The Utility of FDG-PET/CT in the Assessment and Management of Loeffler's Endocarditis

Introduction: Review current diagnostic guidelines for Loeffler’s endocarditis. Explore the utility of FDG-PET/CT for disease assessment and management.

Methods: Endocarditis parietalis fibroplastica or Loeffler’s endocarditis (LE) is a restrictive cardiomyopathy that occurs as a cardiac manifestation of an hypereosinophilic state. LE is most commonly associated with hypereosinophilic syndrome (HES), which is characterized by an elevated eosinophil count (>1500/mm³) for 6 months, organ involvement or damage as the result of eosinophil mediation, and no other identifiable etiology of hypereosinophilia. LE involves three stages: endomyocardial necrosis, formation of thrombi, and fibrosis. Although LE is a rare form of restrictive cardiomyopathy, it represents a major source of morbidity and mortality in patients with HES, so early identification and treatment is critical. The current gold standard diagnostic procedure for LE involves biopsy of endomyocardial tissue, which is highly invasive. Non-invasive imaging modalities, like cardiac magnetic resonance (CMR) imaging and computed tomography (CT) have limitations, some of which are addressed by 18F-fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT). This exhibit will examine the clinical utility of FDG-PET/CT in LE diagnosis and demonstrate its relative utility compared to other imaging modalities.

Results: FDG-PET/CT imaging is a highly sensitive method for detecting and visualizing inflammation. FDG-PET/CT has been shown to be useful in the detection, staging, and management of other inflammatory cardiac diseases. Early visualization of inflammation is possible through FDG-PET/CT, which is paramount in LE, as treatment can be initiated prior to irreversible myocardial damage. PET imaging can also help with staging thorough myocardial perfusion imaging with radiotracers like 13-Nammonia or 82-rubidium, which can detect irreversible fibrosis and other structural changes. This can be especially useful for therapeutic management, when attempting to identify why patients have not responded to medication. CMR is currently used as first-line imaging for diagnosis of LE, but it has limitations. CMR is contraindicated in a variety of populations, such as those with claustrophobia or those with implanted non-magnetic resonance imaging conditional devices. CT is able to assess the third stage of LE and extracardiac manifestations of HES, but, due to poor visualization of inflammation, it is not ideal for detecting LE in its earlier stages. FDG-PET/CT can address this because it has been shown to be able to visualize such inflammation, which can lead to earlier therapeutic intervention. Additionally, FDG-PET/CT can be used for early diagnosis when CMR results are negative but clinical presentation suggests an ongoing disease process. FDG-PET/CT has the additional benefit over CMR for detecting extracardiac manifestations of HES. In addition to PET/CT, positron emission tomography/magnetic resonance imaging (PET/MR) has shown great potential in evaluating inflammatory conditions like LE, so this modality should also be considered when CMR is not contraindicated. Therefore, we propose that the integration of FDG-PET/CT is essential to the future of LE diagnosis and management in a multi-modal approach.

Conclusions: We argue that FDG-PET/CT may play an important role in the initial evaluation of LE as well as in subsequent evaluations in order to determine response to therapy. Future studies should focus on determining the optimal role for FDG-PET/CT in LE compared to other imaging modalities.