Prognostic Value of Early Postoperative Troponin T in Patients Undergoing Coronary Artery Bypass Grafting

Abstract

Background: Cardiac troponin T (cTnT) is elevated after coronary artery bypass grafting surgery. The aim of this study was to determine the association between cTnT elevations between 6 and 12 hours after coronary artery bypass grafting and in-hospital outcome.

Methods and results: We prospectively studied 1722 patients undergoing isolated coronary artery bypass grafting. We assessed the association between conventional cTnT (749 patients) and high-sensitivity cTnT (hs-cTnT; 973 patients) 6 to 12 hours postoperatively with in-hospital major adverse cardiac or cerebrovascular events (MACCE), a composite of all-cause death, myocardial infarction, or stroke. The prespecified secondary outcome was a safety composite of MACCE, resuscitation, intensive care unit readmission or admission ≥48 hours, inotrope or vasopressor use ≥24 hours, or new-onset renal insufficiency. Among patients with a conventional cTnT measurement, 92 experienced a MACCE (12%) and 146 experienced a safety composite event (19%). Likewise, for hs-cTnT, 114 experienced a MACCE (12%) and 153 experienced a safety composite event (16%). Compared with cTnT ≤200 ng/L, each 200-ng/L increment in cTnT was associated with a monotonous increase in the odds of MACCE and the safety composite outcome. Conventional and hs-cTnT demonstrated moderate discrimination for MACCE (areas under the fitted receiver operating characteristics curve, 0.72 and 0.77 for conventional and hs-cTnT, respectively) and the safety composite outcome (areas under the fitted receiver operating characteristics curve, 0.66 and 0.74 for conventional and hs-cTnT, respectively) and resulted in improved prognostic performance when added to the EuroSCORE. At a cutoff of 800 ng/L, conventional and hs-cTnT provided clinically relevant power to rule in MACCE and the safety composite outcome.

Conclusions: cTnT levels assessed between 6 and 12 hours after coronary artery bypass grafting identify patients at increased risk of MACCE or other complications.

Keywords: coronary artery bypass graft surgery; prognosis; troponin T.

© 2018 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley.

Figures

Figure 1

Patient flow. The asterisk indicates that 9 patients who underwent coronary artery bypass grafting (CABG) between January 1, 2008, and December 31, 2008, were originally excluded from the development cohort because they had received an ablation or a closure of a patent foramen ovale; therefore, previously published results are based on only 290 analyzed patients.10 cTnT indicates cardiac troponin T; and MI, myocardial infarction.

Figure 2

Distribution of early cardiac troponin T (cTnT) and probability of major adverse cardiac or cerebrovascular events (MACCE). Risk of in‐house MACCE; shaded region represents the distribution of conventional or high‐sensitivity troponin T measured 9 hours after coronary artery bypass grafting surgery. The corresponding figures for the safety composite outcome are shown in Figure S1.

Figure 3

Nomograms of the relation between pretest and posttest probability of major adverse cardiac or cerebrovascular events (MACCE) or the safety composite, by troponin levels. The curves are based on pretest probabilities and fitted likelihood ratios of cardiac troponin T (cTnT) cutoffs for the risk of MACCE (left panels) and the safety composite (right panels) for conventional cTnT (top panels) and hs‐cTnT (bottom panels). Black dashed lines represent the relation between pretest and posttest probabilities, ruling out future events by cTnT levels equal to or smaller than the cutoff on the basis of negative likelihood ratios; black solid lines, the relation between pretest and posttest probabilities, ruling in future events by cTnT levels larger than the cutoff on the basis of positive likelihood ratios. Red and blue lines relate to reading examples described in the text.