VenticularFibrillation

Ventricular fibrillation occurs when parts of the ventricles depolarize repeatedly in an erratic, uncoordinated manner. The EKG in ventricular fibrillation shows random, apparently unrelated waves. Usually, there is no recognizable QRS complex.

The EKG on the top shows normal sinus rhythm. The EKG at the bottom shows ventricular fibrillation

Ventricular fibrillation is almost invariably fatal because the uncoordinated contractions of ventricular myocardium result in ineffective pumping and little or no blood flow to the body. There is lack of a pulse and pulse pressure and the patients lose unconsciousness rapidly. When the patient has no pulse and respiration the patient is said to be in cardiac arrest. A person in cardiac arrest must receive CPR immediately.

Electrical defibrillation, by passage of current at high voltage, may be successful in restoration of a normal regular rhythm. The electrical current stimulates each myocardial cell to depolarize simultaneously. Following synchronous repolarization of all ventricular cells, the SA node assumes the role of pacemaker and the ventricular myocardial cells can resume the essentially simultaneous depolarization of normal sinus rhythm.

Ventricular fibrillation is associated with drug toxicity, electrocution, drowning and myocardial infarction.

Last Updated: 01/03/00.
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