The histology of seeded PTFE grafts in humans

To define the histology of PTFE femoral-popliteal grafts seeded with enzymatically-derived endothelium, we examined light level and selected scanning electron micrographs of 20 graft biopsies. Thirteen grafts were chronically occluded and the midgraft samples had a thin lining of fibrin with scattered erythrocytes and leukocytes. One anastomotic sample showed a similar pattern, while three others had neointimal fibrous hyperplasia. Six of the seven remaining midgraft samples demonstrated confluent endothelial healing over parts of the flow surface. The cells were commonly distributed along one side of the graft as viewed in cross-section. Distribution patterns were not improved by changing from a single inoculum with two graft rotation-incubation periods to a sequential inoculation separated by a graft rotation. Circumferential distribution was achieved in one instance in which inoculation was characterized by a relatively high cell density. No luminal endothelium was seen when inoculation cell densities were very low. Smooth muscle cells and fibroblasts were not seen in the subendothelial "inner capsules" of the midgrafts. We conclude that endothelialization occurs in a high proportion of seeded PTFE grafts in humans, that the donor vein surface area should measure at least 5.25% of the inoculated graft surface, that further modifications in the seeding technique will be required to achieve consistent circumferential endothelial distribution, that subendothelial smooth muscle cell invasion is uncommon in the midgraft, but that anastomotic neointimal fibrous hyperplasia probably contributed to some graft failures.