Pre-Algebra on Khan Academy: No way, this isn't your run of the mill arithmetic. This is Pre-algebra. You're about to play with the professionals. Think of pre-algebra as a runway.
Heart attack - Causes. Heart attacks are caused by the blood supply to the heart being suddenly interrupted. Without this supply, heart muscles may be damaged and begin to die. Without treatment, the heart muscles will experience irreversible damage.
Atherosclerosis is the usual cause of heart attacks, strokes, and peripheral vascular disease -- what together are called  cardiovascular disease .. Cardiovascular disease is the No. 1 killer in America, with more than 800,000 deaths in 2005. Coronary artery disease: Stable plaques in the heart's arteries cause angina (chest pain on exertion). 2  Sudden plaque rupture and clotting causes heart muscle to die. 3  This is a heart attack, or myocardial infarction.