Cardiac resynchronization therapy

Abstract

Electrophysiological disturbances are common in the setting of chronic left ventricular dysfunction with or without heart failure. Approximately one-third of patients with systolic heart failure have a QRS duration greater than 120 millisecond, which is most commonly manifested as left bundle branch block [1,2]. Such electrical disturbances result in left ventricular (i.e., intraventricular) dyssynchrony with paradoxical septal wall motion, which further impairs the pumping ability of an already struggling heart [3-6]. In particular, left ventricular dyssynchrony causes suboptimal ventricular filling, prolonged duration of mitral regurgitation, and a reduction in left ventricular pressure development (dP/dt). Interventricular dyssynchrony also occurs in the setting of bundle branch block, adversely affecting the timing of left and right ventricular ejection. Ventricular dyssynchrony, defined electrocardiographically by a prolonged QRS duration, has been associated with increased mortality in heart failure patients [7-10].