A NEW, BIVENTRICULAR WORKING HETEROTOPIC HEART-TRANSPLANT MODEL - ANATOMIC AND PHYSIOLOGICAL CONSIDERATIONS

Background. Current heterotopic heart transplant models have nonworkin g left ventricles that atrophy and are not suitable for some studies. We developed and characterized a new heterotopic model with working le ft and right ventricles.Methods. Hemodynamics were compared in the wor king and nonworking models. The influence of the length of the donor's aorta on coronary arterial oxygenation was tested. The influence of t he recipient's arterial pressure on developed left ventricular systoli c pressure and the effects of alpha- and beta-adrenergic stimulation w ere examined in both models. The nonworking and working models were co mpared in chronic transplant preparations to investigate possible vent ricular atrophy. Results. In this model, coronary arterial oxygen tens ion was influenced by the length of the donor's aorta. With a short do nor aorta (0.5 cm in the porcine model), normal coronary arterial oxyg enation is maintained. Left ventricular systolic pressure was greater in the working compared with the nonworking models. Left ventricular s ystolic pressure did not respond to alpha-adrenergic stimulation but d id respond to beta-adrenergic and combined stimulation, which indicate s its relationship to donor heart output. Left ventricular systolic pr essure correlated with and was determined by recipient arterial pressu re. Ventricular atrophy occurred in the nonworking model, but ventricu lar weight was maintained at sham control levels in this new working m odel. Conclusion. These results demonstrate the surgical anatomic cons iderations of a new heterotopic heart transplant model in which the le ft and right ventricles work. Its hemodynamic performance is related t o recipient hemodynamics, and the model responds to adrenergic stimula tion. In chronic studies, ventricular mass is maintained, thus allowin g this model to overcome a significant shortcoming of existing heterot opic heart transplant models.