Identification of Cardiac Sarcoidosis with N-NH3/F-FDG PET

To our knowledge, no study investigating the usefulness of cardiac PET for detection of myocardial involvement of sarcoidosis is available. We investigated whether N-NH3/F-FDG PET could identify cardiac involvement in patients with sarcoidosis. Methods: Seventeen patients with cardiac sarcoidosis underwent cardiac N-NH3/F-FDG PET under fasting condition. Systemic sarcoidosis was diagnosed by histologically proven noncaseating epithelioid granuloma, and cardiac sarcoidosis was diagnosed according to the Japanese Ministry of Health and Welfare guidelines for diagnosing cardiac sarcoidosis. Results: Only 6 patients exhibited myocardial 201Tl defects and only 3 patients exhibited abnormal 67Ga accumulation in the heart. Thirteen patients exhibited N-NH3 defects, and 14 patients exhibited increased 18F-FDG uptake in the heart; 12 patients exhibited both N-NH3 defects and increased 18F-FDG uptake, 2 patients exhibited increased 18F-FDG uptake but no N-NH3 defect, and 1 patient exhibited N-NH3 defects but no increased 18F-FDG uptake. N-NH3 defects were observed frequently in the basal anteroseptal wall of the left ventricle, and increased 18F-FDG uptake was observed frequently in the basal and midanteroseptal-lateral wall of the left ventricle. Involvement of the apex was rare. Seven patients were treated with steroid hormone and underwent follow-up cardiac PET 1 mo after steroid therapy. N-NH3 defects exhibited no significant change after steroid therapy, whereas increased 18F-FDG uptake was markedly diminished in size and intensity in 5 patients and disappeared completely in 2 patients. Conclusion: Our findings suggest that cardiac N-NH3/F-FDG PET is the most useful method both for the identification of cardiac involvement of sarcoidosis and for the assessment of cardiac sarcoidosis disease activity.