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Carotid Sinus Hypersensitivity (CSH)

Basics

  • Exaggerated response to carotid sinus stimulation causing syncope or presyncope.
  • Carotid sinuses contain baroreceptors regulating blood pressure via vagal and sympathetic pathways.
  • Stimulation (e.g., neck turning, shaving) causes increased baroreceptor firing β†’ vagal activation and/or sympathetic inhibition β†’ bradycardia and/or hypotension.
  • Diagnostic criteria vary:
  • Standard: pause β‰₯3 sec or systolic BP drop β‰₯50 mmHg.
  • Krediet: pause β‰₯6 sec or MAP <60 mmHg for β‰₯6 sec.
  • Kerr: >95th percentile pause (>7.3 sec) or >77 mmHg systolic drop.

Subtypes

  • Cardioinhibitory (70-75%): asystole β‰₯3 sec.
  • Vasodepressive (5-10%): systolic BP drop β‰₯50 mmHg.
  • Mixed (20-25%): combination of both.

Carotid Sinus Syndrome (CSS)

  • CSH plus syncope.
  • Spontaneous CSS: syncope triggered by accidental carotid stimulation (e.g., shaving, tight collars).
  • Induced CSS: syncope diagnosed by CSM without obvious trigger.

Epidemiology

  • Primarily elderly males >65 years.
  • Associated with CAD, hypertension.
  • Prevalence up to 39% in adults >65.
  • CSH contributes to ~30% of unexplained syncope in elderly.

Etiology and Pathophysiology

  • Reflex arc or target organ changes cause hypersensitivity.
  • Possibly part of generalized autonomic dysfunction.
  • Bradycardia/asystole mediated by vagal efferents; vasodilation/hypotension by decreased sympathetic tone.
  • Impaired cerebral autoregulation in symptomatic patients.
  • Atherosclerosis reduces carotid sinus compliance and afferent signaling.
  • Causes include carotid body tumors, neck surgery scarring, lymphadenopathy, metastatic cancer.

Risk Factors

  • Advanced age, male sex, CAD, hypertension, diabetes.

Associated Conditions

  • Carotid sinus syncope, sick sinus syndrome, AV block, CAD, hypertension, orthostatic hypotension, vasovagal syncope, Alzheimer's, Parkinson's disease.

Diagnosis

History

  • Recurrent, sudden, unexplained syncope with full recovery.
  • Unexplained falls (especially cardioinhibitory subtype).
  • Dizziness or presyncope (vasodepressor/mixed subtypes).
  • Syncope triggered by neck movements, shaving, tight collars.
  • Medications potentiating vagal response (digoxin, Ξ²-blockers, physostigmine, morphine, methacholine).

Physical Exam

  • Usually normal except during carotid stimulation: bradycardia, hypotension, pallor, diaphoresis.

Differential Diagnosis

  • Neurocardiogenic syncope, orthostatic hypotension, situational syncope, POTS, autonomic insufficiency, hypovolemia, arrhythmias, sick sinus syndrome, cerebrovascular insufficiency, metabolic, psychogenic causes.

Diagnostic Tests

  • Carotid sinus massage (CSM) in patients >40 years with unexplained syncope.
  • Technique: supine position, continuous BP and ECG monitoring, 5-10 sec firm massage over carotid sinus.
  • Test positive if asystole β‰₯3 sec and/or systolic BP drop β‰₯50 mmHg with symptom reproduction.
  • Tilt-table testing if initial CSM nondiagnostic.
  • Contraindications: carotid bruit with >70% stenosis, recent MI/TIA/stroke (last 3 months).
  • Relative contraindications: VT/VF history.
  • Carotid duplex scan before CSM if bruit present.
  • ECG for pauses or AV block.

Treatment

General Measures

  • No treatment for asymptomatic isolated CSH; educate and avoid triggers.
  • Increase salt and fluids for vasodepressor subtype if no contraindications.
  • Driving restrictions if syncope present.

Medications

  • No agent with proven long-term efficacy for recurrent symptomatic CSH.
  • Fludrocortisone or midodrine may help vasodepressor symptoms (off-label).
  • Atropine acutely for cardioinhibitory bradycardia.
  • SSRIs (sertraline, fluoxetine) may benefit pacemaker nonresponders.

Procedures

  • Permanent pacing may reduce syncope frequency in cardioinhibitory/mixed subtypes but not eliminate it.
  • Surgery (carotid sinus denervation) not recommended due to complications.
  • Surgery indicated for mass lesions causing CSH.

Ongoing Care and Patient Education

  • Avoid neck pressure maneuvers (tight collars, neckties).
  • Restrict driving until cleared.
  • Avoid vasodilator medications that worsen symptoms.
  • Teach supine positioning during presyncope.
  • Provide reassurance and counsel on recurrence risk.

Prognosis

  • CSH not independently linked to increased mortality.
  • Untreated CSS syncope recurrence up to 62% in 4 years.
  • Pacemaker implantation reduces falls in cardioinhibitory CSH.

Complications

  • Kerr criteria-defined CSH linked to increased mortality; further study needed to identify pacing candidates.

Clinical Pearls

  • Consider CSH in elderly with unexplained syncope, dizziness, or falls.
  • Always auscultate for carotid bruit before CSM.
  • Diagnosis requires firm carotid massage for 5-10 seconds with ECG and BP monitoring.
  • Pacemakers helpful in recurrent cardioinhibitory or mixed CSH.
  • CSH diagnosis does not exclude other syncope causes.

References

  1. McDonald C, Pearce MS, Newton JL, et al. Modified criteria for carotid sinus hypersensitivity are associated with increased mortality in a population-based study. Europace. 2016;18(7):1101-1107.
  2. Kadermuneer P, Sandeep R, Haridasan V, et al. Prevalence and one-year outcome of carotid sinus hypersensitivity in unexplained syncope: a prospective cohort study from South India. Indian Heart J. 2019;71(1):1-6.
  3. Runser LA, Gauer RL, Houser A. Syncope: evaluation and differential diagnosis. Am Fam Physician. 2017;95(5):303-312.