Merck Manual

Please confirm that you are a health care professional

honeypot link

Ventricular Fibrillation (VF)


L. Brent Mitchell

, MD, Libin Cardiovascular Institute of Alberta, University of Calgary

Last full review/revision Jan 2021| Content last modified Jan 2021
Click here for Patient Education
Topic Resources

Ventricular fibrillation causes uncoordinated quivering of the ventricle with no useful contractions. It causes immediate syncope and death within minutes. Treatment is with cardiopulmonary resuscitation, including immediate defibrillation.

Ventricular fibrillation (VF) is due to multiple wavelet reentrant electrical activity and is manifested on electrocardiogram (ECG) by ultrarapid baseline undulations that are irregular in timing and morphology.

VF is the presenting rhythm for about 70% of patients in cardiac arrest and is thus the terminal event in many disorders. Overall, most patients with VF have an underlying heart disorder (typically ischemic cardiomyopathy, but also hypertrophic or dilated cardiomyopathies, arrhythmogenic right ventricular dysplasia [ARVD], or Brugada syndrome). Risk of VF in any disorder is increased by electrolyte abnormalities, acidosis, hypoxemia, or ischemia.

Ventricular fibrillation is much less common among infants and children, in whom asystole is the more common presentation of cardiac arrest.

Treatment of Ventricular Fibrillation

  • Defibrillation

  • Implantable cardioverter-defibrillator

Treatment of ventricular fibrillation is with cardiopulmonary resuscitation, including defibrillation. The success rate for immediate (within 3 minutes) defibrillation is about 95%, provided that overwhelming pump failure does not preexist. When it does, even immediate defibrillation is only 30% successful, and most resuscitated patients die of pump failure before hospital discharge.

Patients who have VF without a reversible or transient cause are at high risk of future VF events and of sudden death. Most of these patients require an implantable cardioverter-defibrillator; many require concomitant antiarrhythmic drugs to reduce the frequency of subsequent episodes of ventricular tachycardia and VF.

Click here for Patient Education
NOTE: This is the Professional Version. CONSUMERS: Click here for the Consumer Version
Professionals also read

Test your knowledge

Cardiac Catherization
Cardiac catheterization of the left or the right heart can be used to do various tests, and it also can be used to determine appropriate therapeutic interventions. Right heart catheterization is most commonly used to assess which of the following? 
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID

Also of Interest