Timing and threshold of high sensitive troponin T measurement for the prediction of mortality after cardiac surgery: a retrospective cohort analysis

Background High sensitive cardiac troponin T (hsTnT) is a widely used biomarker of myocardial injury. Along with other high sensitive troponins, HsTnT can predict mortality in both cardiac and non-cardiac surgery. The aim of this study was to determine the association between hsTnT serum elevations in the immediate postoperative period until 120 h after cardiac surgery and the occurrence of in-hospital mortality compared to the Simplified Acute Physiology Score 3 (SAPS3). Additionally, we identified an ideal hsTnT serum threshold to predict in-hospital mortality.Methods We performed a retrospective single-institutional cohort analysis of 2179 patients undergoing cardiac surgery with cardiopulmonary bypass from 2013 to 2021. Logistic regression analysis was used to investigate an association of hsTnT at various time points and in-hospital mortality. The model was adjusted for relevant covariates including SAPS3, lactate and administered norepinephrine dosage. ROC analysis was performed to estimate the accuracy to predict mortality by serum hsTnT concentrations. This prediction was compared to the SAPS3 score. An ideal cutoff of hsTnT concentration was calculated by means of Youden index.Results In total 7576 troponins were measured at the predefined timepoints. 100 (4.59%) patients died during the hospital stay. The fourth hsTnT on d3 (at 96-120 h postoperatively) showed the highest association with in-hospital death (OR 1.56; 95% CI (1.39-1.76); p < 0.001). This finding persisted after multivariable adjustment (aOR 1.34; 95% CI (1.18-1.53); p < 0.001). In contrast, the third hsTnT on d2 (at 48-72 h postoperatively) showed the best discrimination for in-hospital mortality (AUC 82.75%; 95% CI (0.77-0.89). The prediction by the third hsTnT was comparable to the in-hospital mortality prediction by SAPS3 (AUC 79.36%; 95% CI (0.73-0.85); p = 0.056). The optimal cutoff for the third hsTnT was calculated to be 1264 ng/L (Sensitivity 0.62; Specificity 0.88).Conclusion Elevated hsTnT after cardiac surgery was associated with an increased risk of in-hospital mortality. HsTnT measured on postoperative day 2 and 3 were most accurate to predict in-hospital mortality. The prediction of in-hospital mortality using hsTNT is comparable to mortality prediction using the SAPS3 score. HsTnT serum levels currently recommended to establish clinically important periprocedural myocardial injury are lower than thresholds identified in this study.