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Ventricular fibrillation



Ventricular fibrillation (VF) is a condition in which the heart's electrical activity becomes disordered. When this happens, the heart's ventricles — the lower chambers that pump blood — contract in a rapid, unsynchronized way. The ventricles "quiver" rather than beat, causing the heart to pump little or no blood.

VF is life-threatening and requires prompt treatment. Without medical treatment, collapse and sudden cardiac death will occur. However, VF can be treated with a medical device called an implantable cardioverter defibrillator (ICD), which brings the heartbeat back to a regular rhythm.

Signs & symptoms

Ventricular fibrillation may cause the following symptoms:

  • Chest pressure or pain
  • Fatigue
  • Lightheadedness or dizziness
  • Palpitations, which can be skipping, fluttering or pounding in the chest
  • Shortness of breath


Ventricular fibrillation (VF) may occur spontaneously with unpredictable timing, and specialized tests are needed to make an accurate diagnosis. If your child's doctor suspects your child has an arrhythmia caused by ventricular fibrillation, he or she will order one or more of the following diagnostic tests:

  • Electrocardiogram (ECG or EKG). An ECG 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 then 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 for ventricular fibrillation depends on the type and severity of the condition and the results of the diagnostic tests, such as the electrophysiology (EP) study. You and your child's doctor will decide which treatment is right for your child.

A medical device called an implantable cardioverter defibrillator (ICD) is one possible treatment. While not a cure for heart rhythm problems, an ICD stops a very fast heart rhythm and brings the heartbeat back to normal. It may prevent sudden cardiac death. Defibrillator paddles may either be applied to the chest externally or the defibrillator may be implanted internally, which is known as an internal cardiovertor defibrillator (ICD). An ICD is the most common therapy for children with VF.

UCSF Benioff Children's Hospitals medical specialists have reviewed this information. It is for educational purposes only and is not intended to replace the advice of your child's doctor or other health care provider. We encourage you to discuss any questions or concerns you may have with your child's provider.

Where to get care (3)

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Arrhythmia Center

Arrhythmia Center

San Francisco / Oakland

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Cardiology Clinic

Cardiology Clinic

San Francisco / Oakland / Berkeley / Brentwood / Eureka / Fairfield / Fr...

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Pediatric Cardiac Intensive Care Unit

Pediatric Cardiac Intensive Care Unit

San Francisco / Oakland

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