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.
A heart attack is commonly caused by a blockage of the coronary artery. Cholesterol in the form of plaque builds up on the inside wall of the coronary artery. Over time, plaque accumulation can narrow the artery, reducing blood flow to the heart.