Molecular imaging of amyloidosis: will the heart be the next target after the brain?

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.

Novel Tracers for the Imaging of Cardiac Amyloidosis

Radionuclide scintigraphy with technetium-labeled bisphosphonates has brought a paradigm shift in diagnosing cardiac amyloidosis (CA), with transthyretin CA now being effectively diagnosed without the need for tissue biopsy. Yet, deficits remain, such as methods for the noninvasive diagnosis of light-chain CA, means to detect CA early, prognostication, monitoring, and therapy response assessment. To address these issues, there has been growing interest in the development and implementation of amyloid-specific radiotracers for PET. The aim of this review is to educate the reader on these novel imaging tracers. Though still investigational, these novel tracers-given their many advantages-are clearly the future of nuclear imaging in CA.

Semi-Quantification of Myocardial Uptake of Bone-Seeking Agents in Suspected Cardiac Amyloidosis

INTRODUCTION

Bone scintigraphy has emerged as a key tool for non-invasive etiologic diagnosis of transthyretin (ATTR) cardiac amyloidosis (CA). We focused on a new semi-quantification method (on planar imaging) that could complement the qualitative/visual Perugini scoring system, especially when SPET/CT is not available.

MATERIAL AND METHODS

We retrospectively/qualitatively evaluated 8674 consecutive, planar 99mTc-biphosphonate scintigraphies (performed for non-cardiac reasons), identifying 68 (0.78%) individuals (mean age 79 ± 7 years, range 62-100 years; female/male ratio 16/52) presenting myocardial uptake. Due to the retrospective nature of the study, no SPET/CT, pathologic or genetic confirmation was obtained. The Perugini scoring system was determined (in patients presenting cardiac uptake) and compared with three newly proposed semi-quantitative indices. We took 349 consecutive bone scintigraphies, qualitatively absent of any cardiac/pulmonary uptake, as "healthy controls" (HC).

RESULTS

The heart-to-thigh ratio (RHT) and lung-to-thigh ratio (RLT) indices were significantly higher in patients than in HCs (p ≤ 0.0001). There were statistically significant differences for RHT in HCs vs. patients with qualitative Perugini scores of 1 or >1 (with p ranging from ≤0.001 to ≤0.0001). ROC curves showed that RHT outperformed the other indices and was more accurate in both male and female groups. Furthermore, in the male population, RHT accurately distinguished HCs and patients with scores of 1 (less likely affected by ATTR) from patients with qualitative scores >1 (more likely affected by ATTR) with an AUC of 99% (sensitivity: 95%; specificity: 97%).

CONCLUSION

The proposed semi-quantitative RHT index can accurately/semi-quantitatively distinguish between HCs and subjects probably affected by CA (Perugini scores from 1 to 3), and could be particularly useful when no SPET/CT data are available (such as in retrospective studies and data mining). Furthermore, RHT can semi-quantitatively predict, with very high accuracy, subjects in the male population more likely to be affected by ATTR. The present study, although using a very large sample, is however retrospective, monocentric, and therefore the generalizability of the results should be proved by an accurate external validation.

ADVANCES IN KNOWLEDGE

The proposed heart-to-thigh ratio (RHT) can distinguish healthy controls and subjects that are probably affected by cardiac amyloidosis in a simple and more reproducible way, as compared to standard qualitative/visual evaluation.

99mTc-Pyrophosphate Retention in Atelectatic Pulmonary Tissues of a Patient With Transthyretin Cardiac Amyloidosis

ABSTRACT

A 61-year-old man was hospitalized for suspected cardiac amyloidosis. 99mTc-Pyrophosphate scintigraphy showed intense radiotracer uptake in the heart compared with the ribs, suggestive of transthyretin cardiac amyloidosis. Subsequent genetic test showed missense mutations in the transthyretin gene, which confirmed the diagnosis. Incidentally, a regional radiotracer uptake was seen in the bilateral lungs, respectively, corresponding to areas of atelectasis on the localizing CT of the SPECT/CT. Attention should be paid to radiotracer retention in lung atelectasis as it influences the H/CL (heart-to-contralateral lung) ratio calculation and may hinder the diagnosis of cardiac amyloidosis based on the quantitative H/CL ratio.

Cardiac Transthyretin Amyloidosis: A Nuclear Medicine Leading Role. Situation in a Spanish Center and "State of the Art" in Nuclear Medicine

PURPOSE

Amyloidosis is a heterogeneous group of diseases caused by abnormal extracellular deposition of insoluble proteins and can involve myocardium. One of the causes of myocardial involvement is TTR amyloidosis. Our objective has been to evaluate the situation of cardiac amyloidosis (CA) in our center and the role of nuclear medicine, and to review the state of the art of nuclear medicine in this entity.

PATIENTS AND METHODS

We have evaluated retrospectively 186 patients with clinical suspicion of CA and analyzed the clinical characteristics, free light chains and immunofixation in serum and/or urine, and the most relevant biomarkers associated with transthyretin CA (C-ATTR) of these patients and compared them with the results of the 99mTc-DPD scintigraphy.

RESULTS

We have verified the growing bibliographic evidence concerning C-ATTR. A total of 51 scintigraphies (27.4%) were positive, 2 (1.1%) indeterminate and 133 (71.5%) negative according to the Perugini score. ATTR was diagnosed in 22 (11.8%; 77.3% males; mean age, 79.4 years). Of these, 12 (75% men; 82.3 years) were ATTRwt (wild-type or age-associated) patients, 2 (50% men; 52 years) experienced ATTRv (variant or hereditary), and 8 (87.5% men; 82.3 years) were not classified because of the absence genetic test. The origin of amyloidosis could not be determined in 31 (16.7%; 80.7% males; 84.5 years). In 29 of them (93.6%), it was because there was no study of free light chains or immunofixation.

CONCLUSIONS

Nuclear medicine is playing an increasing role in the diagnosis and classification of CA. However, the monitoring of these is still patchy.

Nuclear Imaging for Cardiac Amyloidosis: Bone Scan, SPECT/CT, and Amyloid-Targeting PET

Cardiac amyloidosis (CA) is a type of systemic amyloidosis, in which abnormal amyloid fibril is deposited in extracellular space of myocardium. Most common subtypes of CA are amyloidosis of immunoglobulin light chain (AL) and amyloidosis of transthyretin (ATTR). With increase in incidence of CA and development of new drugs, the needs of early and accurate diagnosis of CA are increasing. In CA, bone scan and SPECT/CT have long been used for diagnosis. Currently, bone scan is included in almost all practice guidelines as one of key diagnostic examinations for ATTR CA. In some specific scenarios, bone scan can be used as even a substitute for endomyocardial biopsy. Recently, amyloid-targeting PET that is used for Alzheimer dementia has also been attempted as an imaging method for CA. Although the study results are still insufficient, amyloid-targeting has shown promising potential as an imaging method for CA, particularly in AL. Here, imaging method and clinical application and implication of bone scan, SPECT/CT, and amyloid-targeting PET/CT in CA are reviewed.

Multi-Modality Imaging in Dilated Cardiomyopathy: With a Focus on the Role of Cardiac Magnetic Resonance

Heart failure (HF) is recognized as a leading cause of morbidity and mortality worldwide. Dilated cardiomyopathy (DCM) is a common phenotype in patients presenting with HF. Timely diagnosis, appropriate identification of the underlying cause, individualized risk stratification, and prediction of clinical response to treatment have improved the prognosis of DCM over the last few decades. In this article, we reviewed the current evidence on available imaging techniques used for DCM patients. In this direction, we evaluated appropriate scenarios for the implementation of echocardiography, nuclear imaging, and cardiac computed tomography, and we focused on the primordial role that cardiac magnetic resonance (CMR) holds in the diagnosis, prognosis, and tailoring of therapeutic options in this population of special clinical interest. We explored the predictive value of CMR toward left ventricular reverse remodeling and prediction of sudden cardiac death, thus guiding the decisions for device therapy. Principles underpinning the use of state-of-the-art CMR techniques such as parametric mapping and feature-tracking strain analysis are also provided, along with expectations for the anticipated future advances in this field. We also attempted to correlate the evidence with clinical practice, with the intent to address questions on selecting the optimal imaging method for different indications and clinical needs. Overall, we recommend a comprehensive assessment of DCM patients at baseline and at follow-up intervals depending on the clinical status, with the addition of CMR as a second-line modality to other imaging techniques. We also provide an algorithm to guide the detailed imaging approach of the patient with DCM. We expect that future guidelines will upgrade their clinical recommendations for the utilization of CMR in DCM, which is expected to further improve the quality of care and the outcomes. This review provides an up-to-date perspective on the imaging of dilated cardiomyopathy patients and will be of clinical value to training doctors and physicians involved in the area of heart failure.

Immunoglobulin light chain amyloidosis: 2020 update on diagnosis, prognosis, and treatment

DISEASE OVERVIEW

Immunoglobulin light chain amyloidosis is a clonal, nonproliferative plasma cell disorder in which fragments of immunoglobulin light or heavy chain are deposited in tissues. Clinical features depend on organs involved but can include heart failure with preserved ejection fraction, nephrotic syndrome, hepatic dysfunction, peripheral/autonomic neuropathy, and "atypical smoldering multiple myeloma or monoclonal gammopathy undetermined significance (MGUS)."

DIAGNOSIS

Tissue biopsy stained with Congo red demonstrating amyloid deposits with apple-green birefringence is required for diagnosis. Invasive organ biopsy is not required in 85% of patients. Verification that amyloid is composed of immunoglobulin light chains is mandatory. The gold standard is laser capture mass spectroscopy.

PROGNOSIS

N-terminal pro-brain natriuretic peptide (NT-proBNP), serum troponin T, and difference between involved and uninvolved immunoglobulin free light chain (FLC) values are used to classify patients into four groups of similar size; median survivals are 94.1, 40.3, 14.0, and 5.8 months.

THERAPY

All patients with a systemic amyloid syndrome require therapy to prevent deposition of amyloid in other organs and prevent progressive organ failure. Stem cell transplant (SCT) is preferred, but only 20% of patients are eligible. Requirements for safe SCT include systolic blood pressure >90 mmHg, troponin T < 0.06 ng/mL and serum creatinine ≤1.7 mg/dL. Nontransplant candidates can be offered cyclophosphamide-bortezomib-dexamethasone or daratumumab-containing regimens as it appears to be highly active in AL amyloidosis.

FUTURE CHALLENGES

Delayed diagnosis remains a major obstacle to initiating effective therapy prior to the development of end-stage organ failure.

Multi-modality imaging of cardiac amyloidosis: Contemporary update

Cardiac amyloidosis is a heterogeneous and challenging diagnostic disease with poor prognosis that is now being altered by introduction of new therapies. Echocardiography remains the first-line imaging tool, and when disease is suspected on echocardiography, cardiac magnetic resonance imaging and nuclear imaging play critical roles in the non-invasive diagnosis and evaluation of cardiac amyloidosis. Advances in multi-modality cardiac imaging allowing earlier diagnosis and initiation of novel therapies have significantly improved the outcomes in these patients. Cardiac imaging also plays important roles in the risk stratification of patients presenting with cardiac amyloidosis. In the current review, we provide a clinical and imaging focused update, and importantly outline the imaging protocols, diagnostic and prognostic utility of multimodality cardiac imaging in the assessment of cardiac amyloidosis.

Positive Myocardial Uptake of Bone Scintigraphic Agents Associated with Cardiac Amyloidosis: Frequency of Positive Uptake Data Based on Daily Clinical Practice

Objective: The bone scan plays an important role for detecting number of conditions relating to bones, including: bone cancer or bone metastasis, bone inflammation. Extraosseous uptake, in particular, myocardial uptake, was observed in some patients examined with the bone scans. Positive uptake of ^99mTc-labeled bone radiotracers is associated with cardiac amyloidosis. However, the frequency and cause of positive cardiac ^99mTc-MDP uptake have not been fully studied. In this regard, the aim of this study was to assess the frequency and characteristics of patients with high myocardi-al uptake of bone scintigraphy in daily clinical practice setting. Methods: We retrospectively analyzed 4180 bone scintigraphies performed in daily clinical practice during 7-years period. The intensity of the myocardial uptake was graded based on a visual scale ranging from 0 to 3 points. Score 0 indicates the absence of uptake. Score 1 defined uptake less than that of bone (referred to as the adjacent rib). Uptake similar to that of bone was classified score 2. Score 3 was defined as uptake greater than that of reference bone. Positive myocardial uptake included a visual score 2 or 3. Result: Positive ^99mTc-MDP myocardial uptake occurred in 12 patients among 4180 patients (0.3%). 7 of 12 positive scan patients were consistent with amyloidosis confirmed by biopsy. In these patients, the mean age was 75.6 ± 5.2 years old. Ten cases showed biventricular uptake and 2 showed LV uptake only. Conclusion: Positive cardiac uptake of bone scintigraphic agents was present in 0.3% of bone scintigraphies in a clinical practice setting. This may be a sign of cardiac amyloidosis involvement which may give the presence of extraosseous bone tracer uptake its own importance and a new role.

Amyloid PET imaging in cardiac amyloidosis: a pilot study using 18F-flutemetamol positron emission tomography

OBJECTIVE

Cardiac amyloidosis is a rare disease characterized by amyloid heart deposits and is usually a part of systemic amyloidosis, in relation to systemic light chain (AL) and transthyretin (ATTR wild-type or genetic) amyloidosis. Several recent studies suggest a promising role of amyloid PET imaging to image cardiac amyloidosis, and several PET tracers are now available for in vivo detection of amyloid deposits. The aim of this study was to evaluate ¹⁸F-flutemetamol in diagnosing cardiac amyloidosis.

METHODS

We performed a pilot study using ¹⁸F-flutemetamol (Vizamyl™) in 12 patients, 3 control subjects without cardiac amyloidosis, and 9 subjects with documented cardiac amyloidosis. Mean standardized uptake value (SUV) in the left ventricular myocardium and blood pool was determined and semi-quantitative parameter as target to background ratio (TBR, myocardial/blood pool mean SUV ratio) between 10th and 30th minutes was calculated.

RESULTS

Uptake of ¹⁸F-flutemetamol in the left ventricular myocardium was noted in all patients with cardiac amyloidosis except one and none in control patient. The TBR was significantly higher in amyloidosis patients than in control subjects: 1.46, interquartile range (IQR) 1.32-2.06 versus 1.06, IQR 0.72-1.1 (p = 0.033). Only one patient in our study had light chain amyloidosis and showed higher TBR than patients with transthyretin amyloid: TBR 3.0 versus TBR median 1.44, IQR 1.33-1.69.

CONCLUSION

Amyloid PET tracers such as ¹⁸F-flutemetamol could be a promising tool in diagnosing and in therapy response assessment for patients with cardiac amyloidosis.

The Cardiorenal Axis: Myocardial Perfusion, Metabolism, and Innervation

PURPOSE OF THE REVIEW

Cardiorenal syndrome (CRS), defined as concomitant heart and kidney disease, has been a focus of attention for nearly a decade. As more patients survive severe acute and chronic heart and kidney diseases, CRS has emerged as an "epidemic" of modern medicine. Significant advances have been made in unraveling the complex mechanisms that underlie CRS based on classification of the condition into five pathophysiologic subtypes. In types 1 and 2, acute or chronic heart disease results in renal dysfunction, while in types 3 and 4, acute or chronic kidney diseases are the inciting factors for heart disease. Type 5 CRS is defined as concomitant heart and kidney dysfunction as part of a systemic condition such as sepsis or autoimmune disease.

RECENT FINDINGS

There are ongoing efforts to better define subtypes of CRS based on historical information, clinical manifestations, laboratory data (including biomarkers), and imaging characteristics. Systematic evaluation of CRS by advanced cardiac imaging, however, has been limited in scope and mostly focused on type 4 CRS. This is in part related to lack of clinical trials applying advanced cardiac imaging in the acute setting and exclusion of patients with significant renal disease from studies of such techniques in chronic HF. Advanced cardiac nuclear imaging is well poised for assessment of the pathophysiology of CRS by offering a myriad of molecular probes without the need for nephrotoxic contrast agents. In this review, we examine the current or potential future application of advanced cardiac imaging to evaluation of myocardial perfusion, metabolism, and innervation in patients with CRS.

Immunoglobulin light chain amyloidosis: 2018 Update on diagnosis, prognosis, and treatment

DISEASE OVERVIEW

Immunoglobulin light chain amyloidosis is a clonal, nonproliferative plasma cell disorder in which fragments of immunoglobulin light or heavy chain are deposited in tissues. Clinical features depend on organs involved but can include restrictive cardiomyopathy, nephrotic syndrome, hepatic dysfunction, peripheral/autonomic neuropathy, and "atypical multiple myeloma."

DIAGNOSIS

Tissue biopsy stained with Congo red demonstrating amyloid deposits with apple-green birefringence is required for diagnosis. Invasive organ biopsy is not required because amyloid deposits can be found in bone marrow, salivary gland, or subcutaneous fat aspirate in 85% of patients. Verification that amyloid is composed of immunoglobulin light chains is mandatory. The gold standard is laser capture mass spectroscopy.

PROGNOSIS

N-terminal pro-brain natriuretic peptide (NT-proBNP), serum troponin T, and difference between involved and uninvolved immunoglobulin free light chain values are used to classify patients into four groups of similar size; median survivals are 94.1, 40.3, 14.0, and 5.8 months.

THERAPY

All patients with a systemic amyloid syndrome require therapy to prevent deposition of amyloid in other organs and prevent progressive organ failure. Stem cell transplant (SCT) is preferred, but only 20% of patients are eligible. Requirements for safe SCT include systolic blood pressure >90 mm Hg, troponin T < 0.06 ng/mL, age < 70 years, and serum creatinine ≤1.7 mg/dL. Nontransplant candidates can be offered melphalan-dexamethasone or cyclophosphamide-bortezomib-dexamethasone. Daratumumab appears to be highly active in AL amyloidosis. Antibodies designed to dissolve existing amyloid deposits are under study.

FUTURE CHALLENGES

Delayed diagnosis remains a major obstacle to initiating effective therapy.

EDUCATIONAL OBJECTIVES

Upon completion of this educational activity, participants will be better able to: Master recognition of clinical presentations that should raise suspicion of amyloidosis. Understand simple techniques for confirming the diagnosis and providing material to classify the protein subunit. Recognize that a tissue diagnosis of amyloidosis does not indicate whether the amyloid is systemic or of immunoglobulin light chain origin. Understand the roles of the newly introduced chemotherapeutic and investigational antibody regimens for the therapy of light chain amyloidosis.

The Potential of Clinical Phenotyping of Heart Failure With Imaging Biomarkers for Guiding Therapies: A Focused Update

The need for noninvasive assessment of cardiac volumes and ejection fraction (EF) ushered in the use of cardiac imaging techniques in heart failure (HF) trials that investigated the roles of pharmacological and device-based therapies. However, in contrast to HF with reduced EF (HFrEF), modern HF pharmacotherapy has not improved outcomes in HF with preserved EF (HFpEF), largely attributed to patient heterogeneity and incomplete understanding of pathophysiological insights underlying the clinical presentations of HFpEF. Modern cardiac imaging methods offer insights into many sets of changes in cardiac tissue structure and function that can precisely link cause with cardiac remodeling at organ and tissue levels to clinical presentations in HF. This has inspired investigators to seek a more comprehensive understanding of HF presentations using imaging techniques. This article summarizes the available evidence regarding the role of cardiac imaging in HF. Furthermore, we discuss the value of cardiac imaging techniques in identifying HF patient subtypes who share similar causes and mechanistic pathways that can be targeted using specific HF therapies.

Standardization of 99mTechnetium pyrophosphate imaging methodology to diagnose TTR cardiac amyloidosis

BACKGROUND

Technetium pyrophosphate (99mTc-PYP) imaging to diagnose transthyretin cardiac amyloidosis (ATTR-CA) has been increasingly utilized. The objective of this study is to provide a standardized 99mTc-PYP imaging protocol to diagnose ATTR-CA.

METHODS

104 scans from 45 subjects with biopsy-proven ATTR-CA or light-chain cardiac amyloidosis (AL) were assessed. Multiple scans were obtained using different counts (750 vs 2000 K), times to acquisition (1 vs 2 to 4 hours), processing matrix (256 vs 128), and 99mTc-PYP dose. Image quality and extracardiac activity was assessed. Quantitative methods using heart-to-contralateral ratios (H/CL) and a visual semiquantitative scale were used to diagnose ATTR-CA.19 The correlation between H/CL ratios and reproducibility of semiquantitative visual scores, acquired using various imaging parameters, were evaluated.

RESULTS

All imaging parameters had good to excellent image quality. 750 vs 2000 K counts, 1 hour acquisition and 256 matrix, had lower extracardiac activity (P = .00018). 10 mCi of 99mTc-PYP v. higher doses showed excellent image quality and less extracardiac activity (P = .0015). Correlation of H/CL ratios was strong (r ≥ 0.92) and reproducibility of semiquantitative visual scores was high (Kappa = 95%).

CONCLUSION

An imaging protocol using 750 K counts, 10 mCi of 99mTc-PYP, and a 256 matrix was chosen as the standardized imaging protocol since it provided the shortest overall study time (1 vs 2 to 4 hours) and lowest radiation exposure (3 vs 8 to 10 mSv).

Evaluation of the effect of D-amino acid incorporation into amyloid-reactive peptides

BACKGROUND

Systemic amyloidoses comprise diseases characterized by the deposition of proteinaceous material known as amyloid. Currently, without performing multiple biopsies, there is no way to ascertain the extent of amyloid deposition in patients-a critical piece of information that informs prognosis and therapeutic strategies. We have developed pan-amyloid-targeting peptides for imaging amyloid and recently have adapted these for use as pre-targeting agents in conjunction with immunotherapy. Incorporation of D-amino acids in these peptides may enhance serum half-life, which is an important characteristic of effective peptide therapeutics. Herein, we assess the effects of partial incorporation of D-amino acids into the amyloidophilic peptide p5 on in vivo amyloid reactivity.

METHODS

Peptides, referred to as ^AQAp5 _(d) , ^aqap5, and ^AQAp5, were radiolabeled with iodine-125 and the tissue biodistribution (% injected dose/gram) measured in healthy mice at multiple time points post-injection. Microscopic distribution of the peptides was further visualized using microautoradiography (ARG). Peptides ^aqap5 and ^AQAp5 were injected into healthy and amyloid-laden mice and evaluated by using SPECT/CT imaging at 1, 4 and 24 h post injection.

RESULTS

Biodistribution data and ARG revealed persistent retention of [¹²⁵I]^AQAp5 _(d) in the liver and kidneys of healthy mice for at least 24 h. In contrast, peptides [¹²⁵I]^aqap5 and [¹²⁵I]^AQAp5 did not bind these organs and was significantly lower than [¹²⁵I]^AQAp5 _(d) at 24 h post injection (p < 0.0001). SPECT/CT imaging of amyloid-laden mice revealed accumulation of both [¹²⁵I]^aqap5 and [¹²⁵I]^AQAp5 in amyloid-affected organs; whereas, in healthy mice, [¹²⁵I]^aqap5 was observed in the kidneys and liver at early time points, and free radioiodide liberated during catabolism of [¹²⁵I]^AQAp5 was seen in the stomach and thyroid. Autoradiography confirmed that both [¹²⁵I]^aqap5 and [¹²⁵I]^AQAp5 peptides specifically bound amyloid with no off-target binding to healthy organs.

CONCLUSION

Incorporation of D-amino acids in amyloid-binding regions of amyloidophilic peptides resulted in off-target binding; however, N-terminus placement retained amyloid-specificity and evasion of deiodinases. Peptide ^aqap5, or similar reagents, may prove useful in novel immunotherapy strategies as well as for imaging renal, gastric and pancreatic amyloidosis.

Role of Imaging in Evaluating Infiltrative Heart Disease

OPINION STATEMENT

Infiltrative heart disease is caused by the deposition of abnormal substances in the heart and can lead to abnormalities in cardiac function and electrical conduction. Advances in non-invasive cardiovascular imaging have allowed for improved diagnosis of infiltrative heart disease, as well as ways to track disease progression or regression, thus enabling a mechanism to follow response to therapy. In this review, we provide an overview of the role of imaging in the diagnosis and management of cardiac sarcoidosis (CS) and cardiac amyloidosis (CA), as well as outline a proposed algorithm for using non-invasive cardiovascular imaging for evaluating these conditions.

18F-Florbetaben: A New Tool for Amyloidosis Staging?

We report the case of a 73-year-old man with a documented (renal biopsy) light-chain amyloidosis (AL) imaged with F-AV-1 (F-florbetaben) compared with a volunteer. A cardiac amyloidosis was suspected. As it was an AL and not a transthyretin amyloidosis, F-FDG and F-florbetaben PET/CT were preferred to bone scan. F-FDG scintigraphy showed a focal cardiac hypermetabolism. In addition of the heart, F-florbetaben scintigraphy showed an intense spleen and thyroid pathologic uptake and a moderate salivary gland and kidney uptake. F-florbetaben PET/CT appears to be useful for staging systemic amyloidosis.

Dual-Energy SPECT and the Development of Peptide p5+14 for Imaging Amyloidosis

Amyloidosis is associated with a number of rare diseases and is characterized by the deposition, in abdominothoracic organs and peripheral nerves, of extracellular protein fibrils, which leads to dysfunction and severe morbidity. Effective clinical evaluation and management of patients with systemic amyloidosis are hampered by the lack of a noninvasive, quantitative method for detecting whole-body amyloid load. We have used a battery of assays including dual-energy SPECT imaging and comparative effectiveness studies in support of translation of a synthetic polybasic peptide, p5+14, as a novel radiotracer for visualization of amyloidosis by molecular imaging. These data provide support for a phase 1 positron emission tomography/computed tomography imaging trial of this reagent, labeled with iodine-124, in patients with all forms of systemic amyloidosis.

Clinical Utility and Future Applications of PET/CT and PET/CMR in Cardiology

Over the past several years, there have been major advances in cardiovascular positron emission tomography (PET) in combination with either computed tomography (CT) or, more recently, cardiovascular magnetic resonance (CMR). These multi-modality approaches have significant potential to leverage the strengths of each modality to improve the characterization of a variety of cardiovascular diseases and to predict clinical outcomes. This review will discuss current developments and potential future uses of PET/CT and PET/CMR for cardiovascular applications, which promise to add significant incremental benefits to the data provided by each modality alone.

Immunoglobulin light chain amyloidosis: 2016 update on diagnosis, prognosis, and treatment

DISEASE OVERVIEW

Immunoglobulin light chain amyloidosis is a clonal, nonproliferative plasma cell disorder in which fragments of immunoglobulin light chain are deposited in tissues. Clinical features depend on organs involved but can include restrictive cardiomyopathy, nephrotic syndrome, hepatic failure, peripheral/autonomic neuropathy, and atypical multiple myeloma.

DIAGNOSIS

Tissue biopsy stained with Congo red demonstrating amyloid deposits with applegreen birefringence is required for diagnosis. Invasive organ biopsy is not required because amyloid deposits can be found in bone marrow biopsy or subcutaneous fat aspirate in 85% of patients. Verification that amyloid is composed of immunoglobulin light chains is mandatory.

PROGNOSIS

N-terminal pro-brain natriuretic peptide (NTproBNP), serum troponin T, and difference between involved and uninvolved immunoglobulin free light chain values are used to classify patients into four groups of similar size; median survivals are 94.1, 40.3, 14.0, and 5.8 months.

THERAPY

All patients with a systemic amyloid syndrome require therapy to prevent deposition of amyloid in other organs and prevent progressive organ failure of involved sites. Stem cell transplant (SCT) is preferred, but only 20% of patients are eligible. Requirements for safe SCT include systolic blood pressure >90 mmHg, troponin T <0.06 ng mL21, age <70 years, and serum creatinine 1.7 mg dL21. Nontransplant candidates can be offered melphalan-dexamethasone or cyclophosphamide-bortezomib-dexamethasone. Other combinations of chemotherapy with agents such as cyclophosphamide-thalidomide (or lenalidomide)-dexamethasone, bortezomib-dexamethasone, and melphalan-prednisone-lenalidomide have documented activity. Antibodies designed to dissolve existing amyloid deposits are under study for previously treated and untreated patients. Late diagnosis remains a major obstacle to initiating effective therapy. Am. J. Hematol., 2016. © 2016 Wiley Periodicals, Inc. Am. J. Hematol. 91:948-956, 2016. © 2016 Wiley Periodicals, Inc.

Systemic amyloidosis

Tissue deposition of protein fibrils causes a group of rare diseases called systemic amyloidoses. This Seminar focuses on changes in their epidemiology, the current approach to diagnosis, and advances in treatment. Systemic light chain (AL) amyloidosis is the most common of these conditions, but wild-type transthyretin cardiac amyloidosis (ATTRwt) is increasingly being diagnosed. Typing of amyloid fibrils, a critical determinant of therapy, has improved with the wide availability of laser capture and mass spectrometry from fixed histological tissue sections. Specific and accurate evaluation of cardiac amyloidosis is now possible using cardiac magnetic resonance imaging and cardiac repurposing of bone scintigraphy tracers. Survival in AL amyloidosis has improved markedly as novel chemotherapy agents have become available, but challenges remain in advanced disease. Early diagnosis, a key to better outcomes, still remains elusive. Broadening the amyloid-specific therapeutic landscape to include RNA inhibitors, fibril formation stabilisers and inhibitors, and immunotherapeutic targeting of amyloid deposits holds promise to transform outcomes in systemic amyloidoses.

Amyloid Proteins and Their Role in Multiple Sclerosis. Considerations in the Use of Amyloid-PET Imaging

Thioflavin T derivatives are used in positron-emission tomography (PET) studies to detect amyloid protein deposits in patients with Alzheimer disease. These tracers bind extensively to white matter, which suggests that they may be useful in studies of multiple sclerosis (MS), and that proteins resulting from proteolytic processing of the amyloid precursor protein (APP) may contribute to MS. This article reviews data from both clinical and preclinical studies addressing the role of these proteins, whether they are detected in CSF studies or using PET imaging. APP is widely expressed in demyelinated axons and may have a protective effect in MS and in experimental allergic encephalomyelitis in animals. Several mechanisms associated with this increased expression may affect the degree of remyelination in MS. Amyloid-PET imaging may help determine the degree of demyelination and provide information on the molecular changes linked to APP proteolytic processing experienced by patients with MS.

Shoulder pad sign and asymptomatic hypercalcemia in a patient with end-stage kidney disease

Interpreting an abnormal serum calcium level in subjects with chronic kidney disease (CKD) requires the simultaneous evaluation of various clinical and laboratory parameters. An excessive intake of calcium salts and vitamin D overdosing may be the most common etiologies of hypercalcemia in individuals with advanced CKD. Nevertheless, it should be noted that such patients are susceptible to all diseases that may cause hypercalcemia in subjects without renal disease. In this report, we describe the case of a male chronic hemodialysis patient who developed asymptomatic hypercalcemia associated with polyarticular swelling. On the basis of the findings of systemic workup, he was finally diagnosed as having multiple myeloma. The so-called shoulder pad sign, which is pathognomonic for light chain amyloidosis, although its detection remains a challenge for physicians, was a clue leading to the prompt diagnosis of the disease in the current case. The impact of articular manifestations on the diagnostic strategy for assessing multiple myeloma is also discussed.

Amyloid PET imaging: applications beyond Alzheimer's disease

As a biomarker of beta-amyloid, positron emission tomography (PET) amyloid imaging offers a unique opportunity to detect the presence of this protein in the human body during life. Besides Alzheimer's disease (AD), deposits of beta-amyloid in the brain are also present in other neurodegenerative diseases associated to dementia, such as Parkinson's disease and dementia with Lewy bodies, as well as in other processes affecting brain function, such as cerebral amyloid angiopathy, brain trauma, Down's syndrome and meningiomas, as shown by post-mortem pathology studies. Furthermore, in systemic amyloidosis other organs besides the brain are affected, and amyloid PET imaging may be suitable for the identification of these extra-cerebral amyloid depositions. Finally, the potential use of amyloid PET tracer accumulation in cerebral white matter (WM) as a marker of myelin is being investigated, leading to some promising results in patients with WM lesions and multiple sclerosis. In this article, a review of the ongoing research pointing to a broader application of amyloid PET imaging in clinical practice beyond AD is provided.

Immunoglobulin light chain amyloidosis: 2014 update on diagnosis, prognosis, and treatment

DISEASE OVERVIEW

Immunoglobulin light chain amyloidosis is a clonal, nonproliferative plasma cell disorder in which fragments of immunoglobulin light chain are deposited in tissues. Clinical features depend on organs involved but can include restrictive cardiomyopathy, nephrotic syndrome, hepatic failure, peripheral/autonomic neuropathy, and atypical multiple myeloma.

DIAGNOSIS

Tissue biopsy stained with Congo red demonstrating amyloid deposits with apple-green birefringence is required for diagnosis. Invasive organ biopsy is not required because amyloid deposits can be found in bone marrow biopsy or subcutaneous fat aspirate in 85% of patients. Verification that amyloid is composed of immunoglobulin light chains is mandatory.

PROGNOSIS

N-terminal pro-brain natriuretic peptide (NT-proBNP), serum troponin T, and difference between involved and uninvolved immunoglobulin free light chain values are used to classify patients into four groups of similar size; median survivals are 94.1, 40.3, 14.0, and 5.8 months.

THERAPY

All patients with a systemic amyloid syndrome require therapy to prevent deposition of amyloid in other organs and prevent progressive organ failure of involved sites. Stem cell transplant (SCT) is preferred, but only 20% of patients are eligible. Requirements for safe SCT include NT-proBNP <5,000 ng/mL, troponin T <0.06 ng/mL, age <70 years, <3 organs involved, and serum creatinine ≤1.7 mg/dL. Nontransplant candidates can be offered melphalan-dexamethasone or cyclophosphamide-bortezomib-dexamethasone. Other combinations of chemotherapy with agents such as cyclophosphamide-thalidomide (or lenalidomide)-dexamethasone, bortezomib-dexamethasone, and melphalan-prednisone-lenalidomide have documented activity. Future Challenges: Late diagnosis remains a major obstacle to initiating effective therapy. Recognizing the presenting syndromes is necessary for improving survival.

The toxicity mechanisms of action of Aβ25-35 in isolated rat cardiac myocytes

β-Amyloid (Aβ) is deposited in neurons and vascular cells of the brain and is characterized as a pathologic feature of Alzheimer's disease (AD). Recently studies have reported that there is an association between cardiovascular risk factors and AD, however the mechanism of this association is still uncertain. In this study we observed Aβ had an effect on cardiovascular cells. We represent as a major discovery that Aβ25-35 had toxicity on isolated rat cardiac myocytes by impacting the cytoskeleton assembly and causing ER stress, ultimately contributing to the apoptosis of the myocytes. Importantly, the activation of ER stress and subsequent cellular dysfunction and apoptosis by Aβ25-35 was regulated by the MAPK pathway, which could be prevented by inhibition of p38 via pharmacological inhibitors. It was noteworthy that Aβ25-35 played a critical role in cardiac myocytes, suggesting that Alzheimer's disease (AD) had a relation with the heart and understanding of these associations in future will help search for effective treatment strategies.

Isolated heart transplantation for familial transthyretin (TTR) V122I cardiac amyloidosis

Transthyretin (TTR) cardiac amyloidosis is characterized by deposition of either mutant or wild type TTR amyloid protein in the myocardium ultimately leading to progressive cardiomyopathy and heart failure. The most common TTR gene mutation that leads to TTR cardiac amyloidosis is the valine-to-isoleucine substitution at position 122 (V122I or Ile122). Currently, the only definitive treatment suggested for mutant TTR cardiac amyloidosis is the combined or sequential liver-heart transplantation in eligible patients, since liver is the source of TTR production. Here, we report a case of heterozygous Val122L mutated TTR-related cardiac amyloidosis treated with isolated heart transplantation with no recurrence of amyloid in the cardiac allograft and no systemic abnormalities 5 years after heart transplantation. Abbreviations MMF mycophenolate mofetil NYHA New York Heart Association TTR transthyretin VE minute ventilation.

Novel styrylbenzene derivatives for detecting amyloid deposits

BACKGROUND

Various styrylbenzene compounds were synthesized and evaluated as mainly Aβ amyloid sensors. These compounds, however, cannot be used for detecting amyloid deposition in peripheral nerves because of the inherent sensitivity of the compounds. These compounds often generate false positives especially in the basement membrane of blood vessels in histochemical studies. To overcome these problems, we must first synthesize other styryl compounds for detecting amyloid fibrils in tissues.

METHODS

A wide variety of symmetrical and unsymmetrical styrylbenzene derivatives were synthesized and then these compounds were used to detect amyloid fibrils in autopsy and biopsy samples from patients with various systemic and localized forms of amyloidosis such as familial amyloidotic polyneuropathy (FAP), senile systemic amyloidosis (SSA), amyloid A (AA) amyloidosis, localized AL amyloidosis, and Alzheimer's disease.

RESULTS

1-Methoxy-2,5-bis-styrylbenzene and 2-(2-(2-fluoroethoxy)ethoxy)ethoxy)-2,5-bis-styrylbenzene (EEEFSB) detected amyloid fibrils in both in vitro and in vivo histopathological studies. 1-Methoxy-2,5-bis-styrylbenzene also showed a high strength of fluorescence with amyloid deposition in peripheral nerves in a patient with FAP.

CONCLUSIONS

1-Methoxy-2,5-bis-styrylbenzene and EEEFSB may prove a useful tool for diagnosing amyloidosis, not only in a histochemical study but also in whole body amyloid positron emission tomography (PET) imaging.

Diffuse Hepatic and Spleen Uptake of Tc-99m MDP on Bone Scintigraphy Resembling Liver-Spleen Scintigraphy in a Patient of Plasma Cell Tumor

The present case demonstrates a diffuse intense hepatic and, to a lesser degree, spleen, Tc-99m MDP uptake on a routine bone scintigraphy resembling liver-spleen imaging. A 49-year-old female with a history of anaplastic plasma cell tumor and suffering from bone pain was referred for bone scintigraphy to evaluate possible bone metastases. The bone scintigraphy showed diffuse hepatic and spleen uptake of Tc-99m MDP resembling liver-spleen imaging. Furthermore, bone uptake of Tc-99m MDP was significantly diminished and there were no abnormal foci throughout the skeleton. The bone scintigraphy of the present case of an anaplastic plasma cell tumor suggests the possible presence of amyloidosis.

Role of imaging in the diagnosis and management of patients with cardiac amyloidosis: state of the art review and focus on emerging nuclear techniques

Amyloidosis is an infiltrative disease characterized by deposition of amyloid fibrils within the extracellular tissue of one or multiple organs. Involvement of the heart, cardiac amyloidosis, is recognized as a common cause of restrictive cardiomyopathy and heart failure. The two major types of cardiac amyloidosis are cardiac amyloid light-chain (AL) and transthyretin-related cardiac amyloidosis (ATTR, mutant and wild types) (Nat Rev Cardiol 2010;7:398-408). While early recognition of cardiac amyloidosis is of major clinical importance, so is the ability to differentiate between subtypes. Indeed, both prognosis and therapeutic options vary drastically depending on the subtype. While endomyocardial biopsy with immunostaining is considered the gold standard, advances in imaging provide an attractive non-invasive alternative. Currently, electrocardiography, echocardiography, and cardiac magnetic resonance imaging are all used in the evaluation of cardiac amyloidosis with varying diagnostic and prognostic accuracy. Yet, none of these modalities can effectively differentiate the cardiac amyloid subtypes. Recent data with (99m)Tc-phosphate derivatives, previously used as bone seeking radioactive tracers, have shown promising results; these radiotracers selectively bind ATTR, but not AL subtype, and can differentiate subtypes with high diagnostic accuracy. This review will initially present the non-radionuclide imaging techniques and then focus on the radionuclide imaging techniques, particularly (99m)Tc-DPD and (99m)Tc-PYP, mechanism of action, performance and interpretation of the study, diagnostic accuracy, prognostic value, future clinical perspective, and outlook.

Immunoglobulin light chain amyloidosis: 2013 update on diagnosis, prognosis, and treatment

DISEASE OVERVIEW

Immunoglobulin (Ig) light chain amyloidosis is a clonal, nonproliferative plasma cell disorder in which fragments of Ig light chain are deposited in tissues. Clinical features depend on organs involved but can include restrictive cardiomyopathy, nephrotic syndrome, hepatic failure, peripheral/autonomic neuropathy, and atypical multiple myeloma.

DIAGNOSIS

Tissue biopsy stained with Congo red demonstrating amyloid deposits with apple-green birefringence is required for diagnosis. Invasive organ biopsy is not required because amyloid deposits can be found in bone marrow biopsy or subcutaneous fat aspirate in 85% of patients. Verification that amyloid is of immunoglobulin origin is mandatory.

PROGNOSIS

N-terminal pro-brain natriuretic peptide (NT-proBNP), serum troponin T, and immunoglobulin free light chain values are used to classify patients into four groups of similar size; median survivals are 94.1, 40.3, 14.0, and 5.8 months.

THERAPY

All patients with a visceral amyloid syndrome require therapy to prevent deposition of amyloid in other viscera and prevent progressive organ failure of involved sites. Stem cell transplant (SCT) is preferred, but only 20% of patients are eligible. Requirements for safe SCT include NT-proBNP <5,000 ng/mL, troponin T < 0.06 ng/mL, age <70 years, <3 organs involved, and serum creatinine ≤1.7 mg/dL. Nontransplant candidates can be offered melphalan-dexamethasone. Pomalidomide appears to have activity, as do other combinations of chemotherapy with agents such as cyclophosphamide-thalidomide (or lenalidomide or bortezomib)-dexamethasone, bortezomib-dexamethasone, and melphalan-prednisone-lenalidomide.

FUTURE CHALLENGES

Late diagnosis remains a major obstacle to initiating effective therapy when organ dysfunction is still recoverable. Recognizing the presenting syndromes is necessary for improving survival.

(99m)Tc-pyrophosphate scintigraphy for differentiating light-chain cardiac amyloidosis from the transthyretin-related familial and senile cardiac amyloidoses

BACKGROUND

Differentiating immunoglobulin light-chain (AL) from transthyretin-related cardiac amyloidoses (ATTR) is imperative given implications for prognosis, therapy, and genetic counseling. We validated the discriminatory ability of (99m)Tc-pyrophosphate ((99m)Tc-PYP) scintigraphy in AL versus ATTR.

METHODS AND RESULTS

Forty-five subjects (12 AL, 16 ATTR wild type, and 17 ATTR mutants) underwent (99m)Tc-PYP planar and single-photon positive emission computed tomography cardiac imaging. Scans were performed by experienced nuclear cardiologists blinded to the subjects' cohort assignment. Cardiac retention was assessed with both a semiquantitative visual score (range, 0; no uptake to 3, diffuse uptake) and by quantitative analysis by drawing a region of interest over the heart corrected for contralateral counts and calculating a heart-to-contralateral ratio. Subjects with ATTR cardiac amyloid had a significantly higher semiquantitative cardiac visual score than the AL cohort (2.9±0.06 versus 0.8±0.27; P<0.0001) as well as a higher quantitative score (1.80±0.04 versus 1.21±0.04; P<0.0001). Using a heart-to-contralateral ratio >1.5 consistent with intensely diffuse myocardial tracer retention had a 97% sensitivity and 100% specificity with area under the curve 0.992, P<0.0001 for identifying ATTR cardiac amyloidosis.

CONCLUSIONS

(99m)Tc-PYP cardiac imaging distinguishes AL from ATTR cardiac amyloidosis and may be a simple, widely available method for identifying subjects with ATTR cardiac amyloidosis, which should be studied in a larger prospective manner.

Imaging in systemic amyloidosis

BACKGROUND

Diagnosis of systemic amyloidosis remains challenging. Histology, the current gold standard for diagnosis of amyloidosis provides limited information on the extent of the disease and is not useful for monitoring. Non-invasive imaging modalities offer an easy way to evaluate whole-body amyloid burden, accurately identify organ involvement, quantify and monitor disease progression and response to treatment.

SOURCES OF DATA

A literature search was performed using PubMed on the subjects of 'amyloid imaging', 'SAP scintigraphy', 'imaging in cardiac amyloidosis', 'cardiac MRI', 'PET and amyloidosis' and 'nuclear imaging in amyloidosis'.

AREAS OF AGREEMENT

¹²³I-SAP scintigraphy is the best and the only modality in routine clinical use for assessing the extent and distribution of visceral amyloid deposition in all types of amyloidosis. Echocardiography remains the most important tool for assessing cardiac amyloidosis but cardiac magnetic resonance imaging is becoming increasingly valuable. Bone-seeking tracers like 99mTc-DPD and pyrophosphate are beginning to have a role in imaging transthyretin cardiac amyloidosis.

LIMITATIONS

Specificity of each of the imaging modalities limits the utility of any one imaging method for all types of amyloidosis for all organs. GROWING POINTS AND FURTHER RESEARCH: 99mTc-DPD has a high sensitivity and specificity to cardiac transthyretin amyloid deposits and its role in early diagnosis of this condition is under investigation. Further studies are needed with ¹²³I-mIBG to assess its utility in patients with early cardiac autonomic neuropathy. Positron emission tomography with tracers used for Alzheimer's disease imaging is an area of increasing interest in systemic amyloid imaging.

Imagining the future of diagnostic imaging

Cardiovascular imaging has become essential to achieving a better understanding of cardiovascular diseases. Due to the advent of new technology and the refinement of existing technologies, imaging's role has extended into the biological, functional, and hemodynamic diagnosis of multiple pathophysiologic processes. Current and future trends in cardiovascular imaging will focus on improving early diagnosis of vascular disease, so as to be able to promote cardiovascular health, and on its development as a useful tool in clinical decision-making. Imaging is also increasingly used to quantify the effect of novel therapies. The rapid development of molecular imaging and fusion imaging techniques improves our understanding of cardiovascular processes from the molecular and cellular points of view and makes it possible to design and test new preventive interventions. The proliferation and integration of imaging techniques in different clinical areas and their role in "translational imaging" plays an important part in the implementation of personalized therapeutic and preventive management strategies for patients with cardiovascular disease.