Loeffler's Endomyocarditis: Clinical characteristics and outcomes from a tertiary care centre registry

BACKGROUND: Loeffler's endomyocarditis, the cardiac manifestation of hypereosinophilic syndrome, is characterized by eosinophilic myocardial infiltration and thrombus formation leading to restrictive cardiomyopathy. METHODS: In a retrospective single-center registry, patients diagnosed with Loeffler's endomyocarditis between 2017 and 2025 were included. Clinical data, biomarkers, echocardiography, cardiac magnetic resonance imaging (CMR), and endomyocardial biopsies (n = 8) were analyzed. RESULTS: Eighteen patients were included. Hierarchical clustering identified two patterns: an acute inflammatory form with elevated troponin T, C-reactive protein, fever, and subepicardial late gadolinium enhancement (LGE), and a subacute/chronic form with lower inflammatory activity, frequent ventricular thrombi, subendocardial LGE, and increased left atrial volume index. Peripheral eosinophilia was present in 61.1% of patients at any time of assessment. The vast majority of patients received corticosteroids and heart failure therapy; 88.2% received oral anticoagulation. During follow-up, left ventricular ejection fraction remained stable, NT-proBNP levels decreased, and most ventricular thrombi resolved. Over a median follow-up of 22 months, no deaths occurred, although two patients required cardiac transplantation. CONCLUSIONS: Loeffler's endomyocarditis shows heterogeneous clinical and imaging patterns consistent with two exploratory patterns. Absence of peripheral Eosinophilia is frequent and should not exclude consideration of the diagnosis. Early recognition and immunosuppressive may be associated with favorable outcomes. Further integrative diagnostic approaches and prospective studies are needed to improve patient stratification and management.