Synopsis
Distinguish paediatric supraventricular tachycardia from sinus tachycardia, recognise infant shock and tachycardia-induced failure, and use monitored vagal manoeuvres, adenosine and synchronised cardioversion with exact weight-based escalation.
- Paediatric SVT is usually a re-entry rhythm above the ventricles, commonly atrioventricular re-entry through an accessory pathway in infancy or AV nodal re-entry in older children.
- Typical SVT is abrupt, very regular and narrow complex with little beat-to-beat variability; rates are often above 220/min in infants and 180/min in children, but rhythm features matter more than one cutoff.
- Sinus tachycardia varies with temperature, distress and breathing and usually has visible normal P waves; treat fever, pain, hypovolaemia, sepsis or hypoxia rather than repeatedly giving adenosine.
- Initial assessment is ABC, perfusion and consciousness, continuous ECG, a rhythm strip and 12-lead ECG during tachycardia if this does not delay treatment, plus proximal IV access and electrolytes.
- In a stable child, try an age-appropriate vagal manoeuvre while preparing adenosine: cold-face diving-reflex stimulation for an infant or a coached Valsalva for an older child. Never use ocular pressure.
- Give adenosine through the largest feasible proximal vein as an immediate rapid bolus followed by a rapid saline flush with a continuous printed rhythm strip.
- Current BWC sequence is 100 micrograms/kg, maximum 6 mg; after 2 minutes 200 micrograms/kg, maximum 12 mg; after another 2 minutes 300 micrograms/kg, maximum 12 mg.
- In shock, synchronised cardioversion is the priority at 1 J/kg then 2 J/kg. Seek expert advice for 4 J/kg and refractory treatment; do not delay shock for repeated cannulation or sedation.
- Check potassium, ionised calcium and magnesium and treat fever, hypoxia and acidosis. A cautious 5 mL/kg fluid aliquot may be used for hypotension only with reassessment because ventricular function may be impaired.
- Adenosine briefly blocks the AV node: it terminates AV-node-dependent re-entry, may reveal atrial flutter, and will not reliably treat automatic atrial tachycardia or ventricular tachycardia.
- After conversion, obtain a 12-lead ECG for pre-excitation, monitor for recurrence, assess ventricular function after prolonged episodes and arrange paediatric cardiology follow-up for prevention or ablation planning.
Key red flags
Poor feeding, pallor, tachypnoea, irritability, hepatomegaly or lethargy in an infant with a fixed very rapid pulse may be SVT with developing heart failure.
Hypotension, altered consciousness, weak pulses, prolonged refill, gallop, acidosis or pulmonary oedema makes immediate synchronised cardioversion the priority.
An irregular or broad-complex tachycardia, pre-excited atrial fibrillation or uncertain rhythm must not receive routine AV-nodal treatment as though it were simple narrow SVT.
Adenosine that has no transient AV-block effect may have been delivered too slowly or too distally, or the dose, diagnosis or interacting medicines may be wrong.
Recurrent syncope, ventricular dysfunction, congenital heart disease, previous cardiac surgery or a family history of sudden death requires expedited electrophysiology assessment.
A neonate or young infant with fever or poor perfusion still needs infection, myocarditis, hypoxia and metabolic causes assessed even when SVT is documented.
Investigation priorities
Document rate, regularity, QRS width and response during treatment.
Management branches
Regular narrow SVT is present without circulatory compromise.
- Attach continuous ECG and pads, obtain a proximal IV and try monitored cold-face stimulation or a coached Valsalva.
- Give adenosine 100 micrograms/kg rapid IV, maximum 6 mg, with an immediate flush while printing the rhythm.
- At 2-minute intervals escalate to 200 then 300 micrograms/kg, each maximum 12 mg, and seek cardiology advice if SVT persists.