Breathing difficulty originating in the heart rather than the lungs or air passages, characteristically occurring at night. It is caused by failure of the left side of the heart because of abnormalities of the aortic or mitral valve, or after a coronary infarction. The heart cannot pump blood away from the lungs rapidly enough and it accumulates there. By day this causes little or no discomfort, but at night the sleeping posture brings more blood into circulation from the legs, and even a small increase in the quantity of blood in the lungs can cause an attack. Because not enough oxygen can be taken from the lungs, cyanosis sets in. A cardiac asthma attack can endanger life and must be treated promptly by the administration of oxygen and medication: rapidly effective diuretics, digitalis and morphine.