Coronary artery disease (CAD) is a condition characterized by the narrowing or blockage of the coronary arteries, which supply blood and oxygen to the heart muscle. This narrowing or blockage is typically caused by the buildup of plaque, consisting of cholesterol, fatty substances, and other materials. CAD can lead to reduced blood flow to the heart, resulting in chest pain (angina), shortness of breath, and an increased risk of heart attack.