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).