Location-weighted versus Volume-weighted Mismatch at MRI for Response to Mechanical Thrombectomy in Acute Stroke.

Background A target mismatch profile can identify good clinical response to recanalization after acute ischemic stroke, but does not consider region specificities. Purpose To test whether location-weighted infarction core and mismatch, determined from diffusion and perfusion MRI performed in patients with acute stroke, could improve prediction of good clinical response to mechanical thrombectomy compared with a target mismatch profile. Materials and Methods In this secondary analysis, two prospectively collected independent stroke data sets (2012-2015 and 2017-2019) were analyzed. From the brain before stroke (BBS) study data (data set 1), an eloquent map was computed through voxel-wise associations between the infarction core (based on diffusion MRI on days 1-3 following stroke) and National Institutes of Health Stroke Scale (NIHSS) score. The French acute multimodal imaging to select patients for mechanical thrombectomy (FRAME) data (data set 2) consisted of large vessel occlusion-related acute ischemic stroke successfully recanalized. From acute MRI studies (performed on arrival, prior to thrombectomy) in data set 2, target mismatch and eloquent (vs noneloquent) infarction core and mismatch were computed from the intersection of diffusion- and perfusion-detected lesions with the coregistered eloquent map. Associations of these imaging metrics with early neurologic improvement were tested in multivariable regression models, and areas under the receiver operating characteristic curve (AUCs) were compared. Results Data sets 1 and 2 included 321 (median age, 69 years [IQR, 58-80 years]; 207 men) and 173 (median age, 74 years [IQR, 65-82 years]; 90 women) patients, respectively. Eloquent mismatch was positively and independently associated with good clinical response (odds ratio [OR], 1.14; 95% CI: 1.02, 1.27; P = .02) and eloquent infarction core was negatively associated with good response (OR, 0.85; 95% CI: 0.77, 0.95; P = .004), while noneloquent mismatch was not associated with good response (OR, 1.03; 95% CI: 0.98, 1.07; P = .20). Moreover, adding eloquent metrics improved the prediction accuracy (AUC, 0.73; 95% CI: 0.65, 0.81) compared with clinical variables alone (AUC, 0.65; 95% CI: 0.56, 0.73; P = .01) or a target mismatch profile (AUC, 0.67; 95% CI: 0.59, 0.76; P = .03). Conclusion Location-weighted infarction core and mismatch on diffusion and perfusion MRI scans improved the identification of patients with acute stroke who would benefit from mechanical thrombectomy compared with the volume-based target mismatch profile. Clinical trial registration no. NCT03045146 © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Nael in this issue.

ASCOD Phenotyping of Stroke With Anterior Large Vessel Occlusion Treated by Mechanical Thrombectomy.

BACKGROUND AND PURPOSE: Determining the mechanism of large vessel occlusion related acute ischemic stroke is of major importance to initiate a tailored secondary prevention strategy. We investigated using the atherosclerosis, small vessel disease, cardiac source, other cause, dissection (ASCOD) classification the distribution of the causes of large vessel occlusion related acute ischemic stroke treated by mechanical thrombectomy. METHODS: This was a predefined substudy of the FRAME (French Acute Multimodal Imaging to Select Patient for Mechanical Thrombectomy). Each patient underwent a systematic etiological workup including brain and vascular imaging, electrocardiogram monitoring lasting at least 24 hours and routine blood tests. Stroke mechanisms were systematically evaluated using the atherosclerosis, small vessel disease, cardiac source, other cause, dissection grading system at 3 months. We defined single potential cause by one cause graded 1 in a single domain, possible cause as a cause graded 1 or 2 regardless of overlap, and no identified cause without grade 1 nor 2 causes. RESULTS: A total of 215 patients (mean age 70±14; 50% male) were included. A single potential cause was identified in 148 (69%). Cardio-embolism (53%) was the most frequent, followed by atherosclerosis (9%), dissection (5%) and other causes (1%). Atrial fibrillation accounted for 88% of C1. Overlap between grade 1 causes was uncommon (3%). Possible causes were identified in 168 patients (83%) and 16 (7%) had no cause identified after the initial evaluation. CONCLUSIONS: Cardio-embolism, especially atrial fibrillation, was the major cause of large vessel occlusion related acute ischemic stroke. This finding emphasizes the yield of paroxysmal atrial fibrillation detection in those patients. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT03045146.

Mismatch Profile Influences Outcome After Mechanical Thrombectomy.

BACKGROUND AND PURPOSE: Mechanical thrombectomy (MT) is the recommended treatment for acute ischemic stroke caused by anterior circulation large vessel occlusion. However, despite a high rate of reperfusion, the clinical response to successful MT remains highly variable in the early time window where optimal imaging selection criteria have not been established. We hypothesize that the baseline perfusion imaging profile may help forecast the clinical response to MT in this setting. METHODS: We conducted a prospective multicenter cohort study of patients with large vessel occlusion-related acute ischemic stroke treated by MT within 6 hours. Treatment decisions and the modified Rankin Scale evaluation at 3 months were performed blinded to the results of baseline perfusion imaging. Study groups were defined a posteriori based on predefined imaging profiles: target mismatch (TMM; core volume <70 mL/mismatch ratio >1.2 and mismatch volume >10 mL) versus no TMM or mismatch (MM; mismatch ratio >1.2 and volume >10 mL) versus no MM. Functional recovery (modified Rankin Scale, 0-2) at 3 months was compared based on imaging profile at baseline and whether reperfusion (modified Thrombolysis in Cerebral Infarction 2bc3) was achieved. RESULTS: Two hundred eighteen patients (mean age, 71±15 years; median National Institutes of Health Stroke Scale score, 17 [interquartile range, 12-21]) were enrolled. Perfusion imaging profiles were 71% TMM and 82% MM. The rate of functional recovery was 54% overall. Both TMM and MM profiles were independently associated with a higher rate on functional recovery at 3 months Adjusted odds ratios were 3.3 (95% CI, 1.4-7.9) for TMM and 5.9 (95% CI, 1.8-19.6) for MM. Reperfusion (modified Thrombolysis in Cerebral Infarction 2bc3) was achieved in 86% and was more frequent in TMM and MM patients. Reperfusion was associated with a higher rate of functional recovery in MM and TMM patients but not among those with no MM. CONCLUSIONS: In this cohort study, about 80% of the patients with a large vessel occlusion-related acute ischemic stroke had evidence of penumbra, regardless of infarction volume. Perfusion imaging profiles predict the clinical response to MT.

Blood-brain barrier profile pretreatment is associated with hemorrhagic transformation after endovascular reperfusion.

BACKGROUND: While advances in endovascular thrombectomy (EVT) have led to high reperfusion rates, most patients treated with EVT do not avoid disability. Post-reperfusion hemorrhagic transformation (HT) is a potential target for improving outcomes. This study examined pretreatment blood-brain barrier (BBB) disruption in tissue that would subsequently become part of the final infarct to evaluate its role in post-EVT HT. METHODS: This post hoc analysis of the FRAME study, which enrolled patients with anterior large vessel occlusion who received EVT within 6 hours of onset, included patients if they had successful pretreatment MRI perfusion weighted imaging (PWI) and underwent successful EVT. BBB disruption was measured as the percent signal change due to gadolinium leakage on the PWI source images prior to thrombectomy. Mean permeability derangement (MPD) was defined as the average of all voxels in the stroke core that are two standard deviations above normal. The primary outcome was hemorrhagic transformation with parenchymal hematoma (PH). RESULTS: In total, 164 patients were included; mean age was 71 and 48% were female. PH occurred in 57 patients. Median MPD was 13.5% for patients with PH versus 3.6% for patients without (p < 0.0001). Elevated MPD was independently associated with PH with a 20% increased risk of PH for each 5% increase in MPD (OR 1.206; 95% CI 1.037:1.405; p = 0.0147, adjusted for NIHSS and procedure duration). CONCLUSIONS: Even in patients who are successfully recanalized in an early time window, pretreatment BBB disruption in regions that go on to infarct is associated with an increased risk of post-EVT HT.

What predicts poor outcome after successful thrombectomy in early time window?

BACKGROUND: Half of the patients with large vessel occlusion (LVO)-related acute ischemic stroke (AIS) who undergo endovascular reperfusion are dead or dependent at 3 months. We hypothesize that in addition to established prognostic factors, baseline imaging profile predicts outcome among reperfusers. METHODS: Consecutive patients receiving endovascular treatment (EVT) within 6 hours after onset with Thrombolysis In Cerebral Infarction (TICI) 2b, 2c and 3 revascularization were included. Poor outcome was defined by a modified Rankin scale (mRS) 3-6 at 90 days. No mismatch (NoMM) profile was defined as a mismatch (MM) ratio ≤1.2 and/or a volume <10 mL on pretreatment imaging. RESULTS: 187 patients were included, and 81 (43%) had a poor outcome. Median delay from stroke onset to the end of EVT was 259 min (IQR 209-340). After multivariable logistic regression analysis, older age (OR 1.26, 95% CI 1.06 to 1.5; p=0.01), higher National Institutes of Health Stroke Scale (NIHSS) (OR 1.15, 95% CI 1.06 to 1.25; p<0.0001), internal carotid artery (ICA) occlusion (OR 3.02, 95% CI 1.2 to 8.0; p=0.021), and NoMM (OR 4.87, 95% CI 1.09 to 22.8; p=0.004) were associated with poor outcome. In addition, post-EVT hemorrhage (OR 3.64, 95% CI 1.5 to 9.1; p=0.04) was also associated with poor outcome. CONCLUSIONS: The absence of a penumbra defined by a NoMM profile on baseline imaging appears to be an independent predictor of poor outcome after reperfusion. Strategies aiming to preserve the penumbra may be encouraged to improve these patients' outcomes.