Applications of multi-modality imaging in the diagnosis of infective endocarditis: a real-life case based contemporary narrative review

Abstract

Background and objective: Recent major international society guidelines have highlighted the utility of multi-modality imaging in the evaluation of infective endocarditis (IE). This article aims to discuss the contemporary applications of multimodality imaging in IE through real-life cases, demonstrating how emerging imaging modalities, including cardiac computed tomography (CCT) and nuclear imaging techniques can be used.

Methods: A literature search of the PubMed database was performed between Jan 01, 2024 and Oct 01, 2024. Relevant articles on the subjects of "infective endocarditis" and "multi-modality imaging" were used in our review. Four clinical cases from the Cleveland Clinic Foundation were incorporated to supplement this literature review with real-world examples.

Key content and findings: This literature review encompasses international cardiology guidelines, as well as investigational studies, meta-analyses, and dedicated reviews highlighting the specific roles, strengths, and weaknesses of different imaging modalities in the evaluation of IE, including transthoracic and transesophageal echocardiography (TEE), CCT, ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG PET), and white blood cell single-photon emission computed tomography (WBC SPECT). This review demonstrates the emerging role for these multi-modality imaging tools in light of an increasingly complex patient population with growing numbers of prosthetic valves and devices.

Conclusions: The current literature and guidelines are discussed with reference to complex clinical cases, with the aim of illustrating the relative advantages and disadvantages, and appropriate utility of multimodality cardiac imaging in IE.

Keywords: Infective endocarditis (IE); cardiac computed tomography (CCT); echocardiography; multimodality imaging; nuclear imaging.

Figure 1

Parasternal long-axis (A) and apical 4-chamber (B) views on transthoracic echocardiogram, performed on initial presentation. There was no clear evidence of vegetation or thrombus along the mitral valve ring.

Figure 2

TEE performed in outpatient clinic. (A) Mid-esophageal 2-chamber and (B) mid-esophageal long-axis views on transesophageal echocardiogram showing distinct mobile vegetations on the anterior and posterior aspects of the mitral valve ring (arrows). TEE, transesophageal echocardiography.

Figure 3

Transthoracic echocardiogram performed on patient presentation. (A) Parasternal long axis view on transthoracic echocardiogram highlighting the TAVR valve. No vegetation is appreciated but the aortic root appears mildly thickened (*). No significant aortic regurgitation is appreciated by color Doppler. (B) 4-chamber view with (C) zoomed-in image highlighting the bioprosthetic mitral valve with no clear prosthetic vegetations (arrows show prosthetic leaflets without clear vegetations). TAVR, transcatheter aortic valve replacement.

Figure 4

Transesophageal echocardiogram highlighting new pathologic findings not appreciated by transthoracic echocardiogram. (A) Mid-esophageal 4-chamber view showing thickening of the posterior aspect of the aortic sinus with a pulsatile cavity that communicates with the LV, consistent with aortic root abscess (arrow). The thickening extends to involve the intervalvular fibrosa and anterior MV annulus. (B) Zoomed-in image of mid-esophageal long axis view highlighting abscess cavity in the posterior aortic root and prosthetic aortic valve leaflet thickening (arrows). (C,D) Mid-esophageal long axis views redemonstrating the aortic root abscess (*, with blue arrows pointing towards aortic root thickening posteriorly) extending into the aorto-mitral curtain with clear communication with the LV by color Doppler (red circle). (E) Mid-esophageal commissural view highlighting small filamentous echodensity/vegetation on the atrial aspect of the prosthetic mitral valve (green arrow). LV, left ventricle; MV, mitral valve.

Figure 5

Electrocardiogram-gated cardiac computed tomography. (A,B) Axial views highlighting valve-in-valve TAVR with prosthetic aortic valve leaflet thickening (green arrow) and several small focal regions of communicating abscesses in the aortic root (blue arrows). (C) Sagittal view showing moderate thickening and calcification involving the aortic root and ascending aorta along with a small focal dissection at the proximal ascending thoracic aorta (green arrow). TAVR, transcatheter aortic valve replacement.

Figure 6

Coronary angiogram of the left native system highlighting acute vegetation embolization to the mid left circumflex artery (arrow). The proximal LAD is known to be severely ectatic and the mid to distal LAD is supplied by a patent left internal mammary artery graft (not imaged here). LAO, left anterior oblique; CAUD, caudal; LAD, left anterior descending.

Figure 7

Transthoracic echocardiogram performed on patient presentation. (A) Parasternal long-axis view showing thickening of the prosthetic AV leaflets with vegetation (blue arrow) and a pulsatile aortic root abscess and/or pseudoaneurysm (*), with color Doppler highlighting the severe aortic regurgitation and flow communication between the left ventricular outflow tract and abscess space (green arrow). (B) Parasternal short-axis view demonstrating the complex aortic root abscess with multiple septations (*). AV, aortic valve.

Figure 8

ECG-gated cardiac computed tomography showing the bioprosthetic aortic valve with thickened leaflets, surrounded circumferentially by multiple, complex contrast-filled collections with septations (*), consistent with aortic root abscess, measuring 6.2 cm × 5.5 cm around the valve. ECG, electrocardiogram.

Figure 9

Mid-esophageal short-axis view of the prosthetic aortic valve during intra-operative transesophageal echocardiogram, showing multiple collections around the aortic root (*) (A) with communication between the left ventricle outflow tract and abscess cavity seen by Doppler (arrow) (B).

Figure 10

Tagged WBC scan and whole body ¹⁸F-FDG PET/CT. (A) Tagged WBC scan demonstrates mild uptake at the level of the ascending aorta graft (blue arrow) with no abdominal graft uptake. Concomitant computed tomography was not performed at the time. (B,C) Show ¹⁸F-FDG PET/CT study and highlight increased FDG uptake in the aortic root and ascending aorta graft, concerning for infection/inflammation (blue arrows), with only low-level FDG uptake in the abdominal graft more consistent with anticipated post-surgical findings (yellow arrow). 18F-FDG PET, 18F-fluorodeoxyglucose positron emission tomography; CT, computed tomography; WBC, white blood cell.

Figure 11

Mid-esophageal view on transesophageal echocardiogram showing the ascending aorta graft surrounded by echo-dense material (*) suspicious for infection.

Figure 12

Serial CT studies. (A) Non-gated non-contrast chest CT obtained two years prior to presentation demonstrating normal post-surgical findings. (B) Gated chest CT suggestive of mild soft tissue stranding adjacent to the aortic root and ascending aorta graft (blue arrows), with minimal improvement one month later (C). CT, computed tomography.