BIV pacing in less severe HF
While the benefits of CRT in moderate to severe HF patients has been well established, it has been more controversial in less severely ill HF patients (NYHA class II or even I). A series of randomized clinical trials (REVERSE26, MADIT-CRT27, Resynchronization/Defibrillation for Ambulatory Heart Failure Trial [RAFT]28) have enrolled nearly 5000 patient with NYHA I-II heart failure.
In MADIT-CRT, patients in NYHA I or II and an LVEF less than or equal 30 % with either LBBB, RBBB or nonspecific intraventricular conduction delay were randomized to either an implantable cardioverter defibrillator (ICD) or CRT with a defibrillator. The hazard ratios for the primary end point (a composite of death from any cause and nonfatal HF-related adverse events) for comparisons of CRT-D patients versus patients who only received an ICD were significantly lower in LBBB patients than in non-LBBB patients. The risk of ventricular tachycardia, ventricular fibrillation, or death was decreased significantly in CRT-D patients with LBBB but not in non-LBBB patients. Echocardiographic parameters showed significantly greater reduction in left ventricular volumes and increase in ejection fraction with CRT-D in LBBB than in non-LBBB patients.
In the REVERSE trial, patients who received CRT pacemakers or defibrillators, with QRS more than or equal 120 ms and LV ejection fraction less than or equal 40% were assigned to active (CRT ON) versus control (CRT OFF) treatment. All patients were in sinus rhythm and receiving optimal medical therapy. The primary study end point was the proportion worsened by the heart failure (HF) clinical composite response. Compared with those of control subjects, clinical outcomes and LV function were improved and LV dimensions were decreased.
The RAFT trial, randomly assigned patients with New York Heart Association (NYHA) class II or III heart failure, a left ventricular ejection fraction of 30% or less, and an intrinsic QRS duration of 120 msec or more or a paced QRS duration of 200 msec or more to receive either an ICD alone or an ICD plus CRT. The primary outcome was death from any cause or hospitalization for heart failure. A significantly less primary outcome occurred in the ICD–CRT group compared with the ICD group.