Ventricular dyssynchrony in dilated cardiomyopathy: The role of biventricular pacing in the treatment of congestive heart failure

Despite advances in pharmacologic therapy, the prognosis of patients with advanced congestive heart failure (CHF) remains poor. Many of these patients have cardiac conduction abnormalities, such as left bundle-branch block or interventricular conduction delays, that can lead to ventricular dyssynchrony (abnormal ventricular activation that results in decreased ventricular filling and abnormal ventricular wall motion). Biventricular pacing is an alternative, nonpharmacologic therapy under active investigation for the treatment of CHF. Resynchronization devices with transvenous leads in the right atrium, right ventricle, and left ventricle (via the coronary sinus) have been implanted in patients to provide atrial triggered biventricular pacing. The use of such devices has been associated with improvement in ejection fraction, dP/dt, stroke work, and functional class. The proposed mechanisms involved in improving ventricular function with biventricular pacing include improved septal contribution to ventricular ejection, increased diastolic filling times, and reduced mitral regurgitation. This article reviews the pathophysiology of ventricular dyssynchrony and examine insights from clinical trials that are evaluating cardiac resynchronization therapy for CHF.