ABSTRACT
BACKGROUND: Myocardial inflammation and perfusion defects detected by 18F-fludeoxyglucose (FDG) and Rubidium-82 positron emission tomography (PET) may be associated with ventricular arrhythmias (VAs) in cardiac sarcoidosis (CS). The role of serial quantitative PET in determining the effect of treatment on myocardial inflammation and clinical outcomes is yet to be defined. METHODS: Newly diagnosed CS patients with active myocardial inflammation (maximum standardised uptake value (SUVmax) ≥ 2.5) were treated with immunosuppression, then underwent repeat FDG-PET, Rubidium-82, and echocardiographic imaging 6-12 months later. Serial changes in SUVmax, SUVmean, inflammatory extent, perfusion defect (PD) extent, metabolism/perfusion mismatch extent, global cardiac metabolic activity, and left ventricular ejection fraction (LVEF) were assessed. The primary endpoint was a composite of all-cause mortality, serious VA and heart-failure (HF) hospitalisation. Event data were recorded from the date of the second FDG-PET. RESULTS: The study population consisted of 113 patients (66% male, age: 55 ± 11 years, LVEF: 54 ± 13%). SUVmax reduced from 4.5 (interquartile range: 3.3-7.1) to 2.7 (2.2-3.6). Overall, 94 (83%) patients saw serial reduction in SUVmax, with 42 (37%) demonstrating complete response (SUVmax <2.5). Following a median of 46 (25-57) months, 28 (25%) patients reached the endpoint (8 deaths, 17 VAs, and 3 HF hospitalisations). PD extent (Hazard ratio 1.03, 95% confidence interval: 1.01-1.05; p = 0.035) was a significant predictor of outcome following treatment, even after accounting for LVEF and change in SUVmean. The risk of adverse events was the greatest in those with a pre-treatment or post-treatment PD extent of >10%. CONCLUSION: In our cohort with active CS, following a treatment-induced reduction in myocardial inflammation, PD extent was the main predictor of adverse events.
