A New Modified Technique for Heterotopic Femoral Heart Transplantation in Rats

Abbott developed the first experimental accessory heart transplant rat model in 1964. This intra-abdominal model required a labor-intensive aortic anastomosis. In 1971, Heron modified the operation by using a sutureless cervical vessel anaastomosis. Rao and Lisistza developed a femoral heart accessory transplant model in 1985. The authors' goal was to improve this femoral model for transplantation between both syngeneic and allogeneic rats.

ACI and Lewis rats weighing 150 to 250 g were used as donors and recipients. It was advantageous to select donors of equal or smaller size for optimal vessel size match. The left common carotid and left pulmonary arteries were anastomosed to the femoral artery and vein in an end-to-end fashion. Improved modifications included the use of hemostatic vessel clips, heparinization of both donor and recipient, and the use of a ventricular Prolene stay suture for easier mobilization and secure graft placement. Total operative time averaged less than 2 hr. Postoperative evaluation included daily weights, accessory heart palpation, and trans-femoral echocardiography. The pulse scale score, based on palpable contraction intensity, ranged from 1 (slow and weak) to 4 (fast and strong).

Heterotopic femoral transplanted hearts (FTHs) allowed easier pulse palpation and access for echo vs. previously described cervical and intra-abdominal models. This modification allows precise detection of acute graft rejection (AGR). AGR is defined as absent ventricular contraction on echo in the presence of anastomotic patency. FTH pulse scores gradually increased from 2 (immediately post surgery) to 4 (within 48 hr). In the allogeneic group (ACl to Lewis), pulse scores declined to 1 on postoperative day 4 prior to AGR. Echo on FTHs demonstrated good ventricular contraction, patent graft vessels with laminar flow, papillary muscle contraction causing mitral valve opening/closing vs. no ventricular contractions after AGR.