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

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 REPORT 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.