The Use of 18F-FDG-PET in Systemic Sclerosis with Myocardial Involvement: The Scleroderma Heart Study

Objectives: Cardiac involvement in scleroderma due to myocardial inflammation and fibrosis is associated with poor outcomes, but there is lack of consensus on its investigation and treatment. In this prospective pilot study, we aimed to assess the cardiac uptake of 18F-FDG-PET/CT in suspected scleroderma cardiomyopathy. Methods: The Scleroderma Heart study involved 16 patients with cardiac scleroderma but no coronary artery disease. 18F-FDG-PET/CTs were performed, and the patients with a positive scan were offered a second 18F-FDG-PET/CT scan after 6–9 months. The clinical characteristics and clinical outcomes (all-cause mortality) were compared between the patients with positive and negative 18F-FDG-PET/CT scans. Results: Of the 16 included patients, 8 (50%) had positive myocardial uptake on the 18F-FDG-PET/CT, 2 of whom showed a pattern consistent with cardiac involvement in scleroderma, while 6 patients more likely had physiological uptake. Over a mean follow-up of 603.3 days, all-cause mortality occurred in six patients (37.5%), and the mortality was similar between the two groups. Five patients with repeat 18F-FDG-PET/CTs showed stable or increased FDG uptake despite immunosuppression. Conclusions: To the best of our knowledge, this is the first study to investigate 18F-FDG-PET/CT in scleroderma patients with suspected cardiac involvement. The cardiac PET showed limited clinical utility due to frequent physiological uptake and lack of correlation with the treatment response. Further studies with larger cohorts and standardised interpretation criteria are needed before cardiac PET can be recommended for routine clinical use in scleroderma cardiomyopathy.