Cardiac Troponin Fragmentation After Heavy Physical Exercise The MaraCat2 Study

Abstract

AbstractBackgroundElevations of commercial cardiac troponin T (total cTnT) levels are common after strenuous exercise, but there is limited information on whether the troponin composition differs from myocardial infarction (MI).MethodsTroponin composition was analyzed in heparin plasma samples taken from 45 runners <1 h after marathon race and from 45 patients with Type 1 MI <12 h after the pain onset. The concentration of long molecular forms of cTnT (long cTnT) was measured with a novel upconversion luminescence assay, total cTnT was measured with a commercial high-sensitivity cTnT assay, and the ratio of long to total cTnT (troponin ratio) was determined.ResultsTotal cTnT exceeded the upper reference limit (>14 ng/l) in 37 (82%) runners. The median total and long cTnT concentrations and the troponin ratio were higher (113 ng/l vs. 25 ng/l, 57 ng/l vs. 4.1 ng/l, and 0.36 vs. 0.17, respectively) in patients with MI than in marathon runners (p <0.001 for all comparisons). Troponin ratio decreased (r = -0.497, p <0.001) in marathon runners and increased (r = 0.466, p = 0.001) in patients with MI with increasing troponin release. In the receiver operating characteristics curve analyses of all subjects with cTnT release >14ng/l and those with 15-100 ng/l, long cTnT showed good predictive power with the area under the curve 0.969 (CI95% 0.939-1.000) and 0.937 (95% CI, 0.877–0.996) in discriminating marathon runners from MI patients. The respective values for total cTnT were 0.892 (CI95% 0.823-0.960) and 0.778 (95% CI, 0.656–0.901).ConclusionsIn contrast to Type 1 MI, after strenuous exercise only a small fraction of circulating cTnT exists as intact cTnT or long molecular fragments. The difference in troponin composition could be of diagnostic value when evaluating post-exercise cTnT elevations in subjects with chest complaints.RegistrationURL:https://www.clinicaltrials.gov; Unique identifier:NCT06000930Clinical PerspectiveWhat Is New?Short cardiac troponin T (cTnT) fragments were the predominant form of cTnT release after marathon race among 45 runners in contrast to 45 patients with Type 1 myocardial infarction (MI) where intact cTnT and longer fragments are more commonly found in the circulation during the early hours after the attack also in patients with comparable troponin levels.The proportion of short cTnT components decreased (r = -0.497, p <0.001) in marathon runners and increased (r = 0.466, p = 0.001) in patients with MI with increasing troponin release.What Are the Clinical Implications?The principle of the novel immunoassay could be applied on automated platforms to allow implementation in clinical care and separate benign cTnT elevations after strenuous exercise from those of acute MI in a single sample with better accuracy than the commercial high-sensitivity cTnT test.