Sudden cardiac death (SCD) is a rapid, unexpected death due to cardiac causes. The differential diagnosis includes diseases from all four structural divisions of the heart: the blood vessels, myocardium, valves, and conduction system. Although ischemic heart disease is a common cause of SCD, acute myocardial infarcts and/or coronary thromboses are not always detected and are not required to make the diagnosis of death due to atherosclerotic coronary disease. Some people die suddenly from heart disease with a grossly and microscopically normal heart. Molecular analysis of some of these autopsy-negative, sudden unexplained deaths (SUD) may detect putative cardiac channel mutations.