Abstract 18768: Comparison of Displacement-Based and Radial Uniformity Ratio Estimate Dyssynchrony Metrics in Serial Echocardiography of Post-Infarct Mice

Abstract

Background: Many of the existing dyssynchrony metrics rely on myocardial strain measurements, including circumferential uniformity ratio estimate (CURE) and related metrics such as RURE. Since strain is a derivative of displacement, amplification of noise in strain calculations due to noisy displacement data is common, thus compromising strain-based dyssynchrony metrics. We propose a novel displacement-based dyssynchrony metric, called Dyskinesia Index (DI), that is sensitive and consistent in detecting left ventricular (LV) dyssynchrony, particularly dyskinesia.

Methods: Long-axis (LA) cines of 7 C57BL/6 mice were captured with a 30MHz ultrasound transducer. Baseline (B) data were acquired prior to myocardial infarction (MI) induced by a 1-hr occlusion of the LAD followed by reperfusion. Thereafter, cines were acquired at 2, 4, 7, 14 and 28 days post-MI. Displacements were quantified using speckle tracking on the LA cines. DI was determined using Fourier analysis of radial displacement distributed along the endocardial wall, and is the square root of the ratio of the zero-order power term to the sum of zero-order and a scaled first order power terms.

Results: In Fig. 1, DI is compared to RURE at B and at 5 time-points post-MI. DI values at B are consistently close to 1 (0.96±0.01), and decrease significantly early after MI due to dyskinesia, reaching a minimum at D4 (0.64±0.08). After the first week, motion in the infarct zone becomes more akinetic due to scar formation and DI values partially recover to a plateau late after MI. ANOVA reveals significant differences between B and all post-MI time-points (p < 0.05). In contrast, RURE is less sensitive to dyskinesia at D4 and post-MI estimates are only significant from B for after D4 (p < 0.05).

Conclusion: Strain-based measures of dyssynchrony are error-susceptible without proper filtering of displacement data. DI has been shown to work well in ultrasound B-mode images, where image artifacts can degrade displacement data.