1KU Leuven Cardiovascular Sciences Leuven, Belgien; 2Ghent University Hospital Cardiology Ghent, Belgien; 3Oslo University Hospital Cardiology Oslo, Norwegen; 4CHU Rennes Cardiology Rennes, Frankreich; 5OLV Aalst Cardiology Aalst, Belgien
Echocardiography-derived septal strain patterns can serve as indicators of progressive left ventricular (LV) remodelling caused by left bundle branch block (LBBB)-induced dyssynchrony. This study aims to address the prognostic value of these strain patterns in predicting volumetric responses and clinical outcomes among patients undergoing cardiac resynchronization therapy (CRT).
Methods
In this prospective multicentre study, CRT candidates from five European centres received pre-implantation echocardiographic assessments with speckle-tracking strain analysis. Dyssynchrony feature analysis of septal strain curves categorized patients into five distinct patterns, denoted as strain Stage-0 through strain Stage-4. The extent of reverse remodelling was assessed after one year, and the primary outcome was defined as all-cause mortality or heart transplantation.
Results
A total of 267 patients, with a mean age of 66±11 years (69% males, 90% LBBB) presented with an average LV ejection fraction (EF) of 30±7%. Across the identified LBBB stages, CRT yielded a progressive volumetric response, with minimal improvements in Stage-0 patients (ΔLV end-systolic volume -9±21ml; ΔLVEF +4±8%) and substantial responses in Stage-4 patients (ΔLV end-systolic volume -85±54ml; ΔLVEF +20±9%) (p<0.001 for both). Median follow-up extended to 49 months. Stage-0 patients exhibited the least favourable outcome (log rank p=0.002, Figure), while subsequent LBBB stages exhibited progressively more favourable outcome (log rank p=0.045, Figure). The occurrence of adverse events decreased gradually along the strain stages, with strain Stages 1 through 4 predicting long-term survival without heart transplantation, each with corresponding 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 Stage-0. After adjusting for baseline LVEF, ischemic heart disease, and the presence of an implantable cardioverter defibrillator, strain staging maintained a significant association with a reduced risk of adverse outcomes (hazard ratio 0.69 (95% CI 0.51-0.92) per one-stage increase).
Conclusions
Septal strain patterns show a clear association with the extent of reverse remodelling and outcome in CRT patients. The proposed strain staging classification offers valuable insights into the pathophysiology of LBBB-induced LV remodelling and may assist in the identification of candidates that may benefit most from CRT implantation.