Paediatric medicine - Syncope in childhood

In the first of this new series, Dr Dan Hindley looks at the causes of fainting.

I have fainted twice, once as a medical student while waiting for a long, hot labour to finish and once more recently when I cut my finger on a broken glass while washing up.

Similarly, many reading this will have suffered syncope - by the age of 20, 20 per cent of men and 50 per cent of women will have fainted at least once. Fainting is unpleasant for the patient and alarming for observers, but it is so common that it is often managed without medical treatment.

Advice is sought if events are recurrent, severe or look like epileptic seizures.

GPs are often faced with patients who have experienced a simple faint, but are all too aware that syncope may be associated with more sinister pathology. The majority of syncopes in childhood are reflex (vasovagal or neurocardiogenic), although occasionally syncope in children will have a cardiac cause and it is worth knowing the important relevant red flags.

If events are recurrent, differentiating a syncopal from an epileptic cause can cause confusion and misdiagnosis.

Childhood syncope is usually benign but beware of symptoms which could indicate a cardiac cause

Reflex syncope
Reflex syncope can occur throughout childhood. I vividly remember an eight-month old baby having a reflex anoxic seizure when a mobile fell off the ceiling onto the examination couch beside him.

The mechanisms can be vagally mediated, orthostatic, secondary to hyperventilation followed by prolonged expiratory apnoea, or mixed.

Fits, faints and funny turns
In a series of 100 children presenting to our 'Fits, faints and funny turns' clinic specific immediate triggers for syncope were common (77 per cent).

Common triggers were minor injury, including immunisation or blood tests, and orthostatic stresses, for example, standing still, standing from sitting and getting out of bed or the bath.

Less common were thwarted wishes, sudden surprises/shocks, seeing blood, hair care and 'semantic syncope' - that is, in response to a gory story or in one case the word 'testicles'.

About a third of children had more than one trigger.

Symptoms of reflex syncope
Premonitory symptoms include light-headedness, feeling hot and sweaty, nausea and not uncommonly visual disturbance.

Some children will have near syncope (aura without loss of consciousness).

If loss of consciousness occurs, there may be associated loss of tone often with a relatively gradual rather than an abrupt onset ('swoon') but many will have anoxic seizures (tonic posturing and less often clonic or myoclonic jerking).

Post-syncopal symptoms vary from immediate or rapid recovery to combinations of nausea, vomiting, headache, confusion and drowsiness for minutes or hours.

Cardiac syncope
Cardiac syncope is either due to arrhythmia, in prolonged QT syndrome for example, or structural/vascular causes such as hypertrophic obstructive cardiomyopathy (HOCM).

I am not aware of any studies that show a significant difference in the symptoms described by those with cardiac causes versus benign causes of syncope in children. For children who suffer sudden death as a result of HOCM, retrospective assessment will often reveal a prodromal history of syncope.

There are some red flags suggesting cardiac syncope (see box) and children with these should have a paediatric cardiology review.

All children with recurrent syncope or unexplained loss of consciousness should have a standard ECG. The only child I have seen with prolonged QT presented with repeated syncope while riding his bike.

Syncope and epilepsy
When approaching the patient who has had a spell of unknown cause, the most important differential to make is between a syncopal episode and a seizure.

In our series of 380 children presenting with 'funny turns', 100 had syncope and 89 had epilepsy. Both conditions can present with recurrent seizures but the history usually allows confident differentiation, particularly the fact that syncopal anoxic seizures are usually situational or triggered.

Anoxic seizures are often tonic without significant clonic jerking. Features such as tongue biting and incontinence during an event are not reliably discriminatory.

Event EEGs in syncope show flattening whereas in epileptic seizures spike wave activity is the norm. However, nothing is simple; syncope can trigger true epileptic seizures, which can be controlled with antiepileptic medication.

Recurrent faints
Recurrent faints can be intrusive and cause great family anxiety. Pallid or breath-holding syncope in toddlers causes particular concern because the child responds to a minor injury or surprise by losing consciousness and lying pulseless, unresponsive and pale. The doctor makes the diagnosis and explains that these events are due to cardiac asystole, may recur, are not easily treated but are benign and will improve with time.

There is an excellent support group which provides sensible advice on this and other forms of syncope (www.stars.org.uk).

In older children simple measures such as avoidance of triggers, increased fluid and salt intake as well as manoeuvres to stave off loss of consciousness during auras can be helpful. Various pharmacological treatments are available, but are the domain of the paediatric cardiologist after full evaluation.

  • Dr Hindley is a consultant paediatrician in Bolton

Red flags for cardiac syncope

  • Syncope in a child with known congenital heart disease.
  • Syncope during exercise or when supine.
  • Family history of sudden death (especially if <30 years of age), prolonged QT syndrome or HOCM.
  • Syncope preceded by palpitations.
  • Heart murmur or other abnormalities on cardiovascular examination.

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