Arrhythmias

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 hormones, 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.

Arrhythmias can be temporary or permanent. They can be caused by several things, but can also occur for no apparent reason. Arrhythmias can be congenital, meaning a child is born with the condition. This can happen in a child with a birth defect of the heart, or even if 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:

• dizziness
• fatigue
• lightheadedness
• weakness
• palpitations (a feeling of fluttering or pounding in the chest)
• shortness of breath
• chest pain
• fainting

Arrhythmias can be consistent or 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, trained athletes such as a teen or adult who plays competitive sports often have a lower resting heart rate).

The normal range for resting heart rate decreases from infancy to adulthood. An infant's normal resting heart rate from age 0–3 months is usually between 100 to 150 beats per minute. A child between the ages of 1–3 years typically has a resting heart rate of 70 to 110 beats per minute, and by 12 years of age will have a normal resting heart rate between 55 to 85 beats per minute.

An abnormally fast heart rate is call tachycardia. An abnormally slow rate is called bradycardia. 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 bradycardia 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 bradycardia in these individuals isn't considered abnormal if no symptoms are associated with it.

Types of Arrhythmias

Types of arrhythmias include:

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

Premature contractions are usually considered minor arrhythmias, in which someone 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 abnormally rapid heartbeat. They fall into two major categories — supraventricular and ventricular:

• Supraventricular Tachycardia (SVT). Supraventricular tachycardia (SVT) is the most common significant arrhythmia in children. It's characterized by bursts of fast heartbeats that originate in the atria (upper chambers of the heart) or the heart cells that carry electrical signals from the atria to the ventricles (lower 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 episodes of SVT are long-lasting or frequent.
• Wolff-Parkinson-White (WPW) Syndrome. Wolff-Parkinson-White (WPW) syndrome, a type of SVT, can run in families and is characterized by an extra electrical conduction path that connects the upper and lower chambers of the heart. The presence of this extra pathway can cause the heart to become flooded with electrical impulses, speeding up the heart rate.
• Ventricular Tachycardia. Ventricular tachycardia is a serious but relatively uncommon condition in children. It originates in the lower chambers of the heart and is usually a sign of serious underlying heart disease.

Bradycardias

The following are examples of bradycardias — arrhythmias characterized by abnormally slow heartbeat:

• Sick Sinus Syndrome. Sick sinus syndrome happens when the heart's sinus node or another part of its electrical conduction system isn't working correctly. This most commonly occurs in kids after surgery to correct a congenital heart defect. Abnormally slow heartbeat is typically seen in this condition; however, episodes of rapid heartbeat due to SVT can also occur.
• Heart Block. Heart block is often caused by a congenital heart defect, although it can also result from 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, and the information obtained about the electrical activity of your child's heart is transferred to a computer, where it's then interpreted and drawn as a graph.

The doctor might recommend the following types of EKG tests:

• Resting EKG. This measures resting heart rate and rhythm, and lasts about a minute.
• Exercise EKG (also called a stress test). This measures heart rate and rhythm while exercising, like riding a stationary bicycle or walking on a treadmill.
• Signal-average EKG. This measures heart rate much like a resting EKG. The only difference is the signal-average EKG monitors the heartbeat over a longer time period (around 15 to 20 minutes).
• Holter monitor. This is an EKG done over a long period of time, usually 24 hours or more. The electrodes are connected to the chest, and the wires are attached to a portable EKG recorder. The child is encouraged to continue normal daily activities, but must be careful to not get the electrodes wet (for example, no swimming, showering, or activities that cause a lot of sweating). The two kinds of Holter monitoring are: continuous recording, which means the EKG is on throughout the entire monitoring period; and event monitoring, which means data are recorded only when the child feels symptoms and then turns the Holter monitor on.

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 the following options might be recommended:

• Medications. Many types of prescription anti-arrhythmic medications are available to treat arrhythmia. The doctor will determine which is best by considering the type of arrhythmia, possible underlying medical causes, and any medications a child is taking. Sometimes, anti-arrhythmic medications can increase symptoms and cause unwanted side effects, so their use and effectiveness should be closely monitored by the doctor, you, and your child.
• Pacemakers. A pacemaker is a small, battery-operated device implanted into the body (near the collarbone) through a surgical procedure. Connected to the heart by a wire, pacemakers can help treat bradycardia. Through a sensing device, a pacemaker can detect if a child's heart rate is too slow and sends electrical signals to the heart to speed up the heartbeat.
• Defibrillators. Like a pacemaker, a defibrillator can deliver electrical impulses to the heart. A small battery-operated implantable cardioverter defibrillator (ICD) can be implanted into the body (near the left collarbone) through a surgical procedure. Wires run from the defibrillator to the heart. It senses if the heart has developed a dangerously fast or irregular rhythm and delivers an electrical shock to restore a normal heartbeat.
• Catheter ablation. "Ablation" literally means removal or elimination. In the case of catheter ablation, a catheter (a long, thin tube) is guided through a vein in the arm or leg and inserted into the heart to eliminate the heart muscle cells that are triggering the arrhythmia. Once the problem area of the heart is pinpointed, the catheter sends waves of high-frequency radio waves into the muscle cells and destroys them.
• Surgery. Surgery is usually the treatment recommended only if all other options have failed. In this case, the child is put under anesthesia, the chest is opened, and the heart is exposed. Then, the tissue causing the arrhythmia is removed.

When to Call the Doctor

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

Reviewed by: Steven Dowshen, MD
Date reviewed: November 2009
Originally reviewed by: Bernard J. Clark III, MD