Which troponometric best predicts midterm outcome after coronary artery bypass graft surgery?

Abstract

Various troponin I measurements (troponometrics) have been used as surrogate markers of patient outcome after coronary artery bypass grafting (CABG). Our aim was to define the postoperative troponometric best able to predict in-hospital and late mortality. In 440 patients (seen from January 2000 to September 2004) undergoing isolated on-pump CABG with standardized anesthesia, perfusion, cardioplegia, and postoperative care, we followed all-cause mortality (census June 2009, 100% complete). Subjects underwent troponin I (cardiac troponin I [cTnI]) estimation at baseline and 6, 12, 24, 48, and 72 hours postoperatively, and individual time-point cTnI (T6, T12, T24, T48, T72), peak cTnI (Cmax), increase in cTnI between 6 and 12 hours (T↑6-12) and 6 and 24 hours (T↑6-24), cumulative area under the curve cTnI (CAUC24, CAUC48, and CAUC72), and cTnI≥13 ng·mL(-1) at any time point were each analyzed using univariate and multivariable Cox models to identify the probability of in-hospital and late death. Logistic EuroSCOREs and calculated creatinine clearance (CrCl) were also included. The Akaike information criterion (AIC) was used to determine goodness of fit. There were 62 of 440 deaths after a median (interquartile range) follow-up period of 7.0 (5.7 to 8.1) years. Univariate Cox analysis demonstrated T12, T24, T48, T72, T↑6-12, T↑6-24, standardized CAUC24, CAUC48, and CAUC72 each to be predictors of midterm mortality. On Cox multivariable analysis in models incorporating both logistic EuroSCOREs and CrCl, both T72 (hazard ratio [HR], 95% confidence interval [CI], 1.10 [1.06 to 1.14]; p<0.001) and CAUC72 (1.45 [1.26 to 1.62], p<0.001) were identified as independent predictors of mortality. Of these, CAUC72 was superior based on the lowest AIC. In myocardial protection studies, serial troponin I data should be collected until 72 hours postoperatively to calculate CAUC72, as this troponometric best predicts midterm mortality.