# Intro to Intra-cardiac Electrograms & the EP Lab https://www.youtube.com/watch?v=-6Z4TB5h7lY Translation: th [00:00] Hi, this is Dr. Joshua Cooper, and we're going to be discussing intercardiac electric rams. สวัสดีครับ นี่คือ ดร. โจชัว คูเปอร์ และเรากำลังจะพูดคุยเกี่ยวกับระบบไฟฟ้าภายในหัวใจ [00:05] It's critically important for all electrophysiologists to understand in detail how unipolar and bipolar signals are recorded and how they should be interpreted in order to maximize the safety and success of EP studies and catheter ablation procedures. เป็นสิ่งสำคัญอย่างยิ่งสำหรับนักสรีรวิทยาไฟฟ้าทุกคนที่จะต้องเข้าใจรายละเอียดเกี่ยวกับวิธีการบันทึกสัญญาณแบบขั้วเดียวและสองขั้ว และวิธีการตีความสัญญาณเหล่านั้น เพื่อเพิ่มความปลอดภัยและความสำเร็จของการศึกษา EP และการทำหัตถการจี้ด้วยสายสวน [00:22] First, I wanted to briefly distinguish between surface electrocardiogram recording and intracardiac electrogram recording. ก่อนอื่น ผมอยากจะแยกความแตกต่างระหว่างการบันทึกคลื่นไฟฟ้าหัวใจบนผิวหนังและการบันทึกคลื่นไฟฟ้าหัวใจภายใน [00:30] When we're recording a surface electrocardiogram, you have two electrodes, the anode and cathode, that are placed on the skin surface, both far away from the heart itself. เมื่อเราบันทึกคลื่นไฟฟ้าหัวใจบนผิวหนัง คุณจะมีอิเล็กโทรดสองตัว คือ แอโนดและแคโทด ที่วางอยู่บนผิวหนัง ซึ่งอยู่ห่างจากหัวใจเอง [00:40] The field view of those electrodes and the distance between them is the entire heart, so that you, in fact, will record the surface P wave, all of the atrial activity, the surface QRS complex, all of the ventricular depolarization, and also even the T wave, the repolarization of มุมมองของอิเล็กโทรดเหล่านั้นและระยะห่างระหว่างกันคือหัวใจทั้งหมด ดังนั้น จริงๆ แล้วคุณจะบันทึกคลื่น P บนผิวหนัง กิจกรรมทั้งหมดของหัวใจห้องบน คลื่น QRS บนผิวหนัง การคลายตัวของหัวใจห้องล่างทั้งหมด และแม้กระทั่งคลื่น T การกลับสู่สภาพเดิมของ [01:02] ventricular tissue however when you place a catheter inside the heart with very closely spaced electrodes so that your anode and cathode are only two or three millimeters apart the fields of view is much much smaller so instead of seeing atrial and ventricular activity in their entirety you're only going to see a little sliver of the local myocardial activation right at the location of where the bipole is positioned. เนื้อเยื่อหัวใจห้องล่าง แต่เมื่อคุณใส่สายสวนเข้าไปในหัวใจด้วยอิเล็กโทรดที่อยู่ใกล้กันมาก จนขั้วบวกและขั้วลบห่างกันเพียงสองหรือสามมิลลิเมตรเท่านั้น ขอบเขตการมองเห็นจะเล็กลงมาก ดังนั้น แทนที่จะเห็นกิจกรรมของหัวใจห้องบนและหัวใจห้องล่างทั้งหมด คุณจะเห็นเพียงส่วนเล็กๆ ของการกระตุ้นกล้ามเนื้อหัวใจเฉพาะที่ ตรงตำแหน่งที่ขั้วสองขั้ววางอยู่ [01:30] this recording is now known as an electrogram and in this case with the catheter in the right ventricle you're not going to see any appreciable atrial activity and you're not even going to see ventricular activity that falls before or after this local recording again called an electrogram. การบันทึกนี้เป็นที่รู้จักในชื่ออิเล็กโทรแกรม และในกรณีนี้ ด้วยสายสวนในหัวใจห้องล่างขวา คุณจะไม่เห็นกิจกรรมของหัวใจห้องบนที่ชัดเจน และคุณจะไม่เห็นกิจกรรมของหัวใจห้องล่างที่เกิดขึ้นก่อนหรือหลังการบันทึกเฉพาะที่นี้ ซึ่งเรียกว่าอิเล็กโทรแกรมอีกครั้ง [01:54] let's start by discussing unipolar recordings in the heart but before we start you might be asking yourself wait a minute we just discussed having an เรามาเริ่มจากการพูดคุยเกี่ยวกับการบันทึกแบบขั้วเดี่ยวในหัวใจกัน แต่ก่อนที่เราจะเริ่ม คุณอาจจะถามตัวเองว่า เดี๋ยวสิ เราเพิ่งพูดถึงการมี [02:04] anode and a cathode in the recording circuit. แอโนดและแคโทดในวงจรบันทึก [02:06] so what do you mean by unipolar recording where there's only one electrode? ดังนั้นคุณหมายถึงอะไรโดยการบันทึกแบบขั้วเดียวซึ่งมีเพียงขั้วไฟฟ้าเดียว [02:10] and here's what we mean when we say unipolar recording in the heart. และนี่คือสิ่งที่เราหมายถึงเมื่อเราพูดถึงการบันทึกแบบขั้วเดียวในหัวใจ [02:17] what we're talking about is actually having only one electrode in the heart itself. สิ่งที่เรากำลังพูดถึงคือการมีขั้วไฟฟ้าเพียงอันเดียวในหัวใจ [02:22] that usually being an anode and the cathode is somewhere remote not located in the heart. โดยปกติจะเป็นแอโนดและแคโทดจะอยู่ที่อื่นห่างไกลออกไป ไม่ได้อยู่ในหัวใจ [02:28] and there are two ways of accomplishing that. และมีสองวิธีในการทำให้สำเร็จ [02:33] one is to take advantage of the surface electrocardiogram electrodes that are already stuck to the patient's skin. วิธีหนึ่งคือการใช้ประโยชน์จากขั้วไฟฟ้าคลื่นไฟฟ้าหัวใจที่พื้นผิวซึ่งติดอยู่กับผิวหนังของผู้ป่วยแล้ว [02:42] if you use the right arm left arm and left leg electrodes they form a triangle. หากคุณใช้ขั้วไฟฟ้าแขนขวา แขนซ้าย และขาซ้าย พวกมันจะก่อตัวเป็นรูปสามเหลี่ยม [02:45] and those vectors actually cancel each other out. และเวกเตอร์เหล่านั้นจะหักล้างกันเอง [02:48] if you electrically couple all three and use them as the recording cathode you're basically going to be recording a unipolar electrogram from the catheter inside the heart. หากคุณเชื่อมต่อทั้งสามเข้าด้วยกันทางไฟฟ้าและใช้เป็นแคโทดบันทึก โดยพื้นฐานแล้วคุณจะบันทึกคลื่นไฟฟ้าหัวใจแบบขั้วเดียวจากสายสวนภายในหัวใจ [03:01] because there is electrical artifact introduced at the level of the adhesive between the. เนื่องจากมีสัญญาณรบกวนทางไฟฟ้าเกิดขึ้นที่ระดับของกาวระหว่าง [03:06] electrode and the skin if you were to add 5,000 to 50,000 ohm resistors into those recording surface electrodes you actually can greatly reduce the amount of that artifact. อิเล็กโทรดและผิวหนัง หากคุณจะเพิ่มตัวต้านทาน 5,000 ถึง 50,000 โอห์มเข้าไปในอิเล็กโทรดพื้นผิวที่บันทึกเหล่านั้น คุณจะสามารถลดปริมาณสิ่งแปลกปลอมนั้นได้อย่างมาก [03:18] This is known as you cut as Wilson Central Terminal. สิ่งนี้เป็นที่รู้จักในชื่อ Wilson Central Terminal [03:24] That means using the surface EKG for creating a unipolar recording. นั่นหมายถึงการใช้ EKG พื้นผิวเพื่อสร้างการบันทึกแบบขั้วเดียว [03:28] The other way that you can achieve a unipolar recording is to place one electrode in the heart like before but have a second electrode in the body itself but remote from the heart. อีกวิธีหนึ่งที่คุณสามารถสร้างการบันทึกแบบขั้วเดียวได้คือการวางอิเล็กโทรดหนึ่งตัวในหัวใจเหมือนก่อนหน้านี้ แต่มีอิเล็กโทรดตัวที่สองในร่างกายเอง แต่ห่างจากหัวใจ [03:42] And this is most often accomplished by having either an independent catheter positioned in the inferior vena cava or an intra cardiac catheter that has an additional electrode mounted somewhere low down in the inferior vena cava that is remote from the heart. และสิ่งนี้มักจะสำเร็จได้โดยการมีสายสวนอิสระที่วางอยู่ในหลอดเลือดดำส่วนล่าง หรือสายสวนภายในหัวใจที่มีอิเล็กโทรดเพิ่มเติมติดตั้งอยู่ด้านล่างในหลอดเลือดดำส่วนล่างที่อยู่ห่างจากหัวใจ [03:58] And that can serve as the recording cathode. และนั่นสามารถทำหน้าที่เป็นแคโทดบันทึกได้ [04:01] And if that is hooked into your recording system again you can record a unipolar. และหากสิ่งนั้นเชื่อมต่อกับระบบบันทึกของคุณอีกครั้ง คุณสามารถบันทึกแบบขั้วเดียวได้ [04:07] recording and that electrode is known as the indifferent electrode. การบันทึกและอิเล็กโทรดนั้นเรียกว่าอิเล็กโทรดที่ไม่แตกต่างกัน [04:16] so here's how we would take a unipolar recording with the anode being shown the red bar representing a sheet of myocardium and the wavefront moving here from left to right past the electrode and beyond. นี่คือวิธีที่เราจะทำการบันทึกแบบขั้วเดี่ยวโดยมีขั้วบวกแสดงเป็นแถบสีแดงแทนแผ่นกล้ามเนื้อหัวใจและคลื่นที่เคลื่อนที่จากซ้ายไปขวาผ่านอิเล็กโทรดและเลยไป [04:31] what's important to recognize in this recording or several things number one when the the wavefront is far away from the electrode at the beginning and at the end of this recording it is outside of the field view and therefore the electrode will record nothing because it can't see it. สิ่งที่สำคัญที่ต้องรับรู้ในการบันทึกนี้มีหลายอย่าง อย่างแรก เมื่อคลื่นอยู่ห่างจากอิเล็กโทรดในตอนเริ่มต้นและตอนท้ายของการบันทึกนี้ มันจะอยู่นอกมุมมอง ดังนั้นอิเล็กโทรดจะไม่บันทึกอะไรเลยเพราะมันมองไม่เห็น [04:49] it is only when the wave front gets close enough to the electrode that it will start to take a recording. มันจะเริ่มบันทึกก็ต่อเมื่อคลื่นเข้ามาใกล้พอที่จะถึงอิเล็กโทรดเท่านั้น [04:55] and when the wave front is moving toward the electrode you're going to see a positive deflection reflecting the movement toward the recording electrode. และเมื่อคลื่นเคลื่อนที่เข้าหาอิเล็กโทรด คุณจะเห็นการเบี่ยงเบนเป็นบวกซึ่งสะท้อนถึงการเคลื่อนที่เข้าหาอิเล็กโทรดบันทึก [05:06] when the wave front passes underneath เมื่อคลื่นเคลื่อนที่ผ่านไปข้างใต้ [05:09] the electrode and starts to move away ขั้วไฟฟ้าและเริ่มเคลื่อนที่ออกไป [05:10] you have a rapid change in the polarity คุณมีการเปลี่ยนแปลงขั้วอย่างรวดเร็ว [05:14] of the electrogram and now it is negative because the wave front is moving away until it is completely out of view in which case there's no longer a recording ของอิเล็กโทรแกรมและตอนนี้มันเป็นลบเพราะหน้าคลื่นกำลังเคลื่อนที่ออกไปจนกระทั่งพ้นสายตาไปโดยสมบูรณ์ซึ่งในกรณีนี้จะไม่มีการบันทึกอีกต่อไป [05:24] if in this same slab of myocardium you position the electrode at the very dead end of the tissue this is what the recording will look like หากในแผ่นกล้ามเนื้อหัวใจเดียวกันนี้คุณวางขั้วไฟฟ้าไว้ที่ปลายสุดของเนื้อเยื่อ นี่คือลักษณะการบันทึกที่จะเป็น [05:36] with the wavefront again moving from left to right you're going to have a much longer period where the wavefront is out of the field view of that one recording electrode เมื่อหน้าคลื่นเคลื่อนที่จากซ้ายไปขวาอีกครั้ง คุณจะมีช่วงเวลาที่ยาวนานขึ้นมากที่หน้าคลื่นอยู่นอกระยะการมองเห็นของขั้วไฟฟ้าบันทึกอันเดียวนั้น [05:47] you're going to have a positive deflection as the wavefront moves toward and unto underneath the electrode but because the wavefront at no point is moving away from the electrode there's no negative deflection seen คุณจะมีการเบี่ยงเบนเป็นบวกเมื่อหน้าคลื่นเคลื่อนที่เข้าหาและอยู่ใต้ขั้วไฟฟ้า แต่เนื่องจากหน้าคลื่นไม่ได้เคลื่อนที่ออกจากขั้วไฟฟ้า ณ จุดใดเลย จึงไม่เห็นการเบี่ยงเบนเป็นลบ [05:59] and conversely if you place the electrode at the very beginning of this strip where the signal starts you're going to see the opposite where at the และในทางกลับกัน หากคุณวางขั้วไฟฟ้าไว้ที่จุดเริ่มต้นของแถบนี้ที่สัญญาณเริ่มต้น คุณจะเห็นสิ่งที่ตรงกันข้ามคือที่ [06:10] Beginning of the recording, you're going to see a negative deflection because the wavefront is moving away from the recording electrode until it gets out of view far enough away and then there will be a flat or absent recording. เมื่อเริ่มบันทึก คุณจะเห็นการเบี่ยงเบนเป็นลบ เนื่องจากคลื่นกำลังเคลื่อนที่ออกจากขั้วไฟฟ้าบันทึก จนกระทั่งพ้นระยะการมองเห็นออกไปไกลพอ จากนั้นจะมีการบันทึกที่ราบเรียบหรือไม่ปรากฏ [06:20] Similarly, if the unipolar electrode is positioned in the middle of the myocardial tissue and the wavefront originates immediately underneath this electrode traveling in more than one direction, you will only see a negative deflection in the unipolar recording because wavefronts are only moving away from the recording electrode and never toward it. ในทำนองเดียวกัน หากขั้วไฟฟ้าขั้วเดียวถูกวางไว้ตรงกลางเนื้อเยื่อกล้ามเนื้อหัวใจ และคลื่นกำเนิดขึ้นทันทีใต้ขั้วไฟฟ้านี้ เคลื่อนที่ไปในทิศทางมากกว่าหนึ่งทิศทาง คุณจะเห็นเพียงการเบี่ยงเบนเป็นลบในการบันทึกขั้วเดียวเท่านั้น เนื่องจากคลื่นกำลังเคลื่อนที่ออกจากขั้วไฟฟ้าบันทึกเท่านั้นและไม่เคยเคลื่อนที่เข้าหา [06:47] You can take advantage of this fact when using a catheter to map the origin of a focal arrhythmia. คุณสามารถใช้ประโยชน์จากข้อเท็จจริงนี้ได้เมื่อใช้สายสวนเพื่อระบุตำแหน่งต้นกำเนิดของการเต้นผิดจังหวะแบบเฉพาะจุด [06:52] When you are at the site of origin, you will only see a negative deflection and no positive deflection in the unipolar electrogram. เมื่อคุณอยู่ที่ตำแหน่งต้นกำเนิด คุณจะเห็นเพียงการเบี่ยงเบนเป็นลบเท่านั้น และไม่มีการเบี่ยงเบนเป็นบวกในกราฟไฟฟ้าขั้วเดียว [06:59] For example, here is a recording taken when a PVC is being mapped in the right ventricular outflow tract. ตัวอย่างเช่น นี่คือการบันทึกที่ถ่ายไว้เมื่อกำลังระบุตำแหน่ง PVC ในทางออกของหัวใจห้องล่างขวา [07:09] You can see in the top six คุณสามารถเห็นในหกอันดับแรก [07:14] recordings here the surface EKGs in those leads and you can see in the distal electrode of the mapping catheter which is also going to serve as the ablation catheter you can see in this site a location there is an initial positive deflection in this unipolar recording that suggests that the wavefront from the origin is moving toward the electrode at some point at the beginning and therefore the electrode cannot possibly be located immediately over that origin and you're not at the right place for ablation. การบันทึกที่นี่คือคลื่นไฟฟ้าหัวใจที่พื้นผิวในลีดเหล่านั้น และคุณสามารถเห็นในอิเล็กโทรดส่วนปลายของสายสวนนำวิถี ซึ่งจะทำหน้าที่เป็นสายสวนจี้ด้วย คุณสามารถเห็นในตำแหน่งนี้ มีการเบี่ยงเบนไปในเชิงบวกในตอนแรกในการบันทึกแบบขั้วเดียวนี้ ซึ่งบ่งชี้ว่าคลื่นจากจุดกำเนิดกำลังเคลื่อนที่เข้าหาอิเล็กโทรด ณ จุดใดจุดหนึ่งในตอนเริ่มต้น ดังนั้นอิเล็กโทรดจึงไม่สามารถอยู่ที่จุดกำเนิดได้ทันที และคุณก็ไม่ได้อยู่ในตำแหน่งที่ถูกต้องสำหรับการจี้ [07:50] if you move the catheter to site B and you see this type of recording where there is absolutely no positive deflection but only a negative deflection that's very encouraging that the wavefront is only moving away from your electrode and suggests the possibility that you may be located right adjacent to or right over the origin the one caveat of course is หากคุณย้ายสายสวนไปยังตำแหน่ง B และคุณเห็นการบันทึกประเภทนี้ ซึ่งไม่มีการเบี่ยงเบนไปในเชิงบวกเลย แต่มีเพียงการเบี่ยงเบนไปในเชิงลบเท่านั้น นั่นเป็นเรื่องน่ายินดีอย่างยิ่งที่คลื่นกำลังเคลื่อนที่ออกจากอิเล็กโทรดของคุณเท่านั้น และบ่งชี้ถึงความเป็นไปได้ที่คุณอาจอยู่ติดกับหรืออยู่เหนือจุดกำเนิด ข้อควรระวังประการหนึ่งแน่นอนคือ [08:15] that if there is an isoelectric initial component to the unipolar recording then it's possible that that down stroke is not the actual start of the electrogram. ว่าหากมีส่วนประกอบเริ่มต้นที่เป็นไอโซอิเล็กทริกของการบันทึกแบบขั้วเดียว ก็เป็นไปได้ว่าการลดลงนั้นไม่ใช่จุดเริ่มต้นที่แท้จริงของอิเล็กโทรแกรม [08:26] and so you have to combine this information with bipolar timing to be a hundred percent sir that your electrode is at the site of origin. และดังนั้นคุณต้องรวมข้อมูลนี้กับการจับเวลาแบบสองขั้วเพื่อให้แน่ใจร้อยเปอร์เซ็นต์ว่าอิเล็กโทรดของคุณอยู่ที่จุดกำเนิด [08:33] but when you see this sharp downward deflection it is very suggestive that you may be on the right track or even at the correct site. แต่เมื่อคุณเห็นการเบี่ยงเบนลงอย่างรวดเร็วนี้ เป็นการบ่งชี้อย่างมากว่าคุณอาจมาถูกทางแล้ว หรือแม้แต่อยู่ในตำแหน่งที่ถูกต้อง [08:46] now we're going to move on from unipolar recordings to bipolar recordings. ตอนนี้เราจะย้ายจากการบันทึกแบบขั้วเดียวไปสู่การบันทึกแบบสองขั้ว [08:54] as a reminder a normal unipolar recording is taken with an anode against myocardial tissue. เพื่อเป็นการเตือนความจำ การบันทึกแบบขั้วเดียวปกติจะทำโดยใช้อะโนดเทียบกับเนื้อเยื่อกล้ามเนื้อหัวใจ [09:00] and as shown in this picture if a wavefront is moving toward the anode a positive deflection is generated in the unipolar recording followed by a rapid down stroke as the wavefront passes the electrode and a negative deflection as the wavefront recedes until it's beyond. และดังที่แสดงในภาพนี้ หากคลื่นเคลื่อนที่เข้าหาอะโนด การเบี่ยงเบนที่เป็นบวกจะถูกสร้างขึ้นในการบันทึกแบบขั้วเดียว ตามด้วยการลดลงอย่างรวดเร็วเมื่อคลื่นผ่านอิเล็กโทรด และการเบี่ยงเบนที่เป็นลบเมื่อคลื่นถอยห่างออกไปจนพ้น [09:18] the fields of view and then no recording is made มุมมองและจากนั้นก็ไม่มีการบันทึก [09:20] what if you took a unipolar recording but used a cathode the opposite polarity from what we were just showing จะเกิดอะไรขึ้นถ้าคุณบันทึกแบบขั้วเดียว แต่ใช้ขั้วลบที่มีขั้วตรงกันข้ามกับที่เราเพิ่งแสดงไป [09:31] and again had a wavefront move from left to right และอีกครั้งที่มีคลื่นเคลื่อนที่จากซ้ายไปขวา [09:33] well basically you're going to see a complete opposite of the recording we showed before โดยพื้นฐานแล้วคุณจะเห็นสิ่งที่ตรงกันข้ามกับการบันทึกที่เราแสดงไปก่อนหน้านี้ [09:44] when the electrum the electrode is recording the signal coming toward it it's going to show a negative deflection instead of positive เมื่ออิเล็กตรัมขั้วไฟฟ้ากำลังบันทึกสัญญาณที่เข้ามาหามัน มันจะแสดงการเบี่ยงเบนเป็นลบแทนที่จะเป็นบวก [09:53] and then there's going to be a rapid transition to a positive deflection as the wave front moves away และการเปลี่ยนผ่านอย่างรวดเร็วไปสู่การเบี่ยงเบนเป็นบวกเมื่อคลื่นเคลื่อนที่ออกไป [09:57] and this opposite polarity is a reflection of the opposite nature of the electrode being used to record และขั้วตรงกันข้ามนี้เป็นการสะท้อนถึงลักษณะที่ตรงกันข้ามของขั้วไฟฟ้าที่ใช้ในการบันทึก [10:03] why is that important ทำไมสิ่งนั้นถึงสำคัญ [10:08] because if you were to record simultaneously an anode and a cathode in unipolar fashion and combine เพราะถ้าคุณจะบันทึกพร้อมกันทั้งแอโนดและแคโทดในลักษณะขั้วเดียวและรวมกัน [10:18] the two that is how we get bipolar recordings so let's do this step-by-step. ทั้งสองนั่นคือวิธีที่เราได้การบันทึกแบบสองขั้ว ดังนั้นเรามาทำทีละขั้นตอนกัน [10:23] if we have these two electrodes positioned near each other but not exactly on top of each other and a wavefront moves from left to right you're going to record both of the things I showed before the anode is going to record a positive deflection and then a negative deflection is the way front approaches passes and then recedes from that electrode and the cathode is going to show the opposite but a little later because it's positioned a little downstream with regard to wavefront propagation. ถ้าเรามีอิเล็กโทรดสองตัวนี้วางอยู่ใกล้กัน แต่ไม่อยู่ตรงกันพอดี และคลื่นเคลื่อนที่จากซ้ายไปขวา คุณจะบันทึกทั้งสองสิ่งที่ฉันแสดงไว้ก่อนหน้านี้ ขั้วบวกจะบันทึกการเบี่ยงเบนที่เป็นบวก จากนั้นการเบี่ยงเบนที่เป็นลบคือคลื่นที่เข้าใกล้ ผ่านไป แล้วถอยห่างจากอิเล็กโทรดนั้น และขั้วลบจะแสดงผลตรงกันข้าม แต่ช้ากว่าเล็กน้อย เพราะมันวางอยู่ต่ำลงไปเล็กน้อยเมื่อเทียบกับการแพร่กระจายของคลื่น [10:56] if you were to take these two recordings and couple them together into one channel you now have a bipolar recording and what's the bipolar recording going to look like it's basically going to be a fusion of the two unipolar recordings superimposed in the one channel and it will look like ถ้าคุณนำการบันทึกทั้งสองนี้มารวมกันเป็นช่องสัญญาณเดียว ตอนนี้คุณมีการบันทึกแบบสองขั้วแล้ว และการบันทึกแบบสองขั้วจะมีลักษณะอย่างไร มันก็คือการรวมกันของการบันทึกแบบขั้วเดียวทั้งสองที่ซ้อนทับกันในช่องสัญญาณเดียว และมันจะมีลักษณะเหมือน [11:19] this in a location where you had only a positive deflection in one electrode and nothing in the other it's going to balance out as a positive deflection at the beginning of the recording and similarly at the end and in the middle you're going to see a fusion of the two where there's overlap and either nullification or amplification depending on the polarities and the timing if you were to take those two electrodes and move them closer together then you're going to get a different appearance of the bipolar recording here is an example of the two electrodes being positioned very close together and this is what the recording will look like as a consequence the amplitude is going to be smaller and the timing is going to be more precise because the electrogram is going to be sharper essentially what is being recorded is the wavefront moving [12:21] in between the two electrodes because they're so close together in terms of timing that most of the overlap here is going to cancel each other out except for the little phase shift in the middle. ระหว่างขั้วไฟฟ้าทั้งสองเพราะว่ามันอยู่ใกล้กันมากในแง่ของเวลาที่การซ้อนทับส่วนใหญ่ที่นี่จะหักล้างกันเอง ยกเว้นการเลื่อนเฟสเล็กน้อยตรงกลาง [12:34] so you get very very precise electrical timing information when you have a closely spaced by pole but the amplitude is going to shrink so there's a balance in terms of how closely spaced electrodes should be in terms of giving you accurate timing information but being able to see the electrogram clearly. ดังนั้นคุณจะได้รับข้อมูลเวลาทางไฟฟ้าที่แม่นยำมากเมื่อคุณมีขั้วไฟฟ้าที่อยู่ใกล้กัน แต่แอมพลิจูดจะลดลง ดังนั้นจึงมีความสมดุลในแง่ของระยะห่างของขั้วไฟฟ้าที่ควรจะเป็นในการให้ข้อมูลเวลาที่แม่นยำ แต่สามารถมองเห็นอิเล็กโทรแกรมได้อย่างชัดเจน [12:53] if you think about this now in different dimensions when you have a bipolar you can have a wavefront that passes in a direction that is parallel to the electrodes in which case you'll get a recording in exactly the way I. หากคุณคิดถึงเรื่องนี้ในมิติที่แตกต่างกัน เมื่อคุณมีขั้วไฟฟ้าสองขั้ว คุณสามารถมีคลื่นที่เคลื่อนที่ไปในทิศทางที่ขนานกับขั้วไฟฟ้า ซึ่งในกรณีนี้คุณจะได้รับการบันทึกในลักษณะเดียวกับที่ฉันทำ [13:12] but what if the wave front moves perpendicularly to the orientation of the by pole you're actually going to get a very flat or almost absent recording. แต่จะเกิดอะไรขึ้นหากคลื่นเคลื่อนที่ตั้งฉากกับทิศทางของขั้วไฟฟ้าสองขั้ว คุณจะได้รับการบันทึกที่แบนราบมากหรือแทบจะไม่มีเลย [13:25] because in this case the two opposite polarity electrodes are going to be recording the signal at exactly the same time because the geometry is the same between the two rather than seeing the wavefront sequentially in which case you're going to get almost complete nullification and overlap of the opposite polarity of the two unipolar recordings in reality when you have a catheter inside the heart usually both electrodes are not exactly lying against the tissue the tip electrode is usually against tissue and the next electrode is usually floating in the blood pool and so you're not usually going to get an exact perpendicular orientation of a wavefront compared to your by pole but you need to take this into account when you're thinking about bipolar recordings. เพราะในกรณีนี้ อิเล็กโทรดขั้วตรงข้ามทั้งสองจะบันทึกสัญญาณในเวลาเดียวกันพอดี เนื่องจากรูปทรงเรขาคณิตเหมือนกันระหว่างทั้งสอง แทนที่จะเห็นคลื่นตามลำดับ ซึ่งในกรณีนั้น คุณจะได้รับการหักล้างและการทับซ้อนของขั้วตรงข้ามของการบันทึกขั้วเดี่ยวทั้งสองเกือบสมบูรณ์ ในความเป็นจริง เมื่อคุณมีสายสวนอยู่ภายในหัวใจ โดยปกติแล้วอิเล็กโทรดทั้งสองจะไม่ได้แนบกับเนื้อเยื่อพอดี อิเล็กโทรดปลายมักจะแนบกับเนื้อเยื่อ และอิเล็กโทรดถัดไปมักจะลอยอยู่ในกระแสเลือด ดังนั้นคุณจึงไม่น่าจะได้รับทิศทางตั้งฉากที่แน่นอนของคลื่นเมื่อเทียบกับขั้วคู่ของคุณ แต่คุณต้องคำนึงถึงสิ่งนี้เมื่อคุณคิดเกี่ยวกับการบันทึกขั้วคู่ [14:18] let's start talking about how to interpret bipolar electric grams with regard to timing and shape it is มาเริ่มพูดคุยกันถึงวิธีการตีความกราฟไฟฟ้าขั้วคู่เกี่ยวกับเวลาและรูปร่างกัน [14:30] First important to recognize that when we are taking intracardiac Elektra grams we are attempting to record very small signals from myocardial tissue but the patient during the study is located in an electrophysiology laboratory where there are all sorts of other electrical signals in the environment and those signals can obscure our ability to see the signals of interest for example there can be high-frequency signals that come from the electrical equipment immediately surrounding the patient creating an artifact or noise that is of high frequency and for this reason we have something called a low-pass filter that can eliminate these high frequency signals and the way to remember this is a low-pass filter will pass the low frequency signals but remove high frequency signals so in this case if we apply a low-pass filter to eliminate the electrical noise shown in ประการแรก สิ่งสำคัญคือต้องตระหนักว่าเมื่อเราทำการตรวจคลื่นไฟฟ้าหัวใจภายในห้องหัวใจ เรากำลังพยายามบันทึกสัญญาณขนาดเล็กมากจากเนื้อเยื่อกล้ามเนื้อหัวใจ แต่ผู้ป่วยระหว่างการศึกษานี้จะอยู่ในห้องปฏิบัติการสรีรวิทยาไฟฟ้าซึ่งมีสัญญาณไฟฟ้าอื่นๆ ทุกประเภทในสภาพแวดล้อม และสัญญาณเหล่านั้นสามารถบดบังความสามารถของเราในการมองเห็นสัญญาณที่น่าสนใจได้ ตัวอย่างเช่น อาจมีสัญญาณความถี่สูงที่มาจากอุปกรณ์ไฟฟ้าที่อยู่รอบตัวผู้ป่วยทันที ทำให้เกิดสิ่งแปลกปลอมหรือสัญญาณรบกวนที่มีความถี่สูง และด้วยเหตุนี้ เราจึงมีสิ่งที่เรียกว่าตัวกรองความถี่ต่ำ (low-pass filter) ที่สามารถกำจัดสัญญาณความถี่สูงเหล่านี้ได้ และวิธีที่จะจำสิ่งนี้คือ ตัวกรองความถี่ต่ำจะยอมให้สัญญาณความถี่ต่ำผ่านไปได้ แต่จะกำจัดสัญญาณความถี่สูง ดังนั้นในกรณีนี้ หากเราใช้ตัวกรองความถี่ต่ำเพื่อกำจัดสัญญาณรบกวนทางไฟฟ้าที่แสดงใน [15:32] the diagram it will clean up the signal แผนภาพจะช่วยลดสัญญาณรบกวน [15:34] and you can see the myocardial potentials more clearly และคุณจะเห็นศักย์ไฟฟ้าของกล้ามเนื้อหัวใจได้ชัดเจนยิ่งขึ้น [15:42] conversely there can be low frequency electrical signals generated around the patient as well ในทางตรงกันข้าม อาจมีสัญญาณไฟฟ้าความถี่ต่ำที่เกิดขึ้นรอบตัวผู้ป่วยได้เช่นกัน [15:45] typically these low frequency signals come from movement of the wires and breathing of the patient โดยทั่วไปสัญญาณความถี่ต่ำเหล่านี้มาจากความเคลื่อนไหวของสายไฟและการหายใจของผู้ป่วย [15:53] that can create an undulation in the baseline ซึ่งสามารถสร้างการแกว่งในเส้นฐานได้ [15:58] this low frequency noise also can obscure the signals of interest สัญญาณรบกวนความถี่ต่ำนี้ยังสามารถบดบังสัญญาณที่น่าสนใจได้ [16:03] and for this purpose we have a high-pass filter which as the name suggests will give a pass or allow through the higher frequency signals และเพื่อวัตถุประสงค์นี้ เรามีฟิลเตอร์ความถี่สูง ซึ่งตามชื่อที่แนะนำ จะยอมให้สัญญาณความถี่สูงผ่านไปได้ [16:14] and it will eliminate the low frequency signals และจะกำจัดสัญญาณความถี่ต่ำ [16:17] and usually in this case for an intracardiac bipolar electrogram that will be set at about 30 Hertz และโดยปกติในกรณีนี้ สำหรับการตรวจคลื่นไฟฟ้าหัวใจสองขั้วภายในหัวใจ จะตั้งค่าไว้ที่ประมาณ 30 เฮิรตซ์ [16:25] and this drifty signal that you see in this diagram can be again cleaned up showing much more clearly the signal และสัญญาณที่ลอยไปมาที่คุณเห็นในแผนภาพนี้สามารถทำความสะอาดได้อีกครั้ง โดยแสดงสัญญาณได้ชัดเจนยิ่งขึ้น [16:33] of interest and eliminating the low frequency noise. ที่น่าสนใจและกำจัดสัญญาณรบกวนความถี่ต่ำ [16:35] when we're thinking about bipolar electro grams we're really thinking about precise timing. เมื่อเรานึกถึงอิเล็กโทรแกรมแบบสองขั้ว เรากำลังนึกถึงการจับเวลาที่แม่นยำ [16:41] as I mentioned in an earlier talk for example if we go back to the PVC analogy here is a recording of a PVC with the top six lines showing surface electrocardiogram tracings in these leads and we are recording from the ablation catheter tip a bipolar electrogram. ดังที่ฉันได้กล่าวไว้ในการพูดคุยก่อนหน้านี้ ตัวอย่างเช่น หากเราย้อนกลับไปที่การเปรียบเทียบ PVC นี่คือการบันทึก PVC โดยหกเส้นด้านบนแสดงการติดตามคลื่นไฟฟ้าหัวใจที่พื้นผิวในลีดเหล่านี้ และเรากำลังบันทึกจากปลายสายสวนการจี้ อิเล็กโทรแกรมแบบสองขั้ว [17:06] and in this case the shape of the signal is not giving the same meaning as the unipolar signal did but the timing information is what we're after. และในกรณีนี้ รูปร่างของสัญญาณไม่ได้ให้ความหมายเหมือนกับสัญญาณขั้วเดียว แต่ข้อมูลการจับเวลาคือสิ่งที่เราต้องการ [17:19] if you look at the first sharp deflection and see how it compares to the start of the surface PVC we can figure out how early we are with our catheter tip compared to the onset of หากคุณดูที่การเบี่ยงเบนที่คมชัดครั้งแรกและดูว่ามันเปรียบเทียบกับการเริ่มต้นของ PVC ที่พื้นผิวอย่างไร เราสามารถหาได้ว่าปลายสายสวนของเราเร็วแค่ไหนเมื่อเทียบกับการเริ่มต้นของ [17:33] The PVC beat in this case at site A. การเต้นของ PVC ในกรณีนี้ที่ตำแหน่ง A [17:37] We're 20 milliseconds in front. เราอยู่ข้างหน้า 20 มิลลิวินาที [17:40] If we move the catheter to another site and show that this bipolar sharp deflection is even earlier at minus 35 milliseconds. หากเราย้ายสายสวนไปยังตำแหน่งอื่นและแสดงให้เห็นว่าการเบี่ยงเบนที่คมชัดแบบสองขั้วนี้เร็วขึ้นอีกที่ลบ 35 มิลลิวินาที [17:48] We can assume correctly that we are closer to the site of origin of the PVC. เราสามารถสันนิษฐานได้อย่างถูกต้องว่าเราอยู่ใกล้กับตำแหน่งต้นกำเนิดของ PVC [17:53] And by going point by point and creating an activation map, a timing map of all these bipolar signals, we can get very precise location and timing information in seeking out the origin for the purposes of ablation of this PVC. และโดยการไปทีละจุดและสร้างแผนที่การกระตุ้น, แผนที่เวลาของสัญญาณสองขั้วทั้งหมดนี้, เราสามารถรับข้อมูลตำแหน่งและเวลาที่แม่นยำมากในการค้นหาต้นกำเนิดเพื่อวัตถุประสงค์ในการจี้ทำลาย PVC นี้ [18:12] But again, if you look at the morphology of the bipolar electrogram, that's not giving us very much information the way the unipolar signals did. แต่ขอย้ำอีกครั้ง, หากคุณดูสัณฐานวิทยาของกราฟไฟฟ้าสองขั้ว, นั่นไม่ได้ให้ข้อมูลแก่เรามากนักเหมือนที่สัญญาณขั้วเดียวให้มา [18:19] These both are just rapid sharp deflections and the polarity positive or negative doesn't really tell us anything about direction of the wavefront. ทั้งสองอย่างนี้เป็นเพียงการเบี่ยงเบนที่รวดเร็วและคมชัด และขั้วบวกหรือลบไม่ได้บอกอะไรเราจริงๆ เกี่ยวกับทิศทางของคลื่นการกระตุ้น [18:31] It's really the timing that's critical with bipolar recordings. จริงๆ แล้วคือเวลาที่สำคัญกับการบันทึกแบบสองขั้ว [18:34] I wanted to show a couple examples though of how bipolar signals may look. ฉันต้องการแสดงตัวอย่างสองสามตัวอย่างเกี่ยวกับลักษณะของสัญญาณสองขั้วที่อาจปรากฏขึ้น [18:43] In different myocardial scenarios in the simplest situation if a wavefront passes across normal myocardium unobstructed and an ablation catheter is placed with a distal bipole adjacent to myocardial tissue you'll generate a relatively simple bipolar electrogram as shown. ในสถานการณ์กล้ามเนื้อหัวใจที่แตกต่างกัน ในสถานการณ์ที่ง่ายที่สุด หากคลื่นเคลื่อนที่ผ่านกล้ามเนื้อหัวใจปกติโดยไม่มีสิ่งกีดขวาง และวางสายสวนการจี้ด้วยขั้วไฟฟ้าสองขั้วปลายใกล้กับเนื้อเยื่อกล้ามเนื้อหัวใจ คุณจะได้กราฟไฟฟ้าสองขั้วที่ค่อนข้างง่ายตามที่แสดง [19:06] However if you have an area of myocardial scar and remember of course that myocardial scar is not simply dead tissue but it is an intermingling of live but sick and slowly conducting myocardial fibers adjacent to true fibrosis and scar that serves as an electrical barrier and now a wavefront approaches this area you're going to get all kinds of wave fronts moving at อย่างไรก็ตาม หากคุณมีบริเวณที่เป็นแผลเป็นของกล้ามเนื้อหัวใจ และโปรดจำไว้ว่าแผลเป็นของกล้ามเนื้อหัวใจไม่ใช่แค่เนื้อเยื่อที่ตายแล้ว แต่เป็นการผสมผสานระหว่างใยกล้ามเนื้อหัวใจที่มีชีวิตแต่ป่วยและนำไฟฟ้าช้าๆ ที่อยู่ติดกับพังผืดและแผลเป็นที่แท้จริงซึ่งทำหน้าที่เป็นสิ่งกีดขวางทางไฟฟ้า และตอนนี้คลื่นกำลังเข้าใกล้บริเวณนี้ คุณจะได้รับคลื่นทุกประเภทที่เคลื่อนที่ [19:36] various times in various directions in a small geographic location. หลายครั้งในทิศทางต่างๆ ในพื้นที่ทางภูมิศาสตร์ขนาดเล็ก [19:40] if a by pole is placed now on this tissue it's going to record in its field of view. หากวางเสาไว้บนเนื้อเยื่อนี้ มันจะบันทึกภาพในมุมมองของมัน [19:48] all these little signals that are happening at different points in time traveling in different directions. สัญญาณเล็กๆ น้อยๆ ทั้งหมดนี้ที่เกิดขึ้นในช่วงเวลาต่างๆ เดินทางในทิศทางต่างๆ [19:57] and it's going to generate a fractionated prolonged signal usually of low amplitude because it's not a large mass of myocardium that's being activated. และมันจะสร้างสัญญาณที่แยกส่วนและยืดเยื้อ โดยทั่วไปมีความผิดปกติเล็กน้อย เพราะมันไม่ใช่กล้ามเนื้อหัวใจห้องล่างขนาดใหญ่ที่กำลังถูกกระตุ้น [20:07] with each of these small little fibers we get excited when we are mapping for example reentrant ventricular tachycardia. ด้วยเส้นใยเล็กๆ เหล่านี้แต่ละเส้น เราจะตื่นเต้นเมื่อเราทำการแมป เช่น ภาวะหัวใจห้องล่างเต้นเร็วจากการกลับเข้าวงจร [20:15] when we see fractionated signals and similarly if we're looking at a diseased atrium with lots of scar. เมื่อเราเห็นสัญญาณที่แยกส่วน และในทำนองเดียวกัน หากเรากำลังมองไปที่หัวใจห้องบนที่ป่วยซึ่งมีแผลเป็นจำนวนมาก [20:23] and the reason we get excited is the same physiology that creates a fractionated signal during sinus rhythm can allow for a reentry circuit to occur within this area of scar. และเหตุผลที่เราตื่นเต้นคือสรีรวิทยาเดียวกันที่สร้างสัญญาณที่แยกส่วนระหว่างจังหวะไซนัส สามารถทำให้เกิดวงจรกลับเข้าสู่บริเวณแผลเป็นนี้ได้ [20:37] fractionated signal suggests the [20:40] possibility that this area may be [20:42] participating in the mechanism of a [20:44] reentrant arrhythmia in the atrium or [20:46] the ventricle if you have normal [20:51] myocardium but there is a single [20:54] electrical barrier such that an oncoming [20:57] wavefront meets it in order to activate [21:00] the myocardium on the opposite side of [21:02] the barrier the wavefront must travel [21:05] along the barrier go around to get to [21:08] the other side if a mapping catheter is [21:12] positioned right on that barrier such [21:15] that its field of view [21:17] includes myocardial tissue on both sides [21:20] then when a bipolar electro gram is [21:23] recorded it's going to see two signals [21:27] it's going to see the first signal as [21:29] the wavefront first approaches the [21:32] barrier on the first side that's shown [21:35] here as the first signal in the [21:36] recording but then as the wavefront [21:39] travels around the barrier and then [21:41] comes back in the field of view on the [21:44] other side of the barrier you're going [21:46] to get a second signal this is known as [21:49] a split potential or a double potential [21:52] and when it is seen it suggests that [21:55] there is a line of electrical block upon [21:59] which the mapping catheter is positioned [22:02] that block could be native from native [22:05] scar or it could be man-made because of [22:08] an ablation line that had been created [22:14] let's delve a little further into the [22:17] shape of bipolar electric rams and [22:19] review the few scenarios where bipolar [22:22] electro gram morphology can actually be [22:25] of clinical use here we have a patient [22:32] who has scar related ventricular [22:34] tachycardia and in this recording there [22:37] is ventricular pacing going on through [22:40] the strip you can see the pacing [22:43] artifact before each QRS complex and the [22:46] complex is marching through at the [22:47] pacing rate if you look at the bipolar [22:51] recording from the ablation catheter tip [22:53] you're going to notice that there are in [22:55] fact two components associated with each [22:58] beat and your first instinct might be to [23:01] think that one is a ventricular signal [23:04] and the other is an atrial signal until [23:07] you look at the coronary sinus catheter [23:10] recording showing slower atrial signals [23:13] marching through the recording this [23:16] suggests that both of the elements of [23:19] the ablation catheter recording are [23:21] ventricular and the reason that there is [23:24] a wide spaced double potential is that [23:27] the catheter is positioned on a line of [23:29] electrical block this could be either [23:32] from native scar or from previous [23:35] catheter ablation generating yet [23:37] regenexx scar either way there is a line [23:41] of electrical block and this fact can be [23:44] useful when trying to figure out the [23:46] ventricular tachycardia circuit and [23:48] designing an ablation strategy another [23:56] way that the morphology of a bipolar [23:59] electrogram can be useful is during [24:02] energy application here is an example of [24:05] an atrial flutter ablation and the [24:08] energy is turned on for an ablation [24:10] lesion and you can see at the start of [24:13] the strip there is a nice [24:16] bipolar electrogram but soon into [24:19] radiofrequency energy application the [24:21] electrogram starts to become more [24:25] rounded more low-frequency and even [24:29] several seconds into the ablation lesion [24:31] it has a very different shape than [24:33] before ablation commenced this is one [24:37] way to assess efficacy of ablation [24:39] lesion formation when the bipolar signal [24:43] starts to disappear and become very far [24:47] field looking which I'll explain in a [24:50] few slides or lower frequency that can [24:54] tell you that there has been successful [24:56] destruction of myocardial tissue and you [24:58] might choose to come off energy [24:59] application sooner than the timer has [25:03] been set another piece of information [25:08] that can be useful during energy [25:10] application is to look at the morphology [25:13] of the electrogram here again is atrial [25:17] flutter being ablative and notice in [25:20] this case that the electrogram which is [25:23] probably overlapping with a previous [25:25] radiofrequency lesion starts as a single [25:28] signal and by the end a few seconds [25:31] later you start to see the beginnings of [25:33] a double potential and as I explained in [25:36] the previous segment when you see a [25:38] double potential that suggests a line of [25:41] block is forming or present this can [25:44] give you a forecast that you are [25:46] successfully generating a line of block [25:49] on the cable tricuspid isthmus during [25:51] flutter ablation and it can serve also [25:54] to guide you if there is a gap in the [25:56] line where further ablation needs to be [25:59] performed the wider the double potential [26:02] along the line the more it suggests [26:04] block is present at that location so [26:07] you'd search for a single bipolar signal [26:10] potential instead of a wide space double [26:12] if you're looking for a gap in the line [26:18] while the bipolar electrogram shape does [26:22] not tell you about the direction of a [26:25] wavefront [26:26] if a bipolar electrogram changes its [26:29] shape it does tell you that there is a [26:32] wavefront coming from a different [26:34] direction even though you may not know [26:36] what that direction is so this is yet [26:39] another case of flutter ablation but [26:42] done during atrial pacing from the [26:44] coronary sinus and in this case there [26:47] was a lot of delay along the isthmus [26:50] line being created but it was unclear at [26:54] which point block actually occurred the [26:58] timing between the signals shown here [27:01] and the signal shown here is rather [27:03] subtle but the morphology is not the [27:07] fact that this electrogram starts as a [27:10] positive and ends as a negative and [27:12] there is a reversal of that pattern in [27:16] this bipolar electro gram tells us that [27:19] the wave front is approaching that [27:21] bypoll from a different direction in [27:23] this case coming from the lateral part [27:26] of the low right atrium rather than [27:28] through the medial part and across the [27:30] leaky line it is on this second beat [27:34] that electrical block was finally [27:36] achieved and other than the bipolar [27:38] timing clue which was subtle the [27:41] morphology change in the bipolar [27:43] electrogram was further confirmation [27:44] that electrical block was finally [27:47] achieved in this complicated flutter [27:49] case another morphology characteristic [27:55] that is important to appreciate and [27:56] bipolar recordings is whether a signal [27:59] is sharp or blunt when a wave front [28:02] passes immediately adjacent to a [28:04] recording by Poul a very high frequency [28:06] sharp signal is generated known as [28:08] near-field whereas if the wavefront is [28:11] passing a little bit further away but [28:13] not totally out of the field of view of [28:15] the bipole then a blunt or a low [28:17] frequency signal is recorded known as [28:19] far field here's an example where that [28:23] distinction was critical this was a PVC [28:26] ablation case and you can see the [28:29] surface EKG leads up top and here is a [28:32] bipolar recording from the distal pulse [28:35] of the mapping [28:36] I'm going to expand the electrogram so [28:39] that we can see it more clearly notice [28:41] that there is a very early signal seen [28:44] the timing of which was very enticing [28:47] but the nature of the signal was that it [28:50] was somewhat blunt suggesting that this [28:53] was far field and not immediately [28:55] adjacent to the mapping catheter by pole [28:57] the second component of the signal was [29:00] very sharp suggesting this was the local [29:02] potential but it wasn't very early as [29:05] the mapping catheter was moved around [29:07] the endocardial surface in this area at [29:10] no point was there able to be a sharp [29:13] electrogram recorded at that early time [29:16] where the blunt signal is currently seen [29:18] that suggested the possibility that this [29:21] signal was coming from deeper in the [29:24] myocardium or even on the epicardial [29:26] surface as a consequence the catheter [29:32] was advanced out the coronary sinus to [29:34] the great cardiac vein location so that [29:37] signals on the epicardial surface of the [29:39] heart could be sampled in recording and [29:43] here is what we found immediately [29:45] opposite the endocardial site shown on [29:47] the left now on the right within the [29:52] venous structures on the outer surface [29:53] of the heart there was a very sharp and [29:56] very early signal that timed exactly [29:59] with this blunt signal that was seen on [30:01] the opposite side of the myocardium this [30:04] suggests a local potential because it is [30:07] sharp or near field and the timing is [30:10] wonderful with regards to potentially [30:12] finding the origin of the pvc notice [30:15] that the second component is a little [30:16] more blunt as this site on the [30:19] epicardium is seeing the endocardial [30:21] signal in a little bit of a far field [30:24] manner by looking at the difference [30:27] between blunt and sharp signals one [30:30] could fine tune the mapping location for [30:33] where the origin origin of this PVC [30:35] might be now it's time to put it all [30:42] together let's review how unipolar and [30:45] bipolar electro Gram information is [30:47] complementary [30:49] and ideally both types of recordings [30:51] should be used at each recording site to [30:54] give you the most information about [30:55] local activation time and what's going [30:58] on in the tissue that surrounds it it's [31:02] important to first consider the nature [31:04] of the catheter that's being used to map [31:06] here is a traditional mapping catheter [31:09] which is also serving as an ablation [31:10] catheter and these typically have four [31:13] electrodes grouped in two by poles and [31:15] we often think only about the distal and [31:18] the proximal bipolar recordings but [31:20] remember of course that there are a [31:22] total of four electrodes and each one of [31:24] these numbered one through four from the [31:26] tip as per convention can provide a [31:29] unipolar recording as well so that from [31:32] the distal pair you can record two [31:34] unipolar signals we talked before about [31:38] how each by pole will give you a near [31:41] field range of sharp electro grams [31:43] telling you about local activation time [31:45] and also that there is an extended field [31:48] of view in its full recording range [31:50] where each by pole will give you far [31:52] field signals telling you a little bit [31:54] of information about what's going on in [31:56] the tissue that surrounds it many people [32:01] will say look if I'm using a bipolar [32:03] recording and that really is an [32:05] integration of the two unipolar [32:06] recordings from that electrode pair why [32:09] do I need to consider the two unipolar [32:11] recordings separately well there [32:14] actually is additional information that [32:15] can be provided and we're going to go [32:17] through some cases that hopefully [32:19] demonstrate that here is case number one [32:25] it's a PVC ablation case and you can see [32:29] first the distal ablation pair of [32:32] electrodes with it's bipolar electro [32:34] gram recording if we were to drop a [32:36] vertical caliper at the sharp initial [32:39] deflection in this electrogram it tells [32:42] you what the local activation time would [32:43] be and at first you might say okay this [32:47] isn't a good spot let me move the [32:48] catheter because I'm not even in front [32:50] of the PVC itself and you might totally [32:53] ignore the fact that there is a small [32:55] little hump that precedes it it's of low [32:57] amplitude and it's round but if you look [33:00] at the unipolar recordings from the [33:02] first and second electrodes that make up [33:04] that distal vipole you'll actually see [33:06] that there are large deflections this is [33:10] of course amplified in terms of its gain [33:13] but you can see that there are [33:15] deflections that are recorded from those [33:16] electrodes that tell you that somewhere [33:18] nearby in that extended field of view [33:21] there is myocardium that is being [33:23] activated a little bit earlier than [33:25] where the local activation signal is [33:26] being inscribed that tells you you're [33:29] close and you may move in one direction [33:31] or another in order to try to get a [33:34] sharp recording that times with that far [33:36] field signal so lesson number one is do [33:39] not ignore far field signals on bipolar [33:41] recordings and you can see how that [33:44] correlates with unipolar signals that [33:46] may show earlier recordings than the [33:48] local activation time on the bipole [33:51] here's another example that's a little [33:54] more subtle but makes the same point if [33:56] you first were to look at the bipolar [33:59] recording in the ablation distal channel [34:02] here and by the way please ignore these [34:05] that reflect atrial activation from a [34:07] retrograde p-wave you'll see that there [34:11] are multiple deflections in this [34:13] ventricular bipolar recording the local [34:15] activation time where the wavefront [34:17] passes between the two electrodes of [34:19] this bipole is actually the very sharp [34:22] steep deflection here and I'm going to [34:25] put a vertical caliper at that site [34:27] which raises the question what is that [34:30] more blunt signal that precedes the [34:32] local activation time and the answer of [34:35] course looking at the unipolar [34:37] recordings showing an earlier activation [34:40] time and looking at the nature of this [34:43] early signal which is blunt and not [34:45] sharp both suggest that this is a far [34:48] field signal if you're looking for the [34:50] wavefront passing that tissue you're [34:52] going to need to move the mapping [34:54] catheter to a location where you have [34:56] that early timing but a much sharper [34:58] signal [35:04] here is another complicated signal to [35:06] interpret if you look at the ablation [35:09] distal recording there are again [35:11] multiple deflections some people who are [35:15] optimistic and really are eager to get [35:17] to the site of origin of this PVC might [35:19] annotate this local activation time [35:21] right at the very first deflection even [35:24] though it is blunt other people might [35:26] say well let me go to where the [35:28] amplitude is greater the very first [35:30] large amplitude deflection whether it's [35:33] sharp or blunt but it's hard to know [35:36] exactly which is the local activation [35:37] time where the wavefront passes between [35:39] the two electrodes of the spy pole if [35:43] you look at the unipolar recordings [35:44] you'll actually see that the sharp [35:46] downstroke signifying wavefront moving [35:48] away from unipolar one and unipolar two [35:51] electrodes is actually a little bit [35:53] later suggesting that in fact this may [35:56] be the local activation time at this [35:58] location and in fact the earlier stuff [36:01] is far field if you were to a blade at [36:04] this site thinking oh it's early you [36:06] actually may be a blading where there is [36:08] actually only a far field signal being [36:10] recorded if you look carefully you'll [36:14] notice that the proximal pair of [36:16] electrodes shows some sharp deflections [36:18] that are earlier and in fact the [36:20] unipolar two on the distal electrode is [36:23] a little bit earlier than unipolar one [36:25] in terms of its down stroke so probably [36:27] this catheter needs to be pulled back in [36:29] order to get the distal pair of [36:31] electrodes over the site of origin and [36:34] get a sharp electrogram at the earliest [36:36] possible time at the distal tip of the [36:38] catheter okay so you might say I don't [36:43] really need unipolar recordings once [36:45] I've learned to distinguish the more [36:47] blunt far-field signals on a bipolar [36:49] recording from the really sharp steep [36:51] near-field signals from the bipolar [36:53] recording and that may be true although [36:55] sometimes it's not so crystal clear and [36:57] the unipolar recordings do help but [36:59] here's an example where it really is [37:01] confusing and the unipolar signals are [37:03] critical to catheter positioning for a [37:06] successful ablation site look here at [37:09] the ablation distal bipolar signal it's [37:11] sharp it's early when you drop a caliper [37:15] it's before the PVC and in fact [37:17] it's the earliest sight you've recorded [37:19] on your activation map if you were to [37:22] ablate here however you would not [37:24] succeed in ablating the PVC and it's [37:26] only the unipolar signals that will show [37:28] you why remember that that distal bypoll [37:32] is made of two unipolar signals that are [37:34] blended so if you see a sharp signal it [37:37] may be recorded on the proximal [37:39] electrode and not the distal look at the [37:42] two unipolar signals I've just displayed [37:44] below the sharper downstroke is actually [37:48] on uni 2 so that unipolar recording is [37:52] more closely associated with the site of [37:54] origin of this PVC rather than the first [37:58] electrode uni 1 where there's actually a [38:01] less sharp descent and a slightly later [38:04] onset of the unipolar recording however [38:07] because there is that sharp signal on [38:09] uni 2 it will show up in the combined [38:11] bipolar signal but if you leave the [38:14] catheter at this location and ablate at [38:17] the distal tip you may be ablating in [38:19] the wrong site and there's a smaller [38:21] chance that you'll be successful at this [38:23] location what you need to do here is to [38:26] pull the catheter back just a little bit [38:28] so that electrode 1 is sitting where [38:31] electrode 2 was and then you can see the [38:35] same early sharp signal on the by pole [38:37] but now a much sharper dissent in the [38:41] uni 1 recording where you're going to be [38:43] a bleeding one additional point that I [38:47] want to make on this slide is that I [38:50] mentioned that manually one would [38:52] typically annotate the local activation [38:55] time for this bipolar signal at this [38:58] first sharp deflection it's important to [39:01] recognize that new software programs are [39:04] taking into account the unipolar [39:07] recordings especially from the distal [39:10] electrode when annotating the local [39:12] activation time on the bipolar signal in [39:16] this fashion if this point were to be [39:20] annotated automatically the line would [39:24] not be placed where I've demonstrated it [39:26] here because the unipolar maximum [39:29] negative [39:30] down slope is later so this bipolar [39:33] electro gram would be annotated later in [39:35] the signal not earlier and in that way [39:39] we can differentiate a sharp early [39:41] deflection that is a consequence of the [39:44] unipolar two part of the electro Graham [39:47] from unipolar one but if one were to [39:50] manually change it to this point then [39:53] you'd actually lose that information so [39:56] again it's important whether it's [39:58] manually done or whether it's through an [39:59] automated program to take into account [40:02] the unipolar signal this is actually the [40:07] holy grail when you're looking for a [40:09] focal sight of origin you want to see a [40:12] sharp bipolar signal that's as early as [40:15] any where you've recorded and you want [40:18] to see very sharp descent on the Uni one [40:23] electrode that is exactly at the same [40:26] time and you do not want to see any far [40:29] field signals on any of the channels [40:31] suggesting that there may be tissue [40:33] being activated earlier this was in fact [40:36] the successful ablation site for this [40:38] PVC and it was confirmed by combining [40:42] the information provided in the bipolar [40:44] and the unipolar recording channels so [40:47] that you can ablate this with the very [40:48] first RF lesion now that we've discussed [40:53] at length how you record and interpret [40:55] unipolar and bipolar electro grams let's [40:57] get into the nuts and bolts of why we [40:59] actually put catheters in the heart and [41:01] how we describe catheter locations so [41:04] that we can synthesize the information [41:05] that's gathered from multiple by poles [41:07] at the same time let's review why we [41:11] bother putting catheters in the heart in [41:13] the first place [41:14] the main reason is so that we can record [41:16] small signals from inside the heart that [41:19] are not seen on the surface EKG for [41:22] example from the bundle of hiss if you [41:24] put a catheter inside the heart right [41:27] next to where the bundle of hiss is [41:28] located at the tricuspid annulus you can [41:31] record a small deflection but because [41:33] the mass of myocardium being depolarized [41:35] is so small it can't possibly generate a [41:38] signal on the surface EKG so it's [41:40] invisible [41:41] similarly during an arrhythmia such as [41:44] ventricular tachycardia you see the [41:47] surface QRS complexes that reflect the [41:50] bulk of the myocardium being depolarized [41:52] but something has to be happening [41:54] between the qrs's if it's a reentrant [41:57] rhythm and it's only when you put a [41:59] catheter inside the heart in an area of [42:01] myocardial scar where there are small [42:03] slips of life but SiC myocardial tissue [42:06] being activated slowly between the QRS [42:09] complexes that we can finally record [42:11] them to see what is their location and [42:14] to direct catheter ablation and during [42:18] any rhythm if you see fractionated [42:20] signals that are very small it can tell [42:22] you that this tissue you're sitting [42:24] against is made of myocardial scar [42:27] interspersed with live but sick and [42:29] slowly conducting myocardial cells that [42:32] can be the substrate for re-entry if [42:35] it's a small amount of mass then you're [42:37] again not going to see these signals on [42:40] the EKG surface it's important sometimes [42:43] for us to record the timing between [42:45] signals for example when we look at the [42:49] surface PR interval that doesn't tell us [42:51] how much of that interval is made up of [42:54] electrical signals traveling through the [42:56] AV node and how much is traveling [42:58] through the his perch in D system but [43:01] when you can record an intracardiac hiss [43:03] bundle potential you can now split up [43:06] that PR interval into two components the [43:08] first part the segment that goes through [43:10] the AV node and the second part the [43:12] signal passing through the his perch in [43:14] D system and that can be important in [43:16] detecting certain disease states [43:18] especially when there is clinical [43:19] evidence of signals not able to get from [43:22] atrium to ventricles and you want to [43:24] know the consequences of that [43:26] second-degree AV block and lastly we [43:31] want to look at the activation sequence [43:33] we can often guess where the origin of a [43:37] signal is coming from and where a [43:38] wavefront is headed by looking at the [43:40] surface EKGs either the P wave or the [43:42] QRS but if you want very detailed [43:45] information about how a wavefront is [43:47] traveling across myocardial tissue we [43:50] put catheters in their heart and record [43:52] from multiple sites so for example [43:55] during sinus rhythm or during pacing we [43:57] can figure out how the atria and the [43:59] ventricles are connected to each other [44:01] is it only through the AV node or is [44:03] there an accessory pathway present and [44:05] if there's an arrhythmia occurring such [44:08] as atrial flutter or a focal atrial [44:10] tachycardia we can really pinpoint with [44:13] high precision by recording bipolar [44:15] electro grams from multiple sites in the [44:18] chambers of interest the exact timing to [44:21] define where the circuit is located or [44:23] where the focal tachycardia is coming [44:26] from if we are to fully appreciate using [44:31] intracardiac catheters the way wave [44:33] fronts move through cardiac tissue you [44:36] need to be recording local potentials at [44:38] multiple positions at once this means [44:41] putting multiple catheters up in the [44:43] heart and each catheter that you place [44:46] usually has multiple pairs of electrodes [44:48] on it the catheters are strategically [44:51] positioned at locations where we want to [44:53] know the timing of activation for a [44:56] moment though in this image let's forget [44:58] that four of these five catheters are [45:00] even present and focused just on one of [45:02] them this catheter is sitting in the [45:05] coronary sinus between the left atrium [45:07] and the left ventricle along the [45:09] posterior aspect of the mitral valve and [45:11] here I've outlined roughly in this elio [45:14] view where the left and right atria [45:16] might sit if you were to record from [45:20] these five pairs of electrodes that I'm [45:22] arbitrarily labeling a through II a [45:25] sitting at the interatrial septum and [45:27] east sitting at the lateral aspect of [45:29] the left atrium and a single beat [45:32] occurred and here are the recordings [45:34] during that beat we can see right away [45:38] instantaneously that because the signal [45:41] was inscribed at position a followed by [45:44] B then C then D then e that this beat [45:48] must have originated rightward from the [45:52] electrode pair labeled a meaning from [45:54] the interatrial septum or from the right [45:57] atrium if there had been a signal that [46:00] originated from the lateral aspect of [46:03] the left atrium and traveled in this [46:05] direction then we would have seen the [46:07] bipolar recording in [46:08] II first if there had been a signal [46:11] originating from the left atrial roof [46:13] that then came down and activated the [46:15] floor of the left atrium you would have [46:17] seen perhaps more simultaneous [46:19] activation of all of these pairs of [46:21] electrodes rather than sequential so you [46:24] can see the power of recording from [46:27] multiple places at once in this case [46:29] only five pairs of electrodes in the [46:31] coronary sinus imagine what you can do [46:33] with more catheters in place and also a [46:37] roving map and catheter recording [46:39] multiple sites beyond where fixed [46:41] catheters are positioned the more [46:46] catheters that are advanced up into the [46:47] heart the more data will be displayed on [46:49] the screen at the same time so it [46:52] becomes very important to label every [46:54] electrogram channel so that you know [46:56] exactly what catheters are in the heart [46:58] where they're located and what [47:00] electrodes are being viewed here are [47:02] some standard labels that are used when [47:04] you see multiple channels on the screen [47:06] at the same time to keep things [47:08] organized HRA stands for high right [47:11] atrium hiss or HB e stands for the HISP [47:15] undal electrogram catheter r-va stands [47:20] for right ventricular apex catheter C S [47:24] stands for coronary sinus were typically [47:27] a Decca polar ten pole catheter or a [47:29] twenty pole catheter is placed ABL [47:32] stands for the ablation catheter duo or [47:37] RA is used usually to represent a twenty [47:40] pole catheter that can be looped around [47:42] the circumference of the right atrium [47:44] typically during flutter procedures halo [47:49] is another type of 20 pole catheter that [47:51] has a slightly different shape that's [47:52] also looped around the right atrium and [47:54] is also used for flutter procedures [47:57] lasso or spiral stands for a much [48:01] smaller circular catheter usually with [48:03] ten or twenty electrodes on it that's [48:05] positioned inside a vein usually a [48:07] pulmonary vein and left atrium during [48:09] afib ablation or sometimes in the [48:11] superior vena cava if that structure is [48:13] being targeted Penta stands for pent [48:17] array which is a five pronged starfish [48:20] like cath [48:21] that has a total of 20 electrodes on it [48:23] as well and is used in various chambers [48:26] when you want to record multiple [48:27] by-polls at the same time there's a [48:33] consistent way that we number the [48:35] electrodes on all catheters and that is [48:38] starting from the end of the catheter [48:39] and working backwards so the distal [48:41] electrode in all catheters is always [48:44] known as electrode number one and then [48:46] working backwards depending on the [48:47] number of electrodes that exist when you [48:50] have a simple catheter like this [48:52] quadrupolar catheter we sometimes talk [48:54] about pairs of electrodes instead of the [48:57] numbers so we may call this pair the [49:00] distal pair of electrodes the mid pair [49:03] of electrodes or the proximal pair of [49:06] electrodes so for example if you have a [49:08] high right atrial catheter you may see a [49:10] label on the screen HRA - D that [49:14] suggests you're talking about the distal [49:16] pair of electrodes or a hiss bundle [49:18] catheter HB e - M that's the middle pair [49:22] of the quadrupolar catheter positioned [49:24] at the hiss when you have many more [49:28] electrodes than four we generally deal [49:30] with numbers again numbering from the [49:32] end of the catheter backwards so in this [49:35] twenty pole catheter you'll see a label [49:38] duo 1 2 or duo 9 10 and that'll tell you [49:43] which pair of electrodes you're dealing [49:44] with in that recording and same thing [49:50] with a circular catheter even though [49:52] it's a circle it still has an end so [49:55] we'll number the electrodes from the [49:57] distal end backwards starting at 1 and [49:59] in this case ending it 20 because it's a [50:02] 20 pole catheter ablation catheters are [50:06] quadrupolar catheters and they're [50:08] typically labeled in two electrode pairs [50:11] so if you see a BL - D that's the distal [50:14] pair of electrodes which includes the [50:16] ablation electrode itself at the [50:18] catheter end when we're dealing with [50:20] unipolar recordings we will number these [50:22] electrodes one through four so it's [50:25] important to know that distinction when [50:27] looking at ablation catheter [50:28] programs so where do we position [50:34] catheters in the heart during a standard [50:36] electrophysiology procedure we take into [50:39] consideration the normal activation of [50:41] the heart [50:42] starting at the sinus node sweeping [50:44] across the right in the left atrium [50:46] going through the AV node and hiss [50:48] Purkinje system and we position [50:51] catheters at places that are accessible [50:54] from the right side of the heart because [50:55] typically we don't like to enter the [50:57] femoral artery if we don't have to we [51:00] don't like to enter the systemic [51:01] circulation if we don't have to but we [51:03] do like to record from strategic [51:05] locations nonetheless so typically we'll [51:08] position a catheter in the high right [51:10] atrium near the sinus node where beats [51:12] start we'll position a catheter at the [51:15] HISP undal electrogram as we discussed [51:17] before so that we can assess atrial [51:20] ventricular conduction we position a [51:22] catheter down in the ventricles in the [51:24] right ventricular apex so that we can [51:26] assess ventricular activation and so [51:29] that we can look at the left side of the [51:31] heart we take advantage of the coronary [51:32] sinus and we positioned typically a 10 [51:35] pole catheter with five pairs of [51:37] electrodes in the coronary sinus to [51:39] record the left atrial activation here [51:45] is an RA o and an L a o view of a [51:48] standard electrophysiology setup where [51:51] you have the high right atrial catheter [51:53] positioned in the high right atrium as [51:55] seen in these two views the right [51:59] ventricular apical catheter extending [52:01] toward the right in the reo view and [52:03] coming straight out at us in the La ov [52:05] you the Hispano catheter positioned [52:08] right at the tricuspid annulus on the [52:10] septum and the coronary sinus catheter [52:14] going into the screen in the reo view [52:16] and traveling leftward in the LA ov you [52:19] and because of the way the heart [52:21] activates during sinus rhythm and what's [52:24] accessible from the femoral vein these [52:26] typically are the places that catheters [52:28] are positioned during a standard EP [52:30] study [52:34] let's keep moving forward now and look [52:37] at how Electra grams from multiple [52:39] channels are displayed on the screen at [52:40] the same time and get into the [52:42] information that they provide first [52:47] let's talk about the speed with which [52:49] signals are displayed on the screen on [52:51] an EKG we call this paper speed [52:53] obviously electronically there's no [52:55] paper involved but let's quickly look at [52:58] displaying information at different [53:01] speeds on the screen we're used to [53:03] seeing on an EKG a 25 millimeter per [53:07] second paper speed and that's what's [53:10] shown here including multiple [53:12] intracardiac channels and the surface [53:14] EKG looks exactly like we would expect [53:17] in the top three channels here the [53:20] problem in the electrophysiology lab is [53:22] that if we display our electrode Ram's [53:24] at this same relatively slow speed then [53:27] you're going to see a lot of electrode [53:29] rims appearing to be simultaneous and [53:32] figuring out what comes before what and [53:35] measuring the timing between intervals [53:37] can get very difficult because [53:38] everything is squished together as a [53:41] consequence we actually display usually [53:45] at 4 or 8 times that speed on the screen [53:50] in the EP lab so it looks something like [53:52] the image on the right which is shown at [53:54] 200 millimeters per second so now the [53:57] surface EKG looks a little funny because [53:59] it stretched out horizontally [54:01] however the electrode Rams are stretched [54:04] out as well which can be very helpful [54:06] when we're talking about measuring [54:08] intervals between one electrogram and [54:11] another or looking at the sequence of [54:14] things which is much clearer now that [54:16] we've stretched things out compared to [54:17] the image on the left [54:24] when multiple channels are displayed at [54:26] the same time on the screen usually [54:28] people will have a specific sequence [54:30] that they'll use so that you can see the [54:32] same pattern over and over again to [54:34] recognize normal versus abnormal [54:37] electrical conduction through the [54:39] cardiac chambers usually at the top the [54:42] surface EKG leads are displayed followed [54:46] by a sequence of electro grams that [54:48] usually rely on the sequence in sinus [54:51] rhythm so that the high right atrial [54:53] catheter is displayed first signals [54:56] travel across the right atrium and reach [54:58] the bundle of his catheter and then they [55:00] travel across the left atrium so the [55:02] coronary sinus electrodes are displayed [55:05] and the beat gets down to the ventricles [55:08] so that the right ventricular apex is [55:10] usually displayed at the bottom [55:11] sometimes people will display the [55:14] coronary sinus catheter with 9/10 at the [55:17] top because then you'll get a sequence [55:19] that is top to bottom in terms of how [55:22] sinus rhythm transmits across the heart [55:24] other people like to use the numeric [55:26] version and put one two at the top in [55:29] which case the signals will have a [55:31] bottom to top sequence in sinus rhythm [55:35] some people like to group different [55:37] electro grams together for example here [55:40] on the right so that your I can track [55:43] patterns in a little different way so [55:45] here the HISP undal recordings are [55:47] grouped together the coronary sinus [55:50] recordings are bundled together and it's [55:52] just individual preference whether or [55:54] not to bunch the Electra grams that are [55:57] from the same catheter together [55:58] separating them out from adjacent [56:00] catheter electrogram tracings when we [56:06] print out snapshots and present them on [56:08] screens like this we usually get a black [56:11] and white version but in the EP lab we [56:14] have additional features at our disposal [56:16] to make things easier to see and sort [56:19] out and that includes coloring the [56:21] Electra grams this is the color system [56:24] that I personally use where I will [56:26] display the high right atrial catheter [56:28] in green the Hispano catheter in yellow [56:32] the coronary sinus in white and the [56:35] right ventricle signal in lavender but [56:38] everybody has their own preference and [56:40] there have been some debates about what [56:42] is the convention and there really is no [56:44] convention it's whatever makes you [56:45] comfortable but using the same pattern [56:48] over and over again makes things much [56:50] easier when you interpret electro grams [56:52] during an EP procedure let's review the [56:57] electro grams that will be recorded by [56:59] the 5 pairs of electrodes in this Decca [57:02] polar catheter that is positioned across [57:04] the tricuspid annulus spanning from the [57:07] right atrium toward the right ventricle [57:09] and passing the bundle of hiss if you [57:12] look at the drawing in the top right I'm [57:14] going to show now where this Decca [57:17] Poehler catheter is sitting and we can [57:20] use that drawing to understand the 5 [57:23] electrogram patterns that are recorded [57:25] from these pairs of electrodes I'm going [57:30] to actually show the surface EKGs so [57:32] that we can better understand the timing [57:34] of the electro grams compared to what's [57:37] going on in the heart as a whole if we [57:41] start here at the 910 pair of electrodes [57:44] we can see that it is sitting in the [57:46] right atrium and it's far enough away [57:48] from the HISP undal and the right [57:50] ventricle so that it's only recording an [57:52] atrial electrogram this times with the [57:56] surface P wave and maybe you can see a [57:59] far field hint of a signal at times with [58:02] the QRS complex but mainly this is [58:04] sitting in the atrium and recording an [58:06] electro gram that's appropriate for that [58:08] location as we move to pair 7/8 this is [58:13] now positioned right at the annulus and [58:15] right near the bundle of hiss so that we [58:17] actually see three different electrogram [58:20] inscriptions on this channel an atrial [58:22] electro gram at times with the P wave a [58:25] ventricular electrogram that times with [58:28] the QRS complex and in between the two [58:31] during the PR segment we see a third [58:33] recording and this represents a direct [58:36] recording of the bundle of hiss as we [58:40] move forward toward pair five six we [58:43] start moving away from atrial tissue [58:45] so we're getting more of a far-field [58:47] small-signal two times with the p-wave a [58:50] larger ventricular signal that's [58:52] actually clipped we actually limit its [58:55] size and that's why it looks squared off [58:57] here at both ends and we're still [59:00] recording a hiss pontal potential [59:02] between the P wave and the QRS complex [59:04] on the surface as we continue to move [59:07] forward we actually see a small signal [59:11] that's a little bit later than where the [59:13] Hispano signal was and this is probably [59:15] a signal from the right bundle branch [59:18] which runs along the inner surface of [59:20] the right ventricular septum and of [59:22] course we still see a ventricular signal [59:25] timing with the QRS lastly as we move [59:28] toward pair one two we see only a [59:31] ventricular electrogram having moved far [59:33] enough away from the conduction system [59:35] and atrial tissue that we no longer see [59:38] electro grams from those structures [59:44] let's now analyze a multi-channel [59:47] recording that's about as simple as we [59:48] can get in the EP lab here we see at the [59:52] top three surface EKG leads labeled on [59:55] the Left we have a catheter in the high [59:58] right atrium giving us an electro gram [01:00:00] here near the sinus node we have a [01:00:03] quadrupole or hiss catheter and we're [01:00:05] displaying two of the three pairs [01:00:07] labeled mid and distal and we can see [01:00:10] the atrial the hiss and the ventricular [01:00:13] signal as we reviewed in the previous [01:00:15] slide and we have a catheter that's all [01:00:18] the way down in the right ventricular [01:00:19] apex showing us a ventricular [01:00:22] electrogram at times with the surface [01:00:24] QRS [01:00:32] why is it important to record a bundle [01:00:35] of hiss we discussed this earlier when [01:00:37] we talked about dividing up the PR [01:00:39] interval into its two components the AV [01:00:42] node part and the hiss Purkinje part a [01:00:45] signals travel from atrium to ventricle [01:00:48] of course it must travel through the AV [01:00:51] node first and then to the his spawn [01:00:53] DeLand then down the bundle branches in [01:00:55] the his Purkinje Tree on the surface [01:00:59] though of course we can only see the P [01:01:01] wave and the QRS and none of those [01:01:03] structures in between so when we record [01:01:07] a bundle of histone here that gives us a [01:01:10] halfway point which actually isn't [01:01:12] halfway because it usually takes longer [01:01:14] to get through the AV node then it takes [01:01:16] to get down the hiss Purkinje system [01:01:18] because those different parts of the [01:01:20] conduction system behave very [01:01:22] differently but now we can measure the [01:01:24] time it takes to get from local atrial [01:01:27] tissue through the AV node to that hiss [01:01:30] pond 'el and this is known as the a h [01:01:32] interval a four atrium and H for hiss [01:01:36] and we can measure how long it takes to [01:01:39] get from the HISP undal down to the [01:01:41] beginning of the qrs known as the hv [01:01:44] interval from the hiss bundle down to [01:01:46] the ventricle and in this way we can [01:01:49] look when patients have a long PR [01:01:51] interval or evidence of AV conduction [01:01:54] block where the problem is located [01:01:57] because if there's a problem with the AV [01:01:58] node versus a problem with the hiss [01:02:00] Purkinje system there are very different [01:02:03] implications in terms of the timing of [01:02:05] progression and the safety of the [01:02:07] patient dictating the necessary [01:02:09] treatment so let's start getting [01:02:14] comfortable with looking at intracardiac [01:02:16] electrogram recordings when there are [01:02:18] multiple catheters in the heart and more [01:02:20] than one beat on the page the simplest [01:02:27] and most straightforward [01:02:28] electrophysiology studies involve three [01:02:31] catheters placed in the heart one at the [01:02:33] high right atrium one at the bundle of [01:02:35] hiss and one in the right ventricle and [01:02:37] let's use this example of second-degree [01:02:40] heart block to show how these recordings [01:02:42] can be useful [01:02:44] here is the surface EKG from a patient [01:02:47] with second-degree heart block showing [01:02:49] five P waves and four QRS complexes P [01:02:52] wave number four does not conduct [01:02:54] successfully through the ventricles and [01:02:56] we can see that the PR interval is [01:02:59] gradually prolonging before the dropped [01:03:02] P wave and shortens back up afterward [01:03:04] this is a classic AV wanky Bach pattern [01:03:07] if we add the intracardiac recordings [01:03:11] from those three catheters I mentioned [01:03:13] this is what we'll see the first thing [01:03:16] that's most important to recognize is [01:03:18] which Electra Graham's a couple with [01:03:22] which beats on the surface EKG and as [01:03:26] you get more experience to learn to do [01:03:28] this automatically but I'm gonna help [01:03:29] you with this particular example by [01:03:32] boxing in each individual beat along [01:03:35] with its intracardiac Electra grams the [01:03:38] first thing to note is that the high [01:03:41] right atrial channel shows a deflection [01:03:43] that times with the P wave in each of [01:03:45] these five instances and then the right [01:03:48] ventricular electrogram times with the [01:03:51] surface QRS and there are four of those [01:03:54] with the fourth beat being absent and [01:03:57] then as we reviewed before the Hispano [01:04:00] electrogram which record signals from [01:04:03] the atrium the ventricle and the bundle [01:04:06] of hiss itself because all of those are [01:04:08] within the field of view of this [01:04:10] particular bipole and I'm going to label [01:04:13] those for you right here notice that as [01:04:18] the PR interval prolongs on the surface [01:04:21] it is the a H interval on the [01:04:23] intracardiac recordings that is [01:04:25] prolonging where the H the interval is [01:04:28] staying constant this tells us that the [01:04:31] point of prolongation is in the AV node [01:04:34] and not in his Purkinje system on top of [01:04:37] that notice that on beat number four [01:04:39] there's actually no hiss puntal [01:04:41] deflection suggesting that this P wave [01:04:44] blocked in the AV node before the signal [01:04:46] even got to the bundle of hiss those [01:04:49] findings combined tell us that AV Weinke [01:04:52] Bach when it is seen is caused by delay [01:04:56] and then block in the AV node in this [01:04:58] case and not in this perk in G system [01:05:02] let's add yet more intercardiac Elektra [01:05:06] grams to the display we can see here [01:05:09] going from top to bottom that we have on [01:05:12] the top three surface EKG leads as [01:05:16] labeled a high right atrial catheter [01:05:20] with a signaled at times with the [01:05:22] surface P wave a hiss bundle catheter [01:05:25] and we're showing the proximal mid and [01:05:27] distal signals as labeled now we have a [01:05:31] coronary sinus catheter in place that [01:05:33] record signals from the left atrium [01:05:36] because that's where the coronary sinus [01:05:37] runs in addition there are some very [01:05:40] small far-field signals from the left [01:05:43] ventricle base and then lastly we have a [01:05:46] right ventricular apex catheter with [01:05:48] that sharp electrogram timing with the [01:05:50] surface QRS notice that the way this is [01:05:54] displayed is consistent with signals [01:05:56] traveling from the sinus node across the [01:05:59] right and then the left atrium giving us [01:06:02] electrogram depolarizations that go from [01:06:05] top to bottom and left to right again as [01:06:09] I mentioned in a previous slide some [01:06:12] people like to order things differently [01:06:14] on the screen but this is my particular [01:06:16] preference so the high right atrial [01:06:18] catheter is activated first in sinus [01:06:20] rhythm the signal sweeps across the [01:06:22] right atrium and is then recorded in the [01:06:24] history which is at the low interatrial [01:06:26] septum and then as the signal sweeps [01:06:29] outward across the left atrium from [01:06:31] right to left we have deflections in the [01:06:35] proximal pair of electrodes CS nine ten [01:06:37] and seven eight and all the way out to [01:06:40] one two then as the signal travels [01:06:43] through the AV node that's reflected in [01:06:45] this a H interval the signal gets [01:06:48] through the AV node reaches the hissed [01:06:49] bundle where you see a hispano [01:06:51] deflection and then gets through the [01:06:53] ventricles creating a surface QRS [01:06:55] deflections on the his catheter which [01:06:57] can see the base of the ventricle in its [01:06:59] field of view and also the right [01:07:01] ventricular apical catheter which is of [01:07:03] course positioned in the ventricle [01:07:05] itself it's important to recognize what [01:07:08] a sinus beat looks like [01:07:09] that when you see other beats you can [01:07:11] compare and contrast them to this [01:07:13] template here are two beats on the [01:07:19] screen and I'll ask you to think for a [01:07:21] moment if you want to hit pause which [01:07:24] beat reflects what type of cardiac event [01:07:27] I'll tell you now at the outset the [01:07:31] second beat on the page is again a sinus [01:07:34] beat and you know that because on the [01:07:36] surface you have a P wave in front of a [01:07:39] relatively narrow QRS remembering the [01:07:41] fast paper speed and you have a sequence [01:07:44] in the atrial signals going from high [01:07:47] right atrium near the sinus node first [01:07:49] traveling across the right atrium and [01:07:51] then traveling across the left atrium [01:07:54] and then the his bundle deflection and [01:07:56] then the ventricular deflections if you [01:07:59] look at the first beat on the page [01:08:00] however you'll notice first on the [01:08:02] surface the QRS is wider suggesting that [01:08:06] this is not traveling down the full [01:08:07] history Kinji tree or using it at all [01:08:10] and the next thing you may notice is [01:08:12] that the atrial events which we know [01:08:15] clearly look like this on beat number [01:08:18] two the sinus beat in this case are [01:08:20] coming later than the ventricular events [01:08:23] notice the first event to happen is in [01:08:26] the right ventricular apex catheter all [01:08:29] of this information combined suggests [01:08:31] that this beat is a premature [01:08:33] ventricular beat of PVC because the [01:08:35] events start in the ventricle not the [01:08:38] atria [01:08:39] so the ventricular electro grabs happen [01:08:42] first and then that beat happens to [01:08:45] conduct retrograde back up to the atrium [01:08:47] through the history Kinji system up [01:08:49] through the AV node and initially to the [01:08:52] interatrial septum near the bundle of [01:08:55] his recording which is why the atrial [01:08:57] signals in the hissed at that are happen [01:09:00] first the signal then simultaneously [01:09:02] travels right-to-left out toward the [01:09:06] left atrium as you can see from the [01:09:08] deflections in the CS catheter but it's [01:09:11] also simultaneously sending a wavefront [01:09:13] across the right atrium back toward the [01:09:16] high right atrial catheter near the [01:09:18] sinus node in the superior vena cava [01:09:20] so these happen more Alessa [01:09:22] but later than the septum is activated [01:09:26] the reason that we know this beat of [01:09:28] course is not a sinus beat that happens [01:09:30] to occur on top of the PVC is because [01:09:33] the high right atrial event happens late [01:09:37] rather than early this is the sequence [01:09:39] we would have seen if this were a [01:09:41] simultaneous sinus beat on top of the [01:09:43] PVC here are three beats on this page [01:09:51] and maybe hit pause and reflect for a [01:09:53] moment if you can identify what is the [01:09:55] nature of these three beats because [01:09:58] there are three and two of them are [01:10:00] close together I'm going to start by [01:10:02] showing you which signals belong to [01:10:05] which beat and the next thing I'll point [01:10:08] you to is that beats one and three look [01:10:11] very familiar in fact those are both [01:10:14] sinus beats and you can tell again [01:10:17] because of the activation sequence in [01:10:19] the intracardiac electrogram channels [01:10:21] with the high right atrium first and so [01:10:24] on as we've discussed twice before the [01:10:26] second beat however shows a narrow QRS [01:10:31] that happens after a p-wave but notice [01:10:35] that the activation sequence in atrial [01:10:37] electro graham's is different now you [01:10:40] might say well this looks like the [01:10:42] previous retrograde conduction after a [01:10:45] PV C that we saw in the previous slide [01:10:47] but this is not a PV C because we have a [01:10:50] skinny QRS just like in sinus rhythm [01:10:52] which follows the atrial events and [01:10:56] follows the hiss bundle recording so [01:10:59] instead this early beat is a premature [01:11:02] atrial beat apiaceae and we can pinpoint [01:11:05] more or less where it's coming from from [01:11:08] the few electrodes that we have in the [01:11:10] heart we can see that the septum the low [01:11:13] septum is activated before the high [01:11:16] right atrium and before the left atrium [01:11:19] so this is a PA C coming at least [01:11:22] closest to the HISP undal catheter so [01:11:26] probably coming from the interatrial [01:11:27] septum or possibly low in the right [01:11:30] atrium much closer to the his catheter [01:11:32] than [01:11:32] the HRA catheter so this is what a PA C [01:11:35] would look like what bits originating [01:11:38] from that location and lastly here are [01:11:42] two beats on this page and by now you're [01:11:45] an expert and you can tell that beat [01:11:46] number two is a sinus feed for all the [01:11:50] reasons we've discussed and you can tell [01:11:52] that beat number one is not a PVC [01:11:55] because the atrial events happen first [01:11:58] and the QRS is skinny just like in sinus [01:12:02] rhythm and it follows the atrial events [01:12:05] and the HISP undal deflection but now [01:12:08] the earliest atrial activation is way [01:12:10] out over here in the left atrium towards [01:12:13] CS three four or CS one two so this is a [01:12:17] premature atrial beat that is happening [01:12:20] and originating from the left atrium [01:12:23] rather than the septum and certainly not [01:12:25] the sinus node because here the high [01:12:28] right atrial catheter is activated at [01:12:30] the very latest so we can tell it's an [01:12:33] atrial event and we can more or less [01:12:35] tell the region of origin from looking [01:12:38] at the electrogram sequence from the [01:12:40] locations that we're recording from [01:12:47] let's go back and actually think a [01:12:49] little bit more in depth about AV [01:12:52] connections I showed you in the last [01:12:57] module this example of AV wanky Bach on [01:13:00] the surface EKG and how it correlated [01:13:02] with prolongation of the a H interval [01:13:05] the time it took to get through the AV [01:13:07] node and how on the P wave that doesn't [01:13:10] conduct [01:13:11] there's no hispano recording because the [01:13:13] signal blocked in the AV node above the [01:13:17] level of the bundle of hiss where that [01:13:18] recording is made let's contrast that [01:13:24] example with this one another patient [01:13:27] with second-degree heart block and you [01:13:30] can see from the surface EKG here there [01:13:32] are two P waves and the second one [01:13:35] conducts down to the ventricles creating [01:13:37] a QRS but the first one does not let's [01:13:41] see what the intracardiac electra [01:13:43] Grahams look like [01:13:47] here we can see that both P waves are of [01:13:50] course associated with atrial [01:13:53] deflections we can see that here and [01:13:55] here those time with the P wave on the [01:13:59] surface and both beats the blocked and [01:14:03] the one that conducts also have a bundle [01:14:05] of hiss recording [01:14:07] seen here and seen here but the first [01:14:11] beat that blocks has no ventricular [01:14:14] electrogram which is not surprising [01:14:16] because there's no surface QRS compared [01:14:20] to the second beat where there is a [01:14:21] ventricular electrogram that times with [01:14:24] the surface QRS so what we can see here [01:14:26] is that the blocked P wave clearly sent [01:14:31] a signal that got through the AV node to [01:14:35] the bundle of His and then it was beyond [01:14:38] the bundle of hiss that the signal [01:14:40] blocked and didn't get down to the [01:14:42] ventricles this is known as sub nodal [01:14:45] block below the level of the AV node and [01:14:48] in this case below where the bundle of [01:14:50] his recording was made and it's [01:14:52] important to distinguish block in the AV [01:14:55] node from block below the AV node [01:14:58] because the former tends to follow a [01:15:00] more gradual course that tends to be a [01:15:03] little more benign in the short term [01:15:05] whereas the latter block below the AV [01:15:07] node can suddenly result in AV block [01:15:11] with asystole or prolonged pauses that [01:15:14] can be even life-threatening if not [01:15:16] simply causing syncope with injury so an [01:15:20] intro cardiac recording can verify what [01:15:23] we might have guessed from the surface [01:15:24] EKG pattern comparing mobitz one AV node [01:15:28] level block versus mobitz to below the [01:15:32] AV node in the history kin G system the [01:15:35] other point I wanted to make on this [01:15:37] slide is to note that on the beat that [01:15:39] conducts the H the interval is actually [01:15:44] quite long and let's review what I mean [01:15:47] by long on the next slide normally the [01:15:52] Hz interval with a normal history kin G [01:15:55] network [01:15:56] is about 40 to 60 milliseconds and in [01:16:00] this case it actually is about a hundred [01:16:03] milliseconds which even though it's only [01:16:05] 40 milliseconds beyond the upper limit [01:16:07] of normal for a hiss Purkinje system [01:16:09] that's really really abnormally slow [01:16:12] suggesting disease in the history kin G [01:16:15] system even if we hadn't seen blog occur [01:16:18] and for comparison here's a normal hv [01:16:21] interval of 40 milliseconds so if we [01:16:24] were to see somebody with very long hv [01:16:27] conduction time we actually would [01:16:30] recommend a pacemaker because a sick [01:16:32] hiss Purkinje system can potentially [01:16:34] suddenly fail leaving a patient with an [01:16:37] absent or an extremely slow heart rate [01:16:39] and an unpredictable timetable what [01:16:44] about a short hv interval like in this [01:16:46] case I've labeled in the histor the a [01:16:50] the H and the V deflections and if we [01:16:54] measure the HISP undal deflection to the [01:16:57] very earliest part of the surface QRS [01:16:59] which starts here I told you normal is [01:17:02] about 40 to 60 milliseconds here were [01:17:05] only five milliseconds and the question [01:17:07] is how is that possible remembering of [01:17:10] course that the HV interval reflects the [01:17:14] time it takes after the signal gets [01:17:16] through the AV node to then get down the [01:17:19] hiss Purkinje system well is it possible [01:17:21] that this patient has SuperDuper fast [01:17:24] conduction down the hiss Purkinje system [01:17:26] so instead of 40 milliseconds it can [01:17:28] race down in five milliseconds and the [01:17:31] answer is no that doesn't happen so the [01:17:35] only way to explain a short hv interval [01:17:39] is that the ventricles must have been [01:17:42] activated in a way other than through [01:17:46] the normal conduction system this can [01:17:49] happen in two predominant fashions one [01:17:52] is there could have been a PV C that [01:17:54] happened to occur smack on top of a [01:17:58] sinus beat but sooner then conduction [01:18:02] would have activated the ventricles or [01:18:04] in this case you could have gotten from [01:18:07] atrium to ventricle through at [01:18:09] different route other than the normal AV [01:18:12] node in his Purkinje network that being [01:18:14] an accessory pathway so there are two [01:18:17] things happening in parallel while ace [01:18:20] wavefront is passing down the AV node [01:18:22] and down the hiss Purkinje system also a [01:18:26] second way front is able to conduct from [01:18:29] right atrium to right ventricle or left [01:18:32] atrium to left ventricle or in the [01:18:34] interatrial septum to the ventricular [01:18:36] septum and that can happen much faster [01:18:39] than the delay that normally results [01:18:41] from going down the AV node and then [01:18:43] down the hiss Purkinje system so when [01:18:45] you see a short hv interval especially [01:18:48] if it's on every single beat you should [01:18:50] be thinking that if there's an accessory [01:18:52] pathway present let's now think about [01:18:56] how the ventricles are electrically [01:18:58] attached to the atrium it's important in [01:19:01] any full EP study to look at retrograde [01:19:04] conduction and not just anterograde [01:19:06] conduction sometimes there's an [01:19:09] accessory pathway that's only capable of [01:19:11] conducting in one direction and usually [01:19:14] that's backwards from ventricles to [01:19:15] atrium and if you only did atrial pacing [01:19:18] you might miss the fact that there's an [01:19:20] accessory pathway present so you have to [01:19:22] do ventricular pacing in order to detect [01:19:24] what's known as a concealed accessory [01:19:27] pathway that only conducts upward this [01:19:30] screen initially may look a little bit [01:19:32] confusing and I'm going to eliminate [01:19:34] some of the electrogram channels for you [01:19:37] because they're not important to the [01:19:39] question that I'm asking right now in [01:19:41] the future as you get more comfortable [01:19:43] looking at electrogram screens you're [01:19:45] automatically going to draw your eye [01:19:48] toward the electro grams of interest and [01:19:50] ignore the ones that aren't important [01:19:52] for the question you're asking at that [01:19:53] moment there's ventricular pacing [01:19:56] occurring in this image reflected on the [01:20:00] surface with little pacing artifacts [01:20:01] before each wide QRS and also there's a [01:20:05] channel at the bottom that shows us that [01:20:06] pacing is occurring if we look at the [01:20:10] atrial activation sequence we can see [01:20:12] the very first atrial electrogram that's [01:20:15] shown is in CS 9:10 and then the [01:20:18] wavefront travels leftward out toward C [01:20:22] s1 [01:20:22] the lateral left atrium but also at the [01:20:25] same time it travels laterally to the [01:20:27] right toward the high right atrial [01:20:30] catheter which is also late we talked in [01:20:33] a previous slide about a PA C that came [01:20:36] from the interatrial septum and traveled [01:20:39] at the same time leftward and rightward [01:20:41] and this is a similar scenario except [01:20:44] now the septum is being activated first [01:20:48] because of retrograde conduction through [01:20:50] the AV node which is located on the [01:20:53] interatrial septum so the two atrial [01:20:56] beats that we see are show activation of [01:20:59] the septum first and then out toward the [01:21:02] left and out toward the right atrium [01:21:04] consistent with conduction over the AV [01:21:06] node in this fashion contrast that with [01:21:12] this image where we're also ventricular [01:21:14] pacing and we see the opposite [01:21:18] activation sequence in the coronary [01:21:20] sinus catheter here the atrial [01:21:23] electrogram and C s12 is first and the [01:21:27] signal then travels left to right across [01:21:29] the left atrium and then getting to the [01:21:32] high right atrial catheter at the very [01:21:34] end [01:21:34] well the AV node as I said is located on [01:21:38] the interatrial septum not out at the [01:21:40] left lateral part of the left atrium so [01:21:44] it's not possible especially considering [01:21:47] the fact that this pattern is seen beat [01:21:48] after beat after beat it's not possible [01:21:51] that this retrograde conduction is [01:21:53] occurring over the AV node because the [01:21:55] AV node is not located out here this [01:21:59] image instantly tells us that we have a [01:22:02] left lateral accessory pathway and that [01:22:06] explains this what's called an eccentric [01:22:08] or an eccentric activation sequence [01:22:10] let's think about it in the elio view of [01:22:13] this fluoroscopy image you can see the [01:22:16] CS catheter labeled and remember of [01:22:18] course that 1/2 is at the tip 9 10 is [01:22:22] here toward the interatrial septum and [01:22:24] if we pace in the right ventricle on the [01:22:27] left we're conducting up the AV node [01:22:29] which is right at the septum and [01:22:31] traveling right [01:22:33] two left across the floor of the left [01:22:35] atrium and the right image where we have [01:22:37] an accessory pathway present the [01:22:40] opposite is happening where we're [01:22:41] reaching the atrial tissue nearest pair [01:22:45] one two in the coronary sinus first and [01:22:47] then travelling back in the opposite [01:22:50] direction I had mentioned earlier that [01:22:56] the more electrode pairs you have in the [01:22:58] heart the more simultaneous information [01:23:00] you can get about activation sequence [01:23:03] having a twenty pol catheter in the [01:23:05] right atrium during atrial flutter is a [01:23:08] great example of the power of having [01:23:11] multiple electrodes simultaneously [01:23:13] recording and let's review such a case [01:23:19] here is a 20 pol catheter that's wrapped [01:23:22] around the right atrium with the tip of [01:23:25] the catheter extending out into the [01:23:28] coronary sinus over here in this case [01:23:32] normally of course we number the [01:23:34] electrodes one through 20 but because of [01:23:36] the subsequent slides numbering [01:23:39] electrode pairs rather than individual [01:23:41] electrodes we're going to talk about [01:23:43] electrode pairs one through ten [01:23:46] numbering from the end backwards and to [01:23:50] give you a sense of where this catheter [01:23:52] is sitting I've shaded roughly where the [01:23:55] left and the right atria are sitting in [01:23:57] this LA o fluoroscopy view here is the [01:24:06] presenting atrial flutter rhythm and [01:24:08] first thing you should look at is the [01:24:11] surface EKG in the inferior leads shown [01:24:15] here in AVF you have the classic [01:24:17] sawtooth pattern consistent with [01:24:20] counterclockwise [01:24:22] right atrial flutter how can we confirm [01:24:25] that using intracardiac recordings we [01:24:28] look at the 10 electrode pairs on this [01:24:31] 20 pole catheter and we look at the [01:24:33] activation sequence [01:24:35] notice that in duo Decca 10 the Electra [01:24:39] grab happens first followed by nine then [01:24:42] eight and seven and six all the way to [01:24:44] one [01:24:45] and this happens over and over again and [01:24:49] this can tell us at a glance that the [01:24:53] wavefront during this tachycardia must [01:24:56] be traveling in this counterclockwise [01:24:58] direction around the right atrium and [01:25:01] then out the coronary sinus and out [01:25:03] toward the left atrium let's think for a [01:25:09] moment about where the right atrial [01:25:11] flutter circuit is located the wavefront [01:25:14] travels down the lateral wall of the [01:25:17] right atrium across the floor up the [01:25:20] interatrial septum back across the right [01:25:23] atrial roof and back down the lateral [01:25:25] part of the right atrium again the left [01:25:29] atrium is activated passively and is not [01:25:31] part of the circuit let me introduce you [01:25:34] to a concept called entrainment pacing [01:25:37] and the basic concept is this you can [01:25:40] pace in the heart from any pair of [01:25:42] electrodes a little faster than the [01:25:44] tachycardia thereby accelerating the [01:25:47] rate and you can come off pacing and you [01:25:50] can then measure the time between the [01:25:52] last paced beat and the first [01:25:54] electrogram in that same channel from [01:25:57] which you were pacing if you're pacing [01:26:00] from within the circuit that measurement [01:26:04] the last paced beat to the first [01:26:05] electrogram of the next beat will be [01:26:07] identical the same as the tachycardia [01:26:11] cycle length if you're pacing away from [01:26:14] the circuit then that interval after [01:26:16] pacing called the post pacing interval [01:26:19] will be longer than the actual [01:26:22] tachycardia cycle length and here is an [01:26:25] example so that we can pinpoint the [01:26:27] location of this right atrial flutter [01:26:29] circuit more precisely if we pace from [01:26:33] electrode pair one duo one shown here [01:26:36] the last paced beat and come off pacing [01:26:40] and measure how long it takes to get to [01:26:42] the first electro gram in that same [01:26:44] channel it's longer than the tachycardia [01:26:47] cycle length telling us that this [01:26:50] location is not in the flutter circuit [01:26:52] and that's important to recognize [01:26:54] because you don't have all atrial [01:26:58] flutter x' [01:26:59] around the right atrium you can have a [01:27:01] left atrial flutter and you can have [01:27:03] flutter circuits that involve scar and [01:27:05] not an entire chamber so this type of [01:27:07] pacing maneuver done at multiple sites [01:27:10] can help pinpoint the exact location and [01:27:13] extent of a flutter circuit if we now [01:27:18] pace from duo v v pair of electrodes [01:27:22] which is now on the lateral floor of the [01:27:25] right atrium and in the circuit we're [01:27:28] going to see that that posts pacing [01:27:30] interval the last paced beat to the [01:27:32] first electrogram on the next beat is [01:27:35] the same as the tachycardia cycle length [01:27:38] telling us that this pair of electrodes [01:27:41] is in the circuit and likewise if we [01:27:48] pace up here at duo 9 we're going to see [01:27:52] the same phenomenon if we pace and stop [01:27:56] pacing we're going to show that that [01:27:58] post pacing interval abbreviated ppi is [01:28:02] the same timing as the tachycardia after [01:28:06] we come off pacing telling us that this [01:28:10] electrode pair is also in the circuit [01:28:12] and lastly and most importantly if we [01:28:18] put an ablation electrode on the floor [01:28:21] of the right atrium in the place where [01:28:23] you would plan to ablate we want that of [01:28:27] course to be in the circuit because we [01:28:28] want to ablate and cut off the circuit [01:28:30] itself and here we see pacing in that [01:28:34] ablation catheter on the Isthmus the [01:28:37] area between the inferior vena cava and [01:28:40] the tricuspid valve and again the post [01:28:44] pacing interval is the same as the [01:28:46] tachycardia telling us that this [01:28:49] location is also in the circuit so in [01:28:51] summary we have found that all places [01:28:54] we've paced around the circumference of [01:28:56] the right atrium are in the flutter [01:28:59] circuit and when we pace from the floor [01:29:03] of the left atrium in the coronary sinus [01:29:05] that is out of the circuit this further [01:29:07] confirms that we're dealing with [01:29:09] counterclockwise [01:29:11] by atrial flutter and we can proceed [01:29:13] with catheter ablation sure enough when [01:29:21] lesions are placed with a radiofrequency [01:29:23] catheter across the floor of the right [01:29:26] atrium in the Isthmus between the [01:29:29] inferior vena cava and the tricuspid [01:29:30] annulus the flutter stops you can see [01:29:35] that occurring right here in the middle [01:29:37] of the screen moreover you can see that [01:29:42] the flutter stops exactly where you had [01:29:44] expected to notice that the last [01:29:48] electrogram to be inscribed is occurring [01:29:51] in duo v but there's no electrogram in [01:29:55] duo 4 which is seen on the [01:29:58] second-to-last beat that's because we're [01:30:00] a blading here right at electrode pair 4 [01:30:03] so that when this flutter circuit is [01:30:06] coming around for the last time and [01:30:08] finally meets block it's able to get to [01:30:10] pair 5 but not beyond that because [01:30:13] that's where the ablation has been [01:30:15] performed so this makes perfect sense [01:30:18] looking at the activation sequence [01:30:20] during tachycardia and at the time of [01:30:22] termination [01:30:23] during radiofrequency ablation if we [01:30:29] pace from the coronary sinus however [01:30:32] after the flutter has terminated we see [01:30:36] this pattern and let's analyze it as we [01:30:41] pace from electrode pair 1 in the [01:30:44] coronary sinus located over here that [01:30:48] wave front is going to move in all [01:30:50] directions including across the floor [01:30:52] toward the right atrium and up the [01:30:54] interatrial septum over the roof and [01:30:57] what's happening in the electro graham's [01:31:00] up top here is a demonstration that the [01:31:04] wavefront is traveling from pair 1 - 2 - [01:31:08] 3 - 4 - 5 - 6 that goes through and past [01:31:13] where we had been making our ablation [01:31:15] lesions suggesting that even though the [01:31:18] flutter terminated signals are still [01:31:20] able to travel across the floor across [01:31:23] the isthmus [01:31:24] and up the lateral wall it's only with [01:31:32] additional ablation lesions that isthmus [01:31:35] block is finally achieved and you can [01:31:38] see that on the third paste beat on the [01:31:42] screen here where the activation [01:31:44] sequence suddenly changed from what had [01:31:46] been seen before what makes this [01:31:49] difference [01:31:51] now there's block at the level of pair [01:31:56] four which is where the ablation lesions [01:31:58] are being created so in order for the [01:32:02] wavefront [01:32:03] to travel to electrode pair five it can [01:32:06] no longer travel across the Isthmus [01:32:08] which is now blocked but instead it has [01:32:11] to travel over the roof and all the way [01:32:14] down and eventually get to electrode [01:32:16] para five that's the only way that that [01:32:18] pair can be activated and that's the [01:32:21] reason for the change in the activation [01:32:24] sequence on the duo Decca catheter look [01:32:27] at what happened to electrode pair five [01:32:29] before it was following electrode four [01:32:32] and before number 6 but when Blanc [01:32:35] occurs now you get to four hit a [01:32:38] roadblock and you have to wait for the [01:32:40] signal to travel over the roof ten nine [01:32:43] eight and all the way down to five on [01:32:44] the lateral side of the line this [01:32:47] confirms that we have block at the cave [01:32:50] of tricuspid isthmus and again [01:32:52] demonstrates how important it is to [01:32:54] record from multiple sites at once when [01:32:57] looking at activation sequence [01:33:03] let's talk a little bit about pacing [01:33:05] maneuvers that can be done in the EP lab [01:33:08] to give us more information about the [01:33:10] heart's electrical system why do we [01:33:16] perform pacing maneuvers during an EP [01:33:18] study there's a whole variety of pieces [01:33:20] of information we can gather by pacing [01:33:23] in the atria and ventricles and here are [01:33:25] some of the most common first we can [01:33:29] assess the health of the sinus node as [01:33:31] I'll show you by pacing in the atria we [01:33:34] can assess AV connections which we've [01:33:36] partially discussed already looking at [01:33:39] the health of the AV node and the hiss [01:33:41] Purkinje system and looking for any [01:33:43] evidence of an accessory pathway that [01:33:45] can conduct in the forward or the [01:33:48] backward direction also we can induce [01:33:52] arrhythmias by pacing in the atria or [01:33:55] the ventricles in different patterns as [01:33:57] we will review and if you're in attack [01:34:02] of kardea there are many different [01:34:04] pacing maneuvers that can be performed [01:34:06] ranging from single beats to overdrive [01:34:09] pacing faster than the tachycardia [01:34:11] itself in order to get more information [01:34:14] about that arrhythmia whether it's it's [01:34:17] mechanism or its location the two main [01:34:25] types of pacing that we do are known as [01:34:28] burst pacing and programmed extra [01:34:31] stimulation and here's what we mean by [01:34:33] those terms burst pacing means that a [01:34:37] number of beats in a row are delivered [01:34:40] in a chamber all at the same rate the [01:34:43] same cycle length that's called a burst [01:34:46] programmed extra stimulation on the [01:34:49] other hand is a very specific pattern [01:34:51] where we usually will deliver eight [01:34:53] beats at one speed and then one or two [01:34:57] or three beats at other faster speeds [01:35:01] the first eight beats [01:35:03] all at the same rate are known as s1 if [01:35:07] you're pacing in the atrium people may [01:35:09] call this a1 if you're pacing in the [01:35:12] ventricle it's v1 and then if you [01:35:14] deliver a [01:35:14] single extra stimulus it'll be known as [01:35:17] s2 or a 2 or the 2 depending on where [01:35:21] the stimulus is delivered and then you [01:35:24] may deliver an s3 and even an s4 the [01:35:28] reason for the 8 beats in a row at the [01:35:31] beginning is cardiac tissue has slightly [01:35:35] different behaviors at different speeds [01:35:37] so to standardize in the EP study [01:35:40] environment we typically pace for 8 [01:35:42] beats in a row usually starting at a [01:35:45] hundred beats per minute 600 [01:35:47] milliseconds so that we can alter the s2 [01:35:50] in the s3 starting with exactly the same [01:35:53] electrical environment here is an [01:35:58] example of a sinus node recovery time [01:36:01] test being done [01:36:02] atrial bursts pacing is performed and [01:36:06] you can see that atrial pacing is [01:36:08] happening because of the pacer spikes [01:36:10] seen in the surface EKG and the artifact [01:36:13] on the high right atrial catheter as [01:36:15] well as the notation at the bottom of [01:36:17] the screen telling us that we're [01:36:19] delivering pacing stimuli this is [01:36:22] performed for usually 30 seconds or more [01:36:25] and then we come off pacing and look how [01:36:28] long it takes for the first sinus beat [01:36:31] to occur this is known as the sinus node [01:36:35] recovery time and there are normal [01:36:38] parameters where we would expect the [01:36:40] sinus node to wake up after being [01:36:42] suppressed from burst pacing for 30 [01:36:45] seconds or more here on the top is an [01:36:48] example of a normal sinus node recovery [01:36:51] time and on the bottom is a very long [01:36:54] and very abnormal sinus node recovery [01:36:57] time the type that might be seen in [01:36:59] somebody who has symptomatic sinus [01:37:02] bradycardia or even light-headed or [01:37:05] fainting spells and then we discover [01:37:07] that it's because the sinus node is not [01:37:09] functioning properly here's an example [01:37:16] of programmed stimulation being used to [01:37:19] look at AV node function there are many [01:37:23] different electro grams on this screen [01:37:25] and I want to focus simply on the one [01:37:28] of relevance which is going to be in the [01:37:31] histor in fact this specific channel at [01:37:34] the distal pole you can see here we've [01:37:38] delivered a seventh and an eighth a 1 [01:37:41] and then a single a 2 at a faster pace [01:37:44] and if we look at this hispano recording [01:37:48] we're going to see four different [01:37:49] deflections number one in with the blue [01:37:53] arrows here we see the pacing artifact [01:37:55] that should not be confused with an [01:37:58] intra cardiac electric ram recording [01:38:00] from cardiac tissue this is generated by [01:38:02] our pacing machine and then we see the [01:38:07] aah and the intervals in that his cello [01:38:10] recording as we reviewed in the past [01:38:13] notice on the surface EKG that the PR [01:38:17] interval during the a1 pacing rate which [01:38:21] is slower is shorter and the PR interval [01:38:24] for that single early a to beat that's [01:38:27] faster is a much longer PR interval we [01:38:32] know that the AV node has properties [01:38:35] called decremental properties meaning [01:38:37] the faster you bombard it with a signal [01:38:40] the slower it conducts and we can prove [01:38:44] that it's the AV node that's the cause [01:38:46] of the PR prolongation by looking at the [01:38:48] intracardiac recordings the a h interval [01:38:52] from the a-1 beats is shorter and on [01:38:56] that single a to beat the a h interval [01:38:59] is much longer and we've already [01:39:00] reviewed that the a h interval [01:39:02] represents the time it takes to get [01:39:05] through the AV node this is completely [01:39:09] normal [01:39:09] AV node behavior and again it's called [01:39:12] decrement the same behavior can be seen [01:39:17] in the backwards direction during [01:39:19] retrograde conduction if we put in [01:39:22] ventricular extra stimuli v1 and v2 [01:39:26] here's the seventh and eighth v1 beats [01:39:29] and the single v2 early PVC paced beat [01:39:33] that we put in [01:39:35] I've colored all the ventricular events [01:39:38] purple I'm gonna leave all the electric [01:39:40] Rams up to start to train you to look at [01:39:42] multiple channels now at the same time [01:39:45] and I'm going to show the atrial electro [01:39:48] Graham's in green so that you can train [01:39:51] your eye and if you want to pause at [01:39:53] this point to take this all in [01:39:55] you'll learn to differentiate what [01:39:57] represents a ventricular signal and what [01:40:00] represents an atrial signal the key [01:40:04] point here when we're doing ventricular [01:40:06] extra stimulation and looking at [01:40:07] retrograde conduction is that it takes [01:40:10] longer to get up to the atria on the v2 [01:40:13] beat and it's the same reason that we [01:40:16] saw a PR prolongation when pacing a1a2 [01:40:20] from the top here we're seeing [01:40:23] retrograde decremental conduction in the [01:40:27] AV node in contrast here were also [01:40:34] performing ventricular programmed [01:40:36] stimulation with a seventh and eighth v1 [01:40:40] beat and an early v2 beat and here are [01:40:43] the retrograde atrial electra Graham's [01:40:46] but notice now there is no evidence of [01:40:49] decrement or prolongation of the VA time [01:40:52] on that early v2 beat [01:40:55] the reason why is here we're not [01:40:57] conducting up the AV node instead we're [01:41:01] conducting up an accessory pathway and [01:41:03] you might say wait a minute I thought [01:41:06] you said earlier that when you conduct [01:41:09] retrograde up an accessory pathway that [01:41:11] the coronary sinus activation is [01:41:13] eccentric earliest out at 1/2 well [01:41:16] that's only true if you have a left [01:41:18] lateral accessory pathway that's far [01:41:21] away from the AV node but what if you [01:41:24] have an accessory pathway on the septum [01:41:27] or connecting the right atrium to the [01:41:29] right ventricle in those cases if you [01:41:32] pace in the ventricle conduct retrograde [01:41:35] over a septal or a right-sided pathway [01:41:37] you're going to activate the left atrium [01:41:41] where the coronary sinus catheter is [01:41:42] sitting from a right-to-left direction [01:41:45] just like with the AV node retrograde [01:41:48] activation so one of the ways we can [01:41:51] distinguish retrograde conduction over [01:41:53] the AV node versus retrograde conduction [01:41:56] over a septal or a right-sided pathway [01:41:59] is to look for decrement which is the [01:42:02] behavior of AV node tissue but usually [01:42:04] is not the behavior of accessory pathway [01:42:07] tissue and here when we pasted earlier [01:42:10] in earlier with the v2 beat we did not [01:42:12] see prolongation of the V a time telling [01:42:15] us that we were not likely conducting [01:42:18] over AV node tissue but instead this was [01:42:21] a concealed accessory pathway let's get [01:42:27] a little more sophisticated with some [01:42:29] pacing maneuvers to finish up this [01:42:31] section on intracardiac electro grams [01:42:37] here's a pretty typical screen of [01:42:40] multiple catheters in the heart with [01:42:42] multiple by pulse being recorded and [01:42:44] displayed at once and again for the less [01:42:47] experienced viewer I'm going to simplify [01:42:50] and eliminate most of these electrogram [01:42:53] channels because they are not necessary [01:42:55] to make the point for this slide let's [01:42:58] focus on the Hispano recording [01:43:01] specifically and I'll label for you the [01:43:04] atrial the hiss bundle and the [01:43:06] ventricular electro grams in those [01:43:08] electrode pairs there are two main [01:43:12] features that you should notice during [01:43:15] this a1 a2 programmed stimulation [01:43:19] maneuver the first is the difference in [01:43:22] the QRS appearance between the first and [01:43:25] the second beats on the page after the [01:43:28] a1 beats the QRS is relatively narrow [01:43:32] but after the a two beat it's extremely [01:43:36] wide the second interesting finding to [01:43:40] note is that there is a hispano [01:43:42] deflection between the atrial and the [01:43:44] ventricular electro grams on the a1 [01:43:47] beats but there is no such history on [01:43:51] the a2 be [01:43:52] so the question is how do we explain [01:43:55] these findings the answer is that there [01:44:00] is an accessory pathway present and if [01:44:05] you look carefully now in retrospect [01:44:07] we'll see there's a little Delta wave [01:44:09] here on the surface EKG on the a1 beat [01:44:13] and this QRS represents a blend between [01:44:18] conduction in the forward direction over [01:44:20] the accessory pathway which explains the [01:44:23] little initial Delta wave deflection and [01:44:26] conduction down the AV node in his [01:44:28] Purkinje system which is responsible for [01:44:31] generating a relatively skinny rest of [01:44:33] the QRS complex however when we deliver [01:44:37] an a to beat that comes in early enough [01:44:41] we are bombarding the AV node and either [01:44:45] the AV node decrements to a large degree [01:44:49] whereas the accessory pathway does not [01:44:51] or we may have even blocked in the AV [01:44:55] node because we have surpassed the [01:44:57] refractory period of the AV node in [01:45:00] either case there's no evidence that we [01:45:03] got through the AV node into the HISP [01:45:06] undal in time to contribute to the QRS [01:45:09] complex which instead is generated [01:45:13] exclusively over the accessory pathway [01:45:15] which doesn't at all mind having been [01:45:18] bombarded by an early a to beat because [01:45:21] the accessory pathway does not have [01:45:24] decremental properties so here we have [01:45:27] demonstrated with a1 a2 programmed [01:45:30] stimulation pacing the behavior of the [01:45:33] AV node versus an accessory pathway [01:45:36] that's conducting in the forward [01:45:38] direction here is an example showing [01:45:45] ventricular programme stimulation with [01:45:48] another subtlety that I wanted to [01:45:49] highlight here are the v1 and v2 beats [01:45:54] and if we look here at retrograde atrial [01:45:58] activation we'll see a different pattern [01:46:01] than anything we've seen before [01:46:04] we've talked about [01:46:05] in eccentric activation versus a [01:46:09] concentric activation of the coronary [01:46:11] sinus meaning earliest at 1/2 versus [01:46:14] earliest at 9:10 but here on the v1 [01:46:17] beats we see a blend of those two a [01:46:20] reverse C shape where there's early [01:46:23] activation both out at CS 1 2 and at CS [01:46:28] 9 10 the reason for this is during [01:46:32] retrograde conduction on those v1 beats [01:46:34] the signal is passing upward both [01:46:38] through an accessory pathway that is [01:46:41] beyond CS 1 2 and also through the AV [01:46:45] node at the interatrial septum so the [01:46:48] Elektra grams that we record in the [01:46:50] coronary sinus catheter are a blend of [01:46:53] those two ways that signals are getting [01:46:57] from ventricles to atrium but what about [01:47:00] on the v 2 beat where we now have an [01:47:02] eccentric only activation well what [01:47:06] happened on that beat is we have [01:47:09] decrement in the AV node in the [01:47:12] retrograde direction or possibly even [01:47:14] block in the AV node in the retrograde [01:47:17] direction so we don't have any early [01:47:20] activation of the septum and cs9 10 but [01:47:23] we exclusively have retrograde [01:47:26] activation via the left lateral [01:47:29] accessory pathway showing early signals [01:47:33] out in CS 1 2 and then traveling in a [01:47:36] left-to-right fashion across the floor [01:47:38] of the left atrium and the coronary [01:47:40] sinus consistent with only conduction [01:47:44] over a left lateral accessory pathway [01:47:46] another way that we can use programmed [01:47:48] extra stimulation to show us how the [01:47:52] ventricles connect to the atria and we [01:47:55] can stress those connections in [01:47:56] particular the AV node by putting in [01:47:59] early extra beats we have previously [01:48:04] discussed that one of the reasons that [01:48:06] we perform programmed stimulation during [01:48:08] an EP study is trying to induce [01:48:11] reentrant arrhythmias [01:48:15] program stimulation can induce a circuit [01:48:18] to perpetuate because of a certain [01:48:20] principle called unidirectional block [01:48:23] when you have a circuit that implies [01:48:25] that you have two routes of getting from [01:48:27] point A to point B in a chamber and if [01:48:30] you put in early extra beats you [01:48:34] hopefully will find a window of time [01:48:36] with the early beat that one of the two [01:48:40] limbs of the circuit is recovered from [01:48:43] the previous beat and the other limb is [01:48:45] not its refractory in which case the [01:48:49] signal you deliver early will travel [01:48:51] down only one of the two routes get to [01:48:54] the far end of the circuit and travel [01:48:56] backwards up the other and if the tissue [01:49:01] recovers by the time that all happens [01:49:03] then you can have the signal travel a [01:49:06] second time round the circuit and on [01:49:09] going again the principle is [01:49:12] unidirectional block and we'll talk [01:49:14] about this in a future module here's an [01:49:17] example of ventricular programme [01:49:19] stimulation inducing reentrant [01:49:22] ventricular tachycardia this is in the [01:49:25] context of a patient who has ventricular [01:49:28] scar with live myocardial fibers [01:49:31] interspersed with scar tissue and there [01:49:34] is a potential circuit that can conduct [01:49:36] round and round if we put in an early [01:49:39] beat at just the right moment to get [01:49:41] unidirectional block and start this [01:49:43] circuit going on this slide we have [01:49:50] exactly the same principle of [01:49:53] unidirectional block and reentry being [01:49:56] provoked by program stimulation but now [01:49:59] we have atrial programmed stimulation [01:50:02] and we have super ventricular [01:50:04] tachycardia as a consequence of a [01:50:07] reentry circuit I'm going to walk you [01:50:09] through this busy slide by coloring all [01:50:12] the atrial electrogram screen and the [01:50:15] ventricular electro grams and surface [01:50:17] QRS complexes purple here are the a1 and [01:50:22] a2 beats and notice that the a1 B [01:50:27] have a pretty normal AV conduction time [01:50:30] and normal aah interval as I'll show in [01:50:33] a moment whereas the a too early beat [01:50:38] takes a really long time to get from [01:50:40] atrium to ventricle the reason here is [01:50:43] that the circuit for this SVT is all [01:50:47] within the AV node and the two limbs of [01:50:51] the circuit are a fast part of the AV [01:50:53] node and a slow part of the AV node that [01:50:57] a to beat blocked in unidirectional [01:51:01] fashion it blocked in the fast pathway [01:51:04] part and conducted taking a long time to [01:51:07] do so over the slow part of the AV node [01:51:10] and then it was able to conduct [01:51:12] backwards up the fast getting reentry [01:51:16] going and initiating SVT again we'll [01:51:20] discuss this principle of reentry in a [01:51:23] future module but I wanted to highlight [01:51:26] the fact that reentry can be produced [01:51:29] with program stimulation in any part of [01:51:33] the heart and that includes for [01:51:35] ventricular tachycardia that's reentrant [01:51:37] for SVT that's reentrant for atrial [01:51:40] flutter which is reentrant it's [01:51:42] important concept at electrophysiology [01:51:45] and arrhythmia understanding