The prognostic value of serum troponin T in unstable angina.

BACKGROUND. Cardiac troponin T is a regulatory contractile protein not normally found in blood. Its detection in the circulation has been shown to be a sensitive and specific marker for myocardial cell damage. We used a newly developed enzyme immunoassay for troponin T to determine whether its presence in the serum of patients with unstable angina was a prognostic indicator. METHODS. We screened 109 patients with unstable angina (25 with accelerated or subacute angina and 84 with acute angina at rest) for serum creatine kinase activity, creatine kinase isoenzyme MB activity, and troponin T every eight hours for two days after admission to the hospital. The outcomes of interest during the hospitalization were death and myocardial infarction. RESULTS. Troponin T was detected (range, 0.20 to 3.64 micrograms per liter; mean, 0.78; median, 0.50) in the serum of 33 of the 84 patients (39 percent) with acute angina at rest. Only three of these patients had elevated creatine kinase MB activity (two were positive for troponin T, and one was negative). Of the 33 patients who were positive for troponin T, 10 (30 percent) had myocardial infarction (3 after coronary-artery bypass surgery), and 5 of these died during hospitalization. In contrast, only 1 of the 51 patients with angina at rest who were negative for troponin T had an acute myocardial infarction (P less than 0.001), and this patient died (P = 0.03). Thus, 10 of the 11 patients with myocardial infarctions had detectable levels of troponin T; only 1 had elevated creatine kinase MB activity. Troponin T was not detected in any of the 25 patients with accelerated or subacute angina, and none of these patients died. CONCLUSIONS. Cardiac troponin T in serum appears to be a more sensitive indicator of myocardial-cell injury than serum creatine kinase MB activity, and its detection in the circulation may be a useful prognostic indicator in patients with unstable angina.     

Coronary angiographic findings in patients with clinical unstable angina according to cardiac troponin I and T concentrations in serum

CONTEXT: Elevated cardiac troponin levels have been reported to identify unstable angina patients at high risk. OBJECTIVE: To examine the relation of cardiac troponin I (cTnI) and cardiac troponin T (cTnT) levels to findings of coronary angiography in these patients. METHODS: Samples for troponin estimation were taken every 4 hours throughout the first 48 hours after admission before angiography in 34 patients with primary unstable angina. Patients were considered to be troponin positive if the marker was increased (>0.04 microg/L for cTnT and >0.03 microg/L for cTnI) in at least one sample collected. RESULTS: An increased troponin (I or T) concentration was documented in 14 patients (41.2%). Twelve patients (35.3%) had elevations of both markers, whereas the remaining 2 patients had elevations of cTnI or cTnT alone. Patients with or without increased troponin levels did not differ with respect to degree of coronary disease at angiography. However, patients with elevated troponin concentrations had more complex lesion characteristics. In 69% of patients with increased cTnI levels and in 77% of patients with increased cTnT levels, type B2 or C lesions were documented with presence of ulcerated plaques and thrombus formation. In contrast, only 23% of the patients with elevated cTnI or cTnT levels had type A lesions compared with 71% of patients with negative troponin concentrations. CONCLUSIONS: Patients with unstable angina who have significant release of cTnI and/or cTnT have evidence of more complex lesions on coronary angiography, supporting the hypothesis that both troponins might be used without distinction as surrogate markers for microembolization from thrombus formation on a disrupted plaque.