Background
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.
Clinical
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.
ECG
- 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 |
Alorithm
Management
Cardioversion
- Reserved for patients in shock or CHF
- Initial dose= 0.5-1.0 watt sec/kilogram
Vagal
Infants:
- Diving reflex - Place bag with ice slurry over face for <30 seconds
- Bring knees up to chest
Children:
- 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
Adenosine
- 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
Flecainide
- Only after consultation with paed. cardiologist
- 1-2mg/kg over 20 minutes, need structurally normal heart
Amiodarone
- Only after consultantion with paed. cardiologist
- 5mg/kg over 30 minutes
Esmolol
- Only after consultation with paed. cardiologist
- 0.1mg/kg/minute increasing very gradually to max of 0.5mg/kg/minute