Fast Heart Rate (Tachycardia)

How does the heart beat?

The heartbeat is controlled by electricity. Special cells called pacemakers release bursts of electrical energy that travel through the heart muscle, causing it to contract. When the muscle contracts, blood is pumped through the heart.

What is an arrhythmia?

An arrhythmia​ (also called dysrhythmia) refers to what is usually an irregular heartbeat. The heart rate can be fast, slow, or irregular, taking into consideration age and activity. For example, a newborn’s heart beats much faster than a 5-year-old child’s heart.

What is tachycardia?

Tachycardia is a type of arrhythmia. It is a fast heart rate. With tachycardia, the resting heart rate for a newborn can increase to over 160 beats per minute. This can last for seconds, minutes, or even hours, depending on how serious it is. Symptoms include feeling dizzy, weak, and generally uncomfortable.

It’s important to know that it is unusual for tachycardia to cause the heart to stop all of a sudden, and it usually does not last long enough to cause serious damage.

There are two basic types of tachycardia:

  • ventricular tachycardia, which involves only the ventricles
  • supraventricular tachycardia (SVT), which involves both the atria and the ventricles

The most common tachycardia in children is supraventricular tachycardia. This used to be called paroxysmal atrial tachycardia.

Ventricular tachycardia

This fast heart rate starts in the ventricles. It is not common, but it can be very serious. It usually happens in children with serious heart disease, but sometimes it happens on its own.

 

Ventricular Tachycardia
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A very fast heart rate originating in the ventricles.

Supraventricular tachycardia (SVT)

This is the most common type of tachycardia in children. It involves both the upper and lower chambers of the heart. During an SVT episode, a child may breathe faster or seem sleepier or crankier than usual. The heart rate can reach more than 220 beats per minute.

Treatment may be provided if the episodes happen often and last for a long time. Treatment involves stopping a current episode and preventing future episodes. Some of these procedures can be simple, such as putting ice or cold water on the face. Others involve delivering electricity through a catheter (radiofrequency catheter ablation) or shocks to the chest wall (cardioversion).

There are several different types of SVT. The main types are as follows:

  • atrioventricular reentry tachycardia (AVRT)
  • atrioventricular nodal reentry tachycardia (AVNRT)
  • atrial flutter
  • atrial ectopic tachycardia
  • junctional ectopic tachycardia

Atrioventricular reentry tachycardia (AVRT)

With this arrhythmia, there is an extra electrical loop or circuit that connects the atrium and the ventricle, without passing through the AV node. This extra circuit pathway allows the heart's electrical impulse to go backwards and start another heartbeat. The fast heart rate occurs because the impulse is moving through the two pathways at the same time.

 

Atrioventricular Reentrant Tachycardia (AVRT)
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An extra electrical circuit encompassing the atrium and the ventricle causes the heart's electrical impulse to go backwards and start another heartbeat, resulting in a fast heart rate.

Atrioventricular nodal reentry tachycardia (AVNRT)

Atrioventricular nodal reentry tachycardia involves an extra electrical loop or circuit contained in the AV node. With this tachycardia, the extra pathway allows the heart's electrical impulse to go backwards and start another heartbeat. The fast heart rate occurs because the impulse is moving through the two pathways at the same time.

 

Atrioventricular Node Reentry Tachycardia (AVNRT)
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An extra electrical circuit contained in the atrioventricular node causes the heart's electrical impulse to go backwards and start another heartbeat, resulting in a fast heart rate.

Patients with this tachycardia tend to have more symptoms than those with AVRT. It tends to be more common in females and often is not the result of a heart condition.

Atrial flutter

This arrhythmia is caused by one or more rapid electrical circuits located in the atrium. As the atria have less time to push blood through to the ventricles, the ventricles may not fill up completely, and so the body may not get enough oxygenated blood.

 

Atrial Flutter
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A fast heart rate caused by one or more rapid circuits in the atrium.

Atrial flutter can occur in healthy individuals or in connection with a congenital heart defect. It is usually associated with underlying heart disease, and can occur after repair surgery.

Atrial ectopic tachycardia (AET)

"Ectopic" means "out of place;" in this case, it refers to an impulse originating somewhere other than the sinus node. This arrhythmia is prompted by a small abnormal cluster of cells that sends signals to the atrium, causing the atrium to contract before it should and at too fast a rate. There is often a delay in the conduction of the impulse at the AV node.

 

Atrial Ectopic Tachycardia
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A small abnormal cluster of cells in the atrium prompt the atrium to contract before it should, and at a quick rate.
 

AET can occur in a healthy heart, with an untreated congenital heart defect, or after surgery.

Junctional ectopic tachycardia (JET)

"Ectopic" means "out of place;" in this case, it refers to an impulse originating somewhere other than the sinus node. JET results from an abnormal cluster of conduction cells in or near the atrioventricular node that cause the ventricle to contract too quickly.

 

Junctional Ectopic Tachycardia (JET)
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An abnormal cluster of conduction cells in or near the atrioventricular node cause the ventricle to contract quickly.

JET is a very rare type of SVT. It is usually a complication of surgery, although it can occur in a structurally normal heart. This is a serious condition, as it responds poorly to antiarrhythmic drugs and cardioversion.

How is tachycardia diagnosed?

A tachycardia can be diagnosed with one of the following:

How is tachycardia treated?

Treatment depends on what is causing the tachycardia. Some SVTs can be stopped with certain techniques called vasovagal manoeuvres, including:

  • blowing on your thumb like it’s a horn
  • blowing through a straw with your hand on the end to plug it
  • putting ice or cold water on the face for a few seconds

Other tachycardias can be helped with medication. Drugs can help prevent the episodes from starting, decrease the heart rate during the episode, or shorten how long the episode lasts.

Radiofrequency catheter ablation (RFCA)​ is another option. This approach delivers electricity to the heart to permanently interrupt the abnormal electrical pathway. One of the newer approaches is cryoablation, which involves the use of freezing.

 More Information
Key points

  • Tachycardia is an abnormally fast heart rate.
  • During an episode of tachycardia, your child may feel dizzy, weak, or uncomfortable, and the heart may beat more than 160 times per minute.
  • It is unusual for tachycardia to cause the heart to stop all of a sudden.
  • Tachycardia usually does not last long enough to cause serious damage.
  • There are many different types of tachycardia. Usually, they are caused by a problem with the heart's electrical system.
  • Treatment depends on what is causing the tachycardia.

Elizabeth Stephenson, MD, MSc

3/19/2010




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