A case report of Löffler's endocarditis with right ventricular outflow obstruction in idiopathic hypereosinophilic syndrome: timely surgical intervention is crucial.

Background: Löffler's endocarditis (LE) is a frequently encountered condition in hypereosinophilic syndrome and is associated with a significant morbidity and mortality rate. Case Summary: A 22-year-old man presented with acute dyspnoea, recurring wheezing, and cough, leading to his hospital admission. Multimodal diagnostic imaging revealed a manifestation of eosinophil-mediated cardiac injury in the thrombus formation stage. Moreover, a mural thrombus and thickened endocardium had caused severe obstruction of the right ventricular outflow tract (RVOT) and complete obliteration of the right ventricular apex, resulting in a significant reduction in right ventricular cardiac output. The patient received a diagnosis of LE and was treated with high-dose corticosteroids and anticoagulants. To alleviate the RVOT obstruction, an emergency surgical intervention was conducted through median sternotomy to the removal of the mural thrombus and resection of the thickened endocardium. Subsequently, eosinophil counts normalized within 1 month. Follow-up imaging examination demonstrated the existence of a residual section of thickened endocardium within the right ventricular free wall. Importantly, no mural thrombus was detected with complete relief of the RVOT obstruction. Notably, a transthoracic echocardiography examination at the 3-month postoperative unveiled a significant regression in right ventricular endomyocardial fibrosis. The patient's condition exhibited tangible improvement, with no adverse events observed. Discussion: Multimodal imaging is essential for the early diagnosis and accurate staging of LE. Timely surgical intervention, combined with corticosteroid therapy, is an effective therapeutic approach in selected patients with LE. This approach is crucial to achieve remission of acute phase symptoms and improve prognosis.