Mechanical Wave Velocities by High Frame Rate Echocardiography Identifies Myocardial Dysfunction in Acute Coronary Syndrome

BACKGROUND: Mechanical waves propagating within the myocardium offer insight into tissue stiffness that can be measured by high frame rate echocardiography. This may provide information on myocardial tissue properties in acute myocardial infarction (AMI) incremental to traditional echocardiographic metrics. OBJECTIVES: To investigate whether natural mechanical wave velocities in the left ventricle (LV) are altered in AMI and to establish the feasibility of measuring mechanical wave velocities in all LV regions in AMI patients. METHODS: We examined 60 patients (66±9 years, 72% male) with AMI by high frame rate echocardiography within one day after revascularisation therapy. Natural mechanical waves generated by the atrial kick (AK), mitral valve closure (MVC) and aortic valve closure (AVC) were analysed by clutter filter wave imaging for all LV regions. RESULTS: AK wave velocities were faster in regions with wall motion abnormalities (WMA) compared to regions without (2.9 (2.1-4.6) m/s vs. 2.2 (1.7-2.8) m/s, p=0.004), whereas no differences were observed for MVC or AVC waves. Elevated AK wave velocities were associated with myocardial dysfunction assessed by LV longitudinal strain (β=0.49 (0.26-0.71), p<0.001) and WMA (OR 1.6 (1.3-2.0), p<0.001) by multivariable mixed-model regression analyses adjusting for age, gender and parameters of diastolic function, and for WMA also adjusted for LV longitudinal strain (OR 1.4 (1.0-1.8), p=0.022). Feasibility for measuring AK waves was high in all regions (mean 89%), but lower for MVC/AVC waves (mean 44% and 46%, respectively, p<0.001). Feasibility was lower from basal to apical segments for all wave types (p<0.001). CONCLUSIONS: AK wave velocities were faster in infarcted territories of AMI patients and were independently associated with myocardial dysfunction assessed by LV longitudinal strain and WMA. AK waves could be measured with good feasibility in all LV regions. The lower feasibility for MVC and AVC waves suggests differences in propagation dynamics or intrinsic wave properties.