SCA can result from cardiac causes (abnormalities of the heart muscle or the hearts electrical system), external causes (drowning, trauma, asphyxia, electrocution, drug overdose, blows to the chest), and other medical causes such as inflammation of the heart muscle due to infection. Most SCAs are caused by an abnormal heart rhythm (arrhythmia). The most common life-threatening arrhythmia is ventricular fibrillation, which is an erratic, disorganized firing of impulses from the ventricles (the hearts lower chambers). When this occurs, the heart is unable to pump blood and death will occur within minutes if left untreated. Heart attacks can also lead to SCA.
