Nuclear medicine imaging of endocarditis.

Infective endocarditis is a serious disease which requires early diagnosis and adequate therapy. Echocardiography plays a key role in diagnosis and follow-up. Subacute infective endocarditis, however, is often difficult to prove echocardiographically due to its more subtle morphological changes. Also, echocardiography cannot reliably differentiate florid vegetations from residual structural changes of the affected valves in cured patients. Therefore, scintigraphy of infection and inflammation, a functional imaging procedure, has been investigated as a complementary tool in diagnosis and follow-up of infective endocarditis. So far, results obtained with Gallium-67 scintigraphy are not convincing, although an improvement by using modern acquisition techniques seems possible. Scintigraphy with Indium-111 labelled leukocytes has an unacceptably low sensitivity, which is probably due to the small number of cells involved and unfavourable imaging characteristics of 111In-Technetium-99m labelled leukocytes have been investigated in few patients, so final judgement is not yet possible. SPECT imaging might enhance the detectability of diseased heart valves. Immunoscintigraphy with the 99mTc labelled antigranulocyte antibody in SPECT technique is complementary to echocardiography and seems to assess the floridity of the underlying inflammatory process. The combined use of both imaging modalities allows detection of virtually all cases of subacute infective endocarditis. SPECT immunoscintigraphy with the antigranulocyte antibody seems useful in doubtful cases of infective endocarditis, especially, if echocardiography is non-diagnostic and valve pathology pre-existing. The method may be used for follow-up and monitoring antibiotic therapy.