Experimental heterotopic heart transplantation without cardiopulmonary bypass: auxiliary support for the recipient...

Auxiliary cardiac support using heterotopic heart transplant is of considerable interest, but the outcome is not known. To investigate technical feasibility and the possibility of using auxiliary support from heterotopic heart transplantation without cardiopulmonary bypass, we evaluated hemodynamics including the pressure-volume relationship in experimental animals.

In heterotopic heart transplantation, we tailored the donor heart by removing the pulmonary and tricuspid valves, and by wide removal of the inter-atrial septum. Next, we anastomosed the descending aorta and left atrium of the donor heart to the descending aorta and left atrium of the recipient, without using cardiopulmonary bypass. Consequently, declamping the recipient's descending aorta allowed the donor heart to fill with blood and to start beating. We performed hemodynamic assessments including the effects of adrenergic stimulation. We measured the pressure and volume relationship of the recipient heart by closing and opening inflow of the donor left atrium to change the pre-load of the donor left ventricle.

The donor left ventricle produced a systolic blood pressure that was augmented by the recipient blood pressure and responded to adrenergic stimulation. When inflow of the donor left atrium was opened, the pressure-volume loop of the recipient heart shifted to the left and pressure-volume area decreased. Simultaneously, the mechanical efficiency and E(max) (the slope of the end-systolic pressure-volume relationship) of the recipient heart increased when inflow of the donor left atrium was opened.

This transplant model, without cardiopulmonary bypass, is feasible and can be applied to transplant investigations as a working heart model on the basis of the response of adrenergic stimulation. The increased pre-load of the donor left atrium from the recipient left atrium resulted in a recipient leftward shift of the pressure-volume relationship, suggesting that this transplant model with adequate pre-load acts as auxiliary assistance in the recipient intrathoracic cavity.