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 can be caused by many possible factors. Your heart muscle requires a steady supply of blood and oxygen. A heart attack occurs when that supply is interrupted or blocked. The release of a blood clot from hardened coronary arteries is often the culprit. Many illnesses, as well as drugs, especially cocaine and contraceptive pill usage, can cause a heart attack.