Clinical Practice Guidelines

Supraventricular Tachycardia SVT

  • Assessment


    • Infants - pallor, dyspnoea, poor feeding.
    • Older children - palpitations , chest discomfort


    • Regular tachycardia - HR usually 180-300/min
    • Hypotension may be present.
    • Heart failure, especially infants.


    12 lead ECG showing regular narrow complex tachycardia.


    Consult cardiology urgently if tachycardia is broad complex or irregular.


    • Monitor with continuous ECG trace and frequent measurements of blood pressure
    • If necessary apply oxygen 10 litres / min by face mask
    • If child is shocked (ie. hypotensive, poor peripheral perfusion, impaired mental state) proceed to direct current cardioversion (see below)
    • If child is not shocked treat with intravenous adenosine

    Shocked Child - Direct Current Cardioversion

    • Call ICU. Ensure experienced staff and full resuscitative measures are present
    • Ensure child is on oxygen, and has intravenous access
    • Administer diazepam intravenously if there is any chance of awareness
    • DC revert using a synchronised shock of 1 joule/kg,
    • An unsynchronised shock is necessary for ventricular fibrillation or polymorphic ventricular tachycardia

    Stable Child - Vagal Manoeuvres And Adenosine

    Vagal manoeuvres. Valsalva if child old enough; gag or icepack/iced water for infants - apply to face for a maximum of 30 seconds. Do not use eyeball pressure.

    Intravenous adenosine

    Should be administered only by experienced staff.

    • Insert cannulae into a large proximal peripheral vein (the cubital fossa is ideal) with three way tap attached
    • Draw up starting dose of adenosine 0.1 mg/kg. If necessary dilute to 1 ml with normal saline. Don't draw up the adenosine until after inserting the IV. Adenosine is expensive and in some cases IV insertion alone will lead to reversion to sinus rhythm.
    • Draw up 10 ml saline flush
    • Turn on the ECG trace recorder
    • Administer adenosine as a rapid IV push followed by the saline flush
    • Repeat procedure at 2 minutely intervals, until tachycardia terminated, increasing the dose of adenosine by 0.05mg/kg each time up to a maximum of 0.3 mg/kg (max dose 18mg).
    • Perform 12 lead ECG post reversion

    The recorded strip at the time of conversion to sinus rhythm should be inspected and saved, for concealed pre-excitation which may only be revealed during the first few beats after conversion to sinus rhythm. After a patient has been reverted a 12 lead ECG should be performed to look for pre-excitation and other abnormalities.

    Rapid re-initiation of tachycardia is not uncommon, mostly due to premature atrial contractions stimulated by the adenosine. If this occurs consider trying adenosine again.

    Side effects including flushing and chest tightness/discomfort are not uncommon. These are usually brief and transient. Rarely atrial fibrillation or prolonged pauses may occur.

    Adenosine is contra-indicated in adenosine-deaminase deficiency (rare immune deficiency) and patients taking dypyridamole (Persantin). Care is required in asthma, as it may cause brochospasm.

    If these measures fail to revert the SVT, consult Cardiology.


    A follow up plan should be made in consultation with cardiology.

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