Published Online
on May 5, 2005

A more recent version of this article appeared on June 1, 2005

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Submitted on February 4, 2005
Revised on February 4, 2005
Accepted on February 24, 2005

Embolic Signals And Prediction of Ipsilateral Stroke or Transient Ischemic Attack in Asymptomatic Carotid Stenosis. A Multicenter Prospective Cohort Study

Anne L. Abbott PhD^*; Brian R. Chambers MD; Jacinda L. Stork PhD; Christopher R. Levi MBBS; Christopher F. Bladin MD; and Geoffrey A. Donnan MD

From the National Stroke Research Institute (A.L.A., B.R.C., J.L.S., G.A.D.), Austin Health, Melbourne, Australia; the University of Melbourne (A.L.A., B.R.C., J.L.S., G.A.D.), Australia; the Department of Neuroscience (C.R.L.), John Hunter Hospital, Newcastle, Australia; the Department of Neuroscience (A.L.A., C.F.B.), Box Hill Hospital, Melbourne, Australia; and the Neurology Department (A.L.A., B.R.C., J.L.S., G.A.D.), Austin Health, Melbourne, Australia.

^* To whom correspondence should be addressed. E-mail: a.abbott{at}nsri.org.au.

Background and Purpose--We tested the hypothesis that transcranial Doppler embolic signal (ES) detection identifies an increased risk of ipsilateral carotid stroke or transient ischemic attack (TIA) in subjects with asymptomatic severe carotid stenosis.

Methods--Subjects with duplex-determined 60% to 99% carotid stenosis, without other apparent cerebroembolic sources, underwent 6-monthly neurological assessment and 60-minute ES monitoring. ES positivity was defined as 1 ES detected in 1 study, ES negativity as no ES in any study, and consistent ES negativity as no ES in any study where 6 studies were performed. Rates of ipsilateral carotid stroke/TIA were calculated using Kaplan-Meier analysis and correlated with ES status using odds ratios (ORs) and Cox proportional hazards regression analysis.

Results--A total of 202 subjects (138 male; mean age 74 years; mean follow-up 34 months) were recruited. The average annual rate of ipsilateral carotid stroke/TIA was 3.1%. A total of 231 arteries were monitored at least once (mean 4.3 studies/artery). Six of 60 (10.0%) ES-positive arteries had an ipsilateral carotid stroke/TIA compared with 12 of 171 (7.0%) ES-negative arteries (OR, 1.47; 95% CI, 0.43, 4.48; P=0.624) and 2 of 41 (4.9%) consistently ES-negative arteries (OR, 2.17; 95% CI, 0.36, 22.90; P=0.59). Differences in survival free of ipsilateral carotid stroke/TIA according to ES status were not statistically significant.

Conclusions--Although there were more ipsilateral carotid cerebrovascular events among ES-positive arteries, this was not statistically significant. Less labor-intensive techniques are required to make further study and clinical application practical.

Key words: carotid stenosis • embolic signal • risk • stroke • transcranial Doppler

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