Ventricular fibrillation

Ventricular fibrillation (VF) is a severely abnormal heart rhythm (arrhythmia) that can be life-threatening.


The heart pumps blood to the lungs, brain, and other organs. Interruption of the heartbeat for only a few seconds can lead to fainting (syncope) or cardiac arrest.

Fibrillation is an uncontrolled twitching or quivering of muscle fibers (fibrils). When it occurs in the lower chambers of the heart, it is called ventricular fibrillation. During ventricular fibrillation, blood is not removed from the heart. Sudden cardiac death results.

The most common cause of VF is a heart attack. However, VF can occur whenever the heart does not get enough oxygen or if a person has other heart disorders.

Conditions that can lead to VF include:

  • Congenital heart disease
  • Electrocution accidents or injury to the heart
  • Heart attack
  • Heart muscle disease, including cardiomyopathies
  • Heart surgery
  • Ischemia (lack of oxygen to the heart muscle because of narrowed coronary arteries or shock)
  • Sudden cardiac death (commotio cordis), typically occurring in athletes after a trauma over the surface of the heart

Most people with VF have no history of heart disease. However, many have risk factors for cardiovascular disease, such as smoking, high blood pressure, and diabetes.


A person who has a VF episode will suddenly collapse or become unconscious, because the brain and muscles have stopped receiving blood from the heart.

The following symptoms may occur within 1 hour before the collapse:

  • Chest pain
  • Dizziness
  • Nausea
  • Rapid heartbeat
  • Shortness of breath

Exams and Tests

VF is an emergency condition. Seek immediate medical attention.

The pulse in the neck and groin area may be hard or impossible to feel. The person will be unresponsive.

The health care provider will listen to the heart with a stethoscope. The heartbeats may not be heard, or they may be very irregular.

A cardiac monitor will show a disorganized heart rhythm.


Ventricular fibrillation is a medical emergency and must be treated immediately to save a person's life.

If a person having a VF episode collapses at home or becomes unconscious, call the local emergency number (such as 911).

While waiting for help, place the person’s head and neck in line with the rest of the body to help make breathing easier. Start CPR with mouth-to-mouth breathing and chest compressions. Continue to do this until the person becomes alert or help arrives.

The emergency medical team will quickly examine the person while continuing CPR. The person will be taken to the hospital.

VF is treated by delivering a quick electric shock through the chest using a device called an external defibrillator. The electrical shock can immediately restore the heartbeat to a normal rhythm.

Medicines may be given to control the heartbeat and heart function. People with heart muscle damage may need additional procedures, including a heart transplant.

A cardiologist will look for potential causes of the VF.

An implantable cardioverter defibrillator (ICD) may be recommended for those who survive a VF attack and are at risk for future ones. The ICD can help prevent sudden cardiac death.

Moderate hypothermia therapy may be used on people who remain in a coma after treatment. This involves keeping the person slightly below normal body temperature for several hours. Such therapy has been shown to improve the outcome and reduce death.

Outlook (Prognosis)

VF can lead to death within a few minutes or a few days. The survival rate for a person who has a VF attack outside the hospital ranges between 2% and 25%.

Possible Complications

The most common complication of VF is sudden death (death that occurs within 1 hour after symptoms started).

For survivors of VF, complications include:

  • Coma
  • Nerve problems similar to those after a stroke
  • Reduced mental perception

When to Contact a Medical Professional

Call 911 if someone shows signs of VF.


An implantable defibrillator can help prevent future VF episodes in some patients. Others may need medicine to control the heartbeat.

Many public places and airplanes now have automated external defibrillators for use in an emergency. People may also buy these machines and keep them at home. Defibrillators have been proven to save lives. Another option for individual use is a defibrillator vest.

It is a good idea for family members and friends of VF survivors and patients with heart disease to take a CPR course. CPR courses are available through the American Red Cross, hospitals, or the American Heart Association.

Alternative Names

VF; Fibrillation - ventricular


Olgin JE, Zipes DP. Specific arrhythmias: diagnosis and treatment. In: Libby P, Bonow RO, Mann DL, Zipes DP. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 8th ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 35.

Update Date: 4/1/2012

Reviewed by: Issam Mikati, MD, Associate Professor of Medicine, Feinberg School of Medicine, Director, Northwestern Clinic Echocardiography Lab, Northwestern University, Chicago, IL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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