Patients with AB blood type 20% less likely to die after CABG surgery

A new study presented at ANESTHESIOLOGY 2011 focused on whether blood type affects survival after heart surgery. Researchers from Duke University Medical Center studied more than 15,000 patients to determine if a specific blood type puts patients at a higher risk for death or complications after coronary artery bypass graft (CABG) surgery.

The Duke researchers found that patients with AB blood type were 20 percent less likely to die after CABG surgery than patients with A, B or O blood types. Two proteins in the blood responsible for clotting - the von Willebrand factor (vWF) and Factor VIII (FVIII) -could explain the reduced risk.

The gene that passes on group O confers lower levels of these clotting proteins. Each person has two genes (one from each parent) to determine blood group; all group O patients have two O genes (OO). Some group A and group B patients have one group A or B and one group O gene (AO and BO) and have intermediate levels of clotting proteins. Group AB has no O genes and has the highest levels.

Individuals with type O blood (nearly half of the population) have lower levels of these clotting proteins and may be at greater risk for bleeding and blood transfusions after surgery. Evidence suggests that individuals with type AB blood may be more likely to develop blood clots and/or bleed less after surgery, said lead study author Ian J. Welsby, M.D. -However, blood clots do not appear to be a problem and bleeding less could contribute to the lower death rate in AB blood type patients since bleeding and blood transfusions put patients at a higher risk for death or complications after surgery.

The study concluded that AB patients are at lowest risk for bleeding and that further research is required to determine the order of risk in other blood types (A, B and O groups).

Researchers hope future studies will help with the ability to predict risk levels for bleeding after cardiac surgery using a simple, cheap blood group test. Researchers also want to determine whether boosting the vWF level in non-AB patients to the level found in AB patients will result in better outcomes after heart surgery.