Supraventricular tachycardia will usually present with signs of congestive cardiac failure or shock, but will also depend on the age of the child. Sinus tachycardia can be up to about 200 beats per minute. Supraventricular tachycardia (SVT) is usually above 220 beats per minute.
Assessment
Symptoms
Infants usually present with pallor, dyspnea and poor feeding. Older children have palpitations and chest discomfort.
Signs
In SVT there is a regular tachycardia with a heart rate usually 180–300 per minute. Hypotension might be present but is often compensated early on in presentation. Heart failure with hepatomegaly with gallop rhythm occurs, especially in infants. Consult cardiology urgently if tachycardia is broad complex or irregular.
Management and Treatment
The child must be monitored with continuous ECG trace and frequent measurements of blood pressure. The options for treatment are listed below.
• If necessary apply oxygen 10 liter/min by facemask
• If child is shocked (i.e. 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
If the child is shocked, then direct current cardioversion is needed. You must:
• 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 0.5 J/kg. If this is unsuccessful, increase
dose to 1 J/kg and then to 2 J/kg if still unsuccessful
• An unsynchronised shock is necessary for ventricular fibrillation or polymorphic ventricular tachycardia
Stable child
If the child is stable, vasovagal maneuvers and adenosine should be tried:
• Vagal maneuvers: use the Valsalva maneuver if child old enough, the gag or icepack/iced water for infants (apply to face for a maximum of 30 seconds). Do not use eyeball pressure.
• Intravenous adenosine
• Insert cannula into a large proximal peripheral vein (the cubital fossa is ideal) with a 3-way tap attached
• Draw up starting dose of adenosine 50 µg/kg. If necessary dilute to 1 ml with
normal saline
• Draw up 10 ml saline flush
• Turn on the ECG trace recorder
• Administer adenosine as a rapid i.v. push followed by the saline flush
• Repeat procedure at 2-minute intervals, until tachycardia terminated, increasing the dose of adenosine by 50 µg/kg to a total dose of 300 µgµg/kg for infants of less than 1 month, and to a total dose of 500 µg/kg1 to children between 1 month and 12
years.
• Perform 12-lead ECG postreversion
The recorded strip at the time of conversion to sinus rhythm should be inspected and saved, for concealed pre-excitation 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 because of premature atrial contractions stimulated by the adenosine. If this occurs consider trying adenosine again. Side effects including flushing and chest tightness or discomfort are not uncommon but they are usually brief and transient. Rarely atrial fibrillation or prolonged pauses may occur. Adenosine is contraindicated in adenosine—deaminase deficiency (rare immune deficiency) and patients taking dipyridamole (Persantin). Care is required in asthma, as it may cause bronchospasm. If these measures fail to revert the SVT, consult a cardiology specialist.
Disposition
A follow-up plan should be made in consultation with cardiology. Some children may be started on beta blockers. There may be an underlying conduction abnormality such as Wolff-Parkinson-White syndrome.
Source pict: http://www.medscape.org/
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