In a patient with acute ischemic stroke presenting within 4.5 hours, without large‑vessel occlusion on computed tomography angiography and without hemodynamically significant arterial stenosis, is routine computed tomography perfusion imaging required?

CTP is Not Required for Acute Ischemic Stroke Within 4.5 Hours Without Large-Vessel Occlusion

In patients presenting within 4.5 hours of acute ischemic stroke onset without large-vessel occlusion or hemodynamically significant stenosis on CTA, CT perfusion imaging is not necessary and should not be obtained, as it adds no value to clinical decision-making and only delays treatment.

Rationale Based on Current Guidelines

• The American College of Cardiology explicitly states that for patients presenting within the 6-hour timeframe, CTP is not necessary for clinical decision-making. 1

• Current guidelines recommend CTP only in patients with unknown onset or those presenting >6 hours from onset, because the late-window trials (DAWN and DEFUSE-3) used perfusion imaging to determine ischemic core in their highly selective inclusion criteria. 1

• The standard imaging protocol for acute stroke within 4.5 hours consists of only two studies: non-contrast CT to rule out hemorrhage and estimate ischemic core using ASPECTS, followed immediately by multiphase CTA to detect and localize any occlusion. 1

Why CTP Adds No Value in Your Scenario

• Without large-vessel occlusion, the patient is not a candidate for mechanical thrombectomy, which is the primary clinical decision that perfusion imaging would inform in the extended time window. 1, 2

• The decision to administer IV alteplase within 4.5 hours is based on clinical criteria (time window, NIHSS, blood pressure, glucose) and basic CT findings (no hemorrhage, ASPECTS ≥6)—not on perfusion parameters. 2, 3, 4

• Every minute of delay reduces the probability of favorable outcome; obtaining unnecessary imaging directly harms the patient by postponing thrombolysis. 2, 4

When CTP Is Indicated

• CTP becomes relevant only in three specific scenarios: patients with unknown time of onset (wake-up stroke), patients presenting 6-24 hours after last known well with confirmed large-vessel occlusion being considered for thrombectomy, or patients being evaluated for extended-window thrombolysis beyond 4.5 hours. 1, 2, 3, 4

• Recent evidence from the HOPE trial and meta-analyses supports using perfusion imaging to select patients for thrombolysis in the 4.5-24 hour window, showing improved functional outcomes (adjusted risk ratio 1.52 for mRS 0-1) despite increased symptomatic ICH (3.8% vs 0.5%). 5, 6

• The EXTEND trial demonstrated benefit from alteplase given 4.5-9 hours after onset in patients with salvageable tissue on perfusion imaging (35.4% vs 29.5% achieving mRS 0-1, adjusted RR 1.44). 7

Critical Pitfall to Avoid

• Do not delay IV alteplase administration to obtain CTP or any other advanced imaging when the patient presents within 4.5 hours without LVO. The only mandatory imaging before thrombolysis is non-contrast CT to exclude hemorrhage, and the only mandatory laboratory test is bedside glucose. 2, 3, 4

• The advantages of a single robust imaging protocol (NCCT + multiphase CTA) justify its use in all patients, avoiding overly selective treatment criteria that would deny therapy to eligible candidates. 1

Practical Algorithm for Your Scenario

1. Obtain non-contrast head CT immediately to rule out hemorrhage and assess ASPECTS. 1, 2, 3

2. Perform multiphase CTA from aortic arch to vertex to evaluate for large-vessel occlusion and guide any potential thrombectomy decision. 1, 2, 3

3. If no LVO is present and the patient meets eligibility criteria, proceed directly to IV alteplase (0.9 mg/kg, maximum 90 mg, with 10% as bolus over 1 minute, remaining 90% over 60 minutes). 2, 4

4. Do not obtain CTP—it provides no actionable information in this clinical context and only delays definitive therapy. 1