Preoperative relative abdominal aortic aneurysm thrombus burden predicts endoleak and sac enlargement after endovascular anerysm repair

Abstract

Background: Endoleak and sac growth remain unpredictable occurrences after EVAR, necessitating regular surveillance imaging, including CT angiography. This study was designed to identify preoperative CT variables that predict AAA remodeling and sac behavior post-EVAR.

Methods: Pre- and postoperative CT scans from 136 abdominal aortic aneurysms treated with EVAR were analyzed using M2S (West Lebanon, NH) software for size measurements. Preoperative total sac volume and proportion of thrombus and calcium in the sac were assessed. Sac change was defined as a 3-mm difference in diameter and a 10-mm3 difference in volume when compared with preoperative measurements. Univariate analysis was performed for age, gender, AAA size, relative thrombus/calcium volume, device type, presence of endoleak, and the effects on sac size.

Results: Gender, device type, age, AAA size, and percent calcium were not predictive of sac change post-EVAR. Increased proportion of thrombus on pre-EVAR resulted in a greater likelihood of sac shrinkage (P=0.002). Patients with aneurysms that grew on postoperative CT scan had less sac thrombus on pre-EVAR (mean 27.5%) than patients without evidence of endoleak (mean 41.9%, P<0.0001). Only 2 of 30 patients with >50% pre-EVAR thrombus developed endoleak. A>50% thrombus burden resulted in endoleak in significantly fewer patients (6.7%) compared with those who had <50% thrombus (43.1%).

Conclusions: The proportion of thrombus on preoperative CT may predict sac behavior after EVAR and development of an endoleak. Greater than 50% thrombus appears to predict absence of endoleak after EVAR. Aneurysms with large thrombus burden are less likely to grow and may require less vigilant postoperative surveillance than comparable AAA with relatively little thrombus.