In vitro thrombogenicity test of materials used in arterial prostheses. Comparison of fibrin deposition from blood on glass polystyrene and arterial prostheses.

Coagulation rates in fresh, normal, venous blood was investigated when a given volume of blood was allowed to contact various materials of equivalent surface area, at 22 degrees C, without disturbance. The coagulation rate was determined indirectly by measuring residual thrombin-clottable fibrinogen in cell-free supernatants after arresting coagulation at fixed time intervals with a Ca++-chelating type of anticoagulant and comparing the thrombin-clottable fibrinogen content of the test samples with control samples of blood anticoagulated immediately after venipuncture. In glass containers, after initial formation of the clot, progressive fibrin formation, measured by the rate of disappearance of thrombin-clottable fibrinogen, was found to take place as a gradual and linear progressive process not complete at 30 min after venipuncture with blood stored undisturbed at 22 degrees C. Various graft materials in tubular form were prepared to ensure equivalent blood surface contact. These were investigated for their influence on fibrinogen to fibrin conversion of fresh venous blood in a 15-min period at 22 degrees C. Fibrin formation was greatest in microvel pre-treated with clotting blood and decreased in the following order: microvel, woven Dacron, knitted dacron and Gore-tex. Gore-tex showed by far the least thrombogenicity of all the tested graft materials. We discuss our reasons for making our measurements under non-flow conditions and the reason for measuring fibrinogen to fibrin conversion rather than measuring platelet deposition on the various surfaces.