Supraventricular Tachycardia ( SVT ) in Children


Common in infants. May be first presentation of WPW.

AVRT (AV reciprocating tachycardia) is the most common form in infancy – accessory pathway.

AVNRT is rare in infancy but increases in incidence during adolescence.


May present with

  • Increased crying
  • Poor perfusion, eg pallor, lethargy, increased capillary refill time
  • Poor feeding

Older child:

  • Light-headedness
  • Palpitations

Short paroxysms are rarely a danger to life, however if the attack lasts >24 hours heart failure may develop.


  • Beat varies widely (cf adults)
  • Up to 300 / min (infants), 160 older children
  • QRS narrow
  • Assume wide complex = VT
  • Sinus < 220 beats/minute
  • Variable rate in SVT
  • SVT responds to vagal / adenosine
  • P wave is visible in 50-60% cases of SVT. May be abnormal p wave axis. Short QRS (<0.08sec)

SVT vs Sinus Tachycardia

Sinus tachycardia SVT
Rate <200 >220
Beat to beat variability Yes No
P wave axis Normal Normal/abnormal + retrograde
Associated symptoms Hx/signs of sepsis, history of fluid depletion eg diarrhoea/vomiting Poor feeding, pallor, lethargy
Response to treatment Gradual Abrupt response to vagal/adenosine




  • Reserved for patients in shock or CHF
  • Initial dose= 0.5-1.0 watt sec/kilogram



  • Diving reflex - Place bag with ice slurry over face for <30 seconds
  • Bring knees up to chest


  • Place face in bucket with ice water for as long as able
  • Push out tummy, with legs in the air while the examiner exerts firm pressure
  • Blows through syringe while legs are in the air
  • Hand stand if able


  • Drug of choice
  • Initial dose= 0.1 mg/kg, may be doubled

If Adenosine Fails To Convert:

  • 12 lead ECG to re-evaluate rhythm (? sinus)
  • Consider cardioversion for SVT


  • Only after consultation with paed. cardiologist
  • 1-2mg/kg over 20 minutes, need structurally normal heart


  • Only after consultantion with paed. cardiologist
  • 5mg/kg over 30 minutes


  • Only after consultation with paed. cardiologist
  • 0.1mg/kg/minute increasing very gradually to max of 0.5mg/kg/minute

Content by Dr Rory O'Brien, Dr Dr Íomhar O' Sullivan 25/02/2020. Last review Dr ÍOS 31/08/22.