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Intro to Intra-cardiac Electrograms & the EP Lab
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Electrophysiologists and cardiology trainees should watch this video for a foundational understanding of intracardiac signal recording.
TL;DR
This video explains intracardiac electrograms (IEGs), distinguishing them from surface EKGs. It details how unipolar and bipolar IEGs are recorded using electrodes within the heart, focusing on their interpretation for diagnosing arrhythmias and guiding ablation procedures.
Key Takeaways
- Intracardiac electrograms provide localized myocardial activation signals, unlike surface ECGs which capture the entire heart's electrical activity.
- Unipolar recordings use one electrode in the heart and a remote reference, capturing local electrical events as the wavefront approaches or recedes.
- A unipolar recording with only a negative deflection suggests the electrode is at the origin of an arrhythmia, as wavefronts only move away.
- Positive deflection in a unipolar recording indicates the wavefront is moving towards the electrode, meaning it's not at the precise origin of an arrhythmia.
- Bipolar recordings are created by combining unipolar signals from two closely spaced electrodes, offering a different perspective on local electrical activity.
- Surface ECG electrodes can be adapted for unipolar recordings using the Wilson Central Terminal or an indifferent electrode in the IVC.
- Interpreting both unipolar and bipolar electrograms is crucial for accurate diagnosis and successful catheter ablation procedures in electrophysiology.
In This Video
- 00:00Introduction to Intracardiac Electrograms
Dr. Cooper introduces intracardiac electrograms, emphasizing their importance for EP studies and ablation procedures.
- 00:22Surface vs. Intracardiac Recordings
Surface ECG electrodes are far from the heart, recording the entire heart's activity. Intracardiac electrodes are close, recording local activation.
- 01:54Understanding Unipolar Recordings
Unipolar recordings use one electrode in the heart (anode) with a remote cathode, like Wilson's Central Terminal or an indifferent electrode.
- 04:16Unipolar Wavefront Interpretation
Unipolar recordings show positive deflection when wavefront moves toward the electrode and negative when moving away.
- 06:47Mapping Arrhythmia Origins
Unipolar recordings help map arrhythmia origins; a negative deflection suggests proximity to the origin site.
- 08:46Introduction to Bipolar Recordings
Bipolar recordings combine unipolar anode and cathode signals, capturing local electrical activity between two closely spaced electrodes.
Questions & Answers
What is the difference between surface ECG and intracardiac electrograms?
Surface ECG uses distant electrodes to view the entire heart's electrical activity, while intracardiac electrograms use closely spaced electrodes within the heart to record local myocardial activation.
How is a unipolar electrogram recorded?
A unipolar electrogram uses one electrode within the heart as the anode and a remote electrode (on the skin or in the body) as the cathode.
What is the Wilson Central Terminal used for?
The Wilson Central Terminal uses surface ECG electrodes to create a reference point, allowing for unipolar electrogram recordings from a catheter inside the heart.
What does a positive deflection in a unipolar electrogram indicate?
A positive deflection in a unipolar electrogram indicates that the electrical wavefront is moving toward the recording electrode.
How are bipolar electrograms recorded?
Bipolar electrograms are recorded by using two closely spaced electrodes on a catheter, where one acts as the anode and the other as the cathode, recording the potential difference between them.
What is the significance of a purely negative deflection in a unipolar electrogram during arrhythmia mapping?
A purely negative deflection suggests the electrode is located at or very near the origin of the arrhythmia, as the wavefront is only moving away from the electrode.
Key Terms
- Intracardiac electrogram — An electrical recording made from electrodes placed inside the heart.
- Unipolar recording — An electrogram recorded using a single active electrode within the heart and a remote reference electrode.
- Bipolar recording — An electrogram recorded using two closely spaced electrodes on a catheter, measuring the potential difference between them.
- Wilson Central Terminal — A method using surface ECG electrodes to create a reference potential for unipolar intracardiac recordings.
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