What is the correlation between coronary heart disease and smoking?

Smoking is a major cause of atherosclerosis " a buildup of fatty substances in the arteries. Atherosclerosis occurs when the normal lining of the arteries deteriorates, the walls of the arteries thicken and deposits of fat and plaque block the flow of blood through the arteries. In coronary artery disease, the arteries that supply blood to the heart become severely narrowed, decreasing the supply of oxygen-rich blood to the heart, especially during times of increased activity. Extra strain on the heart may result in chest pain and other symptoms. When one or more of the coronary arteries are completely blocked, a heart attack may occur.