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.
There are a few cardiac conditions that can cause heart attacks. One of the most common causes is plaque buildup in the arteries (atherosclerosis) that prevents blood from getting to the heart muscle. Heart attacks can also be caused by blood clots or a torn blood vessel. Less commonly, a heart attack is caused by a blood vessel spasm.