What are the outcomes of thrombectomy (thrombus removal) in patients 6-24 hours after stroke onset?

Thrombectomy Outcomes 6-24 Hours After Stroke Onset

Thrombectomy performed 6-24 hours after stroke onset produces excellent functional outcomes when patients are selected using perfusion imaging to demonstrate salvageable tissue, with approximately 43-53% achieving functional independence (mRS 0-2) at 90 days.

Anterior Circulation Strokes

Patient Selection Requirements

• Perfusion imaging is mandatory in the 6-24 hour window to demonstrate salvageable tissue using either CT perfusion or diffusion-weighted MRI with perfusion imaging 1
• The landmark DAWN trial showed patients treated at a median of 12.5 hours achieved a 35.5% increase in functional independence—the largest effect ever described in acute stroke treatment 2
• DEFUSE 3 demonstrated patients treated at a median of 11 hours had a 28% increase in functional independence and 20% absolute reduction in death or severe disability 2

Functional Outcomes

• Good outcomes (mRS 0-2) occur in 42-53% of patients selected with perfusion imaging in the 6-24 hour window 3
• Excellent outcomes (mRS 0-1) occur in 26-32% of patients 3
• These outcomes are comparable to those achieved in the 0-6 hour window when proper imaging selection is used 3

Safety Profile

• Symptomatic intracranial hemorrhage rates remain low at 4.6-6.5%, similar to early window treatment 3
• Mortality rates are 3.2-5.7% in properly selected patients 3
• The technical goal should be modified TICI 2b/3 reperfusion to maximize functional outcomes 1

Posterior Circulation (Basilar Artery Occlusion)

Evidence-Based Time Windows

• Thrombectomy is indicated (Class I, Level B-R) for basilar artery occlusion from 0-12 hours based on the ATTENTION trial 4
• Thrombectomy is reasonable (Class IIa, Level B-R) from 12-24 hours based on the BAOCHE trial 4
• The BAOCHE trial specifically enrolled patients 6-24 hours after onset and demonstrated 46% achieved favorable outcomes (mRS 0-3) versus 24% with medical therapy alone 4

Basilar Artery Outcomes

• ATTENTION trial showed 46% achieved good functional outcome (mRS 0-3) versus 23% with medical therapy (absolute risk reduction 2.06) 4
• Mortality at 90 days was significantly lower with thrombectomy: 31-37% versus 42-55% with medical therapy 4
• Symptomatic intracranial hemorrhage remained low at 5-6%, not significantly different from medical therapy 4

Critical Factors Affecting Late Window Outcomes

Infarct Growth Velocity

• Late-presenting patients have slower infarct growth velocity (median 0.6 mL/h) compared to early presenters (5.1 mL/h) 3
• Patients with infarct core growth rate <4.1 mL/hr and initial core volumes <19.9 mL have >89% accuracy for maintaining core <50 mL at 24 hours, predicting favorable thrombectomy outcomes 5
• Up to half of all large vessel occlusion patients have this favorable slow-growth physiology 5

Imaging Characteristics

• Late-presenting patients typically have smaller hypoperfusion volumes (median 77 mL versus 133 mL in early presenters) 3
• Patients must have PC-ASPECTS ≥6 for posterior circulation strokes 4
• The concept of "tissue window" rather than "time window" is the paradigm shift that enables extended treatment 2

Common Pitfalls to Avoid

Critical Errors

• Never attempt thrombectomy in the 6-24 hour window without perfusion imaging—tissue selection is mandatory for benefit 1
• Do not delay thrombectomy for unnecessary testing; only blood glucose measurement is required before treatment 1
• Do not wait to assess IV thrombolysis response before proceeding to angiography if thrombectomy is being considered 1

Technical Considerations

• Fewer thrombectomy attempts are associated with better outcomes in late window patients 6
• Successful recanalization (TICI 2b-3) rates of 81-84% are achievable in the extended window 7

Beyond 24 Hours

Limited Evidence

• Thrombectomy beyond 24 hours may be reasonable on a case-by-case basis (Class IIb, Level C-EO) for basilar artery occlusion 4
• For anterior circulation, patients treated beyond 24 hours who otherwise meet DAWN criteria show comparable safety (5% symptomatic hemorrhage) and functional independence (43%) to those treated within 24 hours 7
• However, outcomes are generally worse beyond 24 hours (18.8% functional independence) compared to 6-24 hour window (34.9%), with higher mortality (OR 2.34) 6
• Functional outcomes beyond 24 hours remain poor when recanalization is achieved >9 hours after onset in patients with low NIHSS scores (≤6) 4