IJCS | Volume 33, Nº1, January / February 2019

92 1. Thuny F, Grisoli D, Cautela J, Riberi A, Raoult D, Habib G. Infective endocarditis: prevention, diagnosis, and management. Can J Cardiol. 2014;30(9):1046-57. 2. Thuny F, Grisoli D, Collart F, Habib G, Raoult D. Management of infective endocarditis: challenges and perspectives. Lancet. 2012;379(9819):965-75. References Albano et al. PET and SPECT in endocarditis Int J Cardiovasc Sci. 2020;33(1):87-93 Review Article The 18F-FDGPET/CT has the advantage to be a whole- body study that allows the assessment of extracardiac sites of the disease, including clinically unsuspected distant foci, and more appropriate and timely intervention, including antibiotic therapy. In fact, whole-body 18F-FDG PET/CT leads to treatment modification in up to 35% of patients with IE. 28 Several factors, such as antimicrobial therapy, small vegetation size and elevated blood glucose level may impact the accuracy of PET/CT and increase the number of false negative findings. The difficulty to detect small vegetations is directly related to the resolution power of the PET/CT device (about 4-5 mm), which is aggravated in case of high FDG uptake in the surrounding myocardium. Physiological uptake of FDG is a common problem in the evaluation of heart infection; for this reason, preparation protocols before and/or after FDG injection were suggested, like dietary preparation for MS and heparin injection. However, different diets have been proposed in the literature, without consensus (Table 3). These MS protocols include patient preparation with the use of a low-carbohydrate and high-fat diet plus fasting for at least 6 hours, and use of heparin prior to imaging. Prolonged fasting and low-carbohydrate, high-fat diets lead to decreased insulin and blood glucose levels, and increased free fatty acid levels, reducing physiological FDG uptake. Heparin induces lipolysis and leads to an increase in free fatty acid levels. Another possible limitation affecting FDG evaluation of IE is the time between valve surgical procedure and PET/CT scan; PET/CT studies performed shortly after cardiac procedures can also be affected by the presence of inflammation foci near to the prostheses. Although 18F-FDG PET/CT is generally considered a method with higher accuracy than SPECT due to higher spatial resolution and detection efficiency, this was not observed in our results. In fact, in our analysis, both sensitivity and specificity ofWBC SPECTwere better than PET/CT. 18F-FDG PET/CT has several clear advantages over SPECT imaging such as the lack of blood handling, a shorter study time and high target-to-background ratio; however, a high specificity of 18F-FDG PET/CT requires specific protocols to increase diagnostic accuracy. 29,30 Limitation of the studies Several limitations affect the quality of our review on the role of SPECT and PET in IE such as the lack of multicenter studies, the low number of patients evaluated (also due to the rarity of this disease), and the heterogeneity of included papers. This heterogeneity arises from the diversity of patients’ characteristics, methodological aspects, reference standards and global quality of the studies. Conclusion Our findings support the utility of both WBC SPECT and 18F-FDGPET/CT as diagnostic tools in the study of IE, particularly in patients with prosthetic valve. Specific protocols including diet and/or heparin injection may improve the diagnostic performance of PET/CT. Author contributions Conception and design of the research: Bertagna F, Giubbini R. Acquisition of data: Albano D. Analysis and interpretation of the data: Albano D, Bertagna F, Giubbini R. Statistical analysis: Albano D. Writing of the manuscript: Albano D. Critical revision of themanuscript for intellectual content: Albano D, Bertagna F, Giubbini R. Potential Conflict of Interest No potential conflict of interest relevant to this article was reported. Sources of Funding There were no external funding sources for this study. Study Association This study is not associated with any thesis or dissertation work. Ethics approval and consent to participate This article does not contain any studies with human participants or animals performed by any of the authors.