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 gene rally smaller benefit-to-risk ratio of reperfusion therapy. We studied the relationship between ST changes and the perfusion territory of th e infarct-related artery in 95 patients: 77 with proximal right corona ry related infarction (perfusion territory quantitated by an angiograp hic score, maximum possible value=1.0) and 18 with circumflex related infarction (divided angiographically into proximal and distal arterial cocclusions). 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 univa riate 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 mu ltivariate analysis, only precordial ST depression and the number of l eads with ST elevation were independent predictors of the angiographic score (r=0.64), with precordial ST depression predicting the major po rtion of its variability. For circumflex related infarction, precordia l ST depression was the only predictor of a proximal occlusion. Summed precordial ST depression greater-than-or-equal-to 0.3 mV, as compared to less or no ST depression, predicted a larger territory of the infa rct-related artery (either a right coronary angiographic score >0.5 or a proximal left circumflex lesion, kappa=0.51, P<0.001). In acute inf erior infarction, deep precordial ST depression reflects large jeopard ized territory, a subgroup that may benefit more from aggressive reper fusion.