A natural substance in the blood, cholesterol comes from the lives. The amount of cholesterol is affected by diet and by physical qualities we inherit from our parents. One kind of cholesterol sticks fat to the walls of arteries, making them smaller and finally blocking them. It produces a condition called “ hardening of the arteries,” which causes heart attacks. With tiny cameras, doctors can see blood circulating through the heart valves. Angiograms are x-rays of the heart arteries. They show fat deposits and blockages caused by high cholesterol.