External defibrillation
The delivery of an electrical shock to a heart experiencing SCA briefly stops all electrical activity in the heart. This brief "break" from the previous electrical chaos can be enough for the heart to restart beating with a normal rhythm.
Not everyone can be saved from SCA - even with defibrillation. However, early defibrillation, especially when delivered within three minutes of a person's collapse from SCA, does provide the best chance.