Does thrombectomy (thrombus removal) 6-24 hours after stroke onset improve functional independence?

Thrombectomy 6-24 Hours After Stroke Onset and Functional Independence

Yes, thrombectomy performed 6-24 hours after stroke onset significantly improves functional independence in carefully selected patients with large vessel occlusion who demonstrate salvageable brain tissue on advanced imaging. 1, 2

Evidence-Based Patient Selection Criteria

The American Heart Association guidelines establish that thrombectomy in the 6-24 hour window requires mandatory perfusion imaging to identify salvageable tissue—this is not optional. 1, 2 Specifically:

• CT perfusion or diffusion-weighted MRI with perfusion imaging must demonstrate a mismatch between the ischemic core and the area of hypoperfusion 2, 3
• Patients must have confirmed large vessel occlusion on CTA or MRA 1
• ASPECTS score ≥6 is required 1, 3
• NIHSS score ≥6 for eligibility 1
• Age 18-89 years, though age limits should not be absolute contraindications 1

Magnitude of Benefit

The landmark trials supporting this approach demonstrate substantial improvements in functional outcomes:

• DAWN trial: 49% achieved functional independence (mRS 0-2) with thrombectomy versus 13% with medical therapy alone—a 33% absolute difference and the largest effect ever described in acute stroke treatment 3, 4
• DEFUSE-3 trial: 45% achieved functional independence versus 17% with medical therapy alone, with a 28% absolute increase in good outcomes 2, 3, 5
• The odds ratio for favorable functional outcome was 2.77 in DEFUSE-3 (P<0.001) 5
• Mortality was reduced from 26% to 14% in the DEFUSE-3 trial 5

Posterior Circulation Considerations

For basilar artery occlusion specifically, the evidence supports an even broader time window:

• 0-12 hours: Thrombectomy is indicated (Class I, Level B-R) based on the ATTENTION trial, which showed 46% achieved good functional outcome versus 23% with medical therapy 1, 2
• 12-24 hours: Thrombectomy is reasonable (Class IIa, Level B-R) based on the BAOCHE trial, demonstrating 46% favorable outcomes versus 24% with medical therapy alone 1, 2
• Patients must have PC-ASPECTS ≥6 1, 2
• Mortality was significantly lower with thrombectomy (31-37% versus 42-55%) 2

Critical Pitfalls to Avoid

Do not proceed with thrombectomy in the 6-24 hour window without perfusion imaging—tissue selection is mandatory for benefit, and treating patients without demonstrable salvageable tissue exposes them to procedural risks without potential benefit. 2, 3

Do not delay thrombectomy for unnecessary testing—only blood glucose measurement is required before treatment initiation. 2, 3

Do not wait to assess IV thrombolysis response before proceeding to angiography if thrombectomy is being considered. 2

Do not use time alone as the selection criterion—the paradigm has shifted from "time window" to "tissue window," recognizing that individual patients have varying compensatory mechanisms and collateral flow patterns. 4

Technical and Post-Procedural Management

• The angiographic target should be modified TICI 2b/3 reperfusion to maximize functional outcomes 2, 6, 3
• Maintain blood pressure ≤180/105 mmHg during and for 24 hours after the procedure 6
• Symptomatic intracranial hemorrhage rates remain low (5-7%) and are not significantly different from medical therapy alone 2, 5

Time-Dependent Effects Within the Extended Window

Even within the 6-24 hour window, faster treatment correlates with better outcomes, particularly in patients with ASPECTS 8-10. 7 Each 15-minute delay decreases the probability of good functional outcome (adjusted OR 0.98 per 15 minutes). 7 However, this time-dependency is less pronounced in the 6-24 hour window compared to the 0-6 hour window, reinforcing that tissue viability rather than absolute time is the critical determinant. 7

Contraindications in the Extended Window

ASPECTS score of 0 indicates extensive irreversible brain damage and precludes benefit from thrombectomy. 3

Absence of perfusion mismatch indicates no salvageable tissue, making reperfusion unlikely to provide benefit. 3

Time beyond 24 hours for anterior circulation strokes remains outside established therapeutic windows, though posterior circulation (basilar artery) occlusions may be considered on a case-by-case basis (Class IIb, Level C-EO). 1, 2