Reversible Severe Heart Failure in Corticosteroid-Refractory Cardiac Sarcoidosis: The Crucial Role of 18F-FDG PET/CT in MRI-Negative Disease

Abstract

Background: Cardiac involvement significantly impacts the prognosis of sarcoidosis. While conduction abnormalities represent the classic presentation, inaugural acute heart failure with severe left ventricular dysfunction is a less common and diagnostically challenging phenotype that can closely mimic idiopathic dilated cardiomyopathy. Furthermore, diagnosing cardiac sarcoidosis (CS) can be complex when initial advanced imaging yields false-negative results. Case Presentation: A 43-year-old female with a history of cutaneous sarcoidosis, maintained on chronic oral corticosteroids, presented with rapidly progressive heart failure (New York Heart Association class III). Transthoracic echocardiography revealed severe left ventricular systolic dysfunction with an ejection fraction of 26%. Her clinical course was notably complicated by an episode of paroxysmal atrial fibrillation and a subsequent transient ischemic attack (TIA). Cardiac magnetic resonance (CMR) imaging was non-contributory, showing no evidence of edema or late gadolinium enhancement. However, due to high clinical suspicion, an 18F-FDG PET/CT was performed, revealing intense, multifocal myocardial uptake indicative of active granulomatous inflammation. Recognising the corticosteroid-refractory nature of her flare-up, she was treated with intravenous corticosteroid pulses, followed by the early introduction of methotrexate as a steroid-sparing agent, optimised guideline-directed medical therapy (GDMT) for heart failure, and therapeutic anticoagulation with apixaban. At one year, the patient was completely asymptomatic with a full normalisation of her ejection fraction to 52%. Conclusion: This case highlights that a normal CMR does not exclude active cardiac sarcoidosis, especially in the early inflammatory stages, reinforcing the critical diagnostic value of 18F-FDG PET/CT. Additionally, it demonstrates that severe, corticosteroid-refractory ventricular dysfunction can achieve complete functional reversibility through the early and synergistic use of methotrexate and GDMT.