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.