Patients with Heart Failure and Right Bundle Branch Block or Nonspecific Intraventricular Conduction Disturbances Can They Benefit from Cardiac Resynchronization Therapy?

Abstract

Biventricular pacing (BVP) has recently been proposed for the treatment of patients with drug-resistant heart failure and long QRS duration [1–6]. The rationale for this suggestion is based on the high prevalence of inter- and intraventricular conduction delay among patients with heart failure [7–9] and on the resultant poor coordination of ventricular contraction and relaxation [9–11], which worsens the left-ventricular dysfunction. The purpose of BVP is to restore ventricular relaxation and contraction sequences as homogeneously as possible by providing right and left ventricular pacing simultaneously. Up to now, this specific pacing mode has been applied to heart failure patients with left bundle branch block (LBBB) to shorten the significant right-to-left inter-ventricular delay with or without intraventricular asynchrony [12–14]. Recently, it was suggested that complete right bundle branch block (RBBB) should be considered as an independent predictor of mortality, and especially in heart failure patients, with the same weighting as LBBB [15]. Since not only marked right-to-left, but also left-to-right, interventricular delay observed on the surface electrocardiogram (ECG) worsens the burden of heart failure, there has been some speculation to the effect that BVP might also benefit patients with severe congestive heart failure and complete RBBB, on the basis that there may be a concomitant left-sided intraventricular conduction disorder that remains invisible on the surface ECG. Recently, several studies have suggested that the presence of a marked left intraventricular electromechanical delay is more likely than the QRS width to be the major criterion identifying patients who will respond to BVP [16–19].