Endothelialization following end-to-end and end-in-end (sleeve) microarterial anastomoses. A scanning electron microscopic study.

Eighteen microvascular end-to-end and eighteen end-in-end anastomoses were performed on the central arteries (diameters 0.8-1.2 mm) of rabbit ears. Specimens taken after intervals of 1-2 hours and 3, 7, 14, 30 and 90 days were studied using a scanning electron microscope. At 1-2 hours platelets and to a minor extent erythrocytes and fibrin had accumulated in defects between the vessel ends on sutures and at the suture holes of all end-to-end anastomoses. This had also occurred at the distal end of the telescoped segment in all end-in-end anastomoses. At 3 days endothelial desquamation at anastomotic sites and clamp sites was found in both end-to-end and end-in-end anastomoses. The exposed subendothelial surface was covered with a carpet of platelets, and frequently numerous leucocytes were found. Between 3 and 7 days, new endothelial cells appeared at the junction between the vessels in end-to-end anastomoses and in all areas damaged by vascular clamps. At the ends of the sleeved segments reendothelialization was observed over platelet aggregates. Between 7 and 14 days neo-endothelialization seemed to be virtually completed in both types of anastomosis. In the vicinity of the anastomoses, the appearance of the new endothelium was frequently abnormal with irregularly formed cells. Characteristic clefts and holes were seen between these abnormal (pleomorphic) endothelial cells. Histological findings from the same vessel specimens show that areas with abnormal endothelialization correspond to segments with intimal hyperplasia. Such areas were found in specimens throughout the entire period studied.(ABSTRACT TRUNCATED AT 250 WORDS)