Acceleration of neointima formation in vascular prostheses by transplantation of autologous venous tissue fragments. Application to small-diameter grafts.

We have previously demonstrated rapid and complete endothelialization in synthetic fabric vascular prostheses that have been pretreated with autologous venous tissue fragments. However, significant thrombogenicity has been a major problem when this method has been applied to small-diameter grafts. By masking the positively charged collagen fibrils in the tissue fragments with negatively charged heparin, we were able to overcome this problem. A canine jugular vein was resected, minced into tissue fragments, and suspended. This mixture was sieved through the wall of a highly porous vascular prosthesis with a water porosity value of 4,000 ml/cm2 per minute by pressurized injection, which caused the tissue fragments to be trapped in the graft wall. Tissue-fragmented grafts (7 mm inside diameter, 5.7 cm long) were implanted into the thoracic aorta of 35 dogs. In addition, tissue-fragmented grafts of small diameter (4 mm inside diameter, 3.5 cm long) were pretreated with heparin and implanted into the carotid arteries of 16 dogs (32 grafts). Preclotted grafts without tissue fragmentation were implanted into the thoracic aorta (25 dogs) and carotid arteries (6 dogs, 12 grafts) as controls. Grafts were explanted from 1 to 495 days after implantation. New arterial wall formation was complete throughout the tissue-fragmented grafts within 2 weeks; however, in the control grafts, neointima formation was limited to the anastomotic sites even after 2 months. Twenty small-caliber tissue-fragmented grafts that were pretreated with heparin in the carotid position were patent, but all the control grafts were occluded within 1 week. These results demonstrate that neointima formation can be enhanced in synthetic fabric prostheses; furthermore, long-term patency of vascular grafts of small caliber is possible in dogs with this tissue-fragmentation technique.