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06-06-2010 | Stroke | Article

Embolic signals identify high-risk asymptomatic carotid stenosis patients


Free abstract

MedWire News: Screening patients with asymptomatic carotid stenosis for embolic signals on transcranial Doppler (TCD) may help to identify those in need of endarterectomy, suggest results of the ACES study.

The benefits and cost-effectiveness of surgery in patients with asymptomatic carotid stenosis are controversial, yet the condition accounts for a large proportion of strokes.

“Only 15% of strokes are preceded by transient ischemic attack (TIA) and therefore waiting for stenoses to become symptomatic fails to prevent most strokes caused by carotid stenosis,” say Hugh Markus (St George’s University of London, UK) and colleagues.

The team’s findings, reported in The Lancet Neurology, highlight one method of identifying patients who are most likely to benefit from surgery.

The ACES (Asymptomatic Carotid Emboli Study) included 467 patients, from 26 centers worldwide, who had at least 70% carotid stenosis, but no symptoms. During 2 years of follow-up, 32 patients suffered ipsilateral stroke (n=6) or TIA (n=26).

TCD screening at baseline (two 1-hour recordings, assessed by researchers blinded to patient outcomes) detected asymptomatic emboli in 77 patients. During follow-up, the absolute annual risk for ipsilateral stroke or TIA was 7.13% in patients with emboli, compared with 3.04% in those without. This equated to a 2.54-fold increased risk in patients with emboli.

The annual ipsilateral stroke risk was 3.62% versus 0.70% in patients with and without emboli, respectively, equating to a 5.57-fold risk increase in patients with emboli. Accounting for age, gender, antiplatelet therapy, hypertension, diabetes, smoking, and degree of stenosis did not weaken the association between emboli and stroke risk.

The researchers note that the less than 1% stroke rate among patients without emboli is lower than in earlier trials, and is consistent with advances in medical therapy.

“At this level of risk carotid endarterectomy is not associated with benefit and might actually incur risk,” they add.

Markus et al also conducted a meta-analysis that included five other studies. They found that, overall, the presence of embolic signals was associated with a 6.63-fold increase in the risk for ipsilateral stroke and a 7.57-fold increase in ipsilateral stroke or TIA risk.

“If TCD is to be used as a clinical tool for risk stratification, improved methods of automated detection of embolic signals are needed,” say the researchers.

“TCD recording itself is simple, non-invasive, and widely used in clinical practice worldwide. However, review of data for the presence of embolic signals is time consuming and relies on trained observers.”

MedWire ( is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2010

By Eleanor McDermid