Carotid Sinus Syndrome


Risk

  • 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

Perioperative Risks

  • 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.

Worry About

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

  • Severity of CSS and frequency of syncopal episodes

  • Hemodynamic compromise: Bradycardia and/or hypotension

Overview

  • 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.

Etiology

  • 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

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