Inflammation of the lining, valves and muscle of the heart. The main causes are bacterial and virus infections and rheumatic fever, and the condition occurs most often in patients whose ENDOCARDIUM is already damaged by congenital deformities or whose immune system has been suppressed by drugs. Infection may be introduced into the bloodstream during dental treatment or surgical procedures, especially on the heart or on the gastrointestinal system. Persons with congenital heart valve disease are advised to take an antibiotic at the time of dental and certain other surgery. The condition is potentially very serious and treatment of bacterial endocarditis is with large doses of antibiotic drugs over a prolonged period. (See HEART, DISEASES OF.)