Experience with vascular grafts in total artificial heart replacement

In total artificial heart replacement the pumps are attached to the vascular system with the help of connectors. These consist of a woven Dacron vessel graft to which a short silastic segment is vulcanized. In 36 calves surviving total artificial heart replacement between one and seven months (average 85 days) the morphological alterations due to interfacial reactions were studied: thrombus formation and neointimal fibrous hyperplasia at the anastomoses. In 15 calves (41.7%) thrombus growth within the outflow tract led to anastomotic stenosis: pulmonary artery 14 (93.3%), aorta-anastomosis 1 (2.8%), both vessels 1 (2.8%), in combination with pannus growth in atrial location 13 (86.7%). In 73.3% the pannus consisted of infected organized thrombus imitating the course of septic vegetative endocarditis. Two calves were reoperated in order to remove the vegetative thrombi, one successfully. In five animals pulmonary stenosis was the main cause of death. The presence and location of excessive tissue growth and thrombus formation within the outflow tract are also inherent to the fluid mechanical design of the valve. Neointimal fibrous hyperplasia at the anastomoses of the grafts seems to be a reparative process started up by platelet-induced subendothelial cell proliferation in response to intimal injuries.