Source: Aviles RJ. Troponin-T levels in patients with acute coronary syndromes, with and without renal dysfunction. N Engl J Med 2002;346:2047-2052.
The authors present a secondary analysis of data from the GUSTO-IV study, which was intended to assess the value of abciximab in patients with acute coronary syndrome (ACS). Patients were enrolled if they had one or more episodes of angina while at rest that lasted at least five minutes and were associated with new ST-segment depression, and/or had an abnormal cardiac troponin-T (cTn-T) value. Serum creatinine was measured and creatinine clearance was calculated. The primary endpoint was death and/or myocardial infarction (MI) within 30 days of enrollment. The risks of reaching the endpoint were adjusted for confounding variables including age, electrocardiogram (ECG) abnormalities, history of coronary disease, and diabetes.
Of 7800 patients enrolled, 7033 were fully evaluable. cTn-T was abnormally elevated (> 0.1 ng/dL) in 52%. Among patients with creatinine clearance values below 58 mL/min, an elevated cTn-T was predictive of increased risk of MI or death, with an adjusted odds ratio of 2.5 (95% CI, 1.8-3.3). This was similar to the risk among patients with higher creatinine clearances, who had an adjusted odds ratio of 1.7 (95% CI, 1.3-2.2). Elevation of cTn-T proved independently predictive of risk across the entire spectrum of renal function. The authors conclude that cTn-T levels are useful prognostic markers in patients with ACS regardless of renal function.
Commentary by David J. Karras, MD, FACEP
Cardiac troponins are known to be excellent markers of MI and appear to detect microinfarctions better than creatine kinase with muscle and brain subunits (CK-MB). In patients with ACS, therefore, elevations in cardiac troponin-I and cTn-T provide valuable independent prognostic information regarding the risk of short-term adverse cardiac outcomes, even in the absence of frank MI.1 Because troponins are cleared by the kidneys, however, the utility of the test in patients with underlying renal insufficiency has been questioned. The authors of this powerful study have demonstrated that abnormal elevation of cTn-T yields the same prognostic information in patients with renal impairment as it does in patients with normal renal function.
Reference
1. Antman EM. Decision making with cardiac troponin tests. N Engl J Med 2002;346:2079-2082.
Dr. Karras, Associate Professor of Emergency Medicine, Department of Emergency Medicine Temple University School of Medicine, Director of Emergency Medicine Research, Temple University Hospital, Philadelphia, PA, is on the Editorial Board of Emergency Medicine Alert.
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