(See also Overview of Arrhythmias.)
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 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.