ABC | Volume 114, Nº2, February 2020

Update Update of the Brazilian Guideline on Nuclear Cardiology – 2020 Arq Bras Cardiol. 2020; 114(2):325-429 Figure 57 – Male patient, age 65, with pacemaker implant 4 months prior (removed due to subcutaneous pocket infection); new implantation with the distal end of the right chambers. He evolved with dyspnea and fever 20 days prior; blood culture was positive for S. aureus. FDG- 18 F - PET/CT study was positive for endocarditis in the implant site; maximum standard uptake value (SUV) = 8.1. Source: INCOR, FMUSP, SP. infections, but it is less reliable for diagnosing infections in the metallic device. 410,411 The presence of a focal hotspot is considered the best criterion for infection, 412 (Figures 57 and 58). It is worth noting that exam accuracy depends on patient preparation and post-implant interval, which is the case with applications involving FDG- 18 F. Mild FDG- 18 F uptake has been reported to be nonspecific in patients with CIED or pacemaker with no suspicion of acute-phase infection (≤ 2 months) following cardiac surgery. 410 Moreover, attenuation correction artifacts due to metallic implants should be avoided by means of close evaluation of images without attenuation correction. Both FDG- 18 F - PET/CT and scintigraphy with marked leukocytes via SPECT/CT seem to be beneficial in diagnosing infections related to ventricular assist devices (VAD). 413,414 FDG- 18 F - PET/CT is especially sensitive to infection in these devices. In a small retrospective study, sensitivity to VAD infection was 100%, and specificity was 80%. Furthermore, in 85% of cases, PET imaging had an impact on clinical management of patients. 415 The role of FDG- 18 F - PET/CT in investigating extracardiac complications of infection was also studied. In a retrospective analysis of patients with suspected CIED infection, the performance of full body PET also identified septic embolism or infection disseminated into other sites in 28% of cases. 416 These results were confirmed in a prospective study on known device endocarditis. 417 In this cohort, FDG- 18 F - PET/CT found septic embolism in 10 patients (29%), including 7 cases of spondylodiscitis, 4 of which were not clinically visible and which resulted in significant modifications to therapy. Guided myocardial biopsy may be another application of FDG- 18 F - PET/CT, as shown in other diseases. 418 Furthermore, MR and PET/CT seem to be complementary in nature. 419 Investigation of the incremental value of PET/MR, a new integrated imaging modality, may have great potential for diagnosing endocarditis. 14.3. Myocarditis The most common causes of myocarditis are viral infections. Other causes include other types of infections, autoimmune disorders, or drug interactions. Clinical manifestations of myocarditis are highly variable, ranging from subclinical disease to sudden death. This spectrum also reflects the extent to which this histological disease’s severity, etiology, and stage of clinical presentation may vary. Inflammation of the myocardium may be focal or diffused, involving any of the cardiac chambers. Endomyocardial biopsy is currently the gold standard for diagnosis, but it has a low sensitivity (20-30%) and significant associated risk. 420 MR is considered the imaging method of reference for non-invasive diagnosis of myocarditis, given that it allows for detection of several characteristics such as inflammatory hyperemia and edema, necrosis, and myocardial scarring, alterations in ventricular size and geometry, regional and global abnormalities in the movement of walls, and identification of pericardial effusion. 421 MR criteria for diagnosis of myocarditis have been summarized in what are known as the Lake Louise Criteria. 422 MR, however, has limitations that are particularly evident in chronic myocarditis, with low diagnostic precision (50% accuracy). 423 406