Post-operative aspartate aminotransferase levels independently predict mortality after isolated coronary artery bypass grafting

BackgroundSince troponins have become widely available, the roles of other less specific biomarkers for myocardial necrosis following coronary artery bypass grafting (CABG) have been seldom studied. Aspartate aminotransferase (AST) may not only be released from the heart but also from the liver or skeletal muscle. We assessed whether post-operative AST levels were associated with mortality and morbidity after contemporary (CABG).MethodPatients undergoing isolated CABG during July 2010–June 2012 at Auckland City Hospital were included if they had a post-operative AST measurement within 48 h (n = 804 of 818). The prognostic utility of 2 × upper limit of normal of AST (> 90 U/L) pre-specified for adverse outcomes was assessed.ResultsMedian post-operative AST level was 37 U/L (lower quartile 30, upper quartile 48). In multivariable analysis, including baseline characteristics, AST > 90 U/L was independently associated with 30-day mortality (OR 12.0, 95% CI 2.99–47.9, P < 0.001), long-term mortality (OR 12.0, 95% CI 1.69–34.8, P < 0.001) and composite morbidity (OR 3.31, 95% CI 1.56–7.02, P = 0.002). AST as a continuous parameter remained an independent predictor for 30-day and long-term mortality when hs-TnT was adjusted for but not for composite morbidity. Independent predictors of AST > 90 U/L included female sex, unstable angina and operation time.ConclusionIncrease in AST levels within 48 hours of CABG was a strong independent predictor of 30 day mortality. Although AST increase is not specific to myocardial necrosis, it remains useful for prognosis in cardiac surgery.