Relation between high-sensitivity troponin i serum levels and myocardial ischemia in patients with suspected chronic coronary syndrome: the RESET-MI study

Abstract Background Although the detection of a rise and/or fall pattern of cardiac troponin (cTn) serum levels in presence of a clinical context of acute myocardial ischemia, represents the main criterion for the diagnosis of acute myocardial infarction (AMI), troponins may increase in various conditions of myocardial injury different from ischemic myocardial necrosis or simply following myocardial ischemia, in the absence of cell necrosis. Some studies found that troponins also increase after physical exertion and other types of stressful stimuli in the absence of obstructive CAD and myocardial ischemia. No previous study, however, investigated the relation between cTn serum levels and the extent of myocardial ischemia in patients with a suspect of CCS. Methods We prospectively enrolled consecutive patients undergoing an elective stress myocardial perfusion scintigraphy (MPS) because of a clinical suspicion of obstructive coronary artery disease (CAD). Patients were divided into 3 groups based on the evidence and degree of stress-induced MI at MPS: 1) group 1, no MI (≤4%); 2) group 2, mild MI (5-10%); 3) group 3, moderate-to-severe MI (≥10%). High sensitivity (hs)-cTnI was measured immediately before (T0) and 1 hour (T1) and 4 hours (T2) after the stress test. A successive evaluation of patients was performed at 24 months. Results One-hundred consecutive patients (64 males; age 65.5±9.5 years) were enrolled in the study. Serum hs-cTnI concentrations significantly increased after MPS, compared to baseline, in the whole population, from (median, interquartile range) 3.9 (2.5-6.1) ng/L at T0, to 4.2 (2.8-7.3) ng/L at T1 (p<0.001) and 6.7 (3.8-14.1) ng/L at T2 (p<0.001 vs. both T0 and T1). The increase in hs-cTnI did not significantly differ between the 3 groups (p=0.35). Heart rate achieved during the test was the strongest determinant of cTnI increase (p < 0.001). No major adverse cardiac event occurred during follow-up. Only 12 patients (12%) underwent coronary revascularization, whereas angina episodes were reported by 23 patients (23%). There were no significant differences in hs-cTnI increase after the stress test between patients with clinical events at follow-up compared with those who did not report myocardial revascularization or angina recurrence (p=0.21). Conclusions In patients with suspected CAD, stress MPS induces an increase of cTnI that is independent of the induction and the extent of myocardial ischemia and is mainly related to myocardial work, as indicated by HR achieved during the test.