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Early Diagnosis of Acute Myocardial Infarction in Patients With Pre-Existing Coronary Artery Disease Using More Sensitive Cardiac Troponin Assays
Study Questions:
What is the impact of high-sensitivity troponin (hs-Tn) measurements on the diagnosis of acute myocardial infarction (AMI) in patients with pre-existing coronary artery disease (CAD) presenting with chest pain?
Methods:
The diagnostic accuracy of three sensitive cardiac Tn (cTn) assays was tested in 1,098 patients presenting with symptoms suggestive of AMI, of whom 37% had pre-existing CAD.
Results:
AMI was determined to be the final diagnosis in 19% of CAD patients. In those without AMI, baseline cTn levels were elevated above the 99th percentile with Roche hs-cTnT in 40%, with Siemens TnI-Ultra in 15%, and Abbott-Architect cTnI in 13%. The diagnostic accuracy at presentation was significantly greater for the sensitive cTn assays compared with the standard assay (area under the curve [AUC] for Roche hs-cTnT, 0.92; Siemens cTnI-Ultra, 0.94; and Abbott-Architect cTnI, 0.93 vs. AUC for the standard assay, 0.87; p < 0.01 for all comparisons). Elevated levels of cTn measured with the sensitive assays predicted mortality irrespective of pre-existing CAD, age, sex, and cardiovascular risk factors.
Conclusions:
The authors concluded that sensitive cTn assays have high-diagnostic accuracy in CAD patients. Mild elevations are common in non-AMI patients, and test-specific optimal cut-off levels tend to be higher in CAD patients than in patients without history of CAD. Sensitive cTn assays also retain prognostic value.
Perspective:
The speed and accuracy of managing chest pain patients may be improved with higher-sensitivity cTn assays, as this and previous studies imply. However, 40% of patients with CAD deemed not to have AMI in this study showed cTn levels above the 99th percentile using the most sensitive assay. Determination of the optimal cut-off values and the net clinical benefit (outcomes and cost savings) of these assays will need to be addressed in future studies. The long-term prognostic implications of elevated cTn, even in patients without acute coronary syndrome, are particularly interesting, and may be useful in guiding preventive therapies. Further study is required.
Keywords: Coronary Artery Disease, Acute Coronary Syndrome, Biomarkers, Early Diagnosis, Troponin
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