Definition
- Cardiac arrhythmias comprise a spectrum of variations to normal heartbeat.
- Normal rhythm variations
- A wide range of normal heart rates is present in young persons.
- Premature (early) beats
- Usually benign arrhythmias that occur as:
- Premature atrial contractions (PACs)
- Premature ventricular contractions (PVCs)
- Couplet
- 2 premature beats in a row
- Bigeminal or trigeminal rhythm
- Every second or third beat is a premature impulse.
- Supraventricular tachycardia (SVT)
- Tachycardia with origin above the ventricles
- Atrial flutter
- Primary atrial reentrant tachycardia
- Atypical form (intraatrial reentrant tachycardia)
- Atrial fibrillation
- Irregular tachycardia with variable atrioventricular conduction
- Types
- Lone (idiopathic, no underlying cause)
- Underlying heart disease
- Ventricular tachycardia (VT)
- ≥ 3 repetitive excitations arising from the ventricles
- Conduction abnormalities
- First-degree atrioventricular (AV) block
- Second-degree AV block
- Wenckebach block or Mobitz type I
- Mobitz type II
- Complete AV block
- Sudden cardiac death
Epidemiology
- Prevalence
- PACs
- Seen in 50–75% of pediatric patients
- PVCs
- Less common than PACs
- On Holter monitoring, seen in up to 25% of healthy infants, children, and adolescents
- SVT
- Up to 1 in 250 children
- Reentrant: > 90% of pediatric SVT
- Automatic: < 10% of pediatric SVT
- Wolff-Parkinson-White (WPW) syndrome:
- 0.15% in the general population with or without SVT
- Atrial flutter
- Bimodal distribution in newborn infants and in older children
- Atrial fibrillation
- Less common than other arrhythmias
- Incidence in adolescence may be underestimated.
- VT
- Rare in the newborn and young infant
- Sudden cardiac death
- 1:100,000
- Beyond infancy, 25% of sudden deaths in the young occur during exercise.
- Long QT syndrome (LQTS)
- 10:100,000
- May be underestimated because of incomplete genetic ascertainment
- Age
- Arrhythmias in the young are common.
- Usually benign
- May be life-altering or fatal
- Arrhythmias may begin at any age.
- In utero up to the later teenage years
- Higher incidence in early infancy and mid-adolescence
- Sudden cardiac death
- Most common in mid-adolescence
- Sex
Mechanism
- Premature beats
- May arise in the atria, the AV junction, or the ventricles
- SVT
- Early infancy
- Usually initiated by PAC or sinus tachycardia
- AV reentry tachycardia through an accessory pathway (preexcitation)
- Childhood and adolescence
- PVCs and sinus pauses with junctional escape beats are additional initiators.
- AV nodal reentry tachycardia using the fast and slow pathways in the AV nodal region
- Primary atrial tachycardias
- Automatic SVT
- Atrial flutter
- Atrial fibrillation
- Conduction abnormalities
- Second-degree AV block
- Type I
- Predominance of vagal tone
- Block is in the AV node.
- Type II
- Block is more distally located in the bundle of His.
- Complete AV block
- Acquired
- Usually results from conduction system injury
- Congenital complete atrioventricular block (CCAVB)
- Fetus exposed to antibodies in a mother with autoimmune disease between 15 and 24 weeks of gestation
- Sudden cardiac death
- Ion channel cardiac disorder that prolongs repolarization
- Genetic basis
- Romano-Ward form (95% of patients)
- Jervell and Lange-Nielsen syndrome (5%)
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