Abstract
Methods for detecting acute. myocardial infarction (AMI) were compared in a prospective study of 726 patients with pain presumed to be caused by ischemia that lasted 30 minutes or longer and was associated with electrocardiographic changes (ST-segment deviation ≥0.1 mV and/or new Q waves or left bundle branch block). Using MB-CK values of more than 12 IU/liter as the standard criterion for detection of AMI, 639 patients (88%) were judged to have AMI. Total plasma CK values, technetium-99m stannous pyrophosphate images 48 to 72 hours after admission, and serial 12-lead electrocardiograms over 10 days were analyzed by investigators blinded to other clinical and laboratory data. For detection of AMI, total CK, electrocardiograms (ECGs) and pyrophosphate imaging were all highly accurate and sensitive (total CK accuracy 97%, ECG 92%, pyrophosphate 88%; total CK sensitivity 98%, ECG 96% and pyrophosphate 91%). However, both pyrophosphate and ECG were less specific than total CK (p <0.01) (total CK specificity 89%, pyrophosphate 64% and ECG 59%). The sensitivity (p <0.05) and accuracy (p <0.01) of total CK and pyrophosphate for those patients with Q-wave development were slightly greater than for those in whom Q waves did not evolve. The ECG was less accurate (p < 0.02) and pyrophosphate was less specific (p <0.04) in patients with prior MI compared with those with initial infarction. Pyrophosphate failed to detect larger infarcts than either the ECG or total CK (both p <0.01). However, combined pyrophosphate and electrocardiographic criteria were more accurate than pyrophosphate (p <0.01) or the ECG alone (p <0.03), and pyrophosphate was helpful in identifying infarcts considered "indeterminate" on the ECG. Although each method has certain limitations, individual and combined use of these diagnostic criteria represent powerful means for detecting AMI. © 1985.