Current perspectives on cardiac amyloidosis

Artificial intelligence based left ventricular ejection fraction and global longitudinal strain in cardiac amyloidosis

BACKGROUND

Assessment of left ventricular ejection fraction (LVEF) and global longitudinal strain (GLS) plays a key role in the diagnosis of cardiac amyloidosis (CA). However, manual measurements are time consuming and prone to variability. We aimed to assess whether fully automated artificial intelligence (AI) calculation of LVEF and GLS provide similar estimates and can identify abnormalities in agreement with conventional manual methods, in patients with pre-clinical and clinical CA.

METHODS

We identified 51 patients (age 80 ± 10 years, 53% male) with confirmed CA according to guidelines, who underwent echocardiography before and/or at the time of CA diagnosis (median (IQR) time between observations 3.87 (1.93, 5.44 years). LVEF and GLS were quantified from the apical 2- and 4-chamber views using both manual and fully automated methods (EchoGo Core 2.0, Ultromics). Inter-technique agreement was assessed using linear regression and Bland-Altman analyses and two-way ANOVA. The diagnostic accuracy and time for detecting abnormalities (defined as LVEF ≤ 50% and GLS ≥ -15.1%, respectively) using AI was assessed by comparisons to manual measurements as a reference.

RESULTS

There were no significant differences in manual and automated LVEF and GLS values in either pre-CA (p = .791 and p = .105, respectively) or at diagnosis (p = .463 and p = .722). The two methods showed strong correlation on both the pre-CA (r = .78 and r = .83) and CA echoes (r = .74 and r = .80) for LVEF and GLS, respectively. The sensitivity and specificity of AI-derived indices for detecting abnormal LVEF were 83% and 86%, respectively, in the pre-CA echo and 70% and 79% at CA diagnosis. The sensitivity and specificity of AI-derived indices for detecting abnormal GLS was 82% and 86% in the pre-CA echo and 100% and 67% at the time of CA diagnosis. There was no significant difference in the relationship between LVEF (p = .99) and GLS (p = .19) and time to abnormality between the two methods.

CONCLUSION

Fully automated AI-calculated LVEF and GLS are comparable to manual measurements in patients pre-CA and at the time of CA diagnosis. The widespread implementation of automated LVEF and GLS may allow for more rapid assessment in different disease states with comparable accuracy and reproducibility to manual methods.

Physiology, Diagnosis and Treatment of Cardiac Light Chain Amyloidosis

AL (light-chain) amyloidosis is a systemic disease in which amyloid fibers are formed from kappa or lambda immunoglobulin light chains, or fragments thereof, produced by a neoplastic clone of plasmocytes. The produced protein is deposited in tissues and organs in the form of extracellular deposits, which leads to impairment of their functions and, consequently, to death. Despite the development of research on pathogenesis and therapy, the mortality rate of patients with late diagnosed amyloidosis is 30%. The diagnosis is delayed due to the complex clinical picture and the slow progression of the disease. This is the type of amyloidosis that most often contributes to cardiac lesions and causes cardiac amyloidosis (CA). Early diagnosis and correct identification of the type of amyloid plays a crucial role in the planning and effectiveness of therapy. In addition to standard histological studies based on Congo red staining, diagnostics are enriched by tests to determine the degree of cardiac involvement. In this paper, we discuss current diagnostic methods used in cardiac light chain amyloidosis and the latest therapies that contribute to an improved patient prognosis.

Contemporary narrative review on left atrial strain mechanics in echocardiography: cardiomyopathy, valvular heart disease and beyond

Left atrial (LA) strain mechanics refer to the measurement of LA myocardial deformation expressed as a percentage, and have been gathering interest over the last decade with expanding research supporting their utility in multiple cardiovascular disorders. Measured through advanced dynamic imaging techniques which include tissue Doppler imaging (TDI) and two-dimensional (2D) speckle tracking echocardiography (STE), LA strain mechanics are affected by left ventricular diastolic dysfunction prior to the onset of functional and structural changes in the left ventricle (LV). There is a need for practising cardiologists to become more familiar with the clinical utility of LA strain mechanics. In this article, we begin by reviewing the physiologic function of the LA, using this as a basis for understanding LA strain mechanics. The focus of this review article is to provide a contemporary update on the utility of LA strain mechanics in a range of cardiovascular disorders, including atrial fibrillation (AF), hypertrophic cardiomyopathy (HCM), valvular pathologies, coronary artery disease (CAD) as well as systemic diseases, such as hypertension (HTN), obesity and diabetes mellitus (DM). This article also highlights the current limitations in more widespread clinical applications of LA strain mechanics, as well as outlining the future perspectives on the clinical applications of LA strain mechanics.

Mechanisms and Potential Treatment Options of Heart Failure in Patients With Multiple Myeloma

Multiple myeloma is a pathology of plasma cells, with one of the most common side effects of its treatment is heart failure. In addition, cardiac amyloidosis could cause heart failure by itself. Even though mechanisms of cardiac amyloidosis are known, and they involve lysosomal dysfunction, reactive oxygen species (ROS) accumulation, and infiltrative effect by fibrils, there is no specific agent that could protect from these effects. While the molecular mechanism of doxorubicin cardiotoxicity via topoisomerase II β is established, the only FDA-approved agent for treatment is dexrazoxane. Liposomal doxorubicin can potentially improve response and decrease the development of heart failure due to microscopic liposomes that can accumulate and penetrate only tumor vasculature. Supplements that enhance mitochondrial biogenesis are also shown to improve doxorubicin-induced cardiotoxicity. Other agents, such as JR-311, ICRF-193, and ursolic acid, could potentially become new treatment options. Proteasome inhibitors, novel agents, have significantly improved survival rates among multiple myeloma patients. They act on a proteasome system that is highly active in cardiomyocytes and activates various molecular cascades in malignant cells, as well as in the heart, through nuclear factor kappa B (NF-kB), endoplasmic reticulum (ER), calcineurin-nuclear factor of activated T-cells (NFAT), and adenosine monophosphate-activated protein kinase (AMPKa)/autophagy pathways. Metformin, apremilast, and rutin have shown positive results in animal studies and may become a promising therapy as cardioprotective agents. This article aims to highlight the main molecular mechanisms of heart failure among patients with multiple myeloma and potential treatment options to facilitate the development and research of new preventive strategies. Hence, this will have a positive impact on life expectancy in patients with multiple myeloma.

The long and winding road to target protein misfolding in cardiovascular diseases

BACKGROUND

In the last decades, cardiovascular diseases (CVD) have remained the first leading cause of mortality and morbidity in the world. Although several therapeutic approaches have been introduced in the past, the development of novel treatments remains an important research goal, which is hampered by the lack of understanding of key mechanisms and targets. Emerging evidences in recent years indicate the involvement of misfolded proteins aggregation and the derailment of protein quality control in the pathogenesis of cardiovascular diseases. Several potential interventions targeting protein quality control have been translated from the bench to the bedside to effectively employ the misfolded proteins as promising therapeutic targets for cardiac diseases, but with trivial results.

DESIGN

In this review, we describe the recent progresses in preclinical and clinical studies of protein misfolding and compromised protein quality control by selecting and reporting studies focusing on cardiovascular diseases including cardiomyopathies, cardiac amyloidosis, atherosclerosis, atrial fibrillation and thrombosis.

RESULTS

In preclinical models, modulators of several molecular targets (eg heat shock proteins, unfolded protein response, ubiquitin protein system, autophagy and histone deacetylases) have been tested in various conditions with promising results although lacking an adequate transition towards clinical setting.

CONCLUSIONS

At present, no therapeutic strategies have been reported to attenuate proteotoxicity in patients with CVD due to a lack of specific biomarkers for pinpointing upstream events in protein folding defects at a subclinical stage of the diseases requiring an intensive collaboration between basic scientists and clinicians.

The Role of Light Kappa and Lambda Chains in Heart Function Assessment in Patients with AL Amyloidosis

There are reports indicating that myocardial dysfunction in systemic immunoglobulin light chain amyloidosis (AL amyloidosis) stems not only from the amyloid deposit in the organ but also the cardiotoxicity of the amyloid precursor free light chains (FLCs) circulating in the blood. The aim of the study is to analyze the role of sFLC κ and λ in the assessment of heart involvement and the degree of myocardial damage in AL amyloidosis. The study involved 71 patients diagnosed with primary AL amyloidosis. The relationship between sFLC concentrations and cardiac biochemical and echocardiographic parameters was assessed. The median concentrations of N-terminal pro b-type natriuretic peptide(NT-proBNP) and troponin I (TnI) were significantly higher in patients with amyloids formed from monoclonal λ chains compared to patients with monoclonal κ proliferation. In patients with heart involvement by amyloids formed from monoclonal FLC, the study demonstrated a statistically significant positive correlation between the concentration of monoclonal antibody λ chain and TnI (R = 0.688; p < 0.05), NT-proBNP (R = 0.449; p < 0.05), and the value of diastolic dimension of the interventricular septum (IVS; R = 0.496, p < 0.05). The above data indicate that the presence of monoclonal λ chains in patients with AL amyloidosis may be associated with more severe damage to cardiomyocytes and dysfunction of the myocardium.

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.

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.

Cardiac Amyloidosis Detected on Imaging of Patients with Heart Failure

Case series

Patients: Male, 63-year-old • Female, 72-year-old • Female, 55-year-old

Final Diagnosis: Amyloid light-chain amyloidosis • cardiac amyloidosis • cardiomyopathy • heart failure • primary AL amyloidosis

Symptoms: Aphasia • dyspnea • heart failure • thrombosis • tongue mass

Medication: —

Clinical Procedure: Biopsy • chemotherapy • echocardiography

Specialty: Cardiology • Hematology

Right Heart Changes Impact on Clinical Phenotype of Amyloid Cardiac Involvement: A Single Centre Study

Amyloidosis is due to deposition of an excessive amount of protein in many parenchymal tissues, including myocardium. The onset of cardiac Amyloidosis (CA) is an inauspicious prognostic factor, which can lead to sudden death. We retrospectively analyzed 135 patients with systemic amyloidosis, admitted to our ward between 1981 and 2019. Among them, 54 patients (46.30% F/53.70% M, aged 63.95 ± 12.82) presented CA at baseline. In 53 patients, it was associated with a multiorgan involvement, while in one there was a primary myocardial deposition. As a control group, we enrolled 81 patients (49.30% F/50.70% M, aged 58.33 ± 15.65) who did not meet the criteria for CA. In 44/54 of patients CA was associated with AL, 5/54 with AA and 3/54 of patients with ATTR, and in 1/54 AL was related to hemodialysis and in 1/54 to Gel-Amyloidosis. The most common AL type was IgG (28/44); less frequent forms were either IgA (7/44) or IgD (2/44), while seven patients had a λ free light chain form. The 32 AL with complete Ig were 31 λ-chain and just one k-chain. CA patients presented normal BP (SBP 118.0 ± 8.4 mmHg; DBP 73.8 ± 4.9 mmHg), while those with nCA had an increased proteinuria (p = 0.02). TnI and NT-proBNP were significantly increased compared to nCA (p = 0.031 and p = 0.047, respectively). In CA patients we found an increased LDH compared to nCA (p = 0.0011). CA patients were also found to have an increased interventricular septum thickness compared to nCA (p = 0.002), a decreased Ejection Fraction % (p = 0.0018) and Doppler velocity E/e’ ratio (p = 0.0095). Moreover, CA patients had an enhanced right atrium area (p = 0.0179), right ventricle basal diameter (p = 0.0112) and wall thickness (p = 0.0471) compared to nCA, and an increased inferior cava vein diameter (p = 0.0495) as well. TAPSE was the method chosen to evaluate systolic function of the right heart. In CA subjects very poor TAPSE levels were found compared to nCA patients (p = 0.0495). Additionally, we found a significant positive correlation between TAPSE and lymphocyte count (r = 0.47; p = 0.031) as well as Gamma globulins (r = 0.43, p = 0.033), Monoclonal components (r = 0.72; p = 0.047) and IgG values (r = 0.62, p = 0.018). Conversely, a significant negative correlation with LDH (r = −0.57, p = 0.005), IVS (r = −0.51, p = 0.008) and diastolic function evaluated as E/e’ (r = −0.60, p = 0.003) were verified. CA patients had very poor survival rates compared to controls (30 vs. 66 months in CA vs. nCA, respectively, p = 0.15). Mean survival of CA individuals was worse also when stratified according to NT-proBNP levels, using 2500 pg/mL as class boundary (174 vs. 5.5 months, for patients with lower vs. higher values than the median, respectively p = 0.013). In much the same way, a decreased right heart systolic function was correlated with a worse prognosis (18.0 months median survival, not reached in subjects with lower values than 18 mm, p = 0.0186). Finally, our data highlight the potential prognostic and predictive value of right heart alterations characterizing amyloidosis, as a novel clinical parameter correlated to increased LDH and immunoglobulins levels. Overall, we confirm the clinical relevance of cardiac involvement suggests that right heart evaluation may be considered as a new marker for clinical risk stratification in patients with amyloidosis.

Left ventricular global function index by magnetic resonance imaging - a novel marker for differentiating cardiac amyloidosis from hypertrophic cardiomyopathy

Differentiating cardiac amyloidosis (CA) from hypertrophic cardiomyopathy (HCM) remains a clinical challenge, particularly in those with preserved left ventricular ejection fraction (LVEF) and similar hypertrophy. This study aimed to use left ventricular global function index (LVGFI) and myocardial contraction fraction (MCF) to discriminate CA from HCM without using contrast agents on cardiovascular magnetic resonance imaging (CMR). In total, we included 68 CA patients, 90 HCM patients, and 35 healthy controls. We found that LVGFI had excellent diagnostic performance in differentiating CA from HCM (area under the curve (AUC) = 0.91, 95% CI [0.86-0.95]), even in the challenging conditions of similar hypertrophy (AUC = 0.92, 95% CI [0.87-0.97]) and preserved LVEF (AUC = 0.90, 95% CI [0.84-0.96]). LVGFI also had significant correlations with LGE extent, NT-proBNP and troponin T (all p < 0.001). Multiple logistic regression analysis revealed that LVGFI was an independent predictor of CA (odds ratio: 1.11, 95% CI: 1.01-1.23; p = 0.034). In conclusion, LVGFI is a novel and clinically useful parameters with excellent ability in determining myocardial function and differentiating cardiac amyloidosis from hypertrophic cardiomyopathy.

Mechanistic Insights into the Early Events in the Aggregation of Immunoglobulin Light Chains

Little is known about the mechanism of amyloid assembly in immunoglobulin light chain (AL) amyloidosis, in contrast to other amyloid diseases. Early events in the aggregation pathway are especially important, as these soluble species could be cytotoxic intermediates playing a critical role in the initiation of the amyloid assembly. In this work, we discuss the mechanism of the early events in in vitro fibril formation of immunoglobulin light chain AL-09 and AL-12 (involved in cardiac amyloidosis) and its germline (control) protein κI O18/O8. Previous work from our laboratory showed that AL-12 adopts a canonical dimer conformation (like the germline protein), whereas AL-09 presents an altered dimer interface as a result of somatic mutations. Both AL-12 and AL-09 aggregate with similar rates and significantly faster than the germline protein. AL-09 is the only protein in this study that forms stable oligomeric intermediates during the early stages of the aggregation reaction with some structural rearrangements that increase the thioflavin T fluorescence but maintain the same number of monomers in solution. The presence of the restorative mutation AL-09 H87Y changes the kinetics and the aggregation pathway compared to AL-09. The single restorative mutation AL-12 R65S slightly delayed the overall rate of aggregation as compared to AL-12. Collectively, our study provides a comprehensive analysis of species formed during amyloid nucleation in AL amyloidosis, shows a strong dependence between the altered dimer conformation and the formation of stable oligomeric intermediates, and sheds light on the structural features of amyloidogenic intermediates associated with cellular toxicity.

Predictors of Mortality in Light Chain Cardiac Amyloidosis with Heart Failure

Cardiac involvement in systemic amyloidosis (AL) occurs in ~50% of all AL patients. However once symptomatic heart failure develops, therapeutic options are limited thereby conferring a poor overall prognosis. The median survival is <6 months when AL patients are untreated for the underlying plasma cell dyscrasia. We thus sought to identify risk factors of increased mortality in treatment-naïve, AL cardiac amyloidosis with heart failure. Patients with biopsy-proven AL cardiac amyloid, who presented with heart failure and did not received prior AL treatment, were enrolled between 2004–2014, at the initial visit to the Amyloidosis Center at Boston University Medical Center. Routine laboratory tests, physical examination and echocardiography data were collected. There were 165 predominantly white (76.4%), and male (61%) patients, with a mean age of 61.6 ± 9.5 years. Median survival was 10.9 months (95% CI 6.2–14.7). By multivariate analysis increased relative wall thickness (RWT) [HR 6.70; 95% CI 2.45–18.30), older age (HR 1.04; 95% CI 1.01–1.06), higher New York Heart Association (NYHA) functional class (HR 1.50; 95% CI 1.02–2.2), log brain natriuretic peptide (BNP) levels (HR 1.45; 95% CI 1.15–1.81) and C-reactive protein (CRP) levels (HR 1.02; 95% CI 1.00–1.04) were significant predictors for increased mortality. In conclusion, in treatment-naïve, AL cardiac amyloidosis patients with heart failure symptoms who lack these high-risk features may have a better outcome. These findings might allow for better risk stratification although outcomes are still poor.

Role of cardiovascular imaging for the diagnosis and prognosis of cardiac amyloidosis

Cardiac amyloidosis (CA) describes the pathological process of amyloid protein deposition in the extracellular space of the myocardium. Unfortunately, the diagnosis of CA is often made late and when the disease process is advanced. However, advances in cardiovascular imaging have allowed for better prognostication and establishing diagnostic pathways with high sensitivity and specificity. This review discusses the role of echocardiography, cardiac MRI and nuclear cardiology in current clinical practice for diagnosis and prognosis of CA.

Coronary Microcirculatory Dysfunction in Human Cardiomyopathies: A Pathologic and Pathophysiologic Review

Cardiomyopathies are a heterogeneous group of diseases of the myocardium. The term cardiomyopathy involves a wide range of pathogenic mechanisms that affect the structural and functional states of cardiomyocytes, extravascular tissues, and coronary vasculature, including both epicardial coronary arteries and the microcirculation. In the developed phase, cardiomyopathies present with various clinical symptoms: dyspnea, chest pain, palpitations, swelling of the extremities, arrhythmias, and sudden cardiac death. Due to the heterogeneity of cardiomyopathic patterns and symptoms, their diagnosis and therapies are great challenges. Despite extensive research, the relation between the structural and functional abnormalities of the myocardium and the coronary circulation are still not well understood in the various forms of cardiomyopathy. The main pathological characteristics of cardiomyopathies and the coronary microcirculation develop in a progressive manner due to (1) genetic-immunologic-systemic factors; (2) comorbidities with endothelial, myogenic, metabolic, and inflammatory changes; (3) aging-induced arteriosclerosis; and (4) myocardial fibrosis. The aim of this review is to summarize the most important common pathological features and/or adaptations of the coronary microcirculation in various types of cardiomyopathies and to integrate the present understanding of the underlying pathophysiological mechanisms responsible for the development of various types of cardiomyopathies. Although microvascular dysfunction is present and contributes to cardiac dysfunction and the potential outcome of disease, the current therapeutic approaches are not specific for the given types of cardiomyopathy.

Amyloid Properties of Titin

This review considers data on structural and functional features of titin, on the role of this protein in determination of mechanical properties of sarcomeres, and on specific features of regulation of the stiffness and elasticity of its molecules, amyloid aggregation of this protein in vitro, and possibilities of formation of intramolecular amyloid structure in vivo. Molecular mechanisms are described of protection of titin against aggregation in muscle cells. Based on the data analysis, it is supposed that titin and the formed by it elastic filaments have features of amyloid.

Monoclonal gammopathy of undetermined significance in systemic transthyretin amyloidosis (ATTR)

OBJECTIVE

To identify the prevalence of monoclonal gammopathy of undetermined significance (MGUS) in patients with transthyretin (ATTR) amyloidosis.

PATIENTS AND METHODS

We performed a retrospective analysis of patients with biopsy-proven ATTRwt (wild-type transthyretin amyloid protein) and genopositive ATTR V122I (valine-to-isoleucine substitution at position 122 of the TTR gene) amyloidosis evaluated at the Amyloidosis Center at Boston University and Boston Medical Center between 1 January 2003 and 31 December 2016.

RESULTS

There were a total of 226 patients with ATTRwt and ATTR V122I amyloidosis evaluated during the specified time frame with 155 and 71 patients in each cohort, respectively. Those with complete medical records, 140 patients with ATTRwt and 57 V1221 ATTRm subjects, were included in the analyses. Fifty-five patients (39%) in the ATTRwt cohort and 28 patients (49%) in the ATTR V122I cohort had an MGUS, as indicated by an abnormality in the serum-free light-chain ratio and/or serum immunofixation electrophoresis.

CONCLUSION

These data confirm the high prevalence of coexistent MGUS with ATTR amyloidosis in this patient population, with an MGUS rate that is higher than the general population. These findings also highlight the importance of a thorough diagnostic evaluation in patients with amyloidosis to determine the precursor protein, as the clinical course and treatment of AL (light-chain amyloid protein) and ATTR amyloidosis are distinct.

Cardiac amyloidosis is associated with increased aortic stiffness

OBJECTIVE

Cardiac amyloidosis (CA) is as an infiltrative disorder primarily caused by extracellular tissue deposition of amyloid fibrils in the myocardial interstitium. The current study was designed to test whether alterations in ascending aortic elastic properties could be detected by echocardiography in CA patients, and to compare their results to controls.

PATIENTS AND METHODS

We included 19 CA patients from which CA proved to be AL amyloidosis in 17 cases and transthyretin (TTR) amyloidosis in 2 cases. Their results were compared to 20 age-, gender-, and risk factor-matched controls.

RESULTS

There was significantly greater interventricular septum and left ventricular (LV) posterior wall thickness, lower LV ejection fraction and greater E/A in CA patients than in controls, suggesting systolic, and diastolic dysfunction. CA patients also showed significantly reduced aortic strain and pulsatile change in aortic diameter, and increased aortic stiffness index.

CONCLUSION

These results suggest increased aortic stiffness in CA patients.

Impact of flow, gradient, and left ventricular function on outcomes after transcatheter aortic valve replacement

OBJECTIVES

To assess the impact of low flow with and without preserved left ventricular ejection fraction (LVEF) on outcomes after transcatheter aortic valve replacement (TAVR).

BACKGROUND

Prior studies have shown that patients with low flow, AVG, and LVEF have worse outcomes after TAVR. It is unclear whether low AVG and LVEF remain prognostic after adjusting for flow, and how the outcomes of patients with low flow with and without preserved LVEF compare after TAVR. The goal of this study was to provide insight into these open questions.

METHODS

Data from 340 TAVR patients at Brigham and Women's Hospital from 2011 through 2015 were analyzed. Low flow was defined as stroke volume index (SVI) ≤35 mL/m² , low AVG as mean gradient < 40 mmHg, and reduced LVEF as < 50%.

RESULTS

Low flow was present in 96 (28.2%) patients, 48 (50.0%) of whom also had reduced LVEF. At 1 year, low flow was associated with increased mortality (21.9 vs 7.4%; P = 0.0002) and heart failure (HF) (20.8 vs 5.3%; P = 0.0113). Among patients with low flow, those with preserved LVEF had increased mortality (HR 5.17, 95% CI 2.73-9.80; P < 0.001) and HF (HR 7.69, 95% CI 3.86-15.31; P < 0.001). After adjusting for clinical factors, patients with low flow had increased mortality (HR 6.51, 95% CI 2.98-14.22; P < 0.001) and HF (HR 5.52, 95% CI 2.34-12.98; P < 0.001), while neither low AVG nor low LVEF were associated with increases in mortality or HF.

CONCLUSIONS

In patients undergoing TAVR, low flow was an independent predictor of 1-year mortality and HF, and a stronger predictor than either low AVG or LVEF. Patients with low flow and preserved EF had increased mortality and HF at 1-year, while those with low flow and reduced EF had outcomes similar to patients with normal flow.

A Peptide-Fc Opsonin with Pan-Amyloid Reactivity

There is a continuing need for therapeutic interventions for patients with the protein misfolding disorders that result in systemic amyloidosis. Recently, specific antibodies have been employed to treat AL amyloidosis by opsonizing tissue amyloid deposits thereby inducing cell-mediated dissolution and organ improvement. To develop a pan-amyloid therapeutic agent, we have produced an Fc-fusion product incorporating a peptide, p5, which binds many if not all forms of amyloid. This protein, designated Fcp5, expressed in mammalian cells, forms the desired bivalent dimer structure and retains pan-amyloid reactivity similar to the p5 peptide as measured by immunosorbent assays, immunohistochemistry, surface plasmon resonance, and pulldown assays using radioiodinated Fcp5. Additionally, Fcp5 was capable of opsonizing amyloid fibrils in vitro using a pH-sensitive fluorescence assay of phagocytosis. In mice,¹²⁵ I-labeled Fcp5 exhibited an extended serum circulation time, relative to the p5 peptide. It specifically bound AA amyloid deposits in diseased mice, as evidenced by biodistribution and microautoradiographic methods, which coincided with an increase in active, Iba-1-positive macrophages in the liver at 48 h postinjection of Fcp5. In healthy mice, no specific tissue accumulation was observed. The data indicate that polybasic, pan-amyloid-targeting peptides, in the context of an Fc fusion, can yield amyloid reactive, opsonizing reagents that may serve as next-generation immunotherapeutics.

Lipopolysaccharide-binding protein (LBP) reverses the amyloid state of fibrin seen in plasma of type 2 diabetics with cardiovascular co-morbidities

Type 2 diabetes (T2D) has many cardiovascular complications, including a thrombotic propensity. Many such chronic, inflammatory diseases are accompanied (and may be exacerbated, and possibly even largely caused) by amyloid fibril formation. Recognising that there are few strong genetic associations underpinning T2D, but that amyloidogenesis of amylin is closely involved, we have been seeking to understand what might trigger the disease. Serum levels of bacterial lipopolysaccharide are raised in T2D, and we recently showed that fibrin(ogen) polymerisation during blood clotting can be affected strongly by LPS. The selectivity was indicated by the regularisation of clotting by lipopolysaccharide-binding protein (LBP). Since coagulopathies are a hallmark of T2D, we wondered whether they might too be caused by LPS (and reversed by LBP). We show here, using SEM and confocal microscopy, that platelet-poor-plasma from subjects with T2D had a much greater propensity for hypercoagulability and for amyloidogenesis, and that these could both be reversed by LBP. These data imply that coagulopathies are an important feature of T2D, and may be driven by ‘hidden’ LPS. Given the prevalence of amyloid formation in the sequelae of diabetes, this opens up novel strategies for both the prevention and treatment of T2D.

Cardiac Amyloidosis and its New Clinical Phenotype: Heart Failure with Preserved Ejection Fraction

Heart failure with preserved ejection fraction (HFpEF) is now an emerging cardiovascular epidemic, being identified as the main phenotype observed in clinical practice. It is more associated with female gender, advanced age and comorbidities such as hypertension, diabetes, obesity and chronic kidney disease. Amyloidosis is a clinical disorder characterized by the deposition of aggregates of insoluble fibrils originating from proteins that exhibit anomalous folding. Recently, pictures of senile amyloidosis have been described in patients with HFpEF, demonstrating the need for clinical cardiologists to investigate this etiology in suspect cases. The clinical suspicion of amyloidosis should be increased in cases of HFPS where the cardio imaging methods are compatible with infiltrative cardiomyopathy. Advances in cardio imaging methods combined with the possibility of performing genetic tests and identification of the type of amyloid material allow the diagnosis to be made. The management of the diagnosed patients can be done in partnership with centers specialized in the study of amyloidosis, which, together with the new technologies, investigate the possibility of organ or bone marrow transplantation and also the involvement of patients in clinical studies that evaluate the action of the new emerging drugs.

Amyloid β-Sheet Secondary Structure Identified in UV-Induced Cataracts of Porcine Lenses using 2D IR Spectroscopy

Cataracts are formed by the aggregation of crystallin proteins in the eye lens. Many in vitro studies have established that crystallin proteins precipitate into aggregates that contain amyloid fibers when denatured, but there is little evidence that ex vivo cataracts contain amyloid. In this study, we collect two-dimensional infrared (2D IR) spectra on tissue slices of porcine eye lenses. As shown in control experiments on in vitro αB- and γD-crystallin, 2D IR spectroscopy can identify the highly ordered β-sheets typical of amyloid secondary structure even if the fibers themselves are too short to be resolved with TEM. In ex vivo experiments of acid-treated tissues, characteristic 2D IR features are observed and fibers >50nm in length are resolved by transmission electron microscopy (TEM), consistent with amyloid fibers. In UV-irradiated lens tissues, fibers are not observed with TEM, but highly ordered β-sheets of amyloid secondary structure is identified from the 2D IR spectra. The characteristic 2D IR features of amyloid β-sheet secondary structure are created by as few as four or five strands and so identify amyloid secondary structure even if the aggregates themselves are too small to be resolved with TEM. We discuss these findings in the context of the chaperone system of the lens, which we hypothesize sequesters small aggregates, thereby preventing long fibers from forming. This study expands the scope of heterodyned 2D IR spectroscopy to tissues. The results provide a link between in vitro and ex vivo studies and support the hypothesis that cataracts are an amyloid disease.

Echo Parameters for Differential Diagnosis in Cardiac Amyloidosis: A Head-to-Head Comparison of Deformation and Nondeformation Parameters

BACKGROUND

A plethora of echo parameters has been suggested for distinguishing cardiac amyloidosis (CA) from other causes of myocardial thickening with, however, scarce data on their head-to-head comparison. This study aimed at comparing the diagnostic accuracy of various deformation and conventional echo parameters in differentiating CA from other hypertrophic substrates, especially in the gray zone of mild hypertrophy (maximum wall thickness ≤16 mm) or normal ejection fraction (EF).

METHODS AND RESULTS

=0.0002, respectively) independent of the CA type.

CONCLUSIONS

Our study demonstrated that in patients with thickened hearts, EF global longitudinal strain ratio has the best accuracy in detecting CA, even among the most "challenging" patient subgroups as those with mild hypertrophy and normal EF.

Strain Imaging Echocardiography: What Imaging Cardiologists Should Know

Despite recent advances in clinical imaging, echocardiography remains as the most accessi-ble and reliable noninvasive. Since knowledge of left ventricular systolic function remains so critically important in determining prognosis; every effort should be made to prevent subjective estimations. The advent of strain imaging echocardiography now offers a readily available and portable imaging tool that not only offers an objective characterization of myocardial dynamics; but also allows for early detection of subclinical left ventricular dysfunction. This review outlines the basic concepts of strain imaging to better understand the mechanism of myocardial function as well their applicability in the least common cardiac diagnosis among current clinical practice.

Tafamidis for the Treatment of Hereditary Transthyretin Amyloid Cardiomyopathy: A Case Report

Tafamidis meglumine is a novel medicine that has been shown to slow the progression of peripheral neurological impairment in patients with hereditary transthyretin amyloidosis (ATTR). However, the efficacy of tafamidis against ATTR-related cardiac amyloidosis remains unclear. A 72-year-old woman had cardiac hypertrophy and axonopathy in her lower legs. Endomyocardial biopsy revealed an infiltrative cardiomyopathy consistent with amyloidosis. Immunostaining and genetic studies confirmed the diagnosis of ATTR, and tafamidis was started subsequently. Two years after the initiation of tafamidis treatment, electromyography demonstrated no change in the axonopathy in her lower legs; however, electrocardiography displayed QRS prolongation, and echocardiography disclosed an increase in interventricular septal thickness. Endomyocardial biopsy indicated that transthyretin amyloid infiltration of the myocardium was not reduced. In this case, there was no apparent progression of axonopathy, although there were signs of worsening amyloid cardiomyopathy during the treatment with tafamidis.

The Imaging Diagnosis of Less Advanced Cases of Cardiac Amyloidosis: The Relative Apical Sparing Pattern

An early diagnosis is important for improving the prognosis of cardiac amyloidosis (CA). We herein describe the utility of two-dimensional speckle tracking echocardiography (2-D STE) in diagnosing CA at a less advanced stage. A 63-year-old woman with exertional dyspnea was suspected of having CA based on her echocardiographic and electrocardiographic findings. A myocardial biopsy was negative for amyloid deposits, while the relative apical sparing pattern was detected on 2-D STE, which was highly suggestive of CA. Chemotherapy was initiated as a treatment for CA, and the patient's symptoms were immediately relieved. Thereafter, amyloid deposits were detected in a skin biopsy specimen.

Phase 2 trial of daily, oral epigallocatechin gallate in patients with light-chain amyloidosis

Previous studies have suggested that an increase in mitochondrial reactive oxygen species may cause organ damage in patients with light-chain (AL) amyloidosis; however, this damage can be decreased by antioxidant-agent treatment. Epigallocatechin gallate (EGCG), the major natural catechin in green tea, has potent antioxidant activity. Because EGCG has recently been reported to have a favorable toxicity profile for treating amyloidosis, we sought to examine the clinical efficacy and toxicity of EGCG in patients with AL amyloidosis. Fifty-seven patients were randomly assigned to the EGCG and observation groups and observed for six months. There were no increases in grade 3-5 adverse events and EGCG therapy was well tolerated. Although a decrease in the urinary albumin level was found in the EGCG group in patients with obvious albuminuria after treatment initiation, its antioxidant activity may not be sufficient to clarify the potential effect of EGCG in patients with AL amyloidosis. Because some of the biological markers responsible for organ damage were well correlated to the level of antioxidant potential in patients' plasma, the status of oxidative stress in the blood may indicate the extent of organ damage in clinical situations.

Up-Regulation of Antioxidant Proteins in the Plasma Proteome during Saturation Diving: Unique Coincidence under Hypobaric Hypoxia

Saturation diving (SD) is one of the safest techniques for tolerating hyperbaric conditions for long durations. However, the changes in the human plasma protein profile that occur during SD are unknown. To identify differential protein expression during or after SD, 65 blood samples from 15 healthy Japanese men trained in SD were analyzed by two-dimensional fluorescence difference gel electrophoresis. The expression of two proteins, one 32.4 kDa with an isoelectric point (pI) of 5.8 and the other 44.8 kDa with pI 4.0, were elevated during SD to 60, 100, and 200 meters sea water (msw). The expression of these proteins returned to pre-diving level when the SD training was completed. The two proteins were identified using in-gel digestion and mass spectrometric analysis; the 32.4 kDa protein was transthyretin and the 44.8 kDa protein was alpha-1-acid glycoprotein 1. Oxidation was detected at methionine 13 of transthyretin and at methionine 129 of alpha-1-acid glycoprotein 1 by tandem mass spectrometry. Moreover, haptoglobin was up-regulated during the decompression phase of 200 msw. These plasma proteins up-regulated during SD have a common function as anti-oxidants. This suggests that by coordinating their biological effects, these proteins activate a defense mechanism to counteract the effects of hyperbaric-hyperoxic conditions during SD.

Smooth muscle titin forms in vitro amyloid aggregates

Amyloids are insoluble fibrous protein aggregates, and their accumulation is associated with amyloidosis and many neurodegenerative diseases, including Alzheimer's disease. In the present study, we report that smooth muscle titin (SMT; 500 kDa) from chicken gizzard forms amyloid aggregates in vitro. This conclusion is supported by EM data, fluorescence analysis using thioflavin T (ThT), Congo red (CR) spectroscopy and X-ray diffraction. Our dynamic light scattering (DLS) data show that titin forms in vitro amyloid aggregates with a hydrodynamic radius (Rh) of approximately 700–4500 nm. The initial titin aggregates with Rh approximately 700 nm were observed beyond first 20 min its aggregation that shows a high rate of amyloid formation by this protein. We also showed using confocal microscopy the cytotoxic effect of SMT amyloid aggregates on smooth muscle cells from bovine aorta. This effect involves the disorganization of the actin cytoskeleton and result is cell damage. Cumulatively, our results indicate that titin may be involved in generation of amyloidosis in smooth muscles.

Light Chain Amyloid Fibrils Cause Metabolic Dysfunction in Human Cardiomyocytes

Light chain (AL) amyloidosis is the most common form of systemic amyloid disease, and cardiomyopathy is a dire consequence, resulting in an extremely poor prognosis. AL is characterized by the production of monoclonal free light chains that deposit as amyloid fibrils principally in the heart, liver, and kidneys causing organ dysfunction. We have studied the effects of amyloid fibrils, produced from recombinant λ6 light chain variable domains, on metabolic activity of human cardiomyocytes. The data indicate that fibrils at 0.1 μM, but not monomer, significantly decrease the enzymatic activity of cellular NAD(P)H-dependent oxidoreductase, without causing significant cell death. The presence of amyloid fibrils did not affect ATP levels; however, oxygen consumption was increased and reactive oxygen species were detected. Confocal fluorescence microscopy showed that fibrils bound to and remained at the cell surface with little fibril internalization. These data indicate that AL amyloid fibrils severely impair cardiomyocyte metabolism in a dose dependent manner. These data suggest that effective therapeutic intervention for these patients should include methods for removing potentially toxic amyloid fibrils.

Functional Amyloid Signaling via the Inflammasome, Necrosome, and Signalosome: New Therapeutic Targets in Heart Failure

As the most common cause of death and disability, globally, heart disease remains an incompletely understood enigma. A growing number of cardiac diseases are being characterized by the presence of misfolded proteins underlying their pathophysiology, including cardiac amyloidosis and dilated cardiomyopathy (DCM). At least nine precursor proteins have been implicated in the development of cardiac amyloidosis, most commonly caused by multiple myeloma light chain disease and disease-causing mutant or wildtype transthyretin (TTR). Similarly, aggregates with PSEN1 and COFILIN-2 have been identified in up to one-third of idiopathic DCM cases studied, indicating the potential predominance of misfolded proteins in heart failure. In this review, we present recent evidence linking misfolded proteins mechanistically with heart failure and present multiple lines of new therapeutic approaches that target the prevention of misfolded proteins in cardiac TTR amyloid disease. These include multiple small molecule pharmacological chaperones now in clinical trials designed specifically to support TTR folding by rational design, such as tafamidis, and chaperones previously developed for other purposes, such as doxycycline and tauroursodeoxycholic acid. Last, we present newly discovered non-pathological "functional" amyloid structures, such as the inflammasome and necrosome signaling complexes, which can be activated directly by amyloid. These may represent future targets to successfully attenuate amyloid-induced proteotoxicity in heart failure, as the inflammasome, for example, is being therapeutically inhibited experimentally in autoimmune disease. Together, these studies demonstrate multiple novel points in which new therapies may be used to primarily prevent misfolded proteins or to inhibit their downstream amyloid-mediated effectors, such as the inflammasome, to prevent proteotoxicity in heart failure.

Can echocardiography and ECG discriminate hereditary transthyretin V30M amyloidosis from hypertrophic cardiomyopathy?

OBJECTIVE

Hereditary transthyretin (ATTR) amyloidosis with increased left ventricular wall thickness could easily be misdiagnosed by echocardiography as hypertrophic cardiomyopathy (HCM). Our aim was to create a diagnostic tool based on echocardiography and ECG that could optimise identification of ATTR amyloidosis.

METHODS

Data were analysed from 33 patients with biopsy proven ATTR amyloidosis and 30 patients with diagnosed HCM. Conventional features from ECG were acquired as well as two dimensional and Doppler echocardiography, speckle tracking derived strain and tissue characterisation analysis. Classification trees were used to select the most important variables for differentiation between ATTR amyloidosis and HCM.

RESULTS

The best classification was obtained using both ECG and echocardiographic features, where a QRS voltage >30 mm was diagnostic for HCM, whereas in patients with QRS voltage <30 mm, an interventricular septal/posterior wall thickness ratio (IVSt/PWt) >1.6 was consistent with HCM and a ratio <1.6 supported the diagnosis of ATTR amyloidosis. This classification presented both high sensitivity (0.939) and specificity (0.833).

CONCLUSION

Our study proposes an easily interpretable classification method for the differentiation between HCM and increased left ventricular myocardial thickness due to ATTR amyloidosis. Our combined echocardiographic and ECG model could increase the ability to identify ATTR cardiac amyloidosis in clinical practice.

Almanac 2014: cardiovascular imaging

The 'Almanac' Reviews provide an overview of articles on a specific topic published in Heart over the past 2 years, put in the context of advances in the field, including publications from several other journals. The focus of this Almanac article is Cardiovascular imaging--as a general cardiology journal, the imaging research in Heart tends to be clinically oriented and often will impact our clinical practice.

Ischemic Hepatitis as the Presenting Manifestation of Cardiac Amyloidosis

An abrupt elevation in aminotransferases without clear etiology may be attributed to hypoxic hepatitis. Underlying cardiac dysfunction, an important clinical clue, is often overlooked as a cause of hypoxic hepatitis, and understanding the interdependence of the heart and liver is crucial in making this diagnosis. Causes of cardiac dysfunction may include any of many different diagnoses; infiltrative heart disease is a rare cause of cardiac dysfunction, with amyloidosis being the most common among this category of pathologies. More advanced imaging techniques have improved the ability to diagnose infiltrative heart disease, thus allowing quicker diagnosis of conditions such as amyloidosis.

Disease-specific differences of left ventricular rotational mechanics between cardiac amyloidosis and hypertrophic cardiomyopathy

Left ventricular (LV) twist (LVT) and untwisting (LVUT) rate are global and thorough parameters of LV function. The aim of the present study was to investigate the differences in LV rotational mechanics between patients with cardiac amyloidosis (CA) and hypertrophic cardiomyopathy (HCM). Twenty consecutive patients with CA, 20 consecutive patients with HCM, and 20 consecutive subjects without evidence of structural heart disease were included. Cardiac magnetic resonance (CMR) with late gadolinium enhancement (LGE) imaging was performed to evaluate biventricular function, LV mass index, and presence/extent of LGE. Feature-tracking analysis was applied to LV basal and apical short-axis images to determine peak LVT, time to peak LVT, peak LVUT rate, and time to peak LVUT rate. Peak LVT and peak LVUT rate were significantly impaired in patients with CA compared with controls (P < 0.05 for both). In patients with HCM, peak LVT was increased (P < 0.05) compared with controls, whereas peak LVUT rate was preserved (P > 0.05). Time to peak LVUT rate was significantly prolonged in patients with CA and in patients with HCM compared with controls (ANOVA P < 0.001). At multivariate analysis, age (P = 0.007), LV ejection fraction (P = 0.035) and extent of LGE (P < 0.001) were independently related to peak LVT, and LV mass index (P = 0.015) and extent of LGE (P = 0.004) were independently related to peak LVUT rate, whereas extent of LGE (P < 0.001) was the only variable independently related to time to peak LVUT rate. In conclusion, CA and HCM have specific behavior of LV rotational mechanics. The extent of LGE significantly influences the LV rotational mechanics.

In vitro binding of [³H]PIB to human amyloid deposits of different types

Systemic amyloidosis is caused by extracellular deposition of insoluble fibrillar proteins arranged in β-pleated sheets. [(11)C]PIB has been used in PET studies to assess Aβ deposition in brain of patients with Alzheimer's disease (AD). The possibility to visualize other types of amyloid deposits with [(11)C]PIB would be of potential clinical importance in early diagnosis and for following therapeutic effects. In the present study, we evaluated in vitro binding of [(3)H]PIB to tissues containing transthyretin (ATTR), immunoglobulin light-chain (AL), amyloid protein A (AA) and Aβ amyloid. We found significantly higher binding of [(3)H]PIB in tissue from systemic amyloidoses than in control tissue, i.e. 4.7 times higher (p < 0.05). [(3)H]PIB showed the highest affinity to cortex of AD brain (IC50 = 3.84 nM), while IC50 values were much higher for ATTR, AA and AL type of amyloidosis and large variations in affinity were observed even within tissues having the same type of amyloidosis. Extraction with guanidine-HCl, which disrupts the β-sheet structure, decreased the protein levels and, concomitantly, the binding of [(3)H]PIB in all four types of amyloidoses.

Stanniocalcin1 is a key mediator of amyloidogenic light chain induced cardiotoxicity

Immunoglobulin light chain (LC) amyloidosis (AL) results from overproduction of circulating amyloidogenic LC proteins and subsequent amyloid fibril deposition in organs. Mortality in AL amyloidosis patients is highly associated with a rapidly progressive AL cardiomyopathy, marked by profound impairment of diastolic and systolic cardiac function and significant early mortality. While myocardial fibril deposition contributes to the severe diastolic dysfunction seen in AL cardiomyopathy patients, the degree of fibril deposition has not been found to correlate with prognosis. Previously, we and others showed a direct cardiotoxic effect of amyloidogenic LC proteins (AL-LC), which may contribute to the pathophysiology and mortality observed in AL cardiomyopathy patients. However, the mechanisms underlying AL-LC related cardiotoxicity remain unknown. Mammalian stanniocalcin1 (STC1) is associated with a number of cellular processes including oxidative stress and cell death. Herein, we find that STC1 expression is elevated in cardiac tissue from AL cardiomyopathy patients, and is induced in isolated cardiomyocytes in response to AL-LC, but not non-amyloidogenic LC. STC1 overexpression in vitro recapitulates the pathophysiology of AL-LC mediated cardiotoxicity, with increased ROS production, contractile dysfunction and cell death. Overexpression of STC1 in vivo results in significant cardiac dysfunction and cell death. Genetic silencing of STC1 prevents AL-LC induced cardiotoxicity in cardiomyocytes and protects against AL-LC induced cell death and early mortality in zebrafish. The cardiotoxic effects of STC1 appears to be mediated via mitochondrial dysfunction as indicated by loss of mitochondrial membrane potential, ROS production and increased mitochondrial calcium levels. Collectively, this work identifies STC1 as a critical determinant of AL-LC cardiotoxicity.

A binding-site barrier affects imaging efficiency of high affinity amyloid-reactive peptide radiotracers in vivo

Amyloid is a complex pathology associated with a growing number of diseases including Alzheimer’s disease, type 2 diabetes, rheumatoid arthritis, and myeloma. The distribution and extent of amyloid deposition in body organs establishes the prognosis and can define treatment options; therefore, determining the amyloid load by using non-invasive molecular imaging is clinically important. We have identified a heparin-binding peptide designated p5 that, when radioiodinated, was capable of selectively imaging systemic visceral AA amyloidosis in a murine model of the disease. The p5 peptide was posited to bind effectively to amyloid deposits, relative to similarly charged polybasic heparin-reactive peptides, because it adopted a polar α helix secondary structure. We have now synthesized a variant, p5R, in which the 8 lysine amino acids of p5 have been replaced with arginine residues predisposing the peptide toward the α helical conformation in an effort to enhance the reactivity of the peptide with the amyloid substrate. The p5R peptide had higher affinity for amyloid and visualized AA amyloid in mice by using SPECT/CT imaging; however, the microdistribution, as evidenced in micro-autoradiographs, was dramatically altered relative to the p5 peptide due to its increased affinity and a resultant “binding site barrier” effect. These data suggest that radioiodinated peptide p5R may be optimal for the in vivo detection of discreet, perivascular amyloid, as found in the brain and pancreatic vasculature, by using molecular imaging techniques; however, peptide p5, due to its increased penetration, may yield more quantitative imaging of expansive tissue amyloid deposits.

Human amyloidogenic light chain proteins result in cardiac dysfunction, cell death, and early mortality in zebrafish

Systemic amyloid light-chain (AL) amyloidosis is associated with rapidly progressive and fatal cardiomyopathy resulting from the direct cardiotoxic effects of circulating AL light chain (AL-LC) proteins and the indirect effects of AL fibril tissue infiltration. Cardiac amyloidosis is resistant to standard heart failure therapies, and, to date, there are limited treatment options for these patients. The mechanisms underlying the development of cardiac amyloidosis and AL-LC cardiotoxicity are largely unknown, and their study has been limited by the lack of a suitable in vivo model system. Here, we establish an in vivo zebrafish model of human AL-LC-induced cardiotoxicity. AL-LC isolated from AL cardiomyopathy patients or control nonamyloidogenic LC protein isolated from multiple myeloma patients (Con-LC) was directly injected into the circulation of zebrafish at 48 h postfertilization. AL-LC injection resulted in impaired cardiac function, pericardial edema, and increased cell death relative to Con-LC, culminating in compromised survival with 100% mortality within 2 wk, independent of AL fibril deposition. Prior work has implicated noncanonical p38 MAPK activation in the pathogenesis of AL-LC-induced cardiotoxicity, and p38 MAPK inhibition via SB-203580 rescued AL-LC-induced cardiac dysfunction and cell death and attenuated mortality in zebrafish. This in vivo zebrafish model of AL-LC cardiotoxicity demonstrates that antagonism of p38 MAPK within the AL-LC cardiotoxic signaling response may serve to improve cardiac function and mortality in AL cardiomyopathy. Furthermore, this in vivo model system will allow for further study of the molecular underpinnings of AL cardiotoxicity and identification of novel therapeutic strategies.