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

Abstract

Background: 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.

Methods: 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 of Health 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, 32 covariates, risk-adjusted transfusion effects were estimated by competing risk regression. Results were confirmed by propensity score adjusted analysis.

Results: 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]: 1.11 to 1.31), and for complications (AHR 1.24, 95% CI: 1.11 to 1.39) and no complications (AHR 1.16, 95% CI: 1.03 to 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.

Conclusions: 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.