Partially bioresorbable vascular grafts in dogs

Previous studies have shown the effectiveness of partially resorbable arterial prostheses in the rabbit. This study compares these same compound prostheses with commercial graft materials in the dog. Conduits 4 mm inner diameter X 50 mm in length were woven from composite yarns containing 69% polyglactin 910 (PG910)/31% polypropylene or containing 70% polydioxanone/30% polypropylene. Nonresorbable controls were woven Dacron and expanded polytetrafluoroethylene (ePTFE). Baseline platelet aggregometry to 10(-5) mol/L adenosine diphosphate was performed. Seventy prostheses were implanted into the aorto-ilac positions, and the prosthesis/tissue complexes were harvested serially from 2 weeks to 1 year. Explanted specimens were photographed and fixed for light microscopy and for scanning and transmission electron microscopy. Results showed no aneurysms or perigraft hematomas. Overall patency for the PG910/polypropylene grafts was 18 of 20 (90%) and for polydioxanone/polypropylene was 19 of 22 (86%). For Dacron and ePTFE, 13 of 19 (68%) and 6 of 11 (54%) remained patent at time of explantation. The partially resorbable grafts, as a group, had significantly greater patency than the control grafts (p less than 0.03). Platelet aggregometry was not predictive of graft patency. Histologic analysis of the partially bioresorbable groups showed inner capsules (IC) composed of myofibroblasts and collagen beneath confluent endothelialized surfaces by 1 month. Kinetics of IC formation paralleled the rates of resorption of the resorbable components. IC cellularity and thickness were greater than those within Dacron or ePTFE. This study suggests an enhanced transinterstitial endothelial cell and myofibroblast ingrowth into the ICs of partially resorbable grafts and shows the effectiveness of these prostheses in the dog.