Cardiology

Background 

Carotid sinus hypersensitivity (CSH) is a condition in which there is an exaggerated response to carotid sinus baroreceptor stimulation, leading to transient bradycardia, hypotension, or both. This response can precipitate syncope or near-syncope and is a form of reflex syncope, particularly prevalent in older adults. 

II) Classification/Types 

By Hemodynamic Response: 

• Vasodepressor type: ≥50 mmHg drop in systolic blood pressure without significant bradycardia. 

• Mixed type: Combination of cardioinhibitory and vasodepressor responses. 

By Etiology: 

• Spontaneous CSH: Occurs without external stimulus, often during head turning, shaving, or tight collar use. 

• Induced CSH: Diagnosed via CSM during clinical evaluation. 

Pathophysiology 

The carotid sinus contains baroreceptors that regulate heart rate and vascular tone through autonomic feedback. In CSH, these receptors exhibit hyperactivity, typically due to aging or autonomic imbalance. Stimulation causes excessive vagal discharge (cardioinhibitory) and/or withdrawal of sympathetic tone (vasodepressor), leading to bradycardia, hypotension, and cerebral hypoperfusion. 

Epidemiology 

• Affects predominantly elderly individuals, especially males over 65 years. 

• Accounts for 10–20% of unexplained syncope in geriatric populations. 

• Often underdiagnosed due to intermittent and non-specific symptoms. 

Etiology 

I) Causes 

• Age-related degeneration of autonomic reflexes 

• External neck pressure (tight collars, shaving, head rotation) 

• Neck tumors, lymphadenopathy, or carotid body tumors 

• History of neck surgery or radiation 

II) Risk Factors 

• Advanced age 

• Structural heart disease 

• Autonomic dysfunction (e.g., diabetes) 

• Prior stroke or carotid artery disease 

• Medications affecting AV nodal conduction (beta-blockers, digoxin) 

Clinical Presentation 

I) History (Symptoms) 

• Recurrent syncope or presyncope 

• Episodes triggered by head turning, neck pressure, or shaving 

• Sudden collapse without warning 

• Fatigue, dizziness, or blurred vision during triggers 

II) Physical Exam (Signs) 

• Often normal between episodes 

• May reproduce symptoms with carotid sinus massage (under monitoring) 

• Evidence of bradycardia or hypotension during CSM 

• Evaluate for carotid bruits or masses 

Differential Diagnosis (DDx) 

• Vasovagal syncope 

• Orthostatic hypotension 

• Sick sinus syndrome 

• Atrioventricular block 

• Seizure disorders 

• Vertebrobasilar insufficiency 

• Neurogenic orthostatic hypotension 

Diagnostic Tests 

Initial Work-Up 

• ECG: Rule out intrinsic conduction system disease 

• Holter monitor or event recorder: Identify spontaneous bradyarrhythmias 

• Carotid Sinus Massage (CSM): 

• Performed under continuous ECG and BP monitoring 

• Reproduction of symptoms with documented pause ≥3 sec or SBP drop ≥50 mmHg confirms diagnosis 

Advanced Testing 

• Tilt-table testing: If vasovagal syncope is suspected 

• Echocardiography: Rule out structural cardiac causes 

• MRI brain/CT angiography: If stroke or structural lesion suspected 

Treatment 

I) Acute Management 

• Avoid known triggers (e.g., tight collars) 

• Patient education on head movement and posture 

• Adjust or discontinue medications that exacerbate bradycardia 

• Atropine may be used acutely if symptomatic bradycardia occurs 

II) Chronic Management 

• Cardioinhibitory CSH: 

• Permanent pacemaker implantation (most effective therapy) 

• Vasodepressor CSH: 

• Difficult to treat; options include fludrocortisone or midodrine 

• Mixed CSH: 

• Pacemaker for cardioinhibitory component 

• Address vasodepressor part with fluids, compression stockings, or medication 

Medications 

Device Therapy 

• Permanent pacemaker: Class I indication for recurrent syncope due to cardioinhibitory CSH 

• Dual-chamber pacing (DDD mode): Preferred to reduce symptomatic pauses 

Patient Education, Screening, Vaccines 

Education 

• Avoid tight clothing around the neck 

• Caution with shaving or neck manipulation 

• Monitor for pre-syncopal symptoms 

• Adherence to pacing follow-up and device checks if implanted 

Screening/Prevention 

• Routine CSM evaluation in unexplained syncope in elderly 

• Avoid unnecessary neck pressure in susceptible individuals 

Vaccinations 

• Routine adult immunizations (influenza, pneumococcus) recommended 

• No vaccines specifically indicated for CSH 

Consults/Referrals 

• Cardiology: For pacing evaluation and syncope work-up 

• Electrophysiology: For specialized assessment and pacemaker placement 

• Neurology: If seizure or CNS etiology suspected 

• Geriatrics: For evaluation of falls and syncope in elderly 

Follow-Up 

Short-Term 

• Monitor pacing thresholds and symptom recurrence post-implant 

• Assess for medication side effects and hypotensive episodes 

Long-Term 

• Regular device checks (every 3–6 months) 

• Repeat CSM only if new or recurrent symptoms 

• Evaluate for orthostatic hypotension or progression to other arrhythmias 

Prognosis 

• Excellent in cardioinhibitory type with pacemaker therapy 

• Less favorable in vasodepressor or mixed types due to lack of definitive therapy 

• Risk of injury due to falls or accidents remains if not adequately managed 

• Early recognition and pacing significantly reduce recurrence and improve quality of life