FDG-PET imaging-guided immunosuppressive therapy in cardiac sarcoidosis: prognostic value of myocardial glucose uptake for predicting cardiac events and arrhythmia outcomes

Background Cardiac sarcoidosis (CS) causes 5% of sudden cardiac death in young patients but remains underdiagnosed. 18F-FDG-PET imaging identifies inflammatory burden; however, utility in guiding immunosuppressive therapy intensity and predicting long-term outcomes remains incompletely characterized. Recent evidence suggests FDG-PET-derived SUVmax at 12 months predicts mortality and arrhythmia risk superior to traditional markers. Objective To systematically evaluate FDG-PET quantitative parameters (SUVmax, TBR) for predicting major adverse cardiac events and fatal ventricular arrhythmias in CS patients undergoing immunosuppressive therapy via meta-analysis of prospective imaging studies. Methods MEDLINE, Embase, Cochrane CENTRAL (2015–January 2026) searched for prospective cohort studies in CS patients with serial FDG-PET imaging (baseline, 6-month, 12-month post-therapy). Inclusion: N≥20, documented immunosuppressive therapy (prednisolone-based ± steroid-sparing agents), reported quantitative FDG uptake (SUVmax, TBR), outcomes (MACE, ventricular tachycardia, sudden cardiac death). Primary outcomes: association of FDG-PET parameters with mortality and ventricular arrhythmia risk. Random-effects meta-analysis; I² heterogeneity assessment; subgroup analyses by therapy intensity (PSL dose), baseline LVEF, presence of late gadolinium enhancement on MRI. Results Eighteen studies (n=487 CS patients; 189 MACE events; median 3.8-year follow-up) included. Pooled analysis: 12-month SUVmax >4.5 independently predicted MACE (HR 3.2, 95% CI 2.1–4.9, p<0.001) and ventricular tachycardia (HR 2.8, 95% CI 1.6–4.8, p<0.001). Six-month SUVmax >3.5 also showed prognostic value (HR 2.1, 95% CI 1.4–3.2). Patients with complete metabolic response (SUVmax normalization at 12 months) demonstrated 5-year arrhythmia-free survival 94% versus 48% in persistent FDG uptake (p<0.001). LVEF <40% at baseline conferred additional mortality risk (HR 1.9). Prednisolone dose ≥10 mg daily associated with treatment failure and persistent FDG uptake. Conclusions FDG-PET SUVmax at 12 months is a critical prognostic biomarker in CS with superior predictive value for arrhythmia and mortality risk. Persistent FDG uptake predicts poor prognosis and may guide escalation to steroid-sparing immunosuppression. Integration of serial FDG-PET into CS management protocols is supported.