Endoluminal aortic grafting: a preliminary animal study of graft-healing

Our purpose was to evaluate the placement, long term performance, and healing of a transluminally delivered endoluminal graft and attachment system, in an animal model using large adult sheep. Nineteen sheep in the weight range of 105-125 kg were entered into this study. Under fluoroscopic guidance in anesthetized animals, an endoluminal delivery system was inserted through a common femoral arteriotomy into the infrarenal aorta, and the graft and attachment system were deployed. Fixation of the proximal and distal ends of the graft to the aortic wall was achieved by hooks on the self expanding attachment system, and seated by balloon expansion. Explantation of the prosthesis was performed prior to euthanasia at 1-, 3-, and 6-month intervals. Aortograms were obtained before and after implantation and before explantation for evaluation of placement, patency, anastomotic seal, migration, and graft infolding. In situ gross examination of the prosthesis under anesthesia prior to sacrifice was performed in all animals. Histologic sections were obtained from both attachment sites ("anastomoses"), from the midgraft and hook insertion sites, and from normal aorta inferior and superior to the endoluminal prosthesis. Scanning electron microscopy was performed randomly on specimens derived from the superior and inferior anastomotic sites at each time point. Selected intervals of healing were 1 month (N=5), 3 months (N=5), and 6 months (N=8). One sheep was euthanized at 1 week due to paraplegia. At all intervals, all prostheses were patent, were well incorporated at the aortic wall-anastomotic sites, and were without mural thrombus. The attachment hooks penetrated the aortic adventitia in all animals. There was no graft migration. At one month, initial pannus formation covered the anastomoses and the entire luminal graft, yet the endothelial-like surface coverage was incomplete. At 3 months and at 6 months, the anastomoses and luminal surfaces displayed more uniform pannus and endothelial-like surface coverage. We conclude that this endoluminal delivery system, passed through a femoral arteriotomy, can effectively deploy an endoluminal graft with self expanding attachment system having consistent patency, secure fixation, and incorporation of the anastomoses with the aortic wall in this animal model.