Ventricular fibrillation (VF) is a life-threatening heart rhythm disturbance and the most common cause of sudden cardiac arrest. Instead of contracting in a coordinated sequence, the ventricles (the heart’s lower pumping chambers) produce rapid, chaotic electrical signals that cause the muscle fibres to quiver rather than pump. The result is an immediate and complete loss of cardiac output: no blood reaches the brain or vital organs.
In a normal heartbeat, an orderly electrical impulse travels through the heart and triggers a single, coordinated contraction. In VF, hundreds of disordered impulses fire simultaneously, making effective contraction impossible. Within seconds the person loses consciousness. Without treatment, irreversible brain damage begins in around four to six minutes, and death follows shortly afterwards.
The only effective treatment for VF is defibrillation: a controlled electric shock delivered by a defibrillator (AED or in-hospital device) that resets the heart’s electrical system and allows a normal rhythm to resume. CPR does not correct VF but sustains a small amount of blood flow to the brain, buying critical time until a defibrillator is available. Survival rates fall by approximately 10% for every minute that defibrillation is delayed.
VF most commonly occurs in people with underlying heart disease, including coronary artery disease, dilated cardiomyopathy, hypertrophic cardiomyopathy, and inherited electrical conditions such as Long QT syndrome or Brugada syndrome. In some survivors no structural or electrical cause is identified; this is known as idiopathic ventricular fibrillation. After a VF-related cardiac arrest, an ICD is recommended for most survivors, as it monitors heart rhythm continuously and delivers an automatic shock if VF recurs.
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