Sudden cardiac death (also called sudden cardiac arrest) is a death resulting from an abrupt loss of heart function (cardiac arrest). The victim may or may not have been diagnosed with heart disease previously. The time and mode of death are unexpected. It occurs within minutes after symptoms appear. The most common underlying reason for patients to die suddenly from cardiac arrest is coronary artery disease.
All known heart diseased can lead to cardiac arrest and sudden cardiac death. Most of the cardiac arrests that lead to sudden death occur when the electrical impulses in the diseased heart become rapid and/or chaotic or both such as ventricular tachycardia, or ventricular fibrillation. Some cardiac arrests are due to extreme slowing of the heartbeat called bradycardia.
The term "massive heart attack" is often wrongly used in the media to describe sudden death. The term "heart attack" refers to death of heart muscle tissue due to the loss of blood supply, not necessarily resulting in a cardiac arrest of the death of the heart attack victim. A heart attack may cause cardiac arrest and sudden cardiac death, but the terms are not synonymous.
Brain death and permanent death start to occur in just four to six minutes after someone experiences cardiac arrest. Cardiac arrest is reversible in most victims if it is treated within a few minutes with an electric shock to the heart to restore normal heart beating. This process is called defibrillation. Few attempts succeed after 10 minutes. If someone becomes unconscious, call 9-1-1 immediately.