A cardiac arrest is the sudden cessation of normal circulation of the blood when the heart stops beating. The heart stops pumping blood. It is different from a heart attack where blood flow to the heart is blocked but the heart usually continues to beat. Stopped blood circulation prevents oxygen delivery to different parts of the body. Decreased blood supply to the brain causes loss of consciousness and abnormal or absent breathing. Lack of treatment can result in brain damage and ultimately, death.
Cardiac arrest is a medical emergency. It can be reversed if treated early enough. Cardiopulmonary resuscitation (CPR) to restart blood circulation followed by defibrillation (giving an electric shock) to restart the natural cardiac pacemaker is the usual procedure to deal with cardiac arrests.
The most common cause of cardiac arrest is uncoordinated contraction of muscle of the lower chambers (ventricular fibrillation). Other causes include include coronary heart disease, enlarged heart, congenital heart disease physical stress, etc.