Fibrillation is an uncoordinated contraction of one or more of the muscles of the heart. It usually follows tachycardia. As the heart rate speeds up, it loses it's regular coordination and starts contracting randomly. The heart loses it's abililty to pump blood, resulting in loss of consciousness due to lack of blood in the brain, followed by cardiac arrest as the heart is starved of oxygen. Ventricular fibrillation is one of the most common forms of heart attack.
Fibrillation can be caused by many things including stimulants, lack of oxygen and electric shock. It is always a medical emergency and anyone suffering from it should be rushed to a hospital.
A heart in fibrillation should be treated with a defibrillator. This sudden electric shock can restore the regular rhythm of the heart. In addition, a drug such as digoxin which slows down the heart should be administered to prevent a second occurrence. Where a defibrillator is not available, CPR should be administered until qualified medical personnel arrive.