Evaluation of a porcine internal mammary artery (No-React II) as a small-diameter conduit

Background. The patency of biologic small-diameter vascular grafts in the aortocoronary position is still unsatisfactory. Most of the studies suggest that xenografts are to be avoided as an aortocoronary bypass. Methods. The porcine internal mammary artery treated by the No-React II procedure was developed for use as an alternative coronary artery bypass conduit. The attempt of this study was to evaluate the patency and histologic changes of the porcine internal mammary artery in animals. Five calves underwent coronary artery bypass grafting with a porcine internal mammary artery graft to the right coronary artery. After euthanasia of the animals 103 days later, the samples of these grafts were studied morphologically for patency, structural changes, calcifications, and inflammatory and immunologic response. Results. One animal died during the procedure as result of acute thrombosis of the porcine internal mammary artery graft. In the other 4 animals all grafts became occluded. In the histologic sections of the grafts we noted multiple calcifications and a host-graft immunologic reaction (severe chronic rejection). Conclusions. The present study demonstrates a very poor experience with the porcine internal mammary artery (No-React II) conduit. We do not recommend this prosthesis for clinical use in humans.