Heart attack

Plaques inside the coronary arteries sometimes break open or "rupture." This is what causes most heart attacks. When a plaque breaks open, it causes a blood clot to form inside the artery. As the clot grows, it can completely block off the flow of blood through the artery. That means that the tissue on the other end of the clogged artery does not get the blood and oxygen it needs, so it gets damaged or dies.