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.
Heart attack - Causes. Heart attacks are caused by the blood supply to the heart being suddenly interrupted. Without this supply, heart muscles may be damaged and begin to die. Without treatment, the heart muscles will experience irreversible damage.
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.