Ventricular fibrillation (VF) is a life-threatening condition in which the heart ceases to beat effectively and instead “quivers” or fibrillates very rapidly – sometimes at 350 beats per minute or more. A person cannot survive this condition for more than a few minutes without emergency treatment. 

Most cases of ventricular fibrillation occur as a result of heart attacks. The person collapses or faints when the heart fibrillation interrupts flow of blood to the brain. However, ventricular fibrillation can also be caused by other forms of heart disease (e.g., heart failure) and heart rhythm disorders, or arrhythmias. A person experiencing ventricular fibrillation must be treated immediately to avoid sudden cardiac death. The treatment for ventricular fibrillation involves shocking the heart back into a normal rhythm with a defibrillator (either a manual defibrillator or an automatic external defibrillator). Giving someone cardiopulmonary resuscitation (CPR) may give him or her some extra time, but defibrillation is essential for surviving ventricular fibrillation. If defibrillation is administered fast enough, and the heart rhythm is restored to normal, the person is said to have experienced aborted sudden cardiac death.

Medical personnel can easily identify VF with their monitoring equipment and can quickly use a defibrillator to shock the heart back to its normal rhythm. However, the time it takes for medical help to arrive may be critical. Success is generally measured in minutes until treatment. People who experience VF outside a hospital setting have poor survival rates. For survivors, treatments to avoid future cases of VF may include either a wearable or implantable defibrillator, which can detect the abnormal rhythm and shock the heart immediately. Others may receive antiarrhythmia medications.

Because most cases of ventricular fibrillation are caused by heart attack, the most reliable warning sign of an impending episode is the heart attack itself. However, in rare cases, ventricular fibrillation may occur among people with healthy hearts or undiagnosed or familial heart disease. It is estimated that idiopathic ventricular fibrillation, which occurs in a person with an otherwise healthy heart, accounts for only about 5 percent of cases of sudden cardiac death. Unfortunately, ventricular fibrillation tends to produce few warning signs by itself. Some patients report changes in the hour or so before the attack, and many patients who experience ventricular fibrillation not related to a heart attack have a history of fainting. However, this lack of symptoms makes the condition difficult to prevent.