Atrial fibrillation

Overview

Atrial fibrillation is a type of arrhythmia in which the two upper chambers of the heart, called the atria, quiver instead of beating effectively. This may result in rapid and irregular impulses in the atrium — as fast as 300 per minute — which typically causes a faster than normal and irregular ventricular rhythm.

The "normal" number of heartbeats per minute, called pulse rate, varies with age. The heart beats about 140 times a minute in a newborn, compared to 70 times a minute in an older child at rest. Heart rate is not constant and changes in response to many factors, such as activity, fever and fear. In atrial fibrillation the heart cannot fill completely with blood, preventing the body from receiving the blood volume it needs to function properly.

Signs & symptoms

Atrial fibrillation may cause the following symptoms:

• Chest pressure or pain
• Fainting, also known as syncope, or near-syncope
• Fatigue
• Lightheadedness or dizziness
• Palpitations, which can be skipping, fluttering or pounding in the chest
• Shortness of breath

It is important to note that some children may not know how to describe what they are feeling during a period of atrial fibrillation. They may have trouble keeping up with other children or realize they are having "spells" and want to sit down and rest. Sometimes, a child does not experience any symptoms at all.

Diagnosis

Atrial fibrillation often occurs spontaneously and with unpredictable timing. Therefore, in many cases, the condition requires specialized tests to acquire an accurate diagnosis. If your doctor suspects that your child has an arrhythmia, such as atrial fibrillation, he or she will order one or more of the following diagnostic tests to determine the source of your child's symptoms.

• Electrocardiogram (ECG or EKG) — An electrocardiogram records the heart's electrical activity. Small patches called electrodes are placed on your child's chest, arms and legs, and are connected by wires to the ECG machine. The electrical impulses of your child's heart are translated into a graph or chart, enabling doctors to determine the pattern of electrical current flow in the heart and to diagnose arrhythmias.
• Electrophysiology (EP) Study — In an EP study, doctors insert special electrode catheters — long, flexible wires — into veins and guide them into the heart. These catheters sense electrical impulses and also may be used to stimulate different areas of the heart. Doctors can then locate the sites that are causing arrhythmias. The EP study allows doctors to examine an arrhythmia under controlled conditions and acquire more accurate, detailed information than with any other diagnostic test.
• Exercise Stress Test — An exercise stress or treadmill test records the electrical activity of your child's heart during exercise, which differs from the heart's electrical activity at rest.
• Event Monitor — This is a small monitor about the size of a pager that your child can have for up to a month. Since the arrhythmia may occur at unpredictable times, this will help to record the abnormal rhythm when your child is experiencing symptoms. He or she can just push a button on the pager and record the heartbeat. The recording can than be transmitted by phone to the doctor.
• Holter Monitor — A Holter monitor is a small, portable machine that your child wears for 24 hours. It is about the size of a portable tape player and provides a continuous 24-hour recording of your child's heartbeat onto a tape. You will be asked to keep a diary of your child's activities and symptoms. This monitor may detect arrhythmias that might not show up on a resting electrocardiogram, which only records a heartbeat for a few seconds at rest.

Treatment

Treatment for your child's atrial fibrillation will depend on the type and severity of your child's condition and the results of their various diagnostic tests, such as the electrophysiology (EP) study. You and your doctor will decide which treatment is right for your child.

The following treatments may be considered:

Medications

Certain anti-arrhythmic drugs change the electrical signals in the heart and help prevent irregular or rapid heart rhythms from occurring. Medication may be used to convert atrial fibrillation to a normal rhythm, slow down the heart rate or prevent recurrences. If medication is ineffective, the doctor may try to stop the atrial fibrillation with pacing or with an electrical cardioversion.

Cardioversion

Cardioversion is the delivery of an electrical shock to the heart using a medical device called a defibrillator. The shock is delivered through pads or paddles placed on the chest. On occasion, cardioversion is performed as an emergency procedure when the heart is beating so fast that the patient cannot maintain a stable blood pressure. The electrical shock will cause the fast rhythm to stop and the heart to restart in a regular rhythm.

If the patient is stable and can tolerate the rhythm, the cardioversion is scheduled ahead of time. Prior to the scheduled cardioversion, it is often necessary to run tests to make sure that there are no blood clots in the heart. Some people need medication to "thin" their blood before having the cardioversion.

For a scheduled cardioversion, the patient is sedated beforehand and his or her breathing is assisted. The electrical shock usually makes the patient's heart convert back to a normal rhythm. Afterward, to decrease the likelihood of the arrhythmia returning — or to prevent blood clots from entering the general circulation — your doctor may recommend a medication regimen.

Follow-up Electrophysiology Study

To make sure that your child's medication is working properly after two or more days in the hospital, your child may be brought to the Electrophysiology Laboratory for an electrophysiology (EP) study. Our goal is to determine the medication that works best for your child. On occasion, we admit children to the hospital and monitor their heart rhythm while we start the medication.

Catheter Ablation

In rare cases, catheter ablation may be used to treat atrial fibrillation in children. The procedure disrupts part of the electrical pathway causing irregular heart rhythms, providing relief for patients who may not respond well to medications, who prefer not to take medications or who can't take medications.

The procedure involves threading a tiny metal-tipped catheter through a vein or artery in the leg and into the heart. Using fluoroscopy or X-ray, doctors guide the catheter through a blood vessel to the heart. Additional catheters — inserted through the vein in the leg and the neck — contain electrical sensors to find the area causing the arrhythmia. This is called mapping.

The metal-tipped catheter is maneuvered to each site in the heart that causes the irregular heartbeat. Energy is sent through the tip of the catheter to destroy the extra electrical pathways that cause abnormal heart rhythms. In most cases, patients leave the hospital within 24 hours or the same day.