**2.1. Major Duke echocardiographic findings**

The three major echocardiographic findings as defined by the modified Duke criteria [2] suggesting direct evidence of endocardial involvement are vegetation, abscess, and new partial dehiscence of a prosthetic valve.

Vegetation is seen as a high frequency independently oscillating mass typically located on the low-pressure side of cardiac valves, in particular the atrial aspect of the atrioventricular (mitral and tricuspid) valves and the outflow tract side of the semilunar (aortic and pulmonary) valves (**Figure 1**). Less often, vegetations can be sessile with little or no mobility or have mixed sessile and mobile components.

Vegetations are commonly attached along the leaflet coaptation zone, although it can be located anywhere on the valve leaflet, annulus, and subvalvular apparatus. They are also frequently found in the path of abnormal turbulent blood flow ('jet lesion') arising from valvular regurgitation, a shunt or may spread to adjacent structures by direct contact ('kissing lesion'). Vegetations may also be attached to the endocardial surface lining the heart chambers (mural) or blood vessels (intraluminal). With an aging population and increased cardiac interventions, vegetations involving prosthetic valves, pacing leads, and other nonbiological intracardiac materials are becoming more prevalent (**Figure 2**).

that uses the properties of reflected ultrasound waves to construct high-quality two-dimensional (2D) and three-dimensional (3D) images of the heart without radiation exposure. Echocardiography should be utilized at the first opportunity when IE is suspected, to provide an early diagnosis and facilitate important management decisions. However, echocardiographic findings should always be interpreted in their clinical context to maximize diagnostic

This chapter will outline the role echocardiography in the management of IE. In addition, the history of cardiac ultrasound, its diagnostic accuracy, limitations, and emerging technologies such as 3D imaging will be reviewed. Finally, there is a section on imaging protocols and quality control to provide guidance to echocardiography laboratories wishing to pursue excellence in

The modified Duke criteria [2] is used to categorize endocarditis as definite, possible or rejected based on clinical, microbiological, echocardiographic, and pathological findings. Blood cultures and echocardiography are the two key criteria for IE. The modified Duke criteria [2] has an overall sensitivity of ∼80–90%, and specificity >90% for diagnosis of IE when compared to pathological diagnosis; however, it is less reliable for identification of prosthetic valve endocarditis (PVE) with sensitivity ∼70–80% [3–7]. Transesophageal echocardiography has been shown to improve the diagnostic accuracy of the Duke criteria for definite IE when

A high-clinical suspicion for IE should be adopted especially when fever is present in patients with a prosthetic valve or device, new murmur or heart block, underlying valvular disease or congenital heart disease (CHD), embolism, immunosuppression, previous IE, or intravenous drug abuse (IVDA). It is imperative for early blood cultures be collected prior to antibiotic

The three major echocardiographic findings as defined by the modified Duke criteria [2] suggesting direct evidence of endocardial involvement are vegetation, abscess, and new partial

Vegetation is seen as a high frequency independently oscillating mass typically located on the low-pressure side of cardiac valves, in particular the atrial aspect of the atrioventricular (mitral and tricuspid) valves and the outflow tract side of the semilunar (aortic and pulmonary) valves (**Figure 1**). Less often, vegetations can be sessile with little or no mobility or have mixed

Vegetations are commonly attached along the leaflet coaptation zone, although it can be located anywhere on the valve leaflet, annulus, and subvalvular apparatus. They are also frequently found in the path of abnormal turbulent blood flow ('jet lesion') arising from

utility.

60 Contemporary Challenges in Endocarditis

the field.

**2. Diagnosis**

compared with TTE imaging [8].

dehiscence of a prosthetic valve.

sessile and mobile components.

therapy and urgent echocardiography performed.

**2.1. Major Duke echocardiographic findings**

**Figure 1.** 3D TEE en-face view of mitral valve demonstrating multiple vegetations (arrows).

**Figure 2.** TEE mitral valve with large vegetation causing a 'stuck' anterior mechanical occluder (arrow).

A vegetation has a similar 'gray scale' ultrasound reflectance (echogenicity) to normal myocardium. Chronic 'healed' vegetations, however, often become partly calcified and therefore appear more echogenic when compared to surrounding structures. Vegetations usually have a soft 'shaggy' irregular inhomogeneous appearance on echocardiography helping to differentiate them from simple degenerative valvular tissue strands such as Lambl's excrescences, which tend to be very thin linear structures (**Figure 3**). Vegetations may reduce in size with treatment, embolize, or remain unchanged.

**Figure 3.** TEE demonstrating the common finding of a degenerative 'Lambl's excrescence' attached to the LVOT aspect (arrow) of the aortic valve.

Differential diagnoses for such masses include fibrin and thrombus, which are frequently extremely difficult, if not impossible to distinguish from vegetations on ultrasound imaging. Other findings, such as pannus and tumors, often have a characteristically distinct appearance from vegetations, albeit subtle, and therefore, it is not always possible to differentiate from one another. While imaging cannot specifically identify the type of microorganism, the appearance/ complications of a vegetation may suggest infective agents, for example, fungal vegetations tend to grow to a very large size, and staphylococcus is associated with abscess.

A minority of vegetations are noninfective in origin and referred to as nonbacterial thrombotic endocarditis (NBTE). According to one study [9], lesions resembling NBTE vegetations were identified by echocardiography frequently in patients with antiphospholipid syndrome/ Libman–Sacks (63%), myeloproliferative disorders (63%), and solid-organ malignancies (19%). The lesions most often resembled typical vegetations, but also diffuse valve involvement (e.g., **Figure 4**), with a verrucous appearance can occur [9–11].

**Figure 4.** Diffuse, 'verrucous' (arrows) thickening of mitral leaflets in Libman–Sacks endocarditis. Three-dimensional TEE mitral valve (LVOT aspect) and 2D TEE mid esophageal view, mitral valve.

Intracardiac abscesses appear as inhomogeneous echolucent or occasionally echodense regions, involving the periannular tissue or myocardium, comprised of necrotic and purulent material. A developing abscess may present as a region of periannular thickening (≥10 mm) and is referred to as a *phlegmon*. Importantly, there is no color flow on Doppler imaging into an abscess from the vessel lumen or cardiac chamber.

Abscesses are detected in patients undergoing surgery for endocarditis at the aortic annulus in 33–50% of cases, but only 10–20% are located at the mitral annulus [12–14]. Abscesses account for a higher proportion of complications in PVE (**Figure 5**) and often require surgical intervention [12, 15]. Intervalvular extension of the abscess posteriorly to involve the mitral– aortic intervalvular fibrosa (MAIVF) occurs in approximately two-thirds of aortic periannular infections [16]. In the early stages following aortic valve or root surgery, it may be difficult to distinguish normal postoperative periaortic edema and hematoma from an abscess.

**Figure 5.** TEE demonstrating posterior periprosthetic aortic abscess (arrow).

**Figure 3.** TEE demonstrating the common finding of a degenerative 'Lambl's excrescence' attached to the LVOT aspect

Differential diagnoses for such masses include fibrin and thrombus, which are frequently extremely difficult, if not impossible to distinguish from vegetations on ultrasound imaging. Other findings, such as pannus and tumors, often have a characteristically distinct appearance from vegetations, albeit subtle, and therefore, it is not always possible to differentiate from one another. While imaging cannot specifically identify the type of microorganism, the appearance/ complications of a vegetation may suggest infective agents, for example, fungal vegetations

A minority of vegetations are noninfective in origin and referred to as nonbacterial thrombotic endocarditis (NBTE). According to one study [9], lesions resembling NBTE vegetations were identified by echocardiography frequently in patients with antiphospholipid syndrome/ Libman–Sacks (63%), myeloproliferative disorders (63%), and solid-organ malignancies (19%). The lesions most often resembled typical vegetations, but also diffuse valve involvement (e.g.,

**Figure 4.** Diffuse, 'verrucous' (arrows) thickening of mitral leaflets in Libman–Sacks endocarditis. Three-dimensional

tend to grow to a very large size, and staphylococcus is associated with abscess.

**Figure 4**), with a verrucous appearance can occur [9–11].

TEE mitral valve (LVOT aspect) and 2D TEE mid esophageal view, mitral valve.

(arrow) of the aortic valve.

62 Contemporary Challenges in Endocarditis

**Figure 6.** 3D TEE en face of a prosthetic mitral valve with dehiscence at the lateral annulus (arrow).

Mitral annular abscess is often located at the mural annulus, particularly the posterior or lateral annular margin [17], rather than the septal annulus [14]. Mitral annular abscess is more frequently associated with pseudoaneurysm formation and/or fistula than aortic abscess. Complications include rupture into the coronary sinus, left circumflex artery, or the pericardial space [14]. The presence of mitral annular calcification (MAC), especially caseous calcification, can make diagnosis of annular abscess more challenging due to acoustic shadowing artifact.

New dehiscence of a prosthetic valve occurs when there is disruption of the annular sewing ring due to a breakdown of supporting tissue adjacent to the prosthesis (**Figure 6**). This results in perivalvular regurgitation and may be associated with an abnormal rocking motion. If the area of dehiscence around a bioprosthetic aortic valve is <30%, concordant motion of the valve with the aortic root will occur; however, if >40% of annular area is dehisced, discordant or rocking valvular motion will be present (**Figure 7**) [18].

**Figure 7.** TEE color flow imaging from the 'long-axis' window demonstrating severe periprosthetic aortic valve regurgitation complicating annular dehiscence (arrow). A large region of dehiscence results in a 'rocking' motion of the prosthetic valve.
