New Directions in the Use of Carbon as Vascular Graft Material

Abstract

Carbon has been used to improve the thromboresistance of synthetic vascular prostheses, and for this pur pose, dacron grafts have been coated with carbon. Owing to the contradic tory results reported in the literature, a new kind of vascular conduit, ex clusively textured from carbon fi bers, has been developed. The pres ent research study was undertaken to compare carbon and expanded poly tetrafluoroethylene (e-PTFE) grafts when used as vascular substitutes. Fifty-six experimental animals were divided into four equal groups and underwent substitution of segments of infrarenal aorta or inferior vena cava (IVC), through use of either carbon or e-PTFE grafts. Prosthetic segments were removed fifteen sec onds, or sixty minutes, or seven, fif teen, thirty, sixty, or one hundred twenty days after implantation. Spec imens were examined by light and scanning electron microscopy. Cumu lative patency rates, calculated by the life-table method at 120 days after surgery, were 72% for aortic carbon grafts, 41 % for aortic e-PTFE grafts, and 0% for both carbon and e-PTFE grafts implanted on the IVC. Carbon conduits performed significantly bet ter than e-PTFE conduits when used as small-caliber arterial substitutes (p < 0.05). Fifteen seconds after blood contact, the inner surface of carbon prostheses, regardless of the implantation site, was covered with a thin proteinaceous layer, whereas e- PTFE grafts appeared almost com pletely free from hematic deposits.

One hour after implantation, a red thrombus was found to overlay the luminal surface of both carbon and e- PTFE prostheses. This layer ap peared to be thicker on the e-PTFE grafts than on the carbon grafts and thicker on the venous grafts than on the arterial. The endothelialization process of the blood-prosthesis inter face seemed to be slightly more rapid on the carbon than on the e-PTFE aortic grafts. In conclusion, this new carbon graft would appear to possess promising specifications, making it suitable for small-caliber arterial (but not venous) replacement.