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 insuffici