Objectives. We sought to determine the incidence and independent prognostic value of increased serum levels of sensitive serologic markers in patients in whom a conventionally diagnosed acute myocardial infarction had been ruled out. Background. Increased serum levels of creatine kinase (CK) isoenzyme MB mass and cardiac troponin T in patients with unstable angina pectoris are associated with a poor prognosis. Methods. We analyzed data from 196 consecutive patients with suspected acute myocardial infarction, which was later ruled out in 124. Increased serum levels of CK-MB mass, troponin T and myosin light chains were compared with clinical findings, ST-T wave abnormalities and presence of arrhythmias. Results. Of the patients in the noninfarction group, 28% had serum CK-MB mass greater than or equal to 6 mu g/liter, 20% had troponin T greater than or equal to 0.20 mu g/liter, and 26% had myosin light chains greater than or equal to 0.4 mu g/liter (discrimination limits). The cardiac event rate (cardiac death, nonfatal acute myocardial infarction) within 28 months was significantly higher in patients in the noninfarction group with elevated marker levels (range 22% to 24%) than in patients with values below these discriminators (range 3% to 5%) but was not significantly different from that in patients with a definite diagnosis of acute myocardial infarction (29%). Further, significant predictors of cardiac events were previous myocardial infarction; myocardial infarction or angina pectoris, or both; previous congestive heart failure; ST-T wave abnormalities on admission; a transient ST-T wave shift on serial electrocardiograms (ECGs); recurrent chest pain; and occurrence of supraventricular or ventricular tachycardia, or both, during the Ist 48 h after admission. It was found that all three biochemical markers, in the main, convey independent prognostic information with respect to clinical findings and presence of arrhythmias but not ST-T wave abnormalities on admission or a transient ST-T wave shift on serial ECGs. Conclusions. Increased serum levels of CK-MB mass, troponin T and myosin light chains all detect a subgroup of 25% of patients without acute myocardial infarction who have as poor a prognosis as that of patients with a definite diagnosis of acute myocardial infarction. All three biochemical markers provide similar important independent prognostic information with regard to clinical findings and arrhythmias but add no additional prognostic information once ECG ST T wave changes are considered.
