Implications of ST changes in reperfusion management of acute inferior myocardial infarction

ST elevation is the basis of management decisions in acute myocardial infarction and may provide a quick means of stratifying patients. This is particularly relevant with inferior infarction because of the generally smaller benefit-to-risk ratio of reperfusion therapy. We studied the relationship between ST changes and the perfusion territory of the infarct-related artery in 95 patients: 77 with proximal right coronary related infarction (perfusion territory quantitated by an angiographic score maximum possible value = 1.0) and 18 with circumflex related infarction (divided angiographically into proximal and distal arterial occlusions). For right coronary related infarction, the angiographic score ranged widely from 0.25 to 0.82 (mean 0.53, standard deviation 0.13). Parameters that correlated with the angiographic score on univariate analysis were precordial ST depression (r = -0.59), inferior ST elevation (r = 0.51), and number of leads with ST change (r = 0.56). On multivariate analysis, only precordial ST depression and the number of leads with ST elevation were independent predictors of the angiographic score (r = 0.64), with precordial ST depression predicting the major portion of its variability. For circumflex related infarction, precordial ST depression was the only predictor of a proximal occlusion. Summed precordial ST depression > or = 0.3 mV, as compared to less or no ST depression, predicted a larger territory of the infarct-related artery (either a right coronary angiographic score >0.5 or a proximal left circumflex lesion, kappa = 0.51, P < 0.001). In acute inferior infarction, deep precordial ST depression reflects large jeopardized territory, a subgroup that may benefit more from aggressive reperfusion.