What are the causes of tachycardia in children?

Causes of Tachycardia in Children

Tachycardia in children has distinct etiologies that vary by age and clinical context, with supraventricular tachycardia (SVT) being the most common pathologic arrhythmia requiring treatment, while sinus tachycardia from physiologic stressors remains the most frequent overall cause. 1, 2

Primary Classification Framework

Tachycardia in pediatric patients must first be categorized by QRS duration to guide diagnosis and management:

Narrow-Complex Tachycardia (QRS ≤0.08-0.09 seconds)

Sinus Tachycardia - The most common cause overall 1

• Physiologic triggers: Fever, infection, pain, dehydration, anemia, hyperthyroidism 3
• Cardiac causes: Myocarditis, heart failure 3
• Distinguished from SVT by gradual onset/offset, rate variability, and identifiable precipitant 1

Supraventricular Tachycardia (SVT) - Most common pathologic arrhythmia 2, 4, 5

• Atrioventricular reentry tachycardia (AVRT): Dominant form in first year of life, involves accessory pathways (Wolff-Parkinson-White syndrome) 2, 6
• Atrioventricular nodal reentry tachycardia (AVNRT): Becomes more common during adolescence 2, 6
• Ectopic atrial tachycardia: More frequent in infants 6
• Atrial flutter: Can occur in infants and after cardiac surgery 6
• Heart rate typically exceeds 220 bpm in infants and 180 bpm in older children 5

Wide-Complex Tachycardia (QRS >0.08-0.09 seconds)

Ventricular Tachycardia 1

• Associated with underlying structural heart disease, particularly post-surgical patients (tetralogy of Fallot, ventricular septal defect repair) 1
• Catecholaminergic polymorphic ventricular tachycardia: Presents with exercise-induced syncope 1

SVT with Aberrant Conduction 1, 7

• Supraventricular rhythm conducted with bundle branch block pattern

Age-Specific Considerations

Neonates and Infants (0-12 months):

• AVRT predominates as the SVT mechanism 2, 6
• Present with signs of congestive heart failure rather than palpitations 4, 6
• Maternal autoimmune disease (SLE, Sjögren's syndrome): Anti-Ro/SSA and anti-La/SSB antibodies can cause both tachyarrhythmias and bradyarrhythmias with poor prognosis, especially with hydrops fetalis 8, 9
• Normal sinus rates: 91-166 bpm in first week, up to 182 bpm by one month 3
• Transient rates up to 230 bpm during distress are physiologic 3

School-Age Children and Adolescents:

• AVNRT becomes increasingly common 2, 6
• Palpitations become the primary presenting symptom 4, 6
• Hypertrophic cardiomyopathy: Most common cause of sudden cardiac death in adolescents; syncope with exercise is an ominous sign 1

Underlying Cardiac Disease

When structural heart disease is present, tachycardia becomes potentially life-threatening 1:

• Post-surgical congenital heart disease: Intra-atrial reentry tachycardia from atrial scarring; ventricular tachycardia from ventricular surgery 1, 6
• Aortic stenosis: Exercise-induced syncope indicates critical obstruction 1
• Primary pulmonary hypertension: Syncope frequently observed 1
• Idiopathic dilated cardiomyopathy: Near-syncope or syncope as presenting symptom in 13% 1
• Coronary artery anomalies: Present in ~1% of population; syncope or sudden death may be first manifestation when anomalous coronary courses between aorta and pulmonary trunk 1

Genetic/Channelopathy Causes

• Long QT syndrome (LQTS): Polymorphic ventricular tachycardia (torsades de pointes) triggered by exercise, emotion, or auditory stimuli 1
• Brugada syndrome: ST elevation in V1-V2 with susceptibility to polymorphic ventricular tachycardia; 30% two-year sudden death risk with syncope 1
• Catecholaminergic polymorphic VT: Exercise-induced presentation 1

Non-Cardiac Causes

• Drug ingestion: Can cause both tachycardia and bradycardia 1
• Anorexia nervosa: Cardiac manifestations include arrhythmias 1
• Central nervous system trauma: Can affect heart rate regulation 1
• Hyperthyroidism: Causes sinus tachycardia 3

Critical Clinical Pitfalls

• Chronic-permanent tachycardia causes dilated cardiomyopathy - any persistent tachycardia requires aggressive management 4
• Infants with SVT require treatment due to difficulty recognizing symptoms and heart failure risk, even if asymptomatic 4, 6
• Syncope with tachycardia indicates severe hemodynamic compromise from extremely rapid rates and warrants urgent evaluation 6
• Patients with Wolff-Parkinson-White syndrome are at sudden death risk and require definitive management 6
• Wide-complex tachycardia should be treated as ventricular tachycardia until proven otherwise in the emergency setting 1
• Consultation with pediatric arrhythmia expert strongly recommended for hemodynamically stable patients before initiating therapy due to potential for serious adverse effects 1

Prognosis by Age of Onset

• SVT starting in first months of life: Disappears in 80% by first year 2
• SVT starting after infancy: Spontaneous remission only 15-20% 2
• This distinction guides decisions about long-term prophylactic therapy versus observation 2, 4