To assess the clinical significance of cardiac troponin elevation after coronary artery bypass grafting, investigators studied data on 847 consecutive patients who underwent isolated CABG at a single U.S. institution. The median peak troponin T (TnT) level obtained within 24 hours after surgery was 1.08 ng/mL. TnT levels were 0.15 ng/mL in 96.6% of patients, and 36.7% had a TnT of 1.60 ng/mL. However, new Q waves or left bundle-branch block occurred in only 17 patients (2%) on the day after surgery.

Postoperative TnT levels correlated directly and significantly with duration of intensive care unit stay, hours of postoperative mechanical ventilation, and duration of hospital stay. The median peak TnT level during the first 24 hours was significantly higher in the nine patients who died within 30 days after CABG than in survivors (3.41 ng/mL vs. 1.07 ng/mL). Heart failure or death occurred in 18 patients; the median TnT level in this group was significantly higher than in patients without either outcome. In a multivariate analysis adjusted for the Society of Thoracic Surgeons risk score, TnT values significantly predicted postoperative death, death or heart failure, death or vasopressor treatment, and the composite of death, heart failure, and vasopressor treatment.

Comment: Elevated troponin T concentrations are seen in nearly all patients after CABG. These results suggest that a marked TnT elevation soon after bypass surgery does indicate a poor prognosis and that troponin testing, although perhaps unnecessary in all patients after CABG, is useful for assessing the clinical implications of delayed recovery. Efforts are warranted to identify — and, ultimately, to prevent or treat — the causes of TnT release during and after bypass surgery.

— Joel M. Gore, MD

Published in Journal Watch Cardiology September 30, 2009