Pulse doppler and M-mode to assess viability of cardiac allografts using heterotopic femoral heart transplantation in rats.

Noninvasive assessment of heterotopic heart transplants using Doppler echocardiography was first described in two patients by Allen at Stanford in 1981. Since then, numerous experiments studying heterotopic heart transplantation in humans and large animals have confirmed its utility by employing either an intra-abdominal or cervical model. In rats, however, prior research investigating intra-abdominal heterotopic hearts has showed echocardiography to be ineffective. We have recently developed a new technique for heterotopic femoral heart transplantation in rats, which employs the novel use of trans-femoral echocardiography. Therefore, our goal was to re-examine the efficacy of echocardiography for detection of graft rejection.

A new modified technique for heterotopic femoral heart transplantation in rats.

BACKGROUND: 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 sutureless cervical vessel anastomoses. Rao and Lisitza developed a femoral heart accessory transplant model in 1985. Our goal was to improve this femoral model for the study of cardiac transplantation between both syngeneic and allogeneic rats. METHODS: ACI and Lewis rats weighing 150 to 350 g were used as donors and recipients (n = 12). The left common carotid and left pulmonary arteries were anastomosed to the femoral artery and vein in an end-to-end fashion, respectively. Improved modifications included the use of hemostatic vessel clips, heparinization of both donor and recipient, a ventricular prolene stay-suture for secure graft placement, and transfemoral echocardiography (TFE). Total operative time averaged 61 +/- 12 minutes. RESULTS: Femoral accessory transplanted hearts (FATHs) allowed easier pulse palpation and access for TFE versus previously described cervical and intra-abdominal models. This modification allows precise detection of acute graft rejection (AGR) and is defined as absent ventricular contraction in the presence of anastomostic patency. CONCLUSIONS: Our new modified technique for heterotopic femoral heart transplantation in rats is a relatively easily learned and reproduced procedure that allows superior allograft access for palpation and improved echocardiographic assessment. Femoral heterotopic heart transplantation remains an effective model for allograft transplantation study.

North American multicenter experience with the On-X prosthetic heart valve.

BACKGROUND AND AIM OF THE STUDY: This ongoing, longitudinal, multi-center, North American study was designed to evaluate the safety and effectiveness of the On-X valve. METHODS: The On-X valve was implanted in isolated aortic (AVR) and mitral (MVR) valve replacement patients at nine North American centers. Follow up was 98.6% complete. Anticoagulation compliance was evaluated by collection of international normalized ratio (INR) results in all patients throughout their postoperative follow up. Adverse events were recorded according to the AATS/STS guidance criteria. Hematologic studies were conducted postoperatively to evaluate hemodynamics and hemolysis. RESULTS: In total, 142 AVR and 142 MVR implants were performed; the mean follow up was 4.5 years; total follow up was 1,273 patient-years (pt-yr). At implant, the mean patient age was 59.2 years (range: 28 to 85 years); 71.8% of patients who underwent AVR and 33.1% who underwent MVR were males. Preoperatively, 89.4% of AVR patients and 56.3% of MVR patients were in sinus rhythm. The cardiac disease etiology was primarily stenotic, calcific degeneration in AVR and rheumatic or degenerative regurgitation in MVR. Hemolysis represented by postoperative elevation of serum lactate dehydrogenase was very low (median 217 IU after AVR and 251 IU after MVR at one year (82% AVR and 98% MVR of upper normal). Late adverse event rates were low, most notably thromboembolism (0.9%/pt-yr after AVR; 1.6%/pt-yr after MVR) and thrombosis. Kaplan-Meier event-free rates at five years were correspondingly high. Anticoagulation compliance analysis showed only about 40% of INR readings to be within target ranges postoperatively; thus, the control range achieved was much greater than the desired target, as might generally be expected for clinic-controlled INR. CONCLUSION: The On-X valve performed well in this study, confirming the original design intent of minimal hemolysis and low adverse event rates.