Detection of asymptomatic embolization by use of transcranial Doppler ultrasound (TCD) can be used to identify patients with asymptomatic carotid stenosis who are at a higher risk of stroke and transient ischemic attack, and also for patients with a low absolute stroke risk, according to the ACES study published in the June edition of Lancet Neurology.
Hugh S. Markus, FRCP, professor of clinical neuroscience at St. George's University of London, and colleagues explained that the benefits of surgery for patients with asymptomatic carotid stenosis has been debated, and that better methods of identifying patients who are likely to develop stroke would improve the risk–benefit ratio for carotid endarterectomy.
The prospective study—Asymptomatic Carotid Emboli Study (ACES)—observed 467 patients with asymptomatic carotid stenosis of at least 70 percent across 26 healthcare facilities globally. To detect the presence of embolic signals, patients underwent two one-hour TCD recordings from the ipsilateral middle cerebral artery at baseline and another one-hour recording at six, 12, and 18 months.
The patients were followed for two years and all recordings were analyzed by researchers who were blinded to patient identity, said the authors.
With the primary endpoints determined to be ipsilateral stroke and transient ischemic attack, embolic signals were present in 77 of 467 patients at the baseline recording.
According to the researchers, these patients presented a hazard ratio for the risk of ipsilateral stroke and transient ischemic attack 2.54 times greater than those without embolic signals at baseline. The annual risk of ipsilateral stroke or transient ischemic attack in patients with embolic signals was 7.13 percent compared with 3.04 percent in those without. The annual risk of ipsilateral stroke alone in patients who did not have embolic signals was 0.70 percent.
In patients presenting with embolic signals on the recording prior to the next six-month follow-up, the hazard ratio for the risk of ipsilateral stroke and transient ischemic attack was 2.63 percent higher than in those without. The researchers noted that antiplatelet therapy, degree of stenosis and other risk factors did not alter results of the study.
While Markus and colleagues noted that further work is needed in the development of more sensitive systems, they concluded: “Assessment of the presence of embolic signals on TCD might be useful in the selection of patients with asymptomatic carotid stenosis who are likely to benefit from endarterectomy…and also to identify patients at low risk in whom surgical intervention will not be beneficial.”