What is the difference between MRCA (Mechanical Retrieval Catheter Aspiration) devices and stent retrieval devices in the treatment of ischemic stroke?

Aspiration vs Stent Retriever Devices in Acute Ischemic Stroke

Direct Answer

Both direct aspiration (ADAPT technique) and stent retriever devices are acceptable first-line strategies for mechanical thrombectomy in acute ischemic stroke, with no significant difference in functional outcomes, recanalization rates, symptomatic hemorrhage, or mortality. 1

Key Evidence from Guidelines

Equivalence Between Techniques

The most recent 2024 European Stroke Organisation (ESO) and European Society for Minimally Invasive Neurological Therapy (ESMINT) guidelines analyzed pooled data comparing direct aspiration versus stent retrievers as first-line strategies in basilar artery occlusion and found:

• No significant difference in good functional outcome (mRS 0-3 at 3 months) 1
• No significant difference in favorable functional outcome (mRS 0-2 at 3 months) 1
• No significant difference in successful recanalization (mTICI 2b-3) 1
• No significant difference in symptomatic intracranial hemorrhage 1
• No significant difference in 90-day mortality 1

Stent Retrievers Remain First Choice

The 2018 American Heart Association/American Stroke Association (AHA/ASA) guidelines established that:

• Stent retrievers are preferred over older devices like the MERCI retriever (Class I; Level of Evidence A) 1
• Aspiration devices may be reasonable as first-line devices in some circumstances, but stent retrievers remain the first choice (Class IIb; Level of Evidence B-R) 1

The ASTER trial compared contact aspiration versus stent retrievers and found:

• Successful revascularization: 85.4% with aspiration vs 83.1% with stent retrievers (no significant difference, p=0.53) 1
• Good functional outcome (mRS 0-2): 45.3% with aspiration vs 50.0% with stent retrievers (no significant difference, p=0.38) 1

Important caveat: ASTER was designed to detect a 15% difference and was not powered for noninferiority, so smaller clinically important differences cannot be excluded 1

Practical Algorithm for Device Selection

First-Line Approach

1. Start with stent retriever devices (Solitaire FR, Trevo) as they have the strongest evidence base from pivotal trials 1, 2, 3, 4
2. Consider direct aspiration (ADAPT) as an acceptable alternative, particularly when:
   • Operator has extensive experience with aspiration technique 1
   • Clot characteristics suggest soft, fresh thrombus amenable to aspiration 1

Rescue Strategy

• If first-line technique fails, switch to the alternative approach (aspiration after failed stent retriever, or vice versa) 1
• Combined techniques (aspiration + stent retriever) may be used when initial attempts are unsuccessful 1

Technical Considerations

• Use proximal balloon guide catheter or large-bore distal-access catheter with stent retrievers rather than cervical guide catheter alone (Class IIa; Level of Evidence C) 1
• Target TICI 2b/3 recanalization as the technical goal to maximize functional outcomes (Class I; Level of Evidence A) 1
• Minimize number of thrombectomy passes as fewer maneuvers correlate with better clinical outcomes 5

Device Performance Characteristics

Stent Retrievers (Solitaire, Trevo)

• Recanalization rates: 82-86% achieving TICI 2a-3 2, 4
• Good functional outcomes: 47-51% achieving mRS 0-2 at 90 days 2
• Mortality: 14-31% at 90 days 2
• Symptomatic hemorrhage: 6-8% 2
• Mechanism: Deploy within thrombus to immediately restore flow, then retrieve clot with stent 1, 2, 3

Direct Aspiration

• Recanalization rates: 85% achieving TICI 2b-3 1
• Good functional outcomes: 45% achieving mRS 0-2 at 90 days 1
• Mechanism: Direct suction through large-bore aspiration catheter 1

Critical Time Considerations

• Groin puncture should occur within 6 hours of symptom onset for anterior circulation strokes 1
• Do NOT observe patients after IV tPA to assess clinical response before pursuing endovascular therapy—this delays treatment and worsens outcomes (Class III; Level of Evidence B-R) 1
• Reduced time to reperfusion is highly correlated with better outcomes regardless of device type 1

Common Pitfalls to Avoid

1. Using outdated devices: The MERCI retriever is inferior to stent retrievers and should not be used (Class I; Level of Evidence A) 1

2. Excessive thrombectomy attempts: Multiple passes increase procedure time and worsen outcomes—switch techniques or use combined approach if initial attempts fail 5

3. Inadequate recanalization: Accepting TICI 2a or lower results in worse outcomes; use salvage adjuncts (including intra-arterial fibrinolysis within 6 hours) to achieve TICI 2b/3 1

4. Delaying for imaging: While patient selection is important, excessive delays for additional imaging reduce the benefit of any thrombectomy technique 1

Rescue Stenting Considerations

When thrombectomy fails due to underlying intracranial atherosclerotic disease (ICAD):

• Rescue PTA and/or stenting may be considered as a bailout strategy (Class IIb; Level of Evidence B-R) 6
• Must be completed within 6 hours of symptom onset 6
• Lower symptomatic hemorrhage rates (4.2%) compared to failed EVT without rescue (14.2%, p=0.002) 1

Critical contraindication: Do NOT perform angioplasty/stenting as initial treatment for severe intracranial stenosis—this causes excess harm (Class III: Harm; Level of Evidence A) 6