Impact of Abdominal Aortic Aneurysm Sac Shrinkage on All-cause Survival and Long-term Sac Behavior, up to 5 Years After Endovascular Aortic Repair with a Low-profile Device

Abdominal aortic aneurysm sac shrinkage measured on computed tomography (CT) images 1 year after 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 scans and ultrasound (US) images, respectively as well as long-term, and all-cause survival between patients with and without sac shrinkage up to five years after EVAR. This is a retrospective, single-center, cohort study of 241 consecutive patients treated with the Zenith Alpha abdominal graft (Cook Medical Inc., Bloomington, Ind) from October 15, 2015, to September 30, 2018. Data were extracted until August 1, 2021. Maximum diameters were measured on preoperative and 1-year postoperative CT angiogram and US scans, and on yearly US scans thereafter. All patients with a 1-year postoperative US measurement were included in the study. A difference of <5 mm between 1-year postoperative and preoperative diameter defined sac stability. Sac shrinkage was defined as a decrease of ≥5 mm, and sac growth was defined as an increase of ≥5 mm. All 241 patients underwent preoperative CT scans, and 177 patients underwent preoperative US examinations. Only 188 patients had a postoperative US diameter and, of these, 174 patients also had a 1-year postoperative CT scan. 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% confidence interval, 68%-88%), and patients without sac shrinkage, 68% (95% confidence interval, 57%-80%; P = .29), up to 4 years after initial categorization (Figure). Sac behavior 1-year post EVAR was preserved at 5 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 4 years (Table II). There was a considerable difference in sac behavior between CT scan and US examination 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 one-half remained stable and 26% displayed sac growth in 4 years.Table IThe difference in sac behavior between imaging modalities 1 year after endovascular aortic repair with a low-profile deviceSac changeaShrinkStableGrowthTotalCT37 (21)111 (64)26 (15)174US82 (47)79 (45)13 (7)174CT, Computed tomography; US, ultrasound.Values are number (%).aSac change=difference between the one-year postoperative diameter and the preoperative diameter. CT diameters were compared with CT diameters, US diameters were compared with US diameters. Shrinkage ≥5 mm decrease. Stable ≤5 mm difference. Growth ≥5 mm increase. Open table in a new tab Table IISac behavior up to 4 years after initial categorization and 5 years after endovascular aortic repairInitial categoryCategory change over 4 yearsaRemaining in initial category 5 years post-EVARbGrowth123 (25)75Stable8823 (26) to growth16 (18) to shrinkage50Shrinkage848 (10)90EVAR, Endovascular aortic repair.aNumber of patients switching category during 4 years of ultrasound (US) surveillance.bPercentage. Open table in a new tab