"The rate of AAA sac enlargement was significantly higher in patients who underwent EVAR outside the IFU, regardless of whether lack of compliance was on the basis of conservative IFU, liberal IFU, or time-dependent IFU," the researchers stated. In addition, the rate of AAA sac enlargement was significantly greater in the group undergoing EVAR more recently (2004-2008), compared with the group who underwent EVAR in 1999-2003.
Multivariate analysis showed that the primary determinate of AAA sac enlargement was the presence of an endoleak on any postop CT scan (hazard ratio, 2.70). Additional significant predictors were a patient age of 80 years or older, an aortic neck diameter of 28 mm or larger, a neck angle greater than 60 degrees, and a common iliac artery diameter less than 20 mm.
Liberalization of the anatomical characteristics "deemed suitable for EVAR has occurred, and several of these factors, including aortic neck diameter, aortic neck angle, and common iliac artery diameter, were independently associated with aortic aneurysm sac enlargement. These observations raise the question as to whether such liberalization is justified with current device designs," the authors suggested.
"In this multicenter patient population, compliance with published EVAR device IFU guidelines was low, and post-EVAR aneurysm sac enlargement was high, raising concern for long-term risk of aneurysm rupture," the researchers stated. In addition, the liberalization in the anatomical criteria deemed appropriate for EVAR, observed throughout the study period, "was associated with worse outcomes."
The authors suggested the need for a prospective EVAR registry incorporating an independent imaging registry to define more precisely the specific aortic and iliac artery anatomy suitable for EVAR with available commercial devices.
Although this is the largest investigation of this question to date, the authors noted several limitations to their study, beyond the lack of device identification and information on secondary interventions. They pointed out that current research indicates that the standard definition of maximum diameter growth of 5 mm or more may be a less-sensitive criterion for sac enlargement than are volume assessments.
Their study indicated a greater need for concern for proper patient selection for EVAR, they concluded.
An improved understanding of these anatomical characteristics "will ultimately improve the effectiveness and durability of EVAR to protect patients against AAA rupture," Dr. Schanzer and his colleagues said.
The authors reported that they had no disclosures. The study was funded by the William Rogers Family Foundation.