The effect of thrombus on the vascular endothelium of arterialized vein grafts

Background It is known that vein grafts can be salvaged by clot removal, but patency rates are diminished. This study was designed to determine the effects of thrombus on vascular endothelium and the ability of the endothelium to recover normal function. Methods Thirty external jugular vein grafts were placed as bilateral femoral artery interposition grafts in 15 mongrel dogs and allowed to arterialize for a period of at least 12 weeks. Six control grafts were not exposed to thrombus (C-NT). Six other control grafts were exposed to thrombus for 7 days and removed, ie, allowed no in vivo recovery (C-T). The remaining 18 grafts in 9 canines were exposed to autologous thrombus for 5 days and then flow was restored. The right femoral graft was removed 7 days after thrombectomy and the left removed 30 days after thrombectomy. At the time of removal, the grafts were perfused with a balanced salt solution alone and then with arachidonic acid added to the same volume of the salt solution. Perfusates were collected at 5, 15, and 30 minutes. These perfusates were assayed for the presence of 6-keto-prosglandin F1α (6-keto-PGF11α), a metabolite of prostacyclin (PGI2). Over the 30-day recovery period, the amounts of 6-keto-PGF11α produced with and without arachidonic acid added were compared to assess endothelial response. Electron micrographs of the endothelium of all vein grafts were compared to the assay findings. Results When arachidonic acid was added to the perfusion system, there was a several fold increase in the production of 6-keto-PGF11α over baseline in all grafts allowed recovery. Grafts (C-T) that were allowed no in vivo recovery had no response to arachidonic acid. Ratios of 6-keto-PGF11α production with arachidonic acid stimulation to 6-keto-PGF11α production without stimulation were calculated to compare endothelial function. The electron micrographs showed the vascular endothelium to be severely injured after contact with thrombus, but recovered by 7 days. Conclusions This study suggests that the endothelium of canine vein grafts is injured by contact with thrombus for 5 days but can recover structure and function. This recovery is detectable at 7 days post-thrombectomy.