Originally published by 2 Minute Medicine® (view original article). Reused on AccessMedicine with permission.

1. For large-vessel occlusion stroke, there were no clinical or safety differences in outcomes for patients undergoing mechanical thrombectomy between 6 and 24 hours after symptom onset, when the imaging modality was non-contrast CT compared to more advanced imaging, such as CT perfusion and MRI.

Evidence Rating Level: 2 (Good)

Due to the results of the DAWN and DEFUSE 3 trials, patients with large-vessel occlusion stroke can receive endovascular treatment if presenting 6-24 hours after symptom onset, which is an extended time period than was indicated previously. In these studies, magnetic resonance imaging (MRI) or computed tomography perfusion (CTP) were used as triage. However, these are advanced imaging modalities, and accessibility is limited. The purpose of this multinational cohort study was to determine if patients with proximal anterior circulation occlusion stroke, triaged with noncontrast CT (NCCT), would also benefit from endovascular mechanical thrombectomy (MT) in this extended time window, compared to those imaged with MRI or CTP. The hypothesis was that there would be no difference in outcomes between the two different imaging cohorts, and the main outcomes measured were scores at 90 days from the modified Rankin Scale (mRS) for Neurological Disability, 90-day functional independence (mRS scores of 0-2), symptomatic intracranial hemorrhage, and 90-day mortality. There were 1604 patients included in the study: 33.3% received NCCT imaging, 46.9% received CTP, and 19.8% received MRI. Individuals in the NCCT group had a higher median baseline National Institutes of Health Stroke Scale (NIHSS) score, higher rates of atrial fibrillation and hypertension, and were more likely to be transfers. The time from symptom onset to puncture was shorter in the NCCT group (median [IQR] of 10.4 [7.8-14.4] hours), compared to CTP (11.3 [8.4-15.2] hours) and MRI (12.4 [9.4-15.4] hours), with p < 0.001. As well, successful reperfusion rates were higher in the NCCT group (88.9%) compared to CTP and MRI (89.5% and 78.9% respectively, p < 0.001). For the 90-day mRS score, there was no difference between NCCT and CTP (adjusted odds ratio 0.95, 95% CI 0.77-1.17, p = 0.64) nor between NCCT and MRI (aOR 0.95, 95% CI 0.80-1.13, p = 0.55). There was also no difference for 90-day functional independence: the proportion of patients having an mRS score between 0 to 2 were 41.2% for NCCT, 44.3% for CTP, and 38.7% for MRI. Symptomatic intracranial hemorrhage was similar in all modalities (NCCT: 8.1%, CTP: 5.8%, MRI: 4.7%, p = 0.11) and 90-day mortality was also similar (NCCT: 23.4%, CTP: 21.1%, MRI: 19.5%, p = 0.38). Overall, this study demonstrated that there is no difference in clinical and safety outcomes for mechanical thrombectomy between 6 to 24 hours after symptom onset, when the imaging modality is with NCCT compared to CTP or MRI imaging.

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