Biventricular pacing and cardiac resynchronization therapy: a fresh approach to heart failure and intraventricular conduction delay.

Approximately 25% of patients diagnosed with symptomatic heart failure have evidence of significant intraventricular conduction delay defined by a QRS width greater than 120 ms. Heart failure leads to dysynchronous ventricular contraction, mechanical inefficiency and further impairment of left ventricular function. Patients with severe heart failure are also more likely to be burdened by mitral regurgitation. Biventricular pacing is a new therapy for heart failure refractory to standard pharmacological therapy. Biventricular pacing has been shown to improve the hemodynamics of patients with intraventricular conduction delay and low ejection fraction. This is done by simultaneous electrical stimulation of both ventricles. This is a review of recent evidence on the efficacy of biventricular pacemakers, cardiac resynchronization therapy, and the pathophysiology underlying the use of these therapies.