124 READINGS IN BIOLOGICAL SCIENCE 



much of the medical advice we are given regarding the protection of the 

 middle-aged healthy heart and the care of the sick heart. 



COMMON TYPES OF HEART DISEASE 



Heart disease is a convenient term used to cover a multitude of different 

 diseases, most of which are quite unrelated except as they all involve the 

 heart or blood vessels. 



1 he most common types of heart disease are those associated with in- 

 fections, especially rheumatic fever and syphilis; or with high blood pres- 

 sure; or with disease of the coronary arteries. Other less common but im- 

 portant types are caused by defects present in the heart or blood vessels 

 at birth (congenital defects), or by overactivity or underactivity of the 

 thyroid gland. 



The Young Heart 



HEART DISEASE ASSOCIATED WITH INFECTIONS 



Generally speaking, it is possible for the heart to become involved in 

 practically any infectious disease if the germs causing it or their poisons are 

 carried to the heart in the blood stream, or if the heart becomes exhausted 

 in the fight put up by the body against the disease. In these days, however, 

 very few cases of heart disease are caused by infections other than rheu- 

 matic fever and syphilis. One important reason for this is that many com- 

 municable diseases are now being prevented by immunization, or are being 

 treated successfully with serums or drugs before they have a chance to 

 infect or weaken the heart. 



Heart disease caused by an infection goes by the name of the part of 

 the heart affected, plus the ending itis, which means "inflammation of." 

 Hence we have myocarditis, inflammation of the myocardium, or heart 

 muscle; pericarditis, inflammation of the pericardium, the bag of membrane 

 enclosing the heart; aortitis, inflammation of the aorta, the great blood 

 vessel leading out of the lower left chamber of the heart; and endocarditis, 

 inflammation of the endocardium, the membrane which lines the hollow 

 heart muscle. Since the endocardium covers the valves of the heart as well 

 as its inner walls, endocarditis frequently leaves scars which may cause 

 narrowing (stenosis) of one or more valves or may interfere with their 

 proper closing. 



Rheumatic Heart Disease. Rheumatic heart disease begins nearly always 

 in childhood between the ages of 6 and 12 as the result of one or more 

 attacks of rheumatic fever. Many cases of rheumatic heart disease in adults 

 may be traced to a partly forgotten or mild attack of rheumatic fever or 

 chorea (St. Vitus's dance) in childhood. 



The cause of rheumatic fever, which plays such havoc with young 

 hearts, is not clear. The solution to the whole puzzle is now one of the chief 

 objectives of medical research. Just as a lighted match starts a fire in 



