ST isopotential precordial surface maps in patients with acute myocardial infarction

ST amplitude distributions were studied in 41 patients with acute myocardial infarction by deriving isopotential maps from a 5×7 electrode precordial matrix. Independent data on infarct size and localization were obtained utilizing the technetium 99m stannous pyrophosphate scintigraphic method. The locus of maximal ST elevation was stable for at least two days in 86% of 27 patients with anterior infarction. A single maximum or maximum-minimum was found in 88% but 22% of the patients had multiple maxima and/or minima in at least two maps. Areas of significant ST elevation were often excluded from the precordial matrix. The site of maximal ST elevation correlated with scintigraphic infarct site but was displaced medially in lateral infarction. The relation between infarct size and ΣST elevation was significant and curvilinear. ΣST underestimated size in large anterior infarction. The correlation of the size and the number of sites with ST elevation ≥1.5 mm was weak (r=0.56). The degree of ST abnormality in 14 patients with inferior infarction decreased significantly during the initial 24 hours. The isopotential maps were similar to those obtained in anterior infarction but the polarity was reversed. The results provide limited support for the continued exploration of ST analysis as a clinical method but suggest that sizing methods should be based on total body surface mapping, taking into account the geometry and electrical properties of the torso.