Long-term histological changes in 1 millimeter polytetrafluoroethylene (Gore-Tex) prosthetic arterial grafts.

Vein grafts are used extensively to repair blood vessels. However, when suitable vein segments are unavailable, alternative graft materials must be used. This study tested the suitability of 1 mm diameter polytetrafluoroethylene (PTFE) grafts for small-calibre arterial replacements. Grafts of 4 mm length were inserted microsurgically into the iliac arteries of 26 rats. The grafts were removed between 3 and 22 months postoperatively and examined with light microscopy and scanning and transmission electron microscopy (SEM:TEM). Anastomotic intimal hyperplasia was minimal, consisting of a few smooth muscle cells extending 100-200 microns onto the graft. The rest of the PTFE was covered with endothelium. In a few isolated areas, there was a subendothelial layer of smooth muscle, 2-10 cells thick. The short segments used in this study were highly successful, with an overall long-term patency rate of 80%. These grafts showed no evidence of excessive neo-intimal hyperplasia.

Vein to artery allografts: experimental evidence of immunological sensitivity in rats.

Vein allografts were studied in rats using the major histocompatibility complex-incompatible DA (RTIa) and LEW (RTI1) inbred strains. Allografts from DA rats were inserted in to 22 LEW hosts, and vice versa, by interposing a 5 mm segment of donor iliolumbar vein into a defect in the host's iliac artery (1 mm in diameter), using microsurgical techniques. Grafts were left in situ for 6 weeks and were then tested for evidence of sensitization by the insertion of an allogeneic fetal heart from the donor strain into the host's foot pad. The fetal heart beat was recorded with an ECG and the time of rejection determined by the cessation of ECG activity. As controls, allogeneic donor fetal hearts were implanted into 40 host rates (20 of each strain) which had not previously received a donor vein allograft. These were monitored by ECG, as above. Control LEW host rats rejected DA fetal hearts in a mean time of 8.45 days. Control DA hosts rejected LEW fetal hearts in 8.70 days. DA hosts with LEW vein allografts did not reject donor fetal hearts significantly sooner (mean 8.33 days) than the controls. However, LEW host rats with allografted DA veins rejected subsequent DA fetal hearts in 7.18 days, which was significantly sooner than in controls (8.45 days). These data provide evidence of sensitization of the rejection response by vein allografts.