Transplantation of Mitral Allograft into the Tricuspid Position - a Sheep Experimental Model

Abstract

Mokráček A., J. Hlubocký, J. Burkert, J. Vojáček, M. Šulda, M. Vambera, J. Kursa, V. Kroupová, P. Kobylka, J. Špatenka: Transplantation of Mitral Allograft into the Tricuspid Position -a Sheep Experimental Model. Acta Vet. Brno 2008, 77: 89-95. Our research was focused on finding the optimal technique of cryopreserved mitral allograft implantation into the tricuspid valve position in a sheep experiment. We prepared 20 cryopreserved mitral valve allografts preoperatively. These were implanted into the tricuspid position in 20 sheep via right thoracotomy, using extracorporeal circulation with cardioplegic heart arrest. We consider the transventricular papillary muscle fixation to be the best technique for obtaining optimal allograft geometry and long-term durability. We evaluated the valve function by epicardial echo before and after implantation, respectively. The findings were confirmed by haemodynamic measurements as well. It was proved that mitral allografts, harvested, processed, and stored according to the Cardiovascular Tissue Bank Protocol remained mechanically strong enough for implantation into the tricuspid position. It was demonstrated that the mitral allograft transplantation into the tricuspid position is feasible. The immediate postoperative haemodynamic performance was excellent in all animals. The mid-term results are currently being evaluatedprior to the possible application of the technique in humans at our institutions. Mitral homograft, epicardial echocardiography, cryopreservation, extracorporeal circulation, tissue banking, blood transfusion, sheepAfter half a century of history, cardiac valve surgery has become routine in developed countries. From the very beginning, mechanical and biological heart valve substitutes were designed, investigated and developed in parallel. Biological valve prostheses were simultaneously perfected in two lines -the commercial interest was focused mainly on the xenograft heart valve substitute construction, while much scientific interest was paid to the clinical use of allograft heart valves in smaller cohorts of patients. Currently about 49% of patients requiring heart valve replacement receive mechanical valve substitute and about 49% have their valves replaced by xenograft. Only 2% of diseased valves are being replaced by allografts. Nevertheless, none of these types represent an ideal valve substitute. Mechanical valve prostheses are durable, but thrombogenic, e.g. patients need anticoagulation therapy (with related complications) for the rest of life. To the contrary, biological valve substitutes are not thrombogenic, anticoagulation therapy is not necessary, but tissue degeneration remains the main reason for structural valve deterioration.Extensive research is still in progress in many commercial as well as academic centres, when the animal modelling has become a routine to assess the short-term haemodynamic characteristics as well as long-term results of new models of prostheses as well as new and/ or modified surgical implantation techniques....