Anatomical and procedural predictors of type Ia and type III endoleaks after EVAR

Aim: Type Ia and Type III endoleaks are high-pressure failure modes of endovascular aneurysm repair (EVAR) that rapidly repressurize the excluded aneurysm sac but arise through different mechanisms. Type Ia reflects proximal seal-zone failure, whereas Type III reflects modular disconnection, component overlap failure, or graft-fabric failure. This study evaluated distinct risk profiles for these urgent subtypes after elective EVAR.

Material and Methods: This retrospective single-center observational study included 383 consecutive eligible patients who underwent elective EVAR for fusiform infrarenal abdominal aortic aneurysm between 2016 and 2024 and had preoperative and postoperative computed tomography angiography with at least 1 year of follow-up. Morphometric and three-dimensional measurements assessed proximal neck anatomy, aneurysm burden, thrombus burden, iliac morphology, and available procedural-complexity markers.

Results: The cohort included 356 male patients (93.0%) and 27 female patients (7.0%). During 33.2 ± 21.2 months of radiological follow-up, Type Ia endoleak occurred in 16 patients (4.2%) and Type III endoleak in 21 patients (5.5%). Type Ia endoleak was independently associated with conical proximal neck morphology, neck–sac angulation > 60 degrees, neck thrombus, and neck calcification, with adjusted odds ratios of 16.89, 5.72, 4.22, and 21.28, respectively. Type III endoleak was associated with longer aneurysm morphology, greater thrombus burden, higher thrombus-to-aneurysm ratio, iliac tortuosity, and iliac aneurysm involvement. The strongest Type III signals were thrombus-to-aneurysm volume ratio > 52%, aneurysm length > 139 mm, and thrombus volume > 118 cm³, with areas under the receiver operating characteristic curve of 0.880, 0.836, and 0.783, respectively.

Conclusion: Type Ia and Type III endoleaks showed distinct mechanism-specific risk profiles. Type Ia was primarily a hostile proximal-neck phenomenon, whereas Type III was associated with larger and longer aneurysm morphology, thrombus burden, iliac tortuosity, and iliac aneurysm involvement. Because device-specific variables and multivariable Type III modeling were unavailable, Type III findings should be interpreted as hypothesis-generating anatomy-device interaction signals rather than definitive independent predictors. Mechanism-specific assessment may support individualized EVAR planning and surveillance.