Lipid uptake across the wall of an expanded polytetrafluoroethylene vascular graft

Previous studies have shown that vascular grafts were prone to inducing an atherosclerosis-like phenomenon, thus possibly jeopardizing their performan ce. Furthermore, lipid retention, observed in most synthetic arterial prost heses explanted from humans, appears to have an important role in the progr ession of this atherosclerotic process, therefore hindering the healing pro cess and neo-intima formation of these synthetic conduits. The current stud y examined lipid concentration profiles across prosthesis membranes exposed to lipid dispersion under various transmural pressures, flaw rates, and du rations of exposure. It was demonstrated that the lipids rapidly permeated the prosthesis membrane, as lipid advection increased to a maximum, then st eadily decreased until the membrane became completely impermeable to the fl uid, The concentration of lipids within the grafts,vas monitored using FT-I R microspectroscopy, then correlated as a function of time in order to eval uate the mass transfer coefficients and lipid saturation concentration. Lip id sorption, as a function of time, was described by a mechanism taking int o account two first-order kinetic models. The lipids were first rapidly ads orbed onto the Teflon(R), potentially influenced by the strong affinity of these lipids for the highly hydrophobic polytetrafluoroethylene polymer. Th is affinity then enhanced the germination of the lipid deposits that filled in the prosthesis wall. For lipid retention as a function of the transmura l pressure and dow rate, no clear tendency was established. (C) 1999 John W iley & Sons, Inc.