Design and manufacture of two experimental test benches for the in vitro assessment of a method to perform in situ fenestration of stent grafts Nicholas P. Lagermana, Timothy K. Chung, Ph.D.a, Mohammad H. Eslami, M.D.b,c, David A. Vorp, Ph.D.a,b,c,d,e,f,g Department of Bioengineering, bDivision of Vascular Surgery, University of Pittsburgh Medical Center, cDepartment of Surgery, d Department of Cardiothoracic Surgery, eDepartment of Chemical and Petroleum Engineering, fMcGowan Institute for Regenerative Medicine, g Center for Vascular Remodeling and Regeneration a
Nicholas Lagerman is a bioengineering student originally from Reading, Pennsylvania. He is continuing in the field of medical device design because of his love for biology and design.
Nicholas P. Lagerman
David A. Vorp, Ph.D.
David A. Vorp, PhD, is the Associate Dean for Research at the Swanson School of Engineering. He is a professor of Bioengineering, with secondary appointments in the Department of Cardiothoracic Surgery, the Department of Chemical and Petroleum Engineering, and the Clinical and Translational Science Institute at the University of Pittsburgh.
Significance Statement
There are two primary methods of abdominal aortic aneurysm (AAA) intervention that minimize risk of rupture: open surgery and endovascular aortic repair (EVAR). Fenestrated endovascular aortic repair (FEVAR) is a specialized EVAR procedure that utilizes a patient-specific stent graft to allow blood flow into visceral arteries. Nearly 80% of AAA repairs consist of EVAR or FEVAR [1] as their respective mortality rates are significantly lower than open surgery. FEVAR costs almost 3 times more than standard EVAR and requires substantial time to intervention because a fenestrated stent graft is custom-made for each patient [2]. The ability to create fenestrations in stent grafts during procedures would likely decrease cost and time to intervention. Our work develops two test benches that aid in the development of a novel device for detecting orifices in AAA geometries and creating in situ fenestrations in stent grafts.
Category: Device Design
Keywords: abdominal aortic aneurysm, test bench, modular perfusion phantom, 3D printing, fiber optic wire, infrared, fenestration. Abbreviations: Abdominal aortic aneurysm (AAA), endovascular aortic repair (EVAR), fenestrated endovascular aortic repair (FEVAR), computer-aided design (CAD) 44 Undergraduate Research at the Swanson School of Engineering
Abstract
This project focuses on the production of two experimental test benches that will be used in parallel towards the development of a novel in situ fenestration device: 1) An in vitro abdominal aortic aneurysm (AAA) phantom to deploy the sensing technology developed in parallel, and 2) A testing block to determine the feasibility of bending fiber optics for the sensing of orifices in the AAA geometry. This was accomplished by designing and generating AAA models, a perfusion chamber, and a fiber optic test block. Three complex geometries (juxtarenal, pararenal, and suprarenal) were modeled using computer-aided design (CAD) software and 3D printed for the perfusion phantom using an elastic resin to simulate the aortic wall’s elasticity. A perfusion chamber to house the models and the connected flow system was designed to allow for the models to be modular. A testing block consisting of fiber optic wire channels with five bending angles and six radii was designed and 3D-printed for the fiber optic test bench. An infrared emitter and receiver circuit with an analog voltage output were placed at opposite ends of the test block to measure the amount of infrared light being transmitted through a fiber optic wire. Both the bend angle (p = 0.135) and bend radius (p = 0.523) tests demonstrated that there was no significant difference in the voltage output between the variations in angles and radii. There is no evidence that the bend radius or angle would influence signaling in the detection of orifices.
1. Introduction
An abdominal aortic aneurysm (AAA) is an enlargement of the abdominal portion of the aorta. Rupture of the aorta may occur if the untreated aneurysm continues to grow in size, and 60% of people will die before reaching the emergency room [3]. To prevent rupture, clinicians usually intervene with one of two: open surgery and endovascular aortic repair (EVAR). There are close to 30,000 AAA repairs that occur annually, and approximately 80% of AAA interventions are EVAR [1] since it is both less invasive and has a lower mortality rate (1.5% compared to 12%) than open surgery [4]. EVAR is performed by inserting a catheter sheath into the femoral artery through a small incision located near the groin [4]. Then a catheter that houses a radially compressed stent-graft is inserted through the sheath. For standard sized grafts, an aneurysm with a minimum neck size of 10 mm (between the aneurysm and renal arteries) is required to properly deploy and anchor the stent-graft to reinforce the vessel wall, whereby preventing rupture [5]. However, there are AAA with complex geometries (juxtarenal, pararenal, suprarenal) which require a specialized fenestrated stent-graft that is deployed and anchored superior to the renal arteries and requires the re-perfusion of blood into the visceral arteries (renal, superior mesenteric artery and celiac) through the use of branching stent-grafts [2]. Therefore, fenestrated endovascular aortic repair (FEVAR) uses a highly customized patient-specific stent-graft to restore blood flow and provide the anchoring needed to prevent migration. There
