The most common cause of a heart that hurts when breathing is due to acute pericarditis, which is a more common condition that can coexist with myocarditis and endocarditis. Causes of the development of acute pericarditis can include infectious factors, as well as tuberculosis, tumors, connective tissue disease, and metabolic diseases. In patients with coronary artery disease, acute pericarditis may also develop after acute myocardial infarction. The typical symptom of acute pericarditis is chest pain, which can be aggravated by changes in position, as well as by breathing and exercise. The pain may be appropriately relieved by a change in position, such as in the anterior tilt position. Patients with acute pericarditis may develop pericardial effusion. For rapid onset of pericardial effusion and large amount of pericardial effusion, it may cause cardiac tamponade and lead to cardiac tamponade triad, which requires emergency pericardial aspiration if necessary.