A histologic comparison of experimental microarterial end-in-end (sleeve) and end-to-end anastomoses.

Twenty-five microvascular end-in-end and 21 end-to-end anastomoses were performed on the central arteries (diameters 0.8 to 1.2 mm) of rabbit ears. The appearance of longitudinal specimens taken after intervals of 1 to 2 hours and 1, 3, 7, 14, 30, and 90 days was studied microscopically. Between 1 to 2 hours and 14 days, all end-in-end anastamoses showed considerable narrowing of the telescoped segment, and platelets had accumulated at the sleeved vessel end. The vascular walls of the telescoped segment were thickened distally, and the internal elastic laminas were folded in the lingitudinal direction due to contraction. Extensive loss of endothelium was observed both around sutures and distally in the telescoped segments. The stenosis initially noted in telescoped vessels gradually decreased due to atrophy of the medial layers in the double vascular walls. Following the organization of the platelet aggregates, subsequent endothelialization was completed between 7 and 14 days. After 2 weeks, neointimal hyperplasia was frequently found at the sleeved vessel end. In the early postoperative period, platelets covered exposed subendothelial structures and sealed defects in the vessel walls of all end-to-end anastomoses. During the first few postoperative weeks, the medial layers disintegrated and were replaced by increasing fibrosis. Reendothelialization was completed between 7 and 14 days, whereafter gradual intimal hyperplasia became significant.(ABSTRACT TRUNCATED AT 250 WORDS)