Infection in the “fifth valve” of the heart

Introduction: Infections of the right side of the heart are frequently seen in patients with intravenous drug use, or in those with invasive devices such as pacemakers or catheters. The majority of cases involve tricuspid or pulmonary valves, but may implicate the Eustachian valve (EV). Known as “the valve of the vena cava”, the EV helps the fetal circulation direct oxygen rich blood from the right atrium through the foramen ovale into the left atrium. Typically it regresses to become vestigial or absent, as it serves no functional purpose in adults. If present, they are often only discovered incidentally, or when there are stigma of infection. This was the scenario in our patient, who developed endocarditis of the EV. CASE PRESENTATION: A 56 year old female with a history of polysubstance abuse presented with cough, back pain and fever. Her workup found gram-positive bacteremia, but a trans-thoracic echocardiogram (TTE) found normal appearances of the tricuspid and pulmonic valves. There was, however, a suspicious echogenic focus noted at the inferior vena cava-right atrium junction, which could not be more specifically described [Image 1]. She was sent for trans-esophageal echocardiogram (TEE) that found a persistent EV, directed toward the inter-atrial septum. A 9mm mobile filamentous structure was attached to this EV [Image 2]. Her blood cultures soon grew methicillin-resistant Staphylococcus aureus. She now met 2 major Duke criteria for infective endocarditis, was treated with 6 weeks of intravenous vancomycin, and discharged in good condition. Another TEE 5 months later found no remaining echocardiographic evidence of vegetations. DISCUSSION: EV endocarditis usually occurs without associated involvement of any other cardiac valves. Localization of infections to the EV is hypothesized to be a result of structural abnormalities or abnormal turbulent blood flow near the valve, or from unknown bacterial virulence factors. While Staph aureus is the most common culprit organism, E. coli, Proteus vulgaris, Enterobacter and Strep viridans have also been described. TEE appears to be a more sensitive diagnostic tool, and is recommended when there are normal results on TTE. Following treatment, vegetations may disappear or persist. Conclusions: Eustachian valves are rare findings in adults, but should be strongly considered in all cases of endocarditis, particularly if no classic vegetations are identified on TTE. A routine examination of the EV should be included in any echocardiographic interrogation of patients suspected to have endocarditis