Ventricular Fibrillation

Background

• 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)

Aetiology

• 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

Presentation

• 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)

Management

• 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.

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