VERY SMALL-DIAMETER POLYURETHANE VASCULAR PROSTHESES WITH RAPID ENDOTHELIALIZATION FOR CORONARY-ARTERY BYPASS-GRAFTING

Two types of spongy polyurethane-polydimethylsiloxane blend (Cardiotha ne 51, Kontron Instruments, Inc., Everett, Mass.) vascular grafts with an internal diameter of 1.5 mm were fabricated by a spray, phase-inve rsion technique. Low-porosity grafts with hydraulic permeability of 2. 7 +/- 0.4 ml/min per square centimeter and medium-porosity grafts with hydraulic permeability of 39 +/- 8 ml/min per square centimeter displ ayed good handling properties and suturability. Twelve straight low-po rosity grafts, 17 straight medium-porosity grafts (1.5 to 2.0 cm in le ngth), and one loop medium-porosity graft (10 cm in length) were impla nted by the same surgeon end to end in the infrarenal aorta of 30 male Sprague-Dawley rats. Three months after implantation, patency was 8% for low-porosity grafts (1/12) and 76% for straight medium-porosity gr afts (13/17). The loop medium-porosity graft was also patent. The sole patent low-porosity graft showed neointimal hyperplasia and incomplet e endothelialization. All but one of the patent straight medium-porosi ty grafts showed a glistening and transparent neointima with complete endothelialization and no anastomotic hyperplasia. The loop medium-por osity graft displayed endothelialization from each anastomosis and in many islands in the middle portion of the graft, totaling 47% of the l uminal surface by morphometric analysis. Thick mural thrombus, anastom otic hyperplasia, or aneurysm formation were not observed in any paten t medium-porosity graft. These data indicate that in the rat aortic re placement model it is possible to achieve patency and a high degree of endothelialization in very small-diameter prostheses of appropriate p orosity.