IYSC13 - Impact of Abdominal Aortic Aneurysm Sac Shrinkage on All-cause Survival and Long-term Sac Behavior, up to Five Years After Endovascular Aortic Repair with a Low-profile Device

Objectives: Abdominal aortic aneurysm (AAA) sac shrinkage measured on computer tomography (CT) images one-year post endovascular aortic repair (EVAR) has been associated with higher all-cause survival compared with patients without sac shrinkage. This study aims to analyze both variation in sac behavior as measured by CT and ultrasound (US) respectively as well as long-term, and all-cause survival between patients with and without sac shrinkage up to five years after EVAR.

Methods: This is a retrospective, single-center, cohort study of 241 consecutive patients treated with the Zenith Alpha abdominal graft (COOK Medical Inc.) from October 15, 2015, to September 30, 2018. Data was extracted until August 1, 2021. Maximum diameters were measured on preoperative and one-year postoperative CTA and US scans, and on yearly US scans thereafter. All patients with a one-year postoperative US-measurement were included in the study. A difference of < 5 mm between one-year postoperative and preoperative diameter defined sac stability. Sac shrinkage was defined as a decrease of ≥5mm, and sac growth was defined as an increase of ≥5 mm.

Results: All 241 patients underwent preoperative CT, and 177 patients underwent preoperative US. Only 188 patients had a postoperative US diameter and of these, 174 patients also had a one-year postoperative CT. Sac change differed considerably between imaging modalities such that US displayed significantly more sac shrinkage (Table I). There was no statistically significant difference in all-cause survival between patients with sac shrinkage, 78% (95% CI 68-88), and patients without sac shrinkage, 68% (95% CI 57-80, p=0.29), up to four years after initial categorization (Figure 1). Sac behavior one-year post EVAR was preserved at five years for 90% of patients with sac shrinkage, 75% of patients with sac growth and 50% of patients with sac stability. Of the remaining patients initially categorized with sac stability (n=88), more (26%) developed sac growth than sac shrinkage (18%) in the following four years (Table II).

Conclusions: There was a considerable difference in sac behavior between CT and US with the latter categorizing significantly more sac shrinkage. There was no significant difference in all-cause survival between patients with and without sac shrinkage. Most patients with initial sac shrinkage/growth sustained this in all their follow-ups. In contrast, in patients with initial sac stability, only half remained stable and 26% displayed sac growth in four years.