Temporal changes in myocardial perfusion patterns in patients with reperfused anterior wall myocardial infarction. Their relation to myocardial viability.

BACKGROUND: Several studies demonstrated ischemic microvascular damage in patients with acute myocardial infarction (AMI). In this study, myocardial contrast echocardiography (MCE) was used to assess the temporal changes in myocardial perfusion after reflow and to investigate the relation between MCE findings and myocardial viability.

METHODS AND RESULTS: MCE was performed with the intracoronary injection of sonicated microbubbles before and shortly after coronary reflow and 1 month later in 45 patients with anterior wall AMI. MCE before reflow was analyzed to determine the risk area as an area of contrast defect in the apical long-axis view. MCE images after reperfusion were analyzed to determine peak contrast intensity, which should be in proportion to the concentration of microbubbles within the microvasculature and in the infarcted and normal myocardium, and the ratio of these (PI ratio) was used to assess microvascular integrity. Areas of residual contrast defect were expressed as a ratio to those of left ventricular myocardial (RCD ratio) to assess the spatial extent of the MCE "no reflow." Regional wall motion (RWM, SD per chord) in the territory of the left anterior descending coronary artery was determined by the centerline method in both the acute and late stages. Although the PI ratio was extremely low shortly after coronary reflow, it increased in the late stage of AMI with the improvement in regional contractile function (RWM, -3.2 +/- 0.5 versus -2.6 +/- 1.0, P < .01; PI ratio, 0.44 +/- 0.25 versus 0.60 +/- 0.29, P < .01). Reduction in the RCD ratio was observed even in 15 patients with MCE no reflow in the acute stage (0.33 +/- 0.09 versus 0.16 +/- 0.11, P < .01). Then we investigated the relation between residual contractile function and microvascular integrity in the late stage. A significant correlation was found between the PI ratio and RWM (r = .73, P < .001) in the late stage of the AMI.

CONCLUSIONS: (1) Recovery from ischemic microvascular damage is generally observed in the late stage of AMI in association with improvement in myocardial contractile function. The degree of improvement in contractile function and microvascular integrity, however, varies among patients. (2) Contrast peak intensity in the late stage of infarction may provide a useful estimate of myocardial viability.