RR12. Changes in AAA Neck Morphology and Loss of Anatomic Suitability for EVAR during Surveillance: Does the ”Window of Opportunity” Close for Some Small AAAs?

Abstract

Growth of small abdominal aortic aneurysms (AAAs) is frequently associated with aortic neck and iliac artery (IA) changes during surveillance. The purpose of this study was to determine the effects of aortic neck and IA changes on anatomic suitability for endovascular aortic aneurysm repair (EVAR) during long-term follow-up, particularly of small AAAs with marginal neck morphology (length < 15 mm and diameter >28 mm). We studied 62 patients with small AAAs (diameter, 4 cm to 5.4 cm) under surveillance with long-term follow-up by CT angiography and 3D reconstructions. The mean follow-up duration was 36 months (interquartile range [IQR], 16-53 months). AAA morphology and changes were measured according to SVS reporting standards. Suitability for EVAR was determined by neck anatomy (diameter, length and angulations, thrombosis), IA morphology and all AAA angulations. The median age of the study cohort was 74 years (IQR, 65-77 years). Marginal necks were present in 22 (35%) small AAAs on initial CTA. Of these AAAs with marginal necks, 74% were considered suitable for EVAR. The median AAA diameter increased from 44.5 mm (IQR, 41-48) to 51.1 mm (IQR, 46-55). The aortic neck diameter increased from 23.0 mm to 25.9 mm (P=.001), whereas neck length decreased from 26.5 mm to 19.0 mm (P<.001). No significant changes in aortic and IA morphology/angulation occurred. Overall, the anatomic suitability for endovascular repair significantly changed during the study period (81% vs 69%; McNemar test, P<.001). Of note, 45% of AAAs with marginal neck morphology vs. 3% of those with adequate necks were not suitable for EVAR at the end of follow-up (P<.001). In fact, AAAs with marginal necks had a 17-fold increased risk of losing anatomic suitability for EVAR during surveillance (odds ratio, 16.8; 95% confidence interval, 4.0-69). Significant changes in aortic neck morphology and EVAR suitability occur during long-term surveillance of small AAAs. EVAR suitability is primarily affected in small AAAs with marginal neck morphology. Our data indicate that early elective EVAR for small AAAs with marginal necks is justified when this is the preferred treatment option, as ongoing surveillance in such patients may result in aortic neck changes that preclude future EVAR.