Coronary artery disease results from the narrowing of the internal diameter of the coronary arteries. The process is called atherosclerosis. This limits the blood supply to heart, so that oxygen supply cannot match the oxygen demand of the heart. 

Atherosclerosis is the underlying cause of coronary artery disease. This results from the build up of fatty deposits inside the arterial wall over many years. Endothelial inflammation and injury, as well as the plaque buildup with lipids, macrophages, foam cells and collagen play an important part of this process.