IP051. Atrophy of the Aneurysm Wall: Observations From Secondary Expansion After Endovascular Aneurysm Repair With Type II Endoleak∗

Abstract

Abdominal aortic aneurysm (AAA) has an age-dependent prevalence of 2% to 11% and is a leading cause of death in men aged >65 years if it is not treated surgically. Endovascular aneurysm repair (EVAR) is performed in up to 80% of elective and 90% of ruptured cases. Although reducing perioperative, early, and midterm outcomes and complications rates, the procedure is associated with specific complications requiring close follow-up, especially endoleaks. Type II endoleaks occur in up to 30% after EVAR; however, aneurysm sac expansion is rare. In this study, we investigate the aneurysm wall morphology in secondary expanding human AAA samples after EVAR due to persistent endoleak type II in comparison to nonaneurysmatic control aortas and AAA samples. Samples were acquired from the aneurysm sac during retroperitoneal ligation of the feeder vessel in a cohort of nine patients. Control tissues included 42 AAAs and 11 control aortas. Hematoxylin and eosin staining and immunohistochemistry for CD3/4/31/68 and Ki67 were performed for morphologic analysis and characterization. Terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling assays allowed quantification of apoptotic cells. Reverse transcription-polymerase chain reaction was used to quantify gene expression and Western blot to quantify proteins. Secondary expansion after EVAR was approximately 17% during 21 ± 12 months before operation. The sac wall after expansion shows significant thinning of the intima-media layer. This is accompanied by a scarcity of cells, with only little chronic inflammation left compared with AAA samples. Macrophages are seen in abundance, and matrix metalloproteinase expression is significantly upregulated. Relevant apoptosis is not noticed. Fibrous tissue is reduced, and a collagen turnover to different subtypes is noted in comparison to nonaneurysmatic control aorta and AAA. This is the first study examining aneurysm sac morphology after EVAR with persistent type II endoleak. Atrophy and proteolysis suggestive of structural weakening are observed and have to be considered indications for follow-up and treatment of this frequent EVAR complication.