The antithrombotic nature of vascular prosthetic pseudointima.

Morphologic functional, and biochemical studies were performed on pseudointima obtained from woven Dacron aortic prostheses harvested from eight dogs 2 to 3 years after placement. In vivo platelet reactivity with prostheses was assessed by serial 51Cr-platelet survival measurements which documented that platelet survival returned towards normal but never attained preoperative levels. The extent of luminal coverage of prosthesis with pseudointima of the time of harvest was 60.3% +/- 2.4%. Morphologic techniques, including conventional light microscopy, immunoperoxidase light microscopy for endothelial factor VIII-related antigen, and scanning and transmission electron microscopy, demonstrated that pseudointima was composed of endothelial cells of varying maturity lining mesenchymal tissue. Areas of the prostheses with poorly formed pseudointima containing exposed Dacron fibers were covered with exuberant, platelet-rich thrombi. Ability of pseudointima to produce prostacyclin was assessed by bioassay of platelet antiaggregatory activity and radioimmunoassay of 6 keto PGF1 alpha, a metabolite of prostacyclin. These experiments confirmed that pseudointima produced abundant prostacyclin, although not as much as native aortic tissue. These studies document that vascular prosthetic pseudointima is nonreactive with platelets, presumably because of prostacyclin generation.