Effects of Blood Transfusion on Cause-Specific Late Mortality After Coronary Artery Bypass Grafting—Less Is More

Abstract

Red blood cell transfusion after coronary artery bypass graft surgery has been associated with increased late all-cause death. Yet, whether this association is, first, independent of the packed red blood cells and perioperative morbidity association, and second, of a cardiac versus noncardiac etiology remains unknown. We analyzed patients undergoing coronary artery bypass graft surgery at two Ohio hospitals (n=6,947) from 1994 to 2007. Salvage operations and patients with preoperative renal failure were excluded. Long-term outcomes and leading cause of death (cardiac, noncardiac, all cause) were derived from the US Social Security Death Index and later from Ohio Department ofHealth Death Index. Fifteen-year mortality cumulative incidence functions were compared for transfusion groups (yes, n= 2,540; no, n= 4,806) overall, and then stratified based on perioperative complications status (yes, n= 2,638; no, n= 4,708). Comprehensive, 32covariates, risk-adjusted transfusion effects were estimated bycompeting risk regression. Results were confirmed bypropensity score adjusted analysis. Perioperative transfusions and complications occurred in 33.9% and 35.2% of patients, respectively. In all, 3,108 deaths (48.1%) have been documented (median time to death, 7.43 years). Both transfusion rates (25.6% versus 49.1%, p < 0.001) and deaths (58.2% versus 38.5%, p< 0.001) were more frequent among complications patients. Red blood cells transfusion increased intermediate to late mortality risk overall (15-year adjusted hazard ratio [AHR] 1.21, 95% confidence interval [CI]: 1.11to 1.31), and for complications (AHR 1.24, 95% CI:1.11 to 1.39) and no complications (AHR 1.16, 95% CI: 1.03to 1.31). The increased mortality was true for cardiac and noncardiac etiologies (AHR 1.19, 95% CI: 1.03 to 1.36, and AHR 1.14, 95% CI: 1.01 to 1.29, respectively). Red blood cell transfusion increased mostly cardiac deaths (AHR 1.38, 95% CI: 1.14 to 1.66) among the complications group, and noncardiac mortality (AHR 1.24, 95% CI: 1.05 to 1.47) for the no complications group. A parallel propensity matched sensitivity analysis confirmed these findings. Perioperative red blood cells transfusion is associated with significant adverse late death effects among both complicated patients and noncomplicated patients, principally seen between 0 and 5 years postoperatively, and is driven by both increased cardiovascular and noncardiovascular mortality. Further studies are needed to elucidate the mechanisms behind these findings, including their potential dose dependence.