Patient preparation for cardiac fluorine-18 fluorodeoxyglucose positron emission tomography imaging of inflammation

Management of cardiac sarcoidosis

Cardiac sarcoidosis (CS) is a form of inflammatory cardiomyopathy associated with significant clinical complications such as high-degree atrioventricular block, ventricular tachycardia, and heart failure as well as sudden cardiac death. It is therefore important to provide an expert consensus statement summarizing the role of different available diagnostic tools and emphasizing the importance of a multidisciplinary approach. By integrating clinical information and the results of diagnostic tests, an accurate, validated, and timely diagnosis can be made, while alternative diagnoses can be reasonably excluded. This clinical expert consensus statement reviews the evidence on the management of different CS manifestations and provides advice to practicing clinicians in the field on the role of immunosuppression and the treatment of cardiac complications based on limited published data and the experience of international CS experts. The monitoring and risk stratification of patients with CS is also covered, while controversies and future research needs are explored.

Novel tracers to assess myocardial inflammation with radionuclide imaging

Myocardial inflammation plays a central role in the pathophysiology of various cardiac diseases. While FDG-PET is currently the primary method for molecular imaging of myocardial inflammation, its effectiveness is hindered by physiological myocardial uptake as well as its propensity for uptake by multiple disease-specific mechanisms. Novel radiotracers targeting diverse inflammatory immune cells and molecular pathways may provide unique insight through the visualisation of underlying mechanisms central to the pathogenesis of inflammatory cardiac diseases, offering opportunities for increased understanding of immunocardiology. Moreover, the potentially enhanced specificity may lead to better quantification of disease activity, aiding in the guidance and monitoring of immunomodulatory therapy. This review aims to provide an update on advancements in non-FDG radiotracers for imaging myocardial inflammatory diseases, with a focus on cardiac sarcoidosis, myocarditis, and acute myocardial infarction.

Contemporary Role of Positron Emission Tomography (PET) in Endocarditis: A Narrative Review

Endocarditis, a serious infectious disease, remains a diagnostic challenge in contemporary clinical practice. The advent of advanced imaging modalities has contributed significantly to the improved understanding and management of this complex disease. 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) imaging has shown remarkable potential in improving the diagnostic accuracy of endocarditis. In the update of the Modified Duke Criteria, in 2023, The International Society for Cardiovascular Infectious Diseases (ISCVID) Working Group recognized specific 18F-FDG PET/CT findings as a major diagnostic criterion, particularly in patient with prosthetic valve endocarditis. The ability of PET to visualize metabolic activity allows for the identification of infective foci and could differentiate between infective and non-infective processes. This review examines the clinical utility of PET in differentiating infective endocarditis from other cardiovascular pathologies, highlighting its sensitivity and specificity in detecting native and prosthetic valve infections, including patients with transcatheter aortic valve implantation (TAVI), cardiac implantable devices (CIEDs), and left ventricular assistance devices (LVAD). Also, practical aspects and indications are illustrated to optimize the quality of imaging and reduce potential false positive results. In conclusion, the current use of PET in endocarditis has become a valuable diagnostic tool; as technological advances continue, PET will play an increasingly important role in the multidisciplinary approach to the management of endocarditis.

The Role of Multimodality Imaging in Cardiomyopathy

PURPOSE OF REVIEW

There has been increasing use of multimodality imaging in the evaluation of cardiomyopathies.

RECENT FINDINGS

Echocardiography, cardiac magnetic resonance (CMR), cardiac nuclear imaging, and cardiac computed tomography (CCT) play an important role in the diagnosis, risk stratification, and management of patients with cardiomyopathies. Echocardiography is essential in the initial assessment of suspected cardiomyopathy, but a multimodality approach can improve diagnostics and management. CMR allows for accurate measurement of volumes and function, and can easily detect unique pathologic structures. In addition, contrast imaging and parametric mapping enable the characterization of tissue features such as scar, edema, infiltration, and deposition. In non-ischemic cardiomyopathies, metabolic and molecular nuclear imaging is used to diagnose rare but life-threatening conditions such amyloidosis and sarcoidosis. There is an expanding use of CCT for planning electrophysiology procedures such as cardioversion, ablations, and device placement. Furthermore, CCT can evaluate for complications associated with advanced heart failure therapies such as cardiac transplant and mechanical support devices. Innovations in multimodality cardiac imaging should lead to increased volumes and better outcomes.

Recurrence of an undifferentiated pleomorphic pulmonary artery sarcoma 8 years after initial presentation: a case report

Background

Primary cardiac tumors remain exceptionally rare, characterized by a poor prognosis. Among them, sarcomas originating in the pulmonary arteries constitute the most infrequent subgroup within primary cardiac sarcomas.

Case summary

This report presents the case of a 76-year-old female experiencing a recurrence of an undifferentiated pleomorphic intracardiac pulmonary artery sarcoma located in the right ventricular outflow tract, manifesting 8 years after initial remission. Successful outcomes were attained through a combination of surgical resection, state-of-the-art radiotherapy, and chemotherapy. This comprehensive approach proved essential for optimizing both survival and quality of life.

Discussion

The unexpectedly prolonged recurrence-free survival observed in this case underscores the effectiveness of the comprehensive multimodal treatment approach outlined in the existing literature. This highlights the pivotal role of a multidisciplinary strategy in addressing primary cardiac sarcomas, particularly those arising in the pulmonary arteries.

Multimodality Imaging of Cardiac Myxomas

Cardiac myxomas are the most common benign cardiac neoplasms. Echocardiography is the first-line imaging modality used to analyze cardiac masses, allowing the detection of tumor location, size, and mobility. However, additional imaging techniques are required to confirm the diagnosis, evaluate tissue characteristics of the mass, and assess potential invasion of surrounding structures. Second-line imaging includes cardiac magnetic resonance imaging (MRI) and/or computed tomography (CT) depending on availability and the patient's characteristics and preferences. The advantages of CT include its wide availability and fast scanning, which allows good image quality even in patients who have difficulty cooperating. MRI has excellent soft-tissue resolution and is the gold standard technique for noninvasive tissue characterization. In some cases, evaluation of the tumor metabolism using 18F-fluorodeoxyglucose positron emission tomography with CT may be useful, mainly if the differential diagnosis includes primary or metastatic cardiac malignancies. A cardiac myxoma can be identified by its characteristic location within the atria, typically in the left atrium attached to the interatrial septum. The main differential diagnoses include physiological structures in the atria like crista terminalis in the right atrium and the coumadin ridge in the left atrium, intracardiac thrombi, as well as other benign and malignant cardiac tumors. In this review paper, we describe the characteristics of cardiac myxomas identified using multimodality imaging and provide tips on how to differentiate myxomas from other cardiac masses.

Diagnosis and Management of Cardiac Sarcoidosis: A Scientific Statement From the American Heart Association

Cardiac sarcoidosis is an infiltrative cardiomyopathy that results from granulomatous inflammation of the myocardium and may present with high-grade conduction disease, ventricular arrhythmias, and right or left ventricular dysfunction. Over the past several decades, the prevalence of cardiac sarcoidosis has increased. Definitive histological confirmation is often not possible, so clinicians frequently face uncertainty about the accuracy of diagnosis. Hence, the likelihood of cardiac sarcoidosis should be thought of as a continuum (definite, highly probable, probable, possible, low probability, unlikely) rather than in a binary fashion. Treatment should be initiated in individuals with clinical manifestations and active inflammation in a tiered approach, with corticosteroids as first-line treatment. The lack of randomized clinical trials in cardiac sarcoidosis has led to treatment decisions based on cohort studies and consensus opinions, with substantial variation observed across centers. This scientific statement is intended to guide clinical practice and to facilitate management conformity by providing a framework for the diagnosis and management of cardiac sarcoidosis.

The active papillary muscle sign in 18F-FDG PET/CT cardiac sarcoidosis exams and its relationship with myocardial suppression

OBJECTIVE

Papillary muscle (PM) activity may demonstrate true active cardiac sarcoidosis (CS) or mimic CS in 18FDG-PET/CT if adequate myocardial suppression (MS) is not achieved. We aim to examine whether PM uptake can be used as a marker of failed MS and measure the rate of PM activity presence in active CS with different dietary preparations.

MATERIALS AND METHODS

We retrospectively reviewed PET/CTs obtained with three different dietary preparations. Diet-A: 24-h ketogenic diet with overnight fasting (n = 94); Diet-B: 18-h fasting (n = 44); and Diet-C: 72-h daytime ketogenic diet with 3-day overnight fasting (n = 98). Each case was evaluated regarding CS diagnosis (negative, positive, and indeterminant) and presence of PM activity. MaxSUV was measured from bloodpool, liver, and the most suppressed normal myocardium. Linear mixed-effects models were used to compare these factors between those with PM activity and those without.

RESULTS

PM activity was markedly lower in the Diet-C group compared with others: Diet-C: 6 (6.1%), Diet-A: 36 (38.3%), and Diet-B: 26 (59.1%) (p < 0.001). MyocardiumMaxSUV was higher, and MyocardiummaxSUV/BloodpoolmaxSUV, MyocardiummaxSUV/LivermaxSUV ratios were significantly higher in the cases with PM activity (p < 0.001). Among cases that used Diet-C and had PM activity, 66.7% were positive and 16.7% were indeterminate. If Diet-A or Diet-B was used, those with PM activity had a higher proportion of indeterminate cases (Diet-A: 61.1%, Diet-B: 61.5%) than positive cases (Diet-A: 36.1%, Diet-B: 38.5%).

CONCLUSION

Lack of PM activity can be a sign of appropriate MS. PM activity is less common with a specific dietary preparation (72-h daytime ketogenic diet with 3-day overnight fasting), and if it is present with this particular preparation, the likelihood that the case being true active CS might be higher than the other traditional dietary preparations.

Standardized ketogenic dietary preparation for metabolic PET imaging in suspected and known cardiac sarcoidosis

Aims

A major limitation of cardiac positron emission tomography (PET) with F18-fluorodeoxyglucose (F18-FDG) for the evaluation of cardiac sarcoidosis (CS) is associated with physiologic myocardial glucose uptake. The optimal dietary protocol to suppress physiologic myocardial F18-FDG uptake is not well-established. We aimed to evaluate the diagnostic performance of a novel dietary preparation using a ketone-based infant formula.

Methods and results

Between 2018 and 2021, consecutive studies using a ketogenic dietary preparation were identified (n = 198). The rate of non-diagnostic studies due to failure to suppress myocardial glucose was 7.1% (n = 14) with a similar incidence in diabetics (n = 6, 8.1%). Among studies reported to have no inflammation (n = 137), 130 studies (66%) had mean myocardial standardized uptake value (SUV) less than or equal to mean blood pool SUV.

Conclusion

Patient preparation with a ketone-based infant formula resulted in low rate of inappropriate myocardial glucose suppression in patients undergoing F18-FDG cardiac PET to evaluate CS.

Prospective Analysis of Immunosuppressive Therapy in Cardiac Sarcoidosis With Fluorodeoxyglucose Myocardial Accumulation: The PRESTIGE Study

BACKGROUND

Fluorodeoxyglucose positron emission tomography (18F-FDG-PET) can noninvasively assess active inflammatory myocardium in patients with cardiac sarcoidosis (CS). Prednisolone (PSL) is the initial drug of choice for active CS; however, its efficacy has not been prospectively evaluated. Moreover, there are no alternative systematic treatment strategies.

OBJECTIVES

The goal of this study was to evaluate the efficacy of methotrexate (MTX) in patients refractory to PSL assessed by using cardiac metabolic activity (CMA) in 18F-FDG-PET.

METHODS

A total of 59 patients with active CS were prospectively enrolled. CMA (standardized uptake value × accumulation area) was used as an indicator of active inflammation, and a 6-month regimen of PSL therapy was introduced, followed by a second FDG scan. Poor responders to PSL therapy (CMA reduction rate <70%) and patients with recurrent CS (CMA reduction rate ≥70% after initial PSL therapy but CMA recurred after an additional 6 months of therapy) were randomly assigned to the MTX or repeat PSL (re-PSL) therapy groups for another 6 months.

RESULTS

Fifty-six patients completed the initial 6-month PSL therapy regimen. Median CMA reduced from 203.3 to 1.0 (P < 0.001), and 47 patients were allocated to the response group, 9 to the poor response group, and 2 to the recurrent group. Accordingly, 11 patients were randomly assigned to the MTX (n = 5) or re-PSL (n = 6) groups. After 6 months, neither group showed a significant reduction in CMA values. MTX was comparable to re-PSL in reducing CMA.

CONCLUSIONS

The 6-month regimen of PSL was a potent therapeutic tool for active CS. When MTX was added to low-dose PSL in patients refractory to the initial PSL therapy, there was no significant difference compared with re-PSL. Further studies are needed to evaluate the therapeutic potential of MTX for active CS, including how MTX works when it is administered in higher doses or for longer periods.

Sarcoid heart disease and imaging

Cardiac sarcoidosis (CS) can mimic any cardiomyopathy due to its ability to manifest with a variety of clinical presentations. The exact prevalence of CS remains unknown but has been reported ranging from 2.3% to as high as 29.9% among patients presenting with new onset cardiomyopathy and/or atrioventricular block. Early and accurate diagnosis of CS is often challenging due to the nature of disease progression and lack of diagnostic reference standard. The current diagnostic criteria for CS are lacking in sensitivity and specificity. Here, we review the contemporary role of advanced imaging modalities such as cardiac magnetic resonance imaging and positron emission tomography/computed tomography imaging in diagnosing and prognosticating patients with CS.

Bilateral Carotid Artery Molecular Calcification Assessed by [18F] Fluoride PET/CT: Correlation with Cardiovascular and Thromboembolic Risk Factors

Atherosclerosis, a leading cause of mortality and morbidity worldwide, involves inflammatory processes that result in plaque formation and calcification. The early detection of the molecular changes underlying these processes is crucial for effective disease management. This study utilized positron emission tomography/computed tomography (PET/CT) with [18F] sodium fluoride (NaF) as a tracer to visualize active calcification and inflammation at the molecular level. Our aim was to investigate the association between cardiovascular risk factors and [18F] NaF uptake in the left and right common carotid arteries (LCC and RCC). A cohort of 102 subjects, comprising both at-risk individuals and healthy controls, underwent [18F] NaF PET/CT imaging. The results revealed significant correlations between [18F] NaF uptake and cardiovascular risk factors such as age (β = 0.005, 95% CI 0.003-0.008, p < 0.01 in LCC and β = 0.006, 95% CI 0.004-0.009, p < 0.01 in RCC), male gender (β = -0.08, 95% CI -0.173--0.002, p = 0.04 in LCC and β = -0.13, 95% CI -0.21--0.06, p < 0.01 in RCC), BMI (β = 0.02, 95% CI 0.01-0.03, p < 0.01 in LCC and β = 0.02, 95% CI 0.01-0.03, p < 0.01 in RCC), fibrinogen (β = 0.006, 95% CI 0.0009-0.01, p = 0.02 in LCC and β = 0.005, 95% CI 0.001-0.01, p = 0.01), HDL cholesterol (β = 0.13, 95% CI 0.04-0.21, p < 0.01 in RCC only), and CRP (β = -0.01, 95% CI -0.02-0.001, p = 0.03 in RCC only). Subjects at risk showed a higher [18F] NaF uptake compared to healthy controls (one-way ANOVA; p = 0.02 in LCC and p = 0.04 in RCC), and uptake increased with estimated cardiovascular risk (one-way ANOVA, p < 0.01 in LCC only). These findings underscore the potential of [18F] NaF PET/CT as a sensitive tool for the early detection of atherosclerotic plaque, assessment of cardiovascular risk, and monitoring of disease progression. Further research is needed to validate the technique's predictive value and its potential impact on clinical outcomes.

Association of longitudinal cardiac troponin trajectory with adverse events in patients with cardiac sarcoidosis

BACKGROUND

Although high-sensitivity cardiac troponins may be sensitive and easily repeatable markers of disease activity in patients with cardiac sarcoidosis (CS), the association between longitudinal cardiac troponin trajectory and adverse events remains unclear. This study aimed to clarify whether longitudinal cardiac troponin levels were associated with adverse events in patients with CS.

METHODS

We examined 63 consecutive CS-initiated prednisolone (PSL) patients with available longitudinal high-sensitivity cardiac troponin T (cTnT) data between December 2013 and March 2023. The area under the cTnT trajectory, which reflected cumulative cTnT release, was calculated to assess the association between longitudinal cTnT levels and adverse events. Patients were divided into two groups according to the median area under the cTnT trajectory per month. The primary outcome was a composite of sustained ventricular tachycardia or fibrillation, worsening heart failure, and sudden cardiac death (SCD).

RESULTS

In total, 463 cTnT measurements were collected over a median follow-up period of 30.4 (interquartile range [IQR] 15.6-34.2) months. The primary outcome was observed in 12 (19%) patients. A higher area under the cTnT trajectory was significantly associated with an increased incidence of the primary outcome (P = 0.027), while cTnT levels before and one month after initiation of PSL, and these changes were not related to adverse events (P = 0.179, 0.096, and 0.95, respectively).

CONCLUSIONS

Longitudinal cTnT trajectory following PSL initiation was associated with adverse cardiac events in patients with CS, suggesting that longitudinal measurement of cTnT would be useful for the early identification of high-risk patients.

Evaluation and Management of Cardiac Sarcoidosis with Advanced Imaging

A high clinical suspicion in the setting of appropriate history, physical exam, laboratory, and imaging parameters is often required to set the groundwork for diagnosis and management. Echocardiography may show septal thinning, evidence of systolic and diastolic dysfunction, along with impaired global longitudinal strain. Cardiac MRI reveals late gadolinium enhancement along with evidence of myocardial edema and inflammation on T2 weighted imaging and parametric mapping. 18F-FDG PET detects the presence of active inflammation and the presence of scar. Involvement of the right ventricle on MRI or PET confers a high risk for adverse cardiac events and mortality.

Tales from the future-nuclear cardio-oncology, from prediction to diagnosis and monitoring

Cancer and cardiovascular diseases (CVD) often share common risk factors, and patients with CVD who develop cancer are at high risk of experiencing major adverse cardiovascular events. Additionally, cancer treatment can induce short- and long-term adverse cardiovascular events. Given the improvement in oncological patients' prognosis, the burden in this vulnerable population is slowly shifting towards increased cardiovascular mortality. Consequently, the field of cardio-oncology is steadily expanding, prompting the need for new markers to stratify and monitor the cardiovascular risk in oncological patients before, during, and after the completion of treatment. Advanced non-invasive cardiac imaging has raised great interest in the early detection of CVD and cardiotoxicity in oncological patients. Nuclear medicine has long been a pivotal exam to robustly assess and monitor the cardiac function of patients undergoing potentially cardiotoxic chemotherapies. In addition, recent radiotracers have shown great interest in the early detection of cancer-treatment-related cardiotoxicity. In this review, we summarize the current and emerging nuclear cardiology tools that can help identify cardiotoxicity and assess the cardiovascular risk in patients undergoing cancer treatments and discuss the specific role of nuclear cardiology alongside other non-invasive imaging techniques.

Multimodality imaging assessment of primary pericardial rhabdomyosarcoma: a case report

Primary pericardial sarcomas are rare and lethal diseases. To date, only a few cases of primary pericardial sarcomas, such as rhabdomyosarcoma (RMS), have been reported. Since the unusual location of RMS in the pericardium makes it challenging to diagnose, precise diagnostic procedures are required. In this study, we present the case of a 23-year-old man who experienced postprandial obstruction and atypical precordial pain that lasted for a week. Echocardiography revealed a heterogeneous isoechoic pericardial mass with a significant pericardial effusion. Contrast-enhanced CT revealed a massive pericardial effusion along with an irregular, defined, heterogeneously enhancing mass that was located between the pericardium and diaphragm. PET-CT imaging showed an intense FDG uptake in the pericardial mass. Furthermore, cardiac MRI demonstrated malignant characteristics of the pericardial mass and provided a detailed visualization of its exact anatomical connection with both cardiac and extracardiac structures. Finally, a pathologic examination of a puncture biopsy specimen confirmed the diagnosis of primary pericardial RMS. Our case emphasizes the importance of multimodal imaging for the differential diagnosis and evaluation of cardiac involvement, while providing clinicians with crucial information for clinical treatment and decision-making.

Exploring the Utility of Cardiovascular Magnetic Resonance Radiomic Feature Extraction for Evaluation of Cardiac Sarcoidosis

BACKGROUND

The aim of this study is to explore the utility of cardiac magnetic resonance (CMR) imaging of radiomic features to distinguish active and inactive cardiac sarcoidosis (CS).

METHODS

Subjects were classified into active cardiac sarcoidosis (CS_active) and inactive cardiac sarcoidosis (CS_inactive) based on PET-CMR imaging. CS_active was classified as featuring patchy [¹⁸F]fluorodeoxyglucose ([¹⁸F]FDG) uptake on PET and presence of late gadolinium enhancement (LGE) on CMR, while CS_inactive was classified as featuring no [¹⁸F]FDG uptake in the presence of LGE on CMR. Among those screened, thirty CS_active and thirty-one CS_inactive patients met these criteria. A total of 94 radiomic features were subsequently extracted using PyRadiomics. The values of individual features were compared between CS_active and CS_inactive using the Mann-Whitney U test. Subsequently, machine learning (ML) approaches were tested. ML was applied to two sub-sets of radiomic features (signatures A and B) that were selected by logistic regression and PCA, respectively.

RESULTS

Univariate analysis of individual features showed no significant differences. Of all features, gray level co-occurrence matrix (GLCM) joint entropy had a good area under the curve (AUC) and accuracy with the smallest confidence interval, suggesting it may be a good target for further investigation. Some ML classifiers achieved reasonable discrimination between CS_active and CS_inactive patients. With signature A, support vector machine and k-neighbors showed good performance with AUC (0.77 and 0.73) and accuracy (0.67 and 0.72), respectively. With signature B, decision tree demonstrated AUC and accuracy around 0.7; Conclusion: CMR radiomic analysis in CS provides promising results to distinguish patients with active and inactive disease.

Role of Imaging in Cardiomyopathies

Imaging has a central role in the diagnosis, classification, and clinical management of cardiomyopathies. While echocardiography is the first-line technique, given its wide availability and safety, advanced imaging, including cardiovascular magnetic resonance (CMR), nuclear medicine and CT, is increasingly needed to refine the diagnosis or guide therapeutic decision-making. In selected cases, such as in transthyretin-related cardiac amyloidosis or in arrhythmogenic cardiomyopathy, the demonstration of histological features of the disease can be avoided when typical findings are observed at bone-tracer scintigraphy or CMR, respectively. Findings from imaging techniques should always be integrated with data from the clinical, electrocardiographic, biomarker, genetic and functional evaluation to pursue an individualised approach to patients with cardiomyopathy.

Pancreatic involvement in Erdheim-Chester disease: Rare presentation of a rare disease

Erdheim-Chester disease (ECD) as a rare non-Langerhans histiocytosis has various clinical manifestations. It is characterized histologically by infiltration of every organ, more commonly bone, retroperitoneum, cardiovascular and CNS systems with foamy, lipid -laden macrophage. Pancreatic involvement as a manifestation of this uncommon disease has very rarely been reported. Here we report a 73-year-old woman with ECD and pancreas involvement in CT, MRI and PET scans. We also aim to increase radiologist knowledge about considering ECD as a differential diagnosis for pancreas mass in the appropriate clinical situation.

Hot spot imaging in cardiovascular diseases: an information statement from SNMMI, ASNC, and EANM

This information statement from the Society of Nuclear Medicine and Molecular Imaging, American Society of Nuclear Cardiology, and European Association of Nuclear Medicine describes the performance, interpretation, and reporting of hot spot imaging in nuclear cardiology. The field of nuclear cardiology has historically focused on cold spot imaging for the interpretation of myocardial ischemia and infarction. Hot spot imaging has been an important part of nuclear medicine, particularly for oncology or infection indications, and the use of hot spot imaging in nuclear cardiology continues to expand. This document focuses on image acquisition and processing, methods of quantification, indications, protocols, and reporting of hot spot imaging. Indications discussed include myocardial viability, myocardial inflammation, device or valve infection, large vessel vasculitis, valve calcification and vulnerable plaques, and cardiac amyloidosis. This document contextualizes the foundations of image quantification and highlights reporting in each indication for the cardiac nuclear imager.

Radionuclide Imaging of Infective Endocarditis

Infective endocarditis (IE) is associated with high morbidity and mortality. Early diagnosis is crucial for adequate patient management. Due to difficulties in the diagnosis, a multidisciplinary discussion in addition to the integration of clinical signs, microbiology data, and imaging data is used. Imaging, including echocardiography, molecular imaging techniques, and coronary CT angiography (CTA) is central to detect infections involving heart valves and implanted cardiovascular devices, also allowing for early detection of septic emboli and metastatic. This article describes the main clinical application of white blood cell SPECT/CT and [¹⁸F]FDG-PET/CT and CTA in IE and infections associated with cardiovascular implantable electronic devices.

Imaging of Endocarditis and Cardiac Device-Related Infections: An Update

IE is a deadly disease requiring prompt diagnosis for adequate patient's management. The diagnosis requires the integration of clinical signs, microbiology data and imaging data and proper discussion within a multidisciplinary team, the endocarditis team. Since the introduction of ¹⁸F-FDG-PET/CT and WBC SPECT/CT in the diagnostic algorithm of PVE the nuclear medicine imaging specialists is active part of the Endocarditis Team, requiring proper knowledge of dedicated imaging acquisition protocols, expertise for imaging reading and interpretations to select the best test or combination of tests for each specific clinical situation. In this manuscript, we will review the main technical aspects of each imaging procedure, the most recent literature with specific regards to special challenging populations and provide clinical examples.

FDG PET/CT Imaging of Sarcoidosis

Sarcoidosis is a multisystemic granulomatous disease of unknown etiology. The diagnostic can be made by histological identification of non-caseous granuloma or by a combination of clinical criteria. Active inflammatory granuloma can lead to fibrotic damage. Although 50% of cases resolve spontaneously, systemic treatments are often necessary to decrease symptoms and avoid permanent organ dysfunction, notably in cardiac sarcoidosis. The course of the disease can be punctuated by exacerbations and relapses and the prognostic depends mainly on affected sites and patient management. FDG-PET/CT along with newer FDG-PET/MR have emerged as key imaging modalities in sarcoidosis, namely for certain diagnostic purposes, staging and biopsy guiding. By identifying with a high sensitivity inflammatory active granuloma, FDG hybrid imaging is a main prognostic tool and therapeutic ally in sarcoidosis. This review aims to highlight the actual critical roles of hybrid PET imaging in sarcoidosis and display a brief perspective for the future which appears to include other radiotracers and artificial intelligence applications.

The utility of beta-hydroxybutyrate in detecting myocardial glucose uptake suppression in patients undergoing inflammatory [18F]-FDG PET studies

PURPOSE

We evaluated whether serum beta-hydroxybutyrate (BHB) can identify adequate suppression of the left ventricle (LV) among patients undergoing [18F]-fluorodeoxyglucose positron emission tomography ([18F]-FDG PET) for cardiac inflammatory/infectious studies.

METHODS

Consecutive patients who underwent [18F]-FDG PET imaging were included. Serum BHB levels were measured in all patients on the day of imaging prior to injecting [18F]-FDG. Myocardial [18F]-FDG suppression was defined if [18F]-FDG uptake in the walls of myocardium, measured using standardized uptake values (SUV), was lower than the blood pool. The optimal threshold of BHB to identify myocardial suppression was based on receiver operating characteristics (ROC) in a random 30% sample of the study population (derivation cohort) and tested in the remaining 70% of sample (validation cohort).

RESULTS

A total of 256 images from 220 patients were included. Patients with sufficient LV suppression had significantly higher BHB levels compared to those with non-suppressed myocardium (median (IQR) BHB 0.6 (0.3-0.8) vs. 0.2 (0.2-0.3) mmol/l, p < 0.001, respectively). BHB level ≥ 0.335 mmol/l had a sensitivity of 84.90% and a specificity of 92.60% to identify adequate LV suppression in the validation cohort. All patients (100%) with BHB ≥ 0.41 mmol/l had adequate myocardial suppression compared to 29.63% of patients with BHB ≤ 0.20 mmol/l.

CONCLUSION

Serum BHB level can be used at the point of care to identify sufficient LV suppression in patients undergoing [18F]-FDG PET cardiac inflammatory/infectious studies. Central illustration (image to the right) shows representative cases of patient images and BHB and, in the image to the left, shows the sensitivity and specificity to identify left myocardial suppression using BHB in validation group.

Cardiac sarcoidosis: the role of cardiac MRI and 18F-FDG-PET/CT in the diagnosis and treatment follow-up

Sarcoidosis is a multi-factorial inflammatory disease characterised by the formation of non-caseating granulomas in the affected organs. Cardiac involvement can be the first, and occasionally the only, manifestation of sarcoidosis. The prevalence of cardiac sarcoidosis (CS) is higher than previously suspected. CS is associated with increased morbidity and mortality. Thus, early diagnosis is critical to introducing immunosuppressive therapy that could prevent an adverse outcome. Endomyocardial biopsy (EMB) has limited utility in the diagnostic pathway of patients with suspected CS. As a result, advanced imaging modalities, i.e. cardiac magnetic resonance imaging (MRI) and positron emission tomography with 18F-Fluorodeoxyglucose/computed tomography scan (18F-FDG-PET/CT), have emerged as alternative tools for diagnosing CS and might be considered the new 'gold standard'. This focused review will discuss the epidemiology and pathology of CS, when to suspect and evaluate CS, highlight the complementary roles of cardiac MRI and 18F-FDG-PET/CT, and their diagnostic and prognostic values in CS, in the current content of guidelines for the diagnostic workflow of CS.

Value of rest 18F-FDG myocardial imaging in the diagnosis of obstructive coronary artery disease in Chinese patients with suspected unstable angina: A prospective real-world clinical study

BACKGROUND

This study aimed to determine the clinical value of rest 18F-FDG imaging in Chinese patients with non-acute chest pain, normal ECG, negative troponin, and suspected UA.

METHODS

136 patients were prospectively included and underwent rest 18F-FDG PET imaging and coronary arteriography within 1 week.

RESULTS

Obstructive CAD was diagnosed in 71 patients, and stenosis ≥ 70% was confirmed in 130 vascular territories. At patients and vascular level, rest 18F-FDG imaging showed sensitivity of 62.0%, 47.7%, specificity of 92.3%, 94.2%, accuracy of 76.5%, 79.4%, PPV of 89.8% and 79.5%, and NPV of 69.0% and 79.4%. The AUCs were 0.771 and 0.710. Of 71 patients with obstructive CAD, rest 18F-FDG imaging showed sensitivity of 47.7% and 58.8%, specificity of 91.6% and 91.2%, accuracy of 64.8% and 80.4%, PPV of 89.9% and 76.9% and NPV of 52.8% and 81.6% in all vascular level and single-vessel disease. In patients with two- or three-vessel disease, rest 18F-FDG imaging had a diagnostic sensitivity, specificity, accuracy, PPV, and NPV of 43.8%, 93.3%, 50.5%, 97.7%, and 20.6%. The AUCs were 0.696, 0.750, and 0.685.

CONCLUSION

Rest 18F-FDG imaging performed certain overall diagnostic efficiency for obstructive CAD in Chinese patients with suspected UA, especially the excellent high PPV in identifying culprit ischemic territory in patients with multivessel disease.

A 65-Year-Old Male With Classic Cardiac Sarcoidosis: Case Report and Review of the Literature

Sarcoidosis is a systemic disease characterized by the formation of non-necrotizing granulomas, primarily involving the lungs and other organs such as the heart. The diagnosis of cardiac sarcoidosis can be difficult. The last set of diagnostic guidelines for diagnosis and treatment of cardiac sarcoidosis was published in 2019 by the Japanese Circulation Society (JCS). We describe a case of classic cardiac sarcoidosis and review the literature on clinical presentation, imaging, and management.

Case report: Disseminated Scedosporium apiospermum infection with invasive right atrial mass in a heart transplant patient

Scedosporium apiospermum associated endocarditis is extremely rare. We report a case of a disseminated S. apiospermum infection with an invasive right atrial mass in a 52-year-old male, 11 months after heart transplantation, referred to our institution for an endogenous endophthalmitis with a one-month history of diffuse myalgias and fatigue. The patient had been supported two times with extracorporeal membrane oxygenation (ECMO) during the first three postoperative months. The echocardiography on admission revealed a mass in the right atrium attached to a thickened lateral wall. The whole-body [18F]FDG PET/CT revealed systemic dissemination in the lungs, muscles, and subcutaneous tissue. Blood cultures were positive on day three for filamentous fungi later identified as S. apiospermum. The disease was refractory to a 3-week dual antifungal therapy with voriconazole and anidulafungin in addition to reduced immunosuppression, and palliative care was implemented.

Multimodality Imaging of Benign Primary Cardiac Tumor

Primary cardiac tumors (PCTs) are rare, with benign PCTs being relatively common in approximately 75% of all PCTs. Benign PCTs are usually asymptomatic, and they are found incidentally by imaging. Even if patients present with symptoms, they are usually nonspecific. Before the application of imaging modalities to the heart, our understanding of these tumors is limited to case reports and autopsy studies. The advent and improvement of various imaging technologies have enabled the non-invasive evaluation of benign PCTs. Although echocardiography is the most commonly used imaging examination, it is not the best method to describe the histological characteristics of tumors. At present, cardiac magnetic resonance (CMR) and cardiac computed tomography (CCT) are often used to assess benign PCTs providing detailed information on anatomical and tissue features. In fact, each imaging modality has its own advantages and disadvantages, multimodality imaging uses two or more imaging types to provide valuable complementary information. With the widespread use of multimodality imaging, these techniques play an indispensable role in the management of patients with benign PCTs by providing useful diagnostic and prognostic information to guide treatment. This article reviews the multimodality imaging characterizations of common benign PCTs.

Potential novel imaging targets of inflammation in cardiac sarcoidosis

Cardiac sarcoidosis (CS) is an inflammatory disease with high morbidity and mortality, with a pathognomonic feature of non-caseating granulomatous inflammation. While 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) is a well-established modality to image inflammation and diagnose CS, there are limitations to its specificity and reproducibility. Imaging focused on the molecular processes of inflammation including the receptors and cellular microenvironments present in sarcoid granulomas provides opportunities to improve upon FDG-PET imaging for CS. This review will highlight the current limitations of FDG-PET imaging for CS while discussing emerging new nuclear imaging molecular targets for the imaging of cardiac sarcoidosis.

Transcriptional and Immune Landscape of Cardiac Sarcoidosis

BACKGROUND

Cardiac involvement is an important determinant of mortality among sarcoidosis patients. Although granulomatous inflammation is a hallmark finding in cardiac sarcoidosis, the precise immune cell populations that comprise the granuloma remain unresolved. Furthermore, it is unclear how the cellular and transcriptomic landscape of cardiac sarcoidosis differs from other inflammatory heart diseases.

METHODS

We leveraged spatial transcriptomics (GeoMx digital spatial profiler) and single-nucleus RNA sequencing to elucidate the cellular and transcriptional landscape of cardiac sarcoidosis. Using GeoMX digital spatial profiler technology, we compared the transcriptomal profile of CD68+ rich immune cell infiltrates in human cardiac sarcoidosis, giant cell myocarditis, and lymphocytic myocarditis. We performed single-nucleus RNA sequencing of human cardiac sarcoidosis to identify immune cell types and examined their transcriptomic landscape and regulation. Using multichannel immunofluorescence staining, we validated immune cell populations identified by single-nucleus RNA sequencing, determined their spatial relationship, and devised an immunostaining approach to distinguish cardiac sarcoidosis from other inflammatory heart diseases.

RESULTS

Despite overlapping histological features, spatial transcriptomics identified transcriptional signatures and associated pathways that robustly differentiated cardiac sarcoidosis from giant cell myocarditis and lymphocytic myocarditis. Single-nucleus RNA sequencing revealed the presence of diverse populations of myeloid cells in cardiac sarcoidosis with distinct molecular features. We identified GPNMB (transmembrane glycoprotein NMB) as a novel marker of multinucleated giant cells and predicted that the MITF (microphthalmia-associated transcription factor) family of transcription factors regulated this cell type. We also detected additional macrophage populations in cardiac sarcoidosis including HLA-DR (human leukocyte antigen-DR)+ macrophages, SYTL3 (synaptotagmin-like protein 3)+ macrophages and CD163+ resident macrophages. HLA-DR+ macrophages were found immediately adjacent to GPMMB+ giant cells, a distinct feature compared with other inflammatory cardiac diseases. SYTL3+ macrophages were located scattered throughout the granuloma and CD163+ macrophages, CD1c+ dendritic cells, nonclassical monocytes, and T cells were located at the periphery and outside of the granuloma. Finally, we demonstrate mTOR (mammalian target of rapamycin) pathway activation is associated with proliferation and is selectively found in HLA-DR+ and SYLT3+ macrophages.

CONCLUSIONS

In this study, we identified diverse populations of immune cells with distinct molecular signatures that comprise the sarcoid granuloma. These findings provide new insights into the pathology of cardiac sarcoidosis and highlight opportunities to improve diagnostic testing.

Unravelling the role of macrophages in cardiovascular inflammation through imaging: a state-of-the-art review

Cardiovascular disease remains the leading cause of death and disability for patients across the world. Our understanding of atherosclerosis as a primary cholesterol issue has diversified, with a significant dysregulated inflammatory component that largely remains untreated and continues to drive persistent cardiovascular risk. Macrophages are central to atherosclerotic inflammation, and they exist along a functional spectrum between pro-inflammatory and anti-inflammatory extremes. Recent clinical trials have demonstrated a reduction in major cardiovascular events with some, but not all, anti-inflammatory therapies. The recent addition of colchicine to societal guidelines for the prevention of recurrent cardiovascular events in high-risk patients with chronic coronary syndromes highlights the real-world utility of this class of therapies. A highly targeted approach to modification of interleukin-1-dependent pathways shows promise with several novel agents in development, although excessive immunosuppression and resulting serious infection have proven a barrier to implementation into clinical practice. Current risk stratification tools to identify high-risk patients for secondary prevention are either inadequately robust or prohibitively expensive and invasive. A non-invasive and relatively inexpensive method to identify patients who will benefit most from novel anti-inflammatory therapies is required, a role likely to be fulfilled by functional imaging methods. This review article outlines our current understanding of the inflammatory biology of atherosclerosis, upcoming therapies and recent landmark clinical trials, imaging modalities (both invasive and non-invasive) and the current landscape surrounding functional imaging including through targeted nuclear and nanobody tracer development and their application.

Comparison of Exogenous Ketone Administration Versus Dietary Carbohydrate Restriction on Myocardial Glucose Suppression: A Crossover Clinical Trial

The ketogenic diet (KD) is the standard of care to achieve myocardial glucose suppression (MGS) for assessing inflammation using ¹⁸F-FDG PET. However, failure to suppress physiologic glucose uptake remains a significant diagnostic barrier. Although extending the duration of KD may be effective, exogenously delivered ketones may provide a convenient, reliable, and same-day alternative. The aims of our study were to determine whether exogenous ketone administration is noninferior to the KD to achieve MGS and whether serum β-hydroxybutyrate (BHB) levels can predict MGS. Methods: KEETO-CROSS (Ketogenic Endogenous versus Exogenous Therapies for myoCaRdial glucOse SuppresSion) is a crossover, noninferiority trial of the KD (endogenous ketosis) versus ketone ester ([KE] exogenous ketosis) drink. Twenty healthy participants were enrolled into 3 arms: weight-based KE drink, 24-h KD, and 72-h KD (n = 18 completed all arms). The primary outcome was achievement of complete MGS on PET (noninferiority margin 5%). The area under receiver-operating-characteristics (AUROC) of endogenous BHB levels (analyzed in a laboratory and by point-of-care device) for predicting MGS was analyzed in 37 scans completed on the KD. Results: The mean age was 30 ± 7 y, 50% were women, and 45% were nonwhite. The median achieved BHB levels (mmol/L) were 3.82 (25th-75th percentile, 2.55-4.97) (KE drink), 0.77 (25th-75th percentile, 0.58-1.02) (25th-75th percentile, 24-h KD), and 1.30 (25th-75th percentile, 0.80-2.24) (72-h KD). The primary outcome was achieved in 44% (KE drink), 78% (24-h KD), and 83% (72-h KD) of participants (noninferiority P = 0.97 and 0.98 for KE vs. 24-h and 72-h KD). Endogenous BHB levels robustly predicted MGS (AUROC, 0.88; 95% CI 0.71, 1.00). A BHB of 0.58 or more correctly classified 92% of scans. A point-of-care device provided comparable predictive value. Conclusion: In healthy volunteers, KE was inferior to KD for achieving MGS. Serum BHB is a highly predictive biomarker for MGS and can be clinically implemented upstream of ¹⁸F-FDG PET, with rapid facilitation by point-of-care testing, to reduce false-positive scans.

Diagnostic utility of fusion 18F-fluorodeoxyglucose positron emission tomography/cardiac magnetic resonance imaging in cardiac sarcoidosis

BACKGROUND

Although each 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) and cardiac magnetic resonance (CMR) imaging with late gadolinium enhancement (LGE) has been used to diagnose cardiac sarcoidosis (CS), active CS is still misdiagnosed.

METHODS

Active CS, diagnosed by PET alone, was defined as focal or focal on diffuse FDG uptake pattern. In fusion PET/CMR imaging, using a regional analysis with AHA 17-segment model, the patients were categorized into four groups: (1) PET-/LGE-, (2) PET+/LGE-, (3) PET+/LGE+, and (4) PET-/LGE+. PET+/LGE+ was defined as active CS.

RESULTS

74 Patients with suspected CS were enrolled. Between PET alone and fusion PET/CMR imaging, 20 cases had mismatch evaluations of active CS, and most had diffuse or focal on diffuse FDG uptake pattern on PET alone imaging. 40 Patients fulfilled the 2016 the Japanese Circulation Society diagnostic criteria for CS. The interobserver diagnostic agreement was excellent (κ statistics 0.89) and the overall accuracy for diagnosing CS was 87.8% in fusion PET/CMR imaging, which were superior to those in PET alone imaging (0.57 and 82.4%, respectively). In a sub-analysis of diffuse and focal on diffuse patterns, the agreement (κ statistics 0.86) and overall accuracy (81.8%) in fusion PET/CMR imaging were still better.

CONCLUSIONS

Fusion PET/CMR imaging with regional analysis offered reliable and accurate diagnosis of CS, covering low diagnostic area by FDG-PET alone.

Nuclear medicine imaging methods of radiation-induced cardiotoxicity

Breast cancer survival is significantly improved over the past decades due to major improvements in anti-tumor therapies and the implementation of regular screening, which leads to early detection of breast cancer. Therefore, it is of utmost importance to prevent patients from long-term side effects, including radiotherapy-induced cardiotoxicity. Radiotherapy may contribute to damage of myocardial structures on the cellular level, which eventually could result in various types of cardiovascular problems, including coronary artery disease and (non-)ischemic cardiomyopathy, leading to heart failure. These cardiac complications of radiotherapy are preceded by alterations in myocardial perfusion and blood flow. Therefore, early detection of these alterations is important to prevent the progression of these pathophysiological processes. Several radionuclide imaging techniques may contribute to the early detection of these changes. Single-Photon Emission Computed Tomography (SPECT) cameras can be used to create Multigated Acquisition scans in order to assess the left ventricular systolic and diastolic function. Furthermore, SPECT cameras are used for myocardial perfusion imaging with radiopharmaceuticals such as ^99mTc-sestamibi and ^99mTc-tetrofosmin. Accurate quantitative measurement of myocardial blood flow (MBF), can be performed by Positron Emission Tomography (PET), as the uptake of some of the tracers used for PET-based MBF measurement almost creates a linear relationship with MBF, resulting in very accurate blood flow quantification. Furthermore, there are PET and SPECT tracers that can assess inflammation and denervation of the cardiac sympathetic nervous system. Research over the past decades has mainly focused on the long-term development of left ventricular impairment and perfusion defects. Considering laterality of the breast cancer, some early studies have shown that women irradiated for left-sided breast cancer are more prone to cardiotoxic side effects than women irradiated for right-sided breast cancer. The left-sided radiation field in these trials, which predominantly used older radiotherapy techniques without heart-sparing techniques, included a larger volume of the heart and left ventricle, leading to increased unavoidable radiation exposure to the heart due to the close proximity of the radiation treatment volume. Although radiotherapy for breast cancer exposes the heart to incidental radiation, several improvements and technical developments over the last decades resulted in continuous reduction of radiation dose and volume exposure to the heart. In addition, radiotherapy reduces loco-regional tumor recurrences and death from breast cancer and improves survival. Therefore, in the majority of patients, the benefits of radiotherapy outweigh the potential very low risk of cardiovascular adverse events after radiotherapy. This review addresses existing nuclear imaging techniques, which can be used to evaluate (long-term) effects of radiotherapy-induced mechanical cardiac dysfunction and discusses the potential use of more novel nuclear imaging techniques, which are promising in the assessment of early signs of cardiac dysfunction in selected irradiated breast cancer patients.

Exploring the Utility of Radiomic Feature Extraction to Improve the Diagnostic Accuracy of Cardiac Sarcoidosis Using FDG PET

Background

This study aimed to explore the radiomic features from PET images to detect active cardiac sarcoidosis (CS).

Methods

Forty sarcoid patients and twenty-nine controls were scanned using FDG PET-CMR. Five feature classes were compared between the groups. From the PET images alone, two different segmentations were drawn. For segmentation A, a region of interest (ROI) was manually delineated for the patients' myocardium hot regions with standardized uptake value (SUV) higher than 2.5 and the controls' normal myocardium region. A second ROI was drawn in the entire left ventricular myocardium for both study groups, segmentation B. The conventional metrics and radiomic features were then extracted for each ROI. Mann-Whitney U-test and a logistic regression classifier were used to compare the individual features of the study groups.

Results

For segmentation A, the SUVmin had the highest area under the curve (AUC) and greatest accuracy among the conventional metrics. However, for both segmentations, the AUC and accuracy of the TBRmax were relatively high, &gt;0.85. Twenty-two (from segmentation A) and thirty-five (from segmentation B) of 75 radiomic features fulfilled the criteria: P-value &lt; 0.00061 (after Bonferroni correction), AUC &gt;0.5, and accuracy &gt;0.7. Principal Component Analysis (PCA) was conducted, with five components leading to cumulative variance higher than 90%. Ten machine learning classifiers were then tested and trained. Most of them had AUCs and accuracies ≥0.8. For segmentation A, the AUCs and accuracies of all classifiers are &gt;0.9, but k-neighbors and neural network classifiers were the highest (=1). For segmentation B, there are four classifiers with AUCs and accuracies ≥0.8. However, the gaussian process classifier indicated the highest AUC and accuracy (0.9 and 0.8, respectively).

Conclusions

Radiomic analysis of the specific PET data was not proven to be necessary for the detection of CS. However, building an automated procedure will help to accelerate the analysis and potentially lead to more reproducible findings across different scanners and imaging centers and consequently improve standardization procedures that are important for clinical trials and development of more robust diagnostic protocols.

A two-stage cardiac PET and late gadolinium enhancement MRI co-registration method for improved assessment of non-ischemic cardiomyopathies using integrated PET/MR

PURPOSE

Respiratory motion causes mismatches between PET images of the myocardium and the corresponding cardiac MR images in cardiac integrated PET/MR. The mismatch may affect the attenuation correction and the diagnosis of non-ischemic cardiomyopathies. In this study, we present a two-stage cardiac PET and MR late gadolinium enhancement (LGE) co-registration method, which seeks to improve diagnostic accuracy of non-ischemic cardiomyopathies via better image co-registration using an integrated whole-body PET/MR system.

METHODS

The proposed PET and LGE two-stage co-registration method was evaluated through comparison with one-stage direct co-registration and no-registration. One hundred and ninety-one slices of LGE and forty lesions were studied. Two trained nuclear medicine physicians independently assessed the displacement between LGE and PET to qualitatively evaluate the co-registration quality. The changes of the mean SUV in the normal myocardium and the LGE-enhanced lesions before and after image co-registration were measured to quantitatively evaluate the accuracy and value of image co-registration.

RESULTS

The two-stage method had an improved image registration score (4.93 ± 0.89) compared with the no-registration method (3.49 ± 0.84, p value < 0.001) and the single-stage method (4.23 ± 0.81, p value < 0.001). Furthermore, the two-stage method led to increased SUV value in the myocardium (3.87 ± 2.56) compared with the no-registration method (3.14 ± 1.92, p value < 0.001) and the single-stage method (3.32 ± 2.16, p value < 0.001). The mean SUV in the LGE lesion significantly increased from 2.51 ± 2.09 to 2.85 ± 2.35 (p value < 0.001) after the two-stage co-registration.

CONCLUSION

The proposed two-stage registration method significantly improved the co-registration between PET and LGE in integrated PET/MR imaging. The technique may improve diagnostic accuracy of non-ischemic cardiomyopathies via better image co-registration.

REGISTERED NO

DF-2020-085,2020.04.30.

OUP accepted manuscript

AIMS

The ketogenic diet (KD) is standard-of-care to achieve myocardial glucose suppression (MGS) for assessing inflammation using fluorine-18 fluorodeoxyglucose-positron emission tomography (FDG-PET). As KD protocols remain highly variable between centres (including estimation of nutrient intake by dietary logs for adequacy of dietary preparation), we aimed to assess the predictive utility of nutrient intake in achieving MGS.

METHODS AND RESULTS

Nineteen healthy participants underwent short-term KD, with FDG-PET performed after 1 and 3 days of KD (goal carbohydrate intake <20 g/day). Nutrient consumption was estimated from dietary logs using nutrition research software. The area under receiver operating characteristics (AUROC) of macronutrients (carbohydrate, fat, and protein intake) for predicting MGS was analysed. The association between 133 nutrients and 4 biomarkers [beta-hydroxybutyrate (BHB), non-esterified fatty acids, insulin, and glucagon] with myocardial glucose uptake was assessed using mixed effects regression with false discovery rate (FDR) correction. Median (25th-75th percentile) age was 29 (25-34) years, 47% were women, and 42% were non-white. Median (25th-75th percentile) carbohydrate intake (g) was 18.7 (13.1-30.7), 16.9 (10.4-28.7), and 21.1 (16.6-29.0) on Days 1-3. No macronutrient intake (carbohydrate, fat, or protein) predicted MGS (c-statistic 0.45, 0.53, 0.47, respectively). Of 133 nutrients and 4 biomarkers, only BHB was associated with myocardial glucose uptake after FDR correction (corrected P-value 0.003).

CONCLUSIONS

During highly supervised, short-term KD, approximately half of patients meet strict carbohydrate goals. Yet, in healthy volunteers, dietary review does not provide reassurance for adequacy of myocardial preparation since no clear thresholds for carbohydrate or fat intake reliably predict MGS.

Nuclear Imaging in Infective Endocarditis

Infective endocarditis (IE) is a life-threatening disease with stable prevalence despite prophylactic, diagnostic, and therapeutic advances. In parallel to the growing number of cardiac devices implanted, the number of patients developing IE on prosthetic valves and cardiac implanted electronic device (CIED) is increasing at a rapid pace. The diagnosis of IE is particularly challenging, and currently relies on the Duke-Li modified classification, which include clinical, microbiological, and imaging criteria. While echocardiography remains the first line imaging technique, especially in native valve endocarditis, the incremental value of two nuclear imaging techniques, ¹⁸F-fluorodeoxyglucose positron emission tomography with computed tomography (¹⁸F-FDG-PET/CT) and white blood cells single photon emission tomography with computed tomography (WBC-SPECT), has emerged for the management of prosthetic valve and CIED IE. In this review, we will summarize the procedures for image acquisition, discuss the role of ¹⁸F-FDG-PET/CT and WBC-SPECT imaging in different clinical situations of IE, and review the respective diagnostic performance of these nuclear imaging techniques and their integration into the diagnostic algorithm for patients with a suspicion of IE.

Stable Extent of Recurrently Active Cardiac and Cutaneous Sarcoidosis

Background: Recurrent or persistently active sarcoidosis is a risk factor for permanent organ damage. Whether this damage is due to accumulated focal injuries or progressive disease extent is not known, as the natural history of chronic inflammation in sarcoidosis is poorly characterized. The objective of this study is to determine the pattern of disease in recurrently active sarcoidosis.

Methods: We identified patients with recurrent cardiac sarcoidosis (N = 21) retrospectively from an imaging database, and with recurrent cutaneous sarcoidosis (N = 17) from a prospective registry. The longitudinal patterns of cardiac sarcoidosis were established by findings on cardiac positron emission tomography scans, and of cutaneous sarcoidosis by the validated Cutaneous Sarcoidosis Activity and Morphology Instrument clinical scoring system. Patterns of recurrent disease were compared to baseline findings.

Results: Recurrent sarcoidosis occurred in a nearly identical pattern and distribution as baseline disease, and spread of disease was rarely observed for both cardiac and cutaneous sarcoidosis: 97% of heart segments positive on recurrence scans were positive on baseline scans, and only one new region of facial disease was observed. In some cases, recurrence followed years of apparent remission.

Discussion: Across phenotypes, and across a long period of follow-up, the extent of sarcoidosis was stable in spite of fluctuations in disease activity. For patients with a demonstrated history of recurrent disease affecting critical organs, our findings support the need for long-term follow-up.

PET Imaging in Cardiac Sarcoidosis: A Narrative Review with Focus on Novel PET Tracers

Sarcoidosis is a multi-system inflammatory disease characterized by the development of inflammation and noncaseating granulomas that can involve nearly every organ system, with a predilection for the pulmonary system. Cardiac involvement of sarcoidosis (CS) occurs in up to 70% of cases, and accounts for a significant share of sarcoid-related mortality. The clinical presentation of CS can range from absence of symptoms to conduction abnormalities, heart failure, arrhythmias, valvular disease, and sudden cardiac death. Given the significant morbidity and mortality associated with CS, timely diagnosis is important. Traditional imaging modalities and histologic evaluation by endomyocardial biopsy often provide a low diagnostic yield. Cardiac positron emission tomography (PET) has emerged as a leading advanced imaging modality for the diagnosis and management of CS. This review article will summarize several aspects of the current use of PET in CS, including indications for use, patient preparation, image acquisition and interpretation, diagnostic and prognostic performance, and evaluation of treatment response. Additionally, this review will discuss novel PET radiotracers currently under study or of potential interest in CS.