A carotid ultrasound is a non-invasive, painless imaging procedure that uses high-frequency sound waves to visualize the blood vessels in the neck. The primary goal of this test is to assess the health of the carotid arteries, the main channels supplying oxygen-rich blood to the brain. By evaluating the structure and blood flow within these vessels, the ultrasound helps medical professionals determine a patient’s risk of stroke. This risk assessment focuses on detecting and quantifying any narrowing, or stenosis, caused by the buildup of fatty deposits known as plaque. Understanding the terms, measurements, and thresholds in your report is key to discussing the results with a healthcare provider.
Key Anatomical Terms
The carotid system begins with the Common Carotid Artery (CCA), which travels up the neck before dividing into two main branches: the Internal Carotid Artery (ICA) and the External Carotid Artery (ECA). This division point is often where atherosclerotic disease begins to develop.
The ICA supplies blood directly to the brain, making blockages here the most concerning for stroke risk. The ECA supplies blood to the face, neck, and scalp, and disease in this vessel is generally less significant for brain health. The term “lumen” refers to the interior, open channel of the blood vessel where blood flows.
The central finding in many reports is “plaque,” a deposit composed of cholesterol, fat, calcium, and other substances that accumulate on the artery walls. Plaque buildup causes the vessel to narrow and harden, a process called atherosclerosis.
Interpreting the Degree of Stenosis
The most frequently cited measurement is the degree of stenosis, which quantifies the percentage of the artery that is blocked. This percentage is calculated by comparing the narrowest diameter at the blockage site to the diameter just beyond it. This approach standardizes the measurement and provides a consistent basis for clinical decision-making.
Stenosis is typically categorized into three main clinical thresholds:
Mild Stenosis
Mild stenosis is defined as narrowing less than 50% (0% to 49%) of the vessel’s diameter. For this range, monitoring and intensive medical management are the usual recommendations, as the immediate risk of stroke is relatively low.
Moderate Stenosis
Moderate stenosis falls within the 50% to 69% range, representing a significant increase in stroke risk. Patients generally require more aggressive medical therapy, including antiplatelet medications and cholesterol-lowering drugs like statins.
Severe Stenosis
Severe stenosis is the most concerning category, representing a blockage of 70% to 99% of the artery’s diameter. At this level, the risk of a stroke is substantially elevated, and interventional treatment options are often considered. A 100% blockage is termed an occlusion, meaning no blood is flowing through that vessel.
Understanding Flow Velocity and Plaque Features
Beyond the visual percentage of narrowing, flow dynamics provide a secondary, often more reliable, measurement of disease severity. Doppler technology measures the speed of blood flow, which naturally increases as blood is forced through a narrowed section of the artery. These velocity measurements are crucial for a complete picture of the blockage.
Two common velocity metrics are the Peak Systolic Velocity (PSV) and the End Diastolic Velocity (EDV). The PSV measures the maximum speed of blood flow during the heart’s contraction phase (systole). The EDV measures the flow speed during the heart’s relaxation phase (diastole). A PSV exceeding 230 cm/second, for instance, often indicates the artery is narrowed by 70% or more.
The characteristics of the plaque itself, known as plaque morphology, also influence the risk of stroke. Plaque described as irregular or ulcerated (having a rough surface) is considered less stable and more likely to rupture, releasing clots. In contrast, smooth and heavily calcified plaque is generally viewed as more stable.
Clinical Grading and Follow-Up Actions
A physician combines the anatomical measurement of stenosis percentage with hemodynamic flow velocity data to assign a final clinical grade. This comprehensive grade guides the management strategy, moving from simple monitoring to aggressive intervention, and represents a tailored risk profile for the patient.
For patients with mild disease (under 50% stenosis), follow-up focuses on intensive management of risk factors like high blood pressure, cholesterol, and diabetes, often involving lifestyle modifications. Medication, such as aspirin therapy and statins, is commonly initiated to stabilize existing plaque and prevent its growth. Regular surveillance ultrasounds, often every six to twelve months, monitor for disease progression.
When stenosis reaches the moderate to severe range (50% or higher), the discussion shifts toward potential surgical or procedural interventions. For severe blockages (70% or greater), a physician may recommend a Carotid Endarterectomy (surgery to remove plaque) or Carotid Artery Stenting (a procedure to open the vessel with a small mesh tube). The decision to intervene is complex and weighed against the patient’s overall health and procedural risk.