Optimal Perfusion Pressure Enhances Donor Heart Preservation During Normothermic Ex Situ Perfusion in a Rat Transplantation Model

<i>Background and Objectives:</i> Normothermic ex situ heart preservation maintains donor heart viability by sustaining physiological conditions and reducing ischemic damage. However, the ideal perfusion pressure remains uncertain. This study aims to identify the optimal perfusion pressure to enhance graft preservation in rat heart transplantation. <i>Materials and Methods</i>: We utilized 20 male Sprague-Dawley rats (400-500 g). Donor hearts underwent normothermic preservation for 2 h using a Langendorff apparatus primed with 12 mL of solution at a consistent 3 mL/min flow. After preservation, hearts were transplanted heterotopically into the recipient's abdomen. We defined successful preservation by observing a QRS complex in electrocardiographic monitoring for 3 h post-transplantation. Histological assessments for myocardial integrity occurred after 4 h of reperfusion. We analyzed statistical differences between successful and unsuccessful preservation groups. <i>Results:</i> Electrocardiograms indicated preservation failure in 8 of the 20 donor hearts due to the absence of a QRS complex. We observed no significant differences in ischemic duration between groups. At 120 min, although serum lactate and potassium concentrations increased in the unsuccessful group, the differences were not statistically significant. Higher initial perfusion pressures (>65 mmHg) at a constant flow rate resulted in elevated lactate and potassium concentrations post-preservation, indicating suboptimal outcomes. Histologically, hematoxylin and eosin staining showed better myocardial preservation in successful hearts, while TUNEL assays demonstrated increased apoptosis in unsuccessful hearts. All hearts increased in weight after preservation, but significant increases occurred only in unsuccessful cases. <i>Conclusions:</i> Higher initial perfusion pressures (>65 mmHg) negatively affect heart preservation outcomes, resulting in elevated serum lactate and potassium levels, increased heart weight, and greater histological damage. Maintaining optimal perfusion pressures is essential to preserve myocardial integrity and functional viability during normothermic ex situ heart preservation.