The diagnosis of IE can be reached using validated criteria which are mainly based on blood culture results and echocardiographic findings, and several minor criteria [1,2,3]. Recently, 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) showed also a role in diagnosing prosthetic-valve endocarditis [4].

Vegetations (i. e., oscillating masses on the low-pressure side of valvular leaflets), perivalvular abscess (i.e., anechoic area in the perivalvular tissue, which if filled on color Doppler is indication of a pseudoaneurysm) and a new dehiscence of a prosthetic valve (typically detected as a pathologic perivalvular leak) are the tree main echocardiographic findings of IE [1]. Minor echocardiographic findings include valve fenestrations, nodular valve thickening and non-oscillating targets [3] (Table 1).

In general, sensitivity of TTE is lower for native-valve endocarditis compared to transesophageal echocardiogram (TEE). TTE has a sensitivity of about 75% for detection of vegetations in native-valve IE, which rises to around 90% for TEE [1]. Specificity is high for both methods (about 90%) [1]. For perivalvular abscess, the sensitivity of TTE is about 50%, reaching about 90% for TEE. Specificity is also similar for both methods (about 90%). For prosthetic-valve endocarditis and device-related IE, TEE has a better sensitivity compared to TTE. Despite the high sensitivity and specificity of TEE, around 15% of patients show false-negative echocardiograms. Therefore, TEE should be repeated in 7–10 days if the suspicion of IE remains high. As the first method to use, TTE is non-invasive, aids in detecting vegetations and also provides crucial information about the systolic and diastolic function of both ventricles as well as the repercussion of valvular regurgitation on the cardiac function (i.e., low cardiac output, high left ventricular filling pressure/pulmonary edema). Limitations of TTE are a poor acoustic window, detecting small-sized vegetations and prosthetic valve/device-related endocarditis. While the initial exam to be performed is TTE in all patients with suspicion of IE, TEE should be always subsequently performed in most cases (Fig. 2). For right-sided endocarditis, TTE is not inferior to TEE [1].

Diagnostic algorithm for echocardiographic diagnosis of infective endocarditis. TTE transthoracic echocardiogram, TEE transesophagic echocardiogram. Modified from [1]

Knowing the size of the vegetations aids in estimating the risk of embolism (> 10 mm high risk; > 15 mm very high risk) [1]. In general, vegetations in the mitral valve have a high risk of embolism, as observed in our patient, while IE of the aortic valve produce more often destructive lesions (abscess formation) [1]. The most important differential diagnosis of vegetations include tumors, thrombus, catheters/leads, papillary muscle or chordae tendineae rupture, prominent Eustachian valve and Chiari network, and also non-infective vegetations (marantic endocarditis) [1].

Surgery is typically indicated in native-valve endocarditis causing refractory pulmonary edema or shock, perivalvular abscess, large aortic or mitral vegetations (> 10 mm) following one or more embolic events, in prosthetic-valve endocarditis and in cardiac device-related IE.