What are the contraindications for mechanical thrombectomy in patients with severe stroke symptoms, such as high National Institutes of Health Stroke Scale (NIHSS) scores, large infarct cores, bleeding disorders, or significant pre-stroke disability?

Contraindications for Mechanical Thrombectomy

Mechanical thrombectomy has very few absolute contraindications, and current guidelines emphasize expanding access rather than restricting it—the primary barriers are technical feasibility and time windows rather than patient-specific contraindications. 1

Absolute Contraindications

The following represent true contraindications where mechanical thrombectomy should not be performed:

• No large vessel occlusion on angiography - Mechanical thrombectomy requires a documented causative occlusion of the internal carotid artery (ICA) or middle cerebral artery (MCA) M1 segment on non-invasive angiography (CTA) 1
• Absence of salvageable brain tissue - Patients with ASPECTS <6 in the early window (0-6 hours) should not undergo thrombectomy 1
• Lack of appropriate mismatch in extended window - Beyond 6 hours, patients must demonstrate sizable mismatch between ischemic core and hypoperfusion area per DAWN or DEFUSE-3 criteria 1, 2

Relative Contraindications (Not Absolute Barriers)

Clinical Factors That Are NOT Contraindications

Importantly, several factors that clinicians might consider contraindications are actually not barriers to thrombectomy:

• Low NIHSS scores (<6) - While guidelines recommend NIHSS ≥6, research demonstrates mechanical thrombectomy is safe and effective in patients with NIHSS <6 and large vessel occlusions, with decreased mortality and smaller infarct size 3, 4
• High NIHSS scores - Severe strokes (NIHSS >25-30) are not contraindications; these patients may benefit most from intervention 5
• Advanced age (>80 years) - Age alone should not be an exclusion criterion, as elderly patients comprise the majority of stroke victims and may still benefit 5
• Pre-stroke disability (mRS >1) - While guidelines specify mRS 0-1 for standard eligibility, this reflects trial populations rather than absolute contraindications 1

Medical Comorbidities That Are NOT Contraindications

• Contraindications to IV thrombolysis - Patients with bleeding disorders, recent surgery, or other contraindications to IV tPA can safely undergo primary mechanical thrombectomy 6
• Anticoagulation use - Therapeutic anticoagulation is not a contraindication to mechanical thrombectomy, though it may preclude concurrent IV tPA 6

Time-Based Restrictions

• Beyond 24 hours from last known well - No guideline support exists for thrombectomy beyond 24 hours in anterior circulation strokes 1
• 0-6 hours window - Requires ASPECTS ≥6, NIHSS ≥6, confirmed large vessel occlusion, and age ≥18 years 1
• 6-16 hours window - Must meet DAWN or DEFUSE-3 eligibility criteria with advanced perfusion imaging demonstrating salvageable tissue 1, 2
• 16-24 hours window - Only reasonable if meeting DAWN criteria specifically 1

Technical and Facility Requirements

• Lack of experienced stroke center - Treatment requires immediate access to cerebral angiography and qualified interventionalists with proper credentialing 1
• Inability to achieve safe vascular access - Any condition making angiography technically impossible represents a contraindication 5

Important Caveats

The 2012 CHEST guidelines suggested against mechanical thrombectomy (Grade 2C), but this recommendation is obsolete 5. Current 2025 American Heart Association guidelines strongly support mechanical thrombectomy based on overwhelming evidence from multiple randomized trials 1.

Uncompensated hypertension (systolic >180 mmHg or diastolic >100 mmHg on three repeated measures) was listed as a contraindication in older trial design standards 5, but modern practice focuses on blood pressure management rather than exclusion, particularly for mechanical thrombectomy without concurrent IV tPA.

The presence of IV tPA contraindications should never delay or prevent mechanical thrombectomy - these patients can safely undergo primary mechanical thrombectomy with similar recanalization rates and acceptable safety profiles 6.