Ventricular fibrillation (v-fib) is the most serious cardiac rhythm disturbance and is potentially life threatening. V-fib occurs when the lower chambers of the heart quiver and the heart cannot effectively pump any blood resulting in cardiac arrest. 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. Collapse and sudden cardiac arrest follows — this is a medical emergency! If you or anyone you know is experiencing v-fib, seek medical attention immediately.