A 73-year-old male was referred for evaluation of prosthetic valve endocarditis (PVE) involving mitral annulus. The patient received mitral valve replacement 8 years ago. He admitted for the management of acute cerebral stroke 3 weeks before referral to our institution and brain MRI suggested an embolic stroke of unknown origin. The echocardiogram revealed a suspicious 1.1 x 0.5 cm-sized oscillating mass lesion attached to the mitral annulus (Figure 1) and the growth of S.epidermidis was observed in 2 consecutive blood culture studies. However, the patient showed no definite fever or serum marker of infection and the diagnosis of PVE was equivocal.
Therefore, F-18 FDG PET was performed to confirm the diagnosis of PVE. The patient fasted for 21 hours and 50 IU/kg of unfractionated heparin was administered 15 minutes before FDG injection. The PET image revealed focal definite uptake in the mitral prosthetic valve annulus (SUVmax = 4.1), confirming that the suspicious oscillating mass on the echocardiogram was PVE lesion (Figure 2a). Additionally, the sternotomy site showed linear FDG uptake along the surgical wound (Figure 2b). Because it had already been 8 years since the valve operation, the sternotomy site was suggested as the origin of infection. Vancomycin, gentamicin and rifampin were administered, and the negative conversion of bacterial growth was confirmed on blood culture.
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Figure 1. Transthoracic echocardiography revealed 1.1 x 0.5 cm-sized oscillating mass attached to the mitral annulus.
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Figure 2. F-18 FDG PET/CT showed definite focal uptake in the mitral annulus (a, arrow). Regarding the echocardiography images, the FDG uptake was anatomically co-localized to the oscillating mass. Sternotomy site showed linear FDG uptake along the surgical wound (b, dotted circle and arrow). It was suggested that the infectious origin of PVE was the surgical site infection of the sternotomy site.
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