Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.

A 67-year-old man is evaluated for a carotid bruit detected on routine medical examination. He reports no history of previous focal neurologic symptoms or visual loss. He has type 2 diabetes mellitus and hyperlipidemia treated with metformin, moderate-intensity pravastatin, and aspirin.

On physical examination, blood pressure is 128/64 mm Hg, pulse rate is 78/min and regular, and respiration rate is 16/min. A left carotid bruit is heard on cardiac examination. All other physical examination findings, including those from a neurologic examination, are unremarkable.

Results of laboratory studies show an LDL cholesterol level of 82 mg/dL (2.12 mmol/L).

The carotid ultrasound report describes a mixed-density plaque at the origin of the left internal carotid artery with stenosis estimated to be 60% to 80%.

Which of the following is the most appropriate next step in management?

A. Carotid endarterectomy
B. Carotid stenting
C. Magnetic resonance angiography of the neck
D. Replacement of aspirin with clopidogrel
E. No further treatment or intervention

MKSAP Answer and Critique

The correct answer is E. No further treatment or intervention.

This patient with 60% to 80% stenosis of the left internal carotid artery should receive no further treatment or intervention. The patient’s LDL cholesterol level indicates that his atherogenic dyslipidemia is adequately treated with pravastatin, a moderate-intensity statin. Although there is some evidence suggesting that his 10-year risk for a major cardiovascular event is high enough to warrant switching to a high-dose, high-intensity statin, there are no specific guidelines recommending such a change. Asymptomatic carotid artery stenosis was not included in the definition of atherosclerotic cardiovascular disease used in the latest dyslipidemia treatment targets. Data are insufficient among patients with asymptomatic disease to recommend a specific therapy beyond treatment with a statin; there is currently no consensus on which statin and what dose to use.

Carotid endarterectomy or stenting is not the best treatment for this patient. The patient has asymptomatic internal carotid artery stenosis of 60% to 80%; the risk of stroke with best medical therapy is very low. Carotid revascularization with either endarterectomy or stenting, on the other hand, has a higher risk of adverse effects, including stroke, and its absolute risk reduction of stroke in asymptomatic patients is small, particularly among patients with stenosis of 80% or less. According to previous studies, predictors of stroke with asymptomatic internal carotid artery stenosis include greater than 80% stenosis, asymptomatic infarcts on brain imaging, an abnormal transcranial Doppler ultrasound study, or rapid progression. Carotid revascularization should be considered in patients at low risk for perioperative cardiovascular morbidity who have greater than 80% stenosis only in the context of a clinical trial.

Magnetic resonance angiography (MRA) of the neck is inappropriate because an additional diagnostic test is unlikely to change medical management. The accuracy of MRA without contrast versus carotid ultrasound is likely similar, but neck MRA is associated with patient discomfort and a higher cost.

Because there is no clear evidence that clopidogrel is superior to aspirin for the primary prevention of stroke in the setting of asymptomatic internal carotid artery stenosis, replacing this patient’s aspirin with clopidogrel is unwarranted.

Key Point

• Statin therapy is indicated for asymptomatic carotid stenosis of 60% to 80%.

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