Angina is usually a symptom of a serious condition called coronary heart disease (CHD), also known as coronary artery disease (CAD). In coronary artery disease, the arteries of the heart become stiff and narrow, making it difficult for oxygen-rich blood to reach your heart muscle. 2,3 This lack of oxygen can cause the pain and discomfort of angina.2 Angina is your heart's way of telling you that it needs more oxygen.2,3