When a coronary artery is narrowed, myocardial distress may result from lack of oxygen in the blood. This illness is called angina pectoris, and is the first reversible sign of cardiac circulation problems. Though angina attacks usually decrease with only slight damage to the heart, episodes of myocardial hypoxia (lack of blood flow), which produce the angina, may lead to severe consequences if they are not addressed and treated. Prolonged or severe angina attacks may lead to a heart attack.

The most common cause of angina is atherosclerosis. This illness can cause a gradual obstruction due to the deposit of lipids, or fatty deposits, inside the arteries. Such damage may cause temporary chest pain, with a feeling of pressure or simply a sensation of discomfort. Often angina pectoris is mistaken for indigestion or for nonspecific pains. Due to such a broad variation in symptoms its diagnosis is not always easy, even though the disease is common:  over 6 million Americans suffer from angina and every year about half a million new cases occur.