Aortic wall structural strengthening by intraluminal net prosthesis to arrest aneurysm progression and to prevent dissection and rupture

Abstract

The major limitation implicit in the endovascular procedures for aortic prosthetic substitution is that they cannot be used in those tracts of the aorta where important collateral branches originate (aortic arch, thoraco-abdominal tract, upper abdominal), that would be occluded by the prosthesis. In order to overcome this limitation we hypothesized the endovascular positioning of a prosthesis in the form of a wide mesh network that would be gradually and spontaneously covered by new intima and included in the aortic wall. The fabric framework linked to the aortic wall would then condition its significant, regular and uniform mechanical strengthening that fractionates and partially absorbs the centrifuge pulsatile stress of the bloodstream. The purpose of this paper is to report the results of the insertion of a braided Prolene net prosthesis in the first 7 cm of the descending aorta of ten swine. The animals were killed after 6 weeks, the substituted segment removed and aortic wall compliance measured under standardized conditions. The prosthesis was found entirely covered by new intima, well embodied in the aortic wall. The intercostal collateral included in the substituted segment was patent, as proved by bubble formation during underwater insufflation. Compliance of the prosthesis segment was significantly lower than that of the adjacent descending aorta. Histology showed a regular net prosthesis inclusion deep in the neo-intima layer. Present results indicate the technical feasibility of the procedure, achieving significant aortic wall strengthening without affecting the collateral (intercostal) circulation.

A mechanical device for aortic compliance modulation: In vitro simulation of aortic dissection treatment

“…This working hypothesis prompted us to explore an alternative acute intervention strategy. Existing experimental therapeutic approaches aim to slow or stop the dissection process by closing the aortic tears placement of intravascular stents or ''containment'' nets (Nazari et al, 1996;Eggebrecht et al, 2002;Kato et al, 1993;Inoue et al, 1999).…”

“…Active counterpulsation to provide mechanical ventricular support is generally used only in cases of extreme ventricular insufficiency, due to the risk of vascular wall damage associated with rapid balloon inflation. Development of alternative or synergistic therapeutic approaches is highly relevant (John, 2002;Fujita et al, 2003;Nazari et al, 1996;Mitchel et al, 1994;Eggebrecht et al, 2002;Kato et al, 1993). With the aim of developing a novel presurgical treatment option, we considered the possibility of introducing a passive counterpulsating damper into the dissected aorta in order to limit the physical stress associated with ventricular ejection and increase the aorto-ventricular pressure gradient in the diastolic phase.…”

New Approaches for Treatment and Prevention of Aortic Aneurysms

“…The experimental hypothesis is based on the fact that the net prosthesis positioned and maintained in stable contact with the aortic walls (A) is spontaneously, gradually covered by the neo-intima (B), invaded by fibroblasts and thus stably associated to the aortic wall. If the net mesh is appropriately dimensioned, it may be expected that the blood flow through the collateral branches is not affected (arrows) (from Nazari et al, 1996c) Fig. 22.…”

“…from Nazari et al 1996b) The structural properties of the aortic wall associated to the intraluminal net prosthesis rely on three factors (fig 24): 1) the structural properties of the net prosthesis, 2) the structural properties of the aortic wall, 3) the strength of the bonds between the aortic wall and the net prosthesis, based substantially on fibroblastic invasion of the net fabric and its permanent integration with aortic wall. Given the structural adequacy of the net prosthesis (polypropylene net prosthesis squared mesh 5x5 mm with a thread diameter of 0.5 mm sustaining a pressure of 300 mmHg (0.04 Nmm 2 ) is charged at 50% of its failure tension (Nazari at al, 1996b(Nazari at al, , 1996c and the mechanical effect of fractioning the aortic wall in the small area of the net meshes (fig 24, lower part), the important point of this model is the strength of the links biologically established between the threads of the mesh and the aortic wall tissues (point 3 in fig. 24) during the 4-6 weeks integration process.…”

Front Lines of Thoracic Surgery

“…The experimental hypothesis is based on the fact that the net prosthesis positioned and maintained in stable contact with the aortic walls (A) is spontaneously, gradually covered by the neo-intima (B), invaded by fibroblasts and thus stably associated to the aortic wall. If the net mesh is appropriately dimensioned, it may be expected that the blood flow through the collateral branches is not affected (arrows) (from Nazari et al, 1996c) Fig. 21.…”