Cardiac Resynchronization Therapy and Ventricular Arrhythmias

Cardiac resynchronisation therapy (CRT) using biventricular pacing prolongs survival in patients with heart failure by improving the pump function of the ventricle. But reversal of normal sequence of myocardial activation during epicardial pacing in CRT increases the transmural dispersion of repolarisation (TDR), which is known to predispose to cardiac arrhythmias. Leyva et al has reviewed this aspect in the current issue of Indian Pacing and Electrophysiology Journal [Leyva F et al. Indian Pacing Electrophysiol. J. 2008;8(4):268-280].
The investigators of The InSync ICD (Implantable Cardioverter-Defibrillator) Italian Registry report that [Di Biase L et al. J Am Coll Cardiol 2008:52:1442-1449] in patients treated with CRT defibrillators, there is in fact a reduction in ventricular arrhythmic events during the initial 12 months after implantation. This has been correlated with the degree of reverse remodelling of the left ventricle induced by CRT. Those with reverse remodelling show a pronounced long term improvement and better survival. The recurrence rate of ventricular arrhythmias were siginificantly lesser in the responders than in non – responders to CRT (32% vs. 43%, p = 0.024). In this study of 398 patients, 227 (57%) were defined as responders as they showed 10% or more reduction in end systolic left ventricular volume. The minimum follow up period was 12 months.

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