Composition of cardiac troponin release differs after marathon running and myocardial infarction.

Objectives: Elevations of cardiac troponin T (cTnT) levels are common after strenuous exercise. We assessed whether the composition of cTnT release after marathon race differs from that of acute myocardial infarction (MI).
Methods: Troponin composition was analysed in plasma samples taken from 45 runners after marathon race and from 84 patients with type 1 MI. The concentration of long cTnT (intact and mildly fragmented cTnT) was measured with a novel upconversion luminescence immunoassay, total cTnT with a commercial high-sensitivity cTnT assay, and the ratio of long to total cTnT (troponin ratio) was determined as a measure of troponin fragmentation.
Results: Total cTnT exceeded the upper reference limit (>14 ng/L) in 37 (82%) runners. Troponin ratio was lower in runners ((IQR) 0.17 (0.11-0.24) vs 0.62 (0.29-0.96), p<0.001). With increasing troponin release the troponin ratio decreased (r=-0.497, p<0.001) in marathon runners and the concentration of long cTnT remained in all runners below 8.4 ng/L. In contrast to marathon runners, troponin ratio increased (r=0.565, p<0.001) with the increase of cTnT release in patients with MI. The median total and long cTnT concentrations were lower in marathon runners than in patients with MI (25 ng/L vs 835 ng/L and 4.1 vs 385 ng/L, p<0.001 for both).
Conclusion: In contrast to type 1 MI, only a small fraction of circulating cTnT exists as intact cTnT or long molecular forms after strenuous exercise and the difference in troponin composition is more pronounced in runners with higher troponin release.
Trial Registration Number: NCT06000930.
Competing Interests: Competing interests: JA: research grants from the Finnish Foundation for Cardiovascular Research and Clinical Research Fund of Turku University Hospital, Turku, Finland. Lectures for Astra Zeneca, Bayer, Boehringer Ingelheim, pending patent application WO2023187258 (A1) - ASSAY FOR LONG FORMS OF CARDIAC TROPONIN T. TP: lectures for Astra Zeneca. TH: lectures for AstraZeneca, Astellas and GSK, pending patent application WO2023187258 (A1) - ASSAY FOR LONG FORMS OF CARDIAC TROPONIN T. TV: pending patent application WO2023187258 (A1) - ASSAY FOR LONG FORMS OF CARDIAC TROPONIN T. SS: none. TT: none. AL-P: research grants from the Finnish Society of Clinical Chemistry. H-MP: lectures for Roche. KT: research grants from The Finnish Foundation for Cardiovascular Research, The Finnish Medical Foundation, The Finnish Foundation for Alcohol Studies and the Finnish State Research Funding. SJ: lectures for Amgen, Boehringer Ingelheim, BMS Pfizer. OJH: none. SW: research grants from the Finnish Society of Clinical Chemistry, the Finnish Foundation for Cardiovascular Research, the Turku University Foundation and the Varsinais-Suomi Regional Fund of the Finnish Cultural Foundation, and the Finnish Foundation for Cardiovascular Research. Research funding from Business Finland, official Finnish government agency for trade and investment promotion, innovation funding, travel promotion and talent attraction. Pending patent application WO2023187258 (A1) - ASSAY FOR LONG FORMS OF CARDIAC TROPONIN T.
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