Predictors of Abdominal Aortic Aneurysm Sac Enlargement After Endovascular Repair

Abstract

Conclusion: In the Unites States compliance with endovascular aneurysm repair (EVAR) device guidelines is low. Rates of post-EVAR aneurysm sac enlargement are high. Summary: Companies marketing EVAR devices measure technical factors such as delivery accuracy, sealing ability, and fixation strength in the laboratory. These measurements are used to generate instructions for use (IFU) that are packaged with each EVAR device sold in the United States. The randomized trials comparing EVAR with open aneurysm repair have used EVAR devices in accordance with IFUs. Many physicians may perform EVAR without adherence to IFUs. It is unknown how often EVAR is performed outside the IFU for the device and longer-term results of EVAR performed outside IFUs are unknown. However, a significant portion of late deaths after EVAR are due to aneurysm rupture (De Bruin JL et al, N Engl J Med 2010;362;1881-9, and Wyss TR, Ann Surg 2010;252;805-12) and aneurysm rupture after EVAR is linked with aneurysm sac enlargement. The authors sought to determine compliance with IFUs in EVAR placement over the last decade and to determine relationships between anatomic characteristics at baseline of aorta and iliac arteries and the subsequent incidence of aortic aneurysm sac enlargement after EVAR. The authors examined patients undergoing EVAR between January 1, 1999, and December 31, 2008, using a medical imaging repository at M2S, Inc. (West Lebanon, NH). The deidentified data on all patients in the prospectively acquired M2S database was used for those who underwent a CT scan before EVAR and had at least one CT scan after EVAR between 1999 and 2008 in the United States. Patients were excluded if they underwent an EVAR in the context of premarketing or postmarketing studies in which M2S served as a core imaging laboratory. Preoperative aorta iliac anatomic characteristics were reviewed for each patient. The specific endovascular device implanted was not available from this database. Morphologic measurements were therefore compared with the most liberal and most conservative published anatomic guidelines stated in manufacturer's IFUs. Primary outcome was post-EVAR aneurysm sac enlargement >5 mm. There were 10,228 patients included in the database and used for the study. Of these, 59% had a maximum abdominal aortic aneurysm diameter below the 55-mm threshold at which intervention is recommended over surveillance. Forty-two percent of patients had anatomy that met the most conservative definition of IFUs and 69% met the most liberal definition of device IFUs. The 5-year post-EVAR rate of AAA sac enlargement was 41%. Independent predictors of AAA sac enlargement included age >80 years, endoleak, aortic neck diameter >28 mm, aortic neck angle >60°, and common iliac artery diameter >20 mm. Comment: Some physicians placing EVAR devices may be acting in what some could consider an irresponsible fashion. In this study, most EVAR devices were placed in abdominal aortic aneurysms that were below the threshold for intervention justified by randomized trials. Even with the most liberal definition of IFUs almost one-third of devices were placed outside manufacturer's recommendations, and in this database, >40% of aortas treated with EVAR had aneurysm sac enlargement at 5 years. The data are disturbing and raise significant questions about aneurysm treatment in the United States and about long-term risk of aneurysm rupture in patients treated with EVAR in the United States. Physicians placing EVAR devices need to do better job of policing themselves. If not, one can be sure someone else will! One can only speculate that it won't take long for the malpractice attorneys to stumble on to this.