An arrhythmia, or abnormal heartbeat, is a change in the normal rhythm of the heart. Your child's heart may beat too fast or too slow. Or it may beat with an irregular or skipping rhythm.

The heart has an electrical system that creates signals to make the heart pump. When something affects those signals, an abnormal heartbeat can happen.

Four chambers hold blood as it moves through the heart. The two lower chambers of the heart are called ventricles. Problems with the electrical signals in the heart can make these ventricles beat faster than normal. There are two kinds of problems:

• Ventricular tachycardia (VT). Rapid electrical signals from the ventricles can cause a fast heart rhythm called ventricular tachycardia, or VT. The heart may be beating too fast to pump blood. This can make your child pass out. It can also cause cardiac arrest, which is when the heart stops beating. This can lead to sudden death.
• Ventricular fibrillation (VF). At times, electrical signals may be sent so fast and unevenly that the heart muscle quivers and doesn’t beat at all. This is called fibrillation. VF can occur if the heart's electrical signals become completely disorganized or if the ventricles have several abnormal circuits. It can also happen if the heart muscle is suddenly injured and becomes electrically unstable. The heart can get to the point that it can’t pump at all (cardiac arrest). Death will occur if emergency treatment isn't given to return the heart rhythm to normal.

Several things can cause an abnormal heartbeat. They include illness, a heart problem that a child is born with, medicines, and heart surgery. Some arrhythmias may run in families. Sometimes the cause isn't known.

Some children don't have symptoms from an abnormal heartbeat. But it can cause many symptoms. Your child may:

• Feel weak or tired.
• Feel lightheaded or dizzy.
• Feel their heart beat fast or skip a beat.
• Act cranky (in babies).
• Have chest pain.
• Pass out.

To diagnose an arrhythmia, the doctor will listen to your child's heart and ask about your child's symptoms. The doctor will also ask about any heart problems in your family. You may be asked to keep a journal of your child's symptoms.

Your child may have tests at the doctor's office. Or the doctor may want your child to go to a specialist (pediatric cardiologist) for tests.

Tests that your child may have include:

• An electrocardiogram (EKG or ECG). This test measures the electrical signals that control the heart's rhythm. The EKG shows the heart's activity as line tracings.
• An at-home heart monitor. Your child might use a heart monitor at home. It may be worn or carried. The monitor records EKGs of your child's heart over time.
• An electrophysiology study. A doctor puts catheters into blood vessels and moves them to the heart. The catheters have electrodes at the tips. They give the doctor details about the heart's electrical activity.

Some heart rhythm problems don't need treatment. Your doctor may watch your child over time to make sure that your child is doing well.

For more serious rhythm problems, treatment may include:

• Medicines. Certain medicines can slow down the heart if it's beating too fast. Other medicines can prevent an abnormal heartbeat from happening.
• An implantable cardioverter-defibrillator (ICD). An ICD is a device that's placed under the skin and connected to the heart. It uses electrical signals or a shock to stop a deadly heart rhythm.
• Cardioversion. This procedure uses a shock to help return the heart to a normal rhythm.
• Catheter ablation. A doctor puts thin tubes called catheters through a blood vessel and into the heart. Wires in the catheters use energy to destroy tiny areas of the heart that cause the abnormal heartbeat.
• Surgery. Sometimes surgery may be done. Heart tissue might be cut to try to stop the signals that cause the abnormal heartbeat.