Ventricular Fibrillation What is ventricular fibrillation? The heart beats when electrical signals move through it. Ventricular fibrillation (ven-TRIK u-ler fib rih-LA shun) ( V fib ) is a condition in which the heart s electrical activity becomes disordered. When this happens, the heart s lower (pumping) chambers contract in a rapid, unsynchronized way. (The ventricles flutter rather than beat.) The heart pumps little or no blood. AHA Scientific Position Ventricular fibrillation is very serious. Collapse and sudden cardiac death will follow in minutes unless medical help is provided immediately. If treated in time, V fib and ventricular tachycardia (ven-TRIK u-ler tak eh-KAR de-ah) (extremely rapid heartbeat) can be converted into normal rhythm. This requires shocking the heart with a device called a defibrillator (de-FIB rih-la-tor). Today one effective way to correct life-threatening rhythms is by using an electronic device called an implantable cardioverter-defibrillator. This device shocks the heart to normalize the heartbeat if the heart s own electrical signals become disordered. My advice is NOT to have one if at all possible.