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Transmural conduction time in an early repolarization syndrome model.
Namsik Yoon1, Hyung Ki Jeong1, Ki Hong Lee1
1Department of Cardiovascular Medicine, Heart Center of Chonnam National University Hospital, Chonnam National University Medical School, Chonnam National University, Dong-gu, Gwangju 61469, Republic of Korea.
Experimental and Therapeutic Medicine
|August 29, 2020
Summary
This study found that polymorphic ventricular tachycardia can occur in early repolarization syndrome without significant delays in ventricular depolarization. Therefore, altered conduction velocity may not be the primary cause of these dangerous arrhythmias.
Area of Science:
- Cardiovascular Physiology
- Electrophysiology
- Cardiac Arrhythmia Research
Background:
- J wave syndrome, a cause of sudden cardiac death, is often linked to delayed ventricular depolarization.
- The prevailing theory suggests heterogeneity in myocardial conduction velocity underlies ventricular arrhythmias in this condition.
- This study investigates whether conduction delays are essential for inducing polymorphic ventricular tachycardia in an early repolarization model.
Purpose of the Study:
- To evaluate transmural conduction time and its heterogeneity in a canine model of early repolarization syndrome.
- To determine if polymorphic ventricular tachycardia can be induced without significant regional conduction velocity differences.
- To challenge the delayed depolarization theory in the context of early repolarization-induced arrhythmias.
Main Methods:
- Utilized coronary-perfused canine left ventricular wedge preparations (n=18).
- Recorded pseudo-electrocardiograms and endocardial/epicardial action potentials.
- Administered Ito agonist NS5806, verapamil, and acetylcholine to mimic early repolarization genotypes and measured transmural conduction times.
Main Results:
- Polymorphic ventricular tachycardia was induced in 14 out of 18 preparations.
- No definite delayed phase 0 upstroke was observed in action potentials during induced arrhythmias.
- While transmural conduction time increased slightly (2.6±0.4 msec) with agents, heterogeneity did not significantly increase (P=0.240).
Conclusions:
- Early repolarization syndrome can trigger polymorphic ventricular tachycardia without significant regional conduction velocity heterogeneity.
- These findings suggest that delayed depolarization is not a prerequisite for generating ventricular arrhythmias in this experimental model.
- Local depolarization heterogeneity is likely not a major factor in the genesis of ventricular arrhythmias in early repolarization syndrome.
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