Fibrillation
Spontaneous contraction of a single muscle cell, "out of sync". If this happens to the heart, particularly the left ventricle, all heart muscle cells contract at random, resulting in the heart being mechanically unable to pump any blood at all. Ventricular fibrillation is a life threatening condition. First aid consists of cardiac compressions (regular compressions of the chest bone), but when happening in a hospital setting normal heart rhythm is usually restored by electric shock treatment called defibrillation. Ventricular fibrillation is a frequent cause of death after myocardial infarction.
GE Healthcare Glossary