(Stroke. 1999;30:1440-1443.)
© 1999 American Heart Association, Inc.
Original Contributions |
Asymptomatic Embolization Predicts Stroke and TIA Risk in Patients With Carotid Artery Stenosis
From the Department of Clinical Neurosciences, Guy's, Kings and St Thomas' School of Medicine and the Institute of Psychiatry, London, UK.
Correspondence to Dr Hugh Markus, Reader in Neurology, Department of Clinical Neurosciences, Institute of Psychiatry, De Crespigny Park, London, UK SE5 8AF. E-mail h.markus{at}iop.kcl.ac.uk
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 
=-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.
Key Words: carotid artery diseases • cerebral embolism • stroke • ultrasonography
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