Carotid Bruit

Carotid Bruit: Excerpt from Field Guide to Bedside Diagnosis

Differential Overview

❑ Carotid artery stenosis

❑ Carotid artery ruptured plaque

❑ Transmitted valvular murmur

❑ Carotid tortuosity

❑ Carotid compression

❑ Jugular venous hum

❑ Thyrotoxicosis

Diagnostic Approach

Carotid bruits are imperfect markers of increased stroke risk because stroke is usually not due to progressive carotid stenosis, but rather to ruptured plaque, cardiac emboli from atrial fibrillation, emboli from aortic sources, or watershed ischemia due to decreased flow. A bruit is, however, an important marker of generalized atherosclerosis. The annual incidence of stroke in the territory of a carotid bruit is 1.7%/year and increases to 5.5%/year as stenosis exceeds 75%. The risk of death (usually cardiac) in a patient with a carotid bruit is 4%/yr. Bruits are clinically significant when associated with transient ipsilateral anterior circulation symptoms such as amaurosis fugax (transient monocular blindness), contralateral homonymous hemianopsia, hemiparesis, and hemisensory defect. Left hemispheric lesions are associated with aphasia, and right with visuospatial neglect and constructional apraxia.

Clinical Findings

Carotid artery stenosis  Bruits occur when laminar flow becomes turbulent at high flow rates. A rule of thumb is that at 50% reduction in diameter (70% cross-sectional area), a soft bruit may be heard. At 60% reduction, the bruit becomes high-pitched, intense, and holosystolic. At 80%, a systolic–diastolic bruit is heard. At near occlusion, the bruit disappears as does the pulse. As stenosis of the ICA becomes critical, flow decreases, decreasing the bruit, and ECA flow is augmented, as detected in the angular pulses.

Carotid artery ruptured plaque  Plaque rupture produces a bruit associated with a sudden shower of anterior circulation ischemic symptoms (unstable TIAs or amaurosis fugax). The carotid pulse is usually normal.

Transmitted valvular murmur  Aortic stenosis produces a murmur that can be heard equally at the upper right sternal border and both carotids, and has the same sound at both locations. A murmur produced by mitral regurgitation from a ruptured chordae tendineae or mitral valve prolapse may also radiate to the neck.

Carotid tortuosity  In an elderly patient, the carotid may become palpably tortuous with prominent pulsations in addition to a bruit.

Carotid compression  Creation of a carotid bruit by stethoscope compression can be “cured” by reducing the pressure of the stethoscope.

Jugular venous hum  A hum occurs most prominently in adults with high cardiac output states and can be confirmed by disappearance with compression of the internal jugular vein.

Thyrotoxicosis  A systolic bruit, which is produced by enhanced flow, can be heard directly over an enlarged thyroid.

Pictures

Book Source Details

• Book Title: Field Guide to Bedside Diagnosis
• Author(s): David S. Smith
• Year of Publication: 2007
• Copyright Details: Field Guide to Bedside Diagnosis, Copyright © 2007 Lippincott Williams & Wilkins.

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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.

More About This Book: Title: Field Guide to Bedside Diagnosis Authors: David S. Smith Publisher: Lippincott Williams & Wilkins Copyright: 2007 ISBN: 0-78178-165-5

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