What are the indications and eligibility criteria for intravenous alteplase thrombolysis in an adult acute posterior cerebral artery ischemic stroke presenting within 4.5 hours?

Indications for Thrombolysis in Posterior Cerebral Artery (PCA) Stroke

Intravenous alteplase (0.9 mg/kg, maximum 90 mg) should be administered to adults with acute PCA ischemic stroke who present within 4.5 hours of symptom onset and meet standard eligibility criteria, with the same inclusion/exclusion criteria applied as for anterior circulation strokes. 1

Standard Time Windows and Eligibility

0–3 Hour Window (Level A Recommendation)

• All patients meeting NINDS criteria should receive IV alteplase within 3 hours of symptom onset, regardless of stroke severity or age >80 years. 2, 1
• The 0–3 hour window produces a 12% absolute increase in achieving minimal or no disability (modified Rankin Scale 0-1: 39% vs 26% with placebo), with a number needed to treat of 8.3. 1
• High NIHSS scores (severe stroke) do not contraindicate treatment in this window. 1
• Age >80 years is not an exclusion criterion for the 0–3 hour window. 1, 3

3–4.5 Hour Window (Level B Recommendation)

• Alteplase should be considered for patients meeting ECASS III criteria in the 3–4.5 hour window, but with additional exclusions. 2, 1
• The following patients are excluded from the 3–4.5 hour window: age >80 years, current oral anticoagulant use (regardless of INR), NIHSS >25, or history of both diabetes and prior stroke. 1, 4
• All other standard eligibility criteria continue to apply. 1

Dosing and Administration Protocol

• Standard dose: 0.9 mg/kg (maximum 90 mg absolute). 1, 4
• Give 10% of total dose (0.09 mg/kg) as IV bolus over exactly 1 minute. 1, 4
• Infuse remaining 90% (0.81 mg/kg) over 60 minutes. 1, 4
• Every 15-minute delay in treatment reduces the likelihood of favorable outcome—"time is brain." 1

Mandatory Pre-Treatment Requirements

Blood Pressure Management

• Systolic/diastolic must be lowered to <185/110 mmHg before initiating alteplase. 1, 4
• Maintain blood pressure <180/105 mmHg for the first 24 hours after infusion. 1, 4

Imaging Requirements

• Non-contrast CT or MRI must exclude intracranial hemorrhage before treatment. 1
• Early ischemic changes should involve ≤1/3 of the middle cerebral artery territory (though this applies more to MCA strokes; for PCA strokes, ensure no extensive established infarction). 1

Laboratory Requirements

• Blood glucose must be >50 mg/dL before alteplase administration. 1
• Only blood glucose assessment must precede IV alteplase—do not delay for other laboratory results. 1

Absolute Contraindications for PCA Stroke

• Intracranial hemorrhage on initial imaging. 1
• Prior ischemic stroke within the preceding 3 months. 1
• Severe head trauma within the preceding 3 months. 1
• Intracranial or spinal surgery within the preceding 3 months. 4
• Active internal bleeding or gastrointestinal malignancy with bleeding within 21 days. 4
• Platelet count <100,000/mm³ or INR >1.7. 4
• Uncontrolled blood pressure >185/110 mmHg despite treatment. 4

Special Considerations for PCA Territory

• Patients with mild but disabling PCA symptoms (e.g., isolated hemianopia causing functional impairment, alexia without agraphia) should not be excluded from treatment. 4
• Prior use of single-agent or dual antiplatelet therapy (aspirin + clopidogrel) is not a contraindication. 1
• End-stage renal disease patients on hemodialysis with normal aPTT are eligible. 1

Post-Treatment Monitoring Protocol

• Neurological assessment every 15 minutes during infusion, every 30 minutes for 6 hours, then hourly until 24 hours. 1
• Blood pressure monitoring: every 15 minutes for 2 hours, every 30 minutes for next 6 hours, then hourly up to 24 hours. 1
• If severe headache, acute hypertension, nausea, or vomiting occur, stop infusion immediately and obtain emergent CT. 1
• Delay placement of nasogastric tubes, indwelling bladder catheters, and intra-arterial pressure catheters until after the monitoring period. 1
• Obtain follow-up CT at 24 hours before starting anticoagulant or antiplatelet therapy; defer these agents for at least 24 hours after alteplase. 1

Relationship to Endovascular Therapy

• Eligible patients should receive IV alteplase even if mechanical thrombectomy is being considered—do not delay IV thrombolysis to assess for thrombectomy eligibility. 1
• If large vessel occlusion is suspected, obtain CTA immediately after non-contrast CT, but do not delay alteplase infusion. 1
• For PCA occlusions amenable to thrombectomy, proceed with both treatments without waiting to assess IV thrombolysis response. 1

Institutional Requirements

• The effectiveness of alteplase is less well established in hospitals lacking organized stroke systems (24/7 rapid CT, dedicated stroke team, continuous neurological monitoring, blood-pressure management protocols, and neurosurgical consultation). 2, 1
• Protocol violations increase symptomatic intracranial hemorrhage risk, especially in centers treating fewer than 5 stroke patients per year. 4

Common Pitfalls to Avoid

• Do not withhold alteplase from PCA stroke patients due to "mild" symptoms if those symptoms are functionally disabling (e.g., hemianopia preventing driving or reading). 4
• Do not exclude patients >80 years old in the 0–3 hour window—age restriction only applies to the 3–4.5 hour window. 1, 3
• Do not delay treatment for complete laboratory workup—only blood glucose is mandatory before administration. 1
• Be aware of angioedema as a potential adverse effect causing partial airway obstruction. 1