Clinical Practice Guidelines

Supraventricular Tachycardia SVT

  • Assessment

    Symptoms

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

    Signs

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

    Investigations

    12 lead ECG showing regular narrow complex tachycardia.

    SVT

    Consult cardiology urgently if tachycardia is broad complex or irregular.

     Management

    • 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 synchronized shock of 1 joule/kg,
    • An unsynchronized shock is necessary for ventricular fibrillation or polymorphic ventricular tachycardia

    Stable Child - Vagal Manoeuvers And Adenosine

    Vagal manoeuvers. 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. Alert ICU before use.

    • 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.

    Disposition

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