Loeffler Endocarditis Causing Heart Failure with Preserved Ejection Fraction (HFpEF): Characteristic Images and Diagnostic Pathway.

We report the case of a 69-year-old female patient in which echocardiography and cardiac magnetic resonance imaging were used to diagnose a patient presenting with heart failure with preserved ejection fraction (HFpEF) due to Loeffler endocarditis. Loeffler endocarditis is an uncommon cause of heart failure with preserved ejection fraction, triggered by eosinophil and lymphocyte infiltration of the endomyocardium, followed by the formation of thrombus in the afflicted area, and eventually fibrosis. This condition is due to an increased number of eosinophils associated with allergies, infections, systemic conditions, as well as malignancies and hypereosinophilic syndrome. Loeffler endocarditis can lead to serious complications, such as progressive heart failure, systemic thromboembolic events, or arrhythmias (including sudden cardiac death).