Cardiac resynchronization therapy.

About 30% of patients with left ventricular systolic dysfunction also have ventricular conduction delays (prolonged QRS duration greater than 0.12 second) most frequently seen as left bundle branch block. This intraventricular conduction delay causes nonsynchronous ventricular activation between the right ventricle and the left ventricle (or dyssychrony), compromising cardiac function. Cardiac resynchronization therapy, or biventricular pacing, is a recent intervention for ventricular dyssychrony that incorporates 3 leads for pacing the right atrium and simultaneous pacing of the right ventricle and left ventricle. Left ventricular lead placement can be difficult to implant because of coronary venous anatomy and can require longer procedure time for the patient. Restoring ventricular synchrony has been shown to decrease septal wall dyskinesis, decrease mitral regurgitation, increase left ventricular filling time, decrease pulmonary capillary wedge pressure, and reverse ventricular modeling.