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A carotid bruit is a noise caused by turbulent blood flow in the carotid artery. It has been found to be a very good indication of carotid artery stenosis.
It is best heard via a stethoscope placed over the carotid bifurcation (at the upper border of the thyroid cartilage) but the sound may also radiate to the orbits, supraclavicular area and neck. Bruits are more common with increasing stenosis and maximal at 70-90% stenosis. They are more likely to be severe if patients have ipsilateral bruit, diabetes or a previous transient ischaemic attack (TIA).
Information about the incidence of carotid bruit in asymptomatic patients is available from the Framingham study. This found that 3.5% of men and women had carotid bruits at 44-54 years. This increased to 7.0% at 65-79 years.
The presenting symptoms of carotid artery disease include:
- Numbness or altered sensation in the arm.
- Dysarthria or dysphasia.
- Unilateral blindness (amaurosis fugax).
These symptoms may be intermittent, may occur in the form of a TIA or may be the more permanent sequelae of a stroke.
Normally, carotid artery bruit is found coincidentally. It may be part of the examination of patients presenting with suspected carotid artery disease or cerebrovascular disease or preoperatively before cardiac surgery. Occasionally, the noise is noticed by patients and presents as pulsatile tinnitus.
The most important determination is to differentiate a true carotid bruit suggestive of stenosis from other noises heard in the neck. These can be caused by:
- A murmur radiating from a stenosed aortic valve.
- External carotid artery disease.
- Intraluminal turbulence in the internal carotid artery.
- Arteriovenous malformations.
- External compression from thoracic outlet syndrome.
- Scarring due to neck surgery.
On detecting a carotid bruit, the clinician is duty bound to investigate further, as a proportion of patients will have significant stenosis, even if they are asymptomatic.
Depending on the clinical context, standard assessment of cardiovascular risk factors should also be arranged.
There are no internationally agreed guidelines, but the consensus view of specialists is that less invasive imaging procedures should be tried first as these are less likely to precipitate a stroke. The whole purpose of investigating patients with carotid bruits is to identify those who require carotid endarterectomy. Poorly designed trials have led to controversies over which method is most cost-effective.
The following types of carotid imaging can be used:
- Duplex ultrasound: This non-invasive test combines ultrasound and Doppler techniques and is the first-line investigation in most cases. It is relatively specific and sensitive for carotid artery stenoses of 50% or more. One study showed that progression of carotid artery stenosis over a six- to nine-month period indicated midterm clinical adverse events of atherosclerosis in high-risk patients, affecting the coronary, cerebrovascular and peripheral circulations.
- Magnetic resonance imaging: This can give additional information about plaque formation within the lumen of the carotid artery, and this can be made more effective by the addition of contrast.
- Digital subtraction angiography: This is angiography using digitally-enhanced images. It is less cost-effective than a combination of the other two methods, but is occasionally employed in complex cases. There is a risk of neurological deficit after this investigation but improving techniques have reduced the likelihood of this complication. One study found an incidence of permanent deficit of 0.09% and of temporary deficit of 0.45%.
- Cerebrovascular event.
- Cerebrovascular disease.
- Peripheral vascular disease.
- Coronary artery disease and conditions predisposing to it, eg diabetes, hyperlipidaemia, metabolic syndrome.
Asymptomatic patients with carotid bruits who have no significant carotid artery disease require no further treatment.
Aggressive control of cardiac and cerebrovascular risk factors is important in all patients with radiologically confirmed carotid artery stenosis, whether about to undergo surgery or not. This includes antiplatelet agents, lipid-lowering drugs and control of comorbidities such as diabetes and hypertension.
- 60% lumen stenosis is usually the cut-off point for selecting patients for endarterectomy.
- Carotid endarterectomy involves removing the thickened lining of the proximal part of the internal carotid artery (which carries blood to the eye and brain).
- Carotid endarterectomy can prevent stroke but this benefit has to be balanced against the risk of stroke as a consequence of surgery.
- In recent years, angioplasty and stenting have provided competitive alternatives to classical endarterectomy. Endarterectomy has been found to be superior in patients fit to undergo it for short- to medium-term outcomes. Endovascular options have significantly higher rates of re-stenosis.
- A study of the cost-effectiveness of carotid endarterectomy in addition to medical management concluded that such a strategy was to be recommended in men under the age of 73 but was less likely to be beneficial in older men or in women of any age.
- The association between asymptomatic carotid bruit and the risk of new vascular events was investigated by the SMART study (= S econd M anifestations of ART erial disease study). This involved 2,684 consecutive patients with clinical manifestations of arterial disease or type 2 diabetes mellitus, but without a history of cerebral ischaemia. In such patients, asymptomatic carotid artery stenosis was found to be an independent predictor of vascular events, especially vascular death.
- For asymptomatic patients, elective endarterectomy performed by skilled surgeons is safe in otherwise healthy patients regardless of age, reducing 5-year stroke rate to 6.4% compared with 11.8% in the control group. On the other hand, waiting for TIA or minor stroke to occur increases the complication rate of surgery to 6%.
- Symptomatic carotid stenosis increases steeply with age but, despite good evidence of major benefit from endarterectomy in elderly patients, there is substantial under-investigation of patients aged over 80 with TIA or ischaemic stroke.
- Elderly people benefit from carotid endarterectomy with little evidence of increased risk from surgery.
- Patients with stenting have been found to have a higher mortality rate post-procedure than endarterectomy patients, though this is felt to reflect the higher risk profile of these patients.
Auscultating for carotid artery bruit during routine examination is worthwhile, but has a low specificity that requires the support of ultrasound investigation.
Due to the relatively low prevalence of carotid artery disease in the community, a national screening programme is not cost-effective.
Further reading & references
- Paraskevas KI, Hamilton G, Mikhailidis DP; Clinical significance of carotid bruits: an innocent finding or a useful warning sign? Neurol Res. 2008 Jun;30(5):523-30.
- Gillett M, Davis WA, Jackson D, et al; Prospective evaluation of carotid bruit as a predictor of first stroke in type 2 diabetes: the Fremantle Diabetes Study.; Stroke. 2003 Sep;34(9):2145-51. Epub 2003 Aug 7.
- Daneshi A, Hadizadeh H, Mahmoudian S, et al; Pulsatile tinnitus and carotid artery atherosclerosis.; Int Tinnitus J. 2004;10(2):161-4.
- Louridas G, Junaid A; Management of carotid artery stenosis. Update for family physicians.; Can Fam Physician. 2005 Jul;51:984-9.
- Insider Medicine, Archives, May 2008
- Rothwell PM, Pendlebury ST, Wardlaw J, et al; Critical appraisal of the design and reporting of studies of imaging and measurement of carotid stenosis.; Stroke. 2000 Jun;31(6):1444-50.
- Huston J 3rd, James EM, Brown RD Jr, et al; Redefined duplex ultrasonographic criteria for diagnosis of carotid artery stenosis.; Mayo Clin Proc. 2000 Nov;75(11):1133-40.
- Sabeti S, Schlager O, Exner M, et al; Progression of carotid stenosis detected by duplex ultrasonography predicts adverse outcomes in cardiovascular high-risk patients. Stroke. 2007 Nov;38(11):2887-94. Epub 2007 Sep 20.
- Saam T, Cai J, Ma L, et al; Comparison of symptomatic and asymptomatic atherosclerotic carotid plaque features with in vivo MR imaging.; Radiology. 2006 Aug;240(2):464-72.
- Phan BA, Chu B, Kerwin WS, et al; Effect of contrast enhancement on the measurement of carotid arterial lumen and wall volume using MRI.; J Magn Reson Imaging. 2006 Apr;23(4):481-5.
- U-King-Im JM, Hollingworth W, Trivedi RA, et al; Cost-effectiveness of diagnostic strategies prior to carotid endarterectomy.; Ann Neurol. 2005 Oct;58(4):506-15.
- Grzyska U, Freitag J, Zeumer H; Selective cerebral intraarterial DSA. Complication rate and control of risk factors.; Neuroradiology. 1990;32(4):296-9.
- Sleight SP, Poloniecki J, Halliday AW; Asymptomatic carotid stenosis in patients on medical treatment alone.; Eur J Vasc Endovasc Surg. 2002 Jun;23(6):519-23.
- Toole JF; Surgery for carotid artery stenosis.; BMJ. 2004 Sep 18;329(7467):635-6.
- Johansson EP, Wester P; Carotid bruits as predictor for carotid stenoses detected by ultrasonography: an observational study. BMC Neurol. 2008 Jun 24;8:23.
- Meier P, Knapp G, Tamhane U, et al; Short term and intermediate term comparison of endarterectomy versus stenting for BMJ. 2010 Feb 12;340:c467. doi: 10.1136/bmj.c467.
- Ederle J, Bonati LH, Dobson J, et al; Endovascular treatment with angioplasty or stenting versus endarterectomy in Lancet Neurol. 2009 Oct;8(10):898-907. Epub 2009 Aug 28.
- Henriksson M, Lundgren F, Carlsson P; Cost-effectiveness of endarterectomy in patients with asymptomatic carotid artery stenosis. Br J Surg. 2008 Jun;95(6):714-20.
- Goessens BM, Visseren FL, Kappelle LJ, et al; Asymptomatic carotid artery stenosis and the risk of new vascular events in patients with manifest arterial disease: the SMART study. Stroke. 2007 May;38(5):1470-5. Epub 2007 Mar 15.
- Mohammed N, Anand SS; Prevention of disabling and fatal strokes by successful carotid endarterectomy in patients without recent neurological symptoms: randomized controlled trial. MRC asymptomatic carotid surgery trial (ACST) collaborative group. Lancet 2004; 363: 1491-502. Vasc Med. 2005 Feb;10(1):77-8.
- Fairhead JF, Rothwell PM; Underinvestigation and undertreatment of carotid disease in elderly patients with transient ischaemic attack and stroke: comparative population based study.; BMJ. 2006 Jul 18;.
- Wang FW, Esterbrooks D, Kuo YF, et al; Outcomes After Carotid Artery Stenting and Endarterectomy in the Medicare Stroke. 2011 May 26.
- Magyar MT, Nam EM, Csiba L, et al; Carotid artery auscultation--anachronism or useful screening procedure?; Neurol Res. 2002 Oct;24(7):705-8.
- No authors listed; Screening for carotid artery stenosis: U.S. Preventive Services Task Force recommendation statement. Ann Intern Med. 2007 Dec 18;147(12):854-9.
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|Original Author: Dr Laurence Knott||Current Version: Dr Hayley Willacy||Peer Reviewer: Dr Adrian Bonsall|
|Last Checked: 19/08/2011||Document ID: 674 Version: 22||© EMIS|