Which patients should undergo a carotid ultrasound, particularly those with a history of smoking, high blood pressure (hypertension), high cholesterol (hyperlipidemia), transient ischemic attacks (TIAs), strokes, cardiovascular disease, diabetes, or peripheral artery disease?

Who Should Have a Carotid Ultrasound?

Routine screening of asymptomatic adults for carotid stenosis is not recommended, as the harms of screening and subsequent intervention outweigh the benefits in the general population. 1

Patients Who Should Undergo Carotid Ultrasound

Symptomatic Patients (Strongest Indication)

• Patients with transient ischemic attacks (TIAs) or stroke symptoms in the carotid territory should be evaluated promptly with duplex ultrasonography for consideration of carotid endarterectomy. 1, 2
• Individuals who develop focal neurological symptoms corresponding to the territory supplied by the left or right internal carotid artery require immediate evaluation. 2
• Patients with transient retinal symptoms (such as amaurosis fugax) of possible ischemic origin should undergo non-invasive imaging for carotid stenosis. 2

Asymptomatic Patients with Specific Findings

• It is reasonable to perform duplex ultrasonography in asymptomatic patients with a carotid bruit detected on physical examination. 1
• Patients with known carotid stenosis greater than 50% should undergo annual duplex ultrasonography to assess disease progression or regression and response to medical therapy. 1

Selected High-Risk Asymptomatic Patients (Controversial)

• Duplex ultrasonography might be considered in asymptomatic patients with two or more of the following risk factors: hypertension, hyperlipidemia, tobacco smoking, family history of atherosclerosis in a first-degree relative before age 60, or family history of ischemic stroke. 1, 2
• Screening may be considered in asymptomatic patients with symptomatic peripheral artery disease, coronary artery disease, or atherosclerotic aortic aneurysm, though it remains unclear whether establishing the diagnosis of carotid stenosis would justify actions that affect clinical outcomes. 1

Patients Who Should NOT Undergo Carotid Ultrasound

• Carotid duplex ultrasonography is not recommended for routine screening of asymptomatic patients who have no clinical manifestations of or risk factors for atherosclerosis. 1
• Screening is not recommended for patients with neurological or psychiatric disorders unrelated to focal cerebral ischemia, such as brain tumors, degenerative disorders, infections, or epilepsy. 1
• Routine serial imaging is not recommended for patients who have no risk factors for atherosclerotic carotid disease and no disease evident on initial testing. 1

Understanding the Evidence and Controversy

Why Routine Screening Is Not Recommended

The U.S. Preventive Services Task Force (USPSTF) concluded that for asymptomatic individuals, the benefits of screening do not outweigh the harms. 1 The number needed to screen to prevent one stroke is approximately 4,348 people, and 8,696 people would need to be screened to prevent one disabling stroke. 1

Key harms include:

• Carotid endarterectomy carries a 30-day stroke or mortality rate of approximately 3% even in excellent centers, with higher rates in some areas. 1, 2
• False-positive screening results lead to unnecessary confirmatory testing with digital subtraction angiography, which itself can cause strokes. 1
• Duplex ultrasonography has imperfect sensitivity (86-90%) and specificity (87-94%) for detecting stenosis greater than 70%. 1

Divergence in Guidelines

While the USPSTF recommends against routine screening, other societies have more liberal recommendations. 1 The Society for Vascular Surgery (2007) recommended screening for individuals age 55 years or older with cardiovascular risk factors such as hypertension, diabetes, smoking, hypercholesterolemia, or known cardiovascular disease. 1 The American Society of Neuroimaging (2007) recommended screening adults age 65 years or older with 3 or more cardiovascular risk factors. 1

However, the most recent and authoritative guideline from the American College of Cardiology/American Heart Association (2011) takes a more conservative approach, emphasizing that it is unclear whether establishing a diagnosis of carotid stenosis in asymptomatic patients would justify actions that affect clinical outcomes. 1

Risk Factors for Carotid Stenosis

Major risk factors include: 1, 2

• Older age (especially >65 years)
• Male sex
• Hypertension
• Smoking
• Hypercholesterolemia/dyslipidemia
• Heart disease
• Diabetes mellitus

Critical Clinical Pitfalls

• Do not confuse the presence of a carotid bruit with significant stenosis—a bruit correlates more closely with systemic atherosclerosis than with significant carotid stenosis. 1
• Focus clinical efforts on optimizing medical management of stroke risk factors (hypertension, hyperlipidemia, smoking cessation, antiplatelet therapy) rather than screening for asymptomatic carotid stenosis. 1
• The benefits of carotid endarterectomy in randomized trials were demonstrated in highly selected patients with excellent surgical centers; real-world outcomes may be worse. 1
• Modern medical therapy (intensive blood pressure and lipid control) was not standard in older trials showing benefit from carotid endarterectomy, making the incremental benefit of surgery over current medical therapy uncertain. 1