Myocardial-infarct extension detected by precordial ST-segment mapping.

Abstract Daily precordial ST-segment mapping was performed with the millimeter sum of ST-segment deviation (ΣST) in a 48-lead system (1 mv = 20 mm) to evaluate 26 normal subjects and 19 patients with acute myocardial infarction. At the time of admission, ΣST (± S.D.)for transmural infarction (men + 140 ± 84.8, and women + 95.7 ± 8.8) and nontransmural infarction (-67 ± 32) was significantly different (p<0.001) from controls (men + 30.1 ± 18.1, and women + 17 ± 11.7). ΣST approached normal values by 10.6 and 13 hospital days, respectively. Twelve of 14 patients (86 per cent) with transmural infarction had re-elevation of ΣST ( + 76 ± 49.7) 5.8 days (mean) after admission. This finding was associated with abnormal creatine phosphokinase in eight (57 per cent), suggesting infarct extension. Standard six precordial leads did not reflect re-elevation of ΣST in four of the 12 patients with infarct extension. The 86 per cent incidence of infarct extension indicates that measures designed to decrease myocardial i...