Management of a Massive Left Ventricular Thrombus in Loeffler Endocarditis: Case Report

Abstract Background Loeffler endocarditis is a rare form of cardiomyopathy caused by eosinophilic infiltration of the endocardium with endomyocardial fibrosis and thrombus formation. It carries significant risk for systemic thromboembolism. This case describes the successful medical management of a massive left ventricular thrombus and highlights the role of cardiac magnetic resonance (CMR) in this condition. Case Summary A 54-year-old female with eosinophilic granulomatosis with polyangiitis with a heart murmur underwent an echocardiogram showing dilated cardiomyopathy with left ventricular ejection fraction (LVEF) of 39%. Follow-up CMR showed apical predominant endomyocardial fibrosis with a large apical thrombus consistent with Loeffler endocarditis. The clinical course was complicated by direct oral anticoagulant (DOAC) failure and intolerance of immunosuppression, requiring warfarin and biologic (mepolizumab) therapy. The patient has remained free of systemic thromboembolic events while on immunosuppression and systemic anticoagulation. Discussion There is limited data on the management of Loeffler endocarditis. The widespread availability of cardiac magnetic resonance (CMR) can allow for early diagnosis of cardiac involvement in eosinophilic and other inflammatory conditions. Despite common cardiac involvement in eosinophilic diseases, there are no universal screening guidelines for echocardiography or CMR. Anticoagulation in the setting of Loeffler endocarditis is based on guidelines and retrospective studies demonstrating safety of DOAC. If cardiac involvement is suspected in eosinophilic diseases, early CMR can allow for detection and prevention of complications from Loeffler endocarditis.