Penetrating micropores increase patency and achieve extensive endothelialization in small diameter skinned vascular grafts

Four types of spongy polyurethane-polydimethylsiloxane (Cardiothane 51TM) vascular grafts (PUG) fabricated by a spray, phase-inversion technique, 1,5 mm ID, 1,5 - 1,9 cm in length, were implanted end-to-end in the infrarenal aorta of 26 adult rats. Some had a continous inner skin and a hydraulic permeability (HP) of 0 ml/min/cm2/120 mmHg (PUG-S-0). Some had an inner skin with varying amount of isolated penetrating micropores and mean HP of 11 (PUG-S-11), 37 (PUG-S-37), or 58 ml/mim//cm2/120 mmHG (PUG-S-58). Twelve PUG-S-0, 6 PUG-S-11, 4 PUG-S-37 and 4 PUG-S-58 were evaluated by macroscopic and microscopic observations. Patency rates were as follows: PUG-S-0, 67% (2/3 - within 3 days), 0% (0/8 at 1-2 weeks), 0% (0/1 at 3 months); PUG-S-11, 0% (0/1) - within 3 days), 80% (4/5 - at 3 months); PUG-S-37, 100% (4/4 - at 3 months); PUG-S-58, 75% (3/4 - at 3 months); All PUG-S-0 occluded soon after implantation. PUG which had a HP of more than 11 ml/min/cm2 showed acceptable patency . Endothelialization, however were limited to anastomoses in patent PUG-S-11. In contrast , the patent PUG-S-37 and PUG-S-58 were largely endothelialized . In all patent grafts at 3 months, numerous host cells had migrated and newly formed capillaries were seen in the voids of the graft wall, which appeared moderately to highly cellular. In conclusion, it appears that penetrating micropores through the graft wall increase patency and that a highly porous structure is needed to achieve extensive endothelialization in small diameter skinned vascular grafts.