 Cardiac resynchronization therapy CRT with biventricular pacing has emerged as a novel treatment for congestive heart failure CHF not responsive to optimal drug therapy. CRT is associated with significant improvements in hemodynamics and functional status of patients with CHF. The physiologic effect of CRT is achieved via placing electrical leads in the right and left ventricular walls, and synchronizing ventricular contraction. Over time, this leads to ventricular wall reverse remodeling, and sustained improvements in left ventricular ejection fraction EF. 