Advanced imaging of cardiac sarcoidosis

Inflammation and Myocardial Blood Flow in Cardiac Sarcoidosis

PURPOSE OF THE REVIEW

Cardiac involvement in systemic sarcoidosis or isolated cardiac sarcoidosis plays a pivotal role in the clinical manifestation and prognostication. Active-inflammatory cardiac sarcoidosis is associated with a regional impairment of coronary microvascular function that may confer further detrimental effects on myocardial function needing further characterization.

RECENT FINDINGS

Clinical investigations with cardiac positron emission tomography/computed tomography in conjunction with 18F-fluorodeoxyglucose to determine myocardial inflammation and 13N-ammonia to quantify myocardial blood flow (MBF) in patients with known or suspected cardiac sarcoidosis outlined that sarcoidosis-induced myocardial inflammation was associated with adverse effects on corresponding regional coronary microvascular function. Notably, immune-suppressive treatment caused reductions in myocardial inflammation were paralleled by improvements of coronary microvascular dysfunction outlining direct adverse effect of inflammation on coronary arteriolar function. This review summarizes contributions of cardiac PET imaging in the identification and characterization of active-inflammatory cardiac sarcoidosis, its effect on coronary microvascular function, treatment responses, and prognostic implications.

Clinical characteristics and prognosis of patients with isolated cardiac sarcoidosis: Insights from the ILLUMINATE-CS study

AIM

Data on the clinical features and prognosis of patients with isolated cardiac sarcoidosis (iCS) are limited. This study evaluated the clinical characteristics and prognostic impact of iCS.

METHODS AND RESULTS

This was a secondary analysis of the ILLUMINATE-CS study, a multicentre, retrospective registry investigating the clinical characteristics and prognosis of cardiac sarcoidosis. iCS was diagnosed according to the 2016 Japanese Circulation Society (JCS) guidelines. Clinical characteristics and prognosis were compared between patients with iCS and systemic cardiac sarcoidosis (sCS). The primary outcome was a combined endpoint of all-cause death, hospitalization for heart failure, or fatal ventricular arrhythmia events. Among 475 patients with CS (mean age, 62.0 ± 10.9 years; female ratio, 59%) diagnosed by the JCS guidelines, 119 (25.1%) were diagnosed with iCS. Patients with iCS had a higher prevalence of a history of atrial fibrillation or hospitalization for heart failure, or lower left ventricular ejection fraction than those with sCS. During a median follow-up of 42.3 (interquartile range, 22.8-72.5) months, 141 primary outcomes (29.7%) occurred. Cox proportional hazard analysis revealed that iCS was a significant risk factor for the primary outcome in the unadjusted model (hazard ratio [HR] 1.62; 95% confidence interval [CI] 1.12-2.34; p = 0.011). However, this association was not retained after adjustment for other covariates (adjusted HR 1.27; 95% CI 0.86-1.88; p = 0.226).

CONCLUSIONS

Patients with iCS had more impaired cardiovascular function at the time of diagnosis than those with sCS. However, iCS was not independently associated with poor prognosis after adjustment for prognostic factors.

The assessment of left ventricular volume and function in gated small animal 18F-FDG PET/CT imaging: a comparative study of three commercially available software tools

BACKGROUND

Several software tools have been developed for gated PET imaging that use distinct algorithms to analyze tracer uptake, myocardial perfusion, and left ventricle volumes and function. Studies suggest that different software tools cannot be used interchangeably in humans. In this study, we sought to compare the left ventricular parameters in gated 18F-FDG PET/CT imaging in mice by three commercially available software tools: PMOD, MIM, and QGS.

METHODS AND RESULTS

Healthy mice underwent ECG-gated 18F-FDG imaging using a small-animal nanoPET/CT (Mediso) under isoflurane narcosis. Reconstructed gates PET images were subsequently analyzed in three different software tools, and cardiac volume and function (end-diastolic (EDV), end-systolic volumes (ESV), stroke volume (SV), and ejection fraction (EF)) were evaluated. While cardiac volumes correlated well between PMOD, MIM, and QGS, the left ventricular parameters and cardiac function differed in agreement using Bland-Altman analysis. EDV in PMOD vs. QGS: r = 0.85; p < 0.001, MIM vs. QGS: r = 0.92; p < 0.001, and MIM vs. PMOD: r = 0.88; p < 0.001, showed good correlations. Correlation was also found in ESV: PMOD vs. QGS: r = 0.48; p = 0.07, MIM vs QGS: r = 0.79; p < 0.001, and MIM vs. PMOD: r = 0.69; p < 0.01. SV showed good correlations in: PMOD vs. QGS: r = 0.73; p < 0.01, MIM vs. QGS: r = 0.86; p < 0.001, and MIM vs. PMOD: r = 0.92; p < 0.001. However, EF among correlated poorly: PMOD vs. QGS: r = -0.31; p = 0.26, MIM vs. QGS: r = 0.48; p = 0.07, and MIM vs. PMOD: r = 0.23; p = 0.41. Inter-class and intra-class correlation coefficient were > 0.9 underlining repeatability in using PMOD, MIM, and QGS for cardiac volume and function assessment.

CONCLUSIONS

All three commercially available software tools are feasible in small animal cardiac volume assessment in gated 18F-FDG PET/CT imaging. However, due to software-related differences in agreement analysis for cardiac volumes and function, PMOD, MIM, and QGS cannot be used interchangeably in murine research.

Cardiovascular positron emission tomography: established and emerging role in cardiovascular diseases

Cardiac positron emission tomography (PET) imaging has established themselves firmly as excellent and reliable functional imaging modalities in assessment of the spectrum of coronary artery disease. With the explosion of technology advances and the dream of flow quantification now a reality, the value of PET is now well realized. Cardiac PET has proved itself as precise imaging modality that provides functional imaging of the heart in addition to anatomical imaging. It has established itself as one of the best available techniques for evaluation of myocardial viability. Hybrid PET/computed tomography provides simultaneous integration of coronary anatomy and function with myocardial perfusion and metabolism, thereby improving characterization of the dysfunctional area and chronic coronary artery disease. The availability of quantitative myocardial blood flow evaluation with PET provides additional prognostic information and increases diagnostic accuracy in the management of patients with coronary artery disease. Hybrid imaging seems to hold immense potential in optimizing management of cardiovascular diseases and furthering clinical research.

Defining cardiac fibrosis complexity and regulation towards therapeutic development

Cardiac fibrosis is insidious, accelerating cardiovascular diseases, heart failure, and death. With a notable lack of effective therapies, advances in both understanding and targeted treatment of fibrosis are urgently needed. Remodelling of the extracellular matrix alters the biomechanical and biochemical cardiac structure and function, disrupting cell‐matrix interactions and exacerbating pathogenesis to ultimately impair cardiac function. Attempts at clinical fibrotic reduction have been fruitless, constrained by an understanding which severely underestimates its dynamic complexity and regulation. Integration of single‐cell sequencing and quantitative proteomics has provided new insights into cardiac fibrosis, including reparative or maladaptive processes, spatiotemporal changes and fibroblast heterogeneity. Further studies have revealed microenvironmental and intercellular signalling mechanisms (including soluble mediators and extracellular vesicles), and intracellular regulators including post‐translational/epigenetic modifications, RNA binding proteins, and non‐coding RNAs. This understanding of novel disease processes and molecular targets has supported the development of innovative therapeutic strategies. Indeed, targeted modulation of cellular heterogeneity, microenvironmental signalling, and intracellular regulation offer promising pre‐clinical therapeutic leads. Clinical development will require further advances in our mechanistic understanding of cardiac fibrosis and dissection of the molecular basis for fibrotic remodelling. This review provides an overview of the complexities of cardiac fibrosis, emerging regulatory mechanisms and therapeutic strategies, and highlights knowledge gaps and opportunities for further investigation towards therapeutic/clinical translation.

Sarcoid Heart Disease: Review of Current Knowledge

Sarcoidosis is a granulomatous disease with the potential of multiple organ system involvement and its etiology remains unknown. Cardiac involvement is associated with worse clinical outcome, and has been reported to be 20-30% in white and as high as 58% in Japanese populations with sarcoidosis. Clinical manifestations of cardiac sarcoidosis highly depend on the extent and location of granulomatous inflammation. The most frequent presentations include heart block, tachyarrhythmia, or heart failure. Endomyocardial biopsy is the most specific diagnostic test, but has poor sensitivity due to often patchy involvement. The diagnosis of cardiac sarcoidosis remains challenging due to nonspecific imaging findings. Both 18 F-fluorodeoxyglucose-positron emission tomography (FDG-PET) and cardiac magnetic resonance imaging can be used to evaluate cardiac sarcoidosis, but evaluate different stages of the disease process. FDG-PET detects metabolically active inflammatory cells while cardiac magnetic resonance imaging with late gadolinium enhancement reveals areas of myocardial necrosis and fibrosis. Aggressive therapy of symptomatic cardiac sarcoidosis is often sought due to the high risk of sudden death and/or progression to heart failure. Prednisone 20-40 mg a day is the recommended initial treatment. In refractory or severe cases, higher doses of prednisone, 1-1.5 mg/kg/d (or its equivalent) and addition of a steroid-sparing agent have been utilized. Methotrexate is added most commonly. Long-term improvement has been reported with the use of a combination of weekly methotrexate and prednisone versus prednisone alone. After initiation of treatment, a cardiac FDG-PET scan may be performed 2-3 months later to assess treatment response.

Various Aspects of Fasting on the Biodistribution of Radiopharmaceuticals

It is demonstrated that fasting can alter the biodistribution of radiopharmaceuticals in nuclear medicine. Various studies have highlighted that fasting is interpreted to be easy for physicians during PET study, fasting is one of the most important factors determining the usefulness of this protocol. It is well documented that fasting can suppress normal ¹⁸F-FDG PET uptake during nuclear cardiology. However, there is no consensus about the usefulness of fasting on radiopharmaceuticals, especially on ¹⁸F-FDG in PET imaging, but special attention should be paid to the setting of the fasting duration. Nevertheless, it does seem we still need extensive clinical studies in the future. The present study aims to review the various aspects of fasting, especially metabolic alteration on radiopharmaceutical biodistribution. In this study, we focused more on the effect of fasting on ¹⁸F-FDG biodistribution, which alters its imaging contrast in cardiology and cancer imaging. Therefore, shifting substrate metabolism from glucose to free fatty acids during fasting can be an alternative approach to suppress physiological myocardial uptake.

A Comprehensive Updated Review on Magnetic Nanoparticles in Diagnostics

Magnetic nanoparticles (MNPs) have been studied for diagnostic purposes for decades. Their high surface-to-volume ratio, dispersibility, ability to interact with various molecules and superparamagnetic properties are at the core of what makes MNPs so promising. They have been applied in a multitude of areas in medicine, particularly Magnetic Resonance Imaging (MRI). Iron oxide nanoparticles (IONPs) are the most well-accepted based on their excellent superparamagnetic properties and low toxicity. Nevertheless, IONPs are facing many challenges that make their entry into the market difficult. To overcome these challenges, research has focused on developing MNPs with better safety profiles and enhanced magnetic properties. One particularly important strategy includes doping MNPs (particularly IONPs) with other metallic elements, such as cobalt (Co) and manganese (Mn), to reduce the iron (Fe) content released into the body resulting in the creation of multimodal nanoparticles with unique properties. Another approach includes the development of MNPs using other metals besides Fe, that possess great magnetic or other imaging properties. The future of this field seems to be the production of MNPs which can be used as multipurpose platforms that can combine different uses of MRI or different imaging techniques to design more effective and complete diagnostic tests.

Interleukin-1 blockade in cardiac sarcoidosis: study design of the multimodality assessment of granulomas in cardiac sarcoidosis: Anakinra Randomized Trial (MAGiC-ART)

BACKGROUND

Sarcoidosis is an inflammatory disease characterized by the formation of granulomas, which involve the heart in up to 25% of patients. Cardiac sarcoidosis can lead to life threatening arrhythmias and heart failure. While corticosteroids have been used as a treatment for over 50 years, they are associated with hypertension, diabetes, and weight gain, further increasing cardiovascular risk. Interleukin-1 (IL-1) is the prototypical proinflammatory cytokine that works to activate the nuclear transcription factor NF-kB, one of the targets of glucocorticoids. IL-1 also plays an important role also in the pathophysiology of heart disease including atherosclerosis, myocardial infarction, and myocarditis.

METHODS

Building on a network of research collaborators developed in the Cardiac Sarcoidosis Consortium, we will investigate the feasibility and tolerability of treatment of CS with anakinra at two National Institute of Health Clinical and Translational Science Award (CTSA) hubs with expertise in cardiac sarcoidosis. In this pilot study, up to 28 patients with cardiac sarcoidosis will be recruited to compare the administration of an IL-1 blocker, anakinra, 100 mg daily on top of standard of care versus standard of care only for 28 days and followed for 180 days. Utilizing surrogate endpoints of changes in systemic inflammatory biomarkers and cardiac imaging, we aim to determine whether IL-1 blockade with anakinra can combat systemic and cardiac inflammation in patients with cardiac sarcoidosis.

DISCUSSION

The current trial demonstrates an innovative collaborative approach to clinical trial development in a rare, understudied disease that disproportionately affects females and minorities. Trial Registration The trial was registered prospectively with ClinicalTrials.gov on July 12, 2019, identifier NCT04017936.

PET Cardiac Imaging (Perfusion, Viability, Sarcoidosis, and Infection)

Cardiovascular disease is the leading cause of death worldwide. Given the increased availability of radiopharmaceuticals, improved positron emission tomography (PET) camera systems and proven higher diagnostic accuracy, PET is increasingly utilized in the management of various cardiovascular diseases. PET has high temporal and spatial resolution, when compared to Single Photon Emission Computed Tomography. In clinical practice, hybrid imaging with sequential PET and Computed Tomography acquisitions (PET/CT) or concurrent PET and Magnetic Resonance Imaging are standard. This article will review applications of cardiovascular PET/CT including myocardial perfusion, viability, cardiac sarcoidosis/inflammation, and infection.

Ten Questions Cardiologists Should Be Able to Answer About Cardiac Sarcoidosis: Case-Based Approach and Contemporary Review

Sarcoidosis is an inflammatory multisystemic disease of unknown etiology characterized by the formation of noncaseating epithelioid cell granulomas. Cardiac sarcoidosis might be life-threatening and its diagnosis and treatment remain a challenge nowadays. The aim of this review is to provide an updated overview of cardiac sarcoidosis and, through 10 practical clinical questions and real-life challenging case scenarios, summarize the main clinical presentation, diagnostic criteria, imaging findings, and contemporary treatment.

FDG-PET in possible cardiac sarcoidosis: Right ventricular uptake and high total cardiac metabolic activity predict cardiovascular events

BACKGROUND

Cardiac involvement accounts for the majority of morbidity and mortality in sarcoidosis. Pathological myocardial fluorodeoxyglucose (FDG)-uptake in positron emission tomography (PET) has been associated with cardiovascular events and quantitative metabolic parameters have been shown to add prognostic value. Our aim was to study whether the pattern of pathological cardiac FDG-uptake and quantitative parameters are able to predict cardiovascular events in patients with suspected cardiac sarcoidosis (CS).

METHODS

137 FDG-PET examinations performed in Tampere University Hospital were retrospectively analyzed visually and quantitatively. Location of pathological uptake was noted and pathological metabolic volume, average standardized uptake value (SUV), and total cardiac metabolic activity (tCMA) were calculated. Patients were followed for ventricular tachycardia, decrease in left ventricular ejection fraction, and death.

RESULTS

Eleven patients had one or more cardiovascular events during the follow-up. Five patients out of 12 with uptake in both ventricles had an event during follow-up. Eight patients had high tCMA (> 900 MBq) and three of them had a cardiovascular event. Right ventricular uptake and tCMA were significantly associated with cardiovascular events during follow-up (P-value .001 and .018, respectively).

CONCLUSIONS

High tCMA and right ventricular uptake were significant risk markers for cardiac events among patient with suspected CS.

Sarcoidosis: rarely a single system disorder

Sarcoidosis is a systemic disease with a number of extrapulmonary manifestations, rarely limited to a single system. The objective of this review is to provide a overview of the systemic features of sarcoidosis and their surveillance.

Sarcoidosis is disease that can affect any organ system, resulting in a number of complications that can cause significant morbidity and mortality, including ophthalmological and cardiac complications. A number of investigations play a role in identifying manifestations of sarcoidosis. Respiratory physicians have an important role to play in identifying complications and monitoring patients with sarcoidosis, as they may be the first to encounter them.

Sarcoidosis can involve any organ system, with several complications, particularly ophthalmological and cardiac disease, that are important to recognise in clinical practice and monitor, no matter one's area of expertisehttps://bit.ly/36oLXxm

Fluorodeoxyglucose Applications in Cardiac PET: Viability, Inflammation, Infection, and Beyond

With its high temporal and spatial resolution and relatively low radiation exposure, positron emission tomography (PET) is increasingly being used in the management of cardiac patients, particularly those with inflammatory cardiomyopathies such as sarcoidosis. This review discusses the role of PET imaging in assessing myocardial viability, inflammatory cardiomyopathies, and endocarditis; describes the different protocols needed to acquire images for specific imaging tests; and examines imaging interpretation for each image dataset-including identification of the mismatch defect in viability imaging, which is associated with significant improvement in LV function after revascularization. We also review the role of fluorodeoxyglucose PET in cardiac sarcoidosis diagnosis, the complementary role of magnetic resonance imaging in inflammatory cardiomyopathy, and the emerging use of cardiac PET in prosthetic valve endocarditis.

Functional significance of post-myocardial infarction inflammation evaluated by 18F-fluorodeoxyglucose imaging in swine model

BACKGROUND

The aim of the study was to investigate the relationship between post-myocardial infarction (MI) inflammation and left ventricular (LV) remodeling in a swine model by 18F-fluorodeoxyglucose (FDG) imaging.

METHODS

MI was induced in swine by balloon occlusion of the left anterior descending coronary artery. A series of FDG positron emission tomography (PET) images were taken within 2 weeks post-MI, employing a comprehensive strategy to suppress the physiological uptake of cardiomyocytes. Echocardiography was applied to evaluate LV volume, global and regional function. CD68+ macrophage and glucose transporters (GLUT-1, -3 and -4) were investigated by immunostaining.

RESULTS

The physiological uptake of myocardium was adequately suppressed in 92.3% of PET scans verified by visual analysis, which was further confirmed by the minimal expression of myocardial GLUT-4. Higher FDG uptake was observed in the infarct than in the remote area and persisted within the observational period of 2 weeks. The FDG uptake of infarcted myocardium on day 1 post-MI was correlated with LV global remodeling, and the FDG uptake of infarcted myocardium on days 1 and 8 post-MI had a trend of correlating with regional remodeling of the infarct area.

CONCLUSIONS

We here report a feasible swine model for investigating post-MI inflammation. FDG signal in the infarct area of swine persisted for a longer duration than has been reported in small animals. FDG activity in the infarct area could predict LV remodeling.

Clinical implication of myocardial FDG uptake pattern in oncologic PET: retrospective comparison study with stress myocardial perfusion imaging as the reference standard

OBJECTIVE

The purpose of this study was to determine the clinical implication of the myocardial FDG uptake patterns by comparing with the results of stress myocardial perfusion imaging (MPI) as the reference standard.

METHODS

By reviewing the medical records, 86 pairs of stress MPI and FDG PET/CT of 84 patients who underwent stress MPI and oncologic FDG PET/CT in 1 month were included in this study. The patterns of the myocardial FDG uptake were classified into five patterns such as 'low', 'diffuse', 'basal ring', 'focal high', and 'focal defect on diffuse high'. MPI was evaluated using a 5-point scoring model ranging from 0 (normal uptake) to 4 (uptake absent) based on the 17-segment model. The summed stress score of 4 or higher was defined as 'abnormal MPI'. Factors predictive of abnormal MPI were analyzed using a log-rank multivariate test and p < 0.05 was set as significant.

RESULTS

Abnormal MPI was observed in only 16 of 36 (44%) patients with 'low' pattern, 10 of 23 (43%) patients with 'diffuse high' pattern, and 1 of 9 (11%) patients with 'basal ring' pattern, but in 8 of 9 (89%) patients with 'focal high' pattern, and 8 of 9 (89%) patients with 'focal defect on diffuse high' pattern. The log-rank multivariate test revealed that 'focal high' and 'focal defect on diffuse high' pattern were correlated with an abnormal MPI.

CONCLUSIONS

These results indicate that further cardiac work-up might be helpful in the patients with 'focal high' pattern or 'focal defect on diffuse high' pattern of myocardial FDG at oncologic PET. A prospective study should be needed to further support this conclusion.

18F-FDG PET-Based Imaging of Myocardial Inflammation Predicts a Functional Outcome Following Transplantation of mESC-Derived Cardiac Induced Cells in a Mouse Model of Myocardial Infarction

Cellular inflammation following acute myocardial infarction has gained increasing importance as a target mechanism for therapeutic approaches. We sought to investigate the effect of syngeneic cardiac induced cells (CiC) on myocardial inflammation using 18F-FDG PET (Positron emission tomography)-based imaging and the resulting effect on cardiac pump function using cardiac magnetic resonance (CMR) imaging in a mouse model of myocardial infarction. Mice underwent permanent left anterior descending coronary artery (LAD) ligation inducing an acute inflammatory response. The therapy group received an intramyocardial injection of 10⁶ CiC into the border zone of the infarction. Five days after myocardial infarction, 18F-FDG PET was performed under anaesthesia with ketamine and xylazine (KX) to image the inflammatory response in the heart. Flow cytometry of the mononuclear cells in the heart was performed to analyze the inflammatory response. The effect of CiC therapy on cardiac function was determined after three weeks by CMR. The 18F-FDG PET imaging of the heart five days after myocardial infarction (MI) revealed high focal tracer accumulation in the border zone of the infarcted myocardium, whereas no difference was observed in the tracer uptake between infarct and remote myocardium. The CiC transplantation induced a shift in 18F-FDG uptake pattern, leading to significantly higher 18F-FDG uptake in the whole heart, as well as the remote area of the heart. Correspondingly, high numbers of CD11⁺ cells could be measured by flow cytometry in this region. The CiC transplantation significantly improved the left ventricular ejection function (LVEF) three weeks after myocardial infarction. The CiC transplantation after myocardial infarction leads to an improvement in pump function through modulation of the cellular inflammatory response five days after myocardial infarction. By combining CiC transplantation and the cardiac glucose uptake suppression protocol with KX in a mouse model, we show for the first time, that imaging of cellular inflammation after myocardial infarction using 18F-FDG PET can be used as an early prognostic tool for assessing the efficacy of cardiac stem cell therapies.

IgG4-related disease with possible myocardial involvement

IgG4-related disease is characterized by mass lesions, a dense lymphoplasmacytic infiltrate with immunohistochemical positivity for IgG4, storiform fibrosis and, frequently, elevated serum IgG4 levels. It can be multisystemic; however, myocardial involvement, which is objectively determined by imaging tests, has not been described in the medical literature. We report the case of a man with IgG4-related disease with possible myocardial involvement, detected by cardiac magnetic resonance. This raises the question of a differential diagnosis with other diseases such as sarcoidosis and Fabry disease, the differential diagnosis of which is of great importance due to its therapeutic impact.

Consecutive episodes of heart and kidney failure in an "otherwise" healthy young man

BACKGROUND

Acute renal failure is a rare occurrence in a patient with an unremarkable past medical history and should always lead to an in depth clinical study. The occurrence in the same healthy young subject, of consecutive episodes of heart failure and of acute renal failure is an even rarer event and should prompt diagnostic tests and restrict the diagnostic hypotheses.

CASE PRESENTATION

We present the case of a 28 year-old man who, while waiting to undergo assessment for a mild chronic kidney disease, was diagnosed with decompensated dilated cardiomyopathy and placed on diuretics and β-blockers. After few weeks he developed a non oligoanuric acute renal failure with a slight elevation of serum calcium. Renal biopsy proved suggestive for renal sarcoidosis; thus the hypothesis of systemic sarcoidosis with cardiac and renal involvement was possible avoiding further delay in initiation of therapy.

CONCLUSIONS

Cardiac sarcoidosis is usually silent but the majority of cases are diagnosed when cardiac symptoms are present in a patient with systemic sarcoidosis. Renal involvement with granulomatous interstitial nephritis is also quite rare and can be an unexpected finding at kidney biopsy. This case highlights the need to evaluate thoroughly clinical problems that do not fit in a specific scenario and emphasizes the importance of performing a kidney biopsy in case of kidney failure of unknown etiology.

18F-FDG-PET in Finnish patients with clinical suspicion of cardiac sarcoidosis: Female sex and history of atrioventricular block increase the prevalence of positive PET findings

INTRODUCTION

Fluorodeoxyglucose positron emission tomography (FDG-PET) is a non-invasive imaging modality that has been shown to be a feasible method to demonstrate myocardial inflammation. The aim of this study was to identify the patients suspected of having cardiac sarcoidosis (CS), who are most likely to benefit from PET imaging.

MATERIALS AND METHODS

137 patients suspected of having CS underwent a dedicated cardiac FDG-PET examination at Tampere University Hospital between August 2012 and September 2015. These examinations were retrospectively analyzed.

RESULTS

33 and 12 of the 137 patients had abnormal left and right ventricular (LV and RV) FDG-uptake, respectively. Abnormal LV-uptake and RV-uptake were significantly associated with female sex and a history of advanced AV-block (P < 0.05). Abnormal RV-uptake was also associated with ventricular tachycardia and atrial fibrillation (P < 0.05). 56% of the 27 female patients with a history of AV-block had a pathological PET finding compared to only 6% of the 49 male patients without a history of AV-block. There were 17 female patients with history of both AV-block and ventricular tachycardia, 71% of them had abnormal PET finding.

CONCLUSIONS

Abnormal FDG-PET findings were associated with female sex, AV-block, and arrhythmias in this clinical cohort.

FDG PET-CT findings of extra-thoracic sarcoid are associated with cardiac sarcoid: A rationale for using FGD PET-CT for cardiac sarcoid evaluation

PURPOSE

This retrospective study investigates the relationship between cardiac and extra-thoracic sarcoid findings on FDG PET-CT using a 72-hour pretest high-fat, high-protein, and very low-carbohydrate (HFHPVLC) diet.

PATIENTS AND METHODS

A total of 196 consecutive FDG PET-CT scans with 72-hour HFHPVLC diet preparation were performed between December 2014 and December 2015 in known sarcoid patients. Of these scans, 5 were excluded for non-adherence to diet preparation or underlying cancer. Cardiac and extra-thoracic sarcoid lesions were categorized and measured for radiotracer uptake.

RESULTS

A total of 188 patients had 191 eligible FDG PET/CT scans (3 follow-up scans), of which there were 20 (10%) positive, 6 indeterminate (3%), and 165 (86%) negative for CS. Among the 20 scans positive for CS, 8 (40%) had findings of both cardiac and extra-thoracic sarcoid.

CONCLUSION

Our study shows that 40% of CS patients also have FDG PET-CT findings of extra-thoracic sarcoid. This makes an intriguing case for FDG PET-CT use with pretest diet prep over cardiac MRI (CMR) for cardiac sarcoid evaluation, given that CMR is likely to overlook these extra-thoracic sites of disease.

Emerging imaging targets for infiltrative cardiomyopathy: Inflammation and fibrosis

Molecular imaging in infiltrative cardiomyopathies is increasingly penetrating the clinical arena. Current approaches target the infiltrate directly, or its metabolic, physiologic, or functional consequences. Inflammation may not just play a role as the infiltrative mechanism itself. It is also thought to play a key role in the development and progression of heart failure in general, because it promotes the development of tissue fibrosis. The cascade leading from tissue damage to inflammation and further to fibrosis and loss of function has emerged as a therapeutic target. This review focuses (1) on novel tracers of inflammation, which are on the brink of clinical applicability and may be more specific than the gross metabolic marker F-18 deoxyglucose; and (2) on novel biologic imaging targets in fibrosis, which may be exploited for interrogation of the crosstalk between inflammation and loss of contractile function. Ultimately, the success of any novel molecular imaging assay will depend on whether it can be used for successful guidance of novel, targeted therapies aiming at tissue regeneration.

Cardiac Magnetic Resonance Imaging for Diagnosis of Cardiac Sarcoidosis: A Meta-Analysis

Background

Cardiac magnetic resonance imaging (CMR) is an effective technique for the diagnosis of cardiac sarcoidosis (CS). The efficacy of CMR versus the Japanese Ministry of Health and Welfare (JMHW) guidelines considered as standard criterion for the diagnosis of CS remains to be elucidated.

Methods

In this systematic review and meta-analysis, we aimed at assessing the diagnostic accuracy of CMR in cardiac sarcoidosis. We searched on PubMed from January 1, 1980, to March 28, 2018, on Embase from January 1, 1980, to March 29, 2018, and on the Cochrane Library from January 1, 1980, to April 1, 2018, using a strategy based on the search terms (sarcoidosis and magnetic resonance imaging) independently. We analyzed the data obtained with Revman 5.3 and Stata 14.0 software.

Results

Eight studies with a total of 649 participants met the inclusion criteria, and data were extracted. CMR had an overall sensitivity of 0.93 (95% confidence interval (CI), 0.87–0.97) and specificity of 0.85 (95% CI, 0.68–0.94) for the diagnosis of cardiac sarcoidosis. The area under the summary receiver operating characteristic (SROC) curve was 0.95 (95% CI, 0.93–0.97). The subgroup analysis via public year showed that studies between 2011 and 2017 had an overall sensitivity of 0.95 (95% CI, 0.88–0.98) and specificity of 0.92 (95% CI, 0.49–0.99), with an area under the SROC curve being 0.96.

Conclusions

The results of this meta-analysis suggest that CMR could be used for the diagnosis of cardiac sarcoidosis and screening of patients suspected of CS. With the improvement of the technique, the diagnostic accuracy of MRI has improved.

Hybrid cardiac imaging using PET/MRI: a joint position statement by the European Society of Cardiovascular Radiology (ESCR) and the European Association of Nuclear Medicine (EANM)

Positron emission tomography (PET) and magnetic resonance imaging (MRI) have both been used for decades in cardiovascular imaging. Since 2010, hybrid PET/MRI using sequential and integrated scanner platforms has been available, with hybrid cardiac PET/MR imaging protocols increasingly incorporated into clinical workflows. Given the range of complementary information provided by each method, the use of hybrid PET/MRI may be justified and beneficial in particular clinical settings for the evaluation of different disease entities. In the present joint position statement, we critically review the role and value of integrated PET/MRI in cardiovascular imaging, provide a technical overview of cardiac PET/MRI and practical advice related to the cardiac PET/MRI workflow, identify cardiovascular applications that can potentially benefit from hybrid PET/MRI, and describe the needs for future development and research. In order to encourage its wide dissemination, this article is freely accessible on the European Radiology and European Journal of Hybrid Imaging web sites.

KEY POINTS

• Studies and case-reports indicate that PET/MRI is a feasible and robust technology. • Promising fields of application include a variety of cardiac conditions. • Larger studies are required to demonstrate its incremental and cost-effective value. • The translation of novel radiopharmaceuticals and MR-sequences will provide exciting new opportunities.

High-Risk Sarcoidosis. Current Concepts and Research Imperatives

Sarcoidosis is a disease with heterogeneous manifestations and outcomes, varying in part on the basis of organ involvement. Specifically, patients with sarcoidosis at risk for poor outcomes include individuals with treatment-resistant pulmonary sarcoidosis, including fibrotic pulmonary disease and pulmonary hypertension, as well as those with cardiac, neurologic, and multiorgan disease. The limited but available data relating to these patients with high-risk sarcoidosis, defined as those patients with presentations requiring medical intervention to avoid progressive disability or premature death, was evaluated as part of the National Heart, Lung, and Blood Institute's workshop to improve understanding of these disease manifestations. In particular, knowledge gaps that preclude a greater understanding of the pathogenesis and management of these severe sarcoidosis clinical phenotypes were identified in the workshop. Research strategies are proposed to address critical knowledge gaps that would further our understanding of these disease manifestations and enhance the care of these patients.

Clinical use of cardiac PET/MRI: current state-of-the-art and potential future applications

Combined PET/MRI is a novel imaging method integrating the advances of functional and morphological MR imaging with PET applications that include assessment of myocardial viability, perfusion, metabolism of inflammatory tissue and tumors, as well as amyloid deposition imaging. As such, PET/MRI is a promising tool to detect and characterize ischemic and non-ischemic cardiomyopathies. To date, the greatest benefit may be expected for diagnostic evaluation of systemic diseases and cardiac masses that remain unclear in cardiac MRI, as well as for clinical and scientific studies in the setting of ischemic cardiomyopathies. Diagnosis and therapeutic monitoring of cardiac sarcoidosis has the potential of a possible 'killer-application' for combined cardiac PET/MRI. In this article, we review the current evidence and discuss current and potential future applications of cardiac PET/MRI.

PET/MRI: Where might it replace PET/CT?

Simultaneous positron emission tomography and MRI (PET/MRI) is a technology that combines the anatomic and quantitative strengths of MR imaging with physiologic information obtained from PET. PET and computed tomography (PET/CT) performed in a single scanning session is an established technology already in widespread and accepted use worldwide. Given the higher cost and complexity of operating and interpreting the studies obtained on a PET/MRI system, there has been question as to which patients would benefit most from imaging with PET/MRI versus PET/CT. In this article, we compare PET/MRI with PET/CT, detail the applications for which PET/MRI has shown promise and discuss impediments to future adoption. It is our hope that future work will prove the benefit of PET/MRI to specific groups of patients, initially those in which PET/CT and MRI are already performed, leveraging simultaneity and allowing for greater degrees of multiparametric evaluation.

LEVEL OF EVIDENCE

5 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2017;46:1247-1262.

MR/PET Imaging of the Cardiovascular System

Cardiovascular imaging has largely focused on identifying structural, functional, and metabolic changes in the heart. The ability to reliably assess disease activity would have major potential clinical advantages, including the identification of early disease, differentiating active from stable conditions, and monitoring disease progression or response to therapy. Positron emission tomography (PET) imaging now allows such assessments of disease activity to be acquired in the heart, whereas magnetic resonance (MR) scanning provides detailed anatomic imaging and tissue characterization. Hybrid MR/PET scanners therefore combine the strengths of 2 already powerful imaging modalities. Simultaneous acquisition of the 2 scans also provides added benefits, including improved scanning efficiency, motion correction, and partial volume correction. Radiation exposure is lower than with hybrid PET/computed tomography scanning, which might be particularly beneficial in younger patients who may need repeated scans. The present review discusses the expanding clinical literature investigating MR/PET imaging, highlights its advantages and limitations, and explores future potential applications.

Comparative evaluation of 18F-FLT and 18F-FDG for detecting cardiac and extra-cardiac thoracic involvement in patients with newly diagnosed sarcoidosis

Background

¹⁸F-FDG PET has been used in sarcoidosis for diagnosis and determination of the extent of the disease. However, assessing inflammatory lesions in cardiac sarcoidosis using ¹⁸F-FDG can be challenging because it accumulates physiologically in normal myocardium. Another radiotracer, 3′-deoxy-3′-¹⁸F-fluorothymidine (¹⁸F-FLT), has been investigated as a promising PET tracer for evaluating tumor proliferative activity. In contrast to ¹⁸F-FDG, ¹⁸F-FLT uptake in the normal myocardium is low. The purpose of this retrospective study was to compare the uptake of ¹⁸F-FLT and ¹⁸F-FDG in the evaluation of cardiac and extra-cardiac thoracic involvement in patients with newly diagnosed sarcoidosis.

Data for 20 patients with newly diagnosed sarcoidosis were examined. ¹⁸F-FLT and ¹⁸F-FDG PET/CT studies had been performed at 1 h after each radiotracer injection. The patients had fasted for at least 18 h before ¹⁸F-FDG PET/CT but were given no special dietary instructions regarding the period before ¹⁸F-FLT PET/CT. Uptake of ¹⁸F-FLT and ¹⁸F-FDG was examined visually and semiquantitatively using maximal standardized uptake value (SUVmax).

Results

Two patients had cardiac sarcoidosis, 7 had extra-cardiac thoracic sarcoidosis, and 11 had both cardiac and extra-cardiac thoracic sarcoidosis. On visual analysis for diagnosis of cardiac sarcoidosis, 4/20 ¹⁸F-FDG scans were rated as inconclusive because the ¹⁸F-FDG pattern was diffuse, whereas no FLT scans were rated as inconclusive. The sensitivity of ¹⁸F-FDG PET/CT for detection of cardiac sarcoidosis was 85%; specificity, 100%; and accuracy, 90%. The corresponding values for ¹⁸F-FLT PET/CT were 92, 100, and 95%, respectively. Using semiquantitative analysis of cardiac sarcoidosis, the mean ¹⁸F-FDG SUVmax was significantly higher than the mean ¹⁸F-FLT SUVmax (P < 0.005). Both ¹⁸F-FDG and ¹⁸F-FLT PET/CT studies detected all 24 extra-cardiac lesions. Using semiquantitative analysis of extra-cardiac sarcoidosis, the mean ¹⁸F-FDG SUVmax was significantly higher than the mean ¹⁸F-FLT SUVmax (P < 0.001).

Conclusions

The results of this preliminary study suggest that ¹⁸F-FLT PET/CT can detect cardiac and extra-cardiac thoracic involvement in patients with newly diagnosed sarcoidosis as well as ¹⁸F-FDG PET/CT, although uptake of ¹⁸F-FLT in lesions was significantly lower than that of ¹⁸F-FDG. However, ¹⁸F-FLT PET/CT may be easier to perform since it requires neither prolonged fasting nor a special diet prior to imaging.

Cardiovascular PET/MR imaging: Quo Vadis?

With the recent advent of PET/MRI scanners, the combination of molecular imaging with a variety of known and novel PET radiotracers, the high spatial resolution of MRI, and its potential for multi-parametric imaging are anticipated to increase the diagnostic accuracy in cardiovascular disease detection, while providing novel mechanistic insights into the initiation and progression of the disease state. For the time being, cardiac PET/MRI emerges as potential clinical tool in the identification and characterization of infiltrative cardiac diseases, such as sarcoidosis, acute or chronic myocarditis, and cardiac tumors, respectively. The application of PET/MRI in conjunction with various radiotracer probes in the identification of the vulnerable atherosclerotic plaque also holds much promise but needs further translation and validation in clinical investigations. The combination of molecular imaging and creation of multi-parametric imaging maps with PET/MRI, however, are likely to set new horizons to develop predictive parameters for myocardial recovery and treatment response in ischemic and non-ischemic cardiomyopathy patients. Molecular imaging and multi-parametric imaging in cardiovascular disease with PET/MRI at current stage are at its infancy but bear a bright future.

Suppression of Myocardial 18F-FDG Uptake Through Prolonged High-Fat, High-Protein, and Very-Low-Carbohydrate Diet Before FDG-PET/CT for Evaluation of Patients With Suspected Cardiac Sarcoidosis

BACKGROUND

A major obstacle in using FDG-PET/CT to diagnose cardiac sarcoidosis (CS) is the unpredictable physiological myocardial FDG uptake. We hypothesized that a prolonged 72-hour pretest high-fat, high-protein, and very-low-carbohydrate (HFHPVLC) diet preparation could suppress physiologic myocardial uptake of FDG and thus help to identify active CS.

METHODS

This retrospective study included 215 FDG-PET/CT tests from 207 patients with biopsy-proven sarcoidosis and clinical suspicion for CS between July 2014 and December 2015. The patients were classified into 2 groups. Group 1 included 12 FDG-PET/CT scans from 12 patients who had 24-hour or less pretest HFHPVLC diet preparation. Group 2 included 203 FDG-PET/CT scans with 72-hour HFHPVLC diet before FDG-PET/CT. Nonadherent patients and patients with cancer were excluded. Cardiac FDG uptake was classified as: "none" and "ringlike diffuse at base" (negative for CS), "focal" (positive for CS), and "diffuse" (indeterminate for CS). FDG uptake in myocardial lesions was measured as SUVmax and compared with SUVmean of mediastinal blood pool. Final diagnoses were made with consensus among physicians in view of all available clinical information including cardiac MRI and echocardiogram results.

RESULTS

In group 1, there were 1 (1/12, 8.3%) positive, 5 (5/12, 41.7%) indeterminate, and 6 (6/12, 50.0%) negative for CS. In group 2, 10 patients were excluded (6 patients because of noncompliance with diet, 2 patients with concurrent diagnosis of cancers, 2 patients because of insulin and steroid use within 4 hours before PET/CT); the remaining 185 patients had 193 FDG PET/CT tests (8 repeats), of which there were 19 (19/193, 9.8%) positive, 7 indeterminate (7/193, 3.6%), and 167 (167/193, 86.7.%) negative for CS. The SUVmax of PET-positive myocardial lesions ranges from 3.4 to 12.5, whereas mediastinal blood pool SUVmean ranges from 1.1 to 3.6. The indeterminate rate was significantly lower in group 2 compared with group 1 (P < 0.001).

CONCLUSIONS

The prolonged 72-hour HFHPVLC diet preparation protocol successfully suppressed physiological myocardial FDG uptake and may permit a more sensitive and accurate method of diagnosing active CS using FDG PET/CT.

Novel Noninvasive Nuclear Medicine Imaging Techniques for Cardiac Inflammation

PURPOSE OF REVIEW

Inflammation is a key player in a wide range of cardiovascular and myocardial diseases. Given the numerous implications of inflammatory processes in disease initiation and progression, functional imaging modalities including positron emission tomography (PET) represent valuable diagnostic, prognostic, and monitoring tools in patient management. Since increased glucose metabolism is a hallmark of inflammation, PET using the radiolabeled glucose analog [18F]-2-deoxy-2-fluoro-d-glucose (FDG) is the mainstay diagnostic test for nuclear imaging of (cardiac) inflammation. Recently, new approaches using more specific tracers to overcome the limited specificity of FDG have emerged.

RECENT FINDINGS

PET imaging has proven its value in a number of inflammatory conditions of the heart including myocarditis, endocarditis, sarcoidosis, or reactive changes after myocardial infarction. In infection-related endocarditis, FDG-PET and white blood cell scintigraphy have been implemented in current guidelines. FDG-PET is considered as nuclear medical gold standard in myocarditis, pericarditis, or sarcoidosis. Novel strategies, including targeting of somatostatin receptors or C-X-C motif chemokine receptor CXCR4, have shown promising results in first studies.

SUMMARY

Nuclear medicine techniques offer valuable information in the assessment of myocardial inflammation. Given the possibility to directly visualize inflammatory activity, they represent useful tools for diagnosis, risk stratification, and therapy monitoring.

Effect of Bayesian-penalized likelihood reconstruction on [13N]-NH3 rest perfusion quantification

ABSTACT

OBJECTIVES: Myocardial blood flow (MBF) imaging is used in patients with suspected cardiac sarcoidosis, and also in stress/rest studies. The accuracy of MBF is dependent on imaging parameters such as new reconstruction methodologies. In this work, we aim to assess the impact of a novel PET reconstruction algorithm (Bayesian-penalized likelihood-BPL) on the values determined from the calculation of [13N]-NH3 MBF values.

METHODS

Data from 21 patients undergoing rest MBF evaluation [13N]-NH3 as part of sarcoidosis imaging were retrospectively analyzed. Each scan was reconstructed with a range of BPL coefficients (1-500), and standard clinical FBP and OSEM reconstructions. MBF values were calculated via an automated software routine for all datasets.

RESULTS

Reconstruction of [13N]-NH3 dynamic data using the BPL, OSEM, or FBP reconstruction showed no quantitative differences for the calculation of territorial or global MBF (P = .97). Image noise was lower using OSEM or BPL reconstructions than FBP and noise from BPL reached levels seen in OSEM images between B = 300 and B = 400. Intrasubject differences between all reconstructions over all patients in respect of all cardiac territories showed a maximum coefficient of variation of 9.74%.

CONCLUSION

Quantitation of MBF via kinetic modeling of cardiac rest MBF by [13N]-NH3 is minimally affected by the use of a BPL reconstruction technique, with BPL images presenting with less noise.

Regional myocardial damage and active inflammation in patients with cardiac sarcoidosis detected by non-invasive multi-modal imaging

AIMS

Cardiac sarcoidosis (CS) can be diagnosed using ¹⁸F-FDG-PET/CT (PET), cardiovascular magnetic resonance (CMR), and ¹²³I-BMIPP/²⁰¹TlCl dual myocardial SPECT. This study aims to clarify the relationships among the three modalities with respect to CS.

METHODS AND RESULTS

We evaluated 16 patients (male n = 11; age 55 ± 13 years) with confirmed CS who underwent PET, CMR, and dual SPECT with gated SPECT before starting steroid therapy. The left ventricular myocardium was divided into 17 segments to obtain SUVmax for PET images, defect scores from 0 to 4 (0 normal; 4 absent), and mismatch scores for dual SPECT (BMDS, TLDS, and MS) images and late gadolinium enhancement (LGE) scores (0 none; 1 partly positive; 2 homogeneous) on CMR images. Summed BMDS, TLDS, and MS were 18.6 ± 12.6, 12.9 ± 10.9, and 5.7 ± 3.1, respectively. The segmental BMDS and TLDS scores became significantly higher as the LGE scores increased. The MS scores were significantly higher in areas of LGE with a score of 1 than 0 (both, p < 0.001), but did not significantly differ between areas with LGE scores of 1 and 2. The SUVmax was significantly higher in LGE areas with a score of 1 than 0 (p < 0.025), but did not significantly differ between those with scores of 1 or 2.

CONCLUSION

Regions with a higher SUVmax indicating active myocardial inflammation were mainly located in areas with LGE, where BMIPP and TL mismatches were evident in patients with CS.