Extending Normothermic Ex Situ Heart Preservation and Viability to 48 Hours via Protein Supplementation and Plasma Exchange.

Prolonged normothermic ex situ heart perfusion (NEHP) could expand the donor pool by decoupling procurement, transport, and implantation, but clinically used systems rarely exceed 4-6 hours. We evaluated pragmatic protein replacement strategies enabling 48-hour NEHP in adult porcine hearts without biologic cross-circulation. Thirteen juvenile pigs (50.6 ± 5.0 kg) underwent Langendorff NEHP and were randomly assigned to 65 kDa serum fractionate (SF65; n = 5), continuous infusion of serum fractionated to <65 kDa with hemofiltration; 120 kDa serum fractionate (SF120; n = 3), consisting of serum fractionated to <120 kDa with hemofiltration; or plasma exchange (PE, n = 5), consisting of unfractionated plasma with concomitant plasma filtration and intermittent hemofiltration. Hearts were perfused for 48 hours with intermittent working-mode assessments under predefined failure criteria. All hearts completed 48 hours without failure. PE demonstrated the lowest coronary resistance at 37-48 hours (0.13 ± 0.05 vs. 0.30 ± 0.13 SF65, 0.69 ± 0.31 SF120 mm Hg/ml/min); SF120 exhibited markedly higher aortic regurgitation (38.1% ± 27.7% vs. 5.7% ± 4.9% SF65, 5.0% ± 6.7% PE); SF65 showed the greatest edema (interventricular septal wall diameter [IVSd] increase 102% ± 23% vs. 37% ± 17% SF120, 33% ± 19% PE); and echocardiographic indices and composite histologic injury scores were similar among groups. Reproducible 48-hour NEHP of adult porcine hearts is feasible using clinically accessible protein replacement strategies. PE approximates the benefits of fractionated serum regimens while avoiding large-protein accumulation and represents a practical path toward translational long-duration heart perfusion.