twelve instructive electrocardiograms for the paediatrician

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Twelve instructiveelectrocardiograms for thepaediatricianDarren Hutchinson

Andrew Davis

AbstractPaediatric arrhythmias have diverse presentations and unique features.

Arrhythmia diagnosis depends on knowing the possibilities, examining

the relationship between the P waves and QRS complexes and pattern

recognition. Ten clinical cases together with a dozen instructive electro-

cardiograms are presented to highlight important principles that all

paediatricians should be aware of.

Keywords Belhassen tachycardia; Long QT Syndrome; Paediatric

arrhythmia; Paediatric electrocardiography; Supraventricular tachycardia;

Wolff Parkinson White syndrome

Case 1

Syncope

A 10-year-old boy was brought to the Emergency Department

after fainting whilst sprinting at school. He had been previously

well. The episode was brief and he was immediately alert after

the event. His ECG is shown in Figure 1. His corrected QT

interval is significantly prolonged and after exclusion of

myocardial and electrolyte abnormalities, is diagnostic of Long

QT syndrome. He subsequently proved to have a mutation in

KCNQ1 (Long QT 1).

Long QT syndrome is an important cause of syncope and

sudden death in childhood as the individual is prone to

‘Torsades de Pointes’, a form of ventricular tachycardia which

may deteriorate to ventricular fibrillation. Most long QT

syndromes are caused by mutations in genes that encode the

ion channels of the myocyte. The QT measurement is taken

from the beginning of the q wave to end of the T wave. The end

of the T wave can be determined by drawing a tangent from the

steepest part of the T wave to the baseline. The QT interval is

corrected (QTc) for heart rate by using Bazett’s formula: QTc ¼QT/square root of previous RR interval (both in seconds). The

QTc is normally distributed in the normal population and this

Darren Hutchinson MBBS is in the Department of Cardiology, Royal

Children’s Hospital, Melbourne, Victoria, Australia. Conflict of interests:

none.

Andrew Davis MBBS MD FRACP FCSANZ FHRS is a Department of Cardiology,

Royal Children’s Hospital and Department of Paediatrics, Melbourne,

Victoria, Australia. Conflict of interests: none.

PAEDIATRICS AND CHILD HEALTH 20:12 577

distribution overlaps substantially with the QTc values of the

afflicted population.

Syncope during physical activity is an important ‘warning

bell’ symptom that requires cardiac assessment. In those with

borderline measurements examining the QTc in the recovery

phase of exercise can assist greatly in making the diagnosis. It is

important to make the diagnosis because the untreated mortality

in prolonged QT syndrome after the first syncope is high.

However for most patients, with simple treatments (especially

beta blockade), the outlook is good. After the diagnosis is made,

comprehensive screening of the family including anyone who

may be afflicted is obligatory.

Case 2

Palpitations and dizzy episodes

A 10-year-old girl presents after a 10-min episode of sudden

onset, sudden offset palpitations associated with dizziness and

chest discomfort. Her ECG is shown in Figure 2a. She has Wolff

Parkinson White Syndrome. Figure 2b, from a different patient

has the same diagnosis but the findings are considerably more

subtle and could be missed with a cursory examination of the

ECG.

Case 3

Collapse

A 15-year-old previously well girl collapsed a school whilst

playing sport. She was taken to her local Emergency Department.

She was drowsy, pale and diaphoretic. Her pulse was thready,

fast and irregular.

Her 12-lead ECG is shown in Figure 3. She had an irregular

wide complex tachycardia. The patient was anaesthetised and

a synchronized biphasic DC shock cardioverted her to sinus

rhythm. A repeat 12-lead ECG revealed a short PR interval and

pre-excitation consistent with Wolff Parkinson White syndrome.

Her presenting ECG shows rapid and irregular conduction of

atrial fibrillation down her accessory pathway.

Wolff Parkinson White syndrome results from eccentric

activation of the ventricle via an accessory atrioventricular

connection. This results in the pre-excitation pattern seen in

sinus rhythm. The pathway is the substrate for supraventric-

ular tachycardia that usually travels down the AV node and

retrograde up the accessory pathway causing symptoms as in

case 2.

Rarely, but importantly, supraventricular tachycardia may

beget atrial fibrillation as in case 3. A small percentage of path-

ways can conduct atrial fibrillation very rapidly which can lead

to ventricular fibrillation and sudden death. The presence of

subtle pre-excitation as in Figure 2b does not preclude the

pathway being dangerous. Assessment by or in conjunction with

a paediatric electrophysiologist is warranted. Ablation is usually

indicated in symptomatic children, once they have reached an

appropriate size. Anti-arrhythmic drugs are used in the interim.

Controversy remains regarding the management of children who

have incidentally been found to have pre-excitation. Sudden and

definitive loss of pre-excitation on exercise testing usually

implies the pathway is unlikely to be dangerous. Electrophysi-

ology study can, to an extent, risk stratify those patients with

rapidly conduction accessory pathways.

Crown Copyright � 2010 Published by Elsevier Ltd. All rights reserved.

http://dx.doi.org/10.1016/j.paed.2010.08.001

Figure 2 a The ECG shows sinus rhythm with pre-excitation. The PR interval is short with delta waves, a widened QRS complex and abnormal repolar-

ization consistent with Wolff Parkinson White Syndrome. b This ECG also shows pre-excitation but its presence is much more subtle. A good clue to the

presence of pre-excitation is the absence of a q wave in lead V6 or V7. The normal septal q wave is a manifestation of normal septal activation from left to

right, which may be perturbed when pre-excitation is present.

Figure 1 The ECG shows sinus rhythm with a prolonged QT interval. The corrected QT interval in lead II is 0.53 s.

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PAEDIATRICS AND CHILD HEALTH 20:12 578 Crown Copyright � 2010 Published by Elsevier Ltd. All rights reserved.


Figure 3 Irregular wide complex tachycardia from extremely rapidly conducted pre-excited atrial fibrillation in a child with WPW syndrome. The differential

diagnosis includes ventricular tachycardia.

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Case 4

Unwell neonate

A 2-week girl presented to the emergency department pale,

breathless and refusing feeds. A tachycardia was noted

(Figure 4). She has supraventricular tachycardia with obvious

retrograde P waves. Adenosine was administered converting the

babe to sinus rhythm. No pre-excitation was present.

The ECG is consistent with supraventricular tachycardia.

The mechanism is the same as in Wolff Parkinson White

syndrome however the pathway in this case was only unidi-

rectional and does not conduct downwards in sinus rhythm, so

the interval ECG was normal. The likelihood of recurrence is

high; many patients are successfully treated with beta-blockers

with more complex anti-arrhythmic medications usually

reserved for treatment failures. There is a good chance of

spontaneous cure.

Figure 4 Regular narrow complex tachycardia with clearly seen retrograde P w


Case 5

Screening ECG

A 4-day-old infant with Trisomy 21 had a screening ECG per-

formed (Figure 5). The automated report read: ‘Sinus rhythm.

Right axis deviation. Consider anterior ischaemia. Abnormal

ECG’. The ECG however is normal for age.

The ECG of the newborn is very different to that of an adult in

a number of ways and will progressively change from newborn

to childhood to adolescence and then adulthood. Automated ECG

reports may not have paediatric algorithms or the algorithm is

not used if the date of birth is not entered; the ECG is then

reported as if the patient is an adult resulting in confusion. The

average heart rate of a newborn infant is approximately 125 bpm.

This will peak at around 1e2months of age when the average

heart rate is approximately 150 bpm. The overall vector of the

QRS complex in the frontal plane is much more rightward in the

aves.



Figure 5 Normal ECG for a day 4 newborn.

Figure 6 Atrial ectopic tachycardia with Wenckebach atrioventricular conduction. The P waves have an abnormal morphology. Arrows indicate P waves.

Figure 7 Long RP tachycardia with inverted P wave inferiorly. Chest lead Voltages are large consistent with biventricular hypertrophy. Diagnosis was the

persistent form of junctional reentry tachycardia (‘PJRT’).

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PAEDIATRICS AND CHILD HEALTH 20:12 580 Crown Copyright � 2010 Published by Elsevier Ltd. All rights reserved.


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newborn. This is normal for age and should not be described as

right axis deviation. The mean QRS vector in a newborn infant is

approximately þ135 degrees. This compares to þ60 degrees in

a 15-year-old.

T wave evolution throughout childhood is important. It is

normal for an infant to have inverted T waves in the right pre-

cordium after the first week of life. The inverted T waves may

progress throughout childhood with T inversion from V1 up to

Figure 8 a Ventricular tachycardia followed by probable sinus rhythm with first

some premature beats. b Sinus rhythm, right axis deviation and a wide QRS co

QRS complex has a ‘Brugada’ like morphology.


V4 being accepted as normal. There is progressive change from

inverted to upright T waves across the precordial leads from left

to right with growth. In the majority of children, all T waves in

the precordial leads will be upright by 8 years of age excluding

V1. Persistence of an inverted T wave in lead V1 until late teens

in common. Importantly an upright T wave in V1 prior to 8 years

and after 8 days of age likely indicates right ventricular

hypertrophy.

degree atrioventricular block, with a right bundle branch block pattern and

mplex that is alternating every second beat. In lead V1 the first and third



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Whilst ECG screening for congenital heart disease in Trisomy

21 is highly specific it is not sensitive enough to be of value and

echocardiography is indicated in all infants with Trisomy 21

because of the high incidence of associated congenital heart

disease.

Case 6

Lethargy and malaise

A 6-year-old boy sees a paediatrician for lethargy and malaise

and a baseline tachycardia with irregularity is noted. An ECG is

performed (Figure 6).

Atrial ectopic tachycardia (also called focal atrial tachycardia)

originates in the either atrium from a focus other than the sinus

node. The P waves usually have an abnormal axis. The tachy-

cardia has an ‘automatic’ basis and often has wide variation in

rate (‘warm up’ e ‘cool down’). There may be varying degrees of

atrioventricular block. The essential feature of Wenckebach

conduction is that the pre-block PR interval is longer than the

post block PR interval as above. Sometimes the incessant

tachycardia ‘tires’ the heart and causes a tachycardia-induced

cardiomyopathy, which usually resolves with control of the

arrhythmia. Children less than 3 years of age usually respond

well to anti-arrhythmic therapy with a good chance of resolution,

whereas those greater than three are less likely to resolve. Atrial

ectopic tachycardia is amenable to catheter ablation.

Case 7

Shortness of breath

A 2-year-old boy came to the emergency Department because of

laboured breathing. He had clinical evidence of cardiac failure

and a baseline tachycardia between 130e150 bpm. His ECG is

shown in Figure 7.

Whilst not diagnostic, this ECG is typical for the so-called

‘permanent form of junctional reciprocating tachycardia’ (‘PJRT’).

ThePwaveshaveanabnormalaxisandare inverted in leads II, III and

Figure 9 Complete atrioventricular block. The atrial rate is 125/min. The ventr

a ventricular, rather than a junctional escape mechanism.


aVF. The differential diagnosis is atrial ectopic tachycardia arising

from the low right atrium. The distinction can sometimes bemade on

Holter monitoring or may require electrophysiology study. The

tachycardia involves retrograde conduction from the ventricles via

a slowly conducting accessory pathway usually located near the

mouth of the coronary sinus. This makes the R to P interval long.

The retrograde P wave is then conducted down the AV node to the

ventricle and the cycle can commence again. The label ‘PJRT’ is

amisnomerbecause theoriginal predictedmechanismwas incorrect.

As ‘PJRT’ is often incessant the result can be a tachycardia-induced

cardiomyopathy. ‘PJRT’ is difficult to treat with anti-arrhythmic

medication but may resolve spontaneously. It can be cured with

ablation of the pathway. After rate control or ablation ventricular

function can usually be expected to return to normal.

Case 8

Seizure

A 3-year-old girl was taken to a local hospital via ambulance after

a seizure at home. There was no significant past history and no

known history of drug ingestion. She was lapsing in and out of

consciousness. Her presenting ECG is shown in Figure 8a. It

shows ventricular tachycardia and then probable sinus rhythm

with first degree atrioventricular block, a broad QRS complex with

a right bundle branch block pattern and some premature beats.

After intubation a second ECG was obtained (Figure 8b). It

shows sinus rhythm, right axis deviation and a wide QRS complex

that is alternating every second beat. In lead V1 the first and third

QRS complex has a ‘Brugada’ like morphology with ST elevation.

Brugada syndrome is a genetic condition that can predispose

to life threatening ventricular arrhythmias. Typically there is

a right bundle branch pattern in the anterior precordial leads

together with ST elevation. This pattern may be only present

intermittently. Differential diagnosis of this pattern includes

pericarditis, myocardial ischaemia or infarction, mediastinal

tumour, arrhythmogenic right ventricular dysplasia and over-

dose of tricyclic antidepressants. Close questioning of the family

icular escape rate is 50/min. The QRS complex is wide; indicating



Figure 10 Belhassen’s ventricular tachycardia. Wide complex (but relatively narrow) tachycardia with a leftward axis and a right bundle branch block.

Arrows on lead V3 indicate P waves. There is ventriculo-atrial dissociation with the ventricular rate being faster than the atrial rate. Arrows show P waves.

OCCASIONAL REVIEW

revealed her grandmother who lived in the house was taking

tricyclic antidepressants and drug screen revealed a high blood

level of the same. After a period of intensive care she made an

uneventful recovery.

Case 9

Incidental bradycardia

A5-year-old boywho is admitted to hospital after fracturing his arm

after a fall from his bike. Routine observations note heart rate of

approximately50bpm.Observationsareotherwisenormal.AnECG

was performed showing complete atrioventricular block (Figure 9).

In retrospect his parents commented that he is more tired of an

evening than his brothers and that he sleeps poorly. His asymp-

tomatic mother was positive for anti-Ro/SSA antibodies and it was

presumed he had undiagnosed congenital atrioventricular block.

Congenital heart block is most commonly associated with

lupus maternal antibodies, especially anti-Ro/SSA or anti-La/

SSB, which can cross the placenta. Other causes of later pre-

senting congenital heart block include structural heart defects,

especially congenitally corrected transposition of the great

arteries. Detailed, evidence based indications for pacing are

published and include for paediatric atrioventricular block;

symptomatic bradycardia, wide complex escape rhythm, long QT

interval and ventricular rate in an infant less than 55 bpm. It is

now widely accepted that all patients with congenital heart block

should be paced by their teenage years.

Case 10

Palpitations and pre-syncope

A 9-year-old boy had sudden onset of palpitations and pre-

syncope whilst sitting in math class. He was transferred to the


closest Emergency Department. His ECG is shown in Figure 10.

The diagnosis of supraventricular tachycardia was made,

however adenosine was given but failed to revert him to sinus

rhythm. After the diagnosis was appreciated he was reverted to

sinus rhythm using intravenous verapamil.

Belhassen’s ventricular tachycardia is a relatively narrow

complex (but still broad complex), with features that include

a right bundle branch block/left axis deviation morphology and

verapamil sensitivity. As it is relatively narrow complex it is

frequently confused with supraventricular tachycardia. It is also

known as posterior fascicular ventricular tachycardia as its origin

is reentry within that region of the left bundle branch. The

tachycardia is amenable to catheter ablation. A

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twelve instructive electrocardiograms for the paediatrician

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