Ventricular Fibrillation

In ventricular fibrillation, the left ventricle contracts so irregularly, rapidly, and weakly that it quivers.

Different parts of the ventricle contract at different times. As a result, little if any blood is pumped from the heart. Thus, ventricular fibrillation is a form of cardiac arrest (when the heart suddenly stops pumping). Unless treated within 4 to 6 minutes, ventricular fibrillation usually results in permanent brain damage or death within several minutes after it begins.

The most common cause of ventricular fibrillation is coronary artery disease, particularly a heart attack. Other causes include severe heart failure, electrical shock, a dangerously low body temperature (hypothermia), near drowning, and very low levels of potassium in the blood (hypokalemia). Certain antiarrhythmic drugs used to treat other arrhythmias can, on occasion, cause ventricular fibrillation.

Ventricular fibrillation causes loss of consciousness within seconds. A person suddenly collapses, turns deadly white, has very dilated pupils, and has no detectable pulse, heartbeat, or blood pressure. Vital organs (such as the heart, brain, and kidneys) do not receive enough blood. Without treatment, the person dies within minutes.

Diagnosis and Treatment

Ventricular fibrillation is suspected when a person suddenly collapses and does not have a pulse or blood pressure. The diagnosis is confirmed by electrocardiography (ECG).

Ventricular fibrillation must be treated as an extreme emergency. Cardiopulmonary resuscitation (CPR) must be started within a few minutes. It must be followed by defibrillation (an electrical shock delivered to the chest) as soon as the equipment is available. Antiarrhythmic drugs may then be given to help maintain the normal heart rhythm.

When ventricular fibrillation is treated within a few minutes (before lack of oxygen damages the brain or other vital organs), some people recover completely. However, people who are successfully resuscitated from ventricular fibrillation due to coronary artery disease are at high risk of another episode. They should usually be evaluated with cardiac catheterization (coronary angiography) or electrophysiologic testing.

If possible, the disorder causing ventricular fibrillation is treated. Otherwise, a defibrillator is surgically implanted. Alternatively, antiarrhythmic drugs are given to prevent recurrences. People who have severe coronary artery disease and poor heart pumping function are less likely to survive, even when defibrillation is promptly done.