Defibrillator

A defibrillator is a medical device that delivers a controlled electric shock to the heart to restore a normal cardiac rhythm in someone experiencing a life-threatening arrhythmia such as ventricular fibrillation (VF) or pulseless ventricular tachycardia (VT). These arrhythmias produce no effective pumping action; defibrillation is the only treatment that can terminate them. The shock depolarises all the heart’s electrical cells simultaneously, giving the heart’s natural pacemaker the chance to re-establish an organised rhythm.

There are three main types. An automated external defibrillator (AED) is a portable device designed for use by members of the public with minimal training. It uses voice prompts and visual instructions to guide the user, and automatically analyses the heart rhythm to determine whether a shock is appropriate. A manual defibrillator is a clinical device used by paramedics and hospital staff; it requires the operator to interpret the rhythm and decide whether to shock. An implantable cardioverter defibrillator (ICD) is a device implanted under the skin near the collarbone that continuously monitors heart rhythm and automatically delivers a shock if a dangerous arrhythmia is detected.

Defibrillation works only for shockable rhythms (VF and pulseless VT). It does not restart a heart in asystole (no electrical activity) or pulseless electrical activity (PEA). CPR is essential alongside defibrillation: it maintains blood flow to the brain between shocks and improves the likelihood that defibrillation will succeed.

For cardiac arrest survivors, the experience of being defibrillated (whether by an AED in the community or by a spontaneous ICD shock) can be both physically and psychologically significant. PTSD, anxiety, and adjustment difficulties are common after defibrillation events, and psychological support is an important part of post-arrest care.