Carotid Sinus Syndrome

• Christopher Pickett, M.D.
• Barry Fine, M.D., PH.D.

 Basic Information

Definition

Light-headedness, dizziness, presyncope, or syncope in a patient with carotid sinus hypersensitivity is defined as carotid sinus syndrome (CSS). Carotid sinus hypersensitivity is the exaggerated response to carotid stimulation resulting in bradycardia, hypotension, or both. CSS is often considered a variant of neurocardiogenic syncope. The 2013 European Guidelines (ESC) defines CSS as syncope with reproduction of symptoms during carotid sinus massage of 10-second duration. There are two components of CSS: cardioinhibitory and vasodepressor.

Synonyms

1. Carotid sinus syncope

2. CSS

3. Carotid sinus hypersensitivity

ICD-10CM CODES
G90.01	Carotid sinus syncope
R55	Syncope and collapse

Epidemiology & Demographics

1. •

   Carotid sinus hypersensitivity accounts for 1% of syncopal episodes (Fig. 1).

   

2. •

   Carotid sinus hypersensitivity is frequently associated with atherosclerosis and diabetes mellitus.

3. •

   Incidence increases with age, with an average age of onset at 61 to 74 yr. Fig. 2 illustrates age distribution of the patients with carotid sinus syndrome.

   

4. •

   Men are affected more often than women (2:1).

5. •

   CSS is rarely found in patients younger than 50 yr.

Mechanism

1. •

   The carotid sinus is located in the internal carotid artery.

2. •

   There is a reflex loop between the mechanoreceptors of the carotid sinus and the vagal nucleus in the midbrain.

3. •

   There is an exaggerated cardioinhibitory and vasodepressor reaction caused by decreased sympathetic and increased parasympathetic outflow to the heart and vasculature, respectively.

Physical Findings & Clinical Presentation

1. •

   Often associated with sudden neck movements, especially rotation, neck palpation, shaving, or tight-fitting collars, but can occur in the absence of clear provocation.

2. •

   Mild form has symptoms such as fatigue, lightheadedness, nausea, warmth, pallor, or diaphoresis.

3. •

   More severe form of the condition has sudden abrupt loss of consciousness without prodrome.

Properly performed carotid sinus massage (CSM) at the bedside is diagnostic. The European Society of Cardiology recommends carotid sinus massage as part of the exam in patients with syncope of unknown etiology and age over 40. This maneuver can elicit three types of responses in patients with carotid sinus hypersensitivity (see “Diagnosis”).

1. 1.

   CSM should be performed with the patient in the supine and upright positions while monitoring the patient’s blood pressure by cuff and heart rate by ECG.

2. 2.

   CSM should be performed on both the right and left sides but on only one carotid artery at a time.

3. 3.

   Vigorous pressure is applied over the carotid artery, directed posterior to compress the artery against the spinous process of the vertebrae, at the level of the cricoid cartilage for 10 to 30 seconds. Repeat on the opposite side if no effect is produced.

4. 4.

   Contraindications to CSM include the presence of carotid artery bruits, documented carotid artery stenosis >70%, history of stroke or transient ischemic attack <3 mo, history of myocardial infarction <6 mo, history of serious ventricular arrhythmia, or prior carotid endarterectomy.

5. 5.

   Complications of CSM are rare (0.1%-1%) and may include transient visual disturbance, transient paresis, tachyarrhythmias, or bradyarrhythmias.

6. 6.

   False-positive results with carotid sinus massage may be relatively common in the elderly population. Thus alternative explanations for syncope should be investigated prior to attribution of symptoms to carotid sinus hypersensitivity.

Etiology

1. •

   Idiopathic

2. •

   Head and neck tumors (e.g., thyroid)

3. •

   Significant lymphadenopathy

4. •

   Carotid body tumors

5. •

   Prior neck surgery

Diagnosis

1. •

   The diagnosis of CSS is made in a patient with a history of syncope when carotid sinus hypersensitivity is demonstrated by CSM and no other cause of syncope is identified.

2. •

   CSM can elicit three types of responses diagnostic of carotid sinus hypersensitivity:

   1. 1.

      Cardioinhibitory type: CSM producing (1) asystole for at least 3 sec in the absence of symptoms or (2) reproduction of symptoms occurring with a decline in heart rate of 30% to 40% or asystole of up to 2 sec in duration. Symptoms should not recur when CSM is repeated after atropine infusion.

   2. 2.

      Vasodepressor type: CSM producing (1) a decrease in systolic blood pressure of 50 mm Hg in the absence of symptoms or 30 mm Hg in the presence of neurologic symptoms; (2) no evidence of asystole; or (3) neurologic symptoms that persist after infusion of atropine.

   3. 3.

      Mixed type: CSM producing both types of responses.

Differential Diagnosis

All causes of syncope

Workup

1. •

   CSS is a diagnosis of exclusion.

2. •

   Exclude other causes of syncope or presyncope: detailed history, physical examination including orthostatic vital signs, ECG. Other tests should be considered depending on the clinical setting.

Treatment

Nonpharmacologic Therapy

Reassurance and education are important. Avoid applying neck pressure from tight collars, shaving, or rapid head turning.

Acute General Rx

Treatment will vary according to the type of carotid hypersensitivity response and symptoms present (see “Chronic Rx”).

Chronic Rx

Therapy is divided into three classes: medical, surgical (carotid denervation), and cardiac pacing.

1. •

   Surgical therapy has been largely abandoned except in cases of compressing tumors or masses responsible for CSS.

2. •

   For infrequent and mildly symptomatic carotid sinus hypersensitivity of either the cardioinhibitory or vasodepressor type, treatment is generally not necessary.

3. •

   Cardiac pacing is indicated in patients with recurrent syncope in whom CSM induces ventricular asystole of more than 3 seconds, especially if accompanied by reproduction of symptoms.

Permanent pacing is not indicated for carotid sinus hypersensitivity with no, or only vague, symptoms.

For symptomatic patients with a vasodepressor response to CSM:

1. •

   No medical treatment is proven to be effective

2. •

   Drugs, such as vasodilators, that would worsen the response should be discontinued or reduced if feasible

3. •

   Permissive hypertension

4. •

   Increased fluids (≥2 L) and salt intake (>6 g/day)

5. •

   Sympathomimetics: midodrine, titrate from 2.5 to 10 mg tid based on BP and therapeutic response (major side effect in urinary retention in elderly males)

6. •

   Serotonin-specific reuptake inhibitors

7. •

   Fludrocortisone

8. •

   Elastic knee-high or thigh-high stockings

9. •

   Carotid sinus denervation

For symptomatic patients with CSS with a mixed response to CSM:

1. •

   Combination of dual-chamber permanent pacemaker and agents used to treat vasodepressor response

Disposition

1. •

   Up to 50% of the patients have recurrent symptoms.

2. •

   No increased mortality rate in patients with idiopathic CSS compared with the general population.

Referral

Cardiology referral is indicated if pacemaker placement is being considered.

Pearls & Considerations

1. •

   The most common type of CSS is cardioinhibitory, followed by mixed and vasodepressor responses.

2. •

   Driving restrictions in the 2009 ESC syncope update and 2006 AHA/ACCF consensus document on syncope are stratified according to whether patients have mild or severe syncope.

3. •

   Mild carotid sinus syndrome is defined as infrequent mild symptoms (without syncope), with clear precipitating causes (usually standing), warning signs, and infrequent occurrence. For patients with mild sinus hypersensitivity, no driving restrictions are recommended for private or commercial driving.

4. •

   Severe carotid sinus syndrome is marked by syncope without warning occurring in any position, without precipitating causes and frequent occurrences. For patients with severe hypersensitivity, all driving is prohibited. If symptoms are controlled, driving is permitted 1 to 6 months after, based on the modality of treatment.

Comments

Prognosis depends on the underlying cause.

Related Content

1. Syncope (Patient Information)

2. Orthostatic Hypotension (Related Key Topic)

3. Syncope (Related Key Topic)