High Quality Content by WIKIPEDIA articles! Infective endocarditis is a form of endocarditis caused by infectious agents. The agents are usually bacterial, but other organisms can also be responsible. The valves of the heart do not receive any dedicated blood supply. As a result, defensive immune mechanisms (such as white blood cells) cannot directly reach the valves via the bloodstream. If an organism (such as bacteria) attaches to a valve surface and forms a vegetation, the host immune response is blunted. The lack of blood supply to the valves also has implications on treatment, since drugs also have difficulty reaching the infected valve. Normally, blood flows smoothly through these valves. If they have been damaged - from rheumatic fever, for example - the risk of bacteria attachment is increased.