"In vitro" evaluation of the optimal degree of oversizing of thoracic endografts in prosthetic landing areas : A Pilot Study

• Objectives: The optimal degree of proximal thoracic endograft oversizing when aiming for durable sealing in prosthetic grafts in unknown. The aim of this study was to create an in vitro model for testing different oversized thoracic endografts in a reproducible and standardized manner, and subsequently determining the optimal oversizing range when planning procedures with proximal landing in prosthetic zones in the descending thoracic aorta or aortic arch.Materials and Methods: An in-vitro model consisting of a fixated 24mm polyethylene terephthalate (Dacron) graft sutured proximally and distally to two specifically designed 40mm rings, with four force sensing resistors attached at 4 equally distant positions and a USB camera attached proximally for photographic and video documentation was used for deployment of Zenith TX2 (Cook Medical, Bloomington, IN, USA) dissection platform endografts with diameters between 24 and 36mm. After deployment, ballooning with a 32mm compliant balloon was performed to simulate real life conditions. Assessment of oversizing included visual inspection, calculation of the valley areas created between the prosthetic wall and the stentgraft fabric, distance between stentgraft peaks, radial force exerted by the proximal sealing stent and the pull-out force necessary for endograft extraction.Results: A total of 70 endografts were deployed: 10x 24mm, 10x 26mm, 10x 28mm, 10x30mm, 10x32mm, 10x34mm and 10x36mm, with oversizing ranging between 0-50%. Two cases of infolding occurred with 50% oversizing. Valley areas increased from 8.79 ± 0,23 mm with 16.7% oversizing to 14.26 ± 0.45 mmÇ for 50% oversizing (p<.001). There was a significant difference in the pull-out force required for endografts <10% oversizing vs. 10% oversizing or more (p<.001), which reached a plateau at approximately 4 N after oversizing > 15%. The mean radial force of the proximal sealing stent was greater after remodelling with a compliant balloon (.55 ± .02 N vs .60 ± .02 N after ballooning (p<.001)). However, larger oversizing did not lead to an increase in the radial force exerted by the proximal sealing stent.Conclusion: The findings of this study offer additional insight into the mechanics of oversized stentgrafts in surgical grafts. In endografts with the z-stent design (TX2), oversizing below 16.7% resulted in reduced resistance to displacement forces, while oversizing > 50% was associated to major infolding in 20% of the cases. Long-term in vitro and in vivo testing are required to understand how these mechanical properties impact clinical outcomes of oversizing.

Subject headings

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Kardiologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Cardiac and Cardiovascular Systems (hsv//eng)

Keyword

Medicinsk vetenskap

Medical Science

Medicinsk vetenskap

Medical Science

Publication and Content Type

vet (subject category)

ovr (subject category)