Usefulness of heparin loading 18F-fluoro-2-deoxyglucose positron emission tomography for the diagnosis of cardiac sarcoidosis and evaluation of the response to therapy

Purpose: Heparin loading 18F-fluoro-2-deoxyglucose positron emission tomography (HL 18F-FDG PET) has advantages for the assessment of myocardial inflammation because heparin administration increases free-fatty acids (FFA), followed by shift of myocardial substrate utilization from glucose to FFA under normal conditions. Our goal was to evaluate the usefulness of HL 18F-FDG PET for the diagnosis of cardiac sarcoidosis and evaluation of the response to therapy. Methods: We screened 49 consecutive patients, who underwent HL 18F-FDG PET based on a suspicion of cardiac sarcoidosis. Five patients were diagnosed by the Japanese Ministry of Health and Welfare guidelines and showed 18F-FDG uptake on PET-CT (G(+) group). Twelve patients did not fulfill the diagnostic criteria but showed 18F-FDG uptake on PET-CT, so they were treated as cardiac sarcoidosis (G(-) group). 18F-FDG uptake was expressed as the maximum standardized uptake value (SUVmax). We compared reductions of SUVmax in response to therapy in both groups. Furthermore, the relationship between the 18F-FDG uptake pattern and prognosis was examined. Results: After steroid therapy, SUVmax was significantly reduced in both the G(+) group (from 8.0±0.9 to 4.0±0.4, p=0.04) and the G(-) group (from 8.3±3.4 to 6.2±3.2, p<0.01). Neither the absolute value of SUVmax nor the ΔSUVmax after steroid therapy were significantly correlated with event-free survival. After steroid therapy, ten patients showed diffuse uptake on 18F-FDG PET and five patients showed focal uptake. Major cardiac events (sudden cardiac death, ventricular arrhythmia, heart failure and complete AV block) occurred in 60% of patients with diffuse and 20% of those with focal uptake. Ten patients relapsed after reducing the dose of prednisolone. 18F-FDG uptake was significantly increased with low-dose prednisolone (mean 9.3±4.8 mg) compared with high-dose prednisolone. Conclusions: This study suggests that some cases of cardiac sarcoidosis cannot be diagnosed by current guidelines, and HL 18F-FDG PET might be useful for diagnosis of cardiac sarcoidosis and evaluation of the response to therapy.