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 artery disease. The most common underlying cause of heart attack is atherosclerosis, a condition in which a fatty substance called plaque builds up on the inside walls of blood vessels. When this occurs in the coronary arteries, it's known as coronary artery disease (CAD).
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.