What is PSVT?

Paroxysmal supraventricular tachycardia (PSVT or shortly SVT) is when the heart starts beating quickly and suddenly (hence the name paroxysmal which means abrupt start and termination) much faster than normal beats. It can be normal in some people but in children, it is alarming and needs attention and further investigation. 

It is considered to be the second most frequent arrhythmia in newborns and infants, after tachycardia (increased regular heart beats).¹ One subtype of PSVT is Wolff-Parkinson-White syndrome (WPW), which is the most prevalent kind of PSVT in young children.

The estimated incidence of PSVT in healthy children is 1 in 250. In children under one year old, a heart rate of more than 220 beats per minute (bpm) and in children over one year old heart rate of more than 180 beats per minute is suggestive of PSVT. 

This condition appears in the first year of life in 40% of cases.² However, 90% of the infants resolve spontaneously in their first year while a third of them have recurrence at a mean age of about 8 years. What is important to say is that PSVT occurs in children with mostly structurally normal hearts while it also happens to affect children with congenital heart disease. 

It is important to understand and recognise the symptoms of PSVT in children to be able to diagnose and treat it if needed. The decision to treat is based on the frequency and complexity of the symptoms. Infants should be treated as they will not be able to recognise symptoms nor express them, while some children do not require any therapy.

What happens in PSVT?

Simply explained, normally our heart has two chambers: two upper and two lower. The upper chambers are connected to the lower chambers through a circuit of electricity. When a child has PSVT, most commonly it means that there is an extra electrical pathway (accessory pathway) in the heart other than the normal one which causes disturbance in the physiology of the heart electricity resulting in these extra fast beats, the PSVT. 

PSVT makes the heart work harder to pump blood, particularly if it persists for a long period. Extended periods can exhaust the heart and impair its regular pumping function.³ However there are other causes for PSVT, such as:

• Congenital heart diseases: Heart defects at birth such as Ebstein anomaly of the tricuspid valve, and ventricular or atrial septal defects were found to be associated with PSVT in about 9% to 32% of the cases³
• After cardiac surgery: it is common postoperatively in some children to have different arrhythmias such as PSVT that respond easily to drugs. Moreover, PSVT can be provoked by cardiac surgery if it already exists in the patient⁴
• Genetic: some types of PSVT were found to have a genetic background where the patient had a first-degree relative with documented SVT. Other patients with a subtype called WPW syndrome have the liability of 3 times more risk than the population to have an affected first-degree relative with the same syndrome³

What are the symptoms of PSVT in children?

The self-limiting nature and non-specific symptoms make recognising PSVT in children a bit challenging. Certain children with PSVT show no symptoms at all. The episodes might occur once a year or many times a day, ranging from a few minutes to several hours, and vary greatly in frequency and length. 

Palpitations, or the sensation of a rapid heartbeat or hammering in the chest, are the most typical when they occur. Additional signs and symptoms might be:⁵

• Lightheadedness
• Fatigue
• Weakness
• Palpitation, breathing difficulties and chest discomfort in older children
• Losing consciousness
• Poor feeding, excessive crying, and irritability can be found in infants

Heart rate during an episode is frequently described as "too fast to count" if someone attempts to take a reading. Babies may be diagnosed with PSVT if they exhibit signs of congestive heart failure. For several hours, a baby's heart rate may be kept extremely high without causing any symptoms. The symptoms are mild at first, but unless the rapid beat stops on its own or the problem is addressed, they will get worse. 

Generally speaking, PSVT rarely poses a life-threatening risk, and episodes don't require immediate medical attention. Vagal manoeuvres (massaging the neck at certain points to stimulate the vagus nerve that controls the rhythm to the heart) ought to be attempted in the event of an episode. If the event lasts more than 45 minutes, a child should be driven to a nearby emergency department in an appropriate amount of time.⁶ 

It is worth mentioning that the death rate from PSVT is nearly 1% in those with concomitant cardiac disease while it is 0.25% in those with normal heart structure.⁷

How is PSVT diagnosed in children?

There are different modalities that some or all of them may be used in approaching a case of PSVT. Among these are:

1. Resting Electrocardiogram commonly known as Resting ECG is the main tool used to diagnose PSVT. It is important to catch the rhythm of the PSVT during the acute attack as it gives many clues to differentiate different types of SVT from other arrhythmias.
2. Exercise ECG (known as stress ECG): It records heart rate and rhythm when exercising, such as walking on a treadmill or pedalling a stationary bike.
3. However, if the child was not taken to the ER or the physician at the time of the attack, PSVT could be recorded through another tool called Holter ECG. It is a 24-hour ECG, in a small device that the child can wear wrapped around their arm and the recording is taken afterwards by the physician and is analysed. This device could save up to 15-30 days of data to detect rare or paroxysmal attacks of SVT.
4. Electrophysiological study (EPS) is another invasive tool that is both diagnostic and therapeutic. It is used mainly to search for the primary cause of PSVT. In certain situations, EPS wouldn't be essential if it were possible to predict the mechanism of SVT by noninvasive methods.⁸
5. Echocardiography is a type of ultrasound imaging technique that is done on the heart to capture pictures of it and assess its function. It is useful in determining congenital anomalies or any post-surgical abnormalities that occurred to the heart of the child.

What is the management of PSVT in children?

Acute management

1. Vagal manoeuvres: done to your child by massaging the neck at a certain area at one side at a time to stimulate the vagus nerve which slows down the heart rate. Another technique called the Valsalva manoeuvre can be done at the child’s bedside, the Valsalva procedure can be done by pressing down on a closed glottis for a duration of 10 to 30 seconds.
2. Adenosine administration: is given when the vagal stimulation fails. It is given as shots in the blood until reaching the maximum dose. Afterwards monitoring by ECG is done to ensure whether that the patient reached a normal heart rate or failed. However, adenosine any drug, could cause side effects such as inducing dysrhythmia therefore 
3. Cardioversion: the use of electric shock to unstable patients who have low or no recorded blood pressure. The aim is to restore the heart's normal beats as if it's “resetting” the heart’s electricity. This of course happens when the patient arrives at the ER.

Long-term management

1. Medications (e.g., beta-blockers, calcium channel blockers): these are drugs that are given to the child by the physician to slow the heart rate to normal levels. Sometimes they are prescribed for acute cases but they are also given for long-term control. Your child should be seen by the physician for regular assessment as these drugs have side effects in the long run.⁹
2. Catheter ablation: is the definitive treatment for recurrent or symptomatic PSVT. When given to symptomatic children it enhances quality of life and decreases anxiety that occurs due to PSVT attacks. 

Doctors insert a catheter, which is a tiny, flexible plastic wire through an artery or vein in the child's leg and into the heart while they are having anaesthesia. Once the exact location of the heart's problem is identified, the catheter tip can burn or freeze the tissues responsible for the arrhythmia using hot energy (known as radiofrequency ablation) or cold energy (known as cryoablation).¹⁰

Are there any complications of PSVT in children?

Untreated PSVT episodes can weaken the heart over time and cause the heart to fail to pump. This is especially true for those children who concurrently suffer from other illnesses such as congenital heart disease. PSVT attacks that are severe enough to produce fainting or sudden cardiac arrest, which is a complete stop of heart action.

Complications are sometimes related to medications or ablation as it is an invasive procedure. These complications are:⁶

• Haematoma formation (blood sequestration in the tissue)
• Pseudoaneurysm of the artery (dilation in the wall of the artery)
• Loss of blood
• Infarction of the heart
• Dysfunction in the electricity of the heart may further need a device to control it called a pacemaker
• Stroke
• Death

Physicians who treat children with PSVT should prioritise supporting families. They should stress that while PSVT usually poses no threat to life, it can if the condition of the patient is left untreated. 

The diagnosis, prognosis, and available treatments should be the main topics of instruction. Reducing anxiety and lessening the fear of the unknown should be prioritised. The family should know what to anticipate, who to call in the event of an incident, and when to call emergency services. Plans for school emergencies should contain similar information and are as critical.

Summary

PSVT, or Paroxysmal Supraventricular Tachycardia, is a sudden, rapid heartbeat disorder affecting children, often caused by an extra electrical pathway in the heart. It's the second most common arrhythmia in newborns, with an incidence of 1 in 250 healthy children, usually presenting in the first year of life. 

Symptoms vary, from palpitations to lightheadedness and fainting. Diagnosis involves tools like ECGs and echocardiography, while management includes vagal manoeuvres, medication, and, in severe cases, cardioversion or catheter ablation. Long-term care focuses on medication or ablation to prevent recurrent episodes. Complications, such as heart failure or stroke, can arise if untreated. 

The support of the children’s families is crucial, through education and emergency plans, as SVT, though usually non-life-threatening, can lead to severe outcomes. Recognising symptoms early and seeking medical attention promptly is essential for optimal management and outcomes.