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 artery disease. The most common underlying cause of heart attack is atherosclerosis, a condition in which a fatty substance called plaque builds up on the inside walls of blood vessels. When this occurs in the coronary arteries, it's known as coronary artery disease (CAD).
Heart attacks are caused by coronary artery disease, the medical term for narrowing of the arteries that supply blood to the heart muscle. The narrowing of the arteries is caused by formation of a plaque on the lining of the artery (called atherosclerosis).