Cardiac pacing in patients with heart failure and right bundle branch block

Abstract

Patients with bundle branch block by ECG whether right bundle branch block (RBBB) or left bundle branch block (LBBB) have an increased risk of cardiovascularmorbidity and mortality. Both types of conduction abnormalities are associated with structural heart disease and are often seen together with heart failure [1]. Cardiac resynchronization therapy (CRT) has been a tremendous breakthrough for patients with LBBB and symptomatic heart failure leading to increased life quality, reduced symptoms, LV remodeling and reduced morbidity and mortality [2]. In contrast, studies indicate that non-LBBB patients (RBBB or IVCD) do not benefit from CRT and that it may even be harmful in some patients [3]. While LBBB pathophysiology and the mechanisms behind treatment of LBBB-induced heart failure have begun to unravel throughout recent years [4,5], a large evidence gap exists regarding the electrical and mechanical effects of pacing in patients with heart failure and RBBB. Indeed, it is unclear whether CRT is applied correctly and even whether it should be applied at all. In the current issue of JECG Crea and coworkers report a case of right ventricular septal pacing as an alternate treatment for heart failure and RBBB. It may be that other pacing modes should be considered to improve device therapy in RBBB patients. The experience with pacing in heart failure patients and RBBB is sparse. Between 5% and 15% of the patients in the landmark clinical trials have been patients with RBBB. Most of the data available on RBBB and CRT is derived from retrospective analysis and from a relatively small number of patients from post hoc analysis of the randomized CRT trial. A large retrospective analysis by Bilchick et al. on 14,946 Medicare patients (2005–2006) showed that RBBB was a powerful predictor of death (1-year HR, 1.44; 3-year HR, 1.37; P b 0.001) [6]. In another Medicare study of 24,169 CRT patients (2006–2009) absence of LBBB in comparison to LBBB regardless of QRS duration, was associated with increased risk of all-cause mortality and of all-cause, cardiovascular, and heart failure readmissions [7]. Lack of efficacy, however, cannot be estimated in any of these retrospective analysis in the absence of a control group. No improvement has been observed in data from the early CRT studies in patients with RBBB including the Multicenter InSync Randomized Clinical evaluation (Miracle) n = 43 as well as the pooled data from Miracle and Contak cardiac