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.
Both heart attack and heart failure are serious medical conditions that can cause death. Heart attack is caused by sudden total clogging of an artery that gives blood to the heart muscle. This kills part of the muscle of the heart, which weakens the heart. Heart failure occurs when the heart cannot circulate blood through the body.