Carotid stenosis, or narrowing of the carotid artery, is a cause of stroke and transient ischaemic attack (TIA). An ultrasound procedure that detects cerebral emboli (small blood clots and plaque that break off from the narrowing in the carotid arteries) can identify symptom-free patients with carotid stenosis who are at a higher risk of stroke and TIA, and also those with a low stroke risk. These findings suggest that transcranial doppler ultrasound, which is a non-invasive and inexpensive technique, might be useful for selecting patients most likely to benefit from endarterectomy (surgery to clear blockages), concludes an Article to be presented at the European Stroke Conference meeting in Barcelona and published Online First and in the June edition of the Lancet Neurology.
Endarterectomy is the standard treatment for patients who have symptoms of an impending stroke (symptomatic carotid stenosis), and has been shown to reduce stroke risk by up to 75% in these patients. However, the benefit of surgery to prevent stroke in patients with no pre-existing symptoms is less clear.
Most patients with carotid stenosis will not have a TIA or minor stroke before a disabling stroke, and the majority of patients with asymptomatic carotid stenosis benefit from intensive medical therapies such as lifestyle changes rather than surgery. Therefore, finding better techniques to identify the small group of asymptomatic patients most likely to develop stroke who would benefit most from surgery is important, and would spare those patients at low risk of stroke an operation which itself can cause stroke.
Hugh Markus from St George's University of London and international colleagues established the asymptomatic carotid emboli study (ACES) to investigate whether ultrasound can be used to detect cerebral emboli* and predict stroke risk in patients with asymptomatic carotid stenosis. 482 patients whose carotid arteries were narrowed by at least 70%, but who had no symptoms, were recruited from 26 centres worldwide. Patients had two 1-hour transcranial doppler ultrasound (TCD) recordings at the start of the study and repeat one 1-hour recordings at 6, 12, and 18 months. Ipsilateral stroke and TIA were measured up to 2 years after the start of the study.
Overall, findings showed that over 2 years patients with embolic signals were two and a half times more likely to have an ipsilateral stroke or TIA than those without.
Additionally, the annual risk of stroke or TIA in patients with embolic signals was 7.13% compared with only 3.04% in those without. The annual risk of stroke alone in patients who did not have embolic signals was less than 1% (0.70% vs 3.04%). The authors point out that at this low level of risk surgery would not be beneficial and might in fact incur risk.
Controlling for traditional risk factors for stroke including age, blood pressure, and percent of the carotid that was blocked did not alter the results and supports the use of embolic signals as an independent predictor of stroke risk.
The authors comment: "ACES shows that detection of embolic signals by TCD can identify groups of patients with asymptomatic carotid stenosis who are at low or high risk of future stroke. This technique might be a useful risk predictor for identifying those patients who might benefit from intervention with carotid endarterectomy."
Professor Hugh Markus, St George's University of London, London, UK. T) +44 (0)7812405547 E) hmarkus@sgul.ac.uk
For full Article see: http://press.thelancet.com/tlnaces.pdf
Notes to Editors *Previous studies have shown that the presence of clinical embolism is a good predictor of future stroke risk in symptomatic carotid stenosis, and the detection of embolic signals using ultrasound could also be predictive of transient ischaemic attack (TIA) and stroke risk in asymptomatic carotid stenosis.
Journal
The Lancet Neurology