Dual-Time-Point 18F-FDG PET/CT in Infective Endocarditis: Impact of Delayed Imaging in the Definitive Diagnosis of Endocarditis

Abstract

Infective endocarditis (IE) is a major public health condition due to the associated high morbidity and mortality. Our objective was to evaluate the utility of dual-time 2-deoxy-2-[18F] fluoro-D-glucose (18F-FDG) Positron Emission Tomography/Computed Tomography (PET/CT) imaging in the diagnosis of active IE in patients with suspected native valve endocarditis (NVE) and prosthetic valve endocarditis (PVE). For this purpose, a retrospective study was carried out, including patients suspicious of NVE or PVE who underwent a dual-time-point 18F-FDG PET/CT. A final diagnosis was established by the Endocarditis Team after patient follow-up using all the available findings. Sixty-nine patients were assessed. A final diagnosis of NVE was established in 3 patients of the 34 by 18F-FDG PET/CT and in the case of PVE was established in 20 patients of the 35. A statistically significant association was found when evaluating the association between PET diagnosis at early acquisition and final diagnosis of IE (χ² = 30.198, p < 0.001) and PET diagnosis at delayed acquisition for final diagnosis of IE (χ² = 9.412, p = 0.002). Delayed PET/CT imaging determined the IE diagnosis in 16/58 of the studies. In conclusion, delayed 18F-FDG PET/CT imaging seems to be useful in improving the definitive diagnosis of IE.

Keywords: PET/CT; dual-time-point; infective endocarditis; native valve; prosthetic valve.

Figure 1

A 61-year-old male patient with a bioprosthetic aortic valve due to severe mitral insufficiency and stenosis with high fever for 17 days. Transthoracic and transesophageal echocardiography showed no paravalvular leakage or any thrombus on the valve leaflets or heart chambers. Two sets of blood cultures were negative. Patient with antibiotic treatment 12 days before PET/CT. MIP image (A), transaxial CT (B), attenuation-corrected PET (C), and non-attenuation-corrected PET images (D) showed focal and heterogenous increased 18F-FDG uptake at the site of aortic valve with 5.7 SUVmax, which increased to 6.9 on delayed images (E–H). Patient was finally diagnosed with confirmed PVE after PET/CT and completed a long-term treatment with antibiotics.

Figure 2

A 61-year-old male patient with no story of heart disease presented to the hospital with a high fever (up to 40 °C) and shivers daily for a month. In two sets of blood cultures grew Enterococus faecalis. Transthoracic echocardiography revealed 16 × 7 mm vegetation on the aortic valve. Antibiotic treatment started 7 days before PET/CT. 18F-FDG PET/CT images MIP (A) and axial views in fused (B) and PET (C) showed a faint focal uptake at the site of the aortic native valve, which increased on delayed imaging with a SUVmax of 4 (D). When we evaluated the impact of late imaging on the definitive diagnosis of IE, in the positive cases the late imaging showed an increase in intensity in both visual and quantitative assessment, except in one case, which was also assessed as visually positive. In the late acquisition, 6 new foci were observed on the late imaging and these findings were determined to be positive for active IE.