Ventricular fibrillation


  • Ventricular fibrillation (VF) is a life-threatening arrhythmia that causes hemodynamic collapse and if not treated promptly leads to organ damage due to organ hypoperfusion and eventually death.
  • It is vitally important to recognise VF as it is a shockable rhythm and can be treated successfully with defibrillation.
  • Patients usually lose consciousness shortly after the onset of VF. Blood pressure is unobtainable and heart sounds are not present.

Classification and ECG findings

  • VF is characterised by the presence of irregular ventricular activity varying in appearance and amplitude described as undulating baseline. P waves, QRS complexes and T waves are not present. Eventually electrical activity of the heart ceases as VF degenerates to asystole.
  • VF can be classified as coarse VF and fine VF based on the amplitude of the QRS complex. The amplitude of the QRS complex decreases over time and patients who present with fine VF therefore have worse prognosis.
  • VF can be distinguished from ventricular flutter.
  • typical ECG findings of ventricular flutter are regular large oscillations with a sine wave appearance at a rate of 150-300/min.
  • However, distinction between ventricular flutter, VF and even pulseless VT does not change the treatment as all require immediate defibrillation.


  • VF usually occurs due to mechanical or electrical disease of the myocardium, the most common cause being acute myocardial infarction.
  • Other types of arrhythmias such as Torsades de Pointes or other VTs can degenerate to VF.
  • It can rarely occur in patients without known structural heart disease - idiopathic VF.
  • Non-cardiac causes of VF include respiratory, environmental, neurological and toxic causes.
  • VF can also occur as a result of administration of some type of drugs, such as antiarrhythmic drugs or in case of non synchronised cardioversion.


  • Management of VF is part of the Basic Life Support and Advanced Life Support protocols.
  • CPR plays a vital role in management of VF and should be provided as soon as possible to sustain perfusion when a defibrillator is not available.
  • The treatment with the highest success rate is defibrillation which should be performed as soon as possible. Chances of survival depend on time from onset of VF to defibrillation and decrease by 7-10% each minute. 
  • Additional treatment options such as pharmacotherapy are part of the Advanced Life Support protocols. In case of unsuccessful defibrillation epinephrine and amiodarone administration is recommended. Detailed information is available here:

ECG 1 Ventricular fibrillation


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  4. Merchant, RM; Topjian, AA; Panchal, AR; Cheng, A; et al. (2020). Part 1: Executive summary: 2020 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care. Circulation, 142(16 Suppl 2), S337-S357. doi:10.1161/CIR.0000000000000918
  5. ERC Guidelines | Guidelines 2020 (