[Initiation modes of spontaneous monomorphic ventricular tachycardia in patients with Chagas heart disease].

INTRODUCTION AND OBJECTIVES We sought to demonstrate the mode of spontaneous onset of sustained monomorphic ventricular tachycardia in patients with Chagas' cardiomyopathy. METHODS We studied 222 stored electrograms in 14 patients with Chagas cardiomyopathy and spontaneous monomorphic ventricular tachycardia treated with a cardioverter defibrillator. Premature ventricular complexes before ventricular tachycardia were classified by morphology and number. The onset was considered "sudden" if no previous premature ventricular complexes were present, and "extrasystolic" if a ventricular extrasystole precedeed SMVT initiation. Prematurity was evaluated by the coupling interval and a calculated prematurity ratio (RR'/RR). RESULTS Two-hundred and nine episodes (94%) were initiated by late-coupled premature ventricular complexes (prematurity ratio >0.5). The mean coupling interval of the initiating beat was 565+/-117 ms with a mean prematurity ratio of 0.72+/-0.15. A sudden onset was the most frequent pattern of ventricular tachycardia initiation (129 episodes, 58%). Among the extrasystolic onset (93 episodes, 42%), 48 were due to multiple premature ventricular complexes and 88 had a different QRS complex (electrogram) morphology of the ventricular extrasystoles than that recorded during the subsequent ventricular tachycardia. The arrhythmia was preceded by a short-long-short sequence in 95/222 episodes (43%). CONCLUSIONS In implantable cardioverter defibrillator recipients with Chagas cardiomyopathy, spontaneous monomorphic ventricular tachycardia episodes are typically initiated by late-coupled premature ventricular complexes, which often show a short-long-short sequence.