¹⁸F-fluorodeoxyglucose positron emission tomography and rest myocardial perfusion imaging in non-granulomatous...

Data on the use of fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) in non-granulomatous myocarditis are limited, and no study has evaluated the diagnostic performance of combined FDG-PET and rest myocardial perfusion imaging (rMPI).

We conducted a multicenter prospective observational feasibility study of patients who underwent combined FDG-PET/CT with rMPI as well as cardiac magnetic resonance (CMR) for suspected myocarditis. When available, endomyocardial biopsy (EMB) established the diagnosis according to consensus criteria. Otherwise, the final adjudicated clinical diagnosis served as the reference standard. All patients had a minimum follow-up of 12 months following PET imaging.

Twenty-five patients were included, of whom 18 (72%) were diagnosed with myocarditis. FDG-PET and rMPI demonstrated a sensitivity/specificity of 61%/100%, and 59%/71%, respectively. Inter-reader agreement for FDG-PET was excellent (κ = 0.84, 95% CI 0.62-1.00). The combination of FDG-PET and rMPI yielded a sensitivity of 82% (95% CI: 50-93%) and a specificity of 71% (95% CI: 29-96%). Late gadolinium enhancement (LGE), excluding isolated subendocardial patterns, showed a sensitivity/specificity of 72%/57%. Spatial agreement between rMPI perfusion defects and LGE on CMR was modest (κ = 0.35, 95%CI: 0.23-0.47).

Combining FDG-PET with rMPI may be a feasible imaging modality for detecting non-granulomatous myocarditis by capturing both inflammatory and fibrotic components across different disease stages.