Syncope in Children

Introduction

Syncope is a transient loss of consciousness and postural tone resulting from temporary global cerebral hypoperfusion. It is characterized by rapid onset, short duration, and spontaneous complete recovery. Syncope affects up to 15% of children before the end of adolescence, with peak incidence between ages 15-19 years.

Pathophysiology

Syncope occurs when cerebral blood flow drops below 50% of normal requirements for more than 6-8 seconds, or there is sudden cessation of blood flow for more than 3-4 seconds. The brain's high metabolic demands make it particularly sensitive to perfusion changes, leading to loss of consciousness when blood flow is compromised.

Key Concepts

Understanding syncope requires knowledge of:

• Cerebral autoregulation mechanisms and their limitations
• Cardiovascular reflexes affecting blood pressure and heart rate
• Autonomic nervous system's role in maintaining hemodynamic stability
• Age-specific variations in presentation and risk factors

Clinical Significance

While most pediatric syncope cases are benign (particularly vasovagal syncope), distinguishing these from potentially life-threatening causes is crucial. The initial evaluation must focus on identifying red flags that suggest serious underlying pathology.

Etiology and Classification

Neural-Mediated (Reflex) Syncope

Most common form in children (60-80% of cases)

• Vasovagal Syncope: Triggered by emotional stress, pain, orthostatic stress, or prolonged standing
  • Characterized by prodromal symptoms
  • Often preceded by nausea, pallor, diaphoresis
  • Usually occurs while standing or sitting
• Situational Syncope:
  • Micturition syncope
  • Defecation syncope
  • Cough syncope
  • Post-exercise syncope

Orthostatic Syncope

Results from impaired autonomic response to postural changes

• Volume depletion
• Medications (diuretics, vasodilators)
• Autonomic dysfunction
• Post-viral orthostatic hypotension

Cardiac Syncope

Less common but potentially life-threatening (5% of cases)

• Structural Abnormalities:
  • Hypertrophic cardiomyopathy
  • Aortic stenosis
  • Pulmonary hypertension
  • Coronary artery anomalies
• Electrical Disorders:
  • Long QT syndrome
  • Wolff-Parkinson-White syndrome
  • Brugada syndrome
  • Catecholaminergic polymorphic ventricular tachycardia

Neurologic Causes

May mimic syncope but have different mechanisms

• Seizures
• Migraine-associated syncope
• Basilar artery migraine
• Breath-holding spells

Clinical Assessment

History Taking

Detailed history is crucial and should include:

• Event Description:
  • Circumstances and triggers
  • Position when syncope occurred
  • Activity preceding event
  • Presence of prodromal symptoms
  • Duration of unconsciousness
  • Post-event symptoms and recovery
• Past Medical History:
  • Previous syncope episodes
  • Cardiac conditions
  • Chronic illnesses
  • Current medications
• Family History:
  • Sudden cardiac death
  • Unexplained death before age 50
  • Inherited cardiac conditions
  • Seizure disorders

Physical Examination

Comprehensive examination focusing on:

• Vital Signs:
  • Blood pressure in both arms
  • Orthostatic blood pressure measurements
  • Heart rate and rhythm
  • Respiratory rate
• Cardiac Examination:
  • Heart sounds and murmurs
  • Peripheral pulses
  • Signs of heart failure
• Neurological Examination:
  • Mental status
  • Cranial nerves
  • Motor and sensory function
  • Deep tendon reflexes

Diagnostic Studies

Based on history and physical examination findings:

• Initial Studies:
  • 12-lead ECG (mandatory)
  • Complete blood count
  • Basic metabolic panel
  • Blood glucose
• Additional Studies (if indicated):
  • Echocardiogram
  • Holter monitor
  • Event recorder
  • Tilt table testing
  • Exercise stress test
  • Electroencephalogram (EEG)

Management

Initial Management

Immediate actions during syncope episode:

• Ensure patient safety and prevent injury
• Position patient supine with legs elevated
• Assess and maintain airway, breathing, circulation
• Monitor vital signs
• Obtain detailed event description from witnesses

Specific Management Strategies

Vasovagal Syncope

• Non-pharmacological Measures:
  • Education about trigger recognition
  • Physical counterpressure maneuvers
  • Adequate hydration (2-2.5L/day)
  • Regular exercise
  • Salt supplementation if appropriate
• Pharmacological Treatment:
  • Beta-blockers (selected cases)
  • Fludrocortisone (volume expansion)
  • Midodrine (alpha-agonist)

Orthostatic Syncope

• Volume repletion
• Compression stockings
• Medication adjustment if necessary
• Treatment of underlying causes

Cardiac Syncope

• Immediate cardiology consultation
• Specific treatment based on underlying condition:
  • Antiarrhythmic medications
  • Implantable cardioverter-defibrillator
  • Surgical intervention if needed

Red Flags

High-Risk Features

• Event Characteristics:
  • Syncope during exertion
  • Syncope while supine
  • Syncope without prodrome
  • Syncope with chest pain or palpitations
• Physical Findings:
  • Pathological heart murmur
  • Abnormal ECG findings
  • Focal neurological deficits
  • Evidence of injury
• Historical Factors:
  • Family history of sudden death
  • Previous cardiac disease
  • Known arrhythmia
  • Multiple episodes without clear trigger

Further Reading

• Expert Consensus on Pediatric Syncope
• AHA Scientific Statement on Syncope