Figure 1: Study Flow Chart and Group Categorization

CRT = cardiac resynchronization therapy; echo = echocardiography; LBBB = left bundle branch block; LV = left ventricular; NICSMR = nonischemic chronic severe mitral regurgitation; pts = patients; Upgrade = upgrading to cardiac resynchronization therapy from a right ventricular pacer/implantable cardioverter-defibrillator.