AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Background

Carotid sinus hypersensitivity (CSH) is an exaggerated response to carotid sinus baroreceptor stimulation. It results in dizziness or syncope from transient diminished cerebral perfusion.

Although baroreceptor function usually diminishes with age, some people experience hypersensitive carotid baroreflexes. For these individuals, even mild stimulation to the neck results in marked bradycardia and a drop in blood pressure.

CSH predominantly affects older males. It is a potent contributory factor and a potentially treatable cause of unexplained falls and neurocardiogenic syncopal episodes in elderly people. Yet, CSH is often overlooked in the differential diagnosis of syncope.

Pathophysiology

The carotid sinus reflex plays a central role in blood pressure homeostasis. Changes in stretch and transmural pressure are detected by baroreceptors in the heart, carotid sinus, aortic arch, and other large vessels. Afferent impulses are transmitted by the carotid sinus, glossopharyngeal, and vagus nerves to the nuclei tractus solitarius and the para median nucleus in the brain stem. Efferent limbs are carried through sympathetic and vagus nerves to the heart and blood vessels, controlling heart rate and vasomotor tone.

In CSH, mechanical deformation of the carotid sinus (located at the bifurcation of the common carotid artery) leads to an exaggerated response with bradycardia or vasodilatation, resulting in hypotension, presyncope, or syncope.

The exact mechanism and site of abnormal sensitivity is unknown. The exaggerated response may be due to changes in any part of the reflex arc or the target organs.

Three types of CSH have been described.

1. The cardioinhibitory type comprises 70-75% of cases. The predominant manifestation is a decreased heart rate, which results in sinus bradycardia, atrioventricular block, or asystole due to vagal action on sinus and atrioventricular nodes. This response can be abolished with atropine.
2. The vasodepressor type comprises 5-10% of cases. The predominant manifestation is a vasomotor tone decrease without a change in heart rate. The significant resulting drop in blood pressure is due to a change in the balance of parasympathetic and sympathetic effects on peripheral blood vessels. This response is not abolished with atropine.
3. The mixed type comprises 20-25% of cases. A decrease in heart rate and vasomotor tone occurs.

Recently, the terms spontaneous carotid sinus syndrome and induced carotid sinus syndrome have been introduced to categorize patients who are presumed to have CSH.

• The term spontaneous carotid sinus syndrome refers to a clinical situation in which the symptoms can be clearly attributed to a history of accidental mechanical manipulation of the carotid sinuses (eg, taking pulses in the neck, shaving) and CSH is reproduced by carotid sinus massage. Spontaneous carotid sinus syndrome is rare and accounts for about 1% of causes of syncope.
• The term induced carotid sinus syndrome refers to a clinical situation in which a patient has no clear history of accidental mechanical manipulation of the carotid sinuses and has a negative result from workup for syncope, except for a hypersensitive response to carotid sinus massage, which can be attributed to the patient's symptoms. Induced carotid sinus syndrome is more prevalent than spontaneous carotid sinus syndrome and accounts for the bulk of patients with an abnormal response to carotid sinus massage observed in the clinical setting.

Frequency

United States

CSH is found in 0.5-9.0% of patients with recurrent syncope.

International

CSH is observed in up to 14% of elderly nursing home patients and 30% of elderly patients with unexplained syncope and drop attacks.

Mortality/Morbidity

• CSH is associated with an increased risk of falls, drop attacks, bodily injuries, and fractures in elderly patients.
• Rates of total mortality, sudden death, myocardial infarction, or stroke are unaffected by the presence of CSH.

Sex

CSH is more common in males than in females.

Age

CSH is predominantly a disease of elderly people; it is virtually unknown in people younger than 50 years.

CLINICAL

Section 3 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

History

Although many patients remain asymptomatic, the following are symptoms of CSH:

• Recurrent dizziness, near-syncope
• Recurrent syncope
• Nonaccidental, unexplained falls
• Symptoms produced by head turning or wearing garments with tight-fitting collars
• Neck tumors, extensive neck scarring secondary to radical dissection or radiation fibrosis or neck trauma
• Possible prodrome or retrograde amnesia for the syncopal event

Physical

Signs of CSH found upon examination include the following:

• Hypotension
• Bradycardia
• Asystole
• Auscultation for carotid artery bruit prior to consideration of carotid sinus massage

Causes

CSH is associated with the following:

• Male sex
• Increasing age
• Hypertension
• Coronary artery disease
• Other causes of neurocardiogenic syncope
• Dementia with Lewy body disease
• Concurrent medication with digitalis, beta-blockers, and methyldopa

DIFFERENTIALS

Section 4 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Other Problems to be Considered

Vasovagal syncope
Orthostatic hypotension
Situational syncope (eg, associated with cough, deglutition, micturition, defecation)
Cardiogenic syncope

WORKUP

Section 5 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Lab Studies

• The initial diagnostic workup should rule out the following:
• • Vasovagal syncope
  • Orthostatic hypotension
  • Situational syncope
  • Sick sinus syndrome
  • Cardiogenic syncope
  • Other causes of syncope (eg, neurogenic, metabolic, psychogenic)
• Any patient with syncope should be evaluated with the following:
• • A carefully elicited history
  • A thorough physical examination
  • An ECG

Procedures

• Carotid sinus massage is the diagnostic maneuver of choice, but the technique has not been standardized.
• A commonly accepted massage method includes the following 4 steps:
  1. Place the patient in the supine position with the neck slightly extended. The patient should lie supine for a minimum of 5 minutes before carotid sinus massage is applied.
  2. Massage over the point of maximal carotid impulse, medial to the sternomastoid muscle at the upper border level of the thyroid cartilage.
  3. Massage for 5 seconds on both sides, with a 1-minute interval between massages.
  4. Continuously monitor surface ECG and blood pressure. Phasic, noninvasive, beat-to-beat blood pressure monitoring is preferred over using a cuff measurement.
• A massage is considered to have a positive result if any of the following 3 criteria are met:
  1. Asystole exceeding 3 seconds (indicates cardioinhibitory CSH)
  2. Reduction in systolic blood pressure exceeding 50 mm Hg independent of heart rate slowing (indicates vasodepressor CSH)
  3. Combination of the above (indicates mixed CSH)
• A less frequently used method consists of carotid sinus massage performed for 5 seconds on each side in the supine and 60° positions using the head-up tilt table. Substantial evidence shows that sensitivity and diagnostic accuracy of carotid sinus massage can be enhanced by performing the test with the patient in an upright position.
• Do not perform a carotid sinus massage if the patient is known to have transient ischemic attack, stroke, or myocardial infarction in the preceding 3 months. History of ventricular tachycardia, ventricular fibrillation, or carotid bruit on auscultation are relative contraindications to carotid sinus massage.
• Some authors describe the use of carotid Doppler ultrasonography to guide carotid sinus massage in patients who have a carotid bruit on auscultation. Carotid sinus massage is performed only in patients with a carotid bruit and less than 70% stenosis on Doppler examination.
• Although carotid sinus massage is usually a benign bedside procedure, a few case reports describe rare neurological deficit symptoms following the massage. Currently, the estimated incidence of neurological complications is less than 0.2%.
• A single case report describes the induction of coronary artery spasm by carotid sinus massage.
• Similarly, rare case reports describe the induction of atrial or ventricular arrhythmias by carotid sinus massage.
• Carotid massage has its greatest clinical utility in elderly patients aged 60-80 years.
• The positive predictive value of carotid massage remains undefined. Therefore, a clinician who finds a sensitive carotid sinus should consider other prognostically important causes of syncope and the presence of comorbid conditions.

TREATMENT

Section 6 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical Care

• Management is based on the frequency, severity, and consequences of each patient's symptoms.
• Most patients can be treated with education, lifestyle changes, expectancy, and routine follow-up.
• A few individuals who have incapacitating and recurrent symptoms may need the following treatments:
• • Pharmacotherapy has been used to treat recurrent, symptomatic conditions. However, no single agent has been proven to provide long-term effectiveness in large-scale, randomized, controlled trials.
  • Supported by 2 randomized trials, permanent pacemaker implantation is now considered an effective treatment for cardioinhibitory CSH and mixed forms of CSH.
    • Current American College of Cardiology/American Heart Association/Heart Rhythm Society clinical practice guidelines consider permanent pacing therapy to be a class I indication (ie, general agreement exists that the therapy is effective and useful) in patients with recurrent syncope caused by carotid sinus stimulation in the absence of any drug that depresses the sinus node or atrioventricular conduction. Permanent pacing is considered a class IIa indication in patients with recurrent syncope without clear, provocative events and with a hypersensitive cardioinhibitory response. Permanent pacing is discouraged in patients with a hypersensitive cardioinhibitory response to carotid sinus stimulation in the absence of symptoms.
    • The consensus is that dual chamber pacing (DDD, DVI, DDI) is optimal in the patients. However, VVI mode is also effective in preventing recurrent syncope in some patients. AAI and VDD modes are considered inappropriate.
    • Cardiac pacing has little or no effect on the vasodepressor type of CSH.
  • Volume maintenance can control the vasodepressor form of CSH, preventing syncopal episodes by maintaining adequate central volume. An individual without another cardiovascular disease should increase salt intake and drink more fluids containing electrolytes.

Surgical Care

• Surgical denervation and radiological denervation of the carotid sinus nerve were techniques used previously, but they have been largely abandoned because of high complication rates.
• Surgery remains an option for a patient with a neck tumor that is compressing the carotid sinus.

Consultations

• Consult a cardiologist to rule out cardiac arrhythmia and evaluate the patient for pacemaker implantation.
• Obtain a surgical consultation and evaluation if the patient has a neck tumor that is compressing the carotid sinus.

Activity

• No general activity restrictions are necessary.
• Precipitating events, such as wearing tight neck collars or sudden rotating neck movements, should be avoided.

MEDICATION

Section 7 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Although a variety of pharmacological agents has been used empirically to treat recurrent, symptomatic CSH, no single agent has been unequivocally proven to provide long-term effectiveness in large-scale, randomized controlled trials. Some observers have successfully used the serotonin reuptake inhibitors sertraline and fluoxetine in patients who were unresponsive to dual-chamber pacing.

More recently, a randomized, controlled pilot study showed that treatment with midodrine, an alpha-1 agonist, could significantly decrease the rate of symptoms and the degree of hypotension in the vasodepressor form of CSH. Treatment with midodrine was also associated with an elevation of a mean 24-hour ambulatory blood pressure level. Midodrine induces arterial and venous capacitance constriction and has minimal cerebral and cardiac effects. It is indicated for the treatment of symptomatic orthostatic hypotension.

The US Food and Drug Administration has not yet approved these agents for the management of CSH.

FOLLOW-UP

Section 8 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Further Outpatient Care

• Follow-up should be based on the severity of symptoms and the treatment modality.
• Patients on any form of treatment require regular follow-up to monitor the effects of treatment versus the adverse effects of intervention.
• Follow-up for patients who rarely have symptoms may be on an as-needed basis.

Prognosis

• The long-term mortality rate is similar to the general population and patients with unexplained syncope.
• Untreated symptomatic patients have a syncope recurrence rate as high as 62% within 4 years.
• Patients treated with a pacemaker have fewer syncopal attacks but may experience a recurrence rate as high as 16% in 4 years.

Patient Education

• Recognize premonitory symptoms
• Avoid triggering events
• Be aware of therapeutic actions such as methods to increase central fluid volume in the body
• For excellent patient education resources, visit eMedicine's Brain and Nervous System Center. Also, see eMedicine's patient education article Dizziness.

MISCELLANEOUS

Section 9 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical/Legal Pitfalls

• Performing carotid sinus massage on a patient with cerebrovascular disease or carotid bruit on auscultation may precipitate neurological manifestations.

Special Concerns

• Patients with severe symptoms attributed to CSH should be advised against driving vehicles until the condition is addressed by a physician.

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

• Benditt DG, Fahy GJ, Lurie KG, et al. Pharmacotherapy of neurally mediated syncope. Circulation. Sep 14 1999;100(11):1242-8. [Medline].
• Brignole M. Randomized clinical trials of neurally mediated syncope. J Cardiovasc Electrophysiol. Sep 2003;14(9 Suppl):S64-9. [Medline].
• Brignole M, Menozzi C, Lolli G, et al. Long-term outcome of paced and nonpaced patients with severe carotid sinus syndrome. Am J Cardiol. Apr 15 1992;69(12):1039-43. [Medline].
• Gregoratos G, Abrams J, Epstein AE, et al. ACC/AHA/NASPE 2002 Guideline Update for Implantation of Cardiac Pacemakers and Antiarrhythmia Devices--summary article: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (ACC/AHA/NASPE Committee t. J Am Coll Cardiol. Nov 6 2002;40(9):1703-19. [Medline].
• Kenny RA, Richardson DA, Steen N, et al. Carotid sinus syndrome: a modifiable risk factor for nonaccidental falls in older adults (SAFE PACE). J Am Coll Cardiol. Nov 1 2001;38(5):1491-6. [Medline].
• Kenny RA, O''Shea D, Parry SW. The Newcastle protocols for head-up tilt table testing in the diagnosis of vasovagal syncope, carotid sinus hypersensitivity, and related disorders. Heart. May 2000;83(5):564-9. [Medline].
• McIntosh SJ, Lawson J, Kenny RA. Clinical characteristics of vasodepressor, cardioinhibitory, and mixed carotid sinus syndrome in the elderly. Am J Med. Aug 1993;95(2):203-8. [Medline].
• Moore A, Watts M, Sheehy T, et al. Treatment of vasodepressor carotid sinus syndrome with midodrine: a randomized, controlled pilot study. J Am Geriatr Soc. Jan 2005;53(1):114-8. [Medline].
• Morillo CA, Camacho ME, Wood MA, et al. Diagnostic utility of mechanical, pharmacological and orthostatic stimulation of the carotid sinus in patients with unexplained syncope. J Am Coll Cardiol. Nov 1 1999;34(5):1587-94. [Medline].

Article Last Updated: Jun 23, 2005