In 3D computational models, combined dilation and left bundle branch block synergistically decreased regional cardiac function, detected by CURE (decreased 23%) and ISF (increased 20-fold).
Are CURE and ISF more sensitive than WTpeak to regional mechanical nonuniformity caused by ventricular dilation and electrical dyssynchrony in computational models?
Computational modeling demonstrates that CURE and ISF are more sensitive indices of regional mechanical nonuniformity than WTpeak in the setting of combined ventricular dilation and electrical dyssynchrony, potentially explaining their utility in predicting CRT response.
BACKGROUND: Heart failure (HF) in combination with mechanical dyssynchrony is associated with a high mortality rate. To quantify contractile dysfunction in patients with HF, investigators have proposed several indices of mechanical dyssynchrony, including percentile range of time to peak shortening (WTpeak), circumferential uniformity ratio estimate (CURE), and internal stretch fraction (ISF). The goal of this study was to compare the sensitivity of these indices to 4 major abnormalities responsible for cardiac dysfunction in dyssynchronous HF: dilation, negative inotropy, negative lusitropy, and dyssynchronous activation. METHODS AND RESULTS: All combinations of these 4 major abnormalities were included in 3D computational models of ventricular electromechanics. Compared with a nonfailing heart model, ventricles were dilated, inotropy was reduced, twitch duration was prolonged, and activation sequence was changed from normal to left bundle branch block. In the nonfailing heart, CURE, ISF, and WTpeak were 0.97+/-0.004, 0.010+/-0.002, and 78+/-1 milliseconds, respectively. With dilation alone, CURE decreased 2.0+/-0.07%, ISF increased 58+/-47%, and WTpeak increased 31+/-3%. With dyssynchronous activation alone, CURE decreased 15+/-0.6%, ISF increased 14-fold (+/-3), and WTpeak increased 121+/-4%. With the combination of dilation and dyssynchronous activation, CURE decreased 23+/-0.8%, ISF increased 20-fold (+/-5), and WTpeak increased 147+/-5%. CONCLUSIONS: Dilation and left bundle branch block combined synergistically decreased regional cardiac function. CURE and ISF were sensitive to this combination, but WTpeak was not. CURE and ISF also reflected the relative nonuniform distribution of regional work better than WTpeak. These findings might explain why CURE and ISF are better predictors of reverse remodeling in cardiac resynchronization therapy.
Kerckhoffs et al. (Fri,) conducted a other in Heart failure with mechanical dyssynchrony. Simulated ventricular dilation and dyssynchronous activation (LBBB) vs. Nonfailing heart model and isolated abnormalities was evaluated on Sensitivity of mechanical dyssynchrony indices (CURE, ISF, WTpeak) to cardiac abnormalities. In 3D computational models, combined dilation and left bundle branch block synergistically decreased regional cardiac function, detected by CURE (decreased 23%) and ISF (increased 20-fold).