Composition of Troponin Release After Elective On-Pump and Off-Pump Cardiac Surgery.

BACKGROUND: Troponin levels are almost always elevated after cardiac surgery. We assessed whether measurement of intact and mildly fragmented cTnT (cardiac troponin T) forms (long cTnT) analyzed using a novel immunoassay could provide incremental value in the evaluation of myocardial injury after cardiac surgery. METHODS: In 149 patients undergoing elective cardiac surgery, high-sensitivity-cTnT and long cTnT were measured preoperatively and at 3 to 6 hours, 1 day, and 3 to 7 days postoperatively. RESULTS: No patient had a clinical diagnosis of perioperative myocardial infarction. Peak high-sensitivity cTnT exceeded 70× the upper reference limit (URL) in 34 (23%) patients, with a median peak concentration of 636 ng/L. For long cTnT, the median peak concentration was 542 (interquartile range, 250-880) ng/L and 79 (53%) patients exceeded 70× URL. Long cTnT levels declined rapidly from the peak to postoperative days 3 to 7 (median 11 [7-17] ng/L) and exceeded 10× URL in only 1 patient (0.7%) with a new left bundle-branch block. In contrast, high-sensitivity cTnT remained elevated, exceeding 10× URL in 57% of patients at postoperative days 3 to 7. Peak release of long cTnT correlated with the duration of cardiopulmonary bypass (r=0.339, P<0.001) and was higher in on-pump surgery than in off-pump surgery (median 603 ng/L versus 23 ng/L, P<0.001). CONCLUSIONS: Long cTnT constitutes the main component of early troponin release after on-pump surgery while smaller molecules dominate after off-pump surgery. The rapid decrease in long cTnT concentrations may offer diagnostic value for myocardial infarction as early as 24 hours after surgery, when high-sensitivity cTnT concentrations still remain elevated. REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifier: NCT04465591.