[Influence of flow disturbance on an anastomotic intimal hyperplasia: experimental and clinical study]

Experimental and clinical studies were made of the localization and morphology of anastomotic intimal hyperplasia (AIH) at the end-to-side anastomosis in relation to flow disturbances. In vitro experimental findings showed that boundary layer separation (BLS) became prominent as proximal outflow segment (POS) flow increased. An aorto-right iliac bypass was performed on 30 dogs using 22 Biografts, 3 EPTFES and 5 Dacron grafts. Distal end-to-side anastomoses were made at 3 different angles, i.e., 30 degrees (Group I), 90 degrees (Group II) and 150 degrees (Group III). BLS was likely to occur at the toe in Group I because POS flow exceeded 50%, while not in Group III. Up to 35 months observation, AIH was noted to develop at the toe 36% in Group I, 25% in Group II but in none in Group III. Thirty five reconstructions using Biograft in which angiography was performed later than 6 months postoperatively were chosen for clinical study. Invariably in all cases of AIH occurring following a femoropopliteal bypass, severe stenosis was noted to occur at the toe and heel of the distal end-to-side anastomosis. In conclusion, a disproportionate increase in POS flow was considered a likely cause of marked BLS and, consequently, an important precipitating cause of AIH. When POS flow exceeds 50%, a distal anastomosis dividing flow distribution should be considered as a salvage operation of potential usefulness.