Cardiac resynchronization therapy and ventricular tachyarrhythmia burden

Background

Cardiac resynchronization therapy–defibrillator (CRT-D) may reduce the incidence of first ventricular tachyarrhythmia (VTA) in patients with heart failure (HF) and left bundle branch block (LBBB).

Objective

The purpose of this study was to assess the effect of CRT-D on VTA burden in LBBB patients.

Methods

We included 1281 patients with LBBB from MADIT-CRT (Multicenter Automatic Defibrillator Implantation Trial–Cardiac Resynchronization Therapy). VTA was defined as any treated or monitored sustained ventricular tachycardia (VT ≥180 bpm) or ventricular fibrillation (VF). Life-threatening VTA was defined as VT ≥200 bpm or VF. VTA recurrence was assessed using the Andersen-Gill model.

Results

During a mean follow-up of 2.5 years, 964 VTA episodes occurred in 264 patients (21%). The VTA rate per 100 person-years was significantly lower in the CRT-D group compared with the implantable cardioverter-defibrillator (ICD) group (20 vs 34; P <.01). Multivariate analysis demonstrated that CRT-D treatment was associated with a 32% risk reduction for VTA recurrence (hazard ratio 0.68; 95% confidence interval 0.57–0.82; P <.001), 57% risk reduction for recurrent life-threatening VTA, 54% risk reduction for recurrent appropriate ICD shocks, and 25% risk reduction for the combined endpoint of VTA and death. The effect of CRT-D on VTA burden was consistent among all tested subgroups but was more pronounced among patients in New York Heart Association functional class I. Landmark analysis showed that at 2 years, the cumulative probability of death subsequent to year one was highest (16%) among patients who had ≥2 VTA events during their first year.

Conclusion

In patients with LBBB and HF, early intervention with CRT-D reduces mortality, VTA burden, and frequency of multiple appropriate ICD shocks. VTA burden is a powerful predictor of subsequent mortality.

Introduction

Cardiac resynchronization therapy–defibrillator (CRT-D) improves heart failure (HF) symptoms and lowers mortality in patients with a low left ventricular ejection fraction (LVEF) and a wide QRS.¹ The benefit of CRT has been proven to be greatest among individuals with complete left bundle branch block (LBBB) morphology on surface electrocardiogram.² Furthermore, CRT may reduce the rate of cardiac disease progression by establishing biventricular electromechanical synchrony during the early stages of HF.³ Our previous data from MADIT-CRT (Multicenter Automatic Defibrillator Implantation Trial–Cardiac Resynchronization Therapy) has suggested that CRT-D also reduces the risk of a first ventricular tachyarrhythmia (VTA) event in patients with HF and LBBB.⁴ However, data regarding the risk factors for repeated VTA events in this patient population or the effect that CRT-D may have on VTA burden are limited. Importantly, VTA burden may be associated with frequent implantable cardioverter-defibrillator (ICD) shocks, decreased quality of life, and subsequent increase in hospitalizations and death.5, 6, 7 Thus, assessment of VTA burden among patients with HF remains of paramount importance.

In the current study, 1281 patients with LBBB who were enrolled in MADIT-CRT were included. We aimed to (1) evaluate the effect of CRT-D on VTA burden (defined as recurrent VTA events) and death; (2) evaluate the consistency of the CRT-D effect on VTA burden in risk subgroups including patients in New York Heart Association (NYHA) functional classes I and II, those with ischemic cardiomyopathy (ICM), and those with nonischemic cardiomyopathy (NICM); (3) identify risk factors for first and recurrent VTA events; and (4) assess the effect of increasing VTA burden on the risk of subsequent adverse events, including death and HF events.