Ventricular Fibrillation


  • Ventricular fibrillation is one of the major causes of cardiac arrest and sudden cardiac death.
  • Coordinated contractions of the ventricles is replaces by rates of up to 500bpm, resulting in disorganised excitation and contraction, and failure of the heart to pump blood around the body.
    • Requires advanced life support and cardioversion in order for the patient to survive (see below)


  • Coronary artery disease/Myocardial infarction is the most common cause, but it can also result from other heart disease e.g. chronic ischaemic disease; cardiomyopathies; valvular disease; structural (congenital) disease of the heart
    • Ventricular tachycardia rhythm may also degenerate into VF
    • Ventricular ectopics may cause a reentry VF if they occur during the upstroke of the T wave (a risk in patients with underlying heart disease and prolonged QT syndrome)
  • Other causes include those that cause severe and acute haemodynamic collapse e.g. Pulmonary embolus, aortic aneurysm rupture/aortic dissection
  • Also electrical conduction abnormalities e.g. prolonged QT syndrome, WPWS, Brugada syndrome
  • Antiarrhythmic drugs may also cause VF


  • The patient is usually unconscious/unresponsive.
    • They may or may not be breathing, but usually do not have a pulse.

ECG appearance

  • Chaotic irregular waveforms of varying amplitude
  • No identifiable P waves, QRS complexes or T waves
  • Rate of 150-500bpm
  • Amplitude tends to decrease with duration (coarse VF initially – fine VF later)



  • Advanced life support
  • If patients survive, treatment of the underlying cause is crucial.
    • E.g. correct electrolyte disturbance, ablate accessory pathway, treat myocardial ischaemia, heart failure etc
  • Patients, if they are at risk of future attacks of VF, should be fitted with an implantable defibrillator.
  • Patients may suffer brain damage as a result of their VF.

3 thoughts on “Ventricular Fibrillation”

    1. I am working on a few other posts at the moment, but heart failure is not uncommon so I shall make sure to put that near the top of my list. Thanks

    2. Just posted one on HF- let me know if its ok or if you have any Qs. It’s a large topic 🙂

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