Ventricular fibrillation (V-fib) is a form of cardiac arrhythmia characterized by an irregular heart rhythm. During ventricular fibrillation, the ventricles contract rapidly and in an irregular manner. As a result, the heart fails to circulate blood throughout the body. When blood circulation stops for this reason, one generally has only a few seconds before losing consciousness. This is known as Cardiac arrest, usually fatal within minutes without immediate medical attention.