THE EARLY THROMBOGENICITY OF IMPREGNATED DACRON GRAFTS ASSESSED IN AN ARTIFICIAL CIRCULATION
The impregnation of knitted Dacron grafts with biodegradable protein removes the need for preclotting at implantation. The effect of such impregnation on the thrombogenic potential of these prostheses is, however, unknown. We have compared the early thrombogenicity of two impregnated knitted Dacron grafts - Hemashield ( collagen-impregnated Dacron, Meadox) and Gelseal (gelatin-impregnated Dacron, Vascutek) -with conventionally preclotted knitted Dacron in an artificial circulation. Fresh, heparinised human blood, containing 111Indium-labelled platelets, was circulated around identical twin circuits of silicone tubing by a Sarns roller pump at 180 ml/min and 120 mmHg. Into each circuit a different 15 cm × 8 mm type of graft material was mounted. Changes in platelet count, platelet aggregation to collagen, plasma haemoglobin and blood radioactivity were recorded and after 60 minutes of perfusion each graft was sectioned and counted for radioactivity prior to scanning electron microscopy (SEM) of the luminal surface. The mean graft radioactivity divided by the mean blood radioactivity yields a Graft Activity Index (GAI) allowing comparison of platelet deposition and thus thrombogenicity.RESULTS: (mean ± s.e.m.) 8 examples of each graftSEM confirmed these findings with preclotted Dacron having the highest platelet deposition. Both impregnated grafts produced significant early haemolysis within 4 minutes of blood contact. Our findings indicate that the early thrombogenicity of these impregnated grafts is significantly less than conventionally preclotted Dacron, (p< 0.01, Wilcoxon signed rank test), despite the early haemolytic phenomenon and that Hemashield grafts are less thrombogenic than Gelseal grafts. (p<0.05, Wilcoxon signed rank test)