High-sensitivity cardiac troponin I after coronary artery bypass grafting for post-operative decision-making

Aims: Current troponin cut-offs suggested for the post-operative workup of patients following coronary artery bypass graft (CABG) surgery are based on studies using non-high-sensitive troponin assays or are arbitrarily chosen. We aimed to identify an optimal cut-off and timing for a proprietary high-sensitivity cardiac troponin I (hs-cTnI) assay to facilitate post-operative clinical decision-making. Methods and results: We performed a retrospective analysis of all patients undergoing elective isolated CABG at our centre between January 2013 and May 2019. Of 4684 consecutive patients, 161 patients (3.48%) underwent invasive coronary angiography after surgery, of whom 86 patients (53.4%) underwent repeat revascularization. We found an optimal cut-off value for peak hs-cTnI of >13 000 ng/L [>500× the upper reference limit (URL)] to be significantly associated with repeat revascularization within 48 h after surgery, which was internally validated through random repeated sampling with 1000 iterations. The same cut-off also predicted 30-day major adverse cardiovascular events and all-cause mortality after a median follow-up of 3.1 years, which was validated in an external cohort. A decision tree analysis of serial hs-cTnI measurements showed no added benefit of hs-cTnI measurements in patients with electrocardiographic or echocardiographic abnormalities or haemodynamic instability. Likewise, early post-operative hs-cTnI elevations had a low yield for clinical decision-making and only later elevations (at 12-16 h post-operatively) using a threshold of 8000 ng/L (307× URL) were significantly associated with repeat revascularization with an area under the curve of 0.92 (95% confidence interval 0.88-0.95). Conclusion: Our data suggest that for hs-cTnI, higher cut-offs than currently recommended should be used in the post-operative management of patients following CABG. Key question: To describe the kinetics of high-sensitivity cardiac troponin I (hs-cTnI) after elective coronary artery bypass graft (CABG) surgery and assess which hs-cTnI cut-offs correlate with clinically meaningful findings. Key finding: High-sensitivity cardiac troponin I levels determined 12-16 h after surgery with a cut-off of 8000 ng/L (307× upper reference limit) correlated best with a decision to repeat revascularization, while at earlier time-points, clinical decision should rather be based on electrocardiogram (ECG), echocardiographic, and haemodynamic criteria. Take-home message: High-sensitivity cardiac troponin I aids decision-making when determined 12 h or later after CABG utilizing higher cut-offs than currently recommended, at earlier time-points workup should be based on ECG, echo, and haemodynamic criteria.