We aim to support communities by providing public access defibrillators which are available 24/7. Thames Valley Heartbeat also provides free confidence building familiarisation sessions on CPR and the use of a defibrillator. Cardiac arrest is a leading cause of premature death, but with immediate treatment, many lives can be saved. The heart stops because the electrical rhythm that controls the heart is replaced by a disorganised electrical rhythm. The quicker this can be treated, the greater the chance of successful resuscitation. Cardiac arrest can be reversible, but it is vital it is recognised and acted upon in the first few seconds or minutes. Lives can be saved by CPR and the use of a defibrillator.