A worried couple bring in their 7 yr old boy (Tom) to your ED after he suddenly lost consciousness at the school athletics carnival.
Fainting or loss of consciousness can be an understandable cause for alarm for parents, especially in those with no family history or experience with fainting.
A detailed history is the most diagnostic part of syncope assessment
Vasovagal syncope is by far the most common cause in paediatrics
A baseline ECG can help rule out rare but deadly causes of arrhythmia
They had just seen him run in the 200m final before lunch, and five minutes later he was lining up for food and fell to the ground. He was initially unresponsive but came to after what seemed like a long time. He then collapsed again within a few minutes on the way to the car. An ambulance was called, and by the time QAS arrived, he was awake but feeling very tired.
This is the first time this has happened to Tom, who is an only child and is usually quite a fit and active boy. His mother and father do not have a fainting history and there is no history of congenital heart disease known in the extended family. Tom’s maternal grandfather died at 38 in a car accident.
What is syncope?
Syncope is a sudden and transient loss of consciousness with a loss of postural tone from which recovery is spontaneous and complete.
15% of children will experience a syncopal event, most of which will be benign.
It is a very common presentation to ED and has a huge list of differentials.
Our role is to detect the rare fatal or pathological syncope whilst avoiding over-investigating the benign.
How is syncope classified?
Syncope can be classified into three main groups
- Neurally–mediated – most common
- Cardiovascular causes – potentially fatal
- Other – epilepsy and psychogenic
Neurally-mediated syncope is a heterogenous group of autonomic disorders causing orthostatic intolerance. It peaks in toddlers and adolescents.
There are two main groups – reflex and Postural Orthostatic Tachycardia Syndrome (or autonomic failure). In this post, we will discuss reflex syncope.
What is reflex syncope?
Reflex syncope is a sudden failure of the autonomic nervous system to maintain vascular tone during orthostatic stress.
There is hypotension and bradycardia; along with cerebral hypoperfusion and loss of consciousness. An individual may have an event characterised by a primary vasodepressor, cardioinhibitory, or a mixed response.
In reflex syncope there is a clear provoking factor.
Vasovagal syncope is the most common type of reflex syncope in children, but what exactly is it?
This is a benign reflex event. There is depression of sympathetic vasomotor tone (‘vaso’) with associated parasympathetic mediated bradycardia (‘vagal’).
In vasovagal syncope, there is clear provocation – tiredness, hunger, heat, dehydration
Often there is a prodromal sensation with short-lasting loss of consciousness and quick complete recovery.
So, what are reflex anoxic seizures?
There are non-epileptic paroxysmal events in infants and preschool-aged children provoked by pain or surprise. 8 in 1000 pre-schoolers are affected.
Sudden vagal excitation following the trigger leads to a short period of asystole.
A better term to use is reflex asystolic syncope. This describes the event exactly and removes the confusion by using the word seizure – this is not a seizure.
Asystole! That sounds awful…
The classic presentation of reflex asystolic syncope is:
- A sudden and distressing stimulus such as injury or shock – the child is described as deathly pale and lifeless.
- A period of asystole that typically lasts 5 – 30 seconds.
- Can have a brief convulsive phase.
- The child comes around confused and distressed.
The convulsive phase may be dystonic posturing with asymmetrical or symmetrical jerking and occasionally incontinence which can increase diagnostic confusion for the physician. There may even be a short post-ictal phase. This diagnosis falls in the hinterland between neurology and cardiology. It is generally managed by a general paediatrician.
History is vital in diagnosing this. Clues include provocation, deathly white, and then collapse. Ask the family if this happened before – note that recurrent attacks may have no provocation but a previous episode will help give clues.
Cardiac syncope is extremely rare but can be 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 avoidable. 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.
How do SADS conditions present to the ED?
- Cardiac arrest
A retrospective study at RCH, Melbourne 2012 showed that syncope was the leading cause for the presentation of the 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 and 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)*
- Congenital heart disease (abnormal valves, chambers, or anomalous coronary arteries, from birth)
- Re-entrant tachycardias
- Long / short QT Syndrome (natural or iatrogenic)
- CPVT (Catecholaminergic Polymorphic Ventricular Tachycardia)
The ECG in syncope
Although cardiac syncope is rare, it is potentially fatal. It is, therefore, essential that we know how to recognise ECGs that identify the cause of cardiac syncope.
Hypertrophic obstructive cardiomyopathy
HOCM is the leading cause of SADS in young athletes. It involves myocardial hypertrophy of the nondilated left ventricle. There is impaired filling, especially at times of stress with electrical disruption and variable outflow obstruction.
HOCM is worse on exercise. 55% have a family history
High left ventricular voltage with associated ST segment / T-wave abnormalities
Deep, narrow (“dagger-like”) Q waves in the lateral(I aVL V5 V6) > inferior leads – not had a previous lateral MI and not in LVH – not sensitive but is specific
Left atrial enlargement – bifid p waves
Arrhythmogenic right ventricular cardiomyopathy
AKA arrhythmogenic right ventricular dysplasia (ARVD)
AVRC was first described in 1978 and has an autosomal dominant inheritance.
Fibrofatty replacement of the right ventricle leads to a dilated and hypokinetic right ventricle and, if undetected, death. It is the second most common cause of SADS. Patients have palpitations, syncope and cardiac arrest.
The ECG is difficult to interpret.
Epsilon wave (most specific finding, seen in 30% of patients) – notch at end of QRS complex
T wave inversions in V1-3 (85% of patients)
Prolonged S-wave upstroke V1-3 (95% of patients)
Localised QRS widening of 110ms in V1-3
Sinus rhythm with a very short PR interval
Broad QRS complexes with a slurred upstroke to the QRS complex — the delta wave
Tall R waves and inverted T waves in V1-3 mimicking right ventricular hypertrophy — these changes are due to WPW and do not indicate underlying RVH
Negative delta wave in aVL simulating the Q waves of lateral infarction — this is referred to as the “pseudo-infarction” pattern
This is autosomal dominant with variable penetrance and is a sodium channelopathy. There is an association with long QT syndrome. It more commonly presents with VF, but syncope is well documented.
1. Adult study of 104 symptomatic patients with ECG changes: 73% VF, 27% syncope
2. 30 adult patients with ECG changes: 44% syncope, 56% arrest of which 82% had a history of syncope
There are various ECG patterns:
Coved ST-segment elevation >2mm in >1 of V1-V3 followed by a negative T wave) is the only ECG abnormality that is potentially diagnostic.
This above ECG sign is referred to as the Brugada sign.
Brugada type 2 – >2mm of saddleback-shaped ST elevation
Brugada type 3 can be the morphology of either type 1 or type 2, but with <2mm of ST-segment elevation.
As we can see, there are several variations of Brugada.
Consider Brugada if there are any ST abnormalities in V1-3 in a younger patient
It can look like right bundle branch block
ECG changes may be intermittent
These days, most ECG machines calculate this for us, but you should know how to calculate this (QT interval divided by the square root of the R-R interval).
Pediatric Electrophysiology Society Study (published in American Heart Association in 1993) describes presenting clinical features of LQTS in 287 patients from 26 centres < 21 years of age, with either documented LQTc or a family history of long QTc or a family history of unexplained syncope/seizures/cardiac arrest.
- Mean age presentation 6.8 years
- 61% symptomatic at presentation
- 26% syncope
- 10% seizures (misdiagnosed)
- Only 9% with cardiac arrest
Of the 61% with symptoms
- 67% with exercise
- 18% with emotion and exercise
- Family history positive for long QT in 39% and for sudden death in 31%
Catecholaminergic Polymorphic Ventricular Tachycardia (CPTV)
- Mean age of presentation 6 – 10 years
- Provoked by a surge in adrenaline
- Present with exercise or emotion-induced syncope or cardiac arrest
- Had a “fit” when woken by the alarm clock
- Often went dizzy and lightheaded watching a scary movie
- Clinical diagnosis based on history around exercise/emotion-induced symptoms
- Mean age of syncope 7.8 years
- Mean age of diagnosis 9.9 years
- 50% of the cases had initially been misdiagnosed as epilepsy and treated accordingly
So, with syncope, there should be the normal ECG interpretation process but with pattern recognition awareness:
WPW delta wave
High left ventricular voltage and Q waves
Other causes of syncope to consider
This is often a continuity from early childhood reflex asystolic syncope (although not necessarily) which extends into adulthood. The mean age of onset is 7 years.
The sight of blood leads to a reflex transient tachycardia, bradycardia and eventual brief asystolic period.
There is a strong family history of both reflex asystolic syncope and blood injury phobia.
Breath holding attacks
There is also a crossover here with reflex asystolic syncope and a similar presentation.
Sudden increased intrathoracic pressure impedes venous return to the heart and thus decreases the cardiac output (essentially a Valsalva manoeuvre).
Typical history: child crying, silence, blue, syncope. History is vital.
Is syncope easily confused with seizures?
It is a common misdiagnosis.
Any syncope can cause limb jerks and often present to ED as a ‘seizure’.
The wrong diagnosis has consequences:
- Unnecessary investigations and specialist referral
- Medication and restrictions to life
- The underlying risk of arrhythmic death missed
And finally….what is POTS?
Postural Orthostatic Tachycardia Syndrome (POTS) is a disorder of the autonomic nervous system. It is defined as a sustained increase in HR > 40bpm in the 12–19 year age group, within 10 mins of standing associated with symptoms of orthostatic intolerance.
- No postural BP drop
It is poorly understood.
The pathophysiology is that the patient goes from lying to sitting, and >300mls blood is redistributed from the thoracic cavity to the limbs in a few secs. There is a compensatory baroreceptor reflex to maintain cerebral perfusion. This causes increased HR, contractile force and peripheral vasoconstriction.
Dysautonomia is a failure of vasoconstriction -> increased compensation of the other components of the triad. Inadequate compensation -> pounding palpations syncope.
How does POTS present?
It often presents following a viral illness, immunisation, stressors such as sepsis, surgery, or growth spurt. It is exacerbated by extremes of temperature, exercise, meals and menstruation.
Typical symptoms: palpitations with fatigue presyncope sensation, difficulty performing exercise,(note symptoms not during exercise necessarily but preventing from participating), tremulousness, weakness, and loss of concentration often described as brain fog and syncope.
Others: chest wall pain, shortness of breath, anorexia and GI upset, – IBS misdiagnosed, headaches – misdiagnosed migraines, occipital shoulder coathanger headaches, pain, sleep difficulty, anxiety and panic attacks.
It can be secondary to other conditions – the most common being joint hypermobility syndrome/Ehlers Danlos hypermobility.
What are the investigations for POTS?
- ECG and echo – differential of tachycardia
- 24-hour Holter
- Baseline bloods (including ferritin, which is often deficient)
- TFT and adrenal axis
- 24-hour urinary catecholamines – pheochromocytoma – symptoms more common when lying down
- 24-hour urinary sodium – evidence of sufficient fluid and sodium intake and thus likely normal plasma volume
- Head upright tilt test (HUTT) – baseline BP and HR when supine, inclined to 70-degree head-up angle with continuous BP and HR measurements
- Active stand test – requires skeletal muscle pump and mimics real life
- Autonomic function test
Both HUTT and the active stand test are sensitive for a diagnosis of POTS with a 30bpm threshold for orthostatic tachycardia AST > specific (79% : 23%)
How do we treat POTS?
- Withdrawal of medications (unlikely in children)
- Treat associated conditions
- 2 -3 litres of water per day
- Adequate salt intake
- Compression stockings; pumping calves before rising and rising slowly; exercise to build up skeletal muscle pump
- Bedhead elevation
- Counter-manoeuvres before rising
- Encourage exercise
- Pharmacological treatment – beta-blockers (alpha and beta blocking effects), clonidine (alpha 2 agonist inhibits SNS – low BP), fludrocortisone (increased sodium retention to expand plasma volume), midodrine (alpha 1 agonist – vasoconstrictor), octreotide (refractory – vasoconstrictor)