Confounders in FDG-PET/CT Imaging of Suspected Prosthetic Valve Endocarditis

Another potential step to improve prosthetic heart valve endocarditis imaging with 18F-FDG PET/CT

“…Other confounding factors that need to be taken into account such as unsuccessful suppression of myocardial FDG uptake despite optimal dietary preparation and prolonged fasting period of [12 h. 8 Such unsuccessful suppression of myocardial FDG uptake may manifest very focal in the basal segment directly adjacent to the prosthetic valve leading to a false-positive finding. 9 In addition, mild-to-moderate amount of FDG uptake around a prosthetic heart valve is commonly a normal finding likely owing to mild foreign body reaction and/or strain on the aortic wall. Other pitfalls of false-positive findings of PVE may be related to application of surgical adhesive during prosthetic valve implantation, the presence of atrial fibrillation with high energy consumption due to uncoordinated contraction of atrial myocytes, and lipomatous hypertrophy of the intertribal septum.…”

Radionuclide Imaging of Infective Endocarditis: State of Art and Future Perspective

“…In addition, the problem of false negative results in presence of small oscillating vegetation and metastatic foci <5 mm which are below the threshold of detectability/resolution has to be considered as well as the issue of radiation burden that might increase when certain protocol for imaging acquisition are applied (i.e. retrospective ECG-triggering) [6,29]. The best strategy to reduce false positive finding is correct patient preparation and selection.…”

FDG PET/CT in prosthetic heart valve endocarditis: There is no need to wait

“…6 Based on the knowledge available at the time, however, there was one caveat that accompanied the recommendation: ''In the setting of the suspicion of endocarditis on a prosthetic valve, abnormal activity around the site of implantation detected by 18 F-FDG PET/CT (only if the prosthesis was implanted for [3 months) (…) should be considered a major criterion.'' 6 The basis for this proposed ''grace period'' of three months after implantation was the assumed probability of false-positive findings based on sterile inflammation in the context of post-surgical healing, based on expert opinion at the time and a case report showing elevated metabolic activity surrounding a PHV in the aortic position 2 months after implantation without signs of PVE.…”

“…10,17 Homogenous uptake surrounding PHVs is a normal variant, especially if it is mild in intensity. 12,18 By contrast, focal or intense uptake is more likely to be related to infection. 12,17 Additionally, a number of confounders are known to mimic infection, notably the use of surgical adhesives during implantation.…”

“…12,17 Additionally, a number of confounders are known to mimic infection, notably the use of surgical adhesives during implantation. 18,19 In cases where FDG PET/CT is difficult to interpret, additional radiolabeled leukocyte scintigraphy may help to further differentiate inflammation from infection: although at the cost of a lower sensitivity, its specificity is higher than that of FDG PET/CT. 8 Finally, it is essential to incorporate all available information in a multidisciplinary approach to establish a final diagnosis.…”