A Novel Technique in a Sheep Model for Evaluating Prosthetic Heart Valve Performance

There have been many various animal studies to evaluate the structural integrity and antithrombogenicity of prosthetic heart valves. We were interested in developing a novel sheep model to study the thrombogenicity of mechanical heart valves placed into the systemic circulation but without the need for cardiac bypass. Also, we wanted to minimize the risk of paraplegia from complete thoracic aortic clamping. Six sheep underwent left lateral thoracotomy for placement of a mechanical heart valve in parallel with the descending thoracic aorta. A valved conduit with a dacron tube graft sutured to the back end was fashioned. Employing partial aortic occlusion with a side-biting clamp, the proximal and distal ends were anastomosed in an end-to-side fashion. Once flow was confirmed through the graft, the native aorta was occulded with umbilical tape. The sheep received no postoperative anticoagulation. The median operative time and estimated blood loss (EBL) was 170 min and 250 cc, respectively. Patency of the va...