Late Window IVT — Wake-Up Stroke & Thrombolysis Eligibility
Last Known Well (LKW) Time
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Frequently asked questions
What is late window IVT and who is eligible?
Late window IVT refers to IV thrombolysis beyond the standard 4.5-hour window. Eligibility depends on imaging and timing: DWI-FLAIR mismatch on MRI for unknown-onset stroke within 4.5 hours of symptom recognition (COR 2a, WAKE-UP), perfusion mismatch in the 4.5–9 hour window (COR 2a, EXTEND), or selected patients with LVO, salvageable penumbra, no feasible rapid EVT pathway, and expert thrombolytic stroke oversight in the late window up to 24 hours from last known well (COR 2b, TRACE-3/TIMELESS).
How is wake-up stroke treated with thrombolysis?
Wake-up stroke can be treated with IV thrombolysis if MRI shows DWI-FLAIR mismatch and treatment can start within 4.5 hours of symptom recognition, consistent with the WAKE-UP trial and the 2026 AHA/ASA COR 2a recommendation. If MRI criteria are not met, patients with a known last-known-well time may still be considered for later LVO-only pathways using perfusion imaging and EVT/expertise screening.
What is the difference between COR 2a and COR 2b for late window thrombolysis?
COR 2a applies when imaging selection strongly favors treatment, such as DWI-FLAIR mismatch for wake-up stroke or perfusion mismatch in the 4.5–9 hour window. COR 2b applies to a narrower late-window group: patients with AIS due to LVO, salvageable penumbra, no feasible rapid EVT option, and treatment directed by clinicians with expertise in thrombolytic stroke care.