The term Sudden Cardiac Death refers to natural death from cardiac causes, heralded by abrupt loss of consciousness within one hour of the onset of acute symptoms Myerburg, Robert J. "Cardiac Arrest and Sudden Cardiac Death" in Heart Disease: A Textbook of Cardiovascular Medicine, 7th ed., WB Saunders, Philadelphia, PA, 2005..

It is important to make a distinction between this term and the related term cardiac arrest, which refers to cessation of cardiac pump function which may be reversible (i.e., may not be fatal). The phrase Sudden Cardiac Death is a public health concept incorporating the features of natural, rapid, and unexpected. It does not specifically refer to the mechanism or cause of death. Although the most frequent underlying cause of Sudden Cardiac Death is Coronary Artery Disease, other categories of causes include:

• Non-atherosclerotic coronary artery abnormalities
• Hypertrophy of ventricular myocardium
• Myocardial diseases and heart failure
• Inflammatory, infiltrative, neoplastic, and degenerative processes
• Diseases of the cardiac valves
• Congenital heart disease
• Primary electrophysiological abnormalities
• Rhythm instability related to neurohumoral and central nervous system influences
• Sudden infant death syndrome and sudden death in children
• Commotio cordis
• Mechanical interference with venous return
• Aortic dissection
• Toxic/metabolic disturbances

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