The pathogenesis of thrombosis in venous prostheses.

To evaluate the pathogenesis of thrombosis formation in synthetic venous grafts, the inferior vena cava of rabbits were replaced by woven Tetron (polyethylene terephtalate) grafts. Six animals were assigned as controls without medication (Group A), and 48 animals were randomly assigned to experimental groups as follows: ticlopidine hydrochloride (100 mg/kg/day) was administered orally from 5 days prior to operation to the end of the experiment (Group B); warfarin sodium (0.33 mg/kg/day) was given orally for the same period (Group C); and a combination of ticlopidine hydrochloride (50 mg/kg/day) and warfarin sodium (0.16 mg/kg/day) was administered for the same period (Group D). All the grafts in group A occluded within 3 h. All grafts harvested from groups B and D remained patent at least until the twenty-eighth day after grafting but the lumen was narrowed by intimal hyperplasia. Although the grafts from group C were patent at the seventh day, all grafts occluded with intimal hyperplasia on day 14 and day 28. The dry weight of thrombus in the graft in group B and group D was 39 +/- 3 mg and 30 +/- 2 mg, respectively on day 28. These figures were significantly lower than that of the control group 59 +/- 9 mg at 5 h after the initial heparinisation. Ultrastructural studies with scanning electron microscopy showed that the thrombus in the graft of the control group was composed of platelet aggregates anchored to synthetic fibres and of erythrocytes entrapped in the fibrin network. By day 7, in the groups modified with drugs, sheets of endothelial-like cells extended across both suture lines from the host stumps and extended to the middle of the graft thereafter. Light microscopy revealed that the initimal hyperplasia in groups B, C and D on day 28 were mainly composed of fibroblasts, myoblasts, collagenous fibres and micro-capillaries.(ABSTRACT TRUNCATED AT 250 WORDS)