Myocardial oxygen handling and metabolic function of ex-situ perfused human hearts from circulatory death donors

This study investigated oxygen handling of human hearts donated after circulatory death (DCD) on normothermic ex-situ heart perfusion (ESHP) and evaluated oxygen handling markers as adjuncts to cardiac viability assessment.

This single-center retrospective study included human DCD heart transplantation procedures using ESHP. Lactate concentrations, blood gas, myocardial oxygen consumption (MVO₂), delivery (MDO₂), and extraction (MEO₂), coronary blood flow (CBF), coronary vascular resistance (CVR), and adenosine infusion were reported over time. Correlation between parameters was assessed, and statistical testing compared patients who did and did not require extracorporeal membrane oxygenation (ECMO) support after transplantation.

Lactate concentrations decreased during ESHP in all transplanted hearts (n = 25) and increased in 1 rejected heart. Arterial partial pressure of oxygen (PO₂) was 75.2 ± 2.9 kPa, with an arteriovenous ΔPO₂ of 44.8 ± 10.4 kPa. Oxygen saturation was 100% in most arterial and venous samples. Average MVO₂ was 2.7 ± 0.6 ml/min/100 g myocardium, MDO₂ 98.5 ± 20.4 ml/min, and MEO₂ 8.6 ± 1.8%. Average CVR was 0.025 ± 0.006 mm Hg min/ml/100 g and increased over time. ΔPO₂ correlated strongly with MVO₂ (R = 0.797, p < 0.001) and lactate trend (R = 0.799, p < 0.001) in transplanted hearts, without differences compared to the rejected heart with increasing lactate. Adenosine infusion on ESHP was significantly higher in patients requiring ECMO post-transplantation vs non-ECMO cases (11.7 (4.5-21.0) vs 2.2 (1.5-6.7) ml/h, p = 0.039).

Hearts on normothermic ESHP receive excessive MDO₂, due to high PO₂ and CBF, while the MVO₂ is relatively low. Thus, CBF and PO₂ can potentially be lowered. Furthermore, ΔPO₂ could serve as additional marker of metabolic function under these hyperoxic circumstances. The adenosine infusion rate might predict post-transplantation ECMO requirement.