La chirurgie vasculaire avec effraction tissulaire minimale pour exclusion d'anévrisme : intérêts et limites des essais chez l'animal

Abstract

The Vanguad™ endoprotheses were implanted transluminally through the femoral route and deployed at the site of surgically created aneurysms in the thoracic or abdominal aortas of dogs for prescheduled periods of implantation of 1 week, 1, 2 and 3 months. The in vivo dimensional stability of the endoprothesis was confirmed by angiography after insertion and before the sacrifice and by macroscopic observations after retrieval. Histological and scanning electron microscopic (SEM) studies were performed to assess the healing sequence of the device. Microscopic studies of the textile components and surface chemical analysis of the Nitinol wires by electron spectroscopy for chemical analysis (ESCA) were undertaken, after specimen cleaning to remove adherent tissue, to detect structural modifications to the textile structure and to evaluate the bioresilience of the Nitinol. Analysis of the angiograms after implantation and before the sacrifice revealed that morphological changes such as sliding and compression of the metal structure occurred initially after deployment and during implantation. Thrombogenicity of the luminal surface of the endoprotheses was low but the healing was still incomplete after 90 days of implantation. The lack of stability of the metal structure may explain the migration distally and the poor healing of the device. ESCA analysis showed that a physiosorbed passivation layer covered the surface of the Nitinol wires masking the nickel (Ni) component of the alloy. Ion bombardments of the surface of the wires confirmed the presence of a contaminated layer composed of carbon and other elements followed by a highly oxidized titanium (Ti) layer, and then, by the Ti/Ni alloy. Although innovative, the minimally-invasive endovascular technique for the treatment of aortic aneurysms is still in its infancy. Significant improvements are required in terms of ease of handling, effectiveness, innocuousness, biostability and healing.