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.
Coronary heart disease. Coronary heart disease (CHD) is the leading cause of heart attacks. CHD is a condition in which the coronary arteries (the major blood vessels that supply the heart with blood) get clogged up with deposits of cholesterol. These deposits are called plaques.
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.