Ventricular Fibrillation

cardiac arrest
Cardiac Arrest. Bruce Ayres/Getty Images

Ventricular fibrillation (VF) is an extremely dangerous form of cardiac arrhythmia, which invariably causes a sudden cardiac arrest.

VF occurs when the electrical impulse in the ventricles - the main pumping chambers of the heart - suddenly becomes disrupted, fragmented and chaotic. The loss of an organized electrical signal causes the ventricles to immediately stop beating, which causes the circulation to collapse.

Unless the circulation is restored, loss of consciousness usually occurs within 10 seconds, and death within 5 to 10 minutes.

What Causes Ventricular Fibrillation?

VF occurs when there is electrical instability within the ventricles. The most common cause of this electrical instability is the presence of cardiac disease that damages the heart muscle, particularly coronary artery disease (CAD) or heart failure.

The more extensive the muscle damage, the higher the risk of VF.

The best way to estimate the amount of heart muscle damage is to measure the left ventricular ejection fraction. The lower the ejection fraction, the more extensive the muscle damage, and the higher the risk of having an episode of VF. In general, the risk of VF becomes substantially elevated once the ejection fraction is reduced to less than 30 to 35%.

In people who have CAD, VF sometimes occurs during times when the heart muscle is acutely ischemic (that is, not getting enough oxygen). So VF can be brought on during an episode of angina, or during acute coronary syndrome (ACS).

However, in people with underlying heart disease VF commonly occurs suddenly, unexpectedly, and for no apparent reason.

This fact makes sudden death all too common in people with heart disease. It is estimated that around 30% of all deaths from CAD are sudden deaths - and most of these are caused by VF.

Other causes of VF include:

How Is Ventricular Fibrillation Treated?

VF is a medical emergency. It always produces a sudden cardiac arrest, which will lead to death within a few minutes unless effective treatment is delivered - which means immediate cardiopulmonary resuscitation (CPR) followed, as quickly as possible, by defibrillation.

Even though many people today know how to perform CPR, and automated external defibrillators (AEDs) are now available in many public places, the large majority of episodes of VF still result in sudden death. So the "best" treatment for VF is preventive.

Preventive Therapy

The very best way to prevent VF, and to keep your risk of sudden cardiac death as low as possible, is to avoid developing heart disease in the first place. You should make every attempt to maintain good cardiac health by keeping your cardiac risk factors under control.

If you already have significant heart disease - especially if you have had heart attacks or have heart failure - you should ask your doctor about taking steps to prevent VF and sudden death.

The aggressive medical therapy that is recommended today for people with these conditions, fortunately, helps at least somewhat to reduce the risk of sudden cardiac death. So if you have CAD or heart failure, you should familiarize yourself with those recommended treatments, and make sure your doctor is prescribing the therapy you need.

Despite receiving the best medical therapy, some patients with CAD or heart failure will still have a substantially elevated risk of VF. For many of these people, the use of an implantable cardiac defibrillator (ICD) should be strongly considered. In general, if your ejection fraction is below 30 - 35%, you should at least discuss this alternative with your doctor.


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de Vreede-Swagemakers JJ, Gorgels AP, Dubois-Arbouw WI, et al. Out-of-hospital cardiac arrest in the 1990's: a population-based study in the Maastricht area on incidence, characteristics and survival. J Am Coll Cardiol 1997; 30:1500.

Henkel DM, Witt BJ, Gersh BJ, et al. Ventricular arrhythmias after acute myocardial infarction: a 20-year community study. Am Heart J 2006; 151:806.

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