Mechanical Thrombectomy for Acute Ischemic Stroke
For patients with acute ischemic stroke due to large vessel occlusion, mechanical thrombectomy combined with intravenous alteplase (when eligible) is the standard of care and should be performed as rapidly as possible, with treatment windows extending up to 24 hours in carefully selected patients based on advanced imaging criteria. 1
Treatment Algorithm by Time Window
Within 0-6 Hours from Symptom Onset
Administer IV alteplase (0.9 mg/kg, maximum 90 mg) immediately if the patient can be treated within 4.5 hours and has no contraindications, with 10% given as bolus over 1 minute and the remainder over 60 minutes 1
Proceed directly to mechanical thrombectomy without waiting to assess response to alteplase in patients with confirmed large vessel occlusion (internal carotid artery or M1 segment of middle cerebral artery) 1
Eligibility criteria for mechanical thrombectomy within 6 hours: age ≥18 years, pre-stroke modified Rankin Scale (mRS) 0-1, NIHSS ≥6, ASPECTS ≥6, and causative occlusion of ICA or MCA-M1 1
Use stent retrievers or direct aspiration as first-line thrombectomy technique, as these second-generation devices demonstrate superior recanalization rates (92%) compared to older devices (24%) 1, 2
Within 6-24 Hours from Last Known Well
Perform mechanical thrombectomy in patients with substantial clinical-imaging mismatch, specifically those meeting DAWN or DEFUSE-3 trial criteria 1, 3
DAWN criteria (up to 24 hours): NIHSS ≥10 with 0-21 mL core infarct (if >80 years) or 0-31 mL core (if <80 years), OR NIHSS ≥20 with 31-51 mL core and age <80 years 1
DEFUSE-3 criteria (up to 16 hours): ischemic core <70 mL, mismatch ratio ≥1.8, and mismatch volume ≥15 mL 1
Consider IV alteplase for patients 4.5-9 hours from onset who have CT or MRI perfusion mismatch and for whom mechanical thrombectomy is not indicated 1
Wake-Up Stroke or Unknown Time of Onset
- Administer IV alteplase within 4.5 hours of symptom recognition if MRI shows DWI-FLAIR mismatch, which identifies patients with stroke onset likely <4.5 hours 1, 4
Critical Technical and Procedural Details
Blood Pressure Management
Lower blood pressure to <185/110 mmHg before initiating IV alteplase in otherwise eligible patients 1
Maintain blood pressure ≤180/105 mmHg during and for 24 hours after mechanical thrombectomy 1
Procedural Goals and Techniques
Target modified TICI grade 2b/3 reperfusion (reperfusion of >50% of the affected territory) as the technical goal of thrombectomy 1
Use proximal balloon guide catheter or large-bore distal access catheter in conjunction with stent retrievers rather than cervical guide catheter alone 1
Direct aspiration (ADAPT) may be used as first-line treatment, with stent retriever thrombectomy as rescue therapy if needed 1
Imaging Requirements
Obtain non-invasive angiography (CTA) immediately in patients with clinically suspected large vessel occlusion 1
Perform advanced imaging (CTP or DWI-MRI) for patients presenting 6-24 hours from last known well to determine thrombectomy eligibility 1
Do not delay IV alteplase for advanced imaging if the patient is within the standard 4.5-hour window 1
Evidence Quality and Strength
The 2023 World Stroke Organization guidelines provide the most current synthesis, showing that mechanical thrombectomy within 6 hours achieves functional independence (mRS 0-2) with a number needed to treat of 4-8 patients 1, 2. The DAWN trial demonstrated a 35.5% absolute increase in functional independence when treating selected patients up to 24 hours, representing the largest treatment effect ever shown in acute stroke trials 3.
The 2018 AHA/ASA guidelines established Class I, Level A evidence for mechanical thrombectomy within 6 hours, and the THRACE trial confirmed that bridging therapy (IV alteplase plus thrombectomy) increases functional independence from 42% to 53% compared to alteplase alone 1, 5.
Common Pitfalls to Avoid
Never delay mechanical thrombectomy to observe clinical response to IV alteplase - this practice is explicitly not recommended and worsens outcomes 1
Do not withhold IV alteplase from thrombectomy candidates - eligible patients should receive both treatments unless alteplase is contraindicated 1
Do not exclude patients based solely on time from onset - use advanced imaging to identify viable tissue in the 6-24 hour window rather than relying on arbitrary time cutoffs 1, 3, 6
Avoid using older mechanical devices (MERCI retrievers) when stent retrievers or aspiration catheters are available, as recanalization rates are significantly lower 1