COMPARISON OF THE DEPLOYMENT AND HEALING OF THIN-WALLED EXPANDED PTFESTENTED GRAFTS AND COVERED STENTS

This study evaluated the deployment and short-term healing of thin-wal led expanded polytetrafluoroethylene (ePTFE) stented grafts and covere d stents as endoluminal prostheses in normal canine aortas and in an a bdominal aortic aneurysm (AAA) model. Stented grafts consisted of a 7 cm length of 3 mm internal diameter ePTFE graft (Impra, Inc., Tempe, A riz.) with two P-188 Palmaz stents (Johnson & Johnson Interventional S ystems, Warren, N.J.) deployed along the inner surface of the ends of the graft to secure the prosthesis to the arterial wall. Covered stent s were fabricated by placing a 3.7 cm length of 3 mm internal diameter thin-walled ePTFE graft over a P-394 Palmaz stent. Four covered stent s and four stented graft prostheses (two of each prototype in the norm al canine aorta and AAA model) were implanted in eight animals. One pr osthesis of each type in each model was removed at 30 days and one at 60 days. Prior to removal, prostheses were evaluated by CT scan, arter iography, and intravascular ultrasound imaging with values compared to those obtained when the prostheses were deployed. Gross inspection an d microscopic evaluation were performed at scheduled explantation. In general, the stented grafts were more difficult to accurately deploy. Healing and maintenance of long-term patency without significant lumin al obstruction or occlusion occurred in only one 30-day sample in a no rmal canine aorta. The 30-day stented graft specimen that had been imp lanted in an AAA and required the addition of a covered stent to seal a maldeployment of the distal segment was also patent. The 60-day sten ted graft in the normal canine aorta was occluded with narrowing of th e graft between the stents. The 60-day stented graft in the AAA was pa tent with one central fold and thrombus occupying approximately 20% to 30% of the lumen at this site. In contrast, the covered stent devices were less difficult to accurately deploy. All of the covered stent de vices were patent with well-incorporated surfaces. Deployment of cover ed stents was more accurate and less complicated compared to stented g rafts. All patent endoluminal prostheses and stent surfaces were well incorporated into aortic tissues. Problems with graft narrowing, foldi ng, and subsequent thrombosis occurred in the unstented segments of th e stented grafts. These preliminary findings support the further devel opment and use of completely supported (stented) devices as endolumina l prostheses.