Utility of ¹⁸F-FDG PET/CT and Cardiac MRI in early Cardiac Sarcoidosis

Although ¹⁸F-FDG-PET/CT and CMR are commonly used to diagnose cardiac sarcoidosis(CS), their clinical utility in early-vs. late-stage disease is unclear. The objective of this study was to compare the diagnostic utility of 18-fluorodeoxyglucose positron emission tomography/computed tomography(¹⁸F-FDG-PET/CT) and cardiac magnetic resonance imaging(CMR) in patients with early- and late-stage CS.

Data of 110 consecutive patients with biopsy-proven CS from the Granulomatous Myocarditis Registry were analyzed. All patients underwent ¹⁸F-FDG0PET/CT and CMR within 2 weeks of initial clinical presentation. Patients were divided into early-(<6 months) and late-stage groups based on the time since their first cardiac presentation. Myocardial uptake and late gadolinium enhancement(LGE) were qualitatively and quantitatively assessed. Complete clinical, echocardiographic, and radiological responses were assessed after 4-6 months of immunosuppressive therapy(IST).

Among the 102 patients in the final analysis(44.1 ± 10.3 years; LV ejection fraction[LVEF], 43.1 ± 9.5 %),54.9 % and 45.6 % received early and late diagnosis, respectively. Abnormal myocardial uptake on ¹⁸F-FDG-PET/CT 100 %) was observed in all patients with early CS, while only 73.2 % showed LGE on CMR(p < 0.001). The diagnostic yield of ⁸F-FDG-PET/CT and CMR was similar in late CS(91.3 %vs.97.8 %,p = 0.498). Patients with early CS had a higher myocardial SUV_max and more extensive LV involvement than those with late CS. Complete response to IST was more common in patients with early CS than in those with late CS(62.5 %vs.47.8 %,p = 0.019). In the early CS cohort, patients without LGE had a higher rate of complete response following IST than those with LGE (86.7 %vs.53.7 %,p = 0.025).

In patients with early CS,¹⁸F-FDG-PET/CT appears to be more sensitive and useful than CMR for diagnosis and assessment of response to IST.