Predictors Of Unfavourable Events Despite Successful Mechanical Thrombectomy In The Extended Window

Background: Futile recanalization (FR) and symptomatic intracranial hemorrhage (sICH) are adverse outcomes after otherwise successful mechanical thrombectomy (MT). The aim of this study was to evaluate independent predictors of these unfavourable events in the extended time window and to compare imaging modalities (non-enhanced CT (NCCT) alone vs. CT perfusion vs. MRI) regarding patient selection. Methods: The CT for Late EndovasculAr Reperfusion (CLEAR) study was a multicenter, retrospective study of stroke patients undergoing thrombectomy in the extended time window. The primary endpoint of this study was the proportion of patients with FR, defined as a patient with large vessel occlusion achieving near-complete or complete reperfusion (TICI 2c/3) with a 90-day mRS score between 3 and 6. The secondary safety endpoints included the predictors of mortality and symptomatic intracranial hemorrhage. Inclusion criteria for this analysis were baseline NIHSS ≥6, internal carotid artery, M1 or M2 segment occlusion, prestroke modified rankin scale (pmRS) 0-2, time last seen well (TLSW) to treatment 6-24 hours, and mTICI 2c-3. Results: Of 2304 patients in the CLEAR study, 715 patients were included in this analysis. Of these, 364 patients (50.9%) showed FR, 37 patients (5.2%) suffered sICH and 127 patients (17.8%) died within 90 days. Old age, higher baseline NIHSS, higher prestroke disability, transfer to a comprehensive stroke center from another site, and a longer interval from TLSW to puncture were identified as positive predictors of FR. Hypertension was an independent predictor of sICH. The imaging modality (NCCT vs. CT perfusion vs. MRI) was not associated with FR, sICH, or mortality. Conclusions: Older age, higher baseline NIHSS, higher prestroke disability, transfer patients, and a longer interval from TLSW to puncture were predictors of FR in the extended window. Hypertension was a predictor of sICH in successfully reperfused patients. Neither MRI or CT perfusion was superior in predicting FR and sICH compared to NCCT alone. NCCT together with CTA may be sufficient for patient selection in the extended time window. Trial Registration: ClinicalTrials.gov Identifier: NCT04096248