Support of the aortic wall: a histological study in sheep comparing a macroporous mesh with low-porosity vascular graft of the same polyethylene terephthalate material

Abstract

OBJECTIVES: Wrapping with various materials was an early treatment for aortic aneurysms. Wrapping with low-porosity vascular grafts has been associated with graft migration and vascular erosion. An alternative is to use a macroporous mesh (MPM) made of the same polymer (polyethylene terephalate). We compared the histological outcome 1 year after wrapping sheep aortas with low-porosity grafts versus MPM fabrics. METHODS:The 2 different fabrics were wrapped around the aorta of 3 sheep. After 1 year the aortas were excised. The 2 wrapped segments of aorta were compared with each other and control aorta. Histological examinations and measurements were made of the layers of the aortic wall in 36 prespecified locations in each of the 3 sheep.RESULTS: Both fabrics were consistently surrounded by foreign body reaction and well-vascularized fibrosis. This was more pronounced with the low-porosity vascular graft material which was poorly incorporated and caused buckling at the transition between wrapped and unwrapped aorta. Conversely, the MPM was fully incorporated, resulting in a composite mesh/biological aortic wall. There was reduction of medial thickness with both materials but it was locally more extreme due to the corrugations in the vascular graft material. The findings were consistent between sampled locations and were similar in the 3 animals. CONCLUSIONS:The different porosity and rigidity of the materials influences their incorporation into the aortic wall. The incorporation of the pliable MPM precludes the complications of migration and erosion which are seen after wrapping with low-porosity prosthetic vascular graft material.

Mechano-biological adaptation of the pulmonary artery exposed to systemic conditions

“…7). These results are in line with our previous studies [27][28][29][30] . In contrast, a patient study examining the capacity of the macroporous material to withstand further dilatation of a weakened vessel wall does not mention atrophy of the SMC 31 .…”

“…Overall the meshes seemed well incorporated in all sheep, again in line with our previous studies [27][28][29][30] . Nevertheless, since the mesh material was not personalized for each surgery, some areas presented gaps between the mesh and the native wall which were filled with edema or proliferating, but inactive SMC.…”

Aortic Leaflet Stress in Surgery for Genetically Determined Root Aneurysms: Biomechanical Insights

“…We believe that their results and our own studies of flow and wall stress after personalized external aortic root support (PEARS) are complementary [2,3]. Our studies with sheep [4,5] show consistently that the PEARS mesh is incorporated into the aortic wall, which is stabilized and believed to be structurally as strong as a tube graft. We are particularly interested in their findings with respect to the aortic valve leaflets, which we have not studied ourselves.In the 1990s, when surgeons were achieving consistently good results with the modern Bentall, one of the unknowns in adopting valve-sparing surgery was whether the integrity of the leaflets could be relied upon.…”

What's in a wrap?

“…and reducing wall stress. 2,4 In an interim analysis in April 2020, there were no late dissections or ruptures over 16 years of follow-up in 321 patients undergoing PEARS. 5 After PEARS, the circumferential wall stress at the interface between supported and unsupported aorta increases, and the area of greatest expansion is shifted distally.…”

“…By serving as a barrier, they may impair the nutrition of the tunica media, potentially leading to dilatation adjacent to the wrap. 2 Furthermore, vascular grafts can cause buckling at the transition zone, possibly leading to wall erosion. 3 We have proposed an alternative approach to prevent aortic dissection and rupture by the use of personalized external aortic root support (PEARS).…”