Biodesign: Engineering an aortic endograft explantation tool

Abstract

Endovascular aortic repair (EVAR) graft failure can be as high as 16% to 30% owing to endoleak, graft migration, or infection, often necessitating explantation, leading to potential morbidity (31%) and mortality (6.3%). Graft prongs frequently tear through the endothelium during explantation, leading to endothelial damage and subsequent fatal bleeding. The current standard of care involves different suboptimal techniques such as the syringe technique in which a cylinder is improvised by cutting a syringe in half and pushed over the graft hooks in a rotating motion, until covered for manual explantation. Because there is no commercially available product to address this shortcoming in graft explantation, we engage in the biodesign process to produce a functional explantation device. We designed and prototyped multiple potential solutions to remove EVAR endografts safely. Silicone tubing with EVAR endografts deployed in the lumen were used to simulate a grafted aorta and test each prototype. Prototypes were compared in their ability to meet design criteria including decrease in graft diameter, prevention of arterial dissection, ease of use, and decrease in procedure time. After determining the single best prototype, surgeon feedback was elicited to iteratively improve the original design. The most effective design uses a tapered lumenal geometry that decreases the EVAR graft diameter and uses stainless steel beads to prevent shear stress to the simulated aorta. A distal grip allows for easy single hand manipulation of the device, while a latching mechanism allows for smooth placement and removal over the endograft. After rigorous prototyping, our device proved feasible and effective for safe EVAR explantation, allowing this procedure to be performed safely.

Keywords: Abdominal aortic aneurysm; Aortic graft infection; Biomedical innovation; EVAR explantation; Open endograft explantation.

Fig 1

Axial view of computed tomography angiogram (CTA) demonstrating gas within the abdominal aortouni-iliac stent graft (red arrow).

Fig 2

(A) Preoperative views demonstrating patent superior mesenteric artery (red arrow). (B) Postoperative sagittal view of computed tomography (CT) scan demonstrating occlusion of the superior mesenteric artery (red arrow).

Fig 3

(A) Technical drawing and three-dimensional model of the device in (B) isometric and (C) cross sectional views.

Fig 4

Endovascular aortic repair (EVAR) struts collapsing from full 25 mm diameter to 7 mm and 9.5 mm.

Fig 5

Close up views of proximal leading edge with metallic beads.

Fig 6

(A) Pinching of an endograft device causes fixating struts to expand radially, complicating explantation. (B) Leading edge metal beads facilitate movement along the collapsing endograft. (C) A partially disassembled prototype mockup featuring (1) the metal pin acting as the key for device closure, (2) the distal device handle, and (3) the tapered interior diameter that assists in graft closure. (D and E) Additional views of the closed prototype mockup.