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How can SVT attacks be prevented?
There are different oral medications
(medicines taken by mouth) which can be
given to children who suffer from SVT, which
prevent attacks when taken regularly. The
choice of medication depends on the type of
tachycardia. Common medicines include:
Sotalol, Flecainide, Atenolol and Amiodarone.
How is an SVT attack stopped?
Emergency Contacts
IN AN EMERGENCY, DIAL
111
Your local hospital is:
“Vagal manoeuvres” can stop an attack of
SVT. These work by stimulating the vagus
nerve in the chest causing the heart to slow. In
the infant, you can try a cold (iced) flannel
over the eyes for about ten seconds. In
hospital (only), doctors may immerse a baby’s
face under cold water for a few seconds.
Children can put their thumb in their mouth
and blow hard on it—until they go red in the
face. A very cold drink, or standing on their
head can work too!
Starship Hospital
Ward 23B: (09) 6304949 ext 23230
www.starship.org.nz
Intravenous medications (medicines put
directly into a vein) are used in hospital to stop
an attack. The usual medications are
Adenosine and Amiodarone.
For booking issues :
Heart Surgery Ph: (09) 630 9946
Cardiac Catheter Ph: (09)623 6496
Electrical cardioversion is rarely needed.
This involves using a controlled electrical
shock to ‘jolt’ the heart back to a normal
rhythm and is done under a brief general
anaesthetic.
Can SVT be cured?
If the tachycardia persists to school age, the
SVT can be cured by physically disabling the
part of the heart causing the problem. This is
called
radio-frequency
ablation,
and
involves a cardiac catheter study where the
electrical pathways of the heart are clearly
mapped and the problem area identified and
disabled. It is usually done under a general
anaesthetic, and the catheters (special wires)
are passed to the heart from veins in the top
of the leg.
Contact us
For questions about your child’s
condition:
Children’s Heart Nurse Specialists
Mon—Fri
(09) 6309972
or
021 614348/ 021 774606
Supraventricular
Tachycardia
(SVT)
discharge information
for families
What is Supraventricular Tachycardia
(SVT)?
A normal heartbeat
originates from the
sinus node, the
heart's pacemaker.
The electrical signal
passes
to
the
bottom of the heart
through a special junction, called the AV node.
An abnormally fast heart rhythm (tachycardia)
can arise from the upper or lower chambers of
the heart, or be a "circuit" made up of the
upper and lower chambers. The heart’s
electrical activity can be seen well using an
electrocardiograph (ECG).
Tachycardias that originate from the lower
chambers (i.e. the ventricles) are called
ventricular tachycardias. Those that involve
the upper chambers (i.e. the atria) are termed
supraventricular tachycardias (SVT).
How dangerous is SVT?
Supraventricular tachycardias are usually not
dangerous. They are not due to a "heart
attack" and in children with an otherwise
healthy heart do not cause sudden death.
However, if they occur very often or for long
periods of time (hours to days) then they can
cause difficulty with the pumping action of the
heart. This can be dangerous if untreated.
Types
of
Tachycardia
Supra-Ventricular
Atrial tachycardia An area of
the upper chambers takes over
the pacemaker activity of the
heart.
This
is
relatively
uncommon in children.
Atrial Flutter A large area of
the upper chamber forms an
electrical circuit. This rhythm
can be seen in children who
have had previous heart
surgery involving the upper
chambers. Some children with
atrial flutter are at risk of
developing clots because the blood flow in
these chambers is slow and disorganized.
Atrio-ventricular re-entrant
tachycardia (AVRT)
An extra electrical connection
(called
an
"accessory
pathway") exists between the
upper and lower chambers.
The wave of electricity that
normally passes from the top
to the bottom of the heart can now pass back
up through the abnormal pathway, forming a
re-entry circuit. This is the most common form
of SVT in children under 8 years of age. The
majority of infants with atrio-ventricular reentrant tachycardia "outgrow" the tachycardia
during their first year.
Specific diagnoses falling into this category
include Wolff-Parkinson-White
Syndrome
(WPW)
and
Permanent
Junctional
Reciprocating Tachycardia (PJRT). WPW can
rarely be life-threatening in the older child, so
special tests and usually curative treatment
are recommended if it persists
to school age.
Atrio-ventricular nodal reentrant tachycardia
(AVNRT)
The atrio-ventricular node is
located between the upper
and lower chambers of the heart. It is normally
the only area that allows the electrical activity
of the heart to pass from the upper chambers
to the lower chambers. Sometimes this area
can become the source for a tachycardia. This
is the most common form of SVT in children
over 8 years of age.
How do I recognise if my child has
SVT?
In older children and adolescents, a fast heart
rate is often felt as palpitations. They may feel
their heart racing at unexpected times such as
resting, doing homework, after exercise or
eating dinner. Younger children may have
difficulty describing this sensation and may
complain of chest pain. SVT may rarely cause
children or adolescents to pass out (syncope).
Some newborns can be quite unwell if they
have had SVT in the womb for a long time,
however in most infants SVT is well tolerated.
The fast heart rate might be noticed while
cuddling the baby or during feedings. Some
infants develop poor feeding, irritability, or
pallor (unnatural paleness) if the SVT
continues. If your baby has a fast heart rate
very often or shows any of these signs, you
should seek medical advice.
When to seek help urgently
During a bad attack, your child may become
dizzy/ less alert, pass out, feel cold, look pale
and/or sweaty. Learning to take your child’s
pulse is an important skill that will help identify
when the rhythm is too fast. If you feel a fast
heart rate is causing your child to become
seriously unwell, call an ambulance.
Always call an ambulance if your child passes
out with an attack. If it is SVT, they should
wake up quickly. Try “vagal manoeuvres” (see
overleaf). Keep your child lying down, or
sitting, until fully recovered.