A Case Series of Eustachian Valve Endocarditis: An Under-Diagnosed and Rare Entity

Objective: Rare disease Background: The eustachian valve is rarely involved in bacterial endocarditis. Patients who present with bacteremia and evidence of organic septic emboli should raise the suspicion of endocarditis as a possible differential diagnosis. This case series describes 2 unique cases of eustachian valve endocarditis (EVE) in patients who had a history of intravenous drug use; although 63% of EVE is caused by Staphylococcus aureus, the causative agent in our first case was methicillin-resistant Staphylococcus epidermidis (MRSE), which is only the third reported case of EVE caused by Staphylococcus epidermidis. Of note, the previous 2 cases of MRSE EVE were also found to be associated with cardiovascular hardware. Case Reports: The first case of the series describes EVE by MRSE with an endovascular graft acting as the nidus of infection. Second case of EVE was caused by methicillin-sensitive Staphylococcus epidermidis (MSSA), the source of bacteremia being a rectovesicular abscess. Although initial transthoracic echoes were negative in both cases, subsequent transesophageal echoes were able to detect vegetations on the eustachian valves. Treatment included 4-6 weeks of culture-directed antibiotic therapy for both of our cases. Conclusions: EVE may be an under-diagnosed sequelae of staphylococcal bacteremia, especially in the intravenous drug abuse population, further reinforcing the importance of systemically visualizing all cardiac valves, including the eustachian valves, while performing echocardiography.