Intimal integrity and fibrinolytic potential of reversed and in situ vein grafts

The improved patency rates of in situ vein grafts are attributed to better flow characteristics, anastomotic “fit,” and intimal preservation. This study compared the early changes in intimal morphology and fibrinolytic activity of in situ and reversed vein bypass grafts from mongrel dogs. Four to six centimeter in situ and reversed vein segments were used to bypass left and right femoral and internal carotid arteries, respectively. Heparin (100 U/kg) was administered before arterial clamping. Anastomoses were fashioned end to side and the intervening artery was ligated. Fifty-two grafts were harvested at day 1 (12 grafts), day 7 (16 grafts), day 14 (12 grafts), and 12 weeks (12 grafts). The veins were analyzed for histologic changes by light microscopy and scanning electron microscopy. The fibrinolytic activity of the grafts was assayed by the fibrin slide and fibrin plate techniques. There were no significant differences in morphology or fibrinolytic activity between the reversed and in situ grafts at any time period. These findings indicate that the improved patency rates associated with in situ grafts are not dependent on improved preservation of intimal structure or fibrinolytic activity.