A 68-year-old man presents with a 2-week history of transient monocular blindness (amaurosis fugax) in the left eye. Carotid duplex ultrasound with spectral Doppler is performed. The structure marked **B** in the diagram shows an elevated peak systolic velocity of 245 cm/s in the left internal carotid artery, with an end-diastolic velocity of 110 cm/s and an ICA/CCA PSV ratio of 4.2. According to the SRU consensus criteria, what degree of stenosis does this Doppler finding indicate?

Question

Accepted Answer

B. >70% stenosis (but not near-occlusion). ## Why >70% stenosis (but not near-occlusion) is right The structure marked **B** represents the peak systolic velocity (PSV) measurement in the internal carotid artery. According to the internationally validated SRU consensus criteria cited in the AHA/ASA 2021 stroke prevention guidelines, a PSV >230 cm/s (in this case 245 cm/s), combined with an end-diastolic velocity >100 cm/s (here 110 cm/s) and an ICA/CCA PSV ratio >4.0 (here 4.2), definitively indicates >70% stenosis but not near-occlusion. This degree of stenosis in a symptomatic patient (amaurosis fugax within 2 weeks) meets the criteria for urgent carotid endarterectomy per NASCET trial evidence. ## Why each distractor is wrong - **50–69% stenosis**: This grade is characterized by PSV 125–230 cm/s. The patient's PSV of 245 cm/s exceeds this threshold, placing him in a higher stenosis category. - **Near-occlusion with variable velocities**: Near-occlusion is defined by a markedly narrowed lumen with variable (often paradoxically low) velocities due to severely reduced flow. This patient has consistently elevated velocities (PSV 245, EDV 110), indicating high-grade but not near-occlusion stenosis. - **<50% stenosis**: This grade is defined by PSV <125 cm/s. The patient's PSV of 245 cm/s is nearly twice this threshold. **High-Yield:** PSV >230 cm/s + EDV >100 cm/s + ICA/CCA ratio >4.0 = >70% stenosis on carotid duplex; symptomatic patients with this finding require urgent CEA within 2 weeks (NASCET). [cite: SRU consensus criteria for carotid stenosis grading; AHA/ASA 2021 Stroke Prevention Guidelines; NASCET trial]

Answer

A. 50–69% stenosis

Answer

C. <50% stenosis

Answer

D. Near-occlusion with variable velocities

Explanation

Why >70% stenosis (but not near-occlusion) is right

Why each distractor is wrong

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