Clinical relevance of slow ventricular tachycardia in heart failure patients with primary prophylactic implantable cardioverter defibrillator indication.

AIMS Implantable cardioverter defibrillators (ICDs) have shown to reduce all-cause mortality in heart failure patients. In SCD-HeFT study, ICDs were programmed with a detection zone of ≥ 187 b.p.m. Thus, the incidence and clinical significance of slower ventricular tachycardias (VTs) in these patients remains largely unknown, though clinically important for device selection, programming, and follow-up. METHODS AND RESULTS We prospectively studied symptomatic heart failure patients with an indication for a primary prophylactic ICD with or without concomitant resynchronization therapy according to SCD-HeFT inclusion criteria. Devices were programmed to an additional monitor zone for slow VTs at heart rates 130-186 b.p.m. Two hundred consecutive patients (86% male) were followed for a mean of 509 ± 308 days. One hundred and thirty-seven patients (68.5%) were New York Heart Association class III, 75 patients (37.5%) were on cardiac resynchronization therapy, and 124 (62%) had ischaemic cardiomyopathy. We observed 473 VT episodes in 36 patients (18%) and 131 ventricular fibrillation episodes in 30 patients (15%). Ventricular tachycardia overall occurred in 40 patients (20%). The incidence of slow VTs was low in only 12 patients (6%). No patient with slow VT suffered from syncope, palpitation, or decompensation leading to hospitalization. We did not find any reliable predictor for increased long-term risk of slow VTs. CONCLUSION Incidence of slow VTs in a typical heart failure population with primary prophylactic ICD-implantation ± resynchronization therapy is very low. Slow VTs detected in the ICD monitor zone remained clinically asymptomatic. Thus, single chamber and atriobiventricular ICDs with a VT/ventricular fibrillation zone of ≥ 187 b.p.m. and one burst before shock delivery might be sufficient and pragmatic for the vast majority of these patients.