Venous endothelium of experimental arteriovenous fistulas in rabbits.

Since hemodynamic factors have been implicated in the localization and pathogenesis of atherosclerosis, the effect of hemodynamic stress on endothelium was investigated. The endothelium of the inferior vena cava of 24 rabbits with aortocaval fistulas was stained in situ and examined by the Hautchen technique at postoperative intervals ranging from 1 to 50 weeks. Cell counts revealed that, in the anastomosed vein of the fistula, an initially high frequency of abnormal cells decreased 3-12 weeks postoperatively but rose again within 20—50 weeks to levels significantly higher than those in either normal venous endothelium or sham-operated veins. An originally high mitotic index at 1—2 weeks decreased with time but still remained significantly larger than that observed in sham-operated rabbits. In most rabbits with arteriovenous shunts, a small area of the inferior vena cava near the fistula was devoid of endothelium, covered with a thin deposit of mural thrombi, and considered to be a jet lesion. The findings demonstrate that hemodynamic factors can cause endothelial injury, increased turnover of endothelial cells, and formation of multinucleated endothelial cells characteristic of regenerating endothelium.