Cystatin C as a predictive marker of renal dysfunction and mid-term outcomes following off-pump coronary artery bypass grafting

OBJECTIVE To determine whether plasma cystatin C and creatinine levels after isolated off-pump coronary artery bypass grafting (OPCAB) are predictive of postoperative renal dysfunction and clinical outcomes. METHODS Between January 2008 and December 2013, 1033 who underwent isolated OPCAB were recruited. The patients were divided into three groups according to the preoperative level of cystatin C: low (0.83 mg/L>), mid (0.83-1.13 mg/L) and high (1.13 mg/L<). The endpoints of all-cause mortality and major adverse cerebrovascular and cardiovascular events were compared among three groups using the Kaplan-Meier method. The predictive power of cystatin C was compared with creatinine using receiver operating curves. RESULTS Follow-up was complete in all of the included patients at a mean of 2.9±1.5 years. Within the follow-up period, 9 early (30-day mortality) and 46 late deaths occurred. The 30-day mortality was zero, four (44%), and five (56%) cases in low, mid and high groups, respectively (p=0.03). The cut-off value of cystatin C for renal dysfunction prediction was approximately 1.04 (mg/L, p<0.001), and cystatin C showed greater predictive power than creatinine for renal dysfunction (area under the curve=0.73 vs 0.65; p=0.01). One-year and five-year overall survival in low, mid and high groups were 99.2%, 98.9% and 94.3%, and 97.9%, 97.3% and 86.3%, respectively (low vs high, p=0.01). CONCLUSIONS Cystatin C is a stronger predictor of postoperative renal dysfunction than serum creatinine, and its level is directly correlated with mid-term OPCAB adverse results.