Background Up to half of patients with infective endocarditis (IE) require cardiac surgery. Although anaemia is common, its precise prevalence, transfusion practices and impact on outcomes in surgically treated IE patients remain unclear. Therefore, our aim was to determine the incidence and severity of preoperative anaemia, describe transfusion and coagulation management and evaluate associations of anaemia and red blood cell (RBC) transfusion with mortality, including sex-based differences.

Methods This retrospective multicentre cohort study used data from the Netherlands Heart Registration, including all adult patients who underwent valve surgery for active IE between 1 January 2016 and 31 December 2023. Anaemia was defined by WHO criteria. Kaplan-Meier and Cox proportional hazards models were used to evaluate associations between anaemia severity, RBC transfusion and 30-day and 1-year mortality. Multivariable analyses were adjusted for age, sex, prior valve surgery, renal dysfunction, surgery urgency, cardiopulmonary bypass and aortic cross-clamp times, surgical re-exploration, preoperative critical illness, surgical re-exploration and year of surgery.

Results Of 2480 patients, 84.9% had preoperative anaemia (50.7% moderate, 2.8% severe). RBC transfusion occurred in 78.7% of patients. 30-day and 1-year mortality were 10.6% and 16.6%, respectively. Moderate and severe anaemia were associated with higher mortality in univariable, but not in multivariable analysis. RBC transfusion remained independently associated with mortality at both time points (adjusted HR for mortality at 30 days 3.58, 95% CI 2.07 to 6.19). Female patients had higher transfusion rates and mortality.

Conclusions Anaemia and transfusion are highly prevalent in IE surgery and associated with increased mortality. RBC transfusion is an independent predictor of adverse outcomes, underscoring the need for improved anaemia management and individualised transfusion strategies.