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 may occur when: A tear in the plaque occurs. This triggers blood platelets and other substances to form a blood a clot at the site that blocks most or all of the oxygen-carrying blood from flowing to a part of the heart muscle. This is the most common cause of heart attack.