We compared graft outcome between two types of a novel
composite three-layer carp-collagen-coated vascular graft in
low-flow conditions in a sheep model. Collagen in group A
underwent more cycles of purification than in group B in order to
increase the ratio between collagen and residual fat. The grafts
were implanted end-to-side in both carotid arteries in sheep
(14 grafts in 7 sheep in group A, 18 grafts in 9 sheep in group B)
and artificially stenosed on the right side. The flow in the grafts
in group A decreased from 297±118 ml/min to 158±159 ml/min
(p=0.041) after placement of the artificial stenosis in group A,
and from 330±164ml/min to 97±29 ml/min (p=0.0052) in
group B (p=0.27 between the groups). From the five surviving
animals in group A, both grafts occluded in one animal 3 and 14
days after implantation. In group B, from the six surviving
animals, only one graft on the left side remained patent
(p=0.0017). Histology showed degradation of the intimal layer in
the center with endothelization from the periphery in group A
and formation of thick fibrous intimal layer in group B. We
conclude that the ratio between collagen and lipid content in the
novel three-layer graft plays a critical role in its patency and
structural changes in vivo.
The geometric shape of the distal anastomosis in an infrainguinal bypass has an influence on its durability. In this article, we compared three different angles of the anastomosis with regard to the hemodynamics. Three experimental models of the distal infrainguinal anastomosis with angles of 25°, 45°, and 60° respectively were constructed according to the similarity theory to assess flow in the anastomoses using particle image velocimetry and computational fluid dynamics. In the toe, heel, and floor of the anastomosis that correspond to the locations worst affected by intimal hyperplasia, adverse blood flow and wall shear stress were observed in the 45° and 60° models. In the 25° model, laminar blood flow was apparent more peripherally from the anastomosis. In conclusions, decreasing the
distal anastomosis angle in a femoropopliteal bypass results in more favorable hemodynamics including the flow pattern and wall shear stress
in locations susceptible to intimal hyperplasia.
Hemodynamics in the distal end-to-side anastomosis is related to early development of intimal hyperplasia and bypass failure. In this study we investigated the effect of diameter ratios between the target artery and the bypass at three different angles of the connection. The pulsatile flow field was visualized using particle image velocimetry in transparent models with three different angles of the connection (25°, 45°, 60°) and the diameter ratio between the bypass and the target artery was 4.6 mm : 6 mm, 6 mm :
6 mm, and 7.5 mm : 6 mm. Six parameters including location and oscillation of the stagnation point, local energy dissipation, wall shear stress (WSS), oscillatory shear index, spatial and temporal gradient of WSS and their distribution in the target artery were calculated from the flow field. In the wider bypass, the stagnation point oscillated in a greater range and was located more proximal to the anastomosis. Energy dissipation was minimal in a wider bypass with a more acute angle. The maximum WSS values were tree times greater in a narrow bypass and concentrated in a smaller circular region at the floor of the anastomosis. The oscillatory shear index increased with wider bypass and more acute angle. The maximum of spatial gradient of WSS concentrated around the floor and toe of the anastomosis and decreased with more acute angle and wider bypass, the temporal gradient of WSS was stretched more towards the side wall. Greater bypass to target vessel ratio and more acute anastomosis angle promote hemodynamics known to reduce formation of intimal hyperplasia.