ABSTRACT
Cardiac resynchronization therapy (CRT) is an established therapy for heart failure patients, which can improve clinical symptoms, left ventricular (LV) function, and long-term prognosis. Current American Heart Association/American College of Cardiology/European Society of Cardiology guidelines include CRT as a class IA indication for heart failure patients with New York Heart Association (NYHA) functional class III-IV(ambulatory) symptoms, LV ejection fraction <35%, and wide QRS duration (with left bundle branch block (LBBB) morphology or >150 msec duration for non-LBBB morphology).1 In addition, the benefi - cial effects of CRT on clinical symptoms, LV function, and prognosis have been demonstrated in large randomized clinical CRT trials including NYHA functional class II heart failure patients. Accordingly, the indications of CRT have been extended to this subgroup of mildly symptomatic heart failure patients.1
