Abstract Body: Background: Computed tomography (CT) is globally recognized as the standard initial imaging modality for mechanical thrombectomy (MT) in large vessel occlusion (LVO). However, in Japan, many institutions prefer magnetic resonance imaging (MRI). This study aimed to evaluate and compare clinical outcomes between patients who underwent MT based on whether CT or MRI was used as the initial imaging modality, as documented in the K-NET registry.
Methods: The K-NET registry is a prospective collection of MT cases for LVO, involving 40 Japanese institutions. Data from 3,182 cases registered between 2018 and 2021 were analyzed. These cases were categorized into three groups: MRI alone (MRI group, n=1,265), CT alone (CT group, n=830), and both modalities (Combined group, n=1,087). The primary outcome measured was the proportion of patients achieving a modified Rankin Scale (mRS) score of 0-2 at 90 days post-procedure. Secondary outcomes included onset-to-door time (OTD), door-to-image time (DTI), door-to-puncture time (DTP), puncture-to-recanalization time (PTR), and the incidence of intracranial hemorrhage (ICH), symptomatic ICH, and mortality.
Results: The median ages were 77 years for the MRI group, and 79 years for both the CT and Combined groups. Initial NIHSS scores were lower in the MRI group (median 17) compared to the CT (19) and Combined (18) groups. The MRI group exhibited a significantly longer OTD (71 mins) than the CT (57 mins) and Combined (60 mins) groups. Conversely, DTI was similar across groups (14, 10, and 17 mins, respectively), while DTP was notably shorter in the MRI group (52 mins) compared to the CT (62 mins) and Combined (97 mins) groups. The MRI group also demonstrated a shorter PTR (37 mins) relative to the CT (53 mins) and Combined (56 mins) groups. While the MRI group had a higher overall incidence of ICH (21%), symptomatic ICH rates did not differ significantly across groups. The proportion of patients achieving an mRS score of 0-2 at 90 days was significantly greater in the MRI group (43%) compared to the CT and Combined groups (both 39%).
Conclusions: Patients in the MRI group were significantly younger and presented with lower NIHSS scores compared to those in the CT and Combined groups. Despite a longer OTD, the MRI group experienced shorter DTP and PTR, ultimately achieving better clinical outcomes at 90 days. However, the differences in baseline characteristics across the groups necessitate careful interpretation of these findings.