Arteriosclerosis is a general term for the thickening and hardening of arteries as a result of cholesterol deposits in their walls. Arteriosclerosis in the coronary arteries reduces the amount of blood that reaches and nourishes the muscle of the heart. Blocked arteries, even if they’re only partially blocked, may not provide enough oxygen and nutrients to the heart muscle. At first, a person may only notice this when he or she increases their physical activity. Climbing stairs, for example, requires additional work by the legs. The heart has to pump harder and faster to meet the increased demand for oxygen by the leg muscles. In patients with Coronary Artery Disease (CAD), the heart needs more oxygen than it can get through the narrowed arteries. When the blockage becomes more severe, the inadequate supply of oxygen is often sensed as chest pain. Eventually, the patient may experience pain with minimal activity or potentially experience a heart attack.