Published Online
on October 13, 2005

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

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Submitted on February 26, 2005
Revised on July 5, 2005
Accepted on August 6, 2005

Absence of Microemboli on Transcranial Doppler Identifies Low-Risk Patients With Asymptomatic Carotid Stenosis

J. David Spence MD^*; Arturo Tamayo MD; Stephen P. Lownie MD; Wai P. Ng MD; and Gary G. Ferguson MD, PhD

From the Stroke Prevention & Atherosclerosis Research Centre (J.D.S., A.T.), Robarts Research Institute, and the London Health Sciences Centre (J.D.S., S.P.L., W.P.N., G.G.F.), University of Western Ontario, London, Canada; currently at the University of Manitoba (A.T.), Winnipeg, Canada.

^* To whom correspondence should be addressed. E-mail: dspence{at}robarts.ca.

Background and Purpose--Carotid endarterectomy clearly benefits patients with symptomatic severe stenosis (SCS), but the risk of stroke is so low for asymptomatic patients (ACS) that the number needed to treat is very high. We studied transcranial Doppler (TCD) embolus detection as a method for identifying patients at higher risk who would have a lower number needed to treat.

Methods--Patients with carotid stenosis of 60% by Doppler ultrasound who had never been symptomatic (81%) or had been asymptomatic for at least 18 months (19%) were studied with TCD embolus detection for up to 1 hour on 2 occasions a week apart; patients were followed for 2 years.

Results--319 patients were studied, age (standard deviation) 69.68 (9.12) years; 32 (10%) had microemboli at baseline (TCD+). Events were more likely to occur in the first year. Patients with microemboli were much more likely to have microemboli 1 year later (34.4 versus 1.4%; P<0.0001) and were more likely to have a stroke during the first year of follow-up (15.6%, 95% CI, 4.1 to 79; versus 1%, 95% CI, 1.01 to 1.36; P<0.0001).

Conclusions--Our findings indicate that TCD- ACS will not benefit from endarterectomy or stenting unless it can be done with a risk <1%; TCD+ may benefit as much as SCS if their surgical risk is not higher. These findings suggest that ACS should be managed medically with delay of surgery or stenting until the occurrence of symptoms or emboli.

Key words: asymptomatic carotid stenosis • endarterectomy • transcranial Doppler • ulcer • ultrasound • unstable plaque

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