Clinical Study of Aneurysm Exclusion Using PTFE Encapsulation of Nitinol Stents

The Arizona Heart Institute is respectfully submitting this protocol for a feasibility study utilizing the endoluminal grafts constructed of PTFE encapsulated nitinol stents. The study is intended to evaluate the use of this unique device in the treatment of aortic aneurysmal disease. The stent graft is made by laminating a PTFE "jacket" around nitinol stents which act as structural and fixation supports. Both materials have an extensive history of use in various types of implanted devices. CT scans and angiography or 3D computer imaging, and possibly IVUS imaging will be used to choose the sites for placement of the devices and to assure precise deployment.

In comparison to the conventional surgical approach, endoluminal stent-graft techniques for repair of abdominal aortic aneurysms (AAAs) offer the advantages of a minimally invasive procedure with lower morbidity and perhaps cost reduction. The Arizona Heart Institute has a long history in the area of endoluminal grafting for treatment of aneurysms and occlusive disease. Endoluminal sleeves principally using ePTFE and both stainless steel and nitinol stent structures have been studied using commercially available materials customized for particular pathologic situations. As the technology advances however, sophisticated engineering beyond the capabilities of our institution was required.

The proposed project originates because of the potential to escalate the combination of ePTFE and stents to a higher level of performance in aneurysm exclusion procedures. Current data reflect several deficiencies in approved exclusion devices. Migration, types I, II and III endoleaks and continual aneurysm expansion are clear predictors for potential ruptures. Increased complications associated with the initial peri-procedural deployment as devices are released on a broader scale have been observed. In order to address these problems, the Arizona Heart Institute has engaged EndoMed engineering to design the endoluminal graft to repair abdominal aortic aneurysms. We believe this will result in a positive step forward in the technology to exclude aneurysmal disease less invasively.

The endoluminal stent-graft is composed of multiple nitinol stents which are encapsulated in expanded Polytetrafluoroethylene (ePTFE). The stents are composed of a Z-shaped, performed nitinol wire, which is crimped together with a stainless steel sleeve to form the circular frame of the graft. This frame is then encapsulated between two thin sheets of laminated PTFE. The proximal end of the endoluminal stent-graft is made in two configurations. One is a completely encapsulated graft where the PTFE covers the entire device. The other has an open stent segment (bare wire configuration) that allows the open stent region of the graft to be placed across the orifice of the renal, mesenteric, or internal iliac arteries without obstructing antegrade blood flow. The device will be available in a straight tube, aortomonoiliac or bifurcated design.

Once the endoluminal stent graft is built, a 4 French guidewire dilator is placed through the center of the graft and the assembly is compressed into a high density polyethylene (HDPE) cartridge for ease of intraluminal delivery. The endoluminal stent-graft is then placed in two Tyvek pouches and sterilized using Hydrogen Peroxide.