Cryopreserved venous allografts: effects of immunosuppression and antiplatelet therapy on patency and function

Experiments were designed to determine the function of the endothelium and smooth muscle in cryopreserved and fresh canine saphenous vein allografts.

Reversed interposition saphenous vein grafts were implanted into the femoral arteries of two groups of dogs: group 1 received one freshly harvested saphenous vein allograft and group 2 received one cryopreserved saphenous vein allograft. The contralateral femoral artery in each group was replaced with a freshly harvested autogenous saphenous vein. Animals received oral cyclosporine alone (n = 3) or in combination with aspirin (325 mg/day; n = 20).

Four weeks after surgery, none of the cryopreserved grafts was patent in the group treated with cyclosporine alone. All grafts were patent in animals treated with cyclosporine and aspirin. At 4 weeks, blood flow through cryopreserved allografts was significantly greater than in freshly harvested allografts. Platelet deposition was comparable in cryopreserved and freshly harvested allografts immediately after implantation and at 4 weeks. Rings cut from the grafts were suspended for the measurement of isometric force in organ chambers. alpha-Adrenergic agonists and endothelin caused concentration-dependent contractions in fresh autografts and allografts. After submaximal contraction with prostaglandin F2 alpha in these same grafts, calcium ionophore and thrombin caused relaxations in rings with endothelium, and nitric oxide caused relaxations in rings without endothelium. Cryopreserved allografts did not respond to any of the agonists tested. Histologic examination of the tissue indicated smooth muscle cells in cryopreserved grafts; evidence of rejection was observed in all allografts.

These results indicate that cryopreserved allografts remain patent with antiplatelet and immunosuppressive therapy in spite of loss of functional smooth muscle.