Influence of QRS duration and axis on response to cardiac resynchronization therapy in chronic heart failure with reduced left ventricular ejection fraction: A single center study including patients with left bundle branch block

Background: The aim of the study was to evaluate QRS duration and axis as predictors of response to cardiac resynchronization therapy (CRT) in order to reduce the proportion of non-responders. Methods: Retrospective single-center study including 42 CRT recipients, with left bundle branch block (LBBB), left ventricular ejection fraction (LVEF) < 40%, in New York Heart Association (NYHA) class II. Response to CRT was declared as NYHA class improvement >= 1 (symptomatic) and LVEF improvement by >= 10% (echocardiographic) > 6 months post implantation. Results: Symptomatic responders had longer pre- (172.3 -+/- 17.9 vs. 159.0 +/- 18.3 ms; p = 0.027) and postimplantation (157.2 +/- 24.1 vs. 136.7 -+/- 23.2 ms; p = 0.009) QRS duration. Preimplantation QRS < 150 ms predicted poor response (odds ratio [OR] for response vs. lack of response 0.04; 95% confidence interval [CI] 0.001-0.74). Predictors of symptomatic response included: postimplantation QRS > 160 ms (OR 7.2; 95% CI 1.24-41.94), longer QRS duration before (OR for a 1 ms increase 1.04, 95% CI 1.00-1.08) and post implantation (OR for a 1 ms increase 1.04; 95% CI 1.01-1.07). Area under the curve (AUC) for pre- and postimplantation QRS duration was 0.672 (95% CI 0.51-0.84) and 0.727 (95% CI 0.57-0.89), respectively, with cut-off points of 178.5 ms and 157 ms. For post plantation QRS axis, AUC was 0.689 (95% CI 0.53-0.85), with cut-off points of -60.5 degrees or -38.5 degrees. Preimplantation QRS axis was the only predictor of echocardiographic response (OR 0.98; 95% CI 0.96-1.00), with AUC of 0.693 (95% CI 0.54-0.85) and a threshold of -36 degrees. Conclusions: Marked pre- and postimplantation QRS prolongation and preimplantation negative QRS axis deviation are moderate predictors of response to CRT.