PENETRATING MICROPORES INCREASE PATENCY AND ACHIEVE EXTENSIVE ENDOTHELIALIZATION IN SMALL-DIAMETER POLYMER SKIN COATED VASCULAR GRAFTS

This article points to the importance of penetrating micropores throug h the graft wall to minimize thrombosis and to enhance endothelializat ion in small diameter polymer skin coated vascular grafts. Four types of spongy polyurethane-polydimethylsiloxane vascular grafts (PUG) fabr icated by a spray, phase-inversion technique, 1.5 mm inner diameter, 1 .5-1.9 cm in length, were implanted end-to-end in the infrarenal aorta of 26 adult rats. Some had a continuous inner skin and a hydraulic pe rmeability (HP) of 0 ml/min/cm(2)/120 mmHg (PUG-S-0). Some had an inne r skin with varying amounts of isolated penetrating micropores and a m ean hydraulic permeability of 11 (PUG-S-11), 37 (PUC-S-37), or 58 ml/m in/cm(2)/120 mmHg (PUG-S-58). Twelve PUC-S-0, 6 PUG-S-11, 4 PUG-S-11, and 4 PUG-S-58 were evaluated between 2 hr and 3 months after implanta tion. All PUC-S-0 occluded soon after implantation. The PUG that had a HP of more than 11 ml/min/cm(2) showed acceptable patency. However, e ndothelialization was limited to anastomoses in patent PUG-S-11. In co ntrast, the patent PUG-S-37 and PUG-S-58 were largely endothelialized. In all patent grafts at 3 months, numerous host cells had migrated, a nd newly formed capillaries were seen in the voids of the graft wall, which appeared moderately to highly cellular. In conclusion, it appear s that penetrating micropores through the graft wall increase patency and that a highly porous structure is needed to achieve extensive endo thelialization in small diameter polymer skin coated vascular grafts.