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Endovascular repair has become state of the art for treating thoracic and abdominal aortic aneurysms. However, complications such as endoleaks or the development of aortic neck dilatation, require lifelong surveillance and re-interventions. The extent to which structural vessel wall alterations during implantation of endovascular grafts are involved in the development of these complications is widely unknown. Therefore, the aim of this study was to characterize aortic vessel wall alterations during endovascular aortic repair in a porcine ex-vivo model.

A total of 18 endovascular stent-grafts were implanted in a thoracoabdominal porcine aortic flow model. Subsequently, histomorphological analysis, transmission electron microscopy and biomechanical analysis of the proximal sealing zone was performed.

While histological wall impairment was detected in only four specimens (22%), transmission electron microscopy revealed ultrastructural disruption in all specimens after EVAR. Transmission electron microscopy revealed a disrupted structure of elastic fibers with microtears and cavities supplemented by ruptured collagen fibers and disrupted integrity of vascular smooth muscle cells in all aortic specimens after stent-graft implantation. As a biomechanical correlate to ultrastructural aortic wall injuries, a significantly lower force at rupture (55.63±14.71 vs. 36.56±12.27 N, P=0.006) and elongation at rupture (22.23±5.39 vs. 17.13±5.34 mm, P=0.048) were observed in aortic specimens after stent-graft implantation.

Endovascular stent-graft implantation induces acute ultrastructural damage to the aortic wall, including elastic fiber disintegration, collagen disruption, and microdissections within the tunica media. These alterations were associated with reduced biomechanical stability. Whether this initial mechanical injury contributes to long-term complications such as aortic neck dilatation warrants further investigation.