Electrocardiographic criteria of true left bundle branch block: a simple sign to predict a better clinical and instrumental response to CRT.

BACKGROUND: Cardiac resynchronization therapy (CRT) has proved to be very effective in improving morbidity and mortality in patients affected with severe congestive heart failure. Its efficacy has been shown to be greater in patients with left bundle branch block (LBBB). The aim of our study was to verify if newly proposed criteria for true LBBB identify patients with a better clinical and instrumental response to CRT. METHODS: Between May 2007 and April 2011, 111 patients with left ventricular ejection fraction (LVEF) 64 35% and LBBB morphology received a CRT device and were divided into two groups according to QRS morphology. Group 1 (61 patients) consisted of patients with "true" LBBB morphology; group 2 (50 patients) consisted of patients with "false" LBBB. The primary endpoint was the utility of criteria for true LBBB to predict a composite endpoint of all-cause mortality and hospital admission with heart failure. The secondary endpoint was the utility of the same criteria to predict an absolute increase in LVEF 65 10%. RESULTS: "False" LBBB morphology and a dose of bisoprolol