Carotid Sinus Syndrome

Male > female

9% of pts with recurrent syncope; history of falls

Increased incidence with age, rarely below age 50 y

Peripheral vascular disease

Head and neck cancer

Presence of CSS does not increase rate of mortality, sudden death, or stroke more when compared with pts with similar age and risk factors.

CSS does increase morbidity, secondary to injuries sustained during syncopal episodes.

Presence of comorbid conditions: CAD, carotid stenosis, and neck tumor

Severity of CSS and frequency of syncopal episodes

Hemodynamic compromise: Bradycardia and/or hypotension

The carotid sinus reflex occurs with changes in transmural pressure of the baroreceptors at the carotid sinus.

Reflex arc:

• Afferent signals are sent via glossopharyngeal and vagus nerves to the nucleus tractus solitarius.

• Efferent signaling occurs through sympathetic and vagus nerves to the heart and blood vessels.

CSH is defined as an exaggerated response to baroreceptor stimulation.

CSS occurs in pts with CSH when direct CSM or accidental neck stimulation produces symptoms such as dizziness/syncope or bradycardia and/or hypotension.

Three types of CSS:

• Cardioinhibitory type, which is due to vagal stimulation of SA and AV nodes, resulting in sinus bradycardia and may be treated with atropine.

• Vasodepressor type, which results in hypotension due to inhibition of vasomotor sympathetic tone; differentiated with cardioinhibitory type by not responding to atropine treatment.

• Mixed type, which results in bradycardia and loss of vasomotor tone.

Diagnosis: Perform CSM in supine position and massage each carotid individually for 5 second. Test is positive if any of the three are true: asystole greater than 3 sec (cardioinhibitory type); decrease in SBP >50 mm Hg (vasodepressor type); and combination or mixed type. There have been some new suggestions that SBP ≤85 mm Hg may be more sensitive in correctly identifying vasodepressor type.

Afferent overshoot from external pressure due to internal atherosclerotic changes diminishing carotid sinus compliance

Degenerative process of the nucleus tractus solitarius that occurs with age and is associated with sternocleidomastoid movement (head turning or looking down)

Possible association with dementia, especially DLB

Mechanical deformation from neck tumors