Efficiency of an external support to reduce lipid infiltration into venous grafts: In vitro evaluation

Excessive distension of venous grafts due to arterial pressure enhances the convective water transport (filtration flow) through the vessel wall, and thus might affect the infiltration of macromolecules such as lipoproteins. In this paired experimental study, filtration velocities were measured at 100 mm Hg for canine jugular veins with or without external supports of expanded polytetrafluoroethylene (ePTFE) arterial prostheses. In addition, to assess the effect of filtration velocity on lipid infiltration or uptake, canine jugular veins were wrapped over half of their lengths with ePTFE arterial prostheses and perfused with dog serum containing ³H-cholesterol at a pressure of 100 mm Hg. At 100 mm Hg, the average filtration velocity of the wrapped jugular veins was 7.9 ± 1.3 x 10^-6 cmis whereas the average filtration velocity of the unwrapped veins was 27.3 ± 2.7 x 10^-6 cm/s (p < 0.005). Moreover, the unwrapped veins had a significantly higher uptake rate of labeled cholesterol than the wrapped veins (10.9 ± 7.3 x 10^-4 cm/h and 5.0 ± 1.6 x 10^-4 cm/h, respectively, p < 0.005). In conclusion, under arterial pressure, veins experience excessive distention, which leads to significant increases in both filtration flow and cholesterol uptake. An external wrap or support of ePTFE material protects veins from excessive distension and thus may prevent atherosclerosis in venous grafts by reducing cholesterol uptake.