Ventricular Fibrillation (VF)

What is ventricular fibrillation (VF)?

Ventricular fibrillation (VF) is an abnormal heart rhythm that causes death. It is responsible for 75-80% of sudden deaths due to heart problems. Normally, heart muscle cells squeeze (contract) in rhythm at the same time to pump blood. These groups of cells are located in the bottom two pumping chambers of the heart (ventricles). In someone with ventricular fibrillation, some heart cells contract while others are relaxing, and blood stops flowing.

VF starts very suddenly. With no blood flow, brain death occurs within 3 to 5 minutes.

How does it occur?

The most common cause of ventricular fibrillation is a heart attack, although VF can occur whenever the supply of oxygen to the heart muscle is decreased. Acute or previous heart attacks, narrowing of coronary arteries by atherosclerosis, and low blood pressure and shock all may lead to VF.

How is it treated?

If you see someone suddenly lose consciousness or collapse, prompt actions should be taken to help the person. Cardiac life support or cardiopulmonary resuscitation (CPR) courses can teach you the basic steps to follow. The courses are locally available through the American Red Cross, hospitals, or the American Heart Association.

The head and neck of the unconscious person should be positioned to help the person breathe more easily. Try to find a pulse in one of the carotid arteries. The carotid arteries are located just below the angle of the jaw on either side of the neck.

If you do not feel a pulse, call 911 for emergency help. Start CPR with mouth-to-mouth breathing and chest compressions. Continue CPR until help arrives or the person regains consciousness.

When they arrive, emergency medical personnel will quickly examine the person. A defibrillator, which passes a quick electric shock through the chest, may be used to change the VF to a normal rhythm. In many public places and on some airplanes, computer-controlled devices called automatic external defibrillators (AEDs) are available that allow a person without medical training to shock the heart back into a normal rhythm. CPR may need to be continued for a time. Medicines that stabilize heart rhythm and function may be given through a vein, as needed.

If VF occurs in the hospital, prompt medical attention is usually available and is more likely to be successful.

Once the VF has been treated and normal heart rhythm restored, the doctor will look for and treat the causes of the abnormal rhythm.

Information obtained from GE Medical Systems; authorization given to reproduce on HCNW web site 9/02.
Written by Donald L. Warkentin, MD
Published by McKesson Clinical Reference Systems.
Copyright © 1997-2002 McKesson Health Solutions LLC. All rights reserved.

This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.