Cardiology

Syncope

Introduction

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.

In the case of vasovagal syncope, a paradoxic withdrawal of sympathetic activity secondary to elevated catecholamines that stimulate mechanoreceptors is thought to be the cause. 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). Often associated with exercise, and always warrants follow up with a pediatric cardiologist. 

  • Outflow obstruction (Aortic stenosis, hypertrophic cardiomyopathy)
  • Arrhythmia (Congenital long QT syndrome, Brugada Syndrome, Wolff-Parkinson-White Syndrome)
  • Ischemia (Coronary artery disease), Acute myocarditis (Coxsackie A, B and Adenovirus)

2. Non-Cardiac Causes/Mimics

  • Seizures (typically include aura, prolonged tonic-clonic phase and post-ictal state)
  • Migraines (basilar) may present with LOC, ataxia, vertigo. Family history is positive in 75% of cases.
  • Orthostatic hypotension (occurring with postural change and at least a 20 mm Hg drop in systolic BP)
  • Psychogenic (Conversion disorder); typically seen in adolescents
  • Breath-holding spells (typically 6-24mos); triggered by emotional insult. These will progress to neurocardiogenic syncope in 17% of cases.
                            CLICK BELOW FOR VIDEO EXAMPLE
                               breath_1.png
  • Metabolic (Hypoglycemia in insulin-dependent DM/electrolyte disturbances
  • Pulmonary hypertension (usually preceded by exertional dyspnea)
  • Toxic Exposure (CO poisoning,  cocaine, alcohol, barbituates, TCAs)

3. Vasovagal (Neurocardiogenic) - most common type of syncope. Uusally associated with a prodrome (nausea/vomiting/vertigo/sweating). No post-ictal state, vs. seizures. Commonly associated with:

  • Fear/panic/anxiety
  • Dehydration/extended period of standing
  • Often associated with depressive symptamatology

CLICK BELOW FOR VIDEO EXAMPLE
vasovagal_0.png
Example of vasovagal syncope during a stressful spelling bee and prolonged standing.   https://www.youtube.com/watch?v=42apZ5wETOE

Evaluation

1. History - important points to ask of the patient and observer of the event

  • Preceding event: aura, prodrome, specific signs/symptoms before event (nausea, cold sweat,  headache, visual changes, palpitations)
  • Association with exercise (suggesting cardiac etiology/risk of sudden death)
  • State of hydration/nutrition at the time of the event  
  • Loss of consciousness (LOC), incontinence
  • Post-ictal signs/symptoms, duration and nature of recovery
  • Family history (seizures, migraine, sudden death, cardiomyopathies)
  • History of similar episodes
  • Emotional state (social stressors)
  • Drug use or medications (pro-arrhythmic medications; QT-prolonging meds)
  • Pregnancy
  • The duration of the episode

2. Physical Examination

  • Vital Signs (including orthostatic BP)
  • Cardiac Exam (Murmurs, UE/LE pulses, capillary refill)
  • Fluid Status Assessment (Mucous membranes, skin turgor)

3. Cardiac evaluation

  • Always include EKG and evaluate for HR, QT interval, T-wave morphology; consider echocardiogram, holter monitor, stress testing as indicated
  • In patients the above diagnostic measures do not detect abnormality, implantable loop recorders can be employed, especially in patients with documented palpitations with their syncope. 

4. Neurologic Evaluation

  • EEG with possible neuroimaging if history consistent with seizures.

5. Tilt table test

  • patient strapped to a table lying flat and tilted completely or almost completely upright
  • symptoms, BP, HR, EKG and sometimes O2 saturations are recorded
  • 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

  • Arrhythmia: medications (ex. Disopyramide) or ablative procedures
  • Cardiac structural etiology: cardiology referral, possible catherization, valvuloplasty or transplant
  • Breath holding spells: parental reassurance; avoid precipitating events and triggers
  • Migraines: maintenance medications (NSAIDs and acetaminophen); consider abortive treatments (triptans)
  • Seizures: medications depend on seizure type
  • Psychogenic: consider psychiatric evaluation
  • Vagovagal
                     
    • Identify individual triggers (syncope journal)
    • Leg pumping and tensioning, leg crossing, squatting (increasing venous return)
    • If preceding signs/symptoms, interrupt activity and lie down prior to LOC
    • Elastic hose (increasing venous return)
    • Maintain appropriate hydration and nutrition; avoid caffeinated beverages (due to diuretic effect)

References

  1. Hyphantis, T., et. al. (2012). Depressive symptoms and neurocardiogenic syncope in children: a 2 year prospective study. Pediatrics, 130(5), 906-913.
  2. Rossano, J., et. al. (2003). Efficacy of implantable loop recorders in establishing symptom-rhythm correlation in young patients with syncope and palpitations. Pediatrics, 112(3), 228-233. 
  3. Snyder, C., (2010). Refer or reassure: guidance on managing patients with syncope. AAP News, 31(5), 18. 
  4. Thilenius, O., et. al. (1991). Tilt test for the diagnosis of unexplained syncope in pediatric patients. Pediatrics, 87(3), 334-338. 
  5. Willis, J. (2000). Syncope. Peds in Review, 21(6), 201-204.