Carotid Sinus Hypersensitivity

Definition

Carotid sinus hypersensitivity (CSH) is a condition where there is an exaggerated response to stimulation of the carotid sinus, a baroreceptor located in the neck. This can result in episodes of syncope (fainting) or presyncope due to a sudden drop in heart rate and blood pressure.

Aetiology

CSH is often idiopathic, but it can be associated with atherosclerosis, head and neck surgery, or neck irradiation. It is more common in older adults and may be triggered by activities such as shaving, wearing tight collars, or turning the head.

Pathophysiology

The carotid sinus contains baroreceptors that help regulate blood pressure. In CSH, these baroreceptors are overly sensitive and can trigger a reflex that causes a sudden decrease in heart rate (bradycardia) and/or dilation of blood vessels (vasodilation), leading to a drop in blood pressure and reduced cerebral perfusion, resulting in syncope or presyncope.

Risk factors

Age (more common in older adults)
Male gender
Atherosclerosis
Previous neck surgery or irradiation
History of syncope or presyncope

Signs and Symptoms

Sudden, transient loss of consciousness
Presyncope (feeling faint without losing consciousness)
Dizziness or light-headedness
Bradycardia (slow heart rate)
Hypotension (low blood pressure)

Red Flags

Recurrent syncope episodes
Syncope associated with injury
Syncope during exertion
History of cardiovascular disease
Abnormal findings on ECG

Investigations

Clinical history and physical examination, focusing on the circumstances of syncope episodes
Carotid sinus massage under monitored conditions to reproduce symptoms and confirm diagnosis
Electrocardiogram (ECG) to assess for arrhythmias or other cardiac abnormalities
24-hour Holter monitoring to detect intermittent bradycardia or arrhythmias
Blood tests to rule out metabolic or infectious causes
Echocardiography to evaluate cardiac structure and function
Neuroimaging (MRI or CT scan) if there are neurological symptoms or red flags

Management

Primary Care Management:

Educate patients to avoid triggers (e.g., avoiding tight collars, careful movements of the head and neck)
Consideration of referral to a cardiologist or specialist in syncope for further evaluation and management
In selected cases, implantation of a pacemaker may be necessary to prevent bradycardia-induced syncope
Review and adjust medications that may exacerbate hypotension or bradycardia

Example Management for Carotid Sinus Hypersensitivity:

A patient diagnosed with CSH should be educated to avoid known triggers such as tight collars and sudden head movements. If episodes are frequent or severe, referral to a cardiologist for potential pacemaker implantation may be warranted. Medications that lower blood pressure or heart rate should be reviewed and adjusted as necessary. The patient may also benefit from a Holter monitor to assess for intermittent arrhythmias that could be contributing to symptoms.

References:

NICE. (2023). Syncope: Management. Retrieved from https://cks.nice.org.uk/topics/syncope/management/
NHS. (2023). Carotid Sinus Hypersensitivity. Retrieved from https://www.nhs.uk/conditions/syncope/
European Society of Cardiology. (2018). Guidelines for the diagnosis and management of syncope. Retrieved from https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Syncope-Guidelines
O'Sullivan, S. B., & Schmitz, T. J. (2016). Physical Rehabilitation. 6th ed. F.A. Davis Company.
Ropper, A. H., & Samuels, M. A. (2019). Adams and Victor's Principles of Neurology. 11th ed. McGraw-Hill Education.