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Carotid sinus hypersensitivity (CSH) is an exaggerated response to carotid sinus baroreceptor stimulation. It is defined by the response to gentle carotid sinus massage applied just below the angle of the jaw, near the carotid bifurcation for between 5 and 10 seconds:
- At least three-second asystole (cardio-inhibition - the most common form; 70-75% of cases).
- Lowering of blood pressure by at least 50 mm Hg (vasodepression; 5-10% of cases) without slowing of the heart.
- A combination of cardio-inhibition and vasodepression (20-25% of cases).
Syncope may occur with or without accompanying bradycardia.
- Although baroreceptor function usually diminishes with age, some people experience hypersensitive carotid baroreflexes. CSH is rare before the age of 50.
- Carotid sinus hypersensitivity is the most commonly reported cause of falls and syncope in older people.The prevalence of CSH in elderly patients presenting with falls is estimated as being about 25%.
- However, it has been claimed that the current criteria for CSH are too sensitive and this in part explains the reported high prevalence of CSH in the general older population.
- Men are affected more often than women.
- Hypersensitivity occurs more often on the right carotid sinus than the left.
CSH is associated with:
- Coronary artery disease
- Other causes of syncope
- Dementia with Lewy bodies
- Medication - eg, digitalis, beta-blockers and methyldopa
- A careful history and thorough physical examination may point to an obvious diagnosis of CSH and no further investigation may be required.
- The assessment must be part of a thorough assessment of recurrent dizziness, syncope and falls.
- Typical trigger factors are shaving, head turning, neck extension or tight collars. Even mild stimulation to the neck may cause marked bradycardia and hypotension. The features of CSH may occasionally occur without any stimulation.
- Many patients remain asymptomatic.
- Signs during an attack will include hypotension, bradycardia or both.
- Auscultation for a carotid artery bruit prior to carotid sinus massage is essential in the evaluation of carotid artery occlusion.
- Postural hypotension.
- Other causes of syncope, including cough or micturition syncope, cardiac rhythm or structural abnormalities, epilepsy, myocardial ischaemia, pulmonary embolism, sick sinus syndrome, hypoglycaemia.
- The exclusion of other causes of syncope is mainly by a thorough history and examination.
- ECG can be used to rule out arrhythmias and indicate structural and functional heart disease. Ambulatory ECG monitoring may be required.
- Transthoracic echocardiogram can be used to rule out structural heart disease and problems of myocardial function.
- Event recording is indicated for the evaluation of patients with infrequent episodes of syncope or presyncope. Holter monitoring should be performed in patients who have no response to carotid sinus massage.
- Exercise treadmill testing: assess cardiac function, ischaemia and exertional cardiac arrhythmias.
- An EEG may also be indicated.
Carotid sinus massage
This should be undertaken with continuous ECG and blood pressure monitoring. Carotid sinus massage is potentially dangerous and may precipitate a stroke. It has also been reported to precipitate ventricular fibrillation. Therefore, full resuscitation facilities and expertise must be immediately available and this test is not appropriate in nearly all primary care settings.
Carotid sinus massage is contra-indicated in patients with:
- Myocardial infarction.
- Transient ischaemic attack (TIA) or a cerebrovascular event in the previous three months.
- Carotid artery occlusion.
- History of ventricular tachycardia or ventricular fibrillation.
- A previous adverse reaction to carotid sinus massage.
Both carotids should be confirmed as pulsatile in advance. Auscultation of the carotid arteries is also essential before the test can be considered. A carotid bruit is a relative contra-indication and a carotid ultrasound must be performed to further evaluate any patient who is found to have a carotid bruit.
The following protocol is taken from the European Society of Cardiology's Guidelines for the Management of Syncope (2009):
- Carotid sinus massage may be performed only in the supine position or in both supine and upright positions. The diagnosis may be missed in one third of cases if massage is not performed in the upright position (usually on a tilt table).
- Following baseline measurements, the right carotid artery is massaged for between 5 and 10 seconds at the anterior margin of the sternocleidomastoid muscle, at the level of the cricoid cartilage. The ipsilateral temporal artery may be palpated during the procedure to ensure that the carotid is not being occluded.
- If there is no significant response in terms of blood pressure or pulse rate, after 1 or 2 seconds the procedure is repeated on the opposite side.
- If there is an asystolic response, the massage is usually repeated after an intravenous injection of atropine. This is to ensure that a vasodepressor component has not been concealed by the asystolic response.
- A massage is considered to be positive if there is:
- Asystole for longer than three seconds.
- Reduction in systolic blood pressure by 50 mm Hg or more, irrespective of heart rate slowing.
- An alternative method is to attempt to reproduce symptoms during carotid massage. Massage is performed for 10 seconds in both the supine and upright positions.
- Lifestyle modification:
- Avoid triggers that increase pressure on the carotid sinus. Loose clothing with open collars may be helpful.
- Maintain adequate fluid intake.
- Learn to be aware of warning symptoms.
- There has not been shown to be any consistent benefit of medical therapies (eg, vasopressors or salt-retaining medications) or the use of elastic support stockings. The selective serotonin reuptake inhibitors (SSRIs) sertraline and fluoxetine have been used in patients who were unresponsive to dual-chamber pacing. However, no medication has been shown to be effective.[6, 7]
- Cardiac pacing with a permanent cardiac pacemaker:
- The treatment of choice to prevent syncope in patients with cardioinhibitory CSH, although permanent pacing intervention has been found to have no effect on fall rates in older patients with CSH.
- Cardiac pacing has little or no effect on the vasodepressor type of CSH.
- Surgical denervation of the carotid sinus:
- May be considered in cases where CSH is unilateral as a result of a mass or tumour in or near the carotid sinus.
- Surgical denervation has been largely abandoned in favour of pacing and is only considered for severely debilitating disease not helped by other treatment methods.
- The most common and important complications are injuries related to falls and other accidents, such as motor vehicle accidents that occur during syncopal episodes.
- There is therefore a potential loss of confidence, and social isolation may occur.
- There is no increase in mortality rates in patients with CSH compared with the general population.
- Untreated symptomatic patients have a high syncope recurrence rate.
- Patients treated with a pacemaker may experience recurrence of syncope.
- Patients with CSH showing a reduction in blood pressure after an carotid sinus stimulation have a worse prognosis than those with a pure cardio-inhibitory response or a lack of vasodepressor response.
Further reading and references
; European Society of Cardiology (2009)
; Carotid sinus hypersensitivity in asymptomatic older persons: implications for diagnosis of syncope and falls. Arch Intern Med. 2006 Mar 13166(5):515-20.
; The history of diagnosing carotid sinus hypersensitivity: why are the current criteria too sensitive? Europace. 2011 Jan13(1):14-22. doi: 10.1093/europace/euq409. Epub 2010 Nov 17.
; Determinants of a positive response to carotid sinus massage and head-up tilt Eur J Intern Med. 2009 Nov20(7):709-11. Epub 2009 Aug 15.
; Evaluation of syncope. Am Fam Physician. 2011 Sep 1584(6):640-50.
; Randomized clinical trials of neurally mediated syncope. J Cardiovasc Electrophysiol. 2003 Sep14(9 Suppl):S64-9.
; The management of patients with carotid sinus syndrome: is pacing the answer? Clin Auton Res. 2004 Oct14 Suppl 1:80-6.
; Pacing in elderly recurrent fallers with carotid sinus hypersensitivity: a Heart. 2009 Mar95(5):405-9. Epub 2009 Jan 5.
; Interventions for preventing falls in older people living in the community. Cochrane Database Syst Rev. 2012 Sep 129:CD007146. doi: 10.1002/14651858.CD007146.pub3.
; Mortality in carotid sinus hypersensitivity: a cohort study. BMJ Open. 2011 Jul 201(1):e000020. doi: 10.1136/bmjopen-2010-000020.
; Recurrent syncope in patients with carotid sinus hypersensitivity. ISRN Cardiol. 20122012:216206. Epub 2012 Sep 10.
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