MedWire News: The presence of asymptomatic embolic signals (ES) on transcranial Doppler imaging predicts future stroke risk in patients with a range of large-vessel diseases, a systematic review and meta-analysis suggests.
The finding supports the use of ES in risk-stratification and as a surrogate marker of antithrombotic therapy efficacy, say Alice King and Hugh Markus, both from St George’s University of London in the UK, writing in the journal Stroke.
Asymptomatic circulating cerebral emboli have been detected in patients with a wide variety of potential embolic sources, such as carotid stenosis, cervical artery dissection, atrial fibrillation, aortic atherosclerosis, fibromuscular dysplasia, and patent foramen ovale.
In this study, King and Markus sought to demonstrate that ES predict stroke risk, noting that this is a prerequisite for the use of ES in directing patient management.
They searched literature databases for studies that used transcranial Doppler to detect ES and included prospective follow-up for the occurrence of stroke or TIA. A total of 30 studies met these criteria and were included in the meta-analysis.
The prevalence of ES in the acute phase after TIA or stroke ranged from 9.3% to 71.0%, the researchers report. Emboli tend to be most frequent in patients with large-artery disease, less frequent in those with cardioembolic stroke, and infrequent or absent in patients with lacunar stroke.
In the eight studies involving patients with acute stroke, the presence of ES predicted the risk for both stroke (odds ratio[OR]=2.4) and the combined endpoint of stroke or TIA (OR=3.71).
In studies of other large-vessel diseases, the presence of ES predicted the risk for stroke in symptomatic carotid stenosis as well as in the immediate postoperative period and during the dissection phase of carotid endarterectomy.
Studies in patients with asymptomatic carotid stenosis were less robust, with conflicting data on the relationship between ES and stroke risk, while no study addressed the relevance of ES in patients with cardioembolic stroke.
King and Markus say that their study confirms the high frequency of ES in patients with potential embolic sources and supports a pathogenic role for embolism in many stroke subtypes.
“This review provides strong evidence that ES predicts future ipsilateral stroke risk in patients with large-artery disease, particularly symptomatic carotid stenosis,” they conclude.
“Data are promising in asymptomatic carotid stenosis, although further studies are required. In other conditions, further prospective data are required.”
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