The heparin neutralizing activity of venous and polyester aortic grafts

The distribution and variations of heparin neutralizing substances in venous and polyester grafts in the abdominal aorta of dogs were investigated and the results compared with those of normal arteries and veins. 1, 4 and 36 months after the operation the venous and polyester grafts were excised and dissected into three layers. The antiheparin activity of the different layers was then determined. In the early post-operative period, the antiheparin activity in the venous and polyester grafts is higher but later begins to fall so that its level 3 years after the operation approaches that of the various layers in the normal veins.