Evaluation of changes in transmural mechanics of stunned myocardium in dogs with speckle tracking imaging

Objective To explore the cross-wall mechanical change and its variation with time through evaluation on the systolic longitudinal strain changes of endocardium, epicardium overall canine stunned myocardium during ischemia and reperfusion with two-dimensional speckle tracking imaging (2D-STI). Methods Left anterior descending coronary artery of 12 dogs was ligated for 20 min and then reperfused for 120 min, respectively. Apex aspect images were acquired before ligation, during ligation period, reperfusing immediately and 30, 60, 90, 120 min after reperfusion, respectively. Two-dimensional ultrasound speckle tracking imaging was used to detect the systolic strain parameters of endocardium, epicardium in ischemia and non-ischemic segments: Peak longitudinal strain (LSpeak) and its delayed time to peak strain (TPSLS), and a comparative analysis was done as well. Results During left anterior descending coronary artery ligation, immediately after reperfusion ischemic heart segment, LSpeak of endocardium, epicardium and overall myocardium decreased significantly, TPSLS prolonged, and LSpeak reduced more obviously in endomyocardium. With the extension of reperfusion, strain parameters gradually restored, but the epicardial myocardium recovered faster, and ischemic myocardial segments as a whole returned to normal when the subendocardial did not yet return to normal. A marked increase of LSpeak and TPSLS was found immediately after reperfusion in non-ischemic segments in the left anterior descending coronary artery ligation, and recovered to normal 30 min later. Conclusion Two-dimensional ultrasound speckle tracking imaging can detect two-dimensional strain change of endocardium and epicardium in dogs with ischemia and reperfusion.