Lipid uptake in expanded polytetrafluoroethylene vascular grafts.
OBJECTIVE
The mechanisms of vascular prosthesis failure are reported to be associated, in part, with an atherosclerotic degenerative process that is related to an abnormal lipid infiltration. The lipid uptake in expanded polytetrafluoroethylene (ePTFE) vascular grafts was reproduced in vitro, and the effect of time on the permeability of these prostheses was studied.


METHODS
Water permeability tests were carried out under dynamic flow conditions at various hydrostatic pressures. Lipid uptake was simulated by circulating a phosphatidylcholine suspension inside an expanded Teflon prosthesis under pulsatile or continuous transmural pressure ranging between 80 mm Hg and 180 mm Hg, at a flow rate of 500 mL/min and 2000 mL/min, for a duration ranging from 2 hours to 1 month.


RESULTS
Water permeability tests indicated that under hydrostatic pressures of 180 mm Hg and 300 mm Hg, water percolated through the prosthesis wall after an exposure of 720 minutes and 75 minutes, respectively. After exposing the prostheses to the lipid dispersion under the various flow conditions, the fluid convection through the wall occurred. Preferential convection pathways with a constant periodicity were observed across the length of each prosthesis and were, therefore, associated with regularly spaced perforations depicted in the structure of the devices. Phospholipids gradually agglomerated within the prosthesis wall, allowing a restrictive molecular mobility. Infrared spectroscopy results indicated that the lipid uptake depended on the transmural pressure and time of exposure.


CONCLUSIONS
The occurrence of the membrane permeability may be associated with the dilatation and plastic deformation of the prosthesis. Lipid uptake occurs in ePTFE grafts after an aggressive kinetic process.
Vermette
P
P
Department of Chemical Engineering, Laval University, and Centre Hospitalier Universitaire de Québec, Québec, Canada.
Mantovani
D
D
Guidoin
R
R
Thibault
J
J
Laroche
G
G
D001807:Blood Vessel Prosthesis; D008055:Lipids; D010539:Permeability; D010713:Phosphatidylcholines; D011138:Polytetrafluoroethylene; D017550:Spectroscopy, Fourier Transform Infrared; D013535:Suspensions; D014867:Water
D008055:Lipids; D010713:Phosphatidylcholines; D013535:Suspensions; D014867:Water; D011138:Polytetrafluoroethylene