Platelet reactivity in human aortic grafts: a prospective, randomized midterm study of platelet adherence and release products in Dacron and polytetrafluoroethylene conduits.

Platelet-related phenomena at the blood-surface interface of randomly placed knitted Dacron (n = 6) and polytetrafluoroethylene (ePTFE) (n = 6) interposition aortic grafts were studied in patients undergoing abdominal aortic aneurysmectomy. Luminal accumulation of platelets was assessed by infusing indium-111-oxine (400 microCi) labeled autologous platelets and imaging grafts at 1 week, 3 months, and 6 months after surgery. Image analysis included an indium ratio technique (comparing aortic graft radioactivity to that of an iliac artery) and a red blood cell technetium subtraction technique (excluding blood pool radioactivity from graft radioactivity, with the heart or iliac artery serving as reference regions). Plasma levels of beta-thromboglobulin and platelet factor 4 were correlated with platelet accumulations on the aortic prostheses. Differences in graft radioactivity or platelet-release products were not evident 1 week after surgery. Three months after implantation, Dacron and ePTFE conduits exhibited 87% and 47% (p less than 0.05) more radioactivity with the indium ratio technique than the iliac artery. Similarly, increased Dacron compared with ePTFE graft radioactivity was noted using technetium subtraction techniques: 71% vs 30% with a heart reference and 26% vs 11% with an iliac artery reference, respectively. Increases in graft radioactivity correlated with increases in both plasma beta-thromboglobulin and platelet factor 4 at 3 months (r = 0.6 to 0.9; p less than 0.05 to 0.001 depending on the imaging technique used). At 6 months, differences did not persist. In fact, technetium subtraction techniques suggested less Dacron conduit reactivity. It is speculated that differences in platelet accumulation and activation associated with different graft substrates may prove clinically important.