Quantitative interpretation of FDG PET/CT with myocardial perfusion imaging increases diagnostic information in the evaluation of cardiac sarcoidosis

Imaging of Cardiac Sarcoidosis: An Update and Future Aspects

Cardiac sarcoidosis (CS), an increasingly recognized disease of unknown etiology, is associated with significant morbidity and mortality. Given the limited diagnostic yield of traditional endomyocardial biopsy (EMB), there is increasing reliance on multimodality cardiovascular imaging in the diagnosis and management of CS, with EMB being largely supplanted by the use of 18F-fluorodeoxyglucose (FDG-PET) and cardiac magnetic resonance imaging (CMR). This article aims to provide a comprehensive review of imaging modalities currently utilized in the screening, diagnosis, and monitoring of CS, while highlighting the latest developments in each area.

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.

Comparing the diagnostic performance of [18F]FDG PET/CT and [18F]FDG PET/MRI for detecting cardiac sarcoidosis: A meta-analysis

PURPOSE

This meta-analysis aimed to evaluate the comparative diagnostic efficacy of [18F]FDG PET/CT and [18F]FDG PET/MRI in detecting cardiac sarcoidosis.

METHODS

An extensive search was conducted in the PubMed and Embase databases to identify available publications up to November 2023. Studies were included if they evaluated the diagnostic efficacy of [18F]FDG PET/CT and [18F]FDG PET/MRI in patients with cardiac sarcoidosis. Sensitivity and specificity were evaluated using the DerSimonian and Laird method, with subsequent transformation via the Freeman-Tukey double inverse sine transformation. Publication bias was assessed using funnel plots and Egger's test.

RESULTS

16 articles involving 1361 patients were included in the meta-analysis. The overall sensitivity of [18F]FDG PET/CT in detecting cardiac sarcoidosis was 0.77(95%CI: 0.62-0.89), while the overall sensitivity of [18F]FDG PET/MRI was 0.94(95%CI: 0.84-1.00). The result indicated that [18F]FDG PET/MRI appears to a higher sensitivity in comparison to [18F]FDG PET/CT(P = 0.02). In contrast, the overall specificity of [18F]FDG PET/CT in detecting cardiac sarcoidosis was 0.90(95%CI: 0.85-0.94), while the overall specificity of [18F]FDG PET/MRI was 0.79(95%CI: 0.53-0.96), with no significant difference in specificity (P = 0.32).

CONCLUSIONS

Our meta-analysis indicates that [18F]FDG PET/MRI demonstrates superior sensitivity and comparable specificity to [18F]FDG PET/CT in detecting cardiac sarcoidosis. However, the small number of PET/MRI studies limited the evidence of current results. To validate these results, larger, prospective studies employing a head-to-head design are needed.

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 visualization 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.

Cardiac Sarcoidosis: Utilizing Cardiac MRI and PET-CT

PURPOSEOF REVIEW

Cardiac sarcoidosis is an inflammatory condition that has been associated with deleterious cardiac manifestations. The diagnosis of cardiac sarcoidosis is challenging and can be guided by advanced cardiac imaging.

RECENT FINDINGS

Endomyocardial biopsy lacks sensitivity in confirming a diagnosis of cardiac sarcoidosis. Studies have shown that the use of cardiac magnetic resonance imaging (MRI) and cardiac Positron Emission Testing (PET) are associated with increased sensitivity and specificity in the diagnosis of cardiac sarcoidosis. Cardiac MRI and cardiac PET CT, although distinct entities, are complimentary in the diagnosis, prognostication of major cardiac events, and aid in the treatment algorithm in patients with cardiac sarcoidosis.

Can FDG-PET Imaging Identify Cardiac Sarcoidosis Disease Phenotypes?

PURPOSE OF REVIEW

Despite the scarcity of data, most guidelines have advocated for the treatment of cardiac sarcoidosis with corticosteroids. However, there is heterogeneity in disease presentation and response to treatment, which can make treatment challenging. The ability to identify disease phenotypes to allow for tailored therapy is therefore highly desirable. This review will seek to outline the disease phenotypes of cardiac sarcoidosis and the role that FDG-PET imaging can play in identifying these phenotypes to optimize disease diagnosis and treatment management.

RECENT FINDINGS

FDG PET can identify cardiac sarcoidosis and is being increasingly used to monitor therapeutic response to immunosuppressive therapy, to follow treatment response after discontinuation of corticosteroid therapy, and to evaluate for disease relapse. Modern quantitative techniques using FDG PET imaging may allow for even better phenotypic disease characterization and the ability to track the response to immunosuppression more accurately. FDG PET currently plays an important role in cardiac sarcoidosis diagnosis. However, it also affords us the opportunity to offer insights into cardiac sarcoidosis disease phenotypes to better understand the underlying disease process and in the future may allows us to tailor therapies accordingly.

The clinical value of quantitative cardiovascular molecular imaging: a step towards precision medicine

Cardiovascular diseases (CVD) are the leading cause of death worldwide and have an increasing impact on society. Precision medicine, in which optimal care is identified for an individual or a group of individuals rather than for the average population, might provide significant health benefits for this patient group and decrease CVD morbidity and mortality. Molecular imaging provides the opportunity to assess biological processes in individuals in addition to anatomical context provided by other imaging modalities and could prove to be essential in the implementation of precision medicine in CVD. New developments in single-photon emission computed tomography (SPECT) and positron emission tomography (PET) systems, combined with rapid innovations in promising and specific radiopharmaceuticals, provide an impressive improvement of diagnostic accuracy and therapy evaluation. This may result in improved health outcomes in CVD patients, thereby reducing societal impact. Furthermore, recent technical advances have led to new possibilities for accurate image quantification, dynamic imaging, and quantification of radiotracer kinetics. This potentially allows for better evaluation of disease activity over time and treatment response monitoring. However, the clinical implementation of these new methods has been slow. This review describes the recent advances in molecular imaging and the clinical value of quantitative PET and SPECT in various fields in cardiovascular molecular imaging, such as atherosclerosis, myocardial perfusion and ischemia, infiltrative cardiomyopathies, systemic vascular diseases, and infectious cardiovascular diseases. Moreover, the challenges that need to be overcome to achieve clinical translation are addressed, and future directions are provided.

Assessment of treatment response in cardiac sarcoidosis based on myocardial 18F-FDG uptake

Objective

Immunosuppressive therapy for cardiac sarcoidosis (CS) still largely consists of corticosteroid monotherapy. However, high relapse rates after tapering and insufficient efficacy are significant problems. The objective of this study was to investigate the efficacy and safety of non-biological and biological disease-modifying anti-rheumatic drugs (nb/bDMARDs) considering control of myocardial inflammation assessed by 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) of the heart.

Methods

We conducted a retrospective analysis of treatment response to nb/bDMARDs of all CS patients seen in the sarcoidosis center of the University Hospital Zurich between January 2016 and December 2020.

Results

We identified 50 patients with CS. Forty-five patients with at least one follow-up PET/CT scan were followed up for a mean of 20.5 ± 12.8 months. Most of the patients were treated with prednisone and concomitant nb/bDMARDs. At the first follow-up PET/CT scan after approximately 6.7 ± 3 months, only adalimumab showed a significant reduction in cardiac metabolic activity. Furthermore, comparing all serial follow-up PET/CT scans (143), tumor necrosis factor inhibitor (TNFi)-based therapies showed statistically significant better suppression of myocardial 18F-FDG uptake compared to other treatment regimens. On the last follow-up, most adalimumab-treated patients were inactive (n = 15, 48%) or remitting (n = 11, 35%), and only five patients (16%) were progressive. TNFi was safe even in patients with severely reduced left ventricular ejection fraction (LVEF), and a significant improvement in LVEF under TNFi treatment was observed.

Conclusion

TNFi shows better control of myocardial inflammation compared to nbDMARDs and corticosteroid monotherapies in patients with CS. TNFi was efficient and safe even in patients with severely reduced LVEF.

Hybrid PET/MR in Cardiac Imaging

In the last few years, technological advances in MR imaging, PET detectors, and attenuation correction algorithms have allowed the creation of truly integrated PET/MR imaging systems, for both clinical and research applications. These machines allow a comprehensive investigation of cardiovascular diseases, by offering a wide variety of detailed anatomical and functional data in combination. Despite significant pathophysiologic mechanisms being clarified by this new data, its clinical relevance and prognostic significance have not been demonstrated yet.

Diagnostic values of delayed additional FDG PET/CT scan in the evaluation of cardiac sarcoidosis

OBJECTIVE

This study aimed to compare the contribution of 18F-fluorodepxyglucose (FDG) positron (PET)/ computed tomography (CT) acquisition of early and delayed scans in patients with cardiac sarcoidosis (CS).

METHODS

Twenty-three patients with CS (median age: 69 years; 11 women) were retrospectively evaluated using dual-phase FDG PET/CT. All patients were instructed to consume a low-carbohydrate diet followed by fasting for 18 h before FDG injection to reduce physiological myocardial uptake. PET/CT was acquired at 60 min (early) and 100 min (delayed) after FDG administration. Focal and focal on diffuse uptake on visual analysis was considered positive for CS. A semi-quantitative analysis was performed using the maximum standardized uptake value (SUVmax) of the cardiac lesion and the mean SUV (SUVmean) of the blood pool.

RESULTS

Significant myocardial FDG uptake was observed in 21 patients (91.3%) in the early acquisition group and in 23 patients in the delayed scan group (100%). Compared to the early scan, the delayed scan showed a significantly higher SUVmax of the cardiac lesion [median, 4.0; IQR (interquartile range, 2.9 to 7.0) vs. 5.8 (IQR 3.7 to 10.1); P = 0.0030] and a significantly lower SUVmean of blood pool [median, 1.3 (IQR, 1.2 to 1.4) vs. 1.1 (IQR, 0.9 to 1.2); P < 0.0001].

CONCLUSION

Delayed FDG PET/CT acquisition improves detection accuracy in patients with CS compared to early scans with washout of the blood pool activity. Therefore, it can contribute to a more accurate assessment of CS.

Combined FDG PET/MRI versus Standard-of-Care Imaging in the Evaluation of Cardiac Sarcoidosis

PURPOSE

To compare combined cardiac fluorine 18 (18F) fluorodeoxyglucose (FDG) PET/MRI with standard-of-care evaluation using cardiac MRI, 18F-FDG PET/CT, and SPECT perfusion imaging in suspected cardiac sarcoidosis (CS) with respect to radiation dose, imaging duration, and diagnostic test performance.

MATERIALS AND METHODS

Consecutive patients with suspected CS undergoing clinical evaluation with cardiac 18F-FDG PET/CT and gated rest technetium 99m sestamibi SPECT perfusion imaging were prospectively recruited between November 2017 and May 2021 for parallel assessment with combined cardiac 18F-FDG PET/MRI on the same day (ClinicalTrials.gov identifier, NCT03356756). Total effective radiation dose and imaging duration were compared between approaches (combined cardiac PET/MRI vs separate cardiac MRI, PET/CT, and SPECT). MRI findings were initially interpreted without PET data, and then PET and late gadolinium enhancement images were fused and interpreted together. Final diagnosis of CS was established using Japanese Ministry of Health and Welfare guidelines.

RESULTS

Forty participants (mean age, 54 years ± 14 [SD]; 26 [65%] male participants) were included, 14 (35%) with a final diagnosis of CS. Compared with separate cardiac MRI, PET/CT, and SPECT perfusion imaging, combined cardiac PET/MRI had 52% lower total radiation dose (8.0 mSv ± 1.2 vs 16.8 mSv ± 1.6, P < .001) and 43% lower total imaging duration (122 minutes ± 15 vs 214 minutes ± 26, P < .001). Combined PET/MRI had the highest area under the curve for diagnosis of CS (0.84) with 96% specificity and 71% sensitivity for colocalized FDG uptake and late gadolinium enhancement in a pattern typical for CS.

CONCLUSION

In the evaluation of suspected CS, combined cardiac 18F-FDG PET/MRI had a lower radiation dose, shorter imaging duration, and higher diagnostic performance compared with standard-of-care imaging.Clinical trial registration no. NCT03356756Keywords: Cardiac Sarcoidosis, 18F-FDG PET/MRI, 18F-FDG PET/CT, SPECT Perfusion Imaging, Cardiac MRI, Standard-of-Care Imaging Supplemental material is available for this article. © RSNA, 2023.

[Positron emission tomography in cardiological practice]

The utility of positron emission tomography in cardiology currently goes beyond the ischemic heart disease and covers an increasingly wider range of non-coronary pathology, which requires timely expert diagnostics, including chronic heart disease of any etiology, valvular and electrophysiology disorders, cardiooncology. Authors emphasize the importance of the development of positron emission tomography technologies in the Russian Federation. This includes the development and implementation of new radiopharmaceuticals for the diagnosis of pathological processes of the cardiovascular system, systemic and local inflammation, including atherosclerosis, impaired perfusion and myocardial metabolism, and also for solving specific diagnostic tasks in comorbid pathology.

Prednisone vs methotrexate in treatment naïve cardiac sarcoidosis

BACKGROUND

Side effects limit the long-term use of glucocorticoids in cardiac sarcoidosis (CS), and methotrexate has gained attention as steroid sparing agent although the supporting evidence is poor. This study compared prednisone monotherapy, methotrexate monotherapy or a combination of both, in the reduction of myocardial Fluorine-18 fluorodeoxyglucose (FDG) uptake and clinical stabilization of CS patients.

METHODS AND RESULTS

In this retrospective cohort study, 61 newly diagnosed and treatment naïve CS patients commenced treatment with prednisone (N = 21), methotrexate (N = 30) or prednisone and methotrexate (N = 10) between January 2010 and December 2017. Primary outcome was metabolic response on FDG PET/CT and secondary outcomes were treatment patterns, major adverse cardiovascular events, left ventricular ejection fraction, biomarkers and side effects. At a median treatment duration of 6.2 [5.7-7.2] months, 71.4% of patients were FDG PET/CT responders, and the overall myocardial maximum standardized uptake value decreased from 6.9 [5.0-10.1] to 3.4 [2.1-4.7] (P < 0.001), with no significant differences between treatment groups. During 24 months of follow-up, 7 patients (33.3%; prednisone), 6 patients (20.0%; methotrexate) and 1 patient (10.0%; combination group) experienced at least one major adverse cardiovascular event (P = 0.292). Left ventricular ejection fraction was preserved in all treatment groups.

CONCLUSIONS

Significant suppression of cardiac FDG uptake occurred in CS patients after 6 months of prednisone, methotrexate or combination therapy. There were no significant differences in clinical outcomes during follow-up. These results warrant further investigation of methotrexate treatment in CS patients.

Semiquantitative evaluation of 68Ga-DOTANOC uptake in the normal myocardium: establishment of reference values

BACKGROUND

To ascertain presence of physiological uptake and derive standardized uptake values (SUV) of 68Ga-DOTANOC in normal myocardium and establish reference values.

METHODS AND RESULTS

Dedicated cardiac 68Ga-DOTANOC PET/CT studies of patients referred for evaluation of cardiac sarcoidosis (CS) or myocarditis and found to be normal on visual assessment and on cardiac MRI were analyzed semiquantitatively. The studies were acquired 45-60 minutes after intravenous injection of 111-185 MBq of 68Ga-DOTANOC. Myocardial SUVmax normalized to lean body mass (SUVmax_lbm) values for septum, anterior wall, proximal lateral wall, distal lateral wall, inferior wall, and apical region were 1.12 ± .39, 1.09 ± .42, 1.26 ± .49, 1.16 ± .40, 1.23 ± .39, and 1.05 ± .40, respectively. Myocardial SUVmax_lbm-to-blood pool SUVmean_lbm ratios were calculated for each region and 95th percentile values of these ratios were considered the upper limit of normal. 95th percentile values of myocardial SUVmax_lbm-to-blood pool SUVmean_lbm ratio for the corresponding regions were 1.70, 1.70, 2.00 1.95, 2.05, and 1.70, respectively.

CONCLUSION

There can be physiological uptake of 68Ga-DOTANOC in normal myocardium and the reference values of semiquantitative parameters established in this study may be employed as a corroborative tool for visual assessment in patients undergoing 68Ga-DOTANOC PET/CT for suspected CS or myocarditis.

Volume-based 18 F-FDG PET analysis of cardiac sarcoidosis using the descending aorta as a reference tissue

OBJECTIVE

18 F-FDG PET can be used to calculate the threshold value of myocardial volume based on the mean standardised uptake value (SUV mean ) of the aorta to detect highly integrated regions of cardiac sarcoidosis. The present study investigated the myocardial volume when the position and number of volumes of interest (VOIs) were changed in the aorta.

METHODS

The present study examined PET/computed tomography images of 47 consecutive cardiac sarcoidosis cases. VOIs were set at three locations in the myocardium and aorta (descending thoracic aorta, superior hepatic margin and near the pre-branch of the common iliac artery). The volume was calculated for each threshold using 1.1-1.5 times the SUV mean (median of three cross-sections) of the aorta as the threshold to detect high myocardial 18 F-FDG accumulation. The detected volume, correlation coefficient with the visually manually measured volume and the relative error were also calculated.

RESULTS

The optimum threshold value for detecting high 18 F-FDG accumulation was 1.4 times that of the single cross-section of the aorta and showed the smallest relative errors of 33.84% and 25.14% and correlation coefficients of 0.974 and 0.987 for single and three cross-sections, respectively.

CONCLUSION

The SUV mean of the descending aorta may be detected in good agreement with the visual high accumulation by multiplying the same threshold constant for both single and multiple cross-sections.

Linking cardiac and extracardiac sarcoidosis and their clinical outcome: 18F-FDG PET/CT analysis in patients with systemic cardiac sarcoidosis

OBJECTIVE

To clarify the link between cardiac sarcoidosis (CS) and extra-CS (ECS) in systemic CS (SCS) patients in terms of extent and clinical outcome by serial FDG-PET/CT.

METHODS

Thirty-five SCS patients treated for > 2 years were enrolled in this study. In the overall analysis, patient-based comparisons of the complete resolution (CR) and recurrence rate between CS and ECS lesions were performed. Then, subgroup analyses were performed according to the extent (mono- vs. multi-organ ECS group) and clinical outcome (stable vs. unstable ECS group) of ECS. Pre-treatment cardiac FDG uptake was compared between the mono- and multi-organ ECS groups. The rates of CR, recurrence, and major adverse cardiac events (MACE) were compared between the two groups.

RESULTS

The CR rate was significantly higher in CS than ECS lesions [77.1% (27/35) vs. 48.5% (17/35), p = 0.01], whereas recurrence rates were similar between CS and ECS [40.7% (11/27) vs. 58.8% (10/17)]. Both the mono- and multi-organ ECS groups showed similar SUV_max, cardiac metabolic volume, and cardiac metabolic activity in the pre-treatment condition. The CR rates were similar between the mono- and multi-organ ECS groups [71.4% (15/21) vs. 85.7% (12/14)], but the recurrence rate was significantly lower in the multi-organ ECS group [60.0% (9/15) vs. 16.7% (2/12), p = 0.02]. The CR [71.4% (5/7) vs. 78.6% (22/28)] and recurrence rates [60.0% (3/5) vs. 36.3% (8/22)] were not significantly different between the stable and unstable ECS groups. The occurrence of MACE was also not significantly different between the mono- and multi-organ ECS groups [19.0% (4/21) vs. 28.6% (4/14)] or between the stable and unstable ECS groups [42.9% (3/7) vs. 17.8% (5/28)].

CONCLUSIONS

CS lesions respond to treatment better than ECS lesions, and the extent and clinical outcome of ECS lesion are not linked with those of CS lesions.

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.

Myocardial Inflammation on FDG PET/MRI and Clinical Outcomes in Symptomatic and Asymptomatic Participants after COVID-19 Vaccination

Purpose

To evaluate potential cardiac sequelae of COVID-19 vaccination at 2-month follow-up and relate cardiac symptoms to myocardial tissue changes on fluorodeoxyglucose (FDG) PET/MRI, blood biomarkers, health-related quality of life, and adverse outcomes.

Materials and Methods

In this prospective study (ClinicalTrials.gov: NCT04967807), a convenience sample of individuals aged ≥17 years were enrolled after COVID-19 vaccination and were categorized as symptomatic myocarditis (new cardiac symptoms within 14 days of vaccination and met diagnostic criteria for acute myocarditis), symptomatic no myocarditis (new cardiac symptoms but did not meet criteria for myocarditis), and asymptomatic (no new cardiac symptoms). Standardized evaluation was performed 2 months after vaccination, including cardiac fluorine 18 FDG PET/MRI, blood biomarkers, and health-related quality of life. Statistical analysis included Kruskal-Wallis and Fisher exact tests.

Results

Fifty-four participants were evaluated a median of 72 days (IQR: 42, 91) after COVID-19 vaccination, 17 symptomatic with myocarditis (36±[SD]15 years, 13 males), 17 symptomatic without myocarditis (42±12 years, 7 males), and 20 asymptomatic (45±14 years, 9 males). No participants in the symptomatic without myocarditis or asymptomatic groups had focal FDG-uptake, myocardial edema or impaired ventricular function. Two participants with symptomatic myocarditis had focal FDG-uptake, and three had high T2 on MRI. Health-related quality of life was lower in the symptomatic myocarditis group than the asymptomatic group. There were no adverse cardiac events beyond myocarditis in any participant.

Conclusions

At two-month follow-up, FDG PET/MRI showed evidence of myocardial inflammation in 2/17 participants diagnosed with acute myocarditis early after COVID-19 vaccination, but not in symptomatic and asymptomatic participants without acute myocarditis.Keywords: Myocarditis, Vaccination, COVID-19, PET/MRI, Cardiac MRI, FDG-PET.

Prognostic Value of Cardiac MRI and FDG PET in Cardiac Sarcoidosis: A Systematic Review and Meta-Analysis

Background There is no consensus regarding the relative prognostic value of cardiac MRI and fluorodeoxyglucose (FDG) PET in cardiac sarcoidosis. Purpose To perform a systematic review and meta-analysis of the prognostic value of cardiac MRI and FDG PET for major adverse cardiac events (MACE) in cardiac sarcoidosis. Materials and Methods In this systematic review, MEDLINE, Ovid Epub, CENTRAL, Embase, Emcare, and Scopus were searched from inception until January 2022. Studies that evaluated the prognostic value of cardiac MRI or FDG PET in adults with cardiac sarcoidosis were included. The primary outcome of MACE was assessed as a composite including death, ventricular arrhythmia, and heart failure hospitalization. Summary metrics were obtained using random-effects meta-analysis. Meta-regression was used to assess covariates. Risk of bias was assessed using the Quality in Prognostic Studies, or QUIPS, tool. Results Thirty-seven studies were included (3489 patients with mean follow-up of 3.1 years ± 1.5 [SD]); 29 studies evaluated MRI (2931 patients) and 17 evaluated FDG PET (1243 patients). Five studies directly compared MRI and PET in the same patients (276 patients). Left ventricular late gadolinium enhancement (LGE) at MRI and FDG uptake at PET were both predictive of MACE (odds ratio [OR], 8.0 [95% CI: 4.3, 15.0] [P < .001] and 2.1 [95% CI: 1.4, 3.2] [P < .001], respectively). At meta-regression, results varied by modality (P = .006). LGE (OR, 10.4 [95% CI: 3.5, 30.5]; P < .001) was also predictive of MACE when restricted to studies with direct comparison, whereas FDG uptake (OR, 1.9 [95% CI: 0.82, 4.4]; P = .13) was not. Right ventricular LGE and FDG uptake were also associated with MACE (OR, 13.1 [95% CI: 5.2, 33] [P < .001] and 4.1 [95% CI: 1.9, 8.9] [P < .001], respectively). Thirty-two studies were at risk for bias. Conclusion Left and right ventricular late gadolinium enhancement at cardiac MRI and fluorodeoxyglucose uptake at PET were predictive of major adverse cardiac events in cardiac sarcoidosis. Limitations include few studies with direct comparison and risk of bias. Systematic review registration no. CRD42021214776 (PROSPERO) © RSNA, 2023 Supplemental material is available for this article.

Novel PET Applications and Radiotracers for Imaging Cardiovascular Pathophysiology

PET allows the assessment of cardiovascular pathophysiology across a wide range of cardiovascular conditions. By imaging processes directly involved in disease progression and adverse events, such as inflammation and developing calcifications (microcalcifications), PET can not only enhance our understanding of cardiovascular disease, but also, as shown for 18F-sodium fluoride, has the potential to predict hard endpoints. In this review, the recent advances in disease activity assessment with cardiovascular PET, which provide hope that this promising technology could be leveraged in the clinical setting, shall be discussed.

Clinical Utilization of Multimodality Imaging for Myocarditis and Cardiac Sarcoidosis

Myocarditis is defined as inflammation of the myocardium according to clinical, histological, biochemical, immunohistochemical, or imaging findings. Inflammation can be categorized histologically by cell type or pattern, and many causes have been implicated, including infectious, most commonly viral, systemic autoimmune diseases, vaccine-associated processes, environmental factors, toxins, and hypersensitivity to drugs. Sarcoid myocarditis is increasingly recognized as an important cause of cardiomyopathy and has important diagnostic, prognostic, and therapeutic implications in patients with systemic sarcoidosis. The clinical presentation of myocarditis may include an asymptomatic, subacute, acute, fulminant, or chronic course and may have focal or diffuse involvement of the myocardium depending on the cause and time point of the disease. For most causes of myocarditis except sarcoidosis, myocardial biopsy is the gold standard but is limited due to risk, cost, availability, and variable sensitivity. Diagnostic criteria have been established for both myocarditis and cardiac sarcoidosis and include clinical and imaging findings particularly the use of cardiac magnetic resonance and positron emission tomography. Beyond diagnosis, imaging findings may also provide prognostic value. This case-based review focuses on the current state of multimodality imaging for the diagnosis and management of myocarditis and cardiac sarcoidosis, highlighting multimodality imaging approaches with practical clinical vignettes, with a discussion of knowledge gaps and future directions.

Assessment of Cardiac Sarcoidosis: FDG PET and BMIPP SPECT

PURPOSE OF REVIEW

Cardiac sarcoidosis (CS) is an inflammatory disease of unknown etiology that can lead to life-threatening arrhythmias, heart failure, and death. Advanced cardiac imaging modalities have improved the clinician's ability to detect this disease. The purpose of this review is to discuss the recent evidence of cardiac metabolic imaging as assessed by [¹⁸F]FDG PET and [¹²³I]BMIPP SPECT in the evaluation of CS patients.

RECENT FINDINGS

[¹⁸F]FDG PET is the gold standard to identify myocardial inflammation. [¹²³I]BMIPP SPECT can uncover early myocardial damage as well as advanced stages of CS when fibrosis prevails. In presence of inflammation, myocardial [¹⁸F]FDG uptake is increased, but in contrast, BMIPP myocardial uptake is reduced or even suppressed. Thus, a complementary role of cardiac metabolic imaging by [¹⁸F]FDG PET and BMIPP SPECT has been proposed to detect the whole spectrum of CS. [¹⁸F]FDG PET is considered an important tool to improve the diagnosis and optimize the management of CS. The role of [¹²³I]BMIPP SPECT in diagnosing CS is still under investigation. Further studies are needed to evaluate the clinical utility of combined cardiac metabolic imaging in the diagnosis, prognosis, and for selecting treatments in CS patients.

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.

Quantitative technetium pyrophosphate and cardiovascular magnetic resonance in patients with suspected cardiac amyloidosis

BACKGROUND

Quantitation of myocardial 99m Tc-pyrophosphate activity may have high diagnostic accuracy, but its correlation with disease burden is unknown. We examined the relationship between 99m Tc-pyrophosphate quantitation and cardiac magnetic resonance (CMR) measures in patients with suspected transthyretin cardiac amyloidosis (ATTR-CM) or light chain cardiac amyloidosis (AL-CM).

METHODS

Consecutive patients who underwent 99mTc-pyrophosphate imaging and CMR were included. ATTR-CM and AL-CM were diagnosed using standard criteria. 99mTc-pyrophosphate images were assessed with standard parameters and quantified with cardiac pyrophosphate activity (CPA) and volume of involvement (VOI). We assessed the association between 99mTc-pyrophosphate image interpretation and CMR tissue characteristics.

RESULTS

Seventy patients were identified, mean age 70.4 ± 11.4 years, with ATTR-CM and AL-CM diagnosed in 22 (31%) and 11 (16%) patients, respectively. In patients with ATTR-CM, there were significant correlations between CPA (r2 = 0.509, P < 0.001) and VOI (r2 = 0.586, P < 0.001) with native myocardial T1 mapping values. Additionally, CPA (adjusted hazard ratio (aHR) 1.04, P = 0.016), VOI (aHR 1.12, P = 0.034), and average myocardial T1 (aHR 1.12, P = 0.025) were associated with incidence of heart failure hospitalization or death.

CONCLUSION

CPA and VOI were correlated with CMR measures of myocardial fibrosis in patients with ATTR-CM. 99mTc-pyrophosphate quantitation may have a role in ATTR-CM disease staging, guiding treatment, or following response to therapy.

Incidence and Predictors of Atrial Fibrillation in Cardiac Sarcoidosis: A Multimodality Imaging Study

BACKGROUND

In cardiac sarcoidosis (CS), the risk and predictors of new-onset atrial fibrillation (AF) are poorly known.

OBJECTIVES

The authors evaluated the incidence and characteristics of AF in newly diagnosed CS.

METHODS

The authors studied 118 patients (78 women, mean age 50 years) with AF-naive CS having undergone cardiac ¹⁸F-fluorodexoyglucose positron emission tomography (¹⁸F-FDG PET) at the time of diagnosis. Details of patient characteristics and medical or device therapy were collected from hospital charts. The PET scans were re-analyzed for presence of atrial and ventricular inflammation, and coincident cardiac magnetic resonance (CMR) studies and single-photon emission computed tomography (SPECT) perfusions were analyzed for cardiac structure and function, including the presence and extent of myocardial scarring. Detection of AF was based on interrogation of intracardiac devices and on ambulatory or 12-lead electrocardiograms.

RESULTS

Altogether 34 patients (29%) suffered paroxysms of AF during follow-up (median, 3 years) with persistent AF developing in 7 patients and permanent AF in 4. The estimated 5-year incidence of AF was 55% (95% CI: 34%-72%) in the 39 patients with atrial ¹⁸F-FDG uptake at the time of diagnosis vs 18% (95% CI: 10%-28%) in the 79 patients without atrial uptake (P < 0.001). In cause-specific Cox regression analysis, atrial uptake was an independent predictor of AF (P < 0.001) with HR of 6.01 (95% CI: 2.64-13.66). Other independent predictors were an increased left atrial maximum volume (P < 0.01) and history of sleep apnea (P < 0.01). Ventricular involvement by PET, SPECT, or CMR was nonpredictive. Symptoms of AF prompted electrical cardioversion in 12 patients (35%). Three of the 34 patients (9%) experiencing AF suffered a stroke versus none of those remaining free of AF.

CONCLUSIONS

In newly diagnosed CS, future AF is relatively common and associated with atrial inflammation and enlargement on multimodality cardiac imaging.

What cardiologists should know about cardiac sarcoidosis in 2022?

PURPOSE OF REVIEW

Cardiac sarcoidosis (CS) is a potentially fatal condition when unrecognized or not treated adequately. The purpose of this review is to provide new strategies to increase clinical recognition of CS and to present an updated overview of the immunosuppressive treatments using most recent data published in the last 18 months.

RECENT FINDINGS

CS is an increasingly recognized pathology, and its diagnostic is made 20 times more often in the last two decades. Recent studies have shown that imaging alone usually lacks specificity to distinguish CS from other inflammatory cardiomyopathies. However, imaging can be used to increase significantly diagnostic yield of extracardiac and cardiac biopsy. Recent reviews have also demonstrated that nearly 25% of patients will be refractory to standard treatment with prednisone and that combined treatment with a corticosteroid-sparing agent is often necessary for a period that remains undetermined.

SUMMARY

CS is a complex pathology that should always require a biopsy attempt to have a histological proven diagnosis before starting immunosuppressive therapy consisting of corticosteroids with or without a corticosteroid-sparing agent.

Inhibition of type 1 immunity with tofacitinib is associated with marked improvement in longstanding sarcoidosis

Sarcoidosis is an idiopathic inflammatory disorder that is commonly treated with glucocorticoids. An imprecise understanding of the immunologic changes underlying sarcoidosis has limited therapeutic progress. Here in this open-label trial (NCT03910543), 10 patients with cutaneous sarcoidosis are treated with tofacitinib, a Janus kinase inhibitor. The primary outcome is the change in the cutaneous sarcoidosis activity and morphology instrument (CSAMI) activity score after 6 months of treatment. Secondary outcomes included change in internal organ involvement, molecular parameters, and safety. All patients experience improvement in their skin with 6 patients showing a complete response. Improvement in internal organ involvement is also observed. CD4⁺ T cell-derived IFN-γ is identified as a central cytokine mediator of macrophage activation in sarcoidosis. Additional type 1 cytokines produced by distinct cell types, including IL-6, IL-12, IL-15 and GM-CSF, also associate with pathogenesis. Suppression of the activity of these cytokines, especially IFN-γ, correlates with clinical improvement. Our results thus show that tofacitinib treatment is associated with improved sarcoidosis symptoms, and predominantly acts by inhibiting type 1 immunity.

Diagnostic Accuracy of Cardiac MRI versus FDG PET for Cardiac Sarcoidosis: A Systematic Review and Meta-Analysis

Background There is limited consensus regarding the relative diagnostic performance of cardiac MRI and fluorodeoxyglucose (FDG) PET for cardiac sarcoidosis. Purpose To perform a systematic review and meta-analysis to compare the diagnostic accuracy of cardiac MRI and FDG PET for cardiac sarcoidosis. Materials and Methods Medline, Ovid Epub, Cochrane Central Register of Controlled Trials, Embase, Emcare, and Scopus were searched from inception until January 2022. Inclusion criteria included studies that evaluated the diagnostic accuracy of cardiac MRI or FDG PET for cardiac sarcoidosis in adults. Data were independently extracted by two investigators. Summary accuracy metrics were obtained by using bivariate random-effects meta-analysis. Meta-regression was used to assess the effect of different covariates. Risk of bias was assessed using the Quality Assessment Tool for Diagnostic Accuracy Studies-2 tool. The study protocol was registered a priori in the International Prospective Register of Systematic Reviews (Prospero protocol CRD42021214776). Results Thirty-three studies were included (1997 patients, 687 with cardiac sarcoidosis); 17 studies evaluated cardiac MRI (1031 patients) and 26 evaluated FDG PET (1363 patients). Six studies directly compared cardiac MRI and PET in the same patients (303 patients). Cardiac MRI had higher sensitivity than FDG PET (95% vs 84%; P = .002), with no difference in specificity (85% vs 82%; P = .85). In a sensitivity analysis restricted to studies with direct comparison, point estimates were similar to those from the overall analysis: cardiac MRI and FDG PET had sensitivities of 92% and 81% and specificities of 72% and 82%, respectively. Covariate analysis demonstrated that sensitivity for FDG PET was highest with quantitative versus qualitative evaluation (93% vs 76%; P = .01), whereas sensitivity for MRI was highest with inclusion of T2 imaging (99% vs 88%; P = .001). Thirty studies were at risk of bias. Conclusion Cardiac MRI had higher sensitivity than fluorodeoxyglucose PET for diagnosis of cardiac sarcoidosis but similar specificity. Limitations, including risk of bias and few studies with direct comparison, necessitate additional study. © RSNA, 2022 Online supplemental material is available for this article.

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.

Combined Cardiac Fluorodeoxyglucose-Positron Emission Tomography/Magnetic Resonance Imaging Assessment of Myocardial Injury in Patients Who Recently Recovered From COVID-19

IMPORTANCE

Although myocardial injury can occur with acute COVID-19, there is limited understanding of changes with myocardial metabolism in recovered patients.

OBJECTIVE

To examine myocardial metabolic changes early after recovery from COVID-19 using fluorodeoxyglucose-positron emission tomography (PET) and associate these changes to abnormalities in cardiac magnetic resonance imaging (MRI)-based function and tissue characterization measures and inflammatory blood markers.

DESIGN, SETTING, AND PARTICIPANTS

This prospective cohort study took place at a single-center tertiary referral hospital system. A volunteer sample of adult patients within 3 months of a diagnosis of COVID-19 who responded to a mail invitation were recruited for cardiac PET/MRI and blood biomarker evaluation between November 2020 and June 2021.

EXPOSURES

Myocardial inflammation as determined by focal fluorodeoxyglucose (FDG) uptake on PET.

MAIN OUTCOMES AND MEASURES

Demographic characteristics, cardiac and inflammatory blood markers, and fasting combined cardiac 18F-FDG PET/MRI imaging were obtained. All patients with focal FDG uptake at baseline returned for repeated PET/MRI and blood marker assessment 2 months later.

RESULTS

Of 47 included patients, 24 (51%) were female, and the mean (SD) age was 43 (13) years. The mean (SD) interval between COVID-19 diagnosis and PET/MRI was 67 (16) days. Most patients recovered at home during the acute infection (40 [85%]). Eight patients (17%) had focal FDG uptake on PET consistent with myocardial inflammation. Compared with those without FDG uptake, patients with focal FDG uptake had higher regional T2, T1, and extracellular volume (colocalizing with focal FDG uptake), higher prevalence of late gadolinium enhancement (6 of 8 [75%] vs 9 of 39 [23%], P = .009), lower left ventricular ejection fraction (mean [SD], 55% [4%] vs 62% [5%], P < .001), worse global longitudinal and circumferential strain (mean [SD], -16% [2%] vs -17% [2%], P = .02 and -18% [2%] vs -20% [2%], P = .047, respectively), and higher systemic inflammatory blood markers including interleukin 6, interleukin 8, and high-sensitivity C-reactive protein. Among patients with focal FDG uptake, PET/MRI, and inflammatory blood markers resolved or improved at follow-up performed a mean (SD) of 52 (17) days after baseline PET/MRI.

CONCLUSIONS AND RELEVANCE

In this study of patients recently recovered from COVID-19, myocardial inflammation was identified on PET in a small proportion of patients, was associated with cardiac MRI abnormalities and elevated inflammatory blood markers at baseline, and improved at follow-up.

Current State and Future Directions of Multimodality Imaging in Cardiac Sarcoidosis

Cardiac sarcoidosis (CS) is an increasingly recognized cause of heart failure and arrhythmia. Historically challenging to identify, particularly in the absence of extracardiac sarcoidosis, diagnosis of CS has improved with advancements in cardiac imaging. Recognition as well as management may require interpretation of multiple imaging modalities. Echocardiography may serve as an initial screening study for cardiac involvement in patients with systemic sarcoidosis. Cardiac magnetic resonance imaging (CMR) provides information on diagnosis as well as risk stratification, particularly for ventricular arrhythmia in the setting of late gadolinium enhancement. More recently, ¹⁸F-fluorodeoxyglucose position emission tomography (FDG-PET) has assumed a valuable role in the diagnosis and longitudinal management of patients with CS, allowing for the assessment of response to treatment. Hybrid FDG-PET/CT may also be used in the evaluation of extracardiac inflammation, permitting the identification of biopsy sites for diagnostic confirmation. Herein we examine the approach to diagnosis and management of CS using multimodality imaging via a case-based review.

Quantitative Assessment of Cardiac Hypermetabolism and Perfusion for Diagnosis of Cardiac Sarcoidosis

BACKGROUND

Quantitative assessment of cardiac hypermetabolism from 18Flourodeoxy glucose (FDG) positron emission tomography (PET) may improve diagnosis of cardiac sarcoidosis (CS). We assessed different approaches for quantification of cardiac hypermetabolism and perfusion in patients with suspected CS.

METHODS AND RESULTS

Consecutive patients undergoing 18FDG PET assessment for possible CS between January 2014 and March 2019 were included. Cardiac hypermetabolism was quantified using maximal standardized uptake value (SUVMAX), cardiometabolic activity (CMA) and volume of inflammation, using relative thresholds (1.3× and 1.5× left ventricular blood pool [LVBP] activity), and absolute thresholds (SUVMAX > 2.7 and 4.1). Diagnosis of CS was established using the Japanese Ministry of Health and Wellness criteria. In total, 69 patients were studied, with definite or possible CS in 29(42.0%) patients. CMA above 1.5× LVBP SUVMAX had the highest area under the receiver operating characteristic curve (AUC 0.92). Quantitative parameters using relative thresholds had higher AUC compared to absolute thresholds (p < 0.01). Interobserver variability was low for CMA, with excellent agreement regarding absence of activity (Kappa 0.970).

CONCLUSIONS

Quantitation with scan-specific thresholds has superior diagnostic accuracy compared to absolute thresholds. Based on the potential clinical benefit, programs should consider quantification of cardiac hypermetabolism when interpreting 18F-FDG PET studies for CS.

Observer repeatability and interscan reproducibility of 18F-sodium fluoride coronary microcalcification activity

BACKGROUND

We aimed to establish the observer repeatability and interscan reproducibility of coronary 18F-sodium-fluoride positron emission tomography (PET) uptake using a novel semi-automated approach, coronary microcalcification activity (CMA).

METHODS

Patients with multivessel coronary artery disease underwent repeated hybrid PET and computed tomography angiography (CTA) imaging (PET/CTA). CMA was defined as the integrated standardized uptake values (SUV) in the entire coronary tree exceeding 2 standard deviations above the background SUV. Coefficients of repeatability between the same observer (intraobserver repeatability), between 2 observers (interobserver repeatability) and coefficient of reproducibility between 2 scans (interscan reproducibility), were determined at vessel and patient level.

RESULTS

In 19 patients, CMA was assessed twice in 43 coronary vessels on two PET/CT scans performed 12 ± 5 days apart. There was excellent intraclass correlation for intraobserver and interobserver repeatability as well as interscan reproducibility (all ≥ 0.991). There was 100% intraobserver, interobserver and interscan agreement for the presence (CMA > 0) or absence (CMA = 0) of coronary18F-NaF uptake. Mean CMA was 3.12 ± 0.62 with coefficients of repeatability of ≤ 10% for all measures: intraobserver 0.24 and 0.22, interobserver 0.30 and 0.29 and interscan 0.33 and 0.32 at a per-vessel and per-patient level, respectively.

CONCLUSIONS

CMA is a repeatable and reproducible global measure of coronary atherosclerotic activity.

Combined simultaneous FDG-PET/MRI with T1 and T2 mapping as an imaging biomarker for the diagnosis and prognosis of suspected cardiac sarcoidosis

PURPOSE

To evaluate the diagnostic and prognostic significance of combined cardiac 18F-fluorodeoxyglucose (FDG) PET/MRI with T1/T2 mapping in the evaluation of suspected cardiac sarcoidosis.

METHODS

Patients with suspected cardiac sarcoidosis were prospectively enrolled for cardiac 18F-FDG PET/MRI, including late gadolinium enhancement (LGE) and T1/T2 mapping with calculation of extracellular volume (ECV). The final diagnosis of cardiac sarcoidosis was established using modified JMHW guidelines. Major adverse cardiac events (MACE) were assessed as a composite of cardiovascular death, ventricular tachyarrhythmia, bradyarrhythmia, cardiac transplantation or heart failure. Statistical analysis included Cox proportional hazard models.

RESULTS

Forty-two patients (53 ± 13 years, 67% male) were evaluated, 13 (31%) with a final diagnosis of cardiac sarcoidosis. Among patients with cardiac sarcoidosis, 100% of patients had at least one abnormality on PET/MRI: FDG uptake in 69%, LGE in 100%, elevated T1 and ECV in 100%, and elevated T2 in 46%. FDG uptake co-localized with LGE in 69% of patients with cardiac sarcoidosis compared to 24% of those without, p = 0.014. Diagnostic specificity for cardiac sarcoidosis was highest for FDG uptake (69%), elevated T2 (79%), and FDG uptake co-localizing with LGE (76%). Diagnostic sensitivity was highest for LGE, elevated T1 and ECV (100%). After median follow-up duration of 634 days, 13 patients experienced MACE. All patients who experienced MACE had LGE, elevated T1 and elevated ECV. FDG uptake (HR 14.7, p = 0.002), elevated T2 (HR 9.0, p = 0.002) and native T1 (HR 1.1 per 10 ms increase, p = 0.044) were significant predictors of MACE even after adjusting for left ventricular ejection fraction and immune suppression treatment. The presence of FDG uptake co-localizing with LGE had the highest diagnostic performance overall (AUC 0.73) and was the best predictor of MACE based on model goodness of fit (HR 14.9, p = 0.001).

CONCLUSIONS

Combined cardiac FDG-PET/MRI with T1/T2 mapping provides complementary diagnostic information and predicts MACE in patients with suspected cardiac sarcoidosis.

Advances in Diagnostic Imaging for Cardiac Sarcoidosis

Sarcoidosis is a systemic granulomatous disease of unknown etiology, and its clinical presentation depends on the affected organ. Cardiac sarcoidosis (CS) is one of the leading causes of death among patients with sarcoidosis. The clinical manifestations of CS are heterogeneous, and range from asymptomatic to life-threatening arrhythmias and progressive heart failure due to the extent and location of granulomatous inflammation in the myocardium. Advances in imaging techniques have played a pivotal role in the evaluation of CS because histological diagnoses obtained by myocardial biopsy tend to have lower sensitivity. The diagnosis of CS is challenging, and several approaches, notably those using positron emission tomography and cardiac magnetic resonance imaging (MRI), have been reported. Delayed-enhanced computed tomography (CT) may also be used for diagnosing CS in patients with MRI-incompatible devices and allows acceptable evaluation of myocardial hyperenhancement in such patients. This article reviews the advances in imaging techniques for the evaluation of CS.

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.

Diagnostic and prognostic value of Technetium-99m pyrophosphate uptake quantitation for transthyretin cardiac amyloidosis

BACKGROUND

99mTc-pyrophosphate imaging has emerged as an important non-invasive method to diagnose transthyretin cardiac amyloidosis (ATTR-CM). Quantitation of 99mTc-pyrophosphate activity, on SPECT images, could be a marker of ATTR-CM disease burden. We assessed the diagnostic accuracy and clinical significance of 99mTc-pyrophosphate quantitation.

METHODS AND RESULTS

Patients who underwent 99mTc-pyrophosphate imaging for suspected ATTR-CM were included. Using SPECT images, radiotracer activity in the myocardium was calculated using cardiac pyrophosphate activity (CPA) and volume of involvement (VOI), with thresholds for abnormal activity derived from LVBP activity. Diagnostic accuracy was assessed using area under the receiver operating characteristic curve (AUC). In total, 124 patients were identified, mean age 73.9 ± 11.4, with ATTR-CM diagnosed in 43 (34.7%) patients. CPA had the highest diagnostic accuracy (AUC .996, 95% CI .987-1.00), and was significantly higher compared to the Perugini score (AUC .952, P = .016). In patients with ATTR-CM, CPA was associated with reduced left ventricular ejection fraction (adjusted odds ratio 1.28, P = .035) and heart failure hospitalizations (adjusted hazard ratio 1.29, P = .006).

CONCLUSION

Quantitative assessment of myocardial radiotracer activity with CPA or VOI have high diagnostic accuracy for ATTR-CM. Both measures are potential non-invasive markers to follow progression of disease or response to therapy.

Cytokine Signaling and Matrix Remodeling Pathways Associated with Cardiac Sarcoidosis Disease Activity Defined Using FDG PET Imaging

While cardiac imaging has improved the diagnosis and risk assessment for cardiac sarcoidosis (CS), treatment regimens have consisted of generalized heart failure therapies and non-specific anti-inflammatory regimens. The overall goal of this study was to perform high-sensitivity plasma profiling of specific inflammatory pathways in patients with sarcoidosis and with CS.Specific inflammatory/proteolytic cascades were upregulated in sarcoidosis patients, and certain profiles emerged for CS patients.Plasma samples were collected from patients with biopsy-confirmed sarcoidosis undergoing F-18 fluorodeoxyglucose positron emission tomography (n = 47) and compared to those of referent control subjects (n = 6). Using a high-sensitivity, automated multiplex array, cytokines, soluble cytokine receptor profiles (an index of cytokine activation), as well as matrix metalloproteinase (MMP), and endogenous MMP inhibitors (TIMPs) were examined.The plasma tumor necrosis factor (TNF) and soluble TNF receptors sCD30 and sTNFRI were increased using sarcoidosis, and sTNFRII increased in CS patients (n = 18). The soluble interleukin sIL-2R and vascular endothelial growth factor receptors (sVEGFR2 and sVEGFR3) increased to the greatest degree in CS patients. When computed as a function of referent control values, the majority of soluble cytokine receptors increased in both sarcoidosis and CS groups. Plasma MMP-9 levels increased in sarcoidosis but not in the CS subset. Plasma TIMP levels declined in both groups.The findings from this study were the identification of increased activation of a cluster of soluble cytokine receptors, which augment not only inflammatory cell maturation but also transmigration in patients with sarcoidosis and patients with cardiac involvement.

Association of high serum soluble interleukin 2 receptor levels with risk of adverse events in cardiac sarcoidosis

Aims

Although soluble interleukin 2 receptor (sIL‐2R) is a potentially useful biomarker in the diagnosis and evaluation of disease severity in patients with sarcoidosis, its prognostic implication in patients with cardiac sarcoidosis (CS) is unclear. We sought to investigate whether sIL‐2R was associated with clinical outcomes and to clarify the relationship between sIL‐2R levels and disease activity in patients with CS.

Methods and results

We examined 83 consecutive patients with CS in our hospital who had available serum sIL‐2R data between May 2003 and February 2020. The primary outcome was a composite of advanced atrioventricular block, ventricular tachycardia or ventricular fibrillation, heart failure hospitalization, and all‐cause death. Inflammatory activity in the myocardium and lymph nodes was assessed by ¹⁸F‐fluorideoxyglucose positron emission tomography/computed tomography. During a median follow‐up period of 2.96 (IQR 2.24–4.27) years, the primary outcome occurred in 24 patients (29%). Higher serum sIL‐2R levels (>538 U/mL, the median) were significantly related to increased incidence of primary outcome (P = 0.037). Multivariable Cox regression analysis showed that a higher sIL‐2R was independently associated with an increased subsequent risk of adverse events (HR 3.71, 95% CI 1.63–8.44, P = 0.002), even after adjustment for significant covariates. sIL‐2R levels were significantly correlated to inflammatory activity in lymph nodes (r = 0.346, P = 0.003) but not the myocardium (r = 0.131, P = 0.27).

Conclusions

Increased sIL‐2R is associated with worse long‐term clinical outcomes accompanied by increased systemic inflammatory activity in CS patients.

Comparison of 68Ga-DOTANOC PET/CT with cardiac MRI in patients with clinical suspicion of cardiac sarcoidosis

BACKGROUND

68Ga-DOTA-NaI-octreotide (DOTANOC) is a promising new alternative to 18F-fluorodeoxyglucose (FDG) for imaging inflammation in cardiac sarcoidosis. The aim of the study was to compare 68Ga-DOTANOC positron emission tomography/computed tomography (PET/CT) with cardiac magnetic resonance imaging (CMR) in patients with clinical suspicion of cardiac sarcoidosis.

METHODS AND RESULTS

Patients with extracardiac sarcoidosis and clinical suspicion of cardiac involvement underwent 68Ga-DOTANOC cardiac PET/CT, myocardial perfusion single photon emission computed tomography (MPS) and CMR (T2-weighted and delayed gadolinium-enhanced T1-weighted images). The patients were screened using revised criteria of Japanese circulation society. Presence of perfusion defects on MPS, abnormal myocardial uptake on 68Ga-DOTANOC PET/CT and characteristic pattern of late gadolinium enhancement (LGE) with or without T2 hyperintensity on CMR was considered positive.

RESULTS

Seventeen patients (13 male and 4 female) were included in the study. Out of the 17 patients, both CMR and PET were positive in 11 and both were negative in 2. In the remaining 4 patients, CMR was positive but PET was normal. Thus, PET and CMR were concordant in 13 (76.5%) patients and discordant in 4 (23.5%). Intermodality agreement was fair (Cohen's kappa = 0.39).

CONCLUSION

LGE on CMR is superior to 68Ga-DOTANOC PET/CT for detecting cardiac involvement in sarcoidosis and there is fair concordance between the two. However, since LGE does not specifically differentiate between inflammation and fibrosis, 68Ga-DOTANOC PET/CT may be better than CMR in identifying patients with active inflammation, since it directly targets inflammatory cells and can have a complementary role to CMR.

The rate of myocardial perfusion recovery after steroid therapy and its implication for cardiac events in cardiac sarcoidosis and primarily preserved left ventricular ejection fraction

BACKGROUND

Sarcoidosis is a multisystemic disorder of unknown cause characterized by immune granuloma formation in the involved organs. Few studies have reported on the myocardial perfusion changes by immunosuppression therapy in cardiac sarcoidosis (CS). Additionally, the relationship between myocardial perfusion changes and prognosis is unknown. Therefore, this study aimed to clarify myocardial perfusion recovery after steroid therapy and its prognostic value for major adverse cardiac events (MACE) in patients with CS.

METHODS AND RESULTS

Thirty-eight consecutive patients with CS {median age, 63 [interquartile range (IQR) 51-68] years; 10 men} underwent both 18F-fluorodeoxyglucose positron emission tomography/computed tomography (CT) and electrocardiography-gated single-photon emission CT (SPECT) pre- and post-steroid therapy. Patients with improved or preserved myocardial perfusion after post-therapy were defined as the recovery group and those with worsened myocardial perfusion as the non-recovery group. Twenty-six patients (68%) were categorized as the recovery group. MACE occurred in eight patients. The Kaplan-Meier curves revealed a significantly higher rate of MACE in the non-recovery group (17.4%/y vs 2.9%/y, P = 0.007).

CONCLUSIONS

Myocardial perfusion was recovered by steroid therapy in 61% and preserved in 8% of patients. Myocardial perfusion recovery after steroid therapy was significantly associated with a low incidence of MACE.