Prevalence of angiographically significant stenosis in patients with chest pain and an elevated troponin I level and normal creatine kinase and creatine kinase-MB levels

The traditional gold standard for the detection of myocardial cell necrosis has been cretine kinase (CK) and its MB isoenzyme (CK-MB); however, this has been limited by its lack of specificity in certain patient subsets, such as active marathon runners and those with skeletal myopathies, chronic renal failure, and hypothyroidism.(1-4) More specific immunoassays have been developed that measure cardiac troponin T and cardiac troponin I, the proteins that regulate the calcium-dependent interactions between actin and myosin in the cardiac myocyte.(5,6) Troponin I is a highly sensitive and specific serum marker for myocardial damage that has been shown to be helpful in distinguishing whether elevations in CK and CK-MB are due to myocardial or skeletal muscle injury.(7,8) Furthermore, several studies have shown that troponin I has sensitivity comparable to and potentially superior to CK-MB for the diagnosis of myocardial infarction with persistent elevations up to 1 week.(9-11) In patients who have an acute coronary syndrome, an elevated troponin I has been shown to be an independent risk factor for predicting mortality.(12,13) However, the clinical significance and coronary anatomy of patients with elevated troponin I and normal CK and CK-MB levels has not been clearly established. We hypothesized that most of these patients would have evidence of significant narrowing of their coronary arteries.