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. 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 .