Abstract 14223: Vector Analysis for Left Ventricular Wall Motion by Optical Flow With Echocardiographic Images in Myocardial Infarction Rat Model

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Background/Research Questions: Alternative evaluation of cardiac function may be established in echocardiography-based vector analysis of the ventricular wall motion property. Vector acceleration and direction have the potential to assess cardiac kinetic energy and dynamics. Optical flow is suitable for vector analysis, because ventricular wall motion can be estimated as visible and quantitative vectors by optical flow from 2D echocardiographic images. Aims: This study aimed to establish a vector analysis for ventricular wall motion via optical flow with echocardiography. Methods: Coronary artery ligation rat model was used in this study. Before surgery (Pre) and four weeks after surgery (MI), short axis echocardiographic images in mid portion were obtained and analyzed by optical flow for left ventricular regional wall motion. Vector accelerations and directions were measured in both systolic and diastolic phases. Vector directions were classified into inward (ID), outward (OD), and circumferential direction (counterclockwise: CC, clockwise: CW). Following echocardiography, a rat was sacrificed for histological evaluation. Results: Pathological myocardial infarction was noted in the anterolateral lesion. Comparing average vector accelerations, MI had significantly smaller acceleration vectors in both systolic and diastolic phase (Pre vs. MI in systolic: 0.006±0.002 vs. 0.002±0.001 mm/s 2 , P<0.001, Pre vs. MI in diastolic: 0.007±0.002 vs. 0.002±0.001 mm/s 2 , P<0.001). Regarding total vector direction, CC and CW significantly increased in MI (P<0.01). In the anterolateral lesion, ID and OD were the main vector directions in Pre. In contrast, CC and CW vectors significantly increased in MI (P<0.0001). Conclusions: Optical flow effectively visualized cardiac wall motions and quantify them as vectors in echocardiographic images. The technique clarified left ventricular wall vector property alterations between healthy and infarcted hearts.

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