What stenosis percentage defines high-grade symptomatic carotid disease in the commonly cited threshold?

• A. 60%
• B. 80%
• C. 50%
• D. 70%

Answer: (D)

In symptomatic carotid disease, how narrow the artery is guides treatment decisions, with the biggest benefit from surgery seen when the narrowing is substantial. The commonly cited threshold for high-grade symptomatic disease is 70% stenosis, as measured by the NASCET method. This method compares the narrowing to the normal distal internal carotid artery, and studies show that in patients with recent ipsilateral symptoms, endarterectomy significantly lowers the risk of recurrent stroke when stenosis is 70% or greater (70–99%). For moderate stenosis (roughly 50–69%), the benefit exists but is smaller and more variable, and for less than 50% the advantage of surgery is limited. Keep in mind that different measurement methods (like ECST) can yield different percentages, but 70% by NASCET is the standard threshold used to define high-grade symptomatic disease.