**4.1. Prosthetic valve endocarditis**

Prosthetic valve endocarditis incidence is estimated at 0.3–1.2% per patient-year and accounts for approximately 10–30% of all cases of IE [6, 29]. Infection is classified as early or late PVE (>12 months postsurgery) and is associated with a different microbiological profile [30]. The infection rates are similar for mechanical and bioprosthetic valves, although lower for mitral valve repair [6, 31, 32]. A large multicenter registry study found that the incidence of endocarditis in transcatheter aortic valve implantation (TAVI) was 0.5% by 12 months, with almost half of the patients not surviving to discharge [33].

Mechanical prostheses are prone to periannular complications due to infection of the sewing ring predisposing to abscess, fistula, and/or dehiscence and are more likely to occur within the first few months postsurgery. Bioprosthetic valves primarily seed vegetations on the leaflets which may progress to ulceration, perforation, and/or leaflet destruction [34].

Echocardiographic imaging is more challenging in PVE, particularly with mechanical valves, due to reverberation and acoustic shadowing. Periannular involvement is common and may be obscured by artifact from the valve prosthesis [34]. Mechanical prosthetic valves are susceptible to formation of adherent thrombus and pannus, while bioprosthetic valves degenerate over time and can develop tissue strands or leaflet tears which can mimic vegetations [35].

Transesophageal echo is superior for assessment and detection of mitral and aortic prosthetic valve abnormalities, including endocarditis, thrombus, and degenerative changes, particularly for mechanical prosthetic valves [36]. Imaging with TTE is limited by the availability of an acoustic window, intervening anatomical structures between the probe and the heart, lower transducer frequency, and acoustic shadowing [36]. Multiplane TEE is highly effective for detecting mechanical valve periprosthetic mitral regurgitation (**Figure 9**), unlike TTE in which acoustic artifact obscures the left atrial aspect of the image [37].

**Figure 9.** TEE color compare showing prosthetic annular dehiscence (arrow) associated with significant mitral regurgitation.

Although color and spectral Doppler assessment of prosthetic valves should be performed during TTE and TEE examinations, transthoracic echo is preferred for assessment of hemodynamics. In the case of a mechanical prosthetic aortic valve, TTE is also superior when assessing the anterior aortic root for abscess as acoustic shadowing is posteriorly directed obscuring the TEE image.

Aortic and mitral mechanical valve occluder motion is difficult to assess with TTE. The use of 2D and 3D TEE offers excellent assessment of mitral occluder motion; however, it is often suboptimal at visualizing the aortic occluders. The addition of cine fluoroscopy can definitively assess occluder-opening angles, while multidetector-row computed tomography (MDCT) is useful for evaluating occluder motion and identifying any mass lesions [38].
