SS25. Prevalence, Risk Factors, and Clinical Impact of Intraprosthetic Thrombus Deposits After Endovascular Aneurysm Repair

Abstract

The objective of this study was to define the prevalence, evolution, and clinical relevance of the intraprosthetic thrombus deposit (ITD) after endovascular aneurysm repair (EVAR). Patients treated with EVAR from 2009 to 2017 for abdominal aortic aneurysm were retrospectively considered. Patients with at least one postoperative computed tomography angiography (CTA) study performed after a 3-month follow-up were included. Postoperative medical therapy (antiplatelet or oral anticoagulant) was recorded. Aortoiliac anatomic characteristics were measured on preoperative CTA images, whereas structural and dimensional endograft features were extracted from instructions for use. ITD was defined as intraendograft thrombus with minimum thickness of 2 mm, longitudinally extended for a minimum of 4 mm; it was assessed on all postoperative CTA images. Primary end points were freedom from ITD occurrence, risk factors for ITD, and evolution of ITD. Secondary end points were the prevalence of overall and ITD-related thromboembolic events (TEEs; main body or limb occlusion, distal embolization) during follow-up and their correlation with ITD. There were 221 patients (mean age, 76 ± 7 years; male, 94%) included. Deployed endografts were aortobi-iliac 96%, aortouni-iliac 3%, aortic tube 1%, Dacron 90%, and expanded polytetrafluoroethylene 10%. Mean follow-up was 30 ± 25 months. Overall ITD prevalence was 36% (80/221). At 6, 12, 24, and 48 months, overall estimated freedom from ITD occurrence was 86%, 80%, 60%, and 52%, respectively (Kaplan-Meier analysis). At Cox univariate analysis, postoperative medical therapy had no influence on ITD. Aortoiliac anatomic risk factors for ITD were larger neck diameter (P < .001), severe neck thrombus (P = .043), higher percentage of sac thrombus (P < .001), and hypogastric occlusion or coverage (P = .040); endograft risk factors were proximal diameter ≥30 mm (P < .001), longer main body (P = .002), Dacron fabric (P = .025), and higher ratio between main body area/gate areas and main body area/distal iliac areas (P < .001 and P < .001, respectively). At Cox multivariate analysis, independent risk factors for ITD were larger neck diameter (P = .003), higher percentage of sac thrombus (P = .005), and longer main body (P = .028). During follow-up, ITD disappeared in 14 cases (18%). Overall TEE prevalence was 4% (8/221), and overall estimated freedom from TEE occurrence at 6, 12, 24, and 48 months was 99%, 99%, 95.3%, and 94.1%, respectively (Kaplan-Meier analysis). TEE was ITD related in five of eight cases (63%). No statistical correlation was found between ITD and TEE. ITD is a frequent event after EVAR. ITD occurrence is strictly correlated with proximal neck dimension, preoperative sac thrombus, and length of endograft main body. No statistical correlations between ITD and TEE are proved.