Multimodality Imaging in the Diagnostic Work-Up of Endocarditis and Cardiac Implantable Electronic Device (CIED) Infection

Abstract

Infective endocarditis (IE) is a serious cardiac condition, which includes a wide range of clinical presentations, with varying degrees of severity. The diagnosis is multifactorial and a proper characterization of disease requires the identification of the primary site of infection (usually the cardiac valve) and the search of secondary systemic complications. Early depiction of local complications or distant embolization has a great impact on patient management and prognosis, as it may induce to aggressive antibiotic treatment or, in more advanced cases, cardiac surgery. In this setting, the multimodality imaging has assumed a pivotal role in the clinical decision making and it requires the physician to be aware of the advantages and disadvantages of each imaging technique. Echocardiography is the first imaging test, but it has several limitations. Therefore, the integration with other imaging modalities (computed tomography, magnetic resonance imaging, nuclear imaging) becomes often necessary. Different strategies should be applied depending on whether the infection is suspected or already ascertained, whether located in native or prosthetic valves, in the left or right chambers, or if it involves an implanted cardiac device. In addition, detection of extracardiac IE-related lesions is crucial for a correct management and treatment. The aim of this review is to illustrate strengths and weaknesses of the various methods in the most common clinical scenarios.

Keywords: Infective endocarditis; computed tomography; echocardiography; endocarditis team; magnetic resonance imaging; multimodality imaging; nuclear imaging; positron emission tomography.

Figure 1

Infective endocarditis (IE) on aortic valve. Top and bottom left: Parasternal long axis and apical four-chamber transthoracic echocardiography (TTE) showing vegetation (arrows) in the left ventricle outflow tract. Top and bottom right: Transoesophageal echocardiography (TOE) showing the vegetation and the related valvular regurgitation.

Figure 2

Complications of IE. Top: Example of peri-aortic abscess (stars) with large anechoic cavity surrounding the biological prosthesis (left: TTE with parasternal short axis view, right: TTE with parasternal long axis view). Bottom: Example of peri-aortic pseudoaneurysm (star) with large cavity communicating with cardiovascular lumen (left: TOE short axis view showing large vegetation on prosthesis cusps, right: TOE log axis view with color Doppler showing flow into the perivalvular cavity).

Figure 3

Vegetation on cardiac computed tomography angiography (CCTA) images. A 69-year-old man with fever and IE. Multiplanar CCTA reconstructions on three-chamber (A) and coronal (B) views show a 2-cm, hypodense, club-shaped, soft-tissue oscillating mass (arrows) attached to the ventricular side of aortic valve leaflets, which appear floating in the lumen of the left ventricular outflow tract in reconstructed axial valve planes (C). Sensitivity of CCTA in detecting vegetation ranges from 52.8% for small lesion to 94.4% for larger ones (>10 mm) [24].

Figure 4

Paravalvular abscesses. CCTA (top images) multiplanar reconstructions and Cardiovascular Magnetic Resonance (CMR) images (bottom images: T1-weighted Turbo Spin Echo on the left, contrast-enhanced T1-weighted Gradient Echo 3D image in the middle and cine-CMR on the right) show a diffuse, partially calcified, thickening of the aortic valve leaflets in a 58-year-old man with Staphilococcus aureus IE and bicuspid valve. IE was complicated by the formation of small perivalvular abscesses, which, following the opening of their contents in the lumen, appear as little saccular outpouchings (arrows).

Figure 5

Complications of prosthetic valve endocarditis (PVE). Top: Biological prosthesis dehiscence in aortic position with large perivalvular leak (left: TOE long-axis view, right: 3D TOE view). Bottom: Biological prosthesis dehiscence in mitral position with large perivalvular leak (left: TOE long-axis view showing the direct communication between atrium and ventricle, right: 3D TOE view). Stars indicate the place of maximal prosthesis dehiscence.

Figure 6

Infective late complication in a patient with Bentall prosthesis: Dehiscence and periprosthetic pseudoaneurysm. CCTA multiplanar reconstructions show a large dehiscence of the surgical suture at the proximal anastomosis of the prosthesis with large communication (arrow) of the left ventricular cavity with a large false lumen (asterisks) recanalized from perivalvular communication (arrow); a little periannular pseudoaneurysm (arrowhead) is seen adjacent to the ventriculo-aortic junction.

Figure 7

Example of the use of multimodality imaging. A patient with history of aortic valve replacement with mechanical prosthesis and ascending aorta graft presented four years later with acute right lower limb ischemia due to occlusion of proximal fibular, anterior tibial, and posterior tibial arteries treated with revascularization attempts and finally leg amputation. During hospitalization, the patient had fever with increased erythrocyte sedimentation rate and C-reactive protein. TTE (A) and at TOE (B,C) show the presence of hyperechogenic periprosthetic area (white arrows), most likely consistent with abscess. Blood culture was negative. The fluoro-18-fluorodeoxyglucose positron emission tomography/computed tomography ((¹⁸F)FDG PET/CT) exam including CCTA (D-J) was performed showing an organized fluid perigraft collection surrounded by thick walls (asterisk) that enhance after iodinated contrast injection on CCTA images (D), which is associated to intense uptake of (¹⁸F)FDG around the aortic valve prosthesis, as shown by the yellow arrows ((E,G) show noncontrast CT transaxial images while (F,H) show the fused PET/CT images). Myocardial suppression of (¹⁸F)FDG uptake is achieved by high-fat, low-carb diet. In addition, the whole-body images showed an area of spleen uptake, consistent with septic embolism ((I,J), noncontrast CT and fused PET/CT transaxial images, respectively), as indicated by the yellow arrow. Ao: ascending aorta; LV: left ventricle.

Figure 8

Example of the use of (¹⁸F)FDG PET/CT in a patient with non-Hodgkin’s lymphoma and sudden onset of fever and a positive blood culture for Streptococcus dysgalactiae. The patient underwent TTE and TEE, which were negative. Antimicrobial treatment was started. Due to the lack of clinical response, the patient underwent (¹⁸F)FDG PET/CT, which revealed infection, as indicated by the black and yellow arrows, involving the pocket of the device ((A), from left to right, CT, PET, and superimposed PET/CT transaxial (upper panel) and coronal (lower panel and (B) non-attenuated corrected transaxial images) as well as the intracardiac portion of the lead extending to the tricuspid valve ((C), from left to right, noncontrast CT, PET, and fused PET/CT coronal images). Based to the PET/CT findings, the device was extracted and replaced.