Arrhythmias

Arrhythmias

An arrhythmia is an abnormal heart rhythm usually caused by an electrical "short circuit" in the heart.

The heart normally beats in a consistent pattern, but an arrhythmia can make it beat too slowly, too quickly, or irregularly. This can cause the heart muscle's pumping function to work erratically, which can lead to a variety of symptoms, including fatigue, dizziness, and chest pain.

What Causes Arrhythmias?

The heart has its own conduction system, or electrical system, that sends electrical signals around the heart, telling it when to contract and pump blood throughout the body. The electrical signals originate from a group of cells in the right atrium, called the sinus node. The sinus node functions as the heart's pacemaker and makes sure the heart is beating at a normal and consistent rate. The sinus node normally increases the heart rate in response to factors like exercise, emotions, and stress, and slows the heart rate during sleep.

However, sometimes the electrical signals flowing through the heart don't "communicate" properly with the heart muscle, and the heart can start beating in an abnormal pattern — an arrhythmia (also called dysrhythmia).

Arrhythmias can be temporary or permanent. They can be caused by several things, but also can occur for no apparent reason. Arrhythmias can be congenital (meaning kids are born with it), sometimes due to a birth defect of the heart but sometimes even when the heart has formed normally.

Other causes of arrhythmias in kids include chemical imbalances in the blood, infections, or other diseases that cause irritation or inflammation of the heart, medications (prescription or over-the-counter), and injuries to the heart from chest trauma or heart surgery. Other factors (such as illegal drugs, alcohol, tobacco, caffeine, stress, and some herbal remedies) also can cause arrhythmias.

Signs and Symptoms

Because arrhythmias can cause the heart to beat less effectively, blood flow to the brain and to the rest of the body can be interrupted. If the heart is beating too fast, its chambers can't fill with the proper amount of blood. If it's beating too slowly or irregularly, the proper amount of blood can't be pumped out to the body.

If the body doesn't get the supply of blood it needs to run smoothly, these symptoms can occur:

Arrhythmias can be constant, but usually come and go at random. Sometimes arrhythmias can cause no detectable symptoms at all. In these cases, the arrhythmia can only be discovered during a physical examination or a heart function test.

What's a Normal Heart Rate?

Heart rate is measured by counting the number of beats per minute. Normal heart rate varies depending on factors like age and whether the person leads an active lifestyle or not. (For example, athletes often have a lower resting heart rate).

The resting heart rate decreases as kids get older. Typical normal resting heart rate ranges are:

Your doctor should help you determine whether or not your child's heart rate is abnormally fast or slow, since the significance of an abnormal heart rate depends on the situation. For example, an older child or adult with a slow heart rate might begin to show symptoms when his or her heart rate drops below 50 beats per minute. However, trained athletes have a lower resting heart rate — so a slow heart rate in them isn't considered abnormal if no symptoms are associated with it.

Types of Arrhythmias

There are several types of arrhythmias, including:

Premature Atrial Contraction (PAC) and Premature Ventricular Contraction (PVC)

Premature contractions are usually considered minor arrhythmias, in which the person may feel a fluttering or pounding in the chest caused by an early or extra beat. PACs and PVCs are very common, and are what happens when it feels like your heart "skips" a beat. It doesn't skip a beat — an extra beat actually comes sooner than normal. Occasional premature beats are common and considered normal, but in some cases they can indicate an underlying medical problem or heart condition.

Tachycardias

Tachycardias are arrhythmias that involve an abnormally rapid heartbeat. They fall into two major categories — supraventricular and ventricular:

  • Supraventricular tachycardia (SVT): is the most common significant arrhythmia, it's characterized by bursts of fast heartbeats that originate in the upper chambers of the heart. The bursts can happen suddenly, and episodes can last anywhere from a few seconds to several days. Specific treatment is usually recommended if incidents of SVT are long-lasting or happen often.
  • Ventricular tachycardia: is a serious but relatively uncommon condition that originates in the lower chambers of the heart and can be dangerous.

Bradycardias

Bradycardias — arrhythmias characterized by an abnormally slow heartbeat — include:

  • Sinus node dysfunction: is when the heart's sinus node isn't working correctly, most commonly following surgery to correct a congenital heart defect. An abnormally slow heartbeat is typically seen in this condition; however, episodes of rapid heartbeat due to SVT also can occur.
  • Heart block: is often caused by a congenital heart defect, but also can be the result of disease or injury. Heart block happens when electrical impulses can't make their way from the upper to lower chambers of the heart. When this happens, another node in the lower chambers takes over and acts as the heart's pacemaker. Although it sends out electrical impulses to keep the heart beating, the transmission of the signals is much slower, leading to a slower heart rate.

Diagnosing Arrhythmias

Doctors use several tools to diagnose arrhythmias. It's very important to know your child's medical history and give this information to your doctor, who will use it, along with a physical examination, to begin the evaluation.

If an arrhythmia is suspected, the doctor will probably recommend an electrocardiogram (EKG) to measures the heart's electrical activity. There is nothing painful about an EKG — a series of electrodes (small metal tabs) are fixed to the skin with sticky papers, then information about the electrical activity of the heart is transferred to a computer, where it's interpreted and drawn as a graph.

The doctor might recommend the following types of EKG tests:

Treating Arrhythmias

Many arrhythmias don't require treatment; however, some can pose a health problem and need to be evaluated and treated by a doctor.

Depending on the type and severity of the arrhythmia, one of these options might be recommended:

When to Call the Doctor

Although many arrhythmias are minor and don't represent a significant health threat, some can indicate a more serious problem. If your child has been having symptoms of an arrhythmia, call your doctor.

Reviewed by: Joel D. Temple, MD
Date reviewed: August 2012





Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor.

© 1995-2014 The Nemours Foundation/KidsHealth. All rights reserved.





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Related Resources
OrganizationNational Heart, Lung, and Blood Institute (NHLBI) The NHLBI provides the public with educational resources relating to the treatment of heart, blood vessel, lung, and blood diseases as well as sleep disorders.
Web SiteCongenital Heart Information Network The Congenital Heart Information Network's goal is to provide information and resources to families of children with congenital and acquired heart disease, adults with congenital heart defects, and the professionals who work with them.
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