Bucks Montgomery Physician Spring 2021 - 11

Pathophysiology
Supraventricular tachycardia (SVT), also called paroxysmal
supraventricular tachycardia (PSVT), is defined as
an abnormally fast heartbeat that begins and ends
spontaneously and originates in heart tissue other than
the ventricles. It is a broad term that includes many forms
of heart arrhythmias that originate above the ventricles.
Supraventricular tachycardias are divided into re-entrant
tachycardias and automatic tachycardias1. Re-entrant
tachycardias occur when the electrical signal is conducted
more than once in a closed circuit, often having two
pathways. Re-entrant tachycardias can be further divided
into atrioventricular reciprocating tachycardia (AVRT)
where the re-entry is caused by an accessory pathway, or
atrioventricular nodal re-entrant tachyardia (AVNRT),
where the re-entry is occurring within the AV Node itself2.
In the pediatric age range, accessory AV pathways are the
most common cause of SVT, making up 80% of cases1.
Automatic tachycardia arises from abnormal automaticity.
Normally, automaticity is a property of the sinus node
and other conduction tissues. It allows for the slow
spontaneous depolarization of cells until a threshold
is reached allowing for an action potential to occur. In
certain conditions, often when there is damage to the
myocardium, some heart cells may acquire automaticity1.
If their intrinsic rate is higher than that of the sinus
node, they begin to set pace for the rest of the heart.
One such tachycardia that falls into this category is
the atrial ectopic tachycardia. In this tachycardia, an
ectopic site in the atria gains automaticity and acts as the
pacemaker. In this condition, heart rates of 250-300 can
be achieved in pediatric patients, though it is relatively
rare in children, making up only 5-10% of all SVTs1.

a benign condition, can cause complications such as
hemodynamic instability, left ventricular dysfunction,
tachycardia-induced cardiomyopathy, and heart
failure if not recognized and managed promptly1.
Vagal manoeuvres are effective in patients with AV reentrant tachycardia2. Adenosine is the drug of choice
at all ages for tachycardias involving the atrioventricular
node2. However, given that this patient's SVT was
most likely occurring from a pathway within the PFO,
guidelines become less clear. Patients with AV re-entrant
PSVT can be treated effectively by class Ic drugs, such
as propaphenone and flecainide1. Amiodarone has the
greatest anti-arrhythmic effect but should be used with
caution owing to the high incidence of side effects1.
Destroying the accessory pathways by Catheter Ablation
can be a permanent and long-term solution and allow
for freedom from pharmacological management2.

References
1. Neroni P, Ottonello G, Manus D, Atzei A, Trudu E,
Floris S, Fanos V. Paroxysmal supraventricular tachycardia:
physiopathology and management. J Pediatr Neonat
Individual Med.2014;3(2):e030243. doi: 10.7363/030243.
2. Colucci RA, Silver MJ, Shubrook J. Common
types of supraventricular tachycardia: diagnosis
and management. Am Fam Physician. 2010
Oct 15;82(8):942-52. PMID: 20949888.
3. Hany M A H M. Diagnosis and Treatment of
Supraventricular Tachyarrhythmia in Pediatric
Population: a Review Article. 2017; 2(4): 555595.
DOI: 10.19080/AJPN.2017.02.555595.

Discussion
The concomitant complete vision loss and onset of
neurological symptoms that superimposed on the
cardiac rhythm disturbance have been unprecedented.
SVT originating from foci in the inter-atrial septum
and anterior atrial septum have been common,
whereas foci in the PFO have been a rarity in medical
literature. Most supraventricular tachycardias affect
structurally healthy hearts1. Often, most tachycardias
in this age group are revealed by heart failure
signs, such as poor feeding, sweating and shortness
of breath1. The main symptom reported by schoolage children is palpitations1. SVT, although generally

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Bucks Montgomery Physician Spring 2021

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