Endovascular thrombectomy in addition to intravenous thrombolysis versus intravenous thrombolysis alone in medium distal vessel occlusions (MDVO)– results from the SITS international stroke register (SITS ISTR)

BACKGROUND: Endovascular thrombectomy (EVT) is the standard of care for large vessel occlusion stroke. Medium distal vessel occlusions (MDVO) account for 25-40% of acute ischemic stroke cases, but recanalization rates with intravenous thrombolysis (IVT) are often <50%. Recent randomized trials have failed to show better outcomes after EVT vs best medical management in MDVO stroke. The main research question of the study: Is the addition of EVT to IVT associated with benefits or harm when treating patients with MDVO stroke? METHODS: We performed a retrospective observational study of patients in the Safe Implementation of Treatments of Stroke International Stroke Registry (SITS-ISTR) 2016-2023, treated with IVT or IVT+EVT for occlusion of the ACA, PCA or distal MCA (M3 and more distal). Only patients with available occlusion data from DTA or MRA were included. Patients with M2 occlusions or those treated with EVT only were excluded. Outcomes were acute post-treatment hemorrhage, three-month modified Rankin Scale (mRS) score, and death at 3 months. Propensity score matching was performed due to baseline imbalances (age, NIHSS, and occlusion site). RESULTS: Of 2198 included patients, 295 (13%) were treated with IVT+EVT, and 1903 (87%) received IVT alone. IVT+EVT patients were younger (73 vs 75) and had higher median NIHSS: 10 (IQR:6-15) vs 8 (5-12), p<0.001. More IVT+EVT patients were functionally independent (mRS 0-1) before stroke at 91.8% vs 83.0% (p<0.001). For the IVT+EVT group, PCA occlusion was the most common (n=179, 60.7%), and distal MCA (n=1140, 59.9%) in the IVT group. After propensity score matching, IVT+EVT was associated with worse three-month outcomes compared to IVT alone: mRS 0-1 (35.8% vs 47.0%, p=0.016, mRS 0-2 52.4% vs 63.4%, p=0.017, and death 21.4% vs 11.8%, p=0.005. Symptomatic intracerebral hemorrhage rates were higher in the IVT+EVT group according to ECASS II: 6.5% vs 2.4%, p=0.043, but were similar according to NINDS: 8.2% vs 4.2%, p=0.095, and SITS-MOST: 0.6% vs 1.2%, p=0.825. CONCLUSIONS: IVT+EVT for MDVO was associated with worse functional outcomes compared to IVT alone. Our results support recent publications but should be interpreted with caution due to the retrospective observational design, warranting further RCTs.