Does Cardiac Resynchronization Therapy Benefit Patients With Right Bundle Branch Block

Abstract

In the United States, ≥5 million have heart failure (HF),1 ≥500 000 are diagnosed each year,2 and 2.5 million are hospitalized for their disease.3 In addition, ≈300 000 patients die from HF every year in the United States,2 and the 5-year survival in the Framingham study in men and women was determined to be 28% and 35%, respectively. These outcomes are known to be modified by QRS duration from the surface ECG. For example, the 3-year mortality rate in patients with HF and QRS duration >160 ms was reported to be 58% in 1 study, which represented nearly a 3-fold increase when compared with patients having a QRS duration under 120 ms.4 The Italian Network on Congestive Heart Failure has reported increased 1-year rates of sudden death and overall mortality in patients with left bundle branch block (LBBB),5 and RBBB has also been found to predict increased mortality in 7073 patients referred for nuclear exercise testing.6 Response by Auricchio et al on p 10 During the past decade, cardiac resynchronization therapy (CRT) implemented as either a pacemaker only or implantable cardioverter defibrillator (ICD; CRT-D) has emerged as an common treatment for patients with HF with left ventricular ejection fraction (LVEF) <35%, severe HF (New York Heart Association [NYHA] class III–IV status), and intraventricular conduction delays, including both LBBB and RBBB. In particular, the Comparison of Medical Therapy, Pacing, and Defibrillation in Heart Failure (COMPANION) trial7 demonstrated improved survival with CRT-D and a borderline improvement in survival for CRT pacemaker device ( P =0.056) in patients with a QRS duration of ≥120 ms. The subgroup analysis from the main article also noted a greater improvement in survival with LBBB versus RBBB. The Cardiac Resynchronization in Heart Failure Study (CARE-HF)8 also enrolled patients with …