Merits of FDG PET/CT and Functional Molecular Imaging Over Anatomic Imaging With Echocardiography and CT Angiography for the Diagnosis of Cardiac Device Infections.

The diagnosis of cardiac device infections, particularly device-related endocarditis, is challenging. Fluorine-18-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) is based on in vivo FDG targeting of the pre-existing inflammatory cells at an infectious site. Hence, it is able to identify cardiac device infection early, before the development of morphological damages from the infectious process. Transesophageal echocardiography (TEE) and electrocardiographically gated computed tomographic angiography (CTA) are currently the first-line imaging studies for device-related endocarditis, but their application to evaluate the extracardiac components or sources of primary infection and/or emboli is limited. Functional FDG PET/CT may have unique advantages over the anatomically based TEE and CT or CTA in the following settings: 1) diagnosing infection earlier than TEE and CTA, before morphological damage ensues; 2) identifying prosthetic endocarditis when findings on TEE and CTA are inconclusive; 3) evaluating infection in the extracardiac components of devices; 4) detecting unexpected source of the primary infection; and 5) discovering embolic consequences of endocarditis in the body. All of these findings may ultimately affect patient management. Although the nonspecific nature of FDG is a concern in differentiating infection from inflammation, accurate diagnosis of infection can be reasonably achieved on the basis of FDG distribution pattern and clinical history or by adding radiolabeled white blood cell scan to improve specificity. Recent publications support the judicious use of FDG PET/CT, particularly in patients with inconclusive or negative results on initial echocardiography and CT.