FDG-positron emission tomography (PET) has high diagnostic accuracy in cardiac sarcoidosis (CS). Beyond CS, the non invasive diagnosis of inflammatory cardiomyopathies (IC) is challenged by a lower diagnostic performance of usual tools as magnetic resonance imaging (MRI).

17 consecutive patients with suspected IC had a FDG-PET to detect myocardial inflammation. From all clinical data including PET, we classified patients in either CS or non-CS and respective PET data were compared. The clinical impact of adding PET in the non-CS group was evaluated by comparing diagnosis and management proposed by an expert blind to PET with final diagnosis and management actually held in practice.

6 patients had CS, all with positive PET. In the 11 non-CS patients, 7 had a positive PET. All had MRI late gadolinium enhancement in FDG uptake areas, suggesting a true positivity of PET for the presence of inflammation. PET data were all significantly different between CS and nonCS patients with positive PET, particularly the coefficient of variation of cardiac SUV which is an index of heterogeneity of FDG uptake was significantly greater in CS patients (0,4 vs 0,17 p<0,002). In non-CS patients, 2 were classified as certain IC, 2 as excluded IC, and 7 as possible IC by an expert blind to PET. Adding PET in clinical practice, IC was excluded for 5 of the 7 patients with possible IC, 2 patients remained with a possible IC diagnosis and the 2 certain IC were confirmed. PET did not change patient management in terms of endomyocardial biopsy or immunosuppressive therapy.

Some patients with suspected IC had a positive FDG-PET in favour of myocardial inflammation, with a different pattern from that observed in CS. Adding PET to usual diagnostic tools led to a decrease of possible IC diagnosis that turned in excluded IC. These preliminary data suggest a potential role of PET for the non-invasive diagnosis of IC that will need further investigations.