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

Abstract

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.

Keywords: Coronary artery bypass grafting; High-sensitivity cardiac troponin; Invasive coronary angiography; Post-operative myocardial infarction.

Graphical abstract

Figure 1

Study flowchart.

Figure 2

Perioperative kinetics of high-sensitivity cardiac troponin I: (A) perioperative kinetics of high-sensitivity cardiac troponin I in the overall collective; (B) perioperative kinetics of high-sensitivity cardiac troponin I according to post-operative management; (C) perioperative kinetics of high-sensitivity cardiac troponin I according to invasive coronary angiography indication.

Figure 3

Proportion analysis of the association between high-sensitivity cardiac troponin I levels and outcomes: (A) repeat invasive coronary angiography in the overall study cohort; (B) new vessel occlusion on invasive coronary angiography; (C) long-term all-cause mortality. URL, the 99th percentile upper reference limit (26 ng/L). Random_Exp and Random_Chi are randomly created cut-offs created following a Monte-Carlo-based approach utilizing an exponential and a χ  ² distributions, respectively. The proportion for >500×URL was significantly higher than other thresholds in all three categories (P < 0.001 for all comparisons). (Details on the methods are provided in the Supplementary material online, analysis of methods.)

Figure 4

Receiver-operating characteristics analysis of high-sensitivity cardiac troponin I at predefined time-points post-operatively for the association with repeat revascularization after surgery. ROC, receiver-operating characteristics; AUC, area under the curve; T4, high-sensitivity cardiac troponin I levels between 0 and 4 h post-operatively; T8, high-sensitivity cardiac troponin I levels between 4 and 8 h post-operatively; T12, high-sensitivity cardiac troponin I levels between 8 and 12 h post-operatively; T16, high-sensitivity cardiac troponin I levels between 12 and 16 h post-operatively; T20, high-sensitivity cardiac troponin I levels between 16 and 20 h post-operatively; T24, high-sensitivity cardiac troponin I levels between 20 and 24 h post-operatively.

Figure 5

Kaplan–Meier survival curves according to peak high-sensitivity cardiac troponin I levels within 48 h after surgery. Kaplan–Meier curves from in multivariable Cox regression analysis (P-values were adjusted for: age, EuroSCORE II, diabetes, peripheral arterial disease, and left ventricular ejection fraction at discharge).