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.
As time goes on, less and less oxygen makes it to the heart, which can cause a heart attack. Coronary artery disease can lead to heart failure and arrhythmias (irregular heart beats). While some people are genetically predisposed to heart disease, it often develops due to poor lifestyle habits.