heart disease, any of several abnormalities of the heart and its function in maintaining blood circulation. Heart disease is the cause of approximately half the deaths in the United States each year. Among the most common causes of heart disease are degenerative changes in the coronary blood vessels, infectious diseases, and congenital heart disease. Congenital defects result from abnormal development of the fetal heart, commonly in the valves or septa. Such defects can be precipitated by environmental conditions in the uterus, such as the presence of the rubella virus, or they can be inherited. Infectious diseases acquired after birth, such as rheumatic fever, syphilis, and endocarditis, can also damage the valves of the heart. In addition, the heart muscle itself can be affected: hypertensive heart disease (see hypertension) can cause it to enlarge, and it can become inflamed by rheumatic fever. Arteriosclerotic depositions in the coronary arteries result in the narrowing of these vessels, causing insufficient blood flow and oxygen to the heart muscle, a condition known as coronary artery disease. The characteristic radiating chest pain, angina pectoris, is the most prominent symptom of this condition. Coronary arteries already narrowed by arteriosclerosis are made susceptible to blockage by a clot (coronary thrombosis), causing the death of the heart muscle supplied by the affected artery, a life-threatening event called a myocardial infarction, or heart attack. Hypertensive, coronary, congenital, and other forms of cardiovascular disease, either singly or in combination, can lead to a state in which the heart is unable to expel sufficient blood for the metabolic demands of the body, ultimately resulting in congestive heart failure. Disturbances in the normal heartbeat, called arrhythmias, can occur by themselves or in conjunction with other heart problems, for example infarction affecting the area of the heart that controls the heartbeat.

coronary heart disease: see coronary artery disease.

congenital heart disease, any defect in the heart present at birth. There is evidence that some congenital heart defects are inherited, but the cause of most cases is unknown. One known cause is infection of the mother with the rubella (German measles) virus during the first trimester of pregnancy. Among the most common congenital heart disorders are malformations in the valves and the persistence of structures that are normally closed off at birth, i.e., the ductus arteriosis (the fetal blood vessel that shunts blood from the pulmonary vein to the aorta, bypassing the heart) and the foramen ovale (the opening between the left and right atria of the fetal heart). If the malformation is severe, it will produce various symptoms of insufficient heart function, such as cyanosis (a bluish tinge to the skin), dyspnea (difficulty in breathing), fatigue, and abnormal heartbeat; valvular deformities predispose the patient to bacterial infection of the endocardium (see endocarditis). Less severe malformations may not produce noticeable symptoms until later in life, and some may not require any medical attention. Many congenital heart defects that are debilitating can be corrected surgically. Other congenital anomalies, such as Down syndrome, are present in about 20% of cases of congenital heart disease. See also heart disease.

or ischemic heart disease

Progressive reduction of blood supply to the heart muscle due to narrowing or blocking of a coronary artery (see atherosclerosis). Short-term oxygen deprivation can cause angina pectoris. Long-term, severe oxygen depletion causes a heart attack. Coronary bypass or angioplasty is needed if medication and diet do not control the disease.

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Deformity of the heart. Examples include septal defect (opening in the septum between the sides of the heart), atresia (absence) or stenosis (narrowing) of one or more valves, tetralogy of Fallot (with four components: ventricular septal defect, pulmonary valve stenosis, right ventricular enlargement, and positioning of the aorta so that it receives blood from both ventricles), and transposition of the great vessels (so the pulmonary and systemic circulations each receive blood from the wrong side of the heart). Such defects can prevent enough oxygen from reaching the tissues, so the skin has a bluish cast. Many are fatal if not corrected surgically soon after birth—or, rarely, before birth, if detected prenatally. Abnormalities of the large vessels are usually less serious (see aorta, coarctation of; ductus arteriosus).

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