Clinical Effectiveness of an Off-the-shelf Single REnal Scalloped sTent-graft for HOstile NEck Infrarenal Abdominal Aortic Aneurysm

Endovascular aneurysm repair (EVAR) is currently the preferred choice to treat the abdominal aortic aneurysms (AAA) with a feasible anatomy. However, approximately 40-60% of AAA patients presented unfavorable characteristics for EVAR, mainly due to a "hostile neck anatomy". In ''real-world'' clinical practice, up to 44% of EVAR cases are performed outside Instruction For Use (IFU) for an adverse neck anatomy6. Short (<15-mm), angulated (>60°), and wide (>28-mm) aortic necks are the main features concurring to the proximal HNA.

The recourse to standard EVAR is currently routine for patients who are not eligible for OR, with acceptable short- and mid-term outcomes, but the long-term durability of EVAR depends on maintaining proper sealing between the endograft and the aortic neck as well as the iliac arteries. HNAs demonstrated worse results when compared to "favorable" ones in terms of technical success (94% vs. 98%) and type-Ia endoleak rate (10% vs. 2%). The issue linked to an unfavorable anatomy can be addressed with more complex techniques, but these are limited by high production costs and considerable complexity .

TREO (Terumo Aortic, Inchinnan, Renfrewshire, UK; formerly Treovance, Bolton Medical, Sunrise, Fla) is a standard bifurcated, modular stent-graft that has shown compelling early- and mid-term results. It seems clear that several physicians are still looking for a feasible solution for HNA patients to keep the complexity of the procedure comparable to standard EVAR while yielding improved results.

Moreover, there is a lack of publications addressing the issue of mismatched take-off of the renal arteries (RAs). This morphology seems to influence the sealing length and could justify the introduction of dedicated devices. A recent study from our group currently under review for publication demonstrated that 25% of patients eligible for EVAR presented with mismatched RAs and that a dedicated device could improve sealing significantly. The study group sealing zone's length increased by about 25% when applying a hypothetical prototype with a single 10x10mm (wide x high) renal scallop. The same approach could be applied to the sealing surface with similar results. In the light of obtained results in selected patients, the use of a "single renal-scallop" custom-made device has been our standard of care.

The results will demonstrate whether the supra mentioned graft can the treatment of AAA with mismatched RAs in the real world. The effectiveness will be evaluated in terms of technical and clinical success.

The benefits could be relevant for the patients in terms of reduction of procedure-related adverse events such as endoleaks and related re-interventions. Furthermore, the use of custom-made standardized devices could significantly reduce costs for health care providers and in the future, it could be the base for an "off-the-shelf" endograft. Procedure-related complications were expected to be similar to standard EVAR and reduced in comparison with literature reporting adverse events in more complex techniques.

The present study aims to evaluate the clinical effectiveness of the custom-made standardized single renal scalloped stent-graft (Treo, Terumo Aortic) to treat infrarenal AAA. The final objective will be to employ the data obtained in this cohort for a future eventual development of an "off-the-shelf" device dedicated to patients with mismatched renal arteries. Such an endograft could keep the complexity of the procedure as similar as possible to standard EVAR while improving sealing.