The aim of the present study was to evaluate the incidence, predictors, and related outcomes of patients with heart failure (HF) treated with cardiac resynchronization therapy with an implantable cardioverter defibrillator (CRT-D) who experienced electrical storm (ES). Electrical storm was defined as the occurrence of ≥3 episodes in 24 hours of sustained ventricular tachyarrhythmias.

A total of 631 patients with HF (90% male, mean 66 ± 9 years) consecutively received a CRT-D device. At baseline, the mean left ventricular ejection fraction was 26% ± 7%, the QRS duration was 164 ± 33 milliseconds, and the mean New York Heart Association class was 3.3 ± 0.3.

During a mean follow-up of 19 ± 11 months, 2,419 ventricular tachyarrhythmia episodes were appropriately detected in 141 (22%) patients. Electrical storm occurred in 45 (7%) of 631 patients. Kaplan-Meier analysis and multivariable Cox regression showed that ES is more frequent in secondary prevention (hazard ratio 2.3, 95% CI 1.2-4.3, P = .015) and in nonischemic patients (hazard ratio 2.0, 95% CI 1.1-3.8, P = .028). In patients who presented ES, CRT was associated with only marginal nonsignificant improvements of New York Heart Association class and left ventricular ejection fraction. Hospitalizations and death due to HF were more frequent in patients with ES compared with those without ES, amounting to 16.8 (4.3) versus 8.6 (0.9) per 100 patient-years (P = .018) and 7.7 versus 2.7 per 100 patient-years (P = .014), respectively.

Electrical storm affect only 7% of CRT-D recipients and occurred more frequently in nonischemic patients with HF with biventricular implantable cardioverter defibrillators implanted for secondary prevention. Electrical storm was associated with worse HF morbidity and mortality.