PPS-PEG surface coating to reduce thrombogenicity of small diameter ePTFE vascular grafts

Aims: Patency failure of small vascular synthetic grafts is still a major problem for coronary and peripheral revascularization. Thus, three new surface coatings of small synthetic grafts were tested in an acute pig model to evaluate their thrombogenicity (extracorporeal arterio-venous shunt) and in a chronic rat model to evaluate the tissue reaction they induced (s.c. implantation). Methods: In five domestic pigs (25-30 kg) an extracorporeal femora-femoral arterio-venous shunt model was used. The study protocol included first a non-heparinized perfusion sequence followed by graft perfusion after 10,000 UI iv heparin. Grafts were perfused for 3 and 9 min. The following coatings were tested on ePTFE grafts: poly-propylene sulfide (PPS) - poly-ethylene glycol (PEG) (wet and dry applications) as well as carbon. Two sets of control were used, one dry and one wet (vehicle only). After perfusion grafts were examd. by SEM for semi-quant. assessment (score 0-3) of cellular and microthrombi deposition. To assess tissue compatibility, pieces of each material were implanted s.c. in 16 Wistar rats. At 2, 4, 8, 12 wk four animals each were sacrificed for semi-quant. (score 0-3) histol. evaluation of tissue reaction. Results: In the pig model, cellular deposition and microthrombi formation increased over time. In non-heparinized animals, the coatings did not improve the surface characteristics, since they did not prevent microthrombi formation and cellular deposition. In heparinized animals, thrombogenicity was lowest in coated grafts, esp. in PPS-PEG dry (p