Early Detection of Multiorgan Light-Chain Amyloidosis by Whole-Body 18F-Florbetapir PET/CT

Extensive Pulmonary AL Amyloidosis Mimicking Miliary Tuberculosis: The Diagnostic Utility of 99mTc-PYP Scintigraphy

ABSTRACT

Amyloidosis is a misfolded protein deposition disorder within the extracellular matrix, leading to dysfunction in the affected organ. Primary amyloidosis manifests as AL and ATTR subtypes, wherein AL is associated with plasma cell dyscrasias. Herein we present a case of a patient who underwent investigation due to the presence of bilateral reticulonodular lung infiltrates, suggestive of miliary tuberculosis. 99mTc-PYP scan revealed widespread radiotracer uptake in the lungs leading to diagnosis of AL amyloidosis.

Molecular Imaging of Heart Failure: An Update and Future Trends

Molecular imaging can detect and quantify pathophysiological processes underlying heart failure, complementing evaluation of cardiac structure and function with other imaging modalities. Targeted tracers have enabled assessment of various cellular and subcellular mechanisms of heart failure aiming for improved phenotyping, risk stratification, and personalized therapy. This review outlines the current status of molecular imaging in heart failure, accompanied with discussion on novel developments. The focus is on radionuclide methods with data from clinical studies. Imaging of myocardial metabolism can identify left ventricle dysfunction caused by myocardial ischemia that may be reversible after revascularization in the presence of viable myocardium. In vivo imaging of active inflammation and amyloid deposition have an established role in the detection of cardiac sarcoidosis and transthyretin amyloidosis. Innervation imaging has well documented prognostic value in predicting heart failure progression and arrhythmias. Tracers specific for inflammation, angiogenesis and myocardial fibrotic activity are in earlier stages of development, but have demonstrated potential value in early characterization of the response to myocardial injury and prediction of cardiac function over time. Early detection of disease activity is a key for transition from medical treatment of clinically overt heart failure towards a personalized approach aimed at supporting repair and preventing progressive cardiac dysfunction.

Radionuclide Imaging of Cardiac Amyloidosis: An Update and Future Aspects

Cardiac amyloidosis (CA) is caused by the misfolding, accumulation and aggregation of proteins into large fibrils in the extracellular compartment of the myocardium, leading to restrictive cardiomyopathy, heart failure and death. The major forms are transthyretin (ATTR) CA and light-chain (AL) CA, based on the respective precursor protein. Each of them requires early diagnosis for a timely treatment initiation that will improve patient outcomes. For this, radionuclide imaging is essentially used as single-photon emission computed tomography (SPECT) with bone-avid radiotracers or as positron emission tomography (PET) with amyloid-binding radiotracers. Both offer unprecedented specificity for the diagnostic of CA. SPECT has even revolutionized the diagnosis of ATTR-CA by making it non-invasive. Indeed, SPECT has now entered the standard diagnostic pathway to CA and has led to earlier diagnosis of the disease. SPECT also modified the epidemiology of ATTR-CA, highlighting that the disease is much more frequent than previously believed, and showing that ATTR-CA plays a substantial role in HFpEF and aortic stenosis, particularly among elderly patients. In parallel, amyloid-binding radiotracers for PET have accumulated a substantial amount of evidence, but are not approved for clinical use in CA yet. Further studies are needed to refine acquisition protocols and validate results in broader populations. Unlike bone-avid SPECT radiotracers, PET radiotracers have been specifically created to bind to amyloid fibrils. Thus, PET is the only imaging method that is truly specific for amyloid deposits and very sensitive to any amyloid type. Indeed, PET can not only detect ATTR-CA, but also AL-CA and rare hereditary forms. For both SPECT and PET, advances in quantitation of myocardial uptake have generated more granular and reproducible findings, paving the way for progress in earlier diagnosis, risk stratification and therapeutic response monitoring. Encouraging findings have shown that SPECT and PET are sensitive to early CA when other diagnostic methods are negative. Both radionuclide imaging techniques can predict adverse outcomes, but more evidence is needed to determine how to use them in conjunction with usual prognostic staging scores. Studies on follow-up imaging after therapy suggested that SPECT and PET can capture myocardial changes in CA, but again, more data are needed to meaningfully interpret such changes. Based on all these promising results, radionuclide imaging has the potential to further impact the landscape of CA in diagnosis, prognosis and follow-up, but also to substantially contribute to the assessment of novel therapies that will improve the lives of patients with CA.

Prognostic Value of Left Ventricular 18F-Florbetapir Uptake in Systemic Light-Chain Amyloidosis

BACKGROUND

Positron emission tomography/computed tomography (PET/CT) with 18F-florbetapir, a novel amyloid-targeting radiotracer, can quantify left ventricular (LV) amyloid burden in systemic light-chain (AL) amyloidosis. However, its prognostic value is not known.

OBJECTIVES

The authors' aim was to evaluate the prognostic value of LV amyloid burden quantified by 18F-florbetapir PET/CT, and to identify mechanistic pathways mediating its association with outcomes.

METHODS

A total of 81 participants with newly diagnosed AL amyloidosis underwent 18F-florbetapir PET/CT imaging. Amyloid burden was quantified using 18F-florbetapir LV uptake as percent injected dose. The Mayo stage for AL amyloidosis was determined using troponin T, N-terminal pro-B-type natriuretic peptide (NT-proBNP), and free light chain levels. Major adverse cardiac events (MACE) were defined as all-cause death, heart failure hospitalization, or cardiac transplantation within 12 months.

RESULTS

Among participants (median age, 61 years; 57% males), 36% experienced MACE, increasing from 7% to 63% across tertiles of LV amyloid burden (P < 0.001). LV amyloid burden was associated with MACE (HR: 1.46; 95% CI: 1.16-1.83; P = 0.001). However, this association became nonsignificant when adjusted for Mayo stage. In mediation analysis, the association between LV amyloid burden and MACE was mediated by NT-proBNP (P < 0.001), a marker of cardiomyocyte stretch and heart failure, and a component of Mayo stage.

CONCLUSIONS

In this first study to link cardiac 18F-florbetapir uptake to subsequent outcomes, LV amyloid burden estimated by percent injected dose predicted MACE in AL amyloidosis. This effect was not independent of Mayo stage and was mediated primarily through NT-proBNP. These findings provide novel insights into the mechanism linking myocardial amyloid deposits to MACE.

Early diagnosis and management of cardiac amyloidosis: A clinical perspective

Cardiac amyloidosis multidisciplinary team (MDT). We propose the creation of a multidisciplinary team (MDT) for cardiac amyloidosis in which internal medicine physicians could take a lead role in coordinating other specialists involved in patient care. Created with BioRender.com.

18 F-Florbetapir PET/CT and 68 Ga-FAPI PET/CT in a Case of Light Chain Amyloidosis With Predominant Multiple Tumor-Like Deposits

ABSTRACT

A 66-year-old man presented with multiple masses in different regions, including the left groin, back subcutaneous area, and lungs. Pathological examination confirmed localized amyloid deposits after 3 surgeries. Serum-free λ light chains were elevated. To evaluate systemic involvement, the patient underwent 18 F-Florbetapir PET/CT and 68 Ga-FAPI-04 PET/CT. Both scans showed increased uptake in multiple masses and nodules throughout the body. This report presents a rare case of light chain (AL) amyloidosis, primarily characterized by multiple localized tumor-like deposits with high activity on 18 F-Florbetapir PET/CT and 68 Ga-FAPI-04 PET/CT.

Quantification of right ventricular amyloid burden with 18F-florbetapir positron emission tomography/computed tomography and its association with right ventricular dysfunction and outcomes in light-chain amyloidosis

AIMS

In systemic light-chain (AL) amyloidosis, quantification of right ventricular (RV) amyloid burden has been limited and the pathogenesis of RV dysfunction is poorly understood. Using 18F-florbetapir positron emission tomography/computed tomography (PET/CT), we aimed to quantify RV amyloid; correlate RV amyloid with RV structure and function; determine the independent contributions of RV, left ventricular (LV), and lung amyloid to RV function; and associate RV amyloid with major adverse cardiac events (MACE: death, heart failure hospitalization, cardiac transplantation).

METHODS AND RESULTS

We prospectively enrolled 106 participants with AL amyloidosis (median age 62 years, 55% males) who underwent 18F-florbetapir PET/CT, magnetic resonance imaging, and echocardiography. 18F-florbetapir PET/CT identified RV amyloid in 63% of those with and 40% of those without cardiac involvement by conventional criteria. RV amyloid burden correlated with RV ejection fraction (EF), RV free wall longitudinal strain (FWLS), RV wall thickness, RV mass index, N-terminal pro-brain natriuretic peptide, troponin T, LV amyloid, and lung amyloid (each P < 0.001). In multivariable analysis, RV amyloid burden, but not LV or lung amyloid burden, predicted RV dysfunction (EF P = 0.014; FWLS P < 0.001). During a median follow-up of 28 months, RV amyloid burden predicted MACE (P < 0.001).

CONCLUSION

This study shows for the first time that 18F-florbetapir PET/CT identifies early RV amyloid in systemic AL amyloidosis prior to alterations in RV structure and function. Increasing RV amyloid on 18F-florbetapir PET/CT is associated with worse RV structure and function, predicts RV dysfunction, and predicts MACE. These results imply a central role for RV amyloid in the pathogenesis of RV dysfunction.

Preclinical evaluation of Tc-99m p5+14 peptide for SPECT detection of cardiac amyloidosis

INTRODUCTION

Amyloid deposition is a cause of restrictive cardiomyopathy. Patients who present with cardiac disease can be evaluated for transthyretin (TTR)-associated cardiac amyloidosis using nuclear imaging with 99mTc-labeled pyrophosphate (PYP); however, light chain-associated (AL) cardiac amyloid is generally not detected using this tracer. As an alternative, the amyloid-binding peptide p5+14 radiolabeled with iodine-124 has been shown to be an effective pan-amyloid radiotracer for PET/CT imaging. Here, a 99mTc-labeled form of p5+14 peptide has been prepared to facilitate SPECT/CT imaging of cardiac amyloidosis.

METHOD

A synthesis method suitable for clinical applications has been used to prepare 99mTc-labeled p5+14 and tested for peptide purity, product bioactivity, radiochemical purity and stability. The product was compared with99mTc-PYP for cardiac SPECT/CT imaging in a mouse model of AA amyloidosis and for reactivity with human tissue sections from AL and TTR patients.

RESULTS

The 99mTc p5+14 tracer was produced with >95% yields in radiopurity and bioactivity with no purification steps required and retained over 95% peptide purity and >90% bioactivity for >3 h. In mice, the tracer detected hepatosplenic AA amyloid as well as heart deposits with uptake ~5 fold higher than 99mTc-PYP. 99mTc p5+14 effectively bound human amyloid deposits in the liver, kidney and both AL- and ATTR cardiac amyloid in tissue sections in which 99mTc-PYP binding was not detectable.

CONCLUSION

99mTc-p5+14 was prepared in minutes in >20 mCi doses with good performance in preclinical studies making it suitable for clinical SPECT/CT imaging of cardiac amyloidosis.

Outcome prediction by myocardial external efficiency from 11 C-acetate positron emission tomography in cardiac amyloidosis

AIMS

This study aimed to study the prognostic value of myocardial oxygen consumption (MVO2 ) and myocardial external efficiency (MEE) from 11 C-acetate positron emission tomography (PET) in cardiac amyloidosis (CA) patients.

METHODS AND RESULTS

Forty-eight CA patients, both transthyretin (ATTR) and immunoglobulin light chain (AL) amyloidosis, and 20 controls were included. All subjects were examined with 11 C-acetate PET and echocardiography. MVO2 , forward stroke volume (FSV), and left ventricular mass (LVM) were derived from 11 C-acetate PET and used to calculate MEE. CA patients were followed for survival and the prognostic impact of clinical, echocardiographic, and 11 C-acetate PET parameters was analysed. MVO2 and MEE were reduced in CA compared with controls, but without significant difference between deceased and surviving CA patients. The ratio of 11 C-acetate PET-derived FSV and LVM was also reduced in CA and significantly lowered in deceased patients compared with survivors. In univariate analysis, New York Heart Association class, N-terminal pro-brain natriuretic peptide, and the 11 C-acetate PET parameters FSV/LVM and MEE were the strongest prognostic factors. Of the 11 C-acetate PET parameters, FSV/LVM was the strongest survival predictor with hazard ratio of 0.56 per 0.1 mL/g (95% confidence interval 0.39-0.81, P = 0.002) and independently prognostic in a multivariate model. MEE significantly separated deceased from surviving CA patients with the cut-off of 15.7% (P = 0.032). Survival was significantly shorter with FSV/LVM below 0.27 mL/g (P < 0.001), also when separating AL- and ATTR-CA.

CONCLUSIONS

Reduced MEE was associated with shorter survival in CA patients, but FSV/LVM was the strongest survival predictor and the only independently prognostic 11 C-acetate PET parameter in multivariate analysis.

Amyloid consults do not have to be vexing

Diagnosing amyloidosis can be challenging due to its clinical heterogeneity, need for multiple specialists to make a diagnosis, and lack of a single diagnostic test for the disease. Patients are often diagnosed late, in advanced stage, and after exhibiting multiple symptoms and signs for a long period. It is important to develop a clinical suspicion of amyloidosis, particularly in those with multisystemic symptoms and high-risk patient populations such as those with precursor hematologic conditions. A systematic approach to the workup of suspected amyloidosis is key, including a comprehensive clinical assessment, laboratory tests to assess organ involvement, advanced imaging studies, screening for plasma cell disorder, and tissue biopsy when necessary. After making a diagnosis of amyloidosis, accurate typing of amyloid deposits, differentiating between localized and systemic amyloidosis, and appropriately staging the disease is important. Early diagnosis is crucial for improving patient outcomes and quality of life in light chain amyloidosis.

Value of nuclide scintigraphy in the diagnosis and prognosis of cardiac amyloidosis

Amyloidosis is a local or systemic disease caused by the deposition of misfolded proteins outside the cell, with rapid progression, and dire prognosis. Common types of cardiac amyloidosis are monoclonal immunoglobulin light chain amyloidosis (AL-CA) and transthyretin cardiac amyloidosis (ATTR-CA). Nuclear medicine examinations can be accurate, rapid, and non-invasive to help diagnose diseases and can effectively predict the prognosis of patients with CA. Technetium (99Tcm)-labeled bisphosphonate imaging has been included in the consensus of experts and has become the first-line imaging method for the diagnosis of ATTR-CA. 123I-metaiodoenzylguanidine (MIBG) as a norepinephrine analogue can effectively assess cardiac sympathetic innervation in patients with CA. Aβ- amyloid imaging agents such as 11C-pittsburgh compound B and 18F-flubetaben are expected to be new techniques for diagnosing AL-CA and incorporating them into cardiac staging systems for AL-CA patients in the future. New imaging agents such as 18F-NaF has been widely used in the diagnosis, treatment response monitoring, and prognosis assessment of CA. Summarizing the research value of nuclide imaging in CA may provide new ideas for clinical realization of early detection of CA and accurate assessment of disease prognosis.

[Giant tongue leading to dysphagia in light chain amyloidosis patient]

Introduction

Macroglossia as a clinical manifestation of systemic amyloidosis is a rare condition, occurring in less than 9% of all types of amyloidosis. The aim of this report is to present the diagnostic approach of a patient with macroglossia, providing a systematic approach and considering relevant diagnostic possibilities during their evaluation.

Clinical case

We present the case of a 60-year-old man who presented with a progressively enlarging giant tongue for six months, causing dysphagia and reduced oral opening. A tongue biopsy was taken, which histopathologically exhibited homogenous eosinophilic amyloid-like material. Congo red staining showed amyloid material with red dye under light microscopy and apple-green birefringence under polarized light. Bone marrow biopsy showed 30% plasma cells, allowing for a definitive diagnosis of soft tissue amyloidosis. Although it is a benign lesion, localized amyloidosis should be differentiated from systemic forms.

Conclusions

The approach of patients with macroglossia is complex due to the diagnostic possibilities, from endocrinological causes, neoplastic, and even by deposit; Being an isolated sign in a patient is a challenge in its approach, because the involvement of the airway is the main complication to avoid in these patients.

Cardiac Amyloid Quantification Using 124I-Evuzamitide (124I-P5+14) Versus 18F-Florbetapir: A Pilot PET/CT Study

BACKGROUND

Cardiac amyloid quantification could advance early diagnosis of amyloid cardiomyopathy (CMP) and treatment monitoring. However, current imaging tools are based on indirect measurements. 124I-evuzamitide is a novel pan-amyloid radiotracer binding to amyloid deposits from multiple amyloidogenic proteins. Its ability to quantify cardiac amyloid has not yet been investigated.

OBJECTIVES

The objectives of this pilot study were to quantify myocardial 124I-evuzamitide uptake and to compare its diagnostic value to 18F-florbetapir in participants with amyloid CMP and control subjects.

METHODS

This study included 46 participants: 12 with light-chain (AL) CMP, 12 with wild-type transthyretin (ATTRwt) CMP, 2 with hereditary amyloidosis, and 20 control subjects. All amyloidosis participants underwent positron emission tomography/computed tomography with 124I-evuzamitide and 18F-florbetapir. Control subjects underwent 124I-evuzamitide (n = 10) or 18F-florbetapir (n = 8) positron emission tomography/computed tomography. Left ventricular percent injected dose (LV% ID) was measured as mean activity concentration × myocardial volume/injected activity. High LV %ID was defined using Youden's index.

RESULTS

In CMP participants, median age was 74 years and 92% were men. 124I-evuzamitide LV %ID differed across groups: median AL-CMP 1.48 (IQR: 1.12-1.89), ATTRwt-CMP 2.12 (IQR: 1.66-2.47), and control subjects 0.00 (IQR: 0.00-0.01; overall P < 0.001). High LV %ID perfectly discriminated CMP from control subjects. Discrimination performance was similar for 18F-florbetapir LV %ID. Notably, for ATTRwt-CMP, LV %ID was higher with 124I-evuzamitide than 18F-florbetapir (P = 0.002). 124I-evuzamitide LV %ID was correlated with interventricular septum thickness (Spearman's ρ = 0.78) and LV global longitudinal strain (ρ = 0.54) from echocardiography, and with LV mass index (ρ = 0.82) and extracellular volume (ρ = 0.51) from cardiac magnetic resonance.

CONCLUSIONS

124I-evuzamitide demonstrates uptake by cardiac amyloid and accurately discriminates amyloid CMP from control subjects. In AL-CMP, discrimination performance is similar to 18F-florbetapir. In ATTRwt-CMP, performance may be better with 124I-evuzamitide. Moderate-to-strong correlations of 124I-evuzamitide uptake with cardiac structural and functional metrics suggest valid amyloid quantification. Hence, 124I-evuzamitide is a promising novel radiotracer to detect and quantify cardiac amyloid.

Molecular Imaging of Systemic and Cardiac Amyloidosis: Recent Advances and Focus on the Future

Myocardial infiltration by amyloid fibrils causes a severe and progressive form of heart failure. Until recently, this was not treatable. Several novel therapies have recently become available, increasing the urgency to make an accurate diagnosis, evaluate risk, and determine treatment response. Molecular imaging with positron-emitting amyloid tracers has a key emerging role in the evaluation and management of cardiac amyloidosis. In this review, we discuss molecular imaging of cardiac amyloidosis using amyloid PET tracers, including recent advances with a focus on the future.

Myocardial Characterization for Early Diagnosis, Treatment Response Monitoring, and Risk Assessment in Systemic Light-Chain Amyloidosis

Aims

In systemic light-chain (AL) amyloidosis, cardiac involvement portends poor prognosis. Using myocardial characteristics on magnetic resonance imaging (MRI), this study aimed to detect early myocardial alterations, to analyze temporal changes with plasma cell therapy, and to predict risk of major adverse cardiac events (MACE) in AL amyloidosis.

Methods and Results

Participants with recently diagnosed AL amyloidosis were prospectively enrolled. Presence of AL cardiomyopathy (AL-CMP vs. AL-non-CMP) was determined by abnormal cardiac biomarkers. MRI was performed at baseline and 6 months, with 12-month imaging in AL-CMP cohort. MACE was defined as all-cause death, heart failure hospitalization, or cardiac transplantation. Mayo AL stage was based on troponin T, NT-proBNP, and difference in free light chains. The study cohort included 80 participants (median age 62 years, 58% males). Median left ventricular extracellular volume (ECV) was significantly higher in AL-CMP (53% vs. 30%, p<0.001). ECV was abnormal (>32%) in all AL-CMP and in 47% of AL-non-CMP. ECV tended to increase at 6 months and decreased significantly from 6 to 12 months in AL-CMP (median -3%, p=0.011). ECV was strongly associated with MACE (p<0.001), and improved MACE prediction when added to Mayo AL stage (p=0.002). ECV≤32% identified a cohort without MACE, while ECV>48% identified a cohort with 74% MACE.

Conclusions

In AL amyloidosis, ECV detects subclinical cardiomyopathy. ECV tends to increase from baseline to 6 months and decreases significantly from 6 and 12 months of plasma cell therapy in AL-CMP. ECV provides excellent risk stratification and offers additional prognostic performance over Mayo AL stage.

Comprehensive assessment of molecular function, tissue characterization, and hemodynamic performance by non-invasive hybrid imaging: Potential role of cardiac PETMR

Noninvasive cardiovascular imaging plays a key role in diagnosis and patient management including monitoring treatment efficacy. The usefulness of noninvasive cardiovascular imaging has been extensively studied and shown to have high diagnostic reliability and prognostic significance, while the nondiagnostic results frequently encountered with single imaging modality require complementary or alternative imaging techniques. Hybrid cardiac imaging was initially introduced to integrate anatomical and functional information to enhance the diagnostic performance, and lately employed as a strategy for comprehensive assessment of the underlying pathophysiology of diseases. More recently, the utility of computed tomography has grown in diversity, and emerged from being an exploratory technique allowing functional measurement such as stress dynamic perfusion. Cardiac magnetic resonance imaging (CMR) is widely accepted as a robust tool for evaluation of cardiac function, fibrosis, and edema, yielding high spatial resolution and soft-tissue contrast. However, the use of intravenous contrast materials is typically required for accurate diagnosis with these imaging modalities, despite the associated risk of renal toxicity. Nuclear cardiology, established as a molecular imaging technique, has advantages in visualization of the disease-specific biological process at cellular level using numerous probes without requiring contrast materials. Various imaging modalities should be appropriately used sequentially to assess concomitant disease and the progression over time. Therefore, simultaneous evaluation combining high spatial resolution and disease-specific imaging probe is a useful approach to identify the regional activity and the stage of the disease. Given the recent advance and potential of multiparametric CMR and novel nuclide tracers, hybrid positron emission tomography MR is becoming an ideal tool for disease-specific imaging.

Phenotyping heart failure by nuclear imaging of myocardial perfusion, metabolism, and molecular targets

Nuclear imaging techniques can detect and quantify pathophysiological processes underlying heart failure, complementing evaluation of cardiac structure and function with other imaging modalities. Combined imaging of myocardial perfusion and metabolism can identify left ventricle dysfunction caused by myocardial ischaemia that may be reversible after revascularization in the presence of viable myocardium. High sensitivity of nuclear imaging to detect targeted tracers has enabled assessment of various cellular and subcellular mechanisms of heart failure. Nuclear imaging of active inflammation and amyloid deposition is incorporated into clinical management algorithms of cardiac sarcoidosis and amyloidosis. Innervation imaging has well-documented prognostic value with respect to heart failure progression and arrhythmias. Emerging tracers specific for inflammation and myocardial fibrotic activity are in earlier stages of development but have demonstrated potential value in early characterization of the response to myocardial injury and prediction of adverse left ventricular remodelling. Early detection of disease activity is a key for transition from broad medical treatment of clinically overt heart failure towards a personalized approach aimed at supporting repair and preventing progressive failure. This review outlines the current status of nuclear imaging in phenotyping heart failure and combines it with discussion on novel developments.

Prognostic Value of Left Ventricular 18 F-Florbetapir Uptake in Systemic Light-Chain Amyloidosis

Background

Myocardial immunoglobulin light-chain (AL) amyloid deposits trigger heart failure, cardiomyocyte stretch and myocardial injury, leading to adverse cardiac outcomes. Positron emission tomography/computed tomography (PET/CT) with 18 F-florbetapir, a novel amyloid-targeting radiotracer, can quantify left ventricular (LV) amyloid burden, but its prognostic value is not known. Therefore, we aimed to evaluate the prognostic value of LV amyloid burden quantified by 18 F-florbetapir PET/CT and to identify mechanistic pathways mediating its association with outcomes.

Methods

Eighty-one participants with newly-diagnosed systemic AL amyloidosis were prospectively enrolled and underwent 18 F-florbetapir PET/CT. LV amyloid burden was quantified using 18 F-florbetapir LV percent injected dose (%ID). Mayo AL stage was determined using troponin T, N-terminal pro-B-type natriuretic peptide (NT-proBNP), and difference between involved and uninvolved free light chain levels. Major adverse cardiac events (MACE) were defined as all-cause death, heart failure hospitalization, or cardiac transplantation within 12 months.

Results

Among participants (median age 61 years, 57% males), 36% experienced MACE. Incidence of MACE increased across tertiles of LV amyloid burden from 7% to 63% (p<0.001). LV amyloid burden was significantly associated with MACE in univariable analysis (hazard ratio 1.45, 95% confidence interval 1.15-1.82, p=0.002). However, this association became non-significant in multivariable analyses adjusted for Mayo AL stage. Mediation analysis showed that the association between 18 F-florbetapir LV %ID and MACE was primarily mediated by NT-proBNP (p<0.001), a marker of cardiomyocyte stretch and component of Mayo AL stage.

Conclusion

In this first study to link cardiac 18 F-florbetapir uptake to subsequent outcomes, LV amyloid burden estimated by LV %ID predicted MACE in AL amyloidosis. But this effect was not independent of Mayo AL stage. LV amyloid burden was associated with MACE primarily via NT-pro-BNP, a marker of cardiomyocyte stretch and component of Mayo AL stage. These findings provide novel insights into the mechanism through which myocardial AL amyloid leads to MACE.

Clinical Perspective

In systemic light-chain (AL) amyloidosis, cardiac involvement is the key determinant of adverse outcomes. Usually, prognosis is based on the Mayo AL stage, determined by troponin T, N-terminal pro-B-type natriuretic peptide (NT-proBNP), and the difference between involved and uninvolved immunoglobulin free light chain levels (dFLC). Cardiac amyloid burden is not considered in this staging. In the present study, we used the amyloid-specific radiotracer 18 F-florbetapir to quantify left ventricular (LV) amyloid burden in 81 participants with newly-diagnosed AL amyloidosis and evaluated its prognostic value on major adverse outcomes (MACE: all-cause death, heart failure hospitalization, or cardiac transplantation within 12 months). We found that higher LV amyloid burden by 18 F-florbetapir positron emission tomography/computed tomography (PET/CT) was strongly associated with MACE. However, this association became non-significant after adjustment for the Mayo AL stage. Mediation analysis offered novel pathophysiological insights, implying that LV amyloid burden leads to MACE predominantly through cardiomyocyte stretch and light chain toxicity (by NT-proBNP), rather than through myocardial injury (by troponin T), also considering the severity of plasma cell dyscrasia (by dFLC). This mediation by NT-proBNP may explain why the association with outcomes was non-significant with adjustment for Mayo AL stage. Together, these results establish quantitative 18 F-florbetapir PET/CT as a valid method to predict adverse outcomes in AL amyloidosis. These results support the use of 18 F-florbetapir PET/CT to measure the effects of novel fibril-depleting therapies, in addition to plasma cell therapy, to improve outcomes in systemic AL amyloidosis.

Molecular Design of Magnetic Resonance Imaging Agents Binding to Amyloid Deposits

The ability to detect and monitor amyloid deposition in the brain using non-invasive imaging techniques provides valuable insights into the early diagnosis and progression of Alzheimer's disease and helps to evaluate the efficacy of potential treatments. Magnetic resonance imaging (MRI) is a widely available technique offering high-spatial-resolution imaging. It can be used to visualize amyloid deposits with the help of amyloid-binding diagnostic agents injected into the body. In recent years, a number of amyloid-targeted MRI probes have been developed, but none of them has entered clinical practice. We review the advances in the field and deduce the requirements for the molecular structure and properties of a diagnostic probe candidate. These requirements make up the base for the rational design of MRI-active small molecules targeting amyloid deposits. Particular attention is paid to the novel cryo-EM structures of the fibril aggregates and their complexes, with known binders offering the possibility to use computational structure-based design methods. With continued research and development, MRI probes may revolutionize the diagnosis and treatment of neurodegenerative diseases, ultimately improving the lives of millions of people worldwide.

The flutemetamol analogue cyano-flutemetamol detects myocardial AL and ATTR amyloid deposits: a post-mortem histofluorescence analysis

BACKGROUND

[18F]flutemetamol is a PET radioligand used to image brain amyloid, but its detection of myocardial amyloid is not well-characterized. This histological study characterized binding of fluorescently labeled flutemetamol (cyano-flutemetamol) to amyloid deposits in myocardium.

METHODS

Myocardial tissue was obtained post-mortem from 29 subjects with cardiac amyloidosis including transthyretin wild-type (ATTRwt), hereditary/variant transthyretin (ATTRv) and immunoglobulin light-chain (AL) types, and from 10 cardiac amyloid-free controls. Most subjects had antemortem electrocardiography, echocardiography, SPECT and cardiac MRI. Cyano-flutemetamol labeling patterns and integrated density values were evaluated relative to fluorescent derivatives of Congo red (X-34) and Pittsburgh compound-B (cyano-PiB).

RESULTS

Cyano-flutemetamol labeling was not detectable in control subjects. In subjects with cardiac amyloidosis, cyano-flutemetamol labeling matched X-34- and cyano-PiB-labeled, and transthyretin- or lambda light chain-immunoreactive, amyloid deposits and was prevented by formic acid pre-treatment of myocardial sections. Cyano-flutemetamol mean fluorescence intensity, when adjusted for X-34 signal, was higher in the ATTRwt than the AL group. Cyano-flutemetamol integrated density correlated strongly with echocardiography measures of ventricular septal thickness and posterior wall thickness, and with heart mass.

CONCLUSION

The high selectivity of cyano-flutemetamol binding to myocardial amyloid supports the diagnostic utility of [18F]flutemetamol PET imaging in patients with ATTR and AL types of cardiac amyloidosis.

Clinical Confirmation of Pan-Amyloid Reactivity of Radioiodinated Peptide 124I-p5+14 (AT-01) in Patients with Diverse Types of Systemic Amyloidosis Demonstrated by PET/CT Imaging

There are at least 20 distinct types of systemic amyloidosis, all of which result in the organ-compromising accumulation of extracellular amyloid deposits. Amyloidosis is challenging to diagnose due to the heterogeneity of the clinical presentation, yet early detection is critical for favorable patient outcomes. The ability to non-invasively and quantitatively detect amyloid throughout the body, even in at-risk populations, before clinical manifestation would be invaluable. To this end, a pan-amyloid-reactive peptide, p5+14, has been developed that is capable of binding all types of amyloid. Herein, we demonstrate the ex vivo pan-amyloid reactivity of p5+14 by using peptide histochemistry on animal and human tissue sections containing various types of amyloid. Furthermore, we present clinical evidence of pan-amyloid binding using iodine-124-labeled p5+14 in a cohort of patients with eight (n = 8) different types of systemic amyloidosis. These patients underwent PET/CT imaging as part of the first-in-human Phase 1/2 clinical trial evaluating this radiotracer (NCT03678259). The uptake of 124I-p5+14 was observed in abdominothoracic organs in patients with all types of amyloidosis evaluated and was consistent with the disease distribution described in the medical record and literature reports. On the other hand, the distribution in healthy subjects was consistent with radiotracer catabolism and clearance. The early and accurate diagnosis of amyloidosis remains challenging. These data support the utility of 124I-p5+14 for the diagnosis of varied types of systemic amyloidosis by PET/CT imaging.

18 F-Flutemetamol PET/CT for Transthyretin Amyloid Cardiomyopathy : Timing Matters

ABSTRACT

We report 18 F-flutemetamol PET/CT finding in an 88-year-old man with cognitive impairment and transthyretin amyloid cardiomyopathy. Early phase PET/CT images showed significantly increased myocardial uptake, but there was no myocardial uptake in delayed phase PET/CT images. A dual-time-point amyloid PET/CT imaging may be helpful to diagnose and differentiate subtypes of amyloid cardiomyopathy in patients with suspected cardiac amyloidosis.

AL Amyloidosis for Cardiologists: Awareness, Diagnosis, and Future Prospects: JACC: CardioOncology State-of-the-Art Review

Amyloid light chain (AL) amyloidosis is a rare, debilitating, often fatal disease. Symptoms of cardiomyopathy are common presenting features, and patients often are referred to cardiologists. Cardiac amyloid infiltration is the leading predictor of death. However, the variable presentation and perceived rarity of the disease frequently lead to delay in suspecting amyloidosis as a cause of heart failure, leading to misdiagnoses and a marked delay in diagnosis, with devastating consequences for the patient. A median time from symptom onset to correct diagnosis of about 2 years is often too long when median survival from diagnosis for patients with AL amyloidosis and cardiomyopathy is 4 months to 2 years. The authors highlight the challenges to diagnosis, identify gaps in the current knowledge, and summarize novel treatments on the horizon to raise awareness about the critical need for early recognition of symptoms and diagnosis of AL amyloidosis aimed at accelerating treatment and improving outcomes for patients.

Noninvasive Diagnostics of Renal Amyloidosis: Current State and Perspectives

Amyloidoses is a group of diseases characterized by the accumulation of abnormal proteins (called amyloids) in different organs and tissues. For systemic amyloidoses, the disease is related to increased levels and/or abnormal synthesis of certain proteins in the organism due to pathological processes, e.g., monoclonal gammopathy and chronic inflammation in rheumatic arthritis. Treatment of amyloidoses is focused on reducing amyloidogenic protein production and inhibition of its aggregation. Therapeutic approaches critically depend on the type of amyloidosis, which underlines the importance of early differential diagnostics. In fact, the most accurate diagnostics of amyloidosis and its type requires analysis of a biopsy specimen from the disease-affected organ. However, absence of specific symptoms of amyloidosis and the invasive nature of biomaterial sampling causes the late diagnostics of these diseases, which leads to a delayed treatment, and significantly reduces its efficacy and patient survival. The establishment of noninvasive diagnostic methods and discovery of specific amyloidosis markers are essential for disease detection and identification of its type at earlier stages, which enables timely and targeted treatment. This review focuses on current approaches to the diagnostics of amyloidoses, primarily with renal involvement, and research perspectives in order to design new specific tests for early diagnosis.

Nuclear Molecular Imaging of Disease Burden and Response to Treatment for Cardiac Amyloidosis

Simple Summary

Cardiac amyloidosis (CA) is characterized by extracellular infiltration and deposition of amyloid fibrils primarily derived from the circulating transthyretin protein (TTR) or immunoglobulin light chain (AL). With the development of non-invasive diagnostic approaches and the emergence of new pharmacotherapeutic treatments for CA, the transformative effects of bone scintigraphy have been important in diagnosing TTR-CA. Positron emission tomography (PET) imaging is another promising, non-invasive option for the diagnosis of CA and may help differentiate between ATTR and AL amyloidosis. Bone-seeking single-photon emission tomography/computed tomography (SPECT/CT) quantification and amyloid-targeting PET imaging could be useful as a new strategy for disease burden and therapy monitoring to provide more insights into therapy response assessed by quantifying the amyloid burden in CA.

Abstract

Cardiac amyloidosis (CA) is a heterogeneous group of diseases in which extracellular insoluble amyloid proteins are deposited in specific organs and tissues locally or systemically, thereby interfering with physiological function. Transthyretin protein (TTR) and light chain (AL) amyloidosis are the most common types of cardiac amyloidosis. Radionuclide bone scintigraphy has recently become the most common non-invasive test for the diagnosis of TTR-CA but is of limited value for the diagnosis of AL-CA. PET has proved promising for the diagnosis of CA and its applications are expected to expand in the future. This review summarizes the current bone scintigraphy and amyloid-targeting Positron emission tomography (PET) imaging, the binding imaging properties of radiotracers, and the values of diagnosis, prognosis, and monitoring therapy response in CA.

[Value of (11)C-PiB PET/MRI in the evaluation of organ involvement in primary systemic light chain amyloidosis]

Objective: To analyze the value of (11)C-PiB PET/MRI for evaluating organ involvement in patients with primary light chain amyloidosis (pAL) . Methods: The clinical data of 20 patients with pAL and 3 healthy volunteers from January 2019 to October 2021 were retrospectively analyzed. The correlation between the organ involvement evaluated by clinical standards and PET/MRI was compared. The relationship between cardiac-related biological indicators, disease stage, and the maximum standardized uptake value (SUVmax) were analyzed. The relationship between 24-hour urinary protein quantification and kidney SUVmax was analyzed. Results: ①In 20 patients (18 newly diagnosed patients and 2 non-newly diagnosed patients) ,(11)C-PiB positive uptake was observed in the heart (15 patients, 75%) , lung (8 patients, 40%) , bone marrow (10 patients, 50%) , muscle (10 patients, 50%) , tongue muscle (7 patients, 35%) , thyroid (6 patients, 30%) , salivary gland (4 patients, 20%) , spleen (2 patients, 10%) , and stomach wall (1 patient, 5%) . ②Organ involvement on (11)C-PiB PET/MRI showed good correlations with the clinical evaluation criteria for the heart and bone marrow. The positive rate of PET/MRI evaluation in the lung, spleen, gland, muscle, and tongue muscle was significantly higher than the clinical criteria. However, (11)C-PiB PET/MRI has limitations in the evaluation of the nervous system and fat tissue. ③To analyze the relationship between cardiac-related biological indexes and the SUVmax of the heart in 13 newly diagnosed patients. Patients with left ventricular ejection fraction (LVEF) <50% and interventricular septal thickness (ISV) ≥1.2 cm showed a higher SUVmax than patients with LVEF ≥50% and ISV<1.2 cm (P<0.05) .There are significant differences in the SUVmax of the heart between the Mayo2004 stage and the Mayo2012 stage. The later the disease stage, the higher the SUVmax (P<0.05) . The SUVmax of the heart was positively correlated with cardiac troponin I (cTnI) and N-terminal pro-brain natriuretic peptide (NT-proBNP) (P<0.01) .There was no significant correlation between renal SUVmax and 24-hour urine protein (P>0.05) . Conclusion: Whole body (11)C-PiB PET/MRI, as a visualization system of amyloid protein, is used to qualitatively evaluate organ involvement, which can improve the level of early non-invasive diagnosis. Whole body (11)C-PiB PET/MRI can be used to perform quantitative evaluation of organ levels, especially the heart, which is expected to evaluate organ function and predict disease prognosis more accurately.

Amyloid Arthropathy and Pseudomyopathy Associated With Multiple Myeloma Detected by 18F-Florapronol Amyloid PET/CT

ABSTRACT

We report a case of amyloid arthropathy and pseudomyopathy with multiple myeloma, detected by amyloid PET/CT using 18F-florapronol. Bone scintigraphy and 18F-FDG PET/CT in a multiple myeloma patient revealed uneven soft tissue uptakes, especially at periarticular areas. The joint capsule and intermuscular fascia showed enhancement on CT, whereas muscle enzymes were normal. These suggested amyloid arthropathy with pseudomyopathy. 18F-Florapronol amyloid PET/CT showed extensive soft tissue uptakes. Amyloid arthropathy and pseudomyopathy were confirmed after biopsy. This is the first report of amyloid PET/CT aiding in the diagnosis of unusual presentation of systemic amyloidosis.

Pulmonary 99mTc-HMDP uptake correlates with restrictive ventilatory defects and abnormal lung reactance in transthyretin cardiac amyloidosis patients

BACKGROUND

Pulmonary involvement in individuals with transthyretin cardiac amyloidosis is unclear. The aim of this study was to quantify 99mTc-hydroxy methylene diphosphonate (HMDP) lung retention in hereditary transthyretin (ATTRv) cardiac amyloidosis patients and to relate tracer uptake intensity to pulmonary function and aerobic capacity.

METHODS

We prospectively enrolled 20 patients with biopsy-proven ATTRv cardiac amyloidosis and 20 control subjects. Cardiac involvement was confirmed by echocardiography and nuclear imaging using 99mTc-HMDP. Semi-quantitative analysis of the heart, rib and lung retention was assessed using a simple region of interest technique. Pulmonary function was evaluation by the means of whole-body plethysmography, diffusing capacity of the lung for carbon monoxide, forced oscillation technique and cardiopulmonary exercise testing.

RESULTS

Pulmonary tracer uptake estimated by lung to rib retention ratio was higher in ATTRv amyloidosis patients compared with control subjects: median 0.62 (0.55-0.69) vs 0.51 (0.46-0.60); p = 0.014. Analysis of relation between lung 99mTc-HMDP retention and pulmonary function parameters shown statistically significant correlations with total lung volume (% predicted), lung reactance (Xrs 5 Hz) and peak VO2, suggesting total lung capacity restriction impaired elastic properties of the lung and poor aerobic capacity.

CONCLUSION

Our study suggests that some grade of pulmonary retention of 99mTc-HMDP may occur in patients with cardiac ATTRv amyloidosis, which can elicit deleterious effects on patient's lung function and aerobic capacity.

Hybrid total-body pet scanners-current status and future perspectives

Purpose Since the 1990s, PET has been successfully combined with MR or CT systems. In the past years, especially PET systems have seen a trend towards an enlarged axial field of view (FOV), up to a factor of ten. Methods Conducting a thorough literature research, we summarize the status quo of contemporary total-body (TB) PET/CT scanners and give an outlook on possible future developments. Results Currently, three human TB PET/CT systems have been developed: The PennPET Explorer, the uExplorer, and the Biograph Vision Quadra realize aFOVs between 1 and 2 m and show a tremendous increase in system sensitivity related to their longer gantries. Conclusion The increased system sensitivity paves the way for short-term, low-dose, and dynamic TB imaging as well as new examination methods in almost all areas of imaging.

First in Human Evaluation and Dosimetry Calculations for Peptide 124I-p5+14-a Novel Radiotracer for the Detection of Systemic Amyloidosis Using PET/CT Imaging

PURPOSE

Accurate diagnosis of amyloidosis remains a significant clinical challenge and unmet need for patients. The amyloid-reactive peptide p5+14 radiolabeled with iodine-124 has been developed for the detection of amyloid by PET/CT imaging. In a first-in-human evaluation, the dosimetry and tissue distribution of ¹²⁴I-p5+14 peptide in patients with systemic amyloidosis. Herein, we report the dosimetry and dynamic distribution in the first three enrolled patients with light chain-associated (AL) amyloidosis.

PROCEDURES

The radiotracer was assessed in a single-site, open-label phase 1 study (NCT03678259). The first three patients received a single intravenous infusion of ¹²⁴I-p5+14 peptide (≤37 MBq). Serial PET/CT imaging was performed during the 48 h post-infusion. Dosimetry was determined as a primary endpoint for each patient and gender-averaged mean values were calculated. Pharmacokinetic parameters were estimated from whole blood radioactivity measurements and organ-based time activity data. Lastly, the biodistribution of radiotracer in major organs was assessed visually and compared to clinically appreciated organ involvement.

RESULTS

Infusion of the ¹²⁴I-p5+14 was well tolerated with rapid uptake in the heart, kidneys, liver, spleen, pancreas, and lung. The gender-averaged whole-body effective radiation dose was estimated to be 0.23 (± 0.02) mSv/MBq with elimination of the radioactivity via renal and gastrointestinal routes. The whole blood elimination t_1/2 of 21.9 ± 7.6 h. Organ-based activity concentration measurements indicated that AUC_last tissue:blood ratios generally correlated with the anticipated presence of amyloid. Peptide uptake was observed in 4/5 clinically suspected organs, as noted in the medical record, as well as six anatomic sites generally associated with amyloidosis in this population.

CONCLUSION

Peptide ¹²⁴I-p5+14 rapidly distributes to anatomic sites consistent with the presence of amyloid in patients with systemic AL. The dosimetry estimates established in this cohort are acceptable for whole-body PET/CT imaging. Pharmacokinetic parameters are heterogeneous and consistent with uptake of the tracer in an amyloid compartment. PET/CT imaging of ¹²⁴I-p5+14 may facilitate non-invasive detection of amyloid in multiple organ systems.

Predicting the nature of pleural effusion in patients with lung adenocarcinoma based on 18F-FDG PET/CT

Background

This study aims to establish a predictive model on the basis of ¹⁸F-FDG PET/CT for diagnosing the nature of pleural effusion (PE) in patients with lung adenocarcinoma.

Methods

Lung adenocarcinoma patients with PE who underwent ¹⁸F-FDG PET/CT were collected and divided into training and test cohorts. PET/CT parameters and clinical information in the training cohort were collected to estimate the independent predictive factors of malignant pleural effusion (MPE) and to establish a predictive model. This model was then applied to the test cohort to evaluate the diagnostic efficacy.

Results

A total of 413 lung adenocarcinoma patients with PE were enrolled in this study, including 245 patients with MPE and 168 patients with benign PE (BPE). The patients were divided into training (289 patients) and test (124 patients) cohorts. CEA, SUVmax of tumor and attachment to the pleura, obstructive atelectasis or pneumonia, SUVmax of pleura, and SUVmax of PE were identified as independent significant factors of MPE and were used to construct a predictive model, which was graphically represented as a nomogram. This predictive model showed good discrimination with the area under the curve (AUC) of 0.970 (95% CI 0.954–0.986) and good calibration. Application of the nomogram in the test cohort still gave good discrimination with AUC of 0.979 (95% CI 0.961–0.998) and good calibration. Decision curve analysis demonstrated that this nomogram was clinically useful.

Conclusions

Our predictive model based on ¹⁸F-FDG PET/CT showed good diagnostic performance for PE, which was helpful to differentiate MPE from BPE in patients with lung adenocarcinoma.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13550-021-00850-2.

Cardiac hybrid imaging: novel tracers for novel targets

Non-invasive cardiac imaging has explored enormous advances in the last few decades. In particular, hybrid imaging represents the fusion of information from multiple imaging modalities, allowing to provide a more comprehensive dataset compared to traditional imaging techniques in patients with cardiovascular diseases. The complementary anatomical, functional and molecular information provided by hybrid systems are able to simplify the evaluation procedure of various pathologies in a routine clinical setting. The diagnostic capability of hybrid imaging modalities can be further enhanced by introducing novel and specific imaging biomarkers. The aim of this review is to cover the most recent advancements in radiotracers development for SPECT/CT, PET/CT, and PET/MRI for cardiovascular diseases.

Procedural recommendations of cardiac PET/CT imaging: standardization in inflammatory-, infective-, infiltrative-, and innervation- (4Is) related cardiovascular diseases: a joint collaboration of the EACVI and the EANM: summary

With this summarized document we share the standard for positron emission tomography (PET)/(diagnostic)computed tomography (CT) imaging procedures in cardiovascular diseases that are inflammatory, infective, infiltrative, or associated with dysfunctional innervation (4Is) as recently published in the European Journal of Nuclear Medicine and Molecular Imaging. This standard should be applied in clinical practice and integrated in clinical (multicentre) trials for optimal standardization of the procedurals and interpretations. A major focus is put on procedures using [¹⁸F]-2-fluoro-2-deoxyglucose ([¹⁸F]FDG), but 4Is PET radiopharmaceuticals beyond [¹⁸F]FDG are also described in this summarized document. Whilst these novel tracers are currently mainly applied in early clinical trials, some multicentre trials are underway and we foresee in the near future their use in clinical care and inclusion in the clinical guidelines. Diagnosis and management of 4Is related cardiovascular diseases are generally complex and often require a multidisciplinary approach by a team of experts. The new standards described herein should be applied when using PET/CT and PET/magnetic resonance, within a multimodality imaging framework both in clinical practice and in clinical trials for 4Is cardiovascular indications.

Future Perspectives

Opportunities and challenges in the field of systemic amyloidosis can be grouped into 4 categories. First, a deeper understanding of the pathogenesis of the disease is required. Second, a greater awareness of the disease, which will lead to an earlier diagnosis, is imperative. Third, end points for interventional trials are required to convey us to our fourth aspirations, which are novel therapies for patients with light chain amyloidosis.

Systemic light-chain amyloidosis incidentally diagnosed after subtotal parathyroidectomy and thyroid lobectomy

A 74-year-old woman with a history of primary hyperparathyroidism, thyroid nodules, atrial fibrillation and pacemaker placement for sick sinus syndrome presented with fatigue, constipation and persistent lower extremity oedema. She underwent subtotal parathyroidectomy and left thyroid lobectomy. Histopathology revealed amyloidosis affecting the thyroidand parathyroids confirmed by Congo Red Staining with Mayo Clinic subtyping of light chain kappa-type amyloidosis. She was found to have combined systolic and diastolic cardiac dysfunction, carpal tunnel neuropathy and pre-diabetes suggestive of systemic amyloidosis with involvement of the heart, nerves and pancreas. Congo red stain was positive for amyloidosis on bone marrow biopsy suggestive of a diagnosis of systemic amyloidosis. She was treated with daratumumab with good clinical response. This case illustrates the necessity of considering systemic amyloidosis in patients with incidentally discovered diffuse amyloid deposits on biopsy of an endocrine organ, as endocrine effects are a rare but likely underdiagnosed consequence of systemic amyloidosis.

Chronic Diarrhea as the Presenting Feature of Amyloidosis with Multiple Myeloma: A Case Report Diagnosed by a Myocardial Biopsy

A 73-year-old woman with a history of diarrhea for one year and other various symptoms was admitted to our hospital. Gastrointestinal endoscopy that included enteroscopy with multiple biopsies was performed. However, no significant findings were observed. Electrocardiography showed low voltage in all limb leads, and an echocardiogram showed thickened cardiac walls with granular sparkling pattern. A myocardial biopsy revealed amyloidosis, and a bone marrow biopsy showed multiple myeloma. This case suggests that we should suspect the possibility of amyloidosis in a patient with diarrhea and various symptoms involving multiple organ systems. Additionally, electrocardiograms and echocardiograms should be performed even when gastrointestinal biopsies reveal negative results.

Systemic amyloidosis from A (AA) to T (ATTR): a review

Systemic amyloidosis is a rare protein misfolding and deposition disorder leading to progressive organ failure. There are over 15 types of systemic amyloidosis, each caused by a different precursor protein which promotes amyloid formation and tissue deposition. Amyloidosis can be acquired or hereditary and can affect various organs, including the heart, kidneys, liver, nerves, gastrointestinal tract, lungs, muscles, skin and soft tissues. Symptoms are usually insidious and nonspecific resulting in diagnostic delay. The field of amyloidosis has seen significant improvements over the past decade in diagnostic accuracy, prognosis prediction and management. The advent of mass spectrometry-based shotgun proteomics has revolutionized amyloid typing and has led to the discovery of new amyloid types. Accurate typing of the precursor protein is of paramount importance as the type dictates a specific management approach. In this article, we review each type of systemic amyloidosis to provide the practitioner with practical tools to improve diagnosis and management of these rare disorders.

Potential Cardiovascular Applications of Total-body PET Imaging

Cardiovascular conditions can exist as part of a systemic disorder (eg, sarcoidosis, amyloidosis, or vasculitis) or have systemic consequences as a result of the cardiovascular insult (eg, myocardial infarction). In other circumstances, multisystem evaluation of metabolism and blood flow might be key for evaluation of multisystemic syndromes or conditions. Long axial field-of-view PET/computed tomography systems hold the promise of transforming the investigation of such systemic disorders. This article aims at reviewing some of the potential cardiovascular applications of this novel instrumentation device.

Novel imaging techniques using 18 F-florbetapir PET/MRI can guide fascicular nerve biopsy in amyloid multiple mononeuropathy

BACKGROUND

Multiple mononeuropathy is a rare presentation of primary (AL) amyloidosis and nerve biopsy is usually needed for diagnosis. Conventional imaging is useful to identify proximal nerve involvement but may be inadequate. We report a patient with multiple mononeuropathy whose presentation was suggestive of AL amyloid neuropathy and in whom repeated tissue biopsies were negative for amyloid (including two sensory nerves and one muscle).

METHODS

The patient underwent magnetic resonance imaging (MRI) and whole body ¹⁸ F-florbetapir positron emission tomography (PET)/MRI.

RESULTS

Whole body ¹⁸ F-florbetapir PET/MRI revealed abnormal low-level florbetapir uptake in the right proximal tibial and peroneal nerves, which provided a target for a sciatic bifurcation fascicular nerve biopsy that was diagnostic of AL amyloidosis.

CONCLUSIONS

¹⁸ F-florbetapir PET/MRI imaging is a promising diagnostic tool for patients with suspected peripheral nerve amyloidosis (including multiple mononeuropathy) in whom conventional imaging and nerve and muscle biopsies miss the pathology.

Procedural recommendations of cardiac PET/CT imaging: standardization in inflammatory-, infective-, infiltrative-, and innervation (4Is)-related cardiovascular diseases: a joint collaboration of the EACVI and the EANM

With this document, we provide a standard for PET/(diagnostic) CT imaging procedures in cardiovascular diseases that are inflammatory, infective, infiltrative, or associated with dysfunctional innervation (4Is). This standard should be applied in clinical practice and integrated in clinical (multicenter) trials for optimal procedural standardization. A major focus is put on procedures using [¹⁸F]FDG, but 4Is PET radiopharmaceuticals beyond [¹⁸F]FDG are also described in this document. Whilst these novel tracers are currently mainly applied in early clinical trials, some multicenter trials are underway and we foresee in the near future their use in clinical care and inclusion in the clinical guidelines. Finally, PET/MR applications in 4Is cardiovascular diseases are also briefly described. Diagnosis and management of 4Is-related cardiovascular diseases are generally complex and often require a multidisciplinary approach by a team of experts. The new standards described herein should be applied when using PET/CT and PET/MR, within a multimodality imaging framework both in clinical practice and in clinical trials for 4Is cardiovascular indications.

Multimodality Imaging in the Evaluation and Management of Cardiac Amyloidosis

Systemic amyloidosis is a heterogeneous group of disorders where misfolded proteins deposit in the various organs as nonbranching fibrils with a β-pleated-sheet structure called amyloid. Extensive extracellular deposition of these amyloid fibrils eventually leads to organ dysfunction. Involvement of the heart, termed as cardiac amyloidosis, leads to heart failure if left untreated and carries high morbidity and mortality. Current interest in cardiac amyloidosis is growing rapidly thanks to the recent development of effective targeted treatment options, driving the need for better and earlier detection of the condition, which is largely underdiagnosed and far commoner than recognized. Timely diagnosis of cardiac amyloidosis is challenging, but is poised to improve with emergence of newer noninvasive imaging techniques, potentially obviating the need for endomyocardial biopsy in some patients and providing prognostic information. With recent advances in the therapeutic options for cardiac amyloidosis, an area of immense interest is the adoption of imaging as biomarkers for longitudinal assessment of disease progression and treatment response. In this article, we provide an overview of cardiac amyloidosis, discuss the role of imaging modalities in cardiac amyloidosis, and explore future directions for imaging in cardiac amyloidosis.

Quantitative [18F]florbetapir PET/CT may identify lung involvement in patients with systemic AL amyloidosis

PURPOSE

The clinical diagnosis of pulmonary involvement in individuals with systemic AL amyloidosis remains challenging. [18F]florbetapir imaging has previously identified AL amyloid deposits in the heart and extra-cardiac organs. The aim of this study is to determine quantitative [18F]florbetapir pulmonary kinetics to identify pulmonary involvement in individuals with systemic AL amyloidosis.

METHODS

We prospectively enrolled 58 subjects with biopsy-proven AL amyloidosis and 9 control subjects (5 without amyloidosis and 4 with ATTR cardiac amyloidosis). Pulmonary [18F]florbetapir uptake was evaluated visually and quantified as distribution volume of specific binding (Vs) derived from compartmental analysis and simpler semiquantitative metrics of maximum standardized uptake values (SUVmax), retention index (RI), and target-to-blood ratio (TBR).

RESULTS

On visual analysis, pulmonary tracer uptake was absent in most AL subjects (40/58, 69%); 12% (7/58) of AL subjects demonstrated intense bilateral homogeneous tracer uptake. In this group, compared to the control group, Vs (median Vs 30-fold higher, 9.79 vs. 0.26, p < 0.001), TBR (median TBR 12.0 vs. 1.71, p < 0.001), and RI (median RI 0.310 vs. 0.033, p < 0.001) were substantially higher. Notably, the AL group without visually apparent pulmonary [18F]florbetapir uptake also demonstrated a > 3-fold higher Vs compared to the control group (median 0.99 vs. 0.26, p < 0.001). Vs was independently related to left ventricular SUVmax, a marker of cardiac AL deposition, but not to ejection fraction, a marker of cardiac dysfunction. Also, intense [18F]florbetapir lung uptake was not related to [11C]acetate lung uptake, suggesting that intense [18F]florbetapir lung uptake represents AL amyloidosis rather than heart failure.

CONCLUSIONS

[18F]florbetapir PET/CT offers the potential to noninvasively identify pulmonary AL amyloidosis, and its clinical relevance warrants further study.

Advances in PET-Based Cardiac Amyloid Radiotracers

The gold standard for diagnosis of cardiac amyloidosis (CA) is endomyocardial biopsy showing Congo red staining followed by mass spectroscopy, but the diagnosis can also be made with high certainty by demonstration of typical cardiac imaging features along with amyloid on biopsy of another involved organ. The use of cardiac imaging techniques to detect amyloid deposits may frequently obviate the need for invasive methods in order to ascertain the presence, and potentially the type, of amyloid deposition. PURPOSE OF REVIEW: We aim to review the evidence behind the development of novel positron emission tomography (PET) radiotracers for demonstrating cardiac amyloid deposition and potentially distinguishing between light-chain (AL) or transthyretin (ATTR) cardiac amyloidosis. RECENT FINDINGS: Multiple recent studies have shown that thioflavin-analogue tracers such as¹⁸F-florbetapir, ¹⁸F-florbetaben, ¹⁸F-flutemetamol, and ¹¹C-labeled Pittsburg Compound-B (PiB) may be able to fulfill the unmet need of elucidating the presence of amyloid deposition in the heart. Because they bind to the beta-pleated motif of the amyloid fibril due to their similarity to the thioflavin structure, they could potentially be used to image CA (Table 1). The use of PET amyloid radiotracers shows promise; however, further data is needed to define their overall accuracy and additive value to the care of patients with suspected systemic and/or cardiac amyloidosis.

Diagnosing cardiac amyloidosis in every-day practice: A practical guide for the cardiologist

Cardiac amyloidosis (CA) has emerged as a previously underestimated cause of heart failure and mortality. Underdiagnosis resulted mainly from unawareness of the true disease prevalence and the non-specific symptoms of the disease. CA results from extracellular deposition of misfolded protein fibrils, commonly derived from transthyretin (ATTR) or immunoglobulin light chains (AL). A significant proportion of older patients with heart failure and other extracardiac manifestations suffer from ATTR-CA, whereas AL-CA is still considered a rare disease. This article provides an overview of CA with a special focus on current and emerging diagnostic modalities. Furthermore, we provide a diagnostic algorithm for the evaluation of patients with suspected CA in every-day practice.

The Changing Face of Nuclear Cardiology: Guiding Cardiovascular Care Toward Molecular Medicine

Radionuclide imaging of myocardial perfusion, function, and viability has been established for decades and remains a robust, evidence-based and broadly available means for clinical workup and therapeutic guidance in ischemic heart disease. Yet, powerful alternative modalities have emerged for this purpose, and their growth has resulted in increasing competition. But the potential of the tracer principle goes beyond the assessment of physiology and function, toward the interrogation of biology and molecular pathways. This is a unique selling point of radionuclide imaging, which has been underrecognized in cardiovascular medicine until recently. Now, molecular imaging methods for the detection of myocardial infiltration, device infection, and cardiovascular inflammation are successfully gaining clinical acceptance. This is further strengthened by the symbiotic quest of cardiac imaging and therapy for an increasing implementation of molecule-targeted procedures, in which specific therapeutic interventions require specific diagnostic guidance toward the most suitable candidates. This review will summarize the current advent of clinical cardiovascular molecular imaging and highlight its transformative contribution to the evolution of cardiovascular therapy beyond mechanical interventions and broad blockbuster medication, toward a future of novel, individualized molecule-targeted and molecular imaging-guided therapies.