Interplay between strain pattern-based classification of dyssynchrony and myocardial scar in CRT patients

Abstract Introduction Echocardiography-derived septal strain patterns are valuable for predicting volumetric reverse remodelling and survival in patients undergoing cardiac resynchronization therapy (CRT). Nevertheless, presence of myocardial scarring in the left ventricle (LV) is known to attenuate CRT treatment response. Purpose This study aims to investigate the interplay between septal strain patterns and myocardial scarring in CRT candidates, and how they link to outcome after CRT. Methods In this prospective multicentre study, CRT candidates from five European institutions underwent pre-implantation assessments using speckle-tracking strain analysis on echocardiography and cardiac magnetic resonance imaging (CMR) with late gadolinium enhancement (LGE). Dyssynchrony was graded through analysis of septal strain curves, categorizing patients into five distinct patterns, denoted as strain Stage-0 through strain Stage-4 (Fig. A). LGE of the LV wall was quantitatively assessed using CMR (as a percentage). The study endpoints were volumetric reverse remodelling (volume responder = more than 15% decrease LV end-systolic volume) after one year, and all-time all-cause mortality. Results A total of 267 patients, with a mean age of 66±11 years (69% males, 90% left bundle branch block [LBBB]) presented with an average LV ejection fraction (EF) of 30±7%. With each stepwise increase in strain stage, global LV scarring decreased (p<0.01; Fig. B) and the proportion of volume responders increased (all p<0.0001; Fig. C). ROC curves demonstrated that the predictive power of strain stages for CRT volumetric response was not significantly improved when scarring percentage was added (AUC 0.78 [95% CI: 0.69-0.83] vs. 0.81 [95% CI: 0.71-0.90]; p>0.05; Fig. D). In a multivariate cox regression model – including clinical characteristics that were significantly related to survival in univariate analysis – a patients’ strain stage was the only significant predictor of survival, also outperforming scar burden as determinant of outcome (HR 0.68; p=0.041; Fig. E). Conclusions Septal strain patterns show a strong association with the extent of reverse remodelling and outcome in CRT-treated patients. An inverse relationship is observed between pre-implant strain stages and the extent of myocardial scarring. However, scar burden did not provide incremental predictive value over the strain stages. Strain-pattern-based dyssynchrony assessment is a meaningful predictive marker which integrates information on myocardial dysfunction due to dyssynchrony as well as scar burden.