Asymptomatic carotid stenosis: intervention or just stick to medical therapy--the case for medical therapy.

Asymptomatic significant (≥50%) carotid stenosis (ASCS) is a frequent finding in the aging population. The prevalence of moderate stenosis (50-70%) increases from 3.6% for those <70 years to 9.3% in those ≥70 years. The (additional) prevalence of severe (70-99%) stenosis is 1.7%. The natural history of ASCS is quite benign. The overall risk of stroke is around 2% per year and within the group higher degrees of stenosis are associated with higher risks. Yet this stroke risk also includes "unrelated" strokes (i.e., lacunar and cardioembolic), and similarly, it is more of a marker for identifying high-risk group of patients at risk of cardiovascular morbidity and mortality (as revealed by many studies)! Carotid endarterectomy (CEA) has been evaluated in several studies; mainly ACAS and ACST. An overall modest benefit of about 1% risk reduction (per year) was found for CEA (with a peri-operative risk of <3%) versus medical treatment, over a 5-year period. Basically these two studies recruited similar patients with ≥60% stenosis based on carotid duplex. However, the similar favorable results differ: while ACAS (published in 1995) found the risk for ipsilateral stroke in the medical group to be 11% over a 5-year period, the 11.8% risk observed in ACST (published in 2004) was for any strokes--showing a better "natural history" for patients with ASCS in the recent study. This observation adds to other reports suggesting a better outcome for patients with ASCS in the recent years, probably because of better medical treatment, mainly due to the significant increase in the use of statins. The suggested guideline that results from the above-mentioned studies is that CEA should be considered in every patient with significant (≥60%?, ≥70%?) stenosis who has a life expectancy of more than 5 years (and is <75 years?). Taking this advice as such, would mean that we should screen for ASCS and operate on all appropriate candidates. This will result in a surge of CEA's! Such a recommendation is not in place, because the observed benefit of CEA by numbers needed to treat (NNT) per year to prevent any stroke is more than one hundred! (for symptomatic patients NNT is <10). This high-figure (i.e., low yield) results from failure of these studies to identify specific risk-factors (including the degree of stenosis within the wide range [60-99%] allowed in the studies) in patients with ASCS. Some studies are underway. Therefore, at present, it seems that for most patients, best (intensive) medical treatment is the best option. Alternately, they should join studies that will help to identify patients with the highest risk--those who will clearly benefit from carotid intervention.