Objective: Data on complex abdominal aortic aneurysms (cAAAs) are scarce in Portugal. The authors aimed to assess the outcomes of endovascular and open surgical repair (OSR) for cAAAs using the Portuguese National Registry of Vascular Procedures, which is a prospective population based registry covering most of Portugal's vascular centres.

Methods: This retrospective cohort study included patients treated for intact cAAA (juxtarenal, pararenal, or complex infrarenal necks outside instructions for use [IFU] for endovascular aneurysm repair [EVAR]). Patients were stratified by surgical technique (OSR, fenestrated and branched [FB-EVAR], or EVAR with adjuncts and or outside IFU). The primary endpoints were 30 day adverse events (AEs) and major adverse events (MAEs). Secondary endpoints were death, failure to rescue, and practice patterns. Outcomes were assessed using inverse probability weighting.

Results: From 2019 to 2023, 293 patients were identified and treated in 16 centres with a median caseload of 11 (range 1 - 93, of which OSR 0 - 19; EVAR 0 - 34, and FB-EVAR 0 - 40). Endovascular strategies were performed in 67.9% (32.7% FB-EVAR; 35.2% EVAR). Compared with OSR, the endovascular group was older, with more frequent pulmonary comorbidities. Compared with EVAR, patients having FB-EVAR were younger and more likely to have had a previous aortic repair. Compared with OSR, EVAR had a lower risk of AEs (adjusted odds ratio [aOR] 0.17, 0.08 - 0.40) and MAEs (aOR 0.10, 0.04 - 0.29). Similarly, FB-EVAR had a lower risk of AEs (aOR 0.44, 0.21 - 0.91) and MAEs (aOR 0.42, 0.19 - 0.91). Non-significant differences in mortality rate (aOR 0.40, 0.11 - 1.25) and failure to rescue (aOR 1.70, 0.33 - 8.87) were observed. Increased morbidity following FB-EVAR was noted in low volume centres (33.3% vs. 12.3%, p = .040). One year survival and secondary interventions (available for 45.5% of cases) were comparable between strategies.

Conclusions: Nationwide data on the treatment of cAAA revealed significant variability in practice. Endovascular strategies were generally associated with improved early outcomes compared with OSR, but one year outcomes were comparable. These results should be interpreted with caution, considering the likelihood of bias in treatment selection.