Determinants and Prognosis of Myocardial Damage After Coronary Artery Bypass Grafting

Background: Myocardial infarction remains a devastating complication after coronary revascularization. Although electrocardiography (ECG) and echocardiography suggest transmural infarction, myocardial damage and the quality of myocardial protection are not recognized unless troponin I (TnI) is assessed. Determinants and prognosis of TnI elevation after coronary artery bypass grafting (CABG) were evaluated.

Methods: Data of 776 consecutive patients undergoing CABG between January 2002 and January 2004 were prospectively exposed to univariate and multivariate analysis. We evaluated the prognosis of patients with all the ECG, echocardiographic, and biochemical criteria for acute myocardial infarction and that of patients with only TnI elevation. Twelve-month follow-up survival and freedom from cardiac events (FCE) were accomplished.

Results: Troponin I greater than 3.1 mug/L at 12 hours was detected in 6.9% of the population, and correlated with lower in-hospital (p < 0.001) and follow-up survival (p = 0.00001), and lower FCE (p = 0.0009). Twenty-one (38.8%) of these fulfilled ECG-echocardiographic criteria (p = 0.05), demonstrating higher TnI values at 12 (p = 0.001), 24 (p = 0.01), 48 (p = 0.01), and 72 (p = 0.04) hours, prolonged ventilation time (p = 0.001), higher in hospital mortality (p = 0.003), lower follow-up survival (p = 0.023), and lower FCE (p = 0.0084). A EuroSCORE greater than 6, ongoing unstable angina, aortic cross-clamp time greater than 90 minutes, cardiopulmonary bypass time greater than 180 minutes, incomplete revascularization, and intraoperative intraaortic balloon pump were independent predictors of myocardial damage (MD) at multivariate analysis. Combined antegrade and retrograde cardioplegia and postoperative enoximone infusion were associated with a lower TnI elevation.

Cconclusions: Troponin I greater than 3.1 mug/L at 12 hours defines perioperative MD. Associated ECG-echocardiographic criteria indicate acute myocardial infarction and anticipate a worse outcome. Identification of predictors for MD is important to develop preventative strategies, as antegrade plus retrograde cardioplegia and enoximone infusion.