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Conical Neck Morphology and Thrombus Burden are Associated with Neck Dilatation following Endovascular Aortic Aneurysm Repair (EVAR)
Gregory G. Westin, MD, MAS, Diego M. Ayo, MD, Sheila N. Blumberg, MD, Andrew R. Baxter, MD, Caron B. Rockman, MD, Neal S. Cayne, MD, Frank J. Veith, MD, Thomas S. Maldonado, MD.
NYU Medical Center, New York, NY, USA.
OBJECTIVES: The purpose of this study is to evaluate infrarenal aortic neck morphology and thrombus burden and their influence on patient outcomes and neck/sac behavior following endovascular aortic aneurysm repair (EVAR).
METHODS: We conducted a single institution retrospective review of consecutive EVARs performed for infrarenal AAA from 2004 to 2013. Only patients who had thin (1-4mm) cut pre- and post-operative CT angiograms available were included. We measured aortic neck length, diameter, and angulation, as well as aneurysm sac diameter. Neck shape was determined qualitatively to be ‘funnel’, ‘conical’, or ‘cylindrical’. Two independent radiologists performed volumetric analysis of neck thrombus burden at 5mm, 10mm, and 15mm below the renal arteries by subtracting the inner wall volume from the outer wall volume. Percent thrombus was calculated as volume of thrombus divided by volume of vessel at outer wall. Outcomes included type 1 endoleak, sac growth >5mm, and neck dilatation within the 15mm below the lowest renal artery. Mean follow-up was 24 months (1-118 months).
RESULTS: 46 patients met inclusion criteria (115 males, 78.8%; mean age of 74.7 +/- 8.2). Neck morphology was cylindrical in 54%, funnel in 11%, and conical in 35%. Mean thrombus volume was 32.5% at 15mm. Mean % oversizing was 15.7 +/- 8.7%. Type 1 endoleak was found in 4/146 patients (3%). Aortic sac growth occurred in 19/146 patients (13%). Neck morphology and thrombus burden were not associated with increased sac growth or the presence of type 1 endoleak. However, thrombus volume of >25% at 15mm was associated with significant neck dilatation (22.8% versus 77.2%, p<0.02). Conical neck morphology was also associated with significant neck dilatation (funnel: 3.6%; conical: 60.7%; cylindrical: 35.7%; P<0.01). Percent oversizing was not related to neck dilatation.
CONCLUSIONS: Patients with conical necks and >25% thrombus burden in the 15-mm seal zone appear to be susceptible to neck dilatation. While this does not appear to affect sac growth or risk for type 1 endoleak, these patients may warrant more vigilant surveillance or more liberal use of a more proximal sealing zone using fenestrated or chimney technology.
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