Background: It has been shown that myocardial stiffness increases during ischemia. This stiffness recovers if myocardial contractility improves (stunning), and remains if the myocardium becomes infarcted. Since it is important to differentiate between these situations, we tested the hypothesis that it may be possible to predict the transmurality of myocardial infarction by using speckle tracking echocardiography derived circumferential strain rate.
Methods: Eleven rats underwent occlusion of the left anterior descending artery for 30 minutes, followed by reperfusion. Short-axis scans of the apex were acquired at baseline, 20 minutes post-MI and two weeks post-MI. The scans were post-processed by a speckle tracking echocardiography program to measure the circumferential strain and strain rate. Thereafter, the rats were sacrificed, and histological analysis of the MI size and transmurality was performed.
Results: – Six rats developed transmural MI and five rats developed small non-transmural MI. The strain results are summarized in Table 1. Twenty minutes post-MI only the A wave of the group that developed transmural MI decreased from baseline (P<0.01). Two weeks later, the peak global strain and the S wave decreased as well for this group (P<0.01). For the group that developed non- transmural MI, the S wave decreased 2 weeks post-MI (P<0.01) whereas the A wave remained unchanged.
Conclusion: – The strain rate A appears to accurately differentiate between rats that will develop transmural vs. non transmural MI.
