Passive Sealing Stent-Grafts for Chimney Endovascular Repair: In Vitro Examination and a Japanese Single-Centre Retrospective Study

PURPOSE: Juxtarenal abdominal aortic aneurysms (JAAAs) present with a short infrarenal neck that does not permit standard endovascular aneurysm repair (EVAR). The AFX VELA cuff extension with its endoskeletal architecture may reduce type Ia endoleak (TIaEL) through passive sealing. We examined this hypothesis using a double-chimney benchtop model and a clinical cohort treated with VELA-based chimney EVAR (ChEVAR). MATERIALS AND METHODS: A benchtop model compared gutter leakage volumes among VELA, Endurant II and Excluder C3 (5 trials per device). A retrospective single-centre cohort (January 2018-April 2024) included consecutive JAAA patients undergoing VELA-based ChEVAR with ≥12-month follow-up. Postoperative computed tomographic (CT) morphometry compared seal-zone geometry across the 3 platforms. RESULTS: In the benchtop model, VELA showed a median gutter leakage of 5.0 mL/min (interquartile range [IQR], 4.0-11.0), whereas both comparators exceeded 500 mL/min and were right-censored. In the clinical cohort, 20 patients (55% male; median age 80.0 years) underwent ChEVAR for JAAAs with a median diameter of 53.5 mm and infrarenal neck length of 5.0 mm. Clinically successful sac exclusion was achieved in 19 of 20 patients (95%). Intraoperative TIaEL occurred in 5 patients: 1 major endoleak was sealed with adjunctive gutter coil embolisation, and 4 minor endoleaks resolved spontaneously on the 1-month CT angiogram. Over a median follow-up of 36.5 months, no persistent TIaEL was detected on follow-up imaging, and no chimney stent-graft (SG) occlusion occurred. One patient (5%) required an aortic-related reintervention for a type Ib endoleak. Estimated glomerular filtration rate (eGFR) decreased by ≥20% in 9 patients (45%), and 1 started dialysis at 4 years. On postoperative CT morphometry, relative gutter area was lowest with VELA, intermediate with Endurant II and highest with Excluder C3; circumferential apposition followed the inverse pattern. CONCLUSION: In the benchtop model, VELA produced consistently lower leakage than both comparators, with concordant CT morphometric evidence consistent with a passive sealing mechanism. In this cohort, VELA-based ChEVAR achieved clinically successful sac exclusion in 19 of 20 patients (95%) with no persistent TIaEL and no chimney SG occlusion. These findings support the feasibility of VELA-based ChEVAR when FEVAR is unavailable; multicentre prospective validation is required. CLINICAL IMPACT: Persistent type Ia endoleak (TIaEL) is a principal limitation of chimney EVAR (ChEVAR) compared with fenestrated EVAR (FEVAR). We report short-to mid-term outcomes of ChEVAR using the AFX VELA cuff extension, whose endoskeletal architecture is designed to promote passive sealing. Postoperative CT morphometry comparing the 3 devices (VELA, Endurant II and Excluder C3) showed a smaller relative gutter area and higher circumferential apposition with VELA, paralleling the benchtop pattern. VELA-based ChEVAR achieved clinically successful sac exclusion in 19 of 20 patients (95%), without persistent TIaEL detected on follow-up imaging. VELA-based ChEVAR appears feasible when FEVAR is unavailable; however, multicentre validation is required.