Should a Patient with Severe Left Ventricular Dysfunction, Congestive Heart Failure, and Right Bundle Branch Block QRS Receive Cardiac Resynchronization Therapy?

Cardiac resynchronization therapy (CRT) is an effective treatment for patients with heart failure and mechanical dyssynchrony. Patients with left bundle branch block and QRS greater than or equal to 150 milliseconds derive the greatest clinical response. Patients with right bundle branch block (RBBB) may not derive the same benefit. The reasons for this disparity are unclear, but may relate to differences in biventricular activation sequence and timing in the presence of left versus RBBB. This article provides a comprehensive review of current understanding of the clinical effectiveness of CRT in patients with left ventricular dysfunction and RBBB.