Atherosclerosis is an aging process, which results in the hardening of arteries due to the deposition of cholesterol, lipids, blood cells etc. On the inner side of an artery. This is an age-related process. In this, the arteries harden and narrow. The process begins in early childhood in everyone, but progresses slowly in some people and rapidly in the others. When this happens within the coronary arteries, the person is at risk of a heart attack.
Gradually these fatty plaques grow; the lumen, the space inside a tubular structure of the coronary arteries, becomes narrow and the heart does not get enough blood. The patient experiences chest pain and discomfort. This is called Angina Pectoris. In the beginning the pain is present only on exertion such as carrying loads or climbing up steps. Later it may occur even while resting.
Atherosclerosis gradually progresses and the lumen of the artery further narrows. When the narrowed lumen is completely blocked by further deposition of atheromatous (patchy) plaques or by a blood clot, the patient suffers a heart attack.