Arrhythmia (Abnormal Heartbeat)

What Is an Arrhythmia?

An arrhythmia  is an abnormal heartbeat. Most arrythmias are 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 erratic pumping can lead to a variety of symptoms, including fatigue, dizziness, and chest pain.

Many arrhythmias don't need medical care, but some can pose a health problem and need to be evaluated and treated by a doctor.

What Causes an Arrhythmia?

A unique electrical conduction system in the heart causes it to beat in its regular rhythm.

The electrical signals start from a group of cells called the sinus node, located in the right atrium. The sinus node acts as the heart's pacemaker and makes sure the heart is beating at a normal and consistent rate. The sinus node normally speeds up the heart rate in response to things like exercise, emotions, and stress, and slows the heart rate during sleep.

But sometimes the electrical signals don't "communicate" properly with the heart muscle, and the heart can start beating in an abnormal rhythm — this is an arrhythmia (also called dysrhythmia).

Arrhythmias also can be due to chemical imbalances in the blood; infections; diseases that irritate the heart; medicines (prescription, over-the-counter, and some herbal remedies); injuries to the heart from chest trauma or heart surgery; use of illegal drugs, alcohol, or tobacco; caffeine; and stress.

Arrhythmias can be temporary or permanent. An arrhythmia can be congenital (meaning a baby is born with it) or happen later.

What are the Signs and Symptoms of an Arrhythmia?

Arrhythmias make the heart beat less effectively, interrupting blood flow to the brain and the rest of the body. When the heart beats too fast, its chambers can't fill with enough blood. When it beats too slowly or irregularly, it can't pump enough blood out to the body.

If the body doesn't get the supply of blood it needs to run smoothly, a person might have:

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

Arrhythmias can be constant, but most come and go at random. Some cause no detectable symptoms at all. In these cases, the arrhythmia is only found 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. Someone's normal heart rate depends on things like the person's age and whether he or she leads an active lifestyle. 

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

• babies (birth to 3 months of age): 100–150 beats per minute
• kids 1–3 years old: 70–110 beats per minute
• kids by age 12: 55–85 beats per minute

A doctor can determine whether a heart rate is abnormally fast or slow, depending on a person's situation. An older child or adult with a slow heart rate, for example, might have symptoms when the heart rate drops below 50 beats per minute. But trained athletes have a lower resting heart rate, so a slow heart rate in them isn't considered abnormal if it causes no symptoms.

What Are the Types of Arrhythmias?

There are many types of arrhythmias, including:

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

Premature contractions are usually considered minor arrhythmias. 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. Actually, the heart doesn't skip a beat — an extra beat comes sooner than normal. Occasional premature beats are common and considered normal, but in some cases they can be a sign of an underlying medical problem or heart condition.

Tachycardias

A tachycardia is an abnormally fast heartbeat. Tachycardias fall into two major categories — supraventricular and ventricular:

• Supraventricular tachycardia (SVT) is characterized by bursts of fast heartbeats that start in the upper chambers of the heart. These can happen suddenly and last anywhere from a few seconds to several days. Treatment is usually recommended if SVTs are long-lasting or happen often.
• Ventricular tachycardia is a serious but uncommon condition that starts in the lower chambers of the heart and can be dangerous.

Bradycardias

A bradycardia is an abnormally slow heartbeat. Bradycardias can be due to:

• Sinus node dysfunction, when the heart's sinus node isn't working correctly, usually after surgery to correct a congenital heart defect.
• Heart block, when electrical impulses can't make their way from the upper to lower chambers of the heart. It's often caused by a congenital heart defect, but also can be due to disease or injury.

How Is an Arrhythmia Diagnosed?

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

If an arrhythmia is suspected, the doctor will order an electrocardiogram (EKG) to measure the heart's electrical activity. For this painless test, the child will lie down and have small metal tabs (called electrodes) fixed to the skin with sticky papers. The electrodes have wires attached to them, which connect to the EKG machine. The electrical signals from the heart are then briefly recorded, usually for just 10 seconds. This information is sent to a computer, where it's interpreted and drawn as a graph.

These types of EKG tests might be recommended:

• 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 during exercising, like riding a stationary bicycle or walking on a treadmill.
• Signal-average EKG. This is much like a resting EKG, but monitors the heartbeat for about 15–20 minutes.
• Holter monitor. This EKG is done over a long period of time, usually 24 hours or more. The electrodes are fixed 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 is recorded only when the child feels symptoms and then turns the Holter monitor on.

How Is an Arrhythmia Treated?

Many arrhythmias don't need treatment. For those that do, these options might be used:

• Medicine. Doctors may prescribe anti-arrhythmic medicines depending on the type of arrhythmia and other considerations. Sometimes, these can increase symptoms and cause side effects, so the patient will be closely watched by the doctor.
• 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, a pacemaker can detect if the heart rate is too slow and send electrical signals to speed up the heartbeat.
• Defibrillators. A small battery-operated implantable cardioverter defibrillator (ICD) is surgically placed near the left collarbone. Wires run from the defibrillator to the heart. The ICD senses if the heart has a dangerously fast or irregular rhythm and sends an electrical signal to restore a normal heartbeat.
• Catheter ablation. A catheter (a long, thin wire) is guided through a vein in the leg to the heart. Arrhythmias often are caused by microscopic defects in the heart muscle. Once the problem area of the heart is pinpointed, the catheter heats or freezes the defective muscle cells and destroys them.
• Surgery. Surgery is usually recommended only if all other options have failed. The child will be put under anesthesia, and a surgeon will remove the tissue causing the arrhythmia.

When to Call the Doctor

Many arrhythmias are minor and aren't a significant health threat. But some can indicate a more serious problem. If your child has symptoms of an arrhythmia, call your doctor.