To examine whether preoperative aneurysm thrombus volume correlated with abdominal aortic aneurysm (AAA) sac regression following endovascular aneurysm repair (EVAR).Clinical records and computed tomographic angiograms (CTAs) from patients undergoing EVAR from 2003 to 2008 were reviewed. Inclusion criteria for this study were available preoperative CTA images, >or=12-month follow-up with surveillance imaging, lack of re-intervention at 12 months, and treatment with commercially available devices. Patients with ruptured AAAs, those requiring an aortomonoiliac stent-graft, and clinical trial cases were excluded. Based on these criteria, satisfactory images and clinical follow-up were available in 100 patients (90 men; mean age 76.8 years, range 55-95). Preoperative CTAs were categorized as demonstrating "minimal," "moderate," or "severe" aneurysm thrombus load by 2 independent examiners blinded to clinical outcome. Percentage of the aortic cross-sectional area occluded by clot (% clot area) was calculated as [(total area) - (luminal area)]/(total area). Multivariate logistic regression analysis was performed to determine predictors of sac shrinkage at long-term follow-up.AAA thrombus was classified as minimal in 24%, moderate in 23%, and severe in 53%. Thrombus area averaged 11%+/-13%, 41%+/-14%, and 72+/-12% in each group, respectively. By multivariate analysis, minimal thrombus (OR = 1.47) and greater AAA diameter (OR = 1.3) were independent predictors of sac regression at 1, 6, and 12 months (all p<0.05). Presence of neck plaque and endoleak were also independent predictors of sac expansion (p<0.05). Patients with severe preoperative thrombus were less likely to demonstrate sac regression even in the absence of endoleak. Thrombus judgment (subjective) and percent clot area (objective) were strongly correlated (R = 0.82, p<0.05). Interobserver agreement on thrombus judgment was 86%.Thrombus burden on preoperative CTA is a strong independent predictor of sac regression following EVAR. If validated by prospective studies, relative thrombus burden should be incorporated into postoperative surveillance algorithms to define procedural success and optimize the timing and cost-effectiveness of cross-sectional imaging.
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