Sudden cardiac arrest is the leading cause of death in adults. Most arrests occur in persons with underlying heart disease.

CPR, invented in 1960, doubles a person's chance of survival from sudden cardiac arrest.

In sudden cardiac arrest the heart goes from a normal heartbeat to a quivering rhythm called ventricular fibrillation. VF is fatal unless an electric shock, called defibrillation, can be given. CPR does not stop VF but provides a trickle of oxygenated blood to the brain and heart and keeps these organs alive until defibrillation can shock the heart into a normal rhythm.

If CPR is started within 4 minutes of collapse and defibrillation provided within 10 minutes a person has a 40% chance of survival.