Emboli detection in asymptomatic carotid stenosis

摘要

We read with interest the results of the Asymptomatic Carotid Emboli Study (ACES). A screening method to identify high-risk patients with asymptomatic carotid disease has long been awaited, and the investigators should be congratulated for this elegant and difficult study; however, I have two heretic questions. First, what were patients at high risk for? I presume for symptomatic conversion (the investigators wisely included transient ischaemic attacks [TIAs] along with strokes in their primary endpoint, and showed that asymptomatic stenoses convert to symptomatic stenoses at a rate of 3-8% per year). The investigators state twice in the Article that despite the small absolute benefit from revascularisation procedures, asymptomatic stenoses account for a large burden of stroke because most strokes are not preceded by TIAs. However, the study proves exactly the opposite: TIAs were four times more frequent than were strokes, four of ten strokes were preceded by TIAs, and furthermore, for unspecified reasons, these four patients were not offered immediate endarterectomy. This point is crucial to interpret the results of the study. If we assumed that all 77 emboli-positive (ie, high-risk) patients underwent endarterectomy with an almost perfect perioperative risk of stroke or death of 1%, we would prevent four strokes (five on study, minus one perioperative), and the number needed to treat would be 19.