Valves previously affected by rheumatic fever and other valve diseases are thick, rough, and swollen. Bacteria that gain entry into the bloodstream on their way through the heart may attach to the roughened valve surface and set up an area of infection. This bacteria may grow to form an ‘‘abscess’’ on the valve. The abscess resembles a clump of moss that swings and sways on the valve leaflet as it opens and closes.
Infection of the heart valves is called infective or bacterial endocarditis. Usually the infection is by bacteria, thus the term bacterial endocarditis, but infections caused by fungi, Coxiella, or chlamydiae can occur, thus the term infective endocarditis is used by many physicians. Infection nay involve heart valves not previously known to be abnormal such as a bicuspid aortic valve, mitral valve prolapse, and rarely a septal defect or ventricular aneu-rysm. Coarctation of the aorta, patent ductus arteriosus, aneurysms, or arteriovenous shunts may be the sites of infective endocarditis. Prosthetic heart valves may be involved and infection at the site of implantation of foreign material may pose a particularly difficult problem.
In susceptible individuals, bacterial endocarditis can begin weeks or months after simple manipulations such as scaling and cleaning of teeth, other dental work, and surgery in areas of the body where infection may gain access. Patients who have mild heart valve lesions but can normally live a normal life to beyond age 80 may have their lives suddenly shortened by this infection.

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