Which large vessel occlusions qualify for clot retrieval, specifically mechanical thrombectomy?

Large Vessel Occlusions Qualifying for Mechanical Thrombectomy

Mechanical thrombectomy is recommended for patients with acute ischemic stroke who have large vessel occlusions (LVOs) of the internal carotid artery (ICA) or middle cerebral artery (MCA) M1 segment, with treatment initiated within 6 hours of symptom onset, and who meet specific clinical and imaging criteria. 1

Primary Eligibility Criteria (0-6 hours)

Patients qualify for mechanical thrombectomy if they meet all of the following:

• Age ≥18 years 1, 2
• Pre-stroke modified Rankin Scale (mRS) score of 0-1 1
• Causative occlusion of the internal carotid artery (ICA) or proximal middle cerebral artery (MCA M1) 1
• National Institutes of Health Stroke Scale (NIHSS) score ≥6 1, 2
• Alberta Stroke Program Early CT Score (ASPECTS) ≥6 1
• Treatment can be initiated (groin puncture) within 6 hours of symptom onset or last known well 1

Extended Time Window Criteria (6-24 hours)

• For patients within 6-16 hours of last known normal: LVO in anterior circulation and meeting DAWN or DEFUSE 3 eligibility criteria 1
• For patients within 16-24 hours of last known normal: LVO in anterior circulation and meeting DAWN eligibility criteria 1
• Advanced imaging (CTP or DW-MRI, with or without MRI perfusion) is required to determine eligibility by demonstrating sizable mismatch between ischemic core and either clinical deficits or area of hypoperfusion 1

Additional Vessel Occlusions with Less Certain Benefit

While evidence is strongest for ICA and MCA M1 occlusions, mechanical thrombectomy may be reasonable in selected patients with:

• MCA segment 2 (M2) or segment 3 (M3) occlusions 1
• Anterior cerebral artery occlusions 1
• Vertebral artery occlusions 1
• Basilar artery occlusions 1
• Posterior cerebral artery occlusions 1
• Tandem lesions (extracranial carotid occlusion/stenosis with intracranial LVO) 1

Special Considerations

• Patients with pre-stroke mRS >1, ASPECTS <6, or NIHSS <6 may still be considered for mechanical thrombectomy if they have ICA or MCA M1 occlusions, though benefits are less certain 1
• The technical goal should be reperfusion to modified Thrombolysis in Cerebral Infarction (mTICI) grade 2b/3 1
• Eligible patients should receive IV thrombolysis even if mechanical thrombectomy is being considered 1, 2
• Evaluation of responses to IV thrombolysis should not delay catheter angiography for mechanical thrombectomy 1, 2

Important Caveats

• For extended time window patients (6-24 hours), strict adherence to DAWN or DEFUSE-3 eligibility criteria is necessary 1
• Non-invasive angiography (e.g., CTA) should be performed in patients with clinically suspected LVO but should not delay IV thrombolysis if indicated 1
• Treatment requires an experienced stroke center with immediate access to cerebral angiography and qualified interventionalists 2
• Distal vessel occlusions (beyond M2) have less robust evidence but may be considered in carefully selected cases 3
• Stent retrievers or direct aspiration techniques can be used, with stent retrievers generally preferred 2, 4

Emerging Evidence

• Recent studies suggest that patients with slower infarct growth velocity may benefit from mechanical thrombectomy even in extended time windows 5
• Alternative access routes (such as trans-anterior communicating artery approach) may be considered when direct access to the occluded vessel is challenging 6
• Special populations, such as patients on extracorporeal membrane oxygenation (ECMO), may also benefit from mechanical thrombectomy for LVOs 7