Higher IL-6 levels but not IL6 −174G > C or −572G > C genotype are associated with post-operative complication following coronary artery bypass graft (CABG) surgery

Abstract Large increases in inflammatory markers, particularly IL-6, occur after cardiac surgery. However, despite interventions to reduce the inflammatory response, great variability still remains which could in part be attributable to genetic predisposition. Since increased IL-6 levels following surgery are also associated with poorer outcome we sought to determine whether baseline and post-operative levels of Interleukin-6 (IL-6) and functional common variants of the Interleukin-6 ( IL6 ) gene are associated with post-operative outcome following coronary artery bypass grafting (CABG). Caucasian patients undergoing first-time elective CABG were studied. IL-6 levels were measured pre-, 6h and 24h following surgery and genotypes for IL6 gene variants −174G>C and −572G>C were obtained. Clinical data was collected daily until patient discharge. Patient outcome was categorised as with (ICUC, n =177) and without (NICUC, n =189) a post-operative complication during the ICU period and with (POC, n =215) and without (NC, n =151) a post-operative complication during hospitalisation. IL-6 levels pre- and at 24h were greater in POC and ICUC than NC and NICUC, respectively. Pre- IL-6 levels independently predicted (for 1 standard deviation increase in log IL-6) POC (OR 1.4, 95% CI 1.1–1.7, p =0.008) and ICUC (OR 1.3, 95% CI 1.0–1.6, p =0.02) outcomes. Overall, the IL6 -572G>C had an effect over time on IL-6 levels ( p =0.04) and on IL-6 levels in NC (P=0.008) and NICUC ( p =0.006). However, no associations were found with the IL6 −572G>C or −174G>C variants on IL-6 levels at individual time-points or by outcome group. Thus, in conclusion, elevated pre-operative IL-6 levels, but not IL6 gene variants predict poor patient outcome following CABG.