Mechanical dyssynchrony combined with septal scarring reliably identifies responders to cardiac resynchronization therapy

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): Research Foundation Flanders (FWO). Background The presence of mechanical dyssynchrony on echocardiography is associated with reverse remodeling after cardiac resynchronization therapy (CRT). In contrast, recent studies suggest that presence of myocardial scarring – particularly in the septal wall – reduces the effect of CRT. Recently, a combined assessment of mechanical dyssynchrony and septal wall scarring has demonstrated high predictive power for CRT response. However, a direct comparison of different markers of mechanical dyssynchrony has not yet been performed. Aim This study: (I) investigated how well a combined assessment of different markers of mechanical dyssynchrony and septal scarring identifies responders to CRT, and (II) evaluated potential differences in predictive power. Methods In a prospective multicentre study in 170 CRT recipients, septal flash (SF) or apical rocking (ApRock), systolic stretch index (SSI) and lateral-to-septal (LW-S) work difference were assessed on echocardiography. SSI was calculated from longitudinal strain traces of the four-chamber view as the sum of the septal systolic stretch and lateral systolic pre-stretch before aortic valve closure. The LW-S work difference was calculated from the regional work of the lateral wall and septal wall - considering the averaged work from the basal- and mid-ventricular segments in the apical four-chamber view. Myocardial scarring of the septum was quantified on cardiac magnetic resonance imaging (CMR) late gadolinium enhancement (LGE) images (n=125 patients), or excluded based on a coronary angiogram and clinical history (n=45 patients). Myocardial scarring was reported regionally as percentage of total amount of scarred tissue per wall. The study’s endpoint was CRT response, defined as ≥15% reduction in LV end-systolic volume 12 months after CRT implantation. AUC’s from ROC curves were used to investigate the predictive power of the different markers for CRT response. Results The AUC’s for the combined assessment of the markers of mechanical dyssynchrony and septal scarring as predictor of CRT-response were 0.86 (95% CI: 0.79–0.91) for presence of SF or ApRock, 0.81 (95% CI: 0.74–0.88) for SSI, and 0.84 (95% CI: 0.76–0.90) for LW-S work difference (all p<0.0001). No significant difference was observed between the different markers of mechanical dyssynchrony (p>0.05 between all). Conclusions The combined assessment of mechanical dyssynchrony and septal scarring identified CRT responders with high predictive power. Both visual and quantitative markers demonstrated similar results. Our data demonstrates the importance of assessing LV mechanics and scarring in CRT-candidates, which can easily be achieved in clinical routine.