What are the indications for mechanical thrombectomy in acute ischemic stroke?

Indications for Mechanical Thrombectomy in Acute Ischemic Stroke

Mechanical thrombectomy is strongly recommended for patients with acute ischemic stroke who have large vessel occlusion (LVO) in the anterior circulation, meeting specific clinical and imaging criteria within appropriate time windows. 1

Primary Eligibility Criteria (0-6 Hours)

Patients should meet all of the following criteria:

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

Extended Time Window Criteria (6-24 Hours)

For patients presenting between 6-24 hours after last known well:

• Mechanical thrombectomy is recommended for patients with LVO in the anterior circulation who meet DAWN or DEFUSE 3 eligibility criteria 2
• For patients within 6-16 hours: Must meet DEFUSE 3 criteria using perfusion-core mismatch and maximum core size 2
• For patients within 6-24 hours: Must meet DAWN criteria using clinical-imaging mismatch 2
• Advanced imaging (CTP or DW-MRI, with or without MRI perfusion) is required to determine eligibility 2, 1
• Strict adherence to either DAWN or DEFUSE 3 eligibility criteria is necessary 2

Imaging Requirements

• All patients with suspected acute stroke should undergo brain imaging (head CT or brain MRI) without delay 2
• Non-invasive angiography (e.g., CTA) is necessary for patients with clinically suspected LVO 2, 1
• For extended time window (6-24 hours), advanced imaging with CTP, DW-MRI, or MRI perfusion is required 2, 1
• It may be reasonable to incorporate collateral flow status into clinical decision making 2

Special Considerations

• Mechanical thrombectomy can be considered for patients with occlusion or stenosis of the cervical ICA in addition to an intracranial LVO 2, 1
• 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, 3
• For M2 occlusions, mechanical thrombectomy is considered "may be reasonable" (Class IIb recommendation) 3

Procedural Considerations

• The technical goal of mechanical thrombectomy should be reperfusion to a modified Thrombolysis in Cerebral Infarction (mTICI) grade 2b/3 2, 1
• Stent retrievers are preferred over older devices like MERCI 1, 4
• Eligible patients should receive IV thrombolysis even if mechanical thrombectomy is being considered 2, 1
• Do NOT evaluate responses to IV thrombolysis before proceeding with catheter angiography for mechanical thrombectomy 2, 1

Implementation Requirements

• Treatment requires an experienced stroke center with immediate access to cerebral angiography and qualified interventionalists 1, 5
• 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

• Only blood glucose assessment must precede the initiation of IV alteplase in all patients; other tests should not delay treatment 2
• The availability of mechanical thrombectomy should not preclude the administration of IV thrombolysis in eligible patients 2, 1
• For extended time window patients, strictly adhere to DAWN or DEFUSE-3 eligibility criteria 2, 1
• Observing patients after IV thrombolysis to assess for clinical response before pursuing endovascular therapy is not recommended and may delay effective treatment 1, 6