Myoglobin levels at 12 hours identify patients at low risk for 30-day mortality after thrombolysis in acute myocardial infarction: A thrombolysis in myocardial infarction 10B substudy

Objective We sought to identify, by use of serum cardiac markers, patients at low risk for 30-day mortality after ST-segment elevation myocardial infa rction. Background Baseline cardiac markers are currently used to identify patients at increased risk for short-term events. We hypothesized that serum marker s measured after treatment could identify patients at low risk for 30-day m ortality. Methods A total of 839 patients from the Thrombolysis in Myocardial Infarct ion (TIMI) 10B study had myoglobin, cardiac-specific troponin-1, creatine k inase (CK)-MB measurements at the following time points, baseline, 90 minut es, and 3 and 12 hours after thrombolysis. By use of receiver operating cha racteristic analysis, thresholds were derived to predict 30-day mortality w ith at least 95% negative predictive value. Results Ninety minutes after thrombolysis myoglobin was superior to troponi n-l or CK-MB in identifying patients at low risk for mortality. The 30-day mortality for 12-hour myoglobin less than or equal to 239 ng/ml was 1.4% co mpared with 9.1% for levels > 239 ng/ml (P < .001), For 12-hour troponin-1 (threshold 81.5 ng/ml], mortality was 1.9% versus 6.6% (P =.001) if above t hreshold; similarly for CK-MB at 12 hours (threshold 191 ng/ml) it was 3.3% versus 7.9% (P =.02). Multivariate analysis of baseline and posttreatment cardiac markers, age, sex, infarct artery location, and 90-minute TIMI flow grade identified only 12-hour myoglobin among the cardiac markers as indep endently predicting a low 30-day mortality (odds ratio 0.11, 95% confidence interval 0.02-0.50, P < .004). Conclusion serum cardiac markers can identi fy greater than two thirds of patients at low risk For 30-day mortality. A low 12-hour myoglobin level (1239 ng/ml in this substudy) identifies such p atients at low risk and could potentially assist in early risk stratificati on and triage after ST-segment elevation myocardial infarction.