Dr. Vipin BhayanaAssociate Professor, Clinical Biochemist (London Health Sciences Centre)
Phone: 519.685.8500, ext. 35775
Acute Myocardial Infarction and Immunodiagnostics
Early and accurate identification and confirmation of acute myocardial infarction (AMI) is important for treatment and early triage of patients from the emergency department (ED). Most physicians in the ED rely heavily on electrocardiography (ECG) results, even though about half of all AMI patients have nondiagnostic ECGs. To alleviate this problem, several biochemical markers have been used for the early diagnosis of AMI.
Of the commercially available assays, myoglobin and isoforms of creatine kinase-2 (CK; EC220.127.116.11) are regarded as the earliest markers; however, the cardiac specificity of both is questionable. CK-2 mass is, at present, widely used in combination with total CK. Both CK and CK-2 mass have poor sensitivity in the early stages of AMI, and false positives are found in patients with skeletal muscle damage.
Cardiac troponin T, in contrast, has been reported as the most specific biochemical marker of AMI. The initial increases of troponin T after AMI is similar to that of CK-2 mass, while troponin T remains elevated for as long as 10 days after AMI and CK-2 mass returns to baseline within 2 days. Most early investigations showed almost absolute specificity of troponin T for cardiac damage. Many other cardiac markers have surfaced within the last few years, but none of them is being extensively used in the routine clinical laboratory.