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).
Proof that stress really does cause heart attacks: Adrenaline can increase white blood cell production which can cause ruptures. 1  Extra white blood cells can cause inflammation in people whose arteries are already thickened with plaque.  These inflammations can lead to ruptures which can cause heart attack in minutes.