What are the indications for endovascular thrombectomy in patients with acute ischemic stroke, particularly those with large vessel occlusion and significant neurological deficit?

Endovascular Thrombectomy Indications for Acute Ischemic Stroke

Endovascular thrombectomy is indicated for patients with acute ischemic stroke due to large vessel occlusion when they present with NIHSS ≥6, demonstrating functionally relevant neurological deficit. 1

Anterior Circulation Large Vessel Occlusion

Early Window (0-6 Hours)

Thrombectomy is definitively indicated for patients meeting ALL of the following criteria: 1, 2

• Large vessel occlusion (distal internal carotid artery, M1 segment, or proximal M2 segment of middle cerebral artery) confirmed on CT angiography 1
• NIHSS score ≥6 indicating functionally relevant neurological deficit 1
• ASPECTS ≥6 on non-contrast CT 2
• Age 18-89 years 1
• Presentation within 6 hours of last known well 1, 2

Critical point: Perfusion imaging is NOT required in this time window—proceed directly to thrombectomy based on non-contrast CT and CTA alone to avoid delays. 2, 3

Extended Window (6-24 Hours)

Thrombectomy remains indicated but requires additional imaging selection: 1, 3

• CT perfusion or MRI with diffusion-weighted imaging is mandatory to demonstrate salvageable tissue (small core, significant penumbra) 3
• ASPECTS ≥6 and favorable perfusion parameters per DAWN or DEFUSE-3 criteria 3
• Intermediate to good collaterals on multiphase CTA 2
• Same clinical criteria (NIHSS ≥6, confirmed LVO) 3

The benefit remains substantial even in this extended window, particularly when advanced imaging demonstrates salvageable tissue. 1

Posterior Circulation (Basilar Artery Occlusion)

The evidence for basilar artery occlusion thrombectomy has recently strengthened with high-quality RCT data: 1

0-12 Hours Window

• Class I, Level B-R recommendation for thrombectomy 1
• Requires NIHSS ≥6 and PC-ASPECTS ≥6 1, 4
• No perfusion imaging required—proceed based on non-contrast CT and CTA confirmation of basilar occlusion 3

12-24 Hours Window

• Class IIa, Level B-R recommendation (reasonable to perform) 1, 3, 4
• Same clinical and imaging criteria (NIHSS ≥6, PC-ASPECTS ≥6) 1, 3

Beyond 24 Hours

• Class IIb, Level C-EO recommendation (may be considered case-by-case) 1, 3
• Outcomes are generally poor, but may be reasonable in highly selected patients with severe deficits 3

The mortality benefit is substantial: 31-37% mortality with thrombectomy versus 42-55% with medical therapy alone in basilar occlusion. 3

Distal Vessel Occlusions

Thrombectomy of more distal vessels (distal M2, M3, or other smaller branches) may be considered but requires careful risk-benefit assessment: 1

• Weigh procedural risks against likelihood of successful recanalization 1
• Consider severity of clinical deficits—more aggressive intervention justified with higher NIHSS 1
• High-quality evidence is lacking for routine distal vessel thrombectomy 1

Technical Approach

Both stent retrievers and direct aspiration are acceptable first-line techniques: 2

• Target modified TICI 2b/3 reperfusion (successful recanalization in 70-90% of cases) 2, 3
• Combined techniques should be employed if initial approach fails 2
• Expected good functional outcome (mRS 0-3) in 40-50% of appropriately selected patients 2

Bridging Intravenous Thrombolysis

Intravenous thrombolysis remains a reasonable bridging strategy when thrombectomy is planned: 1

• Administer IV tPA to otherwise-eligible patients even if thrombectomy is planned 1
• Do not delay thrombectomy to assess IV tPA response 3
• Consider individual bleeding risk from the cardiovascular procedure context 1

Critical Pitfalls to Avoid

Time-wasting errors that worsen outcomes: 2, 3

• Never delay thrombectomy for unnecessary perfusion imaging in clear candidates presenting within 6 hours 2, 3
• Never wait to assess IV thrombolysis response before proceeding to angiography 3
• Never attempt thrombectomy without perfusion imaging in the 6-24 hour window—tissue selection is mandatory 3
• Never delay transfer to thrombectomy-capable centers for patients with confirmed LVO 4

Special Populations

Periprocedural Stroke After Cardiovascular Interventions

If cerebral vessel occlusion occurs during or immediately after a cardiovascular procedure: 1

• Leave the vascular sheath in place for thrombectomy access 1
• Multidisciplinary decision-making involving stroke physician, interventional cardiologist, neurologist, and radiologist is essential 1
• Bleeding risk from the index procedure must be carefully weighed against thrombectomy benefit 1

Age Considerations

Standard age range is 18-89 years, but exceptions exist: 1

• Patients <18 years or >89 years may be considered on a case-by-case basis (Class IIb, Level C-EO) 1

Post-Thrombectomy Management

All patients require stroke unit admission for multidisciplinary care to reduce disability and mortality. 1 This organized approach is pivotal regardless of recanalization success. 1

Symptomatic intracranial hemorrhage rates are 5-8%, comparable to combined IV thrombolysis plus thrombectomy, and do not represent an increased risk compared to medical therapy alone in most studies. 2, 3