Role of troponin I, myoglobin, and creatine kinase for the detection of early graft failure following coronary artery bypass grafting.

Abstract

The detection of early graft failure following coronary artery bypass grafting (CABG) enables immediate reintervention and may significantly limit myocardial damage, thus potentially improving outcome. To date, non-invasive indicators of early graft failure following coronary surgery are still of uncertain diagnostic value. In a prospective study, patients following isolated CABG with a postoperative serum cardiac troponin I (cTnI) above 20 ng/ml or significant ECG-changes underwent acute repeat angiography. cTnI, myoglobin (Myo), and creatine kinase (CK) were measured preoperatively and at 1, 6, 12, and 24 h after aortic unclamping. Peak values of cTnI, Myo, CK and isoenzyme CK-MB were determined postoperatively. Receiver operating curves (ROC) for cTnI, Myo and CK/CK-MB were constructed at 6, 12, and 24 h after aortic unclamping to differentiate between patients with and without early graft failure. Based on these curves, the area under curve+/-standard deviation (AUC+/-SD), the sensitivity and specificity were calculated. Out of 2078 consecutive patients having undergone isolated CABG from January 2001 to April 2003, 55 fulfilled the inclusion criteria and underwent acute repeat angiography. Early graft failure was found in 35 patients (group 1), whereas 20 patients did not show graft failure (group 2). CTnI and Myo, but not CK and CK-MB levels were significantly increased in group 1 compared to group 2 at 12 and 24 h after aortic unclamping. ROC analysis of cTnI, Myo and CK/CK-MB indicated cTnI as the best discriminator between the groups with 21.5 ng/ml at 12 h (AUC, 0.82+/-0.06; sensitivity, 82%; specificity, 66%) and 33.4 ng/ml at 24 h (AUC, 0.95+/-0.03; sensitivity, 98%; specificity, 82%) and Myo with 887 microg/ml at 12 h (AUC, 0.72+/-0.07; sensitivity, 73%; specificity, 57%) after aortic unclamping. In contrast, CK/CK-MB as well as the appearance of ECG-changes could not separate between the groups. cTnI, but not Myo and CK served as a reliable marker for the identification of patients with early graft failure following CABG.