Flow patterns and preferred sites of intimal thickening in bypass-grafted arteries .

AIM: In bypass-grafted arteries, anastomotic intimal hyperplasia develops more markedly at the distal junction than the proximal one. It is likely that it arises from the difference in flow patterns at these two sites. Therefore we have studied the relationship between the flow patterns and precise locations of wall thickening specific to the particular vessel.

METHODS: In total 30 bypass-grafting procedures were carried out on the femoral arteries of dogs with 10 autologous common carotid arteries and 20 saphenous veins. The vessels were harvested at 3 months after operation, and precise locations of intimal thickening and characteristics of the flow such as flow patterns and distributions of fluid velocity and wall shear stress were studied in detail.

RESULTS: At the proximal anastomosis, a large recirculation zone was formed only at the inlet of the partially or totally occluded host artery, whereas at the distal anastomosis, it was formed at both the floor of the host artery and the toe of the bypass in most vessels, and the former was connected to the latter, extending the region of disturbed flow to lateral walls of the host artery. Wall thickening was found mainly in these regions occupied with slow secondary and recirculation flows where wall shear stress was very low.

CONCLUSION: The flow at the distal anastomosis is more disturbed and complex than that at the proximal anastomosis. This difference in flow pattern that determine the region of low wall shear stress might explain why intimal hyperplasia develop more markedly at the distal junction.