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Asymptomatic embolization predicts stroke and TIA risk in patients with carotid artery stenosis
1Department of Clinical Neurosciences, Guy's, Kings and St Thomas' School of Medicine and the Institute of Psychiatry, London, UK.
Insights
Detecting asymptomatic emboli using Doppler ultrasound in patients with carotid artery stenosis identifies those at high risk for stroke. This method aids in selecting patients who may benefit most from carotid endarterectomy.
Area of Science:
- Neurology
- Vascular Surgery
- Diagnostic Imaging
Background:
- Carotid artery stenosis increases stroke risk, necessitating improved patient stratification for therapy.
- Current risk-benefit assessment for carotid endarterectomy is challenging, especially for asymptomatic or moderately symptomatic stenosis.
- Embolic events are a primary cause of stroke in carotid stenosis patients.
Purpose of the Study:
- To evaluate Doppler ultrasound for detecting asymptomatic cerebral emboli in carotid stenosis patients.
- To identify a high-risk subgroup for targeted intervention.
- To correlate embolic signals with clinical and angiographic markers of stroke risk.
Main Methods:
- Transcranial Doppler ultrasound monitored the middle cerebral artery in 111 patients with >60% carotid stenosis for one hour.
- Doppler audio signals were analyzed for embolic signals (ES) by a blinded observer.
- Prospective follow-up assessed the relationship between ES and subsequent ipsilateral ischemic events (TIA and stroke).
- Plaque ulceration was investigated in relation to ES in 67 subjects.
Main Results:
- Embolic signals (ES) were detected in 36.9% of patients.
- ES were more frequent in patients with plaque ulceration (RR 4.94, P=0.025).
- The presence of ES predicted future TIA and stroke risk in both symptomatic (P=0.02) and asymptomatic (P=0.007) patients.
- Asymptomatic embolization independently predicted ischemic events (aOR 8.10, P=0.01) after adjusting for multiple risk factors.
Conclusions:
- Asymptomatic embolization in carotid stenosis is an independent predictor of future stroke.
- Detection of ES correlates with established stroke risk markers.
- This technique may identify patients who would most benefit from carotid endarterectomy, warranting further multicenter validation.
Background And Purpose:
Improved methods of identifying patients at high risk of thromboembolism would allow improved targeting of therapy. One such situation is carotid artery stenosis. This is associated with an increased risk of stroke, which can be reduced by carotid endarterectomy. However, the risk-benefit ratio is low in patients with tight asymptomatic stenosis and moderate symptomatic stenosis. Most stroke in patients with carotid stenosis is believed to be embolic. Therefore, the detection of asymptomatic cerebral emboli using Doppler ultrasound may allow identification of a high-risk group.
Methods:
Transcranial Doppler ultrasound was used to record for 1 hour the ipsilateral middle cerebral artery in 111 patients with >60% carotid artery stenosis (69 symptomatic, 42 asymptomatic). The Doppler audio signal was recorded onto digital audio tape for later analysis for embolic signals (ES) by an individual blinded to clinical details. In 67 subjects the relationship between ES and angiographically determined plaque ulceration was investigated. All subjects were followed up prospectively, and the relationship between ES and risk of future ipsilateral carotid artery territory ischemic events (TIA and stroke) was determined.
Results:
ES were detected in 41(36.9%) subjects. In symptomatic patients there was a significant inverse relationship between the number of ES per hour and time elapsed since last symptoms (Spearman's rho=-0.2558, P=0.034). ES were more common in subjects with plaque ulceration, with a relative risk of 4. 94 (95% CI, 1.23 to 19.84; P=0.025) after controlling for both symptomatic status and degree of stenosis. The presence of ES at entry was predictive of TIA and stroke risk during follow up in both symptomatic (P=0.02) and asymptomatic patients (P=0.007). Considering all 111 patients, the presence of asymptomatic embolization was predictive of a further ischemic event, with an adjusted OR of 8.10 (95% CI, 1.58 to 41.57; P=0.01) after controlling for other cardiovascular risk factors, degree of stenosis, symptomatic status, and aspirin or warfarin use.
Conclusions:
Asymptomatic embolization in patients with carotid artery stenosis correlates with known markers of increased stroke risk and is an independent predictor of future stroke risk in patients with both symptomatic and asymptomatic carotid stenosis. It may allow identification of a high-risk group of patients who will particularly benefit from carotid endarterectomy. A large multicenter study is now required to confirm these findings.