Discussion
The incidence of infective endocarditis (IE) in the United States is steadily increasing despite updates in prophylaxis guidelines. It has increased from 11 to 15 cases per 100 000 people per year. Compared to the widespread data on left-sided IE, right-sided IE is reported less frequently. Right-sided IE accounts for only 5% to 10% of all IE cases with intravenous drug use (IVDU) as the most common risk factor (1). Tricuspid valve (TV) is involved in majority of reported right-sided endocarditis cases, which makes isolated pulmonary valve endocarditis (PVE) a rare entity accounting for 1.5% to 2% of cases (2). Isolated pulmonary valve involvement is uncommon. Importantly, native PV involvement is rarer with an estimate occurrence of 0.2% to 1.2%. The majority of native valve endocarditis affects the left-sided heart valves (3)(4). Table 1 summarizes the most common organisms in right sided-IE with Staphylococcus aureus being the predominant organism (1). For enterococcal bacteremia, gastrointestinal and urinary tracts, intravascular catheters and wounds (ulcers, burns) must be considered as possible entry points. The relative risk of E. faecalis bacteremia for endocarditis, though higher compared to other enterococcal species, is still relatively low and usually associated with prolonged bacteremia of community onset, with unclear source or with prosthetic valve.
Fever, together with predominantly pulmonary symptoms (dyspnea, pleuritic chest pain, cough, hemoptysis) remains to be the most common symptom in PVE (5). A low pitched, short diastolic murmur describes PV regurgitation, which can be easily missed (6). The absence of cardiac symptoms, common risk factors or involvement of other valves leads to a delayed diagnosis (5).
The primary imaging modality used to detect right-sided IE is echocardiography. TTE optimally provides critical information since the right-sided structures are located anteriorly and close to its transducer. However, for cardiac-device related IE, transesophageal echocardiography (TEE) is usually used as TTE has limited sensitivity for the detection of pacemaker lead vegetations (1).
Valvular insufficiency, abscess formation and septic pulmonary embolism are the most common complications of right-sided IE (Table 2) (1). Like left-sided IE, intravenous antibiotics remains the cornerstone of treatment in right-sided IE. Surgical intervention which includes vegetation removal, radical debridement of vegetations, and infected tissue and valve repair may be warranted in certain circumstances as summarized in Table 3 (1).