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).
1 A heart attack results when a blood clot completely obstructs a coronary artery supplying blood to the heart muscle and heart muscle dies.  The blood clot that causes the heart attack usually forms at the site of rupture of an atherosclerotic, cholesterol plaque on the inner wall of a coronary artery.