Clinical implications of non-contrast-enhanced computed tomography for follow-up after endovascular abdominal aortic aneurysm repair

Abstract

Background: There is growing concern over the long-term radiation exposure from serial computed tomographic (CT) scan follow-up after endovascular aneurysm repair (EVAR) of abdominal aortic aneurysms (AAAs). Screening for endoleaks with non-contrast-enhanced volumetric CT has been shown to significantly reduce radiation doses. We evaluated the use of NCT as the primary method of follow-up after EVAR of AAAs.

Methods: Our institutional post-EVAR CT protocol consisted of contrast-enhanced CT angiography (CTA) 1 month after repair, followed by NCT at 3 or 6 and 12 months, and annually thereafter. At each follow-up scan, immediate 3-dimensional volume analysis was performed. If the volume change was <2%, NCT follow-up was continued. If the volume increased by ≥2% on nonenhanced images, contrast-enhanced CT was performed immediately to identify potential endoleaks. All images were reviewed by an experienced cardiovascular radiologist. End points included identification of endoleak, reintervention, and rupture.

Results: Over a 7-year period, 126 patients were followed. Serial CTA was performed in 59 patients, while 67 patients were followed with the NCT protocol. The mean follow-up was 2.07 years. There were no differences in age, sex, or initial aneurysm volume or size. There were 35 total endoleaks identified. Twenty of these were early endoleaks (<30 days post-EVAR). The remaining 15 leaks were late in nature (10 in the contrast group and 5 in the noncontrast group; P=0.17). NCT aneurysm sac volume changes prompted contrasted studies in all 5 late leaks. The mean volume change was 11.2 cm3, an average change of 5.88%. These findings were not significantly different than the late leaks found by routine contrast studies (8.9 cm3; 4.98% [P=0.58]). There were no delayed ruptures or emergent reinterventions in the NCT group.

Conclusions: Serial NCT appears to be safe and effective as the sole means of follow-up after EVAR for AAAs. AAA volume increases of ≥2% should prompt further contrast-enhanced CT imaging. Changes of <2% can be safely followed with serial NCT. This protocol requires dedicated cardiovascular radiologist involvement, and patients should be retained in the radiology suite until real-time image evaluation can be completed.