The influence of aneurysm size on anatomic suitability for endovascular repair

Abstract

Objectives: It has been proposed that the threshold for repair of abdominal aortic aneurysms (AAAs) suitable for endovascular repair (EVAR) be lowered. A critical step in this pathway is determining whether smaller AAAs are more likely to be anatomically suitable for EVAR; that is, whether suitability is lost as the AAA grows.

Methods: Patients who underwent ultrasound (US) imaging for asymptomatic AAAs at the University of Rochester Medical Center between January 1, 2003, and January 31, 2007, were identified. All those who had an abdominal/pelvic computed tomography (CT) scan ≤ 3 months of the US imaging were identified. CT scans were reviewed using predefined criteria to assess anatomic suitability for conventional EVAR (ie, without consideration of debranching).

Results: Of 3005 aortic US studies performed during this period, 221 had CT scans showing infrarenal aneurysms. Of these, 168 patients (76%) were candidates for EVAR and 52 (24%) were not, most commonly due to a short neck (40; 77% of excluded). Size measured by CT scanning (mean, 53 ± 11 mm) averaged 4 mm larger than by US imaging (mean, 49 ± 10 mm; r(2) = 0.66; P < .0001). Aneurysm size measured by CT scanning (P < .0001) or US imaging (P < .0001) correlated with anatomic suitability for EVAR. Mean sizes for those suitable were 52 ± 9 mm by CT and 48 ± 7 mm by US imaging, whereas mean sizes for those not suitable were 58 ± 10 mm by CT and 53 ± 8 mm by US imaging. Receiver operating characteristic curve analysis demonstrated that an US cutoff of 4.87 mm best predicted anatomic suitability (86.2% if smaller, 64.8% if larger), whereas a CT cutoff of 57.0 mm best predicted suitability (84.7% if smaller, 63.2% if larger).

Conclusions: Aneurysm size measured by CT averaged 4 mm larger than by US imaging. Larger aneurysms are less likely to be anatomically suitable for EVAR, but the rate of suitability does not appreciably decrease until the aneurysm measures 49 mm by US imaging or 57 mm by CT scanning. This implies that waiting until the aneurysm reaches currently accepted size criteria for repair does not result in "missing the window" for EVAR; in other words, just as many patients are anatomically suitable for EVAR at currently accepted size cutoffs than if earlier intervention had been done.