Time course of functional improvement in stunned myocardium in risk area in patients with reperfused anterior infarction

Background. The beneficial effect of coronary reflow on myocardial salvage may be assessed more accurately than in previous studies if the size of risk area is taken into account, particularly because the size of risk area varies significantly among patients. In this study, the risk area was determined with myocardial contrast echocardiography to investigate the time course of functional recovery of postischemic myocardium within the risk area in patients with reperfused anterior myocardial infarction. Methods and Results. The study population consisted of 21 patients with anterior myocardial infarction who achieved coronary reflow within 6 hours of onset by means of thrombolysis or coronary angioplasty. Myocardial contrast echocardiography was performed with the injection of hand-agitated Haemaccel (5 ml) into the right and left coronary arteries before coronary reflow, and the risk area was defined as the area of contrast perfusion defect in the apical long-axis view. The ratio of the endocardial length of abnormal contraction (dyskinesis/akinesis) segment to that of contrast defect segment (AS/CD) was determined at days 1, 2, 3, 7, 14, and 28 of reflow. Before reflow, the length of contrast defect correlated well with the segment length of dyskinesis/akinesis. The values for AS/CD in patients with successful reperfusion significantly and progressively decreased until day 14; 1.00±0.02 at day 1, 0.93±0.11 at day 2 (p<0.05 versus day 1), 0.84±0.16 at day 3 (p<0.05 versus day 2), 0.80±0.13 at day 7 (p<0.01 versus day 2), 0.73±0.10 at day 14, and 0.72±0.10 at day 28. Greater improvement in function was obtained in patients reperfused within 4 hours than in those reperfused at ≥4 hours (AS/CD at day 28, 0.64±0.12 versus 0.75±0.09, p<0.05). Conclusions. Thus, a significant amount of myocardium, an average of 28% in segment length of the risk area, is salvaged in patients with reperfused anterior myocardial infarction. Major functional improvement seems to be achieved within 14 days of reflow.