A bruit is caused by turbulent blood flow in an artery which supplies blood to the brain. Increased stenosis of a carotid artery results in increased duration, intensity, and pitch of the bruit.
A carotid bruit and a basal heart murmur are easily confused. Because the sounds radiate throughout the body, a heart murmur will be heard, with reduced intensity, at the auscultation points above the clavicle and a carotid bruit will be heard (again with reduced intensity) at the auscultation points below the clavicle. If the intensity of sound is greater above the clavicle it is most likely a carotid bruit. If it is louder below the clavicle it is most likely a heart murmur.
An early systolic bruit is associated with a 50% decrease in carotid artery luminal diameter. A pansystolic bruit is associated with a 60% reduction in luminal diameter. A pansystolic bruit that extends into early diastole is associated with a decrease in luminal diameter of 70% to 80%.
The identification of a carotid artery bruit using a stethoscope should always be followed up with an ultrasound examination of both carotid vessels due to the limited accuracy of an examination with a stethoscope.
Use either the bell or the diaphragm when listening for the carotid bruit, at a point just lateral to the Adam's apple. Listen for the murmur of aortic stenosis at the second right intercostal space (2RICS).
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