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Cardiac Syncope


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Cardiac syncope is extremely rare but potentially fatal.

24% incidence in subsequent cardiac arrest – 10 Australian youths die suddenly every week due to SADS (Sudden Arrhythmic Death Syndrome).

These deaths are rare, but preventable. We see a lot more cases with warning symptoms than deaths. We need to recognise the importance of the identification of cardiac syncope to prevent death.

This post is part of our Syncope Sunday series – you can read the other posts: Post 1 – what is syncope?; Post 2 – reflex syncope

How do SADS conditions present to the ED?

  • Collapse
  • Fit
  • Faint
  • Cardiac arrest

A retrospective study at RCH, Melbourne 2012 demonstrated that syncope was leading cause for presentation of new diagnosis of conduction disorders and VT.

How do I differentiate cardiac syncope from neurally mediated syncope?

A simple faint has:

  • Warning symptoms (felt faint)
  • Provoking factors (hot, tired stressed, hungry, emotion, full stomach etc)
  • Standing up at the time
  • Pale before & during event
  • May jerk limbs especially if not laid down
  • No headache or post-ictal behaviour
  • Past history of faints

Cardiac syncope has:

  • Relationship to exercise
  • No warning symptoms
  • Higher incidence of injuries
  • Pale during event
  • Rapid recovery
  • Previous history of blackouts, shortness of breath or chest tightness during exertion, or palpitations
  • Family history of young death

The causes of SADS can be classified as follows:

Structural heart disease

  • Cardiomyopathies (HOCM, DCM, RCM, ARVC)*
  • Myocarditis
  • Congenital heart disease (abnormal valves, chambers, or anomolous coronary arteries, from birth)

Conduction disease

  • WPW
  • Re-entrant tachycardias

Ion channelopathies

  • Long / short QT Syndrome (natural or iatrogenic)
  • Brugada
  • CPVT (Catecholaminergic Polymorphic Ventricular Tachycardia)

In the next post we will look at some examples of these on ECGs…

*HOCM = hypertrophic obstructive cardiomyopathy

DCM = dilated cardiomyopathy

RCM = restrictive cardiomyopathy

ARVC = arrhythmogenic right ventricular cardiomyopathy (AKA arrhythmogenic right ventricular dysplasia – ARVD)

About the authors

  • Elayne Forbes is a Paediatric Emergency Fellow working at Sydney Children's Hospital.


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1 thought on “Cardiac Syncope”

  1. Thanks so much for this valuable article. It immediately sent me in search of statistics for the US, and I had great difficulty locating solid statistics regarding SADS in kids in the US. I ultimately found one source that cited 1-2 SADS deaths per 100,000 children per year (Cleveland Clinic) and given that there are 75 million children in the US, that would yield 14 to 29 pediatric deaths per week. Note that this is just a guesstimate based on internet research. What statistics were you working with regard to the incidence in Australia?

    Also, you indicated that cardiac syncope is often associated with exertion. Is there evidence to support that? I found the 2011 UK National Audit of Sudden Arrhythmic Death Syndrome which seemed to state that most SADS deaths occurred at rest (I note that the data regarding activity did not differentiate between adults and kids). It would of course make sense that exertion would trigger arrhythmias, but I didn’t know if there had been a rigorous study of this question.

    Thank you.

    Eric Jaeger



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