Abstract 4667: Mechanisms of Life Threatening Ventricular Tachyarrhythmias in Patients with Hypertrophic Cardiomyopathy: Implication for Prevention of Sudden Death
Introduction. The occurrence and timing of potentially lethal ventricular tachyarrhythmias and sudden death emanating from the arrhythmogenic myocardial substrate in hypertrophic cardiomyopathy (HCM) has proved to be unpredictable. Access to electrophysiologic data obtained at the time of appropriate interventions from implanted cardioverter-defibrillators (ICDs) in high-risk HCM patients permits an assessment of the arrhythmia triggers for these clinical events.
Methods. Among the patients in the “ICD in HCM” international registry, 31 had intracardiac electrograms suitable for this analysis. Arrhythmias were characterized as ventricular fibrillation (VF) or monomorphic ventricular tachycardia (MMVT), and by the initiating rhythm, cycle length and termination.
Results. Electrograms from 59 appropriate ICD interventions (defibrillator shocks or anti-tachycardia pacing) which terminated ventricular tachycardia/fibrillation (VT/VF) were analyzed in the 31 patients, 38 ± 18 years of age. VF (heart rate 325 ± 63 bpm). accounted for 31 arrhythmia events and MMVT (heart rate: 212 ± 38 bpm) accounted for 28 others, including 19 with rates of 160 –230 bpm. In 29 of the 59 events (49%), bursts of sinus tachycardia (148 ± 31 bpm) immediately preceded VT/VF and the appropriate ICD interventions. In addition, in 4 events (7%), rapid atrial fibrillation (133±21 bpm) preceded VT/VF. In the remaining 26 events (44%), VT/VF appeared to arise spontaneously without a premonitory and triggering arrhythmia.
Conclusions. Sinus tachycardia or rapid atrial fibrillation frequently preceded or initiated potentially lethal ventricular tachyarrhythmias in high-risk HCM patients implanted with ICDs. Sinus tachycardia as an arrhythmia trigger offers a potential mechanism to explain sudden death in HCM patients engaged in exercise, including athletes during competition. The observation that atrial fibrillation may precede appropriate device interventions underscores the possibility that this arrhythmia could constitute a novel risk marker for some HCM patients.