What are the criteria for thrombectomy (blood clot removal) in patients with acute ischemic stroke?

Criteria for Thrombectomy in Acute Ischemic Stroke

Mechanical thrombectomy is recommended for patients with acute ischemic stroke who meet specific criteria related to age, pre-stroke functional status, stroke severity, imaging findings, and time from symptom onset. 1

Primary Eligibility Criteria (0-6 hours from symptom onset)

Patients should receive mechanical thrombectomy with a stent retriever or direct aspiration if they meet ALL of the following criteria:

• Age ≥18 years 1
• Pre-stroke modified Rankin Scale (mRS) score of 0-1 1
• Causative occlusion of the internal carotid artery (ICA) or middle cerebral artery (MCA) M1 segment 1
• National Institutes of Health Stroke Scale (NIHSS) score ≥6 1
• 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: Mechanical thrombectomy is recommended if they have large vessel occlusion (LVO) in the anterior circulation and meet DAWN or DEFUSE 3 eligibility criteria 1
• For patients within 16-24 hours of last known normal: Mechanical thrombectomy is reasonable if they have LVO in the anterior circulation and meet DAWN eligibility criteria 1
• These patients must have sizable mismatch between ischemic core (by CT perfusion or MRI-DWI) and either clinical deficits or area of hypoperfusion (by CT perfusion or MRI-PWI) 1

Technical Considerations

• The technical goal should be reperfusion to a modified Thrombolysis in Cerebral Infarction (mTICI) grade 2b/3 1
• Stent retrievers are indicated in preference to older devices like MERCI 1
• Patients with clinically suspected LVO should have non-invasive angiography (e.g., CTA) 1
• Advanced imaging (CTP or DW-MRI, with or without MRI perfusion) is necessary for patients in the extended time window 1

Special Considerations

• Mechanical thrombectomy can be considered in patients with occlusion or stenosis of the cervical ICA in addition to an intracranial LVO 1
• Although benefits are less certain, thrombectomy may be reasonable for carefully selected patients with causative occlusion of the MCA M2/M3 segments, anterior cerebral arteries, vertebral arteries, basilar artery, or posterior cerebral arteries within 6 hours 1
• Thrombectomy may be reasonable for patients with pre-stroke mRS >1, ASPECTS <6, or NIHSS <6 with causative occlusion of the ICA or proximal MCA (M1) within 6 hours, though additional data are needed 1
• Eligible patients should receive IV thrombolysis even if mechanical thrombectomy is being considered 1
• Do NOT wait to evaluate responses to IV thrombolysis before proceeding with catheter angiography for mechanical thrombectomy 1

Implementation Requirements

• Treatment requires the patient to be at an experienced stroke center with immediate access to cerebral angiography and qualified interventionalists 1
• Facilities should define criteria to credential individuals who can perform endovascular procedures 1
• Patients should be transported rapidly to the closest available certified primary stroke center or comprehensive stroke center 1

Common Pitfalls and Caveats

• Strict adherence to DAWN or DEFUSE-3 eligibility criteria is necessary for patient selection in the extended time window 1
• The availability of mechanical thrombectomy should not preclude the administration of IV thrombolysis in eligible patients 1
• Time remains critical - earlier treatment is associated with better outcomes despite extended time windows 2
• Observing patients after IV thrombolysis to assess for clinical response before pursuing endovascular therapy is not required and is not recommended 1

Evolution of Recommendations

It's worth noting that recommendations regarding mechanical thrombectomy have evolved significantly. Earlier guidelines (2012) suggested against mechanical thrombectomy 1, but multiple positive randomized controlled trials since 2014 have established its efficacy with a number needed to treat of less than 3 for improved functional outcomes 3. Current guidelines strongly support its use in appropriate patients 1.