Intra-arterial Thrombolysis For Acute Ischemic Stroke With Medium Vessel Occlusion (IAT-MEVO)

With the continuous advancement of endovascular techniques and the widespread adoption of mechanical thrombectomy, endovascular treatment has become the standard of care for acute ischemic stroke caused by large vessel occlusion. However, the optimal management strategy for acute ischemic stroke caused by medium vessel occlusion (MeVO) remains an unmet clinical need. MeVO accounts for approximately 25-40% of all acute ischemic strokes and is associated with substantial morbidity, yet existing evidence from recent randomized controlled trials, including DISTAL and ESCAPE-MeVO, has failed to demonstrate a clear benefit of mechanical thrombectomy over best medical management alone in this population. Potential reasons include the limited suitability of current thrombectomy devices-which were primarily designed for large vessel occlusions-for more distal and tortuous medium vessels, leading to lower recanalization rates and increased risks of vessel perforation, dissection, and vasospasm. Moreover, the significant heterogeneity in patient selection across previous trials, particularly the lack of unified imaging inclusion criteria, may have diluted the potential treatment effect in specific subgroups.

Intra-arterial thrombolysis (IAT), as an alternative endovascular approach, offers theoretical advantages for MeVO. By delivering thrombolytic agents directly into or adjacent to the thrombus via a microcatheter, IAT achieves high local drug concentrations while minimizing systemic exposure. Evidence from the PROACT II study demonstrated that intra-arterial prourokinase significantly improved 90-day functional outcomes in patients with middle cerebral artery occlusion compared with heparin alone. More recently, the CHOICE trial showed that adjunctive intra-arterial alteplase following successful thrombectomy improved functional outcomes in large vessel occlusion stroke. These findings suggest that IAT may effectively dissolve residual thrombi in distal vascular beds and improve microcirculatory reperfusion-mechanisms particularly relevant to MeVO, where thrombus burden is generally smaller and the target vessels are more amenable to pharmacological dissolution.

Despite these promising signals, no dedicated randomized controlled trial has specifically evaluated IAT as a primary treatment strategy for MeVO. Current guidelines provide no clear recommendation for or against endovascular treatment in this population, reflecting the urgent need for high-quality evidence. Furthermore, the optimal patient selection criteria-including imaging parameters (perfusion mismatch), clinical severity thresholds (NIHSS range), and the distinction of isolated medium vessel occlusion from other stroke subtypes-remain to be defined to maximize the therapeutic benefit.

This study intends to conduct a multicenter, prospective, randomized, open-label, blinded-endpoint (PROBE) phase III trial to compare the clinical outcomes of intra-arterial thrombolysis plus best medical management versus best medical management alone in patients with acute ischemic stroke due to medium vessel occlusion. A total of 306 eligible patients (aged 18-80 years) with confirmed MeVO (distal M2/M3, A2/A3, P1/P2/P3 segments) and baseline NIHSS score 6-25 (or 3-5 with disabling deficits) within 24 hours of symptom onset will be enrolled. For patients presenting beyond 6 hours, perfusion imaging criteria (Tmax > 6s ≥ 10cc, with core infarct volume < 50% of the hypoperfusion area) will be applied to select those with salvageable brain tissue. Participants will be randomly assigned 1:1 to receive either intra-arterial thrombolysis (using either alteplase 0.225 mg/kg, maximum 22.5 mg, or tenecteplase 0.0625 mg/kg, maximum 6.25 mg, administered via microcatheter over 15-30 minutes) plus best medical management, or best medical management alone. The primary endpoint is the proportion of patients achieving functional independence (modified Rankin Scale score 0-2) at 90±7 days post-randomization. Secondary endpoints include recanalization rate, early neurological improvement, overall functional outcome distribution, excellent functional outcome, quality of life, functional independence, and comprehensive safety outcomes including symptomatic intracranial hemorrhage, early neurological deterioration, any intracranial hemorrhage, procedure-related complications, and all-cause mortality.

The study is led by the First Affiliated Hospital of Nanjing Medical University (Jiangsu Province Hospital) as the coordinating center, with 25 participating centers across China. An independent Data Safety Monitoring Board (DSMB) will oversee the trial, with one planned interim analysis using an O'Brien-Fleming-like alpha-spending function. The total study duration is 3 years (June 2026 to May 2029), with enrollment anticipated to be completed within 20 months. The results of this trial are expected to provide high-level evidence on whether intra-arterial thrombolysis offers a safe and effective treatment option for patients with acute ischemic stroke due to medium vessel occlusion, potentially establishing a new standard of care in this underserved population.