ABC | Volume 114, Nº2, February 2020

Update Update of the Brazilian Guideline on Nuclear Cardiology – 2020 Arq Bras Cardiol. 2020; 114(2):325-429 include clinical, microbiological, and echocardiography findings, resulting in a general sensitivity around 80%. 395 Some limitations, however, stand out, especially in patients with prosthetic valves (PV) and cardiac implantable electronic devices (CIED), 396 implying inadequate classification of up to 24%of patients with proven IE. 395 Advanced imaging techniques for early, sensitive diagnosis of IE are, in fact, valuable tools in clinical practice. The combination of both evaluation of myocardial metabolism of glucose via PET/CT using a glucose analogue labeled with 18 F, fluorodeoxyglucose (FDG) (FDG- 18 F - PET/CT), and modified Duke criteria resulted in increased sensitivity, without large alterations in specificity. 397 Although FDG- 18 F - PET/CT is not reliable for evaluation of native valve endocarditis, 398 it may accurately diagnose endocarditis in valve prostheses and its systemic complications. 399 In recognition of its utility, FDG- 18 F - PET/CT was included in the European Society of Cardiology Guidelines, in 2015, as a diagnostic criterion (class of recommendation IIb) for IE in patients with valve prostheses. 400 One option for further improving FDG- 18 F - PET/CT imaging is the incorporation of angio-CT (PET/angio-CT), resulting in sensitivity, specificity, positive predictive value, and negative predictive values of 91%, 91%, 93%, and 88%, respectively. 401 As a more specific alternative to FDG- 18 F - PET/CT, guidelines on IE include scintigraphy using marked leukocytes with SPECT/CT imaging. SPECT/CT is the combination of nuclear medicine tomography imaging (SPECT) and anatomical imaging via CT, greatly increasing diagnostic accuracy. However, notwithstanding the proven value of this technique for detecting endocarditis 402,403 (Figure 56), its widespread application is compromised due to limited sensitivity and the difficulty of locating inflammatory foci, but the very high specificity of scintigraphy with marked leukocytes for infection, when using SPECT/CT imaging, may be particularly useful in cases where diagnosis remains uncertain following echocardiography and FDG- 18 F - PET/CT, especially in patients who have undergone cardiac surgery over the past 2 months. 404-407 As an additional possibility, the simultaneous combination of scintigraphy with marked leukocytes and MPS, acquired to improve localization of infectious points in relation to the valve plane defined by perfusion. Limitations to performing SPECT/CT with marked leukocytes are: the need for a specific structure with laminar flow, the manipulation of blood components, procedure duration, and inferior spatial resolution in relation to PET/CT. 400 Furthermore, new bacteria-specific tracers have become available, such as carbohydrates, which are metabolized exclusively by bacteria or antibodies directed against components of the bacterial cell membrane. For example, the protein component of the pilin structure of Enterococcus faecalis is being developed. 408 This recent study has demonstrated the superior quality of images and another possibility for differentiating between infectious and inflammatory causes of endocarditis. CIED have been increasingly used over recent years, 400 with elevated rates of infection (1% to 3%), and they are associated with 1-year mortality over 10%. 409 Doppler echocardiography is the first line imaging method for evaluation of suspected CIED infection, but its use is limited for investigating infection in extra-cardiac leads and device pockets. Both FDG- 18 F - PET/ CT and SPECT/CT scintigraphy with marked leukocytes have demonstrated additional value for diagnosis of infections related to CIED or pacemaker. FDG- 18 F - PET/CT has been shown to be especially useful for diagnosing device pocket Figure 56 – Images from scintigraphy with labeledleukocytes with SPECT/CT demonstrate anomalous accumulation in the area of the percutaneously implanted aortic valve (arrows). Transesophageal echocardiogram was inconclusive, and blood culture was positive for Staphylococcus aureus . The patient was diagnosed with prosthetic valve infective endocarditis. Personal source (courtesy of Dr. Alan Chambi). 405