Local Measurement of Instantaneous Change in Myocardial Thickness in Swine Heart During Acute Myocardial Ischemia

Ultrasound-based local strain rate (SR) measurement can detect the abnormality of the myocardial contraction owing to ischemia with high sensitivity. In the present paper, the local SR measurement using the velocity estimator based on the multifrequency phase differences was applied to the open-chest heart of swine during acute myocardial ischemia to capture the abnormality of the myocardial contraction. For the normal condition, some myocardial layers became thin during the systole even though the whole thickness of the heart wall increased. Interestingly, for the ischemic condition, the rate of the myocardial layers thinning during the systole decreased. In addition, the magnitude of thickening in the measured local SR distribution during the systole decreased in the ischemic condition. This may be caused by acute myocardial ischemia because the magnitude of thickening corresponds to the contractile force of the myocardium and it decreases in acute myocardial ischemia. The difference between the baseline and the ischemic condition was observed in the measured local SR distribution during the systole, even after only a few seconds from the occlusion of the coronary artery.