Cardiovascular disease comprises disorders of the heart and blood vessels; it includes strokes. The disorders are varied. In 1950 the National Heart Institute considered the term heart disease to include over twenty cardiovascular maladies, and it concentrated its efforts on the three types of heart disease that caused 90 percent of the deaths— rheumatic heart, hypertension or high blood pressure, and atherosclerosis, also called hardening of the arteries. Sometimes heart disease is inherited or caused by another illness, such as rheumatic fever; other times it is caused by lifestyle, particu-., larly poor habits regarding diet, stress, exercise, and weight control. During the 1950s researchers pointed put that smoking contributes significantly to the risk of cardiovascular disease.

A major category of cardiovascular diseases includes those that stem from the inability of vessels to deliver blood to parts of the body. When the defective vessels...