Asbjørn M. Scholtens

Additional Heparin Preadministration Improves Cardiac Glucose Metabolism Suppression over Low-Carbohydrate Diet Alone in ¹⁸F-FDG PET Imaging.

Adequate suppression of cardiac glucose metabolism increases the interpretability and diagnostic reliability of 18F-FDG PET studies performed to detect cardiac inflammation and infection. There are no standardized guidelines, though prolonged fasting (>6 h), carbohydrate-restricted diets, fatty meals, and heparin loading all have been proposed. The aim of this study was to compare the 3 preparatory protocols used in our institution. Methods: 18F-FDG PET scans were selected and grouped according to 3 preparatory protocols (50 consecutive scans per group): 6-h fast (group 1), low-carbohydrate diet plus 12-h fast (group 2), and low-carbohydrate diet plus 12-h fast plus intravenous heparin preadministration (50 IU/kg) (group 3). Consecutive scans were retrospectively included from time frames during which the particular protocol was used. Group 1 included oncologic indications, and groups 2 and 3 infection or inflammation detection. Cardiac segments for which inflammation or infection foci had been confirmed on other imaging modalities were excluded from the analysis. 18F-FDG uptake in normal myocardium was scored according to a scale ranging from 0 (uptake less than that in left ventricle blood pool) to 4 (diffuse uptake greater than that in liver). Adequate suppression was defined as uptake less than that in liver and without any focus (scores 0–2). Results: Adequate suppression differed significantly between groups: 28% in group 1, 54% in group 2, and 88% in group 3 (P < 0.0001 for all comparisons). Conclusion: Single-dose heparin administration before 18F-FDG PET in addition to a low-carbohydrate diet significantly outperforms a low-carbohydrate diet alone in adequately suppressing cardiac glucose metabolism.

CT Angiography and 18F-FDG-PET Fusion Imaging for Prosthetic Heart Valve Endocarditis

IN PROSTHETIC HEART VALVE (PHV) ENDOCARDITIS, transthoracic echocardiography (TTE) and transesophageal echocardiography (TEE) may occasionally fail to recognize vegetations and periannular extensions (abscesses/mycotic aneurysms) due to acoustic shadowing by the metal PHV ring [(1)][1]. In

Differential FDG-PET Uptake Patterns in Uninfected and Infected Central Prosthetic Vascular Grafts

OBJECTIVE (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) scanning has been suggested as a means to detect vascular graft infections. However, little is known about the typical FDG uptake patterns associated with synthetic vascular graft implantation. The aim of the present study was to compare uninfected and infected central vascular grafts in terms of various parameters used to interpret PET images. METHODS From 2007 through 2013, patients in whom a FDG-PET scan was performed for any indication after open or endovascular central arterial prosthetic reconstruction were identified. Graft infection was defined as the presence of clinical or biochemical signs of graft infection with positive cultures or based on a combination of clinical, biochemical, and imaging parameters (other than PET scan data). All other grafts were deemed uninfected. PET images were analyzed using maximum systemic uptake value (SUVmax), tissue to background ratio (TBR), visual grading scale (VGS), and focality of FDG uptake (focal or homogenous). RESULTS Twenty-seven uninfected and 32 infected grafts were identified. Median SUVmax was 3.3 (interquartile range [IQR] 2.0-4.2) for the uninfected grafts and 5.7 for the infected grafts (IQR 2.2-7.8). Mean TBR was 2.0 (IQR 1.4-2.5) and 3.2 (IQR 1.5-3.5), respectively. On VGS, 44% of the uninfected and 72% of the infected grafts were judged as a high probability for infection. Homogenous FDG uptake was noted in 74% of the uninfected and 31% of the infected grafts. Uptake patterns of uninfected and infected grafts showed a large overlap for all parameters. CONCLUSION The patterns of FDG uptake for uninfected vascular grafts largely overlap with those of infected vascular grafts. This questions the value of these individual FDG-PET-CT parameters in identifying infected grafts.

Effect of antibiotics on FDG-PET/CT imaging of prosthetic heart valve endocarditis

Four consecutive 18F-FDG-PET/CT scans of the same patient with a prosthetic heart valve (PHV, Perimount 21 mm biological valve implanted 2 years prior) in the aortic position, with target-to-background ratios (TBR, SUVmax PHV divided by SUVmean aortic blood pool). Patient presented with fever, malaise, and diarrhoea after returning from a trip abroad. Fever persisted under initial antibiotic treatment with ceftriaxone and gentamycin, …

Positron Emission Tomography/Computed Tomography for Diagnosis of Prosthetic Valve Endocarditis

Please cite this article as: Tanis W, Scholtens A, Habets J, van den Brink RBA, van Herwerden LA, Chamuleau SAJ, Budde RPJ, Letter to the editor: Positron Emission Tomography/Computed Tomography for Diagnosis of Prosthetic Valve Endocarditis: Increased Valvular 18F-Fluorodeoxyglucose Uptake as a Novel Major Criterion, Journal of the American College of Cardiology (2013), doi: 10.1016/ j.jacc.2013.06.069.

Standardized uptake values in FDG PET/CT for prosthetic heart valve endocarditis: a call for standardization

BackgroundThe significance of and threshold values for the standardized uptake value (SUV) in FDG PET/CT to diagnose prosthetic heart valve (PHV) endocarditis (PVE) are unclear at present.MethodsA literature search was performed in the PubMed and EMBASE medical databases, comprising the following terms: (FDG OR *fluorode* OR *fluoro-de*) AND (endocarditis OR prosthetic heart valve OR valve replacement). Studies reporting SUVs correlated to the diagnosis of PVE were selected for analysis.Results8 studies were included, with a total of 330 PHVs assessed. SUVs for PVE varied substantially across studies due to differences in acquisition, reconstruction, and measurement protocols, with median SUVmax values for rejected PVE ranging from 0.5 to 4.9 and for definite PVE ranging from 4.2 to 7.4.ConclusionReported SUV values for PVE are not interchangeable between sites, and further standardization of quantification is desirable. To this end, optimal protocols for patient preparation, image acquisition, and reconstruction and measurement methods need to be standardized across centers.

High FDG uptake in the right ventricular myocardium of a pulmonary hypertension patient.

![Figure][1] A patient with pulmonary fibrosis and increasing shortness of breath was referred for 18F-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) scanning to assess pulmonary inflammation. On FDG PET imaging, high glucose metabolism was observed in the right ventricular

18F-fluorodeoxyglucose positron emission/computed tomography and computed tomography angiography in prosthetic heart valve endocarditis: from guidelines to clinical practice

The timely diagnosis of prosthetic heart valve endocarditis remains challenging yet of utmost importance. 18F-fluorodeoxyglucose (18 F-FDG) positron emission/computed tomography (PET/CT) and cardiac computed tomography angiography (CTA) were recently introduced as additional diagnostic tools in the most recent ESC guidelines on infective endocarditis. However, how to interpret PET/CT findings with regard to what is to be considered abnormal, what the potential confounders may be, as well as which patients benefit most from these additional imaging techniques and how to best perform them in these often-complex patients, remains unclear. This review focusses on factors regarding patient selection and image acquisition that need to be taken into account when employing 18F-FDG PET/CT and CTA in daily clinical practice, and the importance of a multidisciplinary Endocarditis Team herein. Furthermore, it emphasizes the need for standardized acquisition protocols and image interpretation, especially now that these techniques are starting to be widely embraced by the cardiovascular society.

Whole-Body Visualization of Ectopic Bone Formation of Arteries and Skin in Pseudoxanthoma Elasticum

Pseudoxanthoma elasticum (PXE), CD73 deficiency, generalized arterial calcification of infancy, and progeria involve accelerated medial arterial calcification (MAC) leading to premature cardiovascular morbidity and mortality. MAC is also observed in diabetes mellitus, chronic kidney disease, and the

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

Prosthetic heart valve (PHV) endocarditis (PVE) is a relatively uncommon complication after PHV implantation with an annual incidence of 0.3%–1.0% per patient, but one that carries a high degree of morbidity and mortality. Echocardiography is often the first imaging modality used to diagnose PVE, but has difficulty establishing the disease in as many as 30% of cases due to acoustic shadowing. It is no wonder that other imaging techniques have garnered increasing interest in the setting of this disease, with publications on Ffluorodeoxyglucose (FDG) positron emission tomography with CT attenuation correction (PET/CT) in the setting of endocarditis steadily increasing in recent years: from none before the year 1995 to 46 in the year 2016 alone. So compelling is the promise of FDG PET/CT for PVE that it was included in the 2015 ESC guidelines for the management of infective endocarditis. 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 F-FDG PET/CT (only if the prosthesis was implanted for[3 months) (...) should be considered a major criterion.’’ 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. Since then, multiple publications have included patients scanned less than three months (some less than two weeks) after implantation. Some explicitly describe true negative findings in scans within this time frame, including our own study in the current issue. In contrast, a recent study by Mathieu et al. which included 51 patients without PVE showed that elevated uptake of FDG in the absence of infection can occur as late as 8 years after implantation, and our own study showed false-positive late images in a patient 13 years after implantation. In other words, we now know that scanning relatively shortly after surgery does not preclude scans from being truly normal, and waiting does not solve the problem of potentially false-positive uptake. Although our dual-time-point study did not have histological confirmation of the underlying process in uninfected valves, the presence of a sterile inflammatory response from hosts against implanted bioprostheses has in fact been documented in a preclinical pig model, with inflammatory cells found on the border between host tissue and the prosthesis in histological evaluation of all explanted PHVs 6 months after implantation. As our knowledge of the various facets of FDG PET/CT imaging in the context of PVE has increased, understanding of the patterns of uptake clearly is of greater importance than the time after implantation. The Reprint requests: A. M. Scholtens, MD, Department of Nuclear Medicine, Meander Medical Center, Amersfoort, The Netherlands; a.scholtens@meandermc.nl J Nucl Cardiol 2017;24:1540–1. 1071-3581/