SYNCOPE

Syncope is defined as a temporary loss of consciousness or postural tone.  Approximately 15% of children have a history of syncope and the majority of cases are benign.  The pathophysiology is thought to be a transient decrease in cerebral blood flow and frequently the individuals will experience some light-headedness or dizziness prior to the syncopal episode.  There is a high rate of recurrences and if specific causes are found, treatment is effective in preventing episodes.

Etiology

1. Cardiac (Structural and Electrical)
     a. Outflow obstruction (Aortic stenosis, hypertrophic cardiomyopathy)
     b. Arrhythmia (Congenital long QT syndrome, Brugada Syndrome, Wolff-Parkinson-White Syndrome)
     c. Ischemia (Coronary artery disease), Acute myocarditis (Coxsackie A, B and Adenovirus)

2. Non-Cardiac Causes/Mimics
    a. Seizures (typically include aura, prolonged tonic-clonic phase and post-ictal state)
    b. Migraines (basilar) may present with LOC, ataxia, vertigo
     c. Orthostatic hypotension (occurring with postural change and abrupt drop in BP)
     d. Psychogenic (Conversion disorder); typically seen in adolescents
     e. Breath-holding spells (typically 6-24mos); triggered by emotional insult
     f. Metabolic (Hypoglycemia in insulin-dependent DM/electrolyte disturbances)

     g. Pulmonary hypertension (usually preceded by exertional dyspnea)
     h. Toxic Exposure (CO poisoning,  cocaine, alcohol, barbituates, TCAs)

3. Vasovagal (Neurocardiogenic)
     a. Fear/panic/anxiety
     b. Dehydration/extended period of standing

Evaluation

1. History - provided by the patient and observer of the event

     a. Preceding event: aura, prodrome, specific signs/symptoms before event (nausea, cold sweat,            headache, visual changes, palpitations)

     b. Association with exercise (suggesting cardiac etiology/risk of sudden death)

     c. State of hydration/nutrition at the time of the event  
     d. Loss of consciousness (LOC), incontinence

     e. Post-ictal signs/symptoms, duration and nature of recovery
     f. Family history (seizures, migraine, sudden death, cardiomyopathies)
     g. History of similar episodes
     h. Emotional state (social stressors)
     i. Drug use or medications (pro-arrhythmic medications; QT-prolonging meds)
     j. Pregnancy

2. Physical Examination
     a. Vital Signs (including orthostatic BP)

     b. Cardiac Exam (Murmurs, UE/LE pulses, capillary refill)
     b. Fluid Status Assessment (Mucous membranes, skin turgor)

3. Cardiac evaluation

a. Always include EKG and evaluate for HR, QT interval, T-wave morphology; consider          echocardiogram, holter monitor, stress testing

4. Neurologic Evaluation

a. EEG with possible neuroimaging if history consistent with seizures.

5. Tilt table test

      a.  patient strapped to a table lying flat and tilted completely or almost completely upright

      b. symptoms, BP, HR, EKG and sometimes O₂ saturations are recorded

      c. Positive clinical responses include:

-        vasodepressor reponse: ³50% decrease in mean arterial BP (40% of positive results)

-        mixed hypotensive/bradycardic response: ³50% decrease in mean arterial pressure and HR (50% of positive results)

-        cardioinhibitory response: sudden severe bradycardia of asystole (5-10% of positive responses)

Management

1. Arrhythmia: medications (ex. Disopyramide) or ablative procedures

2. Cardiac structural etiology: cardiology referral, possible catherization, valvuloplasty or transplant

3. Breath holding spells: parental reassurance; avoid precipitating events and triggers

4. Migraines: maintenance medications (NSAIDs and acetaminophen); consider abortive treatments        (triptans) 

5. Seizures: medications depend on seizure type

6. Psychogenic: consider psychiatric evaluation

7. Vagovagal

          a. Identify individual triggers (syncope journal)
     b. Leg pumping and tensioning, leg crossing, squatting (increasing venous return)
     c. If preceding signs/symptoms, interrupt activity and lie down prior to LOC
     d. Elastic hose (increasing venous return)
     e. Maintain appropriate hydration and nutrition; avoid caffeinated beverages (due to diuretic effect)

References

1. Willis John. Syncope  Pediatrics in Review Vol 21 No. 6 June 2000
2. Strieper MJ.  Distinguishing benign syncope from life-threatening causes of syncope.  Seminars in Pediatric Neurology. 2005; 12:32-38
3. Soteriades E.S. Incidence and Prognosis of Syncope.  NEJM Vol 347 No. 12 Sept 19 2002 Page 878
4. Grubb B. Neurocardiogenic Syncope.  NEJM March 10, 2005