As a result of decreased blood flow you may feel faint and lightheaded. Atrial fibrillation may have no apparent cause, or it may be a result of heart disease or excess thyroid hormone. Treatment consists of medication or, in some cases, an electrical stimulus called electrical cardioversion that restores normal rhythm. Ventricular fibrillation is a medical emergency in which the contractions of the heart's ventricles are so inefficient that the heart virtually stops pumping blood. There is immediate loss of consciousness and pulse.
Death occurs within minutes unless there is emergency intervention.
Ventricular fibrillation has been associated with coronary artery disease, alcohol and cocaine consumption and exercise. But often no cause is found. It is the leading cause of death in young and middle-aged men. If your doctor suspects an arrhythmia, you should have an ECG-an electrocardiogram. If the arrhythmia is intermittent, you may be given a Holter monitor, a portable ECG machine that records your heart rate during your daily activities.