To understand coronary artery disease (CAD), you need to know how your heart works. Your heart is a muscle that pumps blood throughout your body. To work right, your heart needs a steady supply of oxygen. It gets this oxygen from blood supplied by the coronary arteries.
Healthy artery. When a coronary artery is healthy and has no blockages, blood flows through easily. Healthy arteries can easily supply the oxygen-rich blood your heart needs.
Damaged artery. Coronary artery disease begins when damage to the artery lining leads to the buildup of fat-like substances and cholesterol along the artery wall. This is called plaque. This damage could be caused by conditions like high blood pressure, high blood sugar, or smoking. This plaque buildup begins to narrow the arteries carrying blood to the heart. This is called atherosclerosis,
Narrowed artery. As more plaque builds up, your artery has trouble supplying blood to your heart muscle when it needs it most, such as during exercise. You may not feel any symptoms when this happens. Or you may feel angina—pressure, tightness, achiness, or pain in your chest, jaw, neck, back, or arm.
Blocked artery. A piece of plaque may break off and completely block the artery. Or, more commonly,a blood clot may form on a ruptured plaque and plug the narrowed artery. When this happens, blood flow is blocked from reaching the heart. Without oxygen-rich blood, part of the heart muscle becomes damaged and stops working. You may feel crushing pressure or pain in or around your chest. This is a heart attack (acute myocardial infarction, or AMI) and is a medical emergency.