Blood Group AB Is Associated with Decreased Blood Loss but also Worse Outcome in Aortocoronary Bypass Surgery

 

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Objectives: Blood group (BG) specific differences in coagulation have been observed in many patient groups and are thought to be mostly due to the reduction of circulating Von-Willebrand factor (vWF) levels by 30% in BG type O (BG-O) individuals as opposed average and BG type AB (BG-AB) displaying the highest vWF levels of the BG phenotypes. This “ABO-effect” is associated with increased bleeding in ECMO therapy as well as with protective effects regarding acute coronary thrombosis and deep vein thrombosis for BG-O individuals. Aim of this study was to investigate the association between blood types and perioperative transfusion requirements and mortality respectively in patients undergoing isolated coronary artery bypass grafting (CABG).

Methods: We retrospectively analyzed 5,713 patients undergoing isolated CABG procedures in our center between May 2004 and March 2019. The association between the different blood types (O: n = 2,180, A: n = 2,591, B: n = 667 or AB: n = 275) and the outcomes of in-hospital mortality, perioperative red blood cell transfusions (RBC), duration of postoperative hospital stay, and postoperative neurologic events were evaluated. Results of the univariate analysis for mortality were further validated using a logistic regression model (R v3.6.0, R software foundation, Vienna).

Results: Mortality in BG-AB was significantly higher compared to patients with non-AB (4.7 vs. 2.5%, p = 0.03). This association was also observed in the multivariate model after compensation for cofounders (adjusted odds ratio = 2.04, p = 0.026). The proportion of BG-AB patients not requiring transfusions was significantly higher (55.6 vs. 49.3%, p = 0.04) and the average number of RBC transfusions tended to be lower (2.44 vs. 2.94 units, p = 0.06) as compared to non-AB. No significant differences were found regarding postoperative neurologic events and length of hospital stay.

Conclusion: The results of our analysis suggest that blood group type AB patients have a reduced need for RBC transfusions whereas perioperative mortality is increased in these patients. While the cause of this phenomenon is not clear, the higher levels of vWF in BG-AB patients described in the literature could explain this observation of decreased blood loss and increased mortality. While further research is necessary to establish the cause of this effect, therapeutic consequences such as different anticoagulation strategies in this patient collective should be discussed.