Does daily precordial ST-segment mapping detect myocardial infarct extension in patients with acute myocardial infarction?
Precordial ST-segment mapping using a 48-lead system can detect myocardial infarct extension days after the initial event, suggesting a prolonged window for interventions to decrease myocardial ischemia.
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 ischemia may be effective for many days after the onset of acute myocardial infarction. (N Engl J Med 290:123–128, 1974)
Reid et al. (Thu,) studied this question.