Variability of myocardium at risk for acute myocardial infarction

The objective of this study was to assess the variability in myocardium at risk and relate this to coronary angiographic variables. One hundred ninety -seven patients with greater than or equal to 1-mm ST-segment elevation in 2 contiguous electrocardiographic leads, without prior myocardial infarctio n, were injected with technetium-99m sestamibi acutely before reperfusion t herapy. The perfusion defect was quantified to determine myocardium at risk for infarction. patients underwent coronary angiography to determine the i nfarct-related artery and to classify the occlusion as proximal or not prox imal. Collateral and anterograde (Thrombolysis In Myocardial Infarction [TI MI] trial) flow were assessed in a subset of 83 patients with angiography b efore direct angioplasty. Myocardium at risk for infarction in the distribu tion of the left anterior descending coronary artery was significantly grea ter (p <0.0001) than that in the circumflex or right coronary artery. In th e left anterior descending coronary artery distribution, myocardium at risk for infarction was significantly larger for proximal occlusions (p <0.0001 ). There was a trend toward greater myocardium at risk for infarction of pr oximal occlusions (p = 0.14) of the left circumflex but not for proximal oc clusions in the right coronary artery distribution (p = 0.47). Multivariate analysis revealed that the infarct-related artery (p <0.0001), TIMI flow ( p = 0.0002), and proximal location (p = 0.09) in the infarct-related artery were independent predictors of myocardium at risk for infarction. Thus, in farct related artery, TIMI flow, and proximal location of occlusion in the infarct-related artery influence the myocardium at risk for infarction, whi ch is highly variable for given location of occlusion. (C)1999 by Excerpta Medica, Inc.