Pashupati Sah - SVT - SupraVentricular Tachycardia

Medical Disclaimer

The information provided here is for general informational purposes only, and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified healthcare provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read here.

If you or your child are experiencing a medical emergency, call your doctor or emergency services immediately. The techniques discussed, such as vagal maneuvers, should only be attempted in non-emergency situations under appropriate circumstances and with prior guidance from a healthcare professional. Any actions you take based on the information provided are strictly at your own risk.

Supraventricular Tachycardia (SVT) is an abnormally fast heart rhythm originating above the heart's ventricles. It can affect people of all ages, however the reason I created this page is that my child was diagnosed with it at the age of 9. The objective of this page is to tell parents that it is curable but to be aware of the signs of SVT, and basically to understand that this is a thing!

Early Signs

The early signs of supraventricular tachycardia (SVT) in children can vary depending on the child's age and the duration of the episode. However, some common symptoms parents or caregivers may notice include [I add our personal experience to this in this color!]:

1. Rapid Heart Rate

Palpitations: Children may complain of feeling their heart racing or beating very fast, even when they are at rest.
Noticeably fast pulse: For younger children who may not describe their symptoms well, parents might be able to feel a rapid heartbeat by placing a hand on the child's chest or feeling their pulse.

I understand that kids may complain of this after pretty much every play session, and even if they don't complain, their heart rate will definitely be very high after running around. The first time I thought the same for my child. But when the heart rate does not go down even after lying down for half an hour, it is time to bring out your Oximeter. Our episode was pre-COVID hence one didn't really have Oximeters as prevalent. However, a basic measurement using a watch was enough to show that my child had over 150 rate for more than an hour of complete rest. This, or even earlier, is when it would be a good idea to call a doctor. We were fortunate to have a paediatrician's phone number on speed-dial, people in many countries such as USA, may not be as lucky.

2. Dizziness or Lightheadedness

The child may feel dizzy or faint due to the reduced efficiency of the heart when it's beating too fast. This is often due to inadequate blood flow to the brain during an SVT episode.

I do not recall this complaint, but our child was starting to panic. An important tip is not to show panic in front of your child, just assure the child that things are being taken care of.

3. Fatigue or Weakness

Children may feel very tired or weak during or after an episode of SVT, especially if it lasts a long time. They might seem unusually fatigued compared to their normal activity level.

Not our experience, but I think this would be a result of a milder episode of an SVT episode. Our case was not mild.

4. Chest Pain or Discomfort

Some children may experience chest pain, discomfort, or tightness during an SVT episode. This is less common but can happen, especially if the episode is prolonged.

Yes, discomfort will pretty much always set in if the child has been undergoing high pulse rate for an extended period of time.

5. Shortness of Breath

The child may experience difficulty breathing or feel like they can't catch their breath. They may also breathe faster than normal.

Faster breathing would be a result of anxiety brought by the difficulty in breathing. This is a vicious cycle.

6. Paleness or Sweating

During an episode, a child might look pale, sweaty, or clammy, which can be a response to the heart working harder than usual.

True, sweating would be a result of the additional energy the child's body is expending.

7. Restlessness or Anxiety

Especially in younger children and toddlers, SVT might manifest as unexplained irritability, fussiness, or anxiety. They may seem restless and uncomfortable without an apparent cause.

This is a tricky one, as it may be directly related to other factors, especially when the child is having problems breathing.

8. Fainting

In more severe cases, the child may pass out (faint) due to a drop in blood pressure caused by the rapid heart rate. This can be a more concerning sign that requires immediate medical attention.

We were VERY lucky that our child had a strong BP throughout the three episodes he/she had to go through, especially the first one when we had no idea what was going on. We were dumb enough not to call the doctor sooner, but our stupidity was somehow forgiven.

9. Poor Feeding (in Infants)

In babies, SVT can sometimes be harder to detect, but poor feeding, lethargy, or difficulty breathing during feeding can be signs of an episode.

We have no idea about infants. My only advice: call the ER/doctor as soon as you suspect the slightest issue.

10. Lack of Activity Tolerance

A child who usually plays or is physically active may suddenly be unable to tolerate normal activities, becoming tired or winded more quickly than usual.

Again, related to other factors listed above.

When to Seek Help:

If a child exhibits any of these symptoms, particularly if they persist or recur, it's important to seek medical advice. An ECG (electrocardiogram) can help confirm the diagnosis of SVT, and a pediatric cardiologist can guide appropriate management.

We were very lucky that:

We had a paediatrician on speed dial
Our town had a hospital with paediatric cardiology department, which had paediatric ICU and paediatric cardiac surgeons!

Can you do anything while waiting for help to arrive?

There are some simple techniques that can be attempted while waiting for medical help to arrive if a child is experiencing an episode of SVT. These techniques are aimed at stimulating the vagus nerve, which can help slow the heart rate and sometimes stop the SVT episode. However, it’s important to try these only if the child is stable and responsive. If the child is fainting, having trouble breathing, or showing other signs of severe distress, immediate medical attention is necessary and it is best for a non-medical professional to carry out any of these only under supervision of a medical professional.

We did not know or try any of these during the first episode, however after that the doctor taught us the Cold Shock and Carotid Sinus Massage techniques. Hence, it is a good idea to learn these under the supervision of a medical professional, just in case.

DO NOT TRY ANY OF THESE ON AN INFANT.... in fact, do not try any of these on anyone if you have not learnt it from a medical professional and have been asked by them to carry it out!

1. Vagal Maneuvers

Vagal maneuvers stimulate the vagus nerve, which can help reduce the heart rate. The following methods are commonly used:

a. Cold Shock (Diving Reflex)

Method: Place an ice pack or a cold, wet cloth on the child's face or forehead for about 20–30 seconds. Alternatively, you can immerse the child's face in cold water (if they're old enough to understand and cooperate).
Why It Works: The cold triggers the diving reflex, which can slow down the heart rate.

b. Carotid Sinus Massage (Neck Massage)

Method: Gently massage one side of the neck where the carotid artery is located, right under the jawline. Do not massage both sides at once and avoid doing this in children with known carotid artery problems. Only attempt this with the guidance of a healthcare professional.
Why It Works: Stimulating the carotid artery can activate the vagus nerve and slow the heart rate.

c. Valsalva Maneuver (for Older Children)

Method: Have the child take a deep breath, hold it, and then bear down as if they are trying to have a bowel movement or blow out hard against a closed mouth and pinched nose for about 10–15 seconds.
Why It Works: The pressure generated increases intrathoracic pressure and can stimulate the vagus nerve to slow the heart rate.

2. Encourage Relaxation

Method: Reassure the child, keep them calm, and have them lie down in a comfortable position. Reducing anxiety can sometimes help lower the heart rate.
Why It Helps: Anxiety can worsen the episode by raising adrenaline levels and making the heart beat faster.

3. Blowing Through a Straw (for Older Children)

Method: Ask the child to blow forcefully into a straw or blow up a balloon. This is similar to the Valsalva maneuver and can help stop the SVT.
Why It Works: This action increases pressure in the chest, which can stimulate the vagus nerve.

What to Avoid:

Do not give any food or drink during an SVT episode, especially if the child is dizzy or disoriented.
Do not attempt maneuvers repeatedly if they do not work after one or two attempts. Continuing without success may cause unnecessary stress or worsen the episode.

Importance of Medical Attention:

Even if these techniques work and the heart rate returns to normal, it's crucial to follow up with a healthcare provider. They will need to assess the child to ensure there’s no underlying condition that needs treatment.

Why does a child have SVT?

There are several reasons why SVT might occur in a child:

1. Congenital Heart Conditions

Some children are born with abnormal electrical pathways in their hearts. A common condition associated with SVT in children is Wolff-Parkinson-White (WPW) syndrome, where an extra electrical connection (accessory pathway) in the heart can lead to episodes of rapid heart rate.

This was the reason for our child. Other reasons may be manifesting themselves in different ways.

2. Electrical Abnormalities

Even without congenital defects, some children may have a predisposition to abnormal electrical impulses in the heart's atria (upper chambers), which can trigger SVT.

3. Genetic Factors

SVT can run in families, so a genetic predisposition could make some children more susceptible to abnormal heart rhythms. If other family members have SVT, it could be a contributing factor.

4. Triggers

Physical activity or stress: Intense exercise or high emotional stress can sometimes trigger an episode of SVT in susceptible children.
Fever: High fevers in children can increase the heart rate and may sometimes precipitate an SVT episode.
Dehydration or electrolyte imbalances: These can sometimes alter the heart's electrical activity, making SVT more likely.

5. Previous Cardiac Surgery

Children who have undergone heart surgery (e.g., for congenital heart defects) may be more prone to developing arrhythmias, including SVT, due to scarring or altered pathways in the heart.

6. Viral Infections

In some cases, viral infections affecting the heart (like myocarditis) can disrupt the normal electrical signals, leading to SVT.

7. Idiopathic Causes

Sometimes SVT occurs with no identifiable cause, and it is simply a benign rhythm disturbance that children can outgrow.

What will the doctor do?

Ok, so this is a completely personal section as we are only aware of what the medical professionals can do if the child's heart has abnormal/extra electrical pathways in the heart....

Immediate Actions take at the ER

Use of injection ADENOSINE is to bring down the heart back to its normal rhythm. This injection MUST be administered by a Medical Professional.

The technical terms for the long-term treatment is: "RF Ablation after an EP Study".

Which stands for Radio-frequency ablation technique post an Electrophysiology (EP) study.

RF ABLATION:

This is a non-surgical procedure that treats abnormal heart rhythms, or arrhythmias, by destroying tissue in the heart that's causing the abnormal heart beats. In this case, it would be the additional/extra electrical pathways on the heart.

EP STUDY:

An electrophysiology (EP) study is a series of tests that examine the heart's electrical activity. It's also called an invasive cardiac electrophysiology test.

The heart's electrical system produces signals that control the timing of the heartbeats. During an EP study, the cardiologists can create a very detailed map of how these signals move between each heartbeat.

Medications Prescribed

A beta-blocker is normally prescribed for the first few weeks after the above procedures. Patient is reviewed after couple of weeks, then after a month and then, based on the recovery, maybe after every few months.

Below is additional heart related info for the nerdier people.....

The heart's pumping action is tightly controlled by an intricate system of electrical signals that regulate the contraction and relaxation of the heart muscle. Here's how the heart works from the perspective of its electrical signals:

1. The Heart’s Electrical System

The heart's electrical system consists of specialized cells that generate and transmit electrical impulses, ensuring that the heart beats in a coordinated and rhythmic manner. This system includes several key components:

Sinoatrial (SA) Node: Often called the heart's "natural pacemaker," the SA node is located in the upper right atrium. It generates electrical impulses at regular intervals (usually 60–100 times per minute in a healthy adult). These impulses initiate the heartbeat.
Atrioventricular (AV) Node: The AV node is situated between the atria and ventricles. It acts as a gateway, delaying the electrical signal slightly before allowing it to pass into the ventricles. This delay ensures that the atria have enough time to fully contract and push blood into the ventricles before they contract.
Bundle of His and Purkinje Fibers: After passing through the AV node, the electrical signal travels down a pathway called the Bundle of His, which divides into left and right bundle branches, and then into the Purkinje fibers. These fibers spread the electrical signal throughout the ventricles, ensuring that the muscle cells in the ventricles contract simultaneously.

2. Electrical Signal Pathway (Step by Step)

The process of a heartbeat, or cardiac cycle, involves the following sequence of events:

a. Impulse Generation (SA Node)

The SA node generates an electrical impulse that spreads through the walls of both atria. This electrical signal causes the atria to contract (a process known as atrial systole), pushing blood into the ventricles.

b. Signal Travels to the AV Node

The electrical impulse then reaches the AV node. The AV node slows down the signal for a brief moment (about 0.1 seconds). This pause ensures the ventricles have enough time to fill with blood before they contract.

c. Signal Travels to the Ventricles (Bundle of His and Purkinje Fibers)

From the AV node, the electrical signal travels down the Bundle of His and into the right and left bundle branches, which lead to the Purkinje fibers. These fibers distribute the signal through the ventricles, causing the ventricles to contract simultaneously (a process called ventricular systole).

d. Ventricular Contraction (Systole)

The contraction of the ventricles pushes blood out of the heart. The right ventricle sends blood to the lungs to receive oxygen, and the left ventricle pumps oxygenated blood to the rest of the body.

e. Repolarization and Relaxation (Diastole)

After the electrical impulse has passed, the heart's cells reset their electrical charge (a process called repolarization), which allows the heart muscle to relax (diastole). During this phase, the atria fill with blood from the body and the lungs, preparing for the next cycle.

3. Heart Rate and Rhythm

The frequency and regularity of the electrical signals from the SA node determine the heart rate and rhythm. For example:

Normal Sinus Rhythm: A healthy, regular heartbeat initiated by the SA node.
Tachycardia: When the electrical signals fire too rapidly, leading to an abnormally fast heart rate.
Bradycardia: When the electrical signals are too slow, causing a slow heart rate.
Arrhythmias: Abnormal heart rhythms that can arise from problems in the SA node, AV node, or conduction pathways.

4. Electrical Signal Coordination

The coordination of electrical signals ensures that:

The atria contract first, pushing blood into the ventricles.
The ventricles contract after, ensuring efficient blood flow out of the heart. This synchronized activity ensures efficient pumping of blood through the circulatory system, providing oxygen and nutrients to the body.

5. Role of Electrolytes

The movement of charged particles (ions) across the heart’s cells creates the electrical signals. Sodium (Na⁺), potassium (K⁺), and calcium (Ca²⁺) are key ions involved:

Depolarization: The influx of sodium ions causes the cells to become electrically charged, initiating the contraction.
Repolarization: Potassium ions exit the cells, resetting the charge and allowing the heart muscle to relax.
Calcium ions play a crucial role in the actual contraction of the heart muscle once the electrical signal has passed.

6. ECG (Electrocardiogram) Representation

An ECG is a visual representation of the heart's electrical activity:

P Wave: Represents atrial depolarization (when the atria contract).
QRS Complex: Represents ventricular depolarization (when the ventricles contract).
T Wave: Represents ventricular repolarization (when the ventricles relax).

The heart's electrical system is like a carefully timed conductor, sending signals that ensure the heart muscle contracts and relaxes in a precise rhythm. This electrical signaling allows the heart to pump blood efficiently throughout the body. Disturbances in this system can lead to arrhythmias, where the timing or pattern of these signals becomes abnormal, as is the case in SVT!

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