(99m)Tc-DPD uptake reflects amyloid fibril composition in hereditary transthyretin amyloidosis

Epidemiology, diagnosis, and management of cardiac amyloidosis

Cardiac amyloidosis (CA) is an infiltrative restrictive cardiomyopathy caused by the deposition of amyloid fibrils in the myocardium. It manifests in two primary subtypes: transthyretin cardiac amyloidosis (ATTR) and immunoglobulin light chain cardiac amyloidosis (AL). ATTR is further classified into wild-type and hereditary based on transthyretin gene mutation. Advances in diagnostics and therapeutics have transformed CA from a rare and untreatable condition to a more prevalent and manageable disease. Noninvasive diagnostic tools such as electrocardiography, echocardiography, and cardiac magnetic resonance can raise suspicion for CA; bone scintigraphy can non-invasively confirm ATTR, while AL necessitates histological confirmation. The severity of ATTR and AL can be assessed through serum biomarker-based staging. Treatment approaches differ, ranging from silencing or stabilizing transthyretin and degrading amyloid fibrils in ATTR to employing anti-plasma cell therapies and autologous stem cell transplantation in AL.

Diagnostic Modalities in the Detection of Cardiac Amyloidosis

Cardiac amyloidosis (CA) results mainly from the infiltration of the myocardium by either immunoglobulin light-chain fibrils (AL) or transthyretin fibrils (ATTR), causing restrictive cardiomyopathy and eventually death if untreated. AL derives from monoclonal immunoglobulin light chains produced by plasma cell clones in the bone marrow, while ATTR is the misfolded form of hepatically derived transthyretin (TTR) protein and can be hereditary (ATTRv) or wild-type (ATTRwt). Over the last decade, improvements in diagnostic imaging and better clinical awareness have unleashed a notable presence of CA in the community, especially ATTR in the elderly population. These multimodality imaging modalities include echocardiography, cardiac magnetic resonance, and radionuclide scintigraphy with bone-avid tracers. There has been remarkable progress in the therapeutic landscape as well, and there are disease-modifying therapies available now that can alter the course of the disease and improve survival if initiated at an early stage of the disease. There remains an unmet need for detecting this disease accurately and early so that these patients can benefit the most from newly emerging therapies.

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.

How Artificial Intelligence Can Enhance the Diagnosis of Cardiac Amyloidosis: A Review of Recent Advances and Challenges

Cardiac amyloidosis (CA) is an underdiagnosed form of infiltrative cardiomyopathy caused by abnormal amyloid fibrils deposited extracellularly in the myocardium and cardiac structures. There can be high variability in its clinical manifestations, and diagnosing CA requires expertise and often thorough evaluation; as such, the diagnosis of CA can be challenging and is often delayed. The application of artificial intelligence (AI) to different diagnostic modalities is rapidly expanding and transforming cardiovascular medicine. Advanced AI methods such as deep-learning convolutional neural networks (CNNs) may enhance the diagnostic process for CA by identifying patients at higher risk and potentially expediting the diagnosis of CA. In this review, we summarize the current state of AI applications to different diagnostic modalities used for the evaluation of CA, including their diagnostic and prognostic potential, and current challenges and limitations.

Diagnostic and prognostic contribution of DPD scintigraphy in transthyretin V30M cardiac amyloidosis

BACKGROUND

Early diagnosis and prognostic stratification of cardiac transthyretin amyloidosis are crucial. Although 99mTc 3,3-diphosphono-1,2-propanedicarboxylic acid (DPD) scintigraphy is the preferred method for the non-invasive diagnosis, its accuracy appears to be limited in transthyretin amyloidosis protein (ATTR) V30M mutation. Furthermore, its prognostic value in this mutation is unknown. This study investigated the diagnostic value of DPD scintigraphy to detect ATTR cardiomyopathy in V30M mutation and explored its prognostic value regarding mortality.

METHODS

A total of 288 ATTR V30M mutation carriers (median age: 46 years; 49% males) without myocardial thickening (defined as septal thickness ≥13mm) attributable to other causes and who underwent DPD scintigraphy were enrolled. ATTR cardiomyopathy was defined by septal thickness ≥13mm and at least one of the criteria: late heart-to-mediastinum (H/M) 123I-metaiodobenzylguanidine (MIBG) uptake ratio <1.60; electrical heart disease or biopsy-documented amyloidosis.

RESULTS

ATTR cardiomyopathy was identified in 41 (14.2%) patients and cardiac DPD uptake in 34 (11.8%). During a mean follow-up of 33.6 ± 1.2 months, 16 patients died (5.6%). Mortality was 14 times higher in patients with ATTR cardiomyopathy, 13 times higher in those with DPD uptake and 10 times higher in those with late H/M MIBG <1.60. The combined assessment of septal thickness and cardiac DPD uptake improved risk stratification: patients without septal thickening and without DPD retention had an excellent prognosis while those who presented either or both of them had a significantly worse prognosis, with 5-year mortality rates ranging from 39.9 to 53.3%.

CONCLUSIONS

DPD scintigraphy is useful for prognostic stratification of ATTR V30M mutation carriers. Patients without septal thickening and no DPD uptake present the best prognosis compared to those with any signs of cardiac involvement.

High-Sensitivity Cardiac Troponin T to Exclude Cardiac Involvement in TTR Variant Carriers and ATTRv Amyloidosis Patients

(1) Background: Individuals carrying a pathogenic transthyretin gene variant (TTRv) are at high risk for developing hereditary transthyretin (ATTRv) amyloidosis and are routinely screened for the development of cardiomyopathy (ATTRv-CM). This study aims to evaluate whether the cardiac biomarkers N-terminal pro B-type natriuretic peptide (NT-proBNP) and high-sensitivity cardiac troponin T (hs-cTnT) can be used to rule out ATTRv-CM. (2) Methods: In this retrospective case-control study, data from 46 ATTRv-CM patients and 101 TTRv carriers and ATTRv amyloidosis patients without cardiomyopathy were included. Binary logistic regression models were used to assess the ability of NT-proBNP and hs-cTnT to predict the diagnosis of ATTRv-CM. An optimal cutoff for the relevant biomarker(s) was determined based on a sensitivity of ≥99% and the highest possible percentage of additional tests avoided (%ATA) in the index dataset. (3) Results: Hs-cTnT demonstrated the highest predictive capabilities for ATTRv-CM. The addition of NT-proBNP did not improve the predictive model. A hs-cTnT cutoff of <6 ng/L resulted in a 97% sensitivity and a negative predictive value of 95% with a %ATA of 30% in the validation dataset. (4) Conclusion: In conclusion, hs-cTnT is a useful biomarker for excluding cardiac involvement in TTRv carriers and ATTRv amyloidosis patients and it has the potential to prevent unnecessary diagnostic procedures.

Rare c.302C>T TTR Variant Associated with Transthyretin Amyloidosis

Background and Objectives: Hereditary transthyretin amyloidosis (ATTRv) is a rare disease caused by pathogenic variants in the transthyretin (TTR) gene. More than 140 different disease-causing variants in TTR have been reported. Only a few individuals with a rare TTR variant, c.302C>T, p.(Ala101Val) (historically known as p.(Ala81Val)), primarily associated with cardiac ATTRv, have been described. Therefore, our aim was to analyze the clinical characteristics of individuals with the identified c.302C>T TTR variant at our center. Materials and Methods: We analyzed data from individuals with ATTRv who were diagnosed and treated at Vilnius University Hospital Santaros Klinikos. ATTRv was confirmed by negative hematological analysis for monoclonal protein, positive tissue biopsy or bone scintigraphy and a pathogenic TTR variant. Results: During 2018-2021, the TTR NM_000371.3:c.302C>T, NP_000362.1:p.(Ala101Val) variant was found in one individual in a homozygous state and in three individuals in a heterozygous state. The age of onset of symptoms ranged from 44 to 74 years. The earliest onset of symptoms was in the individual with the homozygous variant. A history of carpal tunnel syndrome was identified in two individuals. On ECG, three individuals had low QRS voltage in limb leads. All individuals had elevated NT-proBNP and hsTroponine I levels on baseline laboratory tests and concentric left ventricular hypertrophy on transthoracic echocardiography. The individual with the homozygous c.302C>T TTR variant had the most pronounced polyneuropathy with tetraparesis. Other patients with the heterozygous variant had more significant amyloid cardiomyopathy. When screening family members, the c.302C>T TTR variant was identified in two phenotypically negative relatives at the ages of 33 and 47 years. Conclusions: c.302C>T is a rare TTR variant associated with ATTRv cardiomyopathy. The homozygous state of this variant was not reported before, and is associated with earlier disease onset and neurological involvement compared to the heterozygote state.

Lights and Shadows of Clinical Applications of Cardiac Scintigraphy with Bone Tracers in Suspected Amyloidosis

Radionuclide bone scintigraphy is the cornerstone of an imaging-based algorithm for accurate non-invasive diagnosis of transthyretin cardiac amyloidosis (ATTR-CA). In patients with heart failure and suggestive echocardiographic and/or cardiac magnetic resonance imaging findings, the positive predictive value of Perugini grade 2 or 3 myocardial uptake on a radionuclide bone scan approaches 100% for the diagnosis of ATTR-CA as long as there is no biochemical evidence of a clonal dyscrasia. The technetium-labelled tracers that are currently validated for non-invasive diagnosis of ATTR-CA include pyrophosphate (99mTc-PYP); hydroxymethylene diphosphonate (99mTc-HMDP); and 3,3-diphosphono-1,2-propanodicarboxylate (99mTc-DPD). Although nuclear scintigraphy has transformed the contemporary diagnostic approach to ATTR-CA, a number of grey areas remains, including the mechanism for binding tracers to the infiltrated heart, differences in the kinetics and distribution of these radiotracers, differences in protocols of image acquisition worldwide, the clinical significance of extra-cardiac uptake, and the use of this technique for prognostic stratification, monitoring disease progression and assessing the response to disease-modifying treatments. This review will deal with the most relevant unmet needs and clinical questions concerning scintigraphy with bone tracers in ATTR-CA, providing expert opinions on possible future developments in the clinical application of these radiotracers in order to offer practical information for the interpretation of nuclear images by physicians involved in the care of patients with this ATTR-CA.

State-of-the-Art Imaging of Infiltrative Cardiomyopathies: A Scientific Statement From the American Heart Association

Infiltrative cardiomyopathies comprise a broad spectrum of inherited or acquired conditions caused by deposition of abnormal substances within the myocardium. Increased wall thickness, inflammation, microvascular dysfunction, and fibrosis are the common pathological processes that lead to abnormal myocardial filling, chamber dilation, and disruption of conduction system. Advanced disease presents as heart failure and cardiac arrhythmias conferring poor prognosis. Infiltrative cardiomyopathies are often diagnosed late or misclassified as other more common conditions, such as hypertrophic cardiomyopathy, hypertensive heart disease, ischemic or other forms of nonischemic cardiomyopathies. Accurate diagnosis is also critical because clinical features, testing methodologies, and approach to treatment vary significantly even within the different types of infiltrative cardiomyopathies on the basis of the type of substance deposited. Substantial advances in noninvasive cardiac imaging have enabled accurate and early diagnosis. thereby eliminating the need for endomyocardial biopsy in most cases. This scientific statement discusses the role of contemporary multimodality imaging of infiltrative cardiomyopathies, including echocardiography, nuclear and cardiac magnetic resonance imaging in the diagnosis, prognostication, and assessment of response to treatment.

Tafamidis decreased cardiac amyloidosis deposition in patients with Ala97Ser hereditary transthyretin cardiomyopathy: a 12-month follow-up cohort study

BACKGROUND

Transthyretin cardiac cardiomyopathy (ATTR-CM) is a rare but life-threatening disease. Tafamidis is an effective treatment for patients with ATTR-CM, however its long-term effects on cardiac remodeling and cardiac amyloid deposition are unknown. This study aimed to used cardiac magnetic resonance (CMR) to investigate the effects of tafamidis on patients with hereditary A97S ATTR-CM.

METHODS

We retrospectively analyzed a prospective cohort of ATTR-CM patients, including 14 with hereditary A97S ATTR-CM and 17 healthy controls with baseline CMR data. All ATTR-CM patients received tafamidis treatment and received CMR with extracellular volume (ECV) at baseline and after 1 year of follow-up.

RESULTS

Baseline N-terminal pro-B-type natriuretic peptide, left ventricular (LV) mass, LV ejection fraction, global radial, circumferential and longitudinal strain, T1 mapping and ECV were significantly worse in the patients with ATTR-CM compared with the healthy controls. After 1 year of tafamidis treatment, ECV decreased from 51.5 ± 8.9% to 49.0 ± 9.4% (P = 0.041), however there were no significant changes in LV mass, LV ejection fraction, global radial strain, global circumferential strain, global longitudinal strain and T1 mapping.

CONCLUSIONS

After a one-year treatment period, tafamidis exhibited subtle but statistically significant reductions in ECV, potentially indicating a decrease in amyloid deposition among patients diagnosed with hereditary A97S ATTR-CM.

Prevalence of ventricular arrhythmias and role of implantable cardioverter-defibrillator in cardiac amyloidosis

Cardiac amyloidosis is an underdiagnosed disease that is caused by myocardial deposition of misfolded light chain (AL) or transthyretin (ATTR) amyloid fibrils, leading to restrictive cardiomyopathy and eventually death if untreated. Ventricular arrhythmias are common in cardiac amyloidosis, and the prevalence is higher in AL than ATTR. There are multiple suspected pathogenic mechanisms for ventricular arrhythmia including activation of inflammatory cascade from direct amyloid deposition, and electro-mechanical as well as autonomic dysfunction due to systemic amyloid deposition. Cardiac amyloidosis is associated with an increased risk of sudden cardiac death, and the risk is higher in AL than ATTR. Finally, the role of implantable cardioverter-defibrillators in cardiac amyloidosis is controversial, and while successful termination of life-threatening ventricular arrhythmias has been reported in few studies, there has been no evidence of improvement in outcomes when used for primary prevention in patients with cardiac amyloidosis.

Description of a different quantification method for amyloid burden (DPDload) and validation of SPECT/CT in cardiac amyloidosis

BACKGROUND

Bone tracers such as ^99mTc-DPD have shown high sensitivity and specificity in the non-invasive diagnosis of transthyretin cardiac amyloidosis (ATTR-CA). This study aims to validate SPECT/CT and assess the usefulness of uptake quantification (DPDload) in the myocardial tissue as potential information on the amyloid burden.

METHODS

In a retrospective analysis of 46 patients with suspected CA, 23 cases with ATTR-CA had two quantification methods conducted to estimate amyloid burden (DPDload) through planar scintigraphic scans and a SPECT/CT.

RESULTS

SPECT/CT significantly provided an added value in the patient's diagnosis with CA (P<.05). The estimation of the amyloid burden substantiated that the most affected wall of the LV is the interventricular septum in most cases and the existence of a significant relationship between the Perugini score uptake and the DPDload.

CONCLUSIONS

We validate the need for SPECT/CT to complement planar imaging in diagnosing ATTR-CA. For its part, quantifying the amyloid load continues to be a complex area of research. It requires further studies with a larger number of patients to validate a standardized method of amyloid load quantification, both for diagnosis and treatment monitoring.

Does [99mTc]-3,3-diphosphono-1,2-propanodicarboxylic acid (DPD) soft tissue uptake allow the identification of patients with the diagnosis of cardiac transthyretin-related (ATTR) amyloidosis with higher risk for polyneuropathy?

BACKGROUND

With the introduction of several drugs for the therapy of transthyretin-related amyloidosis (ATTR) which slow down the disease, early detection of polyneuropathy (PNP) is becoming increasingly of interest. [99mTc]-3,3-Diphosphono-1,2-Propanodicarboxylic Acid (DPD) bone scintigraphy, which is used for the diagnosis of cardiac (c)ATTR, can possibly make an important contribution in the identification of patients at risk for PNP.

METHODS

Fifty patients with cATTR, who underwent both planar whole-body DPD scintigraphy and nerve conduction studies (NCS) were retrospectively evaluated. A subgroup of 22 patients also underwent quantitative SPECT/CT of the thorax from which Standardized Uptake Values (SUVpeak) in the subcutaneous fat tissue of the left axillar region were evaluated.

RESULTS

The Perugini score was significantly increased in patients with cATTR and additional diagnosis of PNP compared to patients without (2.51 ± 0.51 vs 2.13 ± 0.52; P = 0.03). Quantitative SPECT/CT revealed that DPD uptake in the subcutaneous fat of the left axillar region was significantly increased in cATTR patients with compared to patients without (1.36 ± 0.60 vs 0.74 ± 0.52; P = 0.04).

CONCLUSION

This study suggests that DPD bone scintigraphy is a useful tool for identification of patients with cATTR and a risk for PNP due to increased DPD soft tissue uptake.

Microcalcification and 99mTc-Pyrophosphate Uptake without Increased Bone Metabolism in Cardiac Tissue from Patients with Transthyretin Cardiac Amyloidosis

Transthyretin cardiac amyloidosis (ATTR-CA) is characterized by high ^99mTc-labeled bone tracer uptake in the heart. However, the mechanism of bone tracer uptake into the heart remains controversial. Since bone tracer uptake into metastatic bone tumors is thought to be associated with increased bone metabolism, we examined ^99mTc-pyrophosphate (PYP) scintigraphy findings, endomyocardial biopsy (EMB) tissue findings, and the expression of bone metabolism-related genes in the EMB tissues in patients with ATTR-CA, amyloid light-chain cardiac amyloidosis (AL-CA), and noncardiac amyloidosis (non-CA) in this study. The uptake of ^99mTc-PYP in the heart was significantly higher in the ATTR-CA patients than in the AL-CA and non-CA patients. A higher percentage of ATTR-CA EMB tissue showed von Kossa-positive microparticles: ATTR-CA, 62%; AL-CA, 33%; and non-CA, 0%. Calcified microparticles were identified using transmission electron microscopy. However, none of the osteogenic marker genes, osteoclastic marker genes, or phosphate/pyrophosphate-related genes were upregulated in the EMB samples from ATTR-CA patients compared to those from AL-CA and non-CA patients. These results suggest that active calcification-promoting mechanisms are not involved in the microcalcification observed in the heart in ATTR-CA. The mechanisms explaining bone tracer uptake in the heart, which is stronger than that in the ribs, require further investigation.

Atrial Fibrillation, Thromboembolic Risk, and Anticoagulation in Cardiac Amyloidosis: A Review

Cardiac amyloidosis (CA) is caused by extracellular myocardial deposition of amyloid fibrils that are primary derived either from misfolding of transthyretin (ATTR) or light-chain (AL) proteins. CA is associated with atrial fibrillation, potentiated by electromechanical changes as a result of amyloid infiltration in the myocardium. CA also predisposes to thromboembolism and could potentially simultaneously elevate bleeding risk. In this review, we aim to explore and compare the prevalence and pathophysiological mechanisms of atrial fibrillation and thromboembolism in ATTR and AL, examine bleeding risk and factors that promote bleeding, and compare anticoagulation strategies in CA. Finally, we highlight knowledge gaps in the field of thromboembolism in CA to guide future research.

Drug and Gene Therapy for Treating Variant Transthyretin Amyloidosis (ATTRv) Neuropathy

Variant Transthyretin Amyloidosis (ATTRv) neuropathy is an adult-onset, autosomal dominant, lethal, multisystemic disease due to the deposition of mutated transthyretin (TTR) in various organs, commonly involving the peripheral nerves and the heart. Circulating TTR tetramers are unstable due to the presence of mutated TTR and dissociate into monomers, which misfold and form amyloid fibrils. Although there are more than 140 mutations in the TTR gene, the p.Val50Met mutation is by far the commonest. In the typical, early-onset cases, it presents with a small sensory fibre and autonomic, length-dependent, axonal neuropathy, while in late-onset cases, it presents with a lengthdependent sensorimotor axonal neuropathy involving all fibre sizes. Treatment is now available and includes TTR stabilizers, TTR amyloid removal as well as gene silencing, while gene editing therapies are on the way. Its timely diagnosis is of paramount importance for a better prognosis.

Multimodality imaging in cardiac amyloidosis: State-of-the-art review

Amyloidosis is a systemic disease, characterized by deposition of amyloid fibrils in various organs, including the heart. For the diagnosis of cardiac amyloidosis (CA) it is required a high level of clinical suspicion and in the presence of clinical, laboratorial, and electrocardiographic red flags, a comprehensive multimodality imaging evaluation is warranted, including echocardiography, magnetic resonance, scintigraphy, and computed tomography, that will confirm diagnosis and define the CA subtype, which is of the utmost importance to plan a treatment strategy. We will review the use of multimodality imaging in the evaluation of CA, including the latest applications, and a practical flow-chart will sum-up this evidence.

Screening for Cardiac Amyloidosis 5 to 15 Years After Surgery for Bilateral Carpal Tunnel Syndrome

BACKGROUND

Bilateral carpal tunnel syndrome (CTS) is a common extracardiac manifestation of amyloidosis and usually predates overt cardiac amyloidosis (CA) by several years. Screening studies on patients undergoing CTS surgery have shown a low yield of CA (2.0%), but high prevalence of amyloid in the carpal ligament. The proportion of patients with amyloid in the carpal ligament who later develop CA is unknown.

OBJECTIVES

The authors sought to investigate the prevalence of undiagnosed CA 5 to 15 years after surgery for bilateral CTS.

METHODS

Using national registries, the authors identified subjects aged 60 to 85 years with prior CTS surgery, where the first procedure on the second wrist was performed 5 to 15 years earlier. Invitations to participate in the study were sent by mail. Per international recommendations, the initial cardiac evaluation included echocardiography, ^99mtechnetium-pyrophosphate scintigraphy, and assessment of monoclonal proteins in serum and urine.

RESULTS

A total of 250 subjects (35.7% of those invited) participated in the study. The median age was 70.4 years, and 50% were female. CA was diagnosed in 12 patients (4.8%; 95% CI: 2.5%-8.2%), and all cases were wild-type transthyretin amyloidosis (ATTRwt). The prevalence of ATTRwt in men was 8.8% (95% CI: 4.5%-15.2%; n = 11), and 21.2% (95% CI: 11.1%-34.7%) in male subjects ≥70 years with a BMI <30 kg/m². All but 2 patients diagnosed with ATTRwt were in the lowest disease severity score (Mayo score).

CONCLUSIONS

Screening for CA in patients with prior surgery for bilateral CTS finds approximately 5% with early-stage transthyretin CA. The clinical yield was higher (>1 in 5) when focusing on nonobese men ≥70 years, showing potential for systematic screening.

Multi-Imaging Characterization of Cardiac Phenotype in Different Types of Amyloidosis

BACKGROUND

Bone scintigraphy is extremely valuable when assessing patients with suspected cardiac amyloidosis (CA), but the clinical significance and associated phenotype of different degrees of cardiac uptake across different types is yet to be defined.

OBJECTIVES

This study sought to define the phenotypes of patients with varying degrees of cardiac uptake on bone scintigraphy, across multiple types of systemic amyloidosis, using extensive characterization comprising biomarkers as well as echocardiographic and cardiac magnetic resonance (CMR) imaging.

METHODS

A total of 296 patients (117 with immunoglobulin light-chain amyloidosis [AL], 165 with transthyretin (TTR) amyloidosis [ATTR], 7 with apolipoprotein AI amyloidosis [AApoAI], and 7 with apolipoprotein AIV amyloidosis [AApoAIV]) underwent deep characterization of their cardiac phenotype.

RESULTS

AL patients with grade 0 myocardial radiotracer uptake spanned the spectrum of CMR findings from no CA to characteristic CA, whereas AL patients with grades 1 to 3 always produced characteristic CMR features. In ATTR, the CA burden strongly correlated with myocardial tracer uptake, except in Ser77Tyr. AApoAI presented with grade 0 or 1 and disproportionate right-sided involvement. AApoAIV always presented with grade 0 and characteristic CA. AL grade 1 patients (n = 48; 100%) had characteristic CA, whereas only ATTR grade 1 patients with Ser77Tyr had characteristic CA on CMR (n = 5; 11.4%). After exclusion of Ser77Tyr, AApoAI, and AApoAIV, CMR showing characteristic CA or an extracellular volume of >0.40 in patients with grade 0 to 1 cardiac uptake had a sensitivity and specificity of 100% for AL.

CONCLUSIONS

There is a wide variation in cardiac phenotype between different amyloidosis types across different degrees of cardiac uptake. The combination of CMR and bone scintigraphy can help to define the diagnostic differentials and the clinical phenotype in each individual patient.

Three Newly Recognized Likely Pathogenic Gene Variants Associated with Hereditary Transthyretin Amyloidosis

INTRODUCTION

Hereditary transthyretin amyloidosis (ATTRv [variant]) is a clinically heterogeneous, progressively debilitating, fatal disease resulting from the deposition of insoluble amyloid fibrils in various organs and tissues. Early diagnosis of ATTRv can be facilitated with genetic testing; however, such testing of the TTR gene identifies variants of uncertain significance (VUS) in a minority of cases, a small percentage of which have the potential to be pathogenic. The Akcea/Ambry VUS Initiative is dedicated to gathering molecular, clinical, and inheritance data for each TTR VUS identified by genetic testing programs to reclassify TTR variants to a clinically actionable status (e.g., variant likely pathogenic [VLP]) where appropriate.

METHODS

Classification criteria used here, based on recommendations from the American College of Medical Genetics and Genomics, are stringent and comprehensive, requiring distinct lines of evidence supporting pathogenesis.

RESULTS

Three TTR variants have been reclassified from VUS to VLP, including c.194C>T (p.A65V), c.172G>C (p.D58H), and c.239C>T (p.T80I). In each case, the totality of genetic, structural, and clinical evidence provided strong support for pathogenicity.

CONCLUSIONS

Based on several lines of evidence, three TTR VUS were reclassified as VLP, resulting in a high likelihood of disease diagnosis for those and subsequent patients as well as at-risk family members.

Epidemiology of hereditary transthyretin amyloidosis in the northernmost region of Sweden: a retrospective cohort study

INTRODUCTION

Epidemiological data on hereditary transthyretin (ATTRv) amyloidosis from the northernmost region of Sweden (Norrbotten) are sparse.

METHODS

We reviewed the medical records of all incident cases of ATTRv amyloidosis in Norrbotten between 2006 and 2018. Official population and mortality statistics were used to estimate incidence rates and standardised mortality ratios (SMRs).

RESULTS

Ninety-three patients were diagnosed with ATTRv amyloidosis between 2006 and 2018 (median age, 72.8 years; 68.8% men; 95.7% Val30Met [p.Val50Met] mutation). The incidence rate per 100,000 persons and year increased from 1.50 (95% confidence interval [CI], 0.84-2.47) cases in 2006-2009 to 4.92 (95%CI, 3.46-6.78) cases in 2016-2018. The SMR in the ATTRv amyloidosis cohort was 2.64 times higher than in the general population in 2006-2018 (95%CI, 1.78-3.77). However, there were indications of lower SMRs over time (2006-2012, 2.96 [95%CI, 1.73-4.74]; 2013-2018, 2.32 [95%CI, 1.23-3.96]) and by use of disease-modifying drugs (no, 3.21 [95%CI, 1.87-5.13]; yes, 2.09 [95%CI, 1.08-3.64]).

CONCLUSION

The incidence of ATTRv amyloidosis increased 3-fold in Norrbotten between 2006 and 2018, most likely due to a previous underdiagnosis - with suggestions of lowered mortality during later years, possibly due to the introduction of disease-modifying drugs.

Suspicion, screening, and diagnosis of wild-type transthyretin amyloid cardiomyopathy: a systematic literature review

Wild-type transthyretin amyloid cardiomyopathy (ATTRwt CM) is a more common disease than previously thought. Awareness of ATTRwt CM and its diagnosis has been challenged by its unspecific and widely distributed clinical manifestations and traditionally invasive diagnostic tools. Recent advances in echocardiography and cardiac magnetic resonance (CMR), non-invasive diagnosis by bone scintigraphy, and the development of disease-modifying treatments have resulted in an increased interest, reflected in multiple publications especially during the last decade. To get an overview of the scientific knowledge and gaps related to patient entry, suspicion, diagnosis, and systematic screening of ATTRwt CM, we developed a framework to systematically map the available evidence of (i) when to suspect ATTRwt CM in a patient, (ii) how to diagnose the disease, and (iii) which at-risk populations to screen for ATTRwt CM. Articles published between 2010 and August 2021 containing part of or a full diagnostic pathway for ATTRwt CM were included. From these articles, data for patient entry, suspicion, diagnosis, and screening were extracted, as were key study design and results from the original studies referred to. A total of 50 articles met the inclusion criteria. Of these, five were position statements from academic societies, while one was a clinical guideline. Three articles discussed the importance of primary care providers in terms of patient entry, while the remaining articles had the cardiovascular setting as point of departure. The most frequently mentioned suspicion criteria were ventricular wall thickening (44/50), carpal tunnel syndrome (42/50), and late gadolinium enhancement on CMR (43/50). Diagnostic pathways varied slightly, but most included bone scintigraphy, exclusion of light-chain amyloidosis, and the possibility of doing a biopsy. Systematic screening was mentioned in 16 articles, 10 of which suggested specific at-risk populations for screening. The European Society of Cardiology recommends to screen patients with a wall thickness ≥12 mm and heart failure, aortic stenosis, or red flag symptoms, especially if they are >65 years. The underlying evidence was generally good for diagnosis, while significant gaps were identified for the relevance and mutual ranking of the different suspicion criteria and for systematic screening. Conclusively, patient entry was neglected in the reviewed literature. While multiple red flags were described, high-quality prospective studies designed to evaluate their suitability as suspicion criteria were lacking. An upcoming task lies in defining and evaluating at-risk populations for screening. All are steps needed to promote early detection and diagnosis of ATTRwt CM, a prerequisite for timely treatment.

It Takes a Village: Multimodality Imaging of Cardiac Amyloidosis

Cardiac amyloidosis (CA) is the buildup and infiltration of amyloid plaque in cardiac muscle. An underdiagnosed form of restrictive cardiomyopathy, CA can rapidly progress into heart failure. CA is evaluated using a multimodality approach that includes echocardiography, cardiac magnetic imaging, and nuclear imaging. Echocardiography remains an essential first-line modality that raises suspicion for CA and establishes functional baselines. Cardiac magnetic imaging provides additional incremental value via high-resolution imaging, robust functional assessment, and superior tissue characterization, all of which enable a more comprehensive investigation of CA. Cardiac scintigraphy has eliminated the need for invasive diagnostic approaches and helps differentiate CA subtypes. Positron emission tomography is the first modality introducing targeted amyloid binding tracers that allow for precise burden quantification, early detection, and disease monitoring. In this review, we highlight the role of several cardiac imaging techniques in the evaluation of CA.

Diagnostic Work-Up of Cardiac Amyloidosis Using Cardiovascular Imaging: Current Standards and Practical Algorithms

Among non-ischemic cardiomyopathies, cardiac amyloidosis is one of the most common, being caused by extracellular depositions of amyloid fibrils in the myocardium. Two main forms of cardiac amyloidosis are known so far, including 1) light-chain (AL) amyloidosis caused by monoclonal production of light-chains, and 2) transthyretin (ATTR) amyloidosis, caused by dissociation of the transthyretin tetramer into monomers. Both AL and ATTR amyloidosis are progressive diseases with median survival from diagnosis of less than 6 months and 3 to 5 years, respectively, if untreated. In this regard, death occurs in most patients due to cardiac causes, mainly congestive heart failure, which can be prevented due to the presence of effective, life-saving treatment regimens. Therefore, early diagnosis of cardiac amyloidosis is crucial more than ever. However, diagnosis of cardiac amyloidosis may be challenging due to variable clinical manifestations and the perceived rarity of the disease. In this regard, clinical and laboratory reg flags are available, which may help clinicians to raise suspicion of cardiac amyloidosis. In addition, advances in cardiovascular imaging have already revealed a higher prevalence of cardiac amyloidosis in specific populations, so that the diagnosis especially of ATTR amyloidosis has experienced a >30-fold increase during the past ten years. The goal of our review article is to summarize these findings and provide a practical approach for clinicians on how to use cardiovascular imaging techniques, such as echocardiography, cardiac magnetic resonance, bone scintigraphy and, if required, organ biopsy within predefined diagnostic algorithms for the diagnostic work-up of patients with suspected cardiac amyloidosis. In addition, two clinical cases and practical tips are provided in this context.

99mTechnetium-labeled cardiac scintigraphy for suspected amyloidosis: a review of current and future directions

Cardiac amyloidosis (CA) is an underdiagnosed form of restrictive cardiomyopathy leading to a rapid progression into heart failure. Evaluation of CA requires a multimodality approach making use of echocardiography, cardiac magnetic imaging, and nuclear imaging. Technetium (Tc)-labeled cardiac scintigraphy has witnessed a resurgence in its application for the workup of CA. Advancements in disease-modifying therapies have fueled the rapid adoption of cardiac scintigraphy using bone tracers and the need for transformative novel studies. The goal of this review is to present diagnostic utility, currently recommended protocols, as well as a glimpse into the rapid evolution of Tc-labeled cardiac scintigraphy in the diagnosis of CA.

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

BACKGROUND

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

METHODS AND RESULTS

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

CONCLUSION

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

Transthyretin cardiac amyloidosis: a review of the nuclear imaging findings with emphasis on the radiotracers mechanisms

Cardiac amyloidosis is a protein deposition disease characterized by the infiltration of the myocardium and coronary arteries resulting in a progressive thickening of both ventricles, interatrial septum and atrioventricular valves, eventually leading to organ failure. It is a disease hard to diagnose, due to the lack of diagnostic investigations. However, development of new and more accurate examinations is undergoing. Endomyocardial biopsy is the gold standard investigation for this disease, but it has its limitations (invasive and not widely available). Other investigations may be able to detect the presence of cardiac amyloidosis but cannot specify the type involved. To that end, nuclear medicine through bone scanning offers a simple, non-invasive solution to detect, differentiate and diagnose transthyretin cardiac amyloidosis (ATTR) from other types of cardiac amyloidosis. In order to demonstrate the importance of bone scanning we will present a few methods of image processing based on literature and a personalized method, followed by a few important examples of positive cases. The aim of this review was to present the current methods of ATTR detection with emphasis on nuclear medicine bone scanning and its important place in the decision algorithm of the cardiologist for a personalized approach to this pathology.

Acquired and inherited amyloidosis: Knowledge driving patients' care

Until recently, systemic amyloidoses were regarded as ineluctably disabling and life-threatening diseases. However, this field has witnessed major advances in the last decade, with significant improvements in therapeutic options and in the availability of accurate and non-invasive diagnostic tools. Outstanding progress includes unprecedented hematological response rates provided by risk-adapted regimens in light chain (AL) amyloidosis and the approval of innovative pharmacological agents for both hereditary and wild-type transthyretin amyloidosis (ATTR). Moreover, the incidence of secondary (AA) amyloidosis has continuously reduced, reflecting advances in therapeutics and overall management of several chronic inflammatory diseases. The identification and validation of novel therapeutic targets has grounded on a better knowledge of key molecular events underlying protein misfolding and aggregation and on the increasing availability of diagnostic, prognostic and predictive markers of organ damage and response to treatment. In this review, we focus on these recent advancements and discuss how they are translating into improved outcomes. Neurological involvement dominates the clinical picture in transthyretin and gelsolin inherited amyloidosis and has a significant impact on disease course and management in all patients. Neurologists, therefore, play a major role in improving patients' journey to diagnosis and in providing early access to treatment in order to prevent significant disability and extend survival.

Cardiac Amyloidosis Presenting as Biventricular Systolic Heart Failure

A previously healthy octogenarian presented with new onset heart failure symptoms. Comprehensive multimodality imaging including complete echocardiography with longitudinal strain analysis, cardiac magnetic resonance imaging (cMRI), nuclear medicine pyrophosphate (99-mcTcPYP) scan along with biomarker, monoclonal protein analysis, and fat pad biopsy confirmed diagnosis of transthyretin cardiac amyloidosis.

Diagnosis and treatment of cardiac amyloidosis: position statement of the German Cardiac Society (DGK)

Systemic forms of amyloidosis affecting the heart are mostly light-chain (AL) and transthyretin (ATTR) amyloidoses. The latter is caused by deposition of misfolded transthyretin, either in wild-type (ATTRwt) or mutant (ATTRv) conformation. For diagnostics, specific serum biomarkers and modern non-invasive imaging techniques, such as cardiovascular magnetic resonance imaging (CMR) and scintigraphic methods, are available today. These imaging techniques do not only complement conventional echocardiography, but also allow for accurate assessment of the extent of cardiac involvement, in addition to diagnosing cardiac amyloidosis. Endomyocardial biopsy still plays a major role in the histopathological diagnosis and subtyping of cardiac amyloidosis. The main objective of the diagnostic algorithm outlined in this position statement is to detect cardiac amyloidosis as reliably and early as possible, to accurately determine its extent, and to reliably identify the underlying subtype of amyloidosis, thereby enabling subsequent targeted treatment.

Cardiac transthyretin amyloidosis 99mTc-DPD SPECT correlates with strain echocardiography and biomarkers

Purpose

Hereditary transthyretin-amyloid amyloidosis (ATTRv) is an underdiagnosed condition commonly manifesting as congestive heart failure. Recently, scintigraphy utilizing DPD as a tracer was shown to identify ATTRv and wild-type ATTR cardiomyopathy. The aim of this study was to determine the value of quantified scintigraphy utilizing ^99mTc-3,3-diphosphono-1,2-propanodicarboxylic acid (DPD) single-photon emission computed tomography (SPECT)/CT, and to correlate its uptake with well-established cardiac functional parameters.

Methods

Forty-eight patients with genetically verified ATTRv type-A fibril composition, positive ^99mTc-DPD SPECT/CT, were retrospectively analyzed. Manual mapping of volumes of interest (VOIs) on DPD SPECT/CT examinations was used to quantify heart uptake. DPD mean and maximum uptake together with a calculated DPD-based amyloid burden (DPD_load) was correlated with echocardiographic strain values and cardiac biomarkers.

Results

Statistically significant correlations were seen in VOIs between DPD uptakes and the corresponding echocardiographic strain values. Furthermore, DPD_load had a strong correlation with echocardiographic strain parameters and also correlated with biomarkers troponin T and logarithmic NT-ProBNP.

Conclusions

In patients with ATTRv cardiomyopathy, DPD SPECT/CT measures the amyloid distribution and provides information on cardiac amyloid load. DPD amyloid load correlates with functional cardiac parameters.

Non-invasive detection and differentiation of cardiac amyloidosis using 99mTc-pyrophosphate scintigraphy and 11C-Pittsburgh compound B PET imaging

PURPOSE

To investigate the utility of the combined use of ¹¹C-Pittsburgh compound B (¹¹C-PiB) positron emission tomography (PET) imaging and ^99mTc-pyrophosphate (^99mTc-PYP) scintigraphy for detection and differentiation of three major types of cardiac amyloidosis, i.e. immunoglobulin light chain (AL), hereditary transthyretin (ATTRv), and wild-type transthyretin (ATTRwt) amyloidosis.

METHODS

Whole-body ¹¹C-PiB PET and ^99mTc-PYP scintigraphy were performed in 17 patients with AL amyloidosis, 22 patients with ATTRv, and eight patients with ATTRwt amyloidosis. The correlations between organ involvement and the uptake of ¹¹C-PiB and ^99mTc-PYP were analyzed in each patient.

RESULTS

Cardiac amyloidosis was detectable by ^99mTc-PYP scintigraphy or ¹¹C-PiB PET in all systemic amyloidosis patients with cardiac involvement. ^99mTc-PYP scintigraphy and ¹¹C-PiB PET showed an interesting complementary relation. Strict combination of positive ¹¹C-PiB and negative ^99mTc-PYP uptake (PiB pattern) was observed in all AL amyloidosis patients with cardiac involvement. In contrast, strict combination of positive ^99mTc-PYP and negative ¹¹C-PiB uptake (PYP pattern) was observed in all ATTRwt amyloidosis patients with cardiac involvement. ATTRv amyloidosis patients with cardiac involvement were divided into two groups: PiB pattern or PYP pattern. All of the early-onset V30M (p.V50M) ATTRv patients showed the PiB pattern, whereas all of the late-onset V30M and non-V30M ATTRv patients showed the PYP pattern.

CONCLUSIONS

All three major types of cardiac amyloidosis can be detected and differentiated non-invasively by combined use of the two amyloid imaging methods and TTR gene testing.

The Role of Multi-modality Imaging in the Diagnosis of Cardiac Amyloidosis: A Focused Update

Cardiac amyloidosis (CA) is a unique disease entity involving an infiltrative process, typically resulting in a restrictive cardiomyopathy with diastolic heart failure that ultimately progresses to systolic heart failure. The two most common subtypes are light-chain and transthyretin amyloidosis. Early diagnosis of this disease entity, especially light-chain CA subtype, is crucial, as it portends a poorer prognosis. This review focuses on the clinical utility of the various imaging modalities in the diagnosis and differentiation of CA subtypes. This review also aims to highlight the key advances in each of the imaging modalities in the diagnosis and prognostication of CA.

Diagnostic value of cardiovascular magnetic resonance in comparison to endomyocardial biopsy in cardiac amyloidosis: a multi-centre study

Background

Cardiac amyloidosis (CA) is an infiltrative disease characterised by accumulation of amyloid deposits in the extracellular space of the myocardium—comprising transthyretin (ATTR) and light chain (AL) amyloidosis as the most frequent subtypes. Histopathological proof of amyloid deposits by endomyocardial biopsy (EMB) is the gold standard for diagnosis of CA. Cardiovascular magnetic resonance (CMR) allows non-invasive workup of suspected CA. We conducted a multi-centre study to assess the diagnostic value of CMR in comparison to EMB for the diagnosis of CA.

Methods

We studied N = 160 patients characterised by symptoms of heart failure and presence of left ventricular (LV) hypertrophy of unknown origin who presented to specialised cardiomyopathy centres in Germany and underwent further diagnostic workup by both CMR and EMB. If CA was diagnosed, additional subtyping based on EMB specimens and monoclonal protein studies in serum was performed. The CMR protocol comprised cine- and late-gadolinium-enhancement (LGE)-imaging as well as native and post-contrast T1-mapping (in a subgroup)—allowing to measure extracellular volume fraction (ECV) of the myocardium.

Results

An EMB-based diagnosis of CA was made in N = 120 patients (CA group) whereas N = 40 patients demonstrated other diagnoses (CONTROL group). In the CA group, N = 114 (95%) patients showed a characteristic pattern of LGE indicative of CA. In the CONTROL group, only 1/40 (2%) patient showed a “false-positive” LGE pattern suggestive of CA. In the CA group, there was no patient with elevated T1-/ECV-values without a characteristic pattern of LGE indicative of CA. LGE-CMR showed a sensitivity of 95% and a specificity of 98% for the diagnosis of CA. The combination of a characteristic LGE pattern indicating CA with unremarkable monoclonal protein studies resulted in the diagnosis of ATTR-CA (confirmed by EMB) with a specificity of 98% [95%-confidence interval (CI) 92–100%] and a positive predictive value (PPV) of 99% (95%-CI 92–100%), respectively. The EMB-associated risk of complications was 3.13% in this study—without any detrimental or persistent complications.

Conclusion

Non-invasive CMR shows an excellent diagnostic accuracy and yield regarding CA. When combined with monoclonal protein studies, CMR can differentiate ATTR from AL with high accuracy and predictive value. However, invasive EMB remains a safe invasive gold-standard and allows to differentiate CA from other cardiomyopathies that can also cause LV hypertrophy.

Electronic supplementary material

The online version of this article (10.1007/s00392-020-01771-1) contains supplementary material, which is available to authorized users.

Role of Nuclear Imaging in Cardiac Amyloidosis Management: Clinical Evidence and Review of Literature

Cardiac amyloidosis (CA) is an infiltrative disease characterized by the extracellular deposition of fibrils, amyloid, in the heart. The vast majority of patients with CA has one of two types between transthyretin amyloid (ATTR) and immunoglobulin light chain associated amyloid (AL), that have different prognosis and therapeutic options. CA is often underdiagnosed. The histological analysis of endomyocardial tissue is the gold standard for the diagnosis, although it has its limitations due to its invasive nature. Nuclear medicine now plays a key role in the early and accurate diagnosis of this disease, and in the ability to distinguish between the two forms. Recent several studies support the potential advantage of bone-seeking radionuclides as a screening technique for the most common types of amyloidosis, in particular ATTR form. This review presents noninvasive modalities to diagnose CA and focuses on the radionuclide imaging techniques (bone-seeking agents scintigraphy, cardiac sympathetic innervation and positron emission tomography studies) available to visualize myocardial amyloid involvement. Furthermore, we report the case of an 83-year old male with a history of prostate cancer, carcinoma of the cecum and kidney cancer, submitted to bone scan to detect bone metastasis, that revealed a myocardial uptake of 99mTC-HMPD suggestive of ATTR CA. An accurate and early diagnosis of CA able to distinguish beyween AL and ATTR CA combined to the improving therapies could improve the survival of patients with this disease.

Abdominal fat pad biopsies exhibit good diagnostic accuracy in patients with suspected transthyretin amyloidosis

Background

The diagnostic accuracy of histopathological detection of transthyretin amyloid (ATTR) by Congo red staining of abdominal fat samples has been questioned since low sensitivity has been reported, especially for patients with ATTR cardiomyopathy. However, the outcome of surgically obtained fat pad biopsies has not yet been evaluated. The aim was to evaluate the diagnostic accuracy of skin punch biopsies from abdominal fat in patients with suspected ATTR amyloidosis.

Material and methods

Data were evaluated from patients who had undergone abdominal fat pad biopsies using a skin punch due to suspected amyloidosis from 2006 to 2015. The biopsies had been analysed using Congo red staining to determine the presence of amyloid, and immunohistochemistry or Western blot to determine the type of amyloidosis. The final diagnosis was based on the clinical picture, biopsy results and DNA sequencing. Minimum follow-up after the initial biopsy was 3 years.

Results

Two hundred seventy-four patients (61% males) were identified, and in 132 (48%), a final diagnosis of amyloidosis had been settled. The majority (93%) had been diagnosed with hereditary transthyretin (ATTRv) amyloidosis, and therefore subsequent analyses were focused on these patients. Overall, our data showed a test specificity of 99% and a sensitivity of 91%. Ninety-eight (94%) of the patients had neuropathic symptoms at diagnosis, whereas 57 (55%) had signs of amyloid cardiomyopathy. Subgroup analyses showed that patients with merely neuropathic symptoms displayed the highest test sensitivity of 91%, whereas patients with pure cardiomyopathy displayed the lowest sensitivity of 83%. However, no significant differences in sensitivity were found between patients with or without cardiomyopathy or between the sexes.

Conclusions

Abdominal fat pad biopsies exhibit good diagnostic accuracy in patients with suspect ATTRv amyloidosis, including patients presenting with cardiomyopathy. In addition, the method enables typing not only of the precursor protein but also of the amyloid fibril type, which is related to the phenotype and to the outcome of the disease.

The sensitivity of DPD scintigraphy to detect transthyretin cardiac amyloidosis in V30M mutation depends on the phenotypic expression of the disease

Background: There is a growing need for a non-invasive test to detect cardiac involvement in patients with transthyretin-related hereditary amyloidosis (ATTR) caused by V30M mutation. ^99mTc-3,3-diphosphono-1,2-propanodicarboxylic acid (DPD) scintigraphy is a promising method, but its accuracy in this particular mutation remains unknown.Methods: A cohort of 179 patients: 92 with early-onset disease (EoD, symptoms <50-years-old), 33 with late-onset disease (LoD) and 54 asymptomatic carriers were prospectively evaluated and underwent DPD scintigraphy, which was compared with the results of echocardiogram, ambulatory blood pressure monitoring, 24 h-Holter, myocardial ¹²³I-metaiodobenzylguanidine imaging and NT-proBNP.Results: Amyloid cardiomyopathy, defined as septal thickness ≥13 mm, was present in 32 patients (17.9%) and was more frequent in those with LoD (OR: 3.68, p = .003). Cardiac DPD uptake was present in 22 individuals (12.3%) and correlated with parameters indicative of cardiac amyloidosis. DPD imaging was strongly influenced by the age of disease onset: among patients with myocardial thickening, cardiac DPD retention was present in 11/15 (73.3%) with LoD, in contrast to only 4/17 (26.7%) with EoD (p = .005). Two patients with myocardial thickening and normal DPD scintigraphy underwent endomyocardial biopsy that confirmed ATTR amyloidosis.Conclusion: DPD scintigraphy presents suboptimal sensitivity to detect cardiac involvement in ATTRV30M, particularly in symptomatic patients with EoD.

Quantification of cardiac amyloid with [18F]Flutemetamol in patients with V30M hereditary transthyretin amyloidosis

Background: Hereditary transthyretin amyloid (ATTRv) is a systemic amyloidosis with mainly neurological and cardiac symptoms. The aim of this study was to evaluate the outcome of [¹⁸F]Flutemetamol PET/CT-scan of the heart in long-term survivors with ATTRV30M amyloidosis.Methods: Twenty-one patients with ATTRV30M amyloidosis and predominantly neurological symptoms, mainly negative on cardiac ^99mtechnetium-3,3-diphosphono-1,2-propanodicarboxylic acid (DPD)-scintigraphy, were examined with a dynamic [¹⁸F]Flutemetamol PET/CT-scan. Five patients suffering from Alzheimer's disease and one healthy individual served as controls. Volumes of interests were drawn over the intraventricular septum, lateral wall of the left ventricle and free wall of the right ventricle. Clinical records were reviewed for data from previous completed DPD-scintigraphy of the heart and echocardiography.Results: Patients with ATTRv amyloidosis had a higher cardiac uptake than the control-group in all analysed regions of the heart and could be identified with high accuracy (sensitivity 88%, specificity 100%) in static image acquisition at 30 or 60 min. We found no correlation between cardiac [¹⁸F]Flutemetamol uptake and clinical variables.Conclusion: In this small study of selected patients, cardiac [¹⁸F]Flutemetamol PET/CT could differentiate between healthy individuals and patients with ATTRV30M. [¹⁸F]Flutemetamol PET/CT imaging of amyloidosis in patients with a negative DPD-scintigraphy has a potential as a diagnostic method.

Amyloidosis in Heart Failure

PURPOSE

Amyloidosis represents an increasingly recognized but still frequently missed cause of heart failure. In the light of many effective therapies for light chain (AL) amyloidosis and promising new treatment options for transthyretin (ATTR) amyloidosis, awareness among caregivers needs to be raised to screen for amyloidosis as an important and potentially treatable differential diagnosis. This review outlines the diversity of cardiac amyloidosis, its relation to heart failure, the diagnostic algorithm, and therapeutic considerations that should be applied depending on the underlying type of amyloidosis.

RECENT FINDINGS

Non-biopsy diagnosis is feasible in ATTR amyloidosis in the absence of a monoclonal component resulting in higher detection rates of cardiac ATTR amyloidosis. Biomarker-guided staging systems have been updated to facilitate risk stratification according to currently available biomarkers independent of regional differences, but have not yet prospectively been tested. Novel therapies for hereditary and wild-type ATTR amyloidosis are increasingly available. The complex treatment options for AL amyloidosis are improving continuously, resulting in better survival and quality of life. Mortality in advanced cardiac amyloidosis remains high, underlining the importance of early diagnosis and treatment initiation. Cardiac amyloidosis is characterized by etiologic and clinical heterogeneity resulting in a frequently delayed diagnosis and an inappropriately high mortality risk. New treatment options for this hitherto partially untreatable condition have become and will become available, but raise challenges regarding their implementation. Referral to specialized centers providing access to extensive and targeted diagnostic investigations and treatment initiation may help to face these challenges.

Cardiac scintigraphy with 99mTc-diphosphonates in cardiac amyloidosis

Transthyretin cardiac amyloidosis (ATTR) has traditionally been considered a rare, difficult-to-diagnose and untreatable disease. However, its prevalence is known to be greater than what was previously thought, non-invasive diagnostic methods are available, and that effective treatments are emerging. In this context, cardiac scintigraphy (CS) with ^99mTc-labelled diphosphonates has aroused a noticeable surge in interest by demonstrating high sensitivity and specificity for the reliable, non-invasive diagnosis of ATTR. By way of a guide, this article aims to identify the critical components in the performance of CS that are useful in everyday clinical practice and, thus, help specialists use optimal radiopharmaceuticals, obtain the most appropriate images, interpret the results thereof, and acquaint themselves with those clinical scenarios in which it is convenient to perform CS.