Expanding Indications for IV Thrombolysis in Acute Ischemic Stroke

Since the original NINDS trial in 1995, the eligibility criteria for intravenous thrombolysis have progressively widened. Early limitations—such as narrow time windows, strict age cutoffs, and exclusion of patients with unknown onset—have given way to a more nuanced, individualized approach. The 2026 AHA/ASA guidelines consolidate decades of evidence and formally endorse tissue-based patient selection.

Updated to reflect the 2026 AHA/ASA Guidelines for Early Management of Acute Ischemic Stroke.

Time Windows: From 3 Hours to 24 Hours

Standard Window: 0–4.5 Hours

Current guidelines endorse IVT within 4.5 hours of stroke onset for patients with disabling deficits. This is based on NINDS (0–3h) and ECASS III (3–4.5h) trials.

2026 Update: Treatment should be initiated as quickly as possible. Do NOT delay for additional multimodal neuroimaging (CTA/MRA, CTP) when not necessary for treatment decisions (Class 1).

Unknown Onset / Wake-Up Stroke

Patients with unknown time of onset—such as wake-up strokes—are eligible if MRI mismatch (DWI positive, FLAIR negative) confirms biological onset within 4.5 hours.

• WAKE-UP (2018): mRS 0–1 in 53.3% vs 41.8% (P = 0.02)
• DWI lesion must be <1/3 MCA territory; no marked FLAIR signal change

2026 Guideline: Class 2a (B-R) — IVT can be beneficial within 4.5h of symptom recognition if MRI criteria met.

Extended Window: 4.5–9 Hours

EXTEND (2019) and pooled analyses used perfusion imaging to identify patients with salvageable penumbra up to 9h:

• mRS 0–1: 35.4% vs 29.5% (aRR 1.44; P = 0.04)
• sICH: 6.2% vs 0.9%

2026 Guideline: Class 2a (B-R) — IVT may be reasonable in 4.5–9h window OR wake-up stroke within 9h of sleep midpoint with salvageable penumbra on perfusion imaging.

Extended Window: 4.5–24 Hours (LVO)

Recent trials pushed the window further for LVO patients:

• TRACE-III (2024): Tenecteplase in LVO without EVT; mRS 0–1: 33.0% vs 24.2% (P = 0.03)
• TIMELESS (2024): Tenecteplase in LVO with EVT; Neutral — IVT did not add benefit when rapid EVT available
• CHABLIS-T II (2025): Improved recanalization but no significant difference in functional outcomes

2026 Guideline: Class 2b (B-R) — In LVO patients 4.5–24h with salvageable penumbra who cannot receive or will have delayed EVT, IVT may be beneficial when directed by experts.

Patient Factors: Age, Baseline Function, Stroke Severity

Age

Guidelines no longer impose an upper age limit. Patients >80 years are eligible if otherwise appropriate. ECASS III originally excluded age >80 in the 3–4.5h window, but subsequent data and meta-analyses support treatment in elderly patients.

Preexisting Disability

Patients with preexisting disability (mRS ≥2) can receive IVT if the stroke is expected to cause new, disabling deficits. Decision-making should incorporate goals of care, functional prognosis, and patient preferences.

Stroke Severity

Severity is not an automatic exclusion:

• Very severe (NIHSS >25): Benefit uncertain; individualize (Class 2b)
• Mild but disabling: Reasonable to treat (Class 2a)
• Mild non-disabling (e.g., isolated sensory): NOT recommended — no superiority vs DAPT in PRISMS trial (Class 3: No Benefit)

Special Populations

Antiplatelet Use

2026 Guideline: IVT is recommended despite prior single or dual antiplatelet therapy (Class 1, B-NR). Although sICH risk is increased compared to no antiplatelet use, net benefit persists.

Cerebral Microbleeds

2026 Guideline:

• Unknown CMB burden: Do NOT delay IVT for MRI (Class 1)
• 1–10 CMBs: IVT reasonable (Class 2a)
• >10 CMBs: Benefit uncertain; may increase sICH (Class 2b)

Pediatric Patients

2026 Guideline: In pediatric patients (28 days–18 years) with confirmed AIS presenting within 4.5h with disabling deficits, IVT with alteplase may be considered (Class 2b, C-LD). Safe but efficacy uncertain.

Choice of Thrombolytic Agent

2026 Paradigm Shift: Tenecteplase 0.25 mg/kg is now formally equivalent to alteplase (Class 1, Level A) based on >6000 patients in multiple phase 3 trials (AcT, TRACE-2, TASTE, ATTEST-2, ORIGINAL).

Summary: Evolution of IVT Eligibility

Conclusion

The 2026 guidelines represent the culmination of 30 years of progress in acute stroke reperfusion. The modern approach emphasizes tissue and clinical viability over rigid time rules. Imaging selection with MRI or CT perfusion, patient-centered evaluation of risks and benefits, and the formal endorsement of tenecteplase as equivalent to alteplase continue to expand access to reperfusion therapy for appropriate patients.