The carotid arteries are large blood vessels on each side of the neck that transport oxygen-rich blood from the heart directly to the brain and other parts of the head. They begin as the common carotid artery, which branches into the internal carotid artery (supplying the brain) and the external carotid artery (supplying the face and scalp). Because of their role in cerebral blood supply, the health of the carotid arteries is monitored during physical examinations. A routine part of this examination is auscultation, or listening, over these vessels with a stethoscope.
What is a Carotid Bruit and Its Significance
A carotid bruit (pronounced “broo-ee”) is an abnormal vascular sound, often described as a whooshing noise, heard over the carotid artery. This sound is caused by turbulent blood flow, where blood moves in a disorganized manner instead of smoothly.
The primary cause is typically atherosclerosis, the buildup of plaque on the artery walls. This leads to carotid artery stenosis, a narrowing of the vessel’s internal diameter. When the artery is significantly narrowed, blood passing through the constriction creates the vibrations heard as a bruit.
The discovery of a carotid bruit indicates underlying arterial disease, usually atherosclerosis. This narrowing can impede blood flow to the brain and increases the risk of a stroke or transient ischemic attack (TIA). Plaque can also rupture, leading to blood clots that may travel to the brain and block smaller vessels.
A bruit is an auscultatory sign, not a definitive diagnosis of severe narrowing. While it suggests the need for further evaluation, some patients with severe stenosis may have no audible bruit. Therefore, the presence of a bruit functions as a screening tool that prompts further assessment.
Preparation for the Assessment
Before auscultating the carotid arteries, the environment and patient must be prepared. The examination room should be quiet, as the sounds are often subtle and low-frequency. The patient should sit comfortably upright with their head facing forward and neck relaxed.
Since carotid bruits are low-frequency sounds, the bell of the stethoscope is the preferred component for this assessment, as it picks up lower-pitched sounds more effectively than the diaphragm. The stethoscope must be placed directly on the skin without clothing interference.
The patient must be instructed on breath-holding. They will be asked to inhale and briefly hold their breath while the examiner listens. This prevents breathing sounds from obscuring a faint bruit. The patient should also avoid talking or moving during the few seconds of listening.
The Auscultation Technique
The assessment begins with a gentle palpation of the carotid pulse in the lower neck to locate the artery and assess the pulse rhythm. This must be performed carefully to avoid compressing the vessel, which could slow the heart rate. Auscultation is performed on one side at a time, comparing findings between the right and left arteries.
The stethoscope’s bell is placed lightly over the artery at three specific locations on each side of the neck:
- The base of the neck, near the clavicle, to listen for sounds radiating up from the chest.
- The mid-cervical area, over the carotid bifurcation, which is the most common site for plaque buildup.
- High in the neck, near the angle of the jaw, the optimal location for detecting bruits from the internal carotid artery.
The examiner must apply only light pressure with the bell to maintain a proper skin seal. Compression must be avoided as it can distort the sound or cause a temporary drop in heart rate.
Interpreting the Findings and Follow-Up
The presence of a bruit suggests that turbulent blood flow is occurring and may indicate carotid artery stenosis. The sound is often heard during systole (the phase when the heart is contracting). A bruit that extends throughout systole and into diastole (the resting phase) is a stronger indicator of severe narrowing, typically 70% to 85%. Conversely, the absence of a bruit does not completely exclude disease, as a very high-grade stenosis (over 85%) or a complete blockage may not produce an audible sound.
If a bruit is detected during the physical exam, the standard next step is to obtain a detailed, non-invasive image of the arteries. A carotid duplex ultrasound is the most common follow-up test. It uses sound waves to visualize the artery structure and measure the speed and pattern of blood flow, accurately determining the degree of stenosis within the vessel.
The ultrasound results guide the subsequent management and follow-up plan. For mild to moderate stenosis, treatment involves medical management, including antiplatelet medications to prevent clotting and statins to lower cholesterol. Patients with significant narrowing (70% or greater) may be evaluated for surgical intervention. Options include a carotid endarterectomy to remove the plaque or carotid stenting to open the artery. Routine follow-up ultrasounds are recommended every six to twelve months for patients with known, non-severe stenosis.