Capillary and venule proliferation in the healing process of Dacron venous grafts in rats

A woven, noncrimped graft (made of Dacron and coated with an elastomer) that was 1.5 mm in diameter and 15 mm long was capable of replacing the vena cava in rats. The elastomer mixture consisting mainly of silicone rubber was necessary to bond the woven Dacron fibrils of the woven graft to prevent fraying at the anastomoses and bleeding through the interstices of the lightly woven, fairly high porosity (500) conduit. Sequential histologic studies showed that patency was associated with the ingrowth of small venules and the spreading of endothelial cells from each anastomosis toward the center. Small venules appeared in loose connective tissue, forming a pseudointima 12 days after grafting. This process occurred in the midportion of the graft before pannus endothelial growth covered the endothelial surface. Various thicknesses of the external polymer coat were studied for their influence on healing. None of the grafts developed a thrombus in these later studies, and regardless of the thickness of the external elastomer, endothelial resurfacing was complete at 30 days. However, the graft with the thinnest external elastomer coating had the best-formed vasa vasorum, and the intima at both the anastomoses and midportions of the graft was significantly thinner than intima found in grafts of other composition. We conclude that this woven Dacron polygraft provides a surface resistant to early thrombosis; that healing occurs mainly by pannus ingrowth, but external and interstitial factors are also important; and that properties inherent in the polygraft wall determine the size of the residual lumen.