It doesn't restart a stopped heart — it does something more specific.
When a heart stops pumping, it is usually in a state called ventricular fibrillation. This means the heart muscle is quivering rapidly and chaotically instead of beating in a coordinated rhythm. Blood cannot circulate to your brain or organs during this time. The heart is still electrically active, but that activity is disorganized and ineffective.
A defibrillator does not restart a heart that has already flatlined into a straight line on a monitor. Instead, it delivers a high-energy electric shock to the heart muscle to stop the chaotic quivering. The goal is to wipe the slate clean for the heart's natural electrical pacemaker. This allows the heart to hopefully resume a normal, steady rhythm on its own.
Every minute that passes in ventricular fibrillation significantly lowers the chances of a successful recovery. We use a defibrillator to intervene as fast as possible to prevent permanent damage to your vital organs. Speed is essential because the heart muscle loses its ability to respond to electrical signals the longer it remains in a chaotic state.
A clinician places adhesive pads on your chest to monitor your cardiac rhythm. If the machine detects a shockable rhythm, we clear the area to ensure safety for everyone nearby. One shock is delivered, and we immediately return to checking your pulse and performing chest compressions if necessary. We continue this cycle until the heart is beating effectively again.