IMPROVEMENT OF PATENCY RATE IN HEPARIN-COATED SMALL SYNTHETIC VASCULAR GRAFTS

Background-Graft thrombosis and intimal hyperplasia represent the majo r causes of graft failure. Heparin has been shown to have a beneficial effect on long-term patency and on prevention of intimal hyperplasia. Thus, the purpose of the present study was to evaluate the effect of heparin coating on patency rate and intimal hyperplasia in small synth etic vascular grafts. Methods and Results-Two synthetic grafts (expand ed polytetrafluoroethylene [ePTFE], and polyurethane) with and without heparin coating were implanted in the infrarenal aorta (diameter, 2 m m) of 40 Whistar rats. Animals survived 8 weeks after implantation. Gr aft patency, intimal thickness, and percentage of diameter stenosis we re determined by light microscopy at the proximal respectively distal anastomosis and in the middle of the graft. Uncoated grafts showed a p atency rate of 70% for ePTFE and 60% for polyurethane grafts. Heparin- coated grafts showed a patency rate of 100% for ePTFE and 90% for poly urethane grafts, Intimal hyperplasia was observed in all grafts mainly at the anastomosis site. Intimal wall thickness and percentage of ste nosis were significantly more pronounced in the polyurethane than ePTF E grafts (P<0.01), Heparin coating significantly reduced overall graft thrombosis (P<0.05) but had no significant effect on intimal hyperpla sia. Conclusions-Small grafts show a high rate of graft thrombosis and an enhanced intimal hyperplasia. ePTFE grafts show significantly less intimal hyperplasia and percentage of stenosis than polyurethane graf ts. Heparin coating significantly reduced graft thrombosis but had no significant effect on intimal hyperplasia. Thus, heparin coating seems to be beneficial for graft patency, and ePTFE appears to be superior to polyurethane as graft material.