Material Fatigue As a Cause of Infrarenal Aneurysm Rupture: A Word of Caution About the AneuRx Device

Christopher M. Chambers, MD, Luis A. Sanchez, MD, Patrick J. Geraghty, MD, Brian G. Rubin, MD, Michael A. Curi, MD, Eric T. Choi, MD and Gregorio A. Sicard
Vascular Surgery, Washington University School of Medicine, St. Louis, MO

Objectives: Endovascular grafts have to withstand significant longitudinal, compressive, and sheer forces that test the strength and stability of the materials used. Most endografts approved in the US have had some type of material fatigue. The AneuRx device has developed material failures, mostly suture breaks and focal nitinol fractures, generally not associated with negative outcomes. Aneurysm rupture is rare after EVAR, often associated with Type I endoleaks and/or graft migration, not material fatigue. We reviewed our experience to understand the association of material fatigue and aneurysm rupture.
Methods: From March 1996 through December 2005, 399 EVARs were performed using the AneuRx device with a mean follow-up of 29±12 months. The records of all patients treated were reviewed retrospectively including their routine follow-up CT scans. Six patients presented with a ruptured aneurysms (1.5%): 5 were treated with endografts and 1 refused treatment. Four patients had major material fatigue noted during follow-up (1%) including nitinol fractures, tears of the polyester material, or a combination of both.
Results: The 4 patients with major material fatigue presented with rupture(2) or increasing AAA size(2) at a mean follow-up of 48±8 months. One patient had a Type IA endoleak/graft migration while the other 3 had Type III endoleaks. 33 %(2/6) of the patients that presented with ruptured aneurysms had associated major material fatigue. No correlation was noted between material fatigue and initial AAA anatomy. All 4 patients had successful endovascular exclusion using AUI devices (2) or aortic cuff & endograft limbs for graft relining (2). The patients are doing well at a mean follow-up of 12±11 months.
Conclusions: Aneurysm rupture and major material fatigue associated with the AneuRx device are rare and are often late occurring events which are not associated with any specific preoperative AAA anatomy. While minor material fatigue (suture breaks) are fairly common and well described, they have not been associated with a poor outcome. Major material fatigue is clearly associated with adverse outcomes (AAA enlargement and/or rupture) and requires reintervention. Fortunately, these patients can often undergo successful secondary endovascular repair. Lifetime follow-up is critical after endovascular repair since device failure is not limited to the initial few years after EVAR and can be associated with significant complications.