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.
The main event of a heart attack is the occlusion by a sudden blood clot of one or more blood vessels supplying the heart muscle. A similar occlusion of blood vessels supplying the brain will result in the death of brain tissue or cerebral infarction. Another cause of stroke is hemorrhage from a ruptured blood vessel.