A 68-year-old man with hypertension, smoking history, and hyperlipidemia presents with a 2-hour history of transient monocular blindness (amaurosis fugax) in the left eye. Duplex ultrasound of the left carotid artery shows a heterogeneous atherosclerotic plaque at the bifurcation with the parameter marked **B** (Peak Systolic Velocity) measured at 245 cm/s. Which of the following best describes the hemodynamic significance of this finding and its clinical implication?

Explanation

## Why "≥70% internal carotid artery stenosis with indication for carotid endarterectomy within 2 weeks of symptom onset" is right Peak Systolic Velocity (PSV) > 230 cm/s is the Doppler ultrasound criterion for ≥70% internal carotid artery (ICA) stenosis per the Society of Radiologists in Ultrasound (SRU) 2003 consensus criteria. A PSV of 245 cm/s unequivocally indicates ≥70% stenosis. The patient is symptomatic (amaurosis fugax—transient monocular blindness from retinal artery embolism via the ophthalmic artery branch of the ICA) within the past 6 months. According to the NASCET trial, symptomatic patients with 70–99% stenosis derive significant benefit from carotid endarterectomy (CEA), with a relative risk reduction of 65% for stroke prevention. Critically, CEA is most effective when performed within 2 weeks of the index event (TIA or stroke) to maximize benefit. This patient meets the indication for urgent CEA. ## Why each distractor is wrong - **50–69% internal carotid artery stenosis; medical therapy alone is sufficient without intervention**: PSV in the 50–69% stenosis range is 125–230 cm/s. A PSV of 245 cm/s exceeds this threshold and indicates ≥70% stenosis, not 50–69%. This misinterprets the Doppler criterion. - **<50% internal carotid artery stenosis; no intervention required; continue best medical therapy**: PSV < 125 cm/s defines <50% stenosis. A PSV of 245 cm/s is far above this threshold and indicates significant hemodynamic stenosis requiring intervention in the symptomatic setting. - **Near-occlusion of the internal carotid artery; revascularization is contraindicated and medical therapy is the only option**: Near-occlusion presents with markedly narrowed lumen and may show low or paradoxically high velocities with a dampened waveform. While PSV > 230 cm/s can occur in near-occlusion, the clinical context (heterogeneous plaque, clear Doppler criteria, symptomatic presentation) and the specific PSV value of 245 cm/s fit the ≥70% stenosis category. Near-occlusion is indeed not amenable to revascularization, but this patient's findings are consistent with severe but not near-occlusive stenosis. **High-Yield:** PSV > 230 cm/s = ≥70% ICA stenosis = CEA within 2 weeks if symptomatic (NASCET: NNT 8 to prevent 1 stroke at 5 years). [cite: Rumack Diagnostic Ultrasound 6e Ch 26; Rutherford's Vascular Surgery 9e Ch 84; NASCET / CREST trials]