Determination of cardiac troponin I forms in the blood of patients with unstable angina pectoris

OBJECTIVE: To determine the predominant form in which cardiac troponin I circulates in the bloodstream of unstable angina patients. DESIGN AND METHODS: The cardiac troponin I forms released in the bloodstream of 25 patients suffering from unstable angina were examined by using three immunoenzymatic assays: the total cTnI assay for detection of free and complexed cTnI, the IC-TIC assay for detection of the IC and TIC troponin complexes, and the IT-TIC assay for detection of the IT and TIC troponin complexes. RESULTS: Approximately 60% of patients with unstable angina had at least one positive value in the total cTnI assay or in the IC-TIC assay. Our results demonstrated that the predominant cardiac troponin I form circulating in the bloodstream of patients with unstable angina was the IC complex. Free cTnI, IT, and/or TIC forms were seldom found, the frequency of IT and/or TIC complexes being higher than that observed previously in patients with acute myocardial infarction. CONCLUSIONS: The release pattern of cTnI in patients suffering from unstable angina is similar to that previously observed in patients with acute myocardial infarction, i.e., a predominance of the IC complex.