The carotid arteries are two large blood vessels in the neck that supply oxygen-rich blood directly to the brain. Maintaining unimpeded blood flow is fundamental for preventing neurological events. The carotid plaque ultrasound, also known as a carotid duplex scan, is a non-invasive diagnostic tool used to assess the health of these arteries. This procedure uses high-frequency sound waves to visualize the vessels and measure the speed of blood flow.
Understanding Carotid Plaque
Carotid plaque is a buildup of fatty deposits, cholesterol, and calcium along the inner lining of the artery walls. This process is called atherosclerosis, which involves the hardening and narrowing of the arteries. This accumulation compromises the space available for blood flow to the brain.
The danger posed by this plaque is twofold: stenosis and embolism. Stenosis is the narrowing of the artery, which reduces the volume of blood reaching the brain. Embolism occurs when a fragment of plaque breaks away from the artery wall.
These loose fragments can travel downstream and lodge in smaller vessels within the brain, leading to a temporary blockage known as a transient ischemic attack (TIA) or a full stroke. Identifying the presence and characteristics of this plaque provides crucial information for assessing a person’s risk of a future stroke.
How the Ultrasound Procedure Works
The carotid ultrasound typically takes between 20 to 30 minutes to complete. The patient lies down, and a sonographer applies a water-based gel to the neck over the carotid arteries to help conduct sound waves. The sonographer uses a small, handheld transducer, gently pressing it against the skin and moving it along the neck.
The transducer emits high-frequency sound waves that bounce off internal structures, including the artery walls and moving blood cells. These returning echoes are processed by a computer to create real-time images on a monitor.
A specialized component, known as Doppler ultrasound, measures the speed and direction of blood flow through the vessels. The Doppler technique translates the movement of blood cells into a measurable signal, sometimes heard as a “whooshing” sound, which helps quantify the degree of blockage. The combination of structural images and flow data provides a complete picture of the artery’s condition.
Interpreting Plaque Severity and Characteristics
The results of a carotid ultrasound are interpreted based on two factors: the degree of stenosis and the physical characteristics of the plaque. Stenosis is quantified as a percentage, representing how much the artery lumen is narrowed by the plaque buildup. Mild stenosis is less than 50% narrowing, moderate is between 50% and 69%, and severe stenosis is 70% or greater.
While the percentage of narrowing is important, the composition of the plaque is recognized as a stronger predictor of stroke risk. Plaque is categorized as either stable or vulnerable. Stable plaque is typically smooth, calcified, and less likely to rupture, posing a lower risk of causing an embolism. Vulnerable plaque is unstable and dangerous, even if it causes a lower percentage of stenosis.
Vulnerable Plaque Characteristics
Features of vulnerable plaque include a large lipid-rich necrotic core, a thin or irregular fibrous cap covering the core, and the presence of intraplaque hemorrhage (bleeding within the plaque itself). These characteristics make the plaque surface more fragile and prone to cracking, which can trigger a blood clot and subsequent stroke.
The sonographer identifies these vulnerable features by noting the plaque’s echogenicity, or brightness, on the ultrasound image. Soft, lipid-rich plaques appear darker (hypoechoic) and are associated with a higher risk. Therefore, a patient with 40% vulnerable plaque may be considered at a higher risk for stroke than a patient with 60% stable, calcified plaque.
Management Options Following Diagnosis
The treatment plan following a carotid plaque diagnosis is tailored to the severity of the stenosis and the vulnerability of the plaque identified. For mild cases or those with no significant narrowing, the focus is on aggressive risk factor modification. These lifestyle changes include adopting a heart-healthy diet, incorporating regular physical activity, and achieving complete smoking cessation, as tobacco use accelerates plaque formation.
Medical management is prescribed for moderate cases and all high-risk plaque, regardless of stenosis percentage. This involves the use of statins to lower cholesterol, which helps stabilize plaque by reducing its lipid content and increasing its density. Antiplatelet medications, such as aspirin, are also commonly prescribed to reduce the risk of clot formation on the plaque surface.
For severe stenosis (70% to 99% narrowing) or for symptomatic patients who have experienced a TIA or minor stroke, surgical intervention may be recommended. The two primary procedures are Carotid Endarterectomy (CEA) and carotid artery stenting. CEA is an open surgical procedure where the plaque is physically removed to restore normal blood flow. Carotid stenting is a less invasive option where a mesh tube is placed inside the artery to keep the vessel open.