Management of Acute Ischemic Stroke at 7 Hours with CTP Mismatch Ratio 1.3
This patient does NOT meet criteria for mechanical thrombectomy based on current evidence-based guidelines, and standard medical management should be pursued instead. 1
Why This Patient Does Not Qualify for Extended-Window Thrombectomy
The critical issue is that a mismatch ratio of 1.3 falls far below the threshold required for late-window intervention. The 2018 AHA/ASA guidelines explicitly state that only patients meeting DAWN or DEFUSE-3 eligibility criteria should receive mechanical thrombectomy between 6-24 hours, and these criteria must be "strictly adhered to in clinical practice." 1
DEFUSE-3 Eligibility Requirements (6-16 hours):
- Mismatch ratio ≥1.8 (this patient has only 1.3) 1
- Mismatch volume ≥15 mL
- Ischemic core <70 mL
- Large vessel occlusion in anterior circulation 1
DAWN Eligibility Requirements (6-24 hours):
- Uses clinical-imaging mismatch based on age, NIHSS score, and core volume
- Requires substantial mismatch between clinical deficit severity and small core size 1
The mismatch ratio of 1.3 indicates insufficient salvageable penumbra relative to the ischemic core, making the risk-benefit ratio of thrombectomy unfavorable at this time point. 1
Recommended Management Pathway
Immediate Assessment
- Confirm exact symptom onset time and last known well time 1
- Document NIHSS score and prestroke mRS 1
- Verify large vessel occlusion location (ICA or M1 segment) on CTA 1
- Calculate ASPECTS score on non-contrast CT 1
Medical Management
- Blood pressure control: Maintain BP ≤180/105 mmHg if no reperfusion therapy is planned 2
- Aspirin 160-325 mg should be administered within 24-48 hours of stroke onset (can start now since patient is beyond thrombolysis window) 2
- Avoid IV alteplase as the patient is beyond the 4.5-hour window 1
Monitoring Protocol
- Serial neurological examinations every 15 minutes for first 2 hours, then hourly 2
- Continuous cardiac monitoring for arrhythmias 1
- Monitor for signs of malignant cerebral edema (especially with right hemiplegia suggesting left MCA territory) 2
- Repeat head CT at 24 hours or immediately if clinical deterioration 2
Critical Pitfalls to Avoid
Do not attempt to "stretch" eligibility criteria for late-window thrombectomy. The guidelines emphasize that DAWN and DEFUSE-3 are the only randomized controlled trials demonstrating benefit beyond 6 hours, and their specific imaging thresholds exist for patient safety. 1 Treating patients who don't meet these criteria exposes them to procedural risks (symptomatic hemorrhage, groin complications, contrast nephropathy) without proven benefit.
Do not delay aspirin administration waiting for potential intervention. Since this patient doesn't qualify for thrombectomy, antiplatelet therapy should begin promptly. 2
Watch for malignant MCA syndrome. Left hemispheric strokes with right hemiplegia carry risk of significant edema; early neurosurgical consultation should be obtained if the patient shows signs of deterioration, as decompressive hemicraniectomy within 48 hours reduces mortality by approximately 50% in younger patients with extensive MCA infarctions. 2
Why Mismatch Ratio Matters
The mismatch ratio represents the volume of hypoperfused tissue divided by the ischemic core volume. A ratio of 1.3 means there is only 30% more hypoperfused tissue than already-infarcted tissue—an insufficient penumbra to justify the risks of late-window intervention. 3, 4 The DEFUSE-3 trial specifically required ≥1.8 because lower ratios did not demonstrate benefit from thrombectomy. 1