Ventricular Fibrillation (VF)
Ventricular fibrillation is chaotic, disorganised ventricular electrical activity that produces no coordinated contraction, so the circulation stops and the patient is in cardiac arrest.
Definition
Ventricular fibrillation is rapid, chaotic, disorganised ventricular electrical activity with no coordinated QRS complexes, no effective ventricular contraction and therefore no cardiac output. Clinically it is a shockable cardiac arrest rhythm, recognised on the defibrillator in a patient who is unresponsive, not breathing normally and has no signs of circulation.
First principles
VF means cardiac arrest, not a fast rhythm with a pulse
Multiple disorganised wavefronts activate the ventricles at once, so there is no coordinated depolarisation and no stroke volume. The patient is unresponsive with absent or abnormal breathing and no signs of circulation. That finding, not the trace, decides the pathway: no output means the cardiac arrest algorithm, and a pulse means the peri-arrest tachyarrhythmia algorithm. A chaotic trace in a patient who is awake or has a pulse is artefact until proved otherwise.
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