Right ventricular (18)F-FDG uptake is an important indicator for cardiac involvement in patients with suspected cardiac sarcoidosis.

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Cardiac sarcoidosis is most commonly found in the left ventricular (LV) free wall. Presence in the right ventricle (RV) is less common but might be useful for detecting cardiac involvement of sarcoidosis. (18)F-fluorodeoxyglucose ((18)F-FDG) PET has been used to detect LV regions with cardiac sarcoidosis. However, the same has not been done for RV involvement. The aims of the current study were to evaluate RV (18)F-FDG uptake and its relationship to the distribution of LV wall (18)F-FDG-positive segments in the LV, and to evaluate whether patients with positive RV (18)F-FDG uptake met the 1993 diagnostic criteria of the Japanese Ministry of Health and Welfare (JMHW) guidelines regarding sarcoidosis with suspected cardiac involvement. Fifty-nine biopsy-proven extra-cardiac sarcoidosis patients (age 56.1 ± 14.7 years) with suspected cardiac involvement based on abnormal electrocardiography or echocardiography findings underwent fasting (18)F-FDG PET or PET/CT. The LV wall was divided into 17 segments and RV uptake was also evaluated. Among 59 patients, 35 (59.3%) showed some abnormal (18)F-FDG uptake in the RV and/or LV wall. With respect to the RV wall, 13 (22.0%) showed abnormal (18)F-FDG uptake. The number of LV-involved segments was 4.8 ± 2.4 in the patients with RV (18)F-FDG uptake, which was significantly higher than in the patients without RV uptake, 1.8 ± 2.2 (P < 0.0001). Patients with RV uptake more frequently met the diagnostic criteria of the 1993 JMHW guidelines (n = 27), than did those without RV uptake (84.6 vs. 34.8%, P = 0.0033). (18)F-FDG PET identified RV involvement less frequently than LV involvement in this study population. However, patients who had RV uptake showed a greater number of LV-involved segments and met the JMHW diagnostic criteria more frequently. Although RV uptake is less frequent, (18)F-FDG RV uptake may be useful in diagnosing cardiac involvement in sarcoidosis. UMIN000006533.