Tri-modality imaging in cardiac sarcoidosis: real-world concordance of cardiac magnetic resonance, echocardiography and fdg-pet

Introduction

Cardiac sarcoidosis (CS) is an uncommon yet potentially life-threatening condition, associated with ventricular arrhythmias and sudden cardiac death. Cardiac magnetic resonance (CMR) and 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) are pivotal for diagnosis and for assessing myocardial inflammatory activity.

Purpose

To describe the clinical, electrocardiogram (ECG), echocardiography, CMR and 18F-FDG PET of a portuguese cardiac sarcoidosis cohort, and to assess concordance between CMR and PET at baseline and on follow-up under immunosuppression.

Methods

Retrospective descriptive study including all patients with sarcoidosis and cardiac involvement followed at a dedicated cardiomyopathy outpatient clinic between 2021–2025. CS diagnosis followed international consensus criteria (Heart Rhythm Society Expert Consensus, 2014; Japanese Circulation Society, 2021; World Association of Sarcoidosis and Other Granulomatous Disorders, 2014). Data were collected from clinical and imaging records. Continuous variables are presented as median [IQR] and categorical variables as counts (%).

Results

A total of eight patients were included in the study, with a median age of 66.0 years (IQR 56.8–72.8); 63% of participants were male and all were Caucasian. Regarding immunosuppression, seven patients received oral corticosteroids, seven were treated with steroid-sparing agents, and three were administered biologics. Two patients exhibited isolated cardiac sarcoidosis. Baseline ECG revealed sinus rhythm in 65% of patients, atrial fibrillation in 25%, and paced rhythm in 10%, with a median QRS duration of 108.0 ms (IQR 89.4–110.9). 24-hour Holter monitoring detected nonsustained ventricular tachycardia in two patients.

CMR imaging demonstrated a left ventricular ejection fraction of 54.0% (IQR 48.0–59.0) and a right ventricular ejection fraction of 45.0% (IQR 40.3–51.0). Late gadolinium enhancement was present in all patients (Figure 1A), predominantly affecting the basal septum; the median number of involved segments was 2 (IQR 2–3).

Baseline 18F-FDG PET imaging (n=6) revealed positive results in three patients, negative results in two, and inconclusive findings in one (Figure 1B). When comparing CMR and PET results at baseline, both modalities were concordant in three patients (positive findings in both PET and CMR), while two patients displayed negative PET results despite notable findings on CMR. Following a median follow-up period of 3.0 years (IQR 2.3–3.4) under immunosuppression, follow-up PET scans (n=4) were negative in all patients; however, significant features remained evident on CMR.

Conclusion

CMR and PET identified cardiac involvement, highlighting their relevance beyond echocardiography alone. During immunosuppression, PET findings evolved from PET+/CMR+ at baseline to PET−/CMR+ at follow-up, supporting a decline in inflammatory activity over time despite persistence of a fibrotic structural substrate.For image description, please refer to the figure legend and surrounding text.