What is the recommended time window for thrombectomy (thrombectomy) in patients with acute ischemic stroke?

Extended Time Window Thrombectomy: Evidence-Based Recommendations

Primary Recommendation

For patients with acute ischemic stroke and large vessel occlusion in the anterior circulation presenting 6-24 hours after last known well, mechanical thrombectomy is strongly recommended when advanced imaging (CT perfusion or diffusion-weighted MRI) demonstrates salvageable tissue using strict DAWN or DEFUSE-3 eligibility criteria. 1, 2

Time-Based Treatment Windows

Standard Window (0-6 Hours)

• Mechanical thrombectomy is strongly recommended for patients with proximal anterior circulation large vessel occlusion (ICA or MCA-M1) who can be treated within 6 hours of symptom onset 1, 2
• Eligibility requires: age ≥18 years, pre-stroke mRS 0-1, NIHSS ≥6, and ASPECTS ≥6 2
• Advanced imaging is not required in this window—proceed directly to thrombectomy after confirming large vessel occlusion on CTA or MRA 1, 2

Extended Window (6-16 Hours)

• Thrombectomy is recommended for carefully selected patients meeting DEFUSE-3 criteria: 1, 3
  • Proximal MCA or ICA occlusion confirmed on CTA/MRA
  • Initial infarct core <70 mL on CT perfusion or DW-MRI
  • Perfusion-to-core mismatch ratio ≥1.8
  • Mismatch volume ≥15 mL
• The DEFUSE-3 trial demonstrated 45% achieved functional independence (mRS 0-2) versus 17% with medical therapy alone (absolute difference 28%, P<0.001) 3
• Mortality was reduced from 26% to 14% with thrombectomy 3

Late Window (16-24 Hours)

• Thrombectomy is reasonable for patients meeting DAWN criteria: 1, 2
  • Group A: Age ≥80 years, NIHSS ≥10, infarct core <21 mL
  • Group B: Age <80 years, NIHSS ≥10, infarct core <31 mL
  • Group C: Age <80 years, NIHSS ≥20, infarct core 31-51 mL
• DAWN demonstrated 49% achieved functional independence versus 13% with medical therapy (absolute difference 36%, P<0.001) 1
• This represents the largest treatment effect ever demonstrated in acute stroke trials 4

Critical Imaging Requirements

For Extended Window (6-24 Hours)

• CT perfusion or diffusion-weighted MRI with perfusion imaging is mandatory—do not proceed without demonstrating salvageable tissue 1, 2, 5
• Either DAWN clinical-imaging mismatch criteria OR DEFUSE-3 perfusion-core mismatch criteria must be strictly applied 1
• The guidelines emphasize that only eligibility criteria from DAWN or DEFUSE-3 should be used—do not extrapolate beyond these validated criteria 1

For Standard Window (0-6 Hours)

• Non-invasive vascular imaging (CTA or MRA) to confirm large vessel occlusion is required 2
• Perfusion imaging should not delay treatment in this window 1

Posterior Circulation Considerations

• For basilar artery occlusion, thrombectomy is strongly recommended 0-12 hours from onset (Class I) 5
• Thrombectomy is reasonable 12-24 hours for basilar artery occlusion (Class IIa) 5
• Patients must have PC-ASPECTS ≥6 5
• Beyond 24 hours, thrombectomy may be considered case-by-case, though outcomes are generally poor 5

Technical and Procedural Standards

• The angiographic goal is modified TICI 2b/3 reperfusion 2, 5
• Stent retrievers are preferred over older-generation devices 2
• Do not delay catheter angiography to assess response to IV thrombolysis—this is explicitly not recommended 2, 6
• Eligible patients should receive IV thrombolysis even if thrombectomy is planned 2

Critical Pitfalls to Avoid

Most Common Errors

• Attempting thrombectomy in the 6-24 hour window without perfusion imaging—tissue selection is mandatory for benefit in extended windows 1, 5
• Deviating from DAWN or DEFUSE-3 eligibility criteria—these are the only validated selection criteria for extended window treatment 1
• Delaying thrombectomy to observe IV thrombolysis response—proceed directly to angiography if thrombectomy is being considered 2, 6
• Using NIHSS score alone for decision-making in extended windows—clinical-imaging or perfusion-imaging mismatch is required 1, 7

Time-Sensitive Considerations

• Only blood glucose measurement is required before initiating treatment—do not delay for other laboratory tests 1, 5
• Transport patients rapidly to centers with immediate access to cerebral angiography and qualified interventionalists 2

Strength of Evidence

The extended window recommendations are based on two landmark randomized controlled trials that fundamentally changed stroke care 1, 4:

• DAWN trial: Enrolled patients at median 12.5 hours, showed 35.5% absolute increase in functional independence—the largest effect ever seen in stroke treatment 4
• DEFUSE-3 trial: Treated patients at median 11 hours, demonstrated 28% absolute increase in functional independence and 20% reduction in death or severe disability 4, 3

Both trials showed no significant increase in symptomatic intracranial hemorrhage compared to medical therapy alone 3, with rates remaining at 5-7% 5

Paradigm Shift: Tissue Window vs. Time Window

The concept has evolved from rigid time windows to "tissue window" based on individual collateral flow and salvageable tissue 4, 8. However, in clinical practice, strict adherence to validated imaging criteria (DAWN or DEFUSE-3) is mandatory rather than subjective assessment of tissue viability 1, 7.