Cardiac resynchronization therapy and clinical outcomes in patients with advanced left ventricular dysfunction and a wide QRS

Limited data exist on the effects of cardiac resynchronization therapy with defibrillator (CRT-D) on clinical outcomes in patients with advanced left ventricular dysfunction.

This study aimed to evaluate the clinical benefits of CRT-D compared with an implantable cardioverter defibrillator (ICD) in patients with very low left ventricular ejection fraction (LVEF ≤20%) and a wide QRS complex.

This study included 820 patients with LVEF ≤20% and QRS duration ≥130 ms, enrolled in five major trials (MADIT-II, MADIT-CRT, MADIT-RIT, MADIT-RISK, RAID). The primary outcome was a composite of heart failure (HF) or death. Secondary outcomes included death, first HF event, recurrent HF, ventricular tachycardia or fibrillation (VT/VF), and appropriate ICD shocks. Outcomes were stratified by the presence of left bundle branch block (LBBB).

Among 508 CRT-D patients (70% LBBB) and 364 ICD patients (72% LBBB), CRT-D vs. ICD was associated with a significant reduction in the 3-year cumulative event rate of HF or death in LBBB patients (20% vs. 40%, p<0.001 [Figure Panel A]) but not in non-LBBB patients (37% vs. 42%, p=0.499 [Figure Panel B]).

Multivariate analysis showed that CRT-D significantly reduced HF or death in LBBB patients (HR=0.46, p<0.001) but showed no benefit in non-LBBB patients (HR=1.16, p=0.566; p-value for interaction =0.001). Similarly, in LBBB patients, CRT-D was associated with reductions in death (HR=0.60, p=0.069), first HF event (HR=0.42, p<0.001), recurrent HF (HR=0.39, p<0.001), VT/VF (HR=0.64, p=0.011), and appropriate ICD shocks (HR=0.35, p<0.001). In contrast, CRT-D did not significantly reduce any of these outcomes in non-LBBB patients (p>0.1 for all comparisons; p for interaction device-by-LBBB <0.05 for all).

CRT-D provides significant clinical benefits in patients with advanced left ventricular dysfunction and LBBB. These findings should be considered when evaluating the need for advanced HF intervention therapies in this population.