Previous studies indicated higher long-term mortality after the transfusion of allogeneic red blood cells (RBC); newer recommendations emphasize lower transfusion rates. The consequences of the transfusion of RBCs in cardiac surgery are unclear because later studies focused on transfusion triggers and short-term outcomes. Reports on long-term complications after cardiac surgery are few.

The mandatory Western Denmark Heart Registry was used to identify all adult cardiac operations performed in 4 centres from 2000 to 2019. Patients with multiple entries or previous cardiac operations, special/complex procedures, dying within 30 days and not eligible for follow-up were excluded.

A total of 32,581 adult cardiac operations performed in 4 centres from 2000 to 2019 were included. The Kaplan–Meier survival plot for low-risk patients undergoing simple cardiac operations showed a significantly lower 15-year survival (0.384 vs 0.661) of patients who received perioperative RBC transfusions [odds ratio 2.43 (confidence level 2.23–2.66)]. The risk decreased with increasing comorbidity or age. No difference was found in high-risk patients. The adjusted risk ratio after an RBC transfusion, including age, sex, comorbidity and surgery, was 1.62 (1.48–1.77).

Despite reduced transfusion rates, long-term follow-up on especially low-risk patients undergoing comparable cardiac operations still demonstrates substantially more deaths of patients receiving perioperative RBC transfusions. Even transfusion of 1–2 units is associated with increased long-term mortality.