Abstract 200: Novel Cardiac Dyssynchrony Metrics Based on Ultrasound Images and Fibrosis

Abstract

Ventricular stiffening is a component of heart failure with preserved ejection fraction. This study focuses on building a dyssynchrony metric based on ultrasound images obtained from normal and fibrotic mouse hearts. The objective is to evaluate the association between regional fibrosis and ventricular wall dynamics as an indicator for the gradient of cardiac dyssynchrony. Ultrasound images were obtained from a previous study in which mice were given thoracic aortic constriction to induce heart failure that included ventricular stiffening and fibrosis. Ultrasound video (frame rate 4.3ms) along the short axis of the mouse heart was captured using commercial software. On each short axis frame, six points were selected and traced on the endocardial wall. Each radial displacement pair is plotted in a loop diagram against one another in 15 unique combinations. A loop whose points are close to the ideal line u = v corresponds to synchronous wall movement, while the area enclosed by the loop is proportional to time dyssynchrony. The inferior free wall and the section nearest the interventricular septum had 35% (26,48) interstitial fibrosis compared to the IS itself which had 9% (7, 13) in hearts with 25% fibrosis, and the contrast had the most variance (8.7%, P<0.0001). Strong predictors of the contrasting fibrosis included the trace perimeter and the maximal normalized displacement, but more pragmatically, the differences between the two conditions are apparent and consistent. Figure 1 is the set of (u,v) pairs measured over the course of a heartbeat where u is the radial displacement of heart segment x measured when segment y had radial displacement v.