Mechanical thrombectomy has drastically improved clinical outcomes of patients with acute ischemic stroke [1], [2], [3]. The standard methods for thrombectomy are retraction with a stent retriever (SR) alone or a direct aspiration first pass technique (ADAPT) using an aspiration catheter (AC) [4], [5]. Improving recanalization grades, shortening the time from onset to recanalization, and reducing intracranial hemorrhages (ICH) are necessary to improve outcomes [6], [7]. Currently, various combined techniques (CBTs) using an SR and AC have been performed to improve outcomes [8], [9], [10].

When performing a CBT, the AC is first navigated toward the occlusion site from a guide catheter placed in the cervical portion. The AC is selected based on its size (inner and outer diameter), navigability, durability, aspiration force, and flexibility depending on the occlusion site. Currently, many types of ACs are available, making it difficult to select an appropriate one for each case. While ACs with larger inner diameters provide better thrombus retrieval performance, they pose an increased risk of hemorrhagic complications [11]. Therefore, when selecting an AC with a lager caliber size for the occluded vessel, the use of a highly flexible AC may contribute to allow navigation to the proximal end of the thrombus without placing mechanical stress on the occluded vessel. Since few studies have examined the relationship between AC flexibility and clinical outcomes, we retrospectively examined it in patients undergoing first-line thrombectomy using a CBT.