**4.2. Right-sided endocarditis**

Right-sided endocarditis (RSE) is epidemiologically distinct from left-sided cardiac infection and is associated with a lower mortality, except when vegetations are ≥20 mm [39]. Often vegetations are larger in size nevertheless infrequently associated with periannular extension [40].

The three major subgroups of RSE include IVDAs, cardiac device-related IE (CDRIE), and CHD. A minority of cases do not fit into any category, usually occurring in patients with structurally normal valves and a history of an indwelling venous catheter for treatment of an unrelated medical condition. This group may have a higher risk of periannular complications. In addition, left-sided IE, such as periannular aortic infection, can extend to involve the rightsided cardiac valves [40].

Endocarditis in IVDAs is more frequently associated with fungal and polymicrobial infections, both of which carry a much higher mortality than the expected 5–10% in RSE [39]. Endocarditis in the IVDA group most commonly involves the tricuspid valve with *S. aureus* the usual culprit. Infection rates are higher in HIV-seropositive and HIV-immunosuppressed individuals [40].
