Increased mortality after coronary artery bypass graft surgery is associated with increased levels of postoperative creatine kinase-myocardial band isoenzyme release - Results from the GUARDIAN trial

OBJECTIVES We sought to determine if elevated cardiac serum biomarkers afte r coronary artery bypass graft surgery (CABG) are associated with increased medium-term mortality and to identify patients that may benefit from bette r postoperative myocardial protection. BACKGROUND The relationship between the magnitude of cardiac serum protein elevation and subsequent mortality after CABG is not well defined, partly b ecause of the lack of large, prospectively studied patient cohorts in whom postoperative elevations of cardiac serum markers have been correlated to m edium- and long-term mortality. METHODS The GUARD during Ischemia Against Necrosis (GUARDIAN) study enrolle d 2,918 patients assigned to the entry category of CABG and considered as h igh risk for myocardial necrosis. Creatine kinase-myocardial band (CK-MB) i soenzyme measurements were obtained at baseline and at 8, 12, 16 and 24 h a fter CABG. RESULTS The unadjusted six-month mortality rates were 3.4%, 5.8%, 7.8% and 20.2% for patients with a postoperative peak CK-MB ratio (peak CK-MB value/ upper limits of normal [ULN] for laboratory test) of <5, greater than or eq ual to5 to < 10, greater than or equal to 10 to < 20 and greater than or eq ual to 20 ULN, respectively (p < 0.0001). The relationship remained statist ically significant after, adjustment for ejection fraction, congestive hear t failure, cerebrovascular disease, peripheral vascular disease, cardiac ar rhythmias and the method of cardioplegia. delivery. Receiver operating char acteristic curve analysis revealed an area under the curve of 0.648 (p < 0. 001); the optimal cut-point to predict six-month mortality ranged from 5 to 10 ULN. CONCLUSIONS Progressive elevation of the CK-MB ratio in clinically high-ris k patients is associated with significant elevations of medium-term mortali ty after CABG. Strategies to afford myocardial protection both during CABG and in the postoperative phase may serve to improve the clinical outcome. ( C) 2001 by the American College of Cardiology.