Angina happens when your heart muscle does not get enough oxygen-rich blood. Medical conditions, particularly ischemic heart disease, or lifestyle habits can cause angina. Angina usually happens because of heart disease. A fatty substance called plaque builds up in your arteries, blocking blood flow to your heart muscle. This forces your heart to work with less oxygen. That causes pain. You may also have blood clots in the arteries of your heart, which can cause heart attacks.

• Two types of ischemic heart disease can cause angina.

• Coronary artery disease happens when plaque builds up inside the large arteries that supply blood to the heart. This is called atherosclerosis. Plaque narrows or blocks the arteries, reducing blood flow to the heart muscle. Sometimes plaque breaks open and causes blood clots to form. Blood clots can partially or totally block the coronary arteries.

• Coronary microvascular disease affects the tiny arteries that branch off the larger coronary arteries. Reduced blood flow in these arteries causes microvascular angina. The arteries may be damaged and unable to expand as usual when the heart needs more oxygen-rich blood.

• Spasm of the coronary arteries:

A spasm that tightens your coronary arteries can cause angina. Spasms can occur whether you have ischemic heart disease and can affect large or small coronary arteries. Damage to your heart’s arteries may cause them to narrow instead of widen when the heart requires more oxygen-rich blood.

Less common causes of chest pain include:

• A blockage in a major artery of your lungs (pulmonary embolism);

• An enlarged or thickened heart (hypertrophic cardiomyopathy);

• Narrowing of a valve in the main part of your heart (aortic stenosis);

• Swelling of the sac around your heart (pericarditis);

• Tearing in the wall of your aorta, the largest artery in your body (aortic dissection).