HAVE A HEART: The heart pumps 5.6 liters of blood through the entire body in roughly 20 seconds; each day your blood travels some 12,000 miles, and your heart beats about 100,000 times. This delivers oxygen and other essential nutrients to the body's cells and organs. A heart attack occurs when the blood supply to the heart muscle is cut off, either because part of the heart is damaged (such as the valves to the chambers), or because plaque has built up inside the arteries, narrowing them and severely restricting blood flow. Hypertrophic cardiomyopathy is a heart disease in which the heart muscle of the ventricle becomes too thick to function properly. This can lead to the most serious type of arrhythmia: ventricular fibrillation, where the lower chambers quiver and the heart can't pump any blood. This results in collapse and sudden death -- if there isn't immediate medical attention.
CPR AND DEFIBRILLATION: Cardiac arrest is the sudden, abrupt loss of heart function resulting from such factors as heart disease, electrocution, drowning, choking and trauma. Cardiopulmonary resuscitation (CPR) combines rescue breathing and chest compressions to keep victims of cardiac arrest alive until medical treatment is available. During cardiac arrest, the heart stops pumping blood; proper CPR supports a small amount of blood flow to the heart and brain to buy time until the heart begins to function normally again. If the arrest is caused by an abnormal heart rhythm, delivering an electric shock to the heart (defibrillation) can restore the normal rhythm. Some defibrillators are implanted or applied inside the body, while others are designed for use by bystanders in emergency situations.