One of the two life threatening cardiac arrhythmias (the other is asystole, absence of a heartbeat) that arise in cardiac arrest. The heart has rapid, ineffective, uncoordinated contractions and does not pump blood. The problem is caused by abnormal heartbeats initiated by electrical activity in the ventricles (lower heart chambers). It is a frequent complication of myocardial infarction (heart attack) and can also be caused by drowning or electrocution.
The diagnosis is confirmed by ECG. Emergency medical treatment is with defibrillation (administration of an electric shock to the heart) and antiarrhythmic drugs.