What is LVO (Large Vessel Occlusion)?
LVO stands for Large Vessel Occlusion, which refers to the blockage of major intracranial arteries—specifically the intracranial carotid artery, M1 segment of the middle cerebral artery, and basilar artery—causing acute ischemic stroke with devastating neurological consequences. 1
Clinical Significance
- LVO accounts for up to 38% of acute ischemic strokes and represents the most severe form of ischemic stroke requiring urgent intervention 2
- These occlusions are less likely to recanalize with intravenous alteplase alone and require consideration for endovascular thrombectomy (EVT) 1
- Posterior circulation LVOs (pc-ELVO) are rarer, representing only 1% of all ischemic strokes and 5% of all LVOs, but carry particularly poor outcomes with only 20% achieving good functional outcomes despite advanced care 1
Anatomical Definition
- Anterior circulation LVOs include occlusions of the intracranial internal carotid artery and M1 segment of the middle cerebral artery 1
- Posterior circulation LVOs involve the basilar artery and vertebral arteries 1
- Distal occlusions (M2 and beyond) have higher probability of recanalization with alteplase but are increasingly treated with EVT as well 1
Why LVO Identification Matters
- Treatment is highly time-dependent—outcomes are directly related to speed of reperfusion and quality of recanalization 1
- LVO patients are candidates for both intravenous alteplase AND endovascular thrombectomy, unlike smaller vessel occlusions 1
- Rapid identification allows for direct transport to EVT-capable centers, bypassing primary stroke centers that cannot perform thrombectomy 1
Detection Methods
- Gold standard diagnosis requires vascular imaging with CT angiography (CTA), magnetic resonance angiography (MRA), or conventional angiography 1
- CTA has high accuracy for LVO detection with excellent interrater reliability, covering both extra- and intracranial vasculature in one sequence 1
- Clinical prediction scales (NIHSS, RACE, LAMS) are used for prehospital triage but no scale achieves both high sensitivity and high specificity—sensitivity reaches 87% and specificity 90% at best, but not simultaneously 1
Common Pitfall
- The term "large vessel" is anatomically specific—it does NOT simply mean "big clot" or "severe stroke" but refers to the specific proximal arterial locations listed above 1