- Baroreceptors in the carotid sinus and aortic arch normally influence blood pressure (BP) and heart rate. An endogenous increase in BP or external pressure on the carotid sinus increases the baroreceptor firing rate and activates vagal efferents, resulting in a bradycardia and/or drop in BP.
- In carotid sinus syndrome, stimulation of 1 or both hypersensitive carotid sinuses may produce brief episodes of faintness or loss of consciousness.
- Carotid sinus syndrome is defined as an asystole of ≥3 seconds and/or a drop in systolic BP of ≥50 mm Hg elicited by cardiac sinus pressure.
- 4 types are described:
- Cardioinhibitory: Vagally mediated, causing bradycardia, sinus arrest, or atrioventricular block for >3 seconds
- Vasodepressor: A sudden drop of peripheral vascular resistance leads to a >50 mm Hg decrease in systolic BP without change in heart rate, or to a >30 mm Hg symptomatic drop in systolic BP.
- Mixed: Combined cardioinhibitory and vasodepressor changes
- Cerebral: Extremely rare; carotid sinus hypersensitivity occurs without bradycardia or hypotension.
- System(s) affected: Cardiovascular; Nervous
- Synonym(s): Carotid sinus syncope; Carotid sinus hypersensitivity
- Predominant age: Elderly
- Predominant sex: Male > Female (2:1)
- More likely to occur in elderly
- Can be a cause of unexplained frequent falls
- 35 million cases are reported every year.
- Incidence increases with age
- In 2 large studies of patients with syncope, 6–14% had carotid sinus hypersensitivity.
- In patients >80 years of age with unexplained syncope, prevalence of carotid sinus syndrome may be as high as 40%.
- Diffuse atherosclerosis
- Carotid body tumors
- Inflammatory and malignant lymph nodes in the neck
- Metastatic cancer
Commonly Associated Conditions
- Sick sinus syndrome
- Atrioventricular block
- Coronary artery disease
- Unexplained falls
- Abnormal gait and balance
- Absence of postictal symptoms
- Abnormal visual acuity
- Orthostatic vital signs (exclude orthostatic hypotension)
Diagnostic Tests & Interpretation
Carotid duplex scan
- Special test: Unilateral carotid sinus pressure “massage” for 5–10 seconds:
- With the patient in the supine position and while the BP and ECG are monitored, manual pressure on the carotid sinus causes asystole or reproduces the symptoms (commonly but somewhat erroneously termed “massage”)
- Diagnostic yield may be increased by combining with tilt-table testing.
- Contraindications to this test include:
- Carotid bruit
- History of stroke or transient ischemic attack
- Recent myocardial infarction
- History of ventricular tachycardia or fibrillation
- The test can be falsely positive in elderly patients.
Pressure on the carotid sinus causes asystole of >3 seconds (cardioinhibitory) and/or a drop in systolic BP ≥50 mm Hg.
- Neurocardiogenic syncope
- Postural hypotension
- Primary autonomic insufficiency
- Sick sinus syndrome
- Cerebrovascular insufficiency
- Other causes of syncope
- Anticholinergics: Atropine (acutely) for cardioinhibitory type
- α-Sympathomimetics: Ephedrine, midodrine
- Precautions: Concomitant usage of digitalis, β-blockers, clonidine, and α-methyldopa may accentuate response to carotid sinus massage.
Fludrocortisone can be used to improve orthostatic symptoms in patients with vasodepressor response.
- No treatment is required for asymptomatic individuals.
- Support hose may help with vasodepressor symptoms.
- Dietary high-salt intake may be helpful.
Issues for Referral
Symptomatic patients need to be referred for further evaluation.
- Carotid sinus denervation by surgery or radiation therapy for selected patients
- Adventitial stripping is a surgical technique that is effective and relatively safe in many patients.
- Permanent pacing may help prevent recurrent symptoms in patients with cardioinhibitory component.
- Carotid endarterectomy for patients with atheroma
- Avoid pressure on the neck, tight collars, and neckties.
- Restrictions on driving or other potentially hazardous activities until cleared by the physician
- Take medications as prescribed.
- Avoid medications that might cause hypotension.
- May be serious if syncope is associated with atheromatous narrowing of sinus artery or basilar artery
- Recurrence rate is difficult to quantify.
- Frequent falls, leading to injuries and fractures
- Rarely, sudden death from asystole
1. 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 to update the 1998 pacemaker guidelines).
2. Alboni P, Brignole M, Menozzi C, et al. Diagnostic value of history in patients with syncope with or without heart disease. J Am Coll Cardiol. 2001;37:1921–8.
3. Bartoletti A, Fabiani P, Bagnoli L, et al. Physical injuries caused by a transient loss of consciousness: main clinical characteristics of patients and diagnostic contribution of carotid sinus massage. Eur Heart J. 2008;29:618–24.
4. Davies AJ, Kenny RA. Frequency of neurologic complications following carotid sinus massage. Am J Cardiol. 1998;81:1256–7.
5. Humm AM, Mathias CJ. Unexplained syncope–is screening for carotid sinus hypersensitivity indicated in all patients aged >40 years? J Neurol Neurosurg Psychiatry. 2006;77:1267–70.
6. 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. 2001;38:1491–6.
7. Kerr SR, Pearce MS, Brayne C, et al. Carotid sinus hypersensitivity in asymptomatic older persons: implications for diagnosis of syncope and falls. Arch Intern Med. 2006;166:515–20.
8. Mathias CJ, Deguchi K, Schatz I. Observations on recurrent syncope and presyncope in 641 patients. Lancet. 2001;357:348–53.
See Also (Topic, Algorithm, Electronic Media Element)
337.01 Carotid sinus syndrome
51723007 Carotid sinus syncope (disorder)
- Pressure on the carotid sinus causes asystole of >3 seconds (cardioinhibitory) and/or a drop in systolic BP ≥50 mm Hg, reproducing symptoms.
- It is clinically important to distinguish carotid sinus syndrome from sick sinus syndrome.
- The finding of carotid sinus hypersensitivity does not exclude other causes of syncope.