Resynchronization Therapy for Congestive Heart Failure.

Ventricular contraction is achieved by the coordinated electrical activation of the ventricles through the action of the cardiac conduction system. In the presence of left bundle branch block (LBBB) or interventricular conduction delay (IVCD), the ventricular contraction pattern is desynchronized and the stroke volume is reduced as a consequence. In patients with congestive heart failure (CHF) due to systolic dysfunction, the presence of LBBB or IVCD further degrades ventricular function, contributing directly to the severity of their CHF symptoms. Cardiac resynchronization therapy (CRT) through biventricular pacing relieves CHF symptoms and improves functional status in patients with medically refractory heart failure due to left ventricular systolic dysfunction and LBBB or IVCD. The benefits of CRT are due to improvement in the ventricular activation sequence, resulting in a more coordinated and efficient ventricular contraction. In addition to symptomatic benefits, available data support the hypothesis that CRT alters the natural history of CHF in patients with intraventricular conduction delay.