A simple new model of physiologically working heterotopic rat heart transplantation provides hemodynamic performance equivalent to that of an orthotopic heart

Background: The widely used non-volume-loaded abdominal heterotopic heart transplant (NL) in rats undergoes atrophy after transplantation. Various techniques have been designed to load the transplanted heart because of its potential immunological impact. Our aim was to create a volume-loaded heterotopic heart transplantation model (VL) capable of ejection and practical for routine studies. Using this model, we tested the hypothesis that VL isografts would retain myocardial performance comparable to native hearts (NH). Methods: Heterotopic hearts were transplanted using and end-to-side anastomosis between the donor's superior vena cava and the recipient's abdominal inferior vena cava. The right ventricle loads the left ventricle (LV) via a direct anastomosis of the pulmonary artery to the left atrium. The LV ejects volume through an end-to-side anastomosis of the donor's aorta to the recipient's abdominal aorta. Hemodynamic data (systolic and diastolic LV pressures, dP/dt max and min, tau) were studied in-situ (at baseline and after adding volume) and in a Langendorff perfusion system (at baseline and after stimulation with isoproterenol) 2 weeks after transplantation. Results: In situ systolic pressure and diastolic function of VL was superior to NL, and P-adrenergic stimulated performance in the Langendorff perfusion of VL showed hemodynamic performance equivalent to NH, unlike NL which had a diminished response. Conclusion: This technique results in a volume-loaded ejecting heart transplant model that preserves anatomical structures. The VL can be evaluated in situ and after explantation in Langendorff perfusion system and may offer advantages if workload of the graft is of significance to the study performed.