A strain-based LBBB classification predicts the degree of reverse remodeling and outcome in patients with cardiac resynchronization therapy

Abstract

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): Research Foundation Flanders (FWO). Introduction Septal strain patterns measured by echocardiography reflect the gradual process of left bundle branch block (LBBB)-induced left ventricular (LV) remodeling. We investigated whether these strain stages also predict progressive volumetric response and outcome in cardiac resynchronization therapy (CRT) patients. Methods This prospective study enrolled consecutive CRT patients from 5 European centers who underwent echocardiographic examination with speckle-tracking strain analysis before CRT implantation. Dyssynchrony was assessed using septal strain curves, which were classified into 5 patterns (stage LBBB-0 to LBBB-4). The magnitude of reverse remodeling was determined at 1 year. The pre-defined outcome was death from any cause or heart transplantation. Results The study involved 267 patients (age 66±11 years; 69% men; 90% LBBB) with a mean LV ejection fraction (EF) of 30±7%. Across the stages, CRT resulted in a gradual volumetric response, ranging from almost no response in LBBB-0 patients (ΔLV end-systolic volume −9 ±21ml; ΔLVEF +4±8%) to super-response in LBBB-4 patients (ΔLV end-systolic volume −85 ±54ml; ΔLVEF +20±9%) (p<0.001 for both). Median follow-up was 49 months. LBBB-0 patients had worst outcome (log rank p = 0.002, Figure), with subsequent LBBB stages gradually showing more favorable outcome (log rank p = 0.045, Figure). There was a stepwise decrease in adverse events according to the staged LBBB classification. LBBB stages 1 to 4 predicted long-term survival without heart transplantation with respective hazard ratios of 0.61 (95% CI 0.25–1.50), 0.26 (95% CI 0.10–0.68), 0.29 (95% CI 0.11–0.77) and 0.13 (95% CI 0.04–0.51) compared to LBBB-0. After multivariable adjustment for baseline LVEF, ischemic heart disease and presence of an implantable cardioverter defibrillator, LBBB staging remained significantly associated with a decreased risk for adverse outcome (hazard ratio 0.69 (95% CI 0.51–0.92) per 1-stage increase). Conclusions Septal strain patterns are associated with the extent of reverse remodeling and outcome in CRT patients. The proposed LBBB classification provides pathophysiological insights in LBBB-induced LV dysfunction and may be helpful to identify patients who may benefit most from CRT implantation.