Cardiac troponin I for stratification of early outcomes and the efficacy of enoxaparin in unstable angina: a TIMI-11B substudy

Objectives We sought to evaluate cardiac troponin I (cTnI) for predicting early clinical outcomes and the efficacy of enoxaparin among patients with non–ST segment elevation acute coronary syndrome (ACS) and negative creatine kinase, MB fraction (CK-MB) levels. Background Cardiac TnI identifies patients with unstable angina who are at higher risk of death or myocardial infarction (MI) by 30 days. The utility of cTnI for predicting very early clinical events, including recurrent ischemia, and the efficacy of enoxaparin are not yet established. Methods At baseline and 12 h to 24 h after enrollment in the Thrombolysis in Myocardial Infarction (TIMI)-11B trial, samples were collected for cTnI determination. Results Among 359 patients with negative serial CK-MB values, 50.1% had a cTnI result ≥0.1 ng/ml within the first 24 h. Patients with elevated cTnI were at higher risk of death or MI at 48 h (3.9 vs. 0%, P = 0.01) and 14 days (13.9 vs. 2.2%, p < 0.0001). Elevated cTnI also correlated with higher risk of recurrent ischemia requiring urgent revascularization by 48 h (10.0 vs. 1.7%, P = 0.001) and 14 days (20.6 vs. 5.6%, p ≤ 0.0001). Enoxaparin had a greater benefit among patients with elevated vs. normal cTnI (p = 0.03), achieving a 47% reduction in the risk of death, MI or urgent revascularization by 14 days in cTnI-positive patients (p = 0.007). Conclusions Elevation of cTnI among patients with non–ST segment elevation ACS and negative levels of CK-MB identifies those at higher risk for very early adverse outcomes, including severe recurrent ischemia. Treatment with enoxaparin reduces the risk associated with elevated cTnI.