Prolonged ischemic time remains a major barrier to donor use and is strongly associated with primary graft dysfunction in heart transplantation. We evaluated whether intraoperative recipient metabolic adequacy, quantified as low oxygen extraction ratio burden during cardiopulmonary bypass, is associated with reduced severe primary graft dysfunction risk in grafts with prolonged ischemic time.

Adult heart transplant recipients (November 2021 to June 2025) with temporal cardiopulmonary bypass perfusion data were retrospectively analyzed. The exposure was the percentage of cardiopulmonary bypass time with oxygen extraction ratio more than 0.25. Recipients were stratified by ischemic time (<4 vs ≥4 hours) and modeled using weighted penalized logistic regression with interaction testing. In the prolonged ischemic time subgroup (>4 hours), sensitivity analyses and g-computation estimated risk reduction and events prevented under counterfactual oxygen extraction ratio burden policies. A post hoc continuous-exposure robustness analysis assessed dose–response relation.

A total of 373 recipients were included in the study. In prolonged ischemia, each 5% increase in bypass time with oxygen extraction ratio more than 0.25 increased the odds of severe primary graft dysfunction (odds ratio, 1.16, P = .005). Within prolonged ischemia (N = 171), oxygen extraction ratio burden 25% or less was associated with lower odds of severe primary graft dysfunction (odds ratio, 0.21, 95% CI, 0.07-0.54; P < .001). Continuous exposure analysis confirmed a dose response–associated risk reduction in severe primary graft dysfunction with low oxygen extraction ratio.

Lower intraoperative oxygen extraction ratio during cardiopulmonary bypass was associated with reduced primary graft dysfunction and improved early outcomes, particularly when ischemic time was prolonged, supporting oxygen extraction ratio–guided metabolic optimization as a scalable intraoperative recipient-side strategy during heart transplantation warranting prospective validation.