Endovascular abdominal aneurysm repair (EVAR) is the standard treatment for abdominal aortic aneurysm (AAA), being less invasive than open surgical repair [1]. However, open surgical repair has mid- and long-term benefits due to increased aneurysm-related mortality and adverse events in EVAR [2]. Type II endoleak (T2EL) is the most common post-EVAR endoleak, resulting in the backflow of blood into the aneurysm sac from the inferior mesenteric artery (IMA), lumbar arteries (LAs), or other aortic side branches (ASBs). Late T2EL, persisting for more than 6 months, is associated with aneurysm enlargement, rupture, and reintervention post-EVAR [3,4]. Reintervention for T2EL is indicated if the aneurysm enlarges post-EVAR using various strategies, including transarterial and translumbar embolization. However, despite these efforts, up to 60% of aneurysms continue to expand even after embolization, requiring reintervention or open conversion [5,6].

Therefore, the use of pre-emptive transcatheter arterial embolization (P-TAE) of ASBs before EVAR has been suggested as a means to prevent T2EL after EVAR [7], [8], [9], [10], [11], [12], [13], [14], [15], [16]. A recent randomized controlled trial found that P-TAE of the IMA was effective in preventing T2EL and promoting aneurysm sac shrinkage post-EVAR [14]. Some studies have reported that P-TAE of LAs and the IMA reduced the incidence of T2EL. However, these results remain controversial because most studies were single-center, retrospective cohort designs. Additionally, the type of endograft used during P-TAE can impact the results. For instance, Endurant stent graft (Medtronic Vascular) is the EVAR device associated with a lower incidence of T2EL by comparison with other devices [17,18]. More robust data through multicenter prospective studies, utilizing a single EVAR device, is essential for accurately assessing the efficacy of P-TAE in preventing T2EL.

The purpose of this study aimed to evaluate the efficacy and safety of P-TAE for ASBs to prevent T2EL and aneurysm sac enlargement before EVAR using a single EVAR device, the Endurant stent-graft, as a prospective, single-arm, multicenter trial in Japan.