Restrictive Cardiomyopathy Research Articles

Neuromuscular and cardiovascular phenotypes in paediatric titinopathies: a multisite retrospective study

BackgroundPathogenic variants in TTN cause a spectrum of autosomal dominant and recessive cardiovascular, skeletal muscle and cardioskeletal disease with symptom onset across the lifespan. The aim of this study was...

Unveiling Alarming Trends: Worsening All Cause Mortality in US Adults over 25 with Amyloid 1999-2020 Analysis

Introduction: Amyloidosis is a collective term for conditions with an abnormal extracellular deposition of amyloid protein. Amyloidosis can be classified based on the location of deposition (localized vs systemic) and by the different subtypes of proteins which are created as a result of a variety of diseases (plasma cell dyscrasias, chronic inflammation, nephrotic syndrome, genetic). Depending on the affected organs, amyloidosis can present with, not limited to, hepatomegaly, renal impairment, nerve conduction impairment, cardiac conduction abnormalities, restrictive cardiomyopathy, and multiorgan failure. In the last century there has been an increase in innovations leading to a better understanding of the pathology, diagnostic tests, staging, and treatment options for amyloidosis. Our study aims to compare all cause mortality trends in adults over 25 years old diagnosed with amyloidosis in the United States. Methods: The national mortality trends from 1999 to 2020 for all subtypes of amyloid were analyzed from the CDC WONDER database. The data was extracted using ICD codes E85 (Amyloidosis) with subgroups E85.0 (Non-neuropathic heredofamilial amyloidosis), E85.3 (Secondary systemic amyloidosis), E85.4 (Organ-limited amyloidosis), E85.8 (Other amyloidosis), and E85.9 (Amyloidosis, unspecified. Data was stratified for age groups above 25 years old. Age-adjusted mortality rates (AAMRs) were calculated per 100,000 people and death certificate data was stratified by reported sex, race/ethnicity, and US census region. Results: Between 1999 and 2020 there were 40,015 deaths from amyloid. Our analysis revealed that all-cause AAMR per 100,000 people with amyloid showed an increasing trend between 1999 to 2020 (Figure 1). Subgroup analysis on race/ethnicity revealed the AAMR for the Black population has been consistently higher to other groups (Table 1). On average, from 1999 to 2020, the Black population had the highest AAMR (1.52 AAMR) followed by the White population (0.78 AAMR), Hispanic (0.55 AAMR), and Asian (0.5 AAMR). Further subgroup analysis revealed men have a higher AAMR (1.9 AAMR, 2020) compared to women (0.8 AAMR, 2020). Overall there are similar census region trends of all mortality in Amyloid: North (1.5 AAMR, 2020), Midwest (1.5 AAMR, 2020), South (1.0, AAMR, 2020) and West (1.3 AAMR, 2020). Conclusion: Due to advancement in technology, amyloid diseases are becoming more widely recognized and increasingly diagnosed. Unfortunately, treatment of amyloidosis remains limited to early diagnosis and treatment of the underlying condition. This includes modalities such as chemotherapy and stem cell transplantation for plasma cell dysplasias and TTR stabilizers for hereditary amyloidosis. These trends in increase in AAMR likely reflect the increased awareness/diagnostics of amyloid disease and complications. The African American population may have higher AAMR due to socioeconomic and environmental factors, health disparities, and research bias. We also suspect men have a higher ATTR than women as it has been reported that ATTR and AL Amyloidosis tends to occur more frequently in men than women and is associated with more severe disease (Kroi et al., 2020, Desport et al., 2012). Further research is necessary to expand on the disparities seen with the ultimate goal of providing targeted therapies to reverse this downward trend.

Effects of diabetes mellitus on left ventricular function and deformation in patients with restrictive cardiomyopathies: a 3.0T CMR feature tracking study

BackgroundDiabetes mellitus (DM) is the most common metabolic disease worldwide and a major risk factor for adverse cardiovascular events, while the additive effects of DM on left ventricular (LV) deformation in the restrictive cardiomyopathy (RCM) cohort remain unclear. Accordingly, we aimed to investigate the additive effects of DM on LV deformation in patients with RCM.Materials and methodsOne hundred thirty-six RCM patients without DM [RCM(DM−)], 46 with DM [RCM (DM+)], and 66 age- and sex-matched control subjects who underwent cardiac magnetic resonance (CMR) scanning were included. LV function, late gadolinium enhancement (LGE) type, and LV global peak strains (including radial, circumferential, and longitudinal directions) were measured. The determinant of reduced LV global myocardial strain for all RCM patients was assessed using multivariable linear regression analyses. The receiver operating characteristic curve (ROC) was performed to illustrate the relationship between DM and decreased LV deformation.ResultsCompared with the control group, RCM (DM−) and RCM(DM+) patients presented increased LV end-diastolic index and end-systolic volume index and decreased LV ejection fraction. LV GPS in all three directions and longitudinal PDSR progressively declined from the control group to the RCM(DM−) group to the RCM(DM+) group (all p < 0.05). DM was an independent determinant of impaired LV GPS in the radial, circumferential, and longitudinal directions and longitudinal PDSR (β = − 0.217, 0.176, 0.253, and − 0.263, all p < 0.05) in RCM patients. The multiparameter combination, including DM, showed an AUC of 0.81(95% CI 0.75–0.87) to predict decreased LV GLPS and an AUC of 0.69 (95% CI 0.62–0.76) to predict decreased LV longitudinal PDSR.ConclusionsDM may have an additive deleterious effect on LV dysfunction in patients with RCM, especially diastolic dysfunction in RCM patients, indicating the importance of early identification and initiation of treatment of DM in patients with RCM.

Prognosis after heart transplant in patients with hypertrophic and restrictive cardiomyopathy. A nationwide registry analysis

Introduction and objectivesPosttransplant outcomes among recipients with a diagnosis of hypertrophic cardiomyopathy (HCM) or restrictive cardiomyopathy (RCM) remain controversial. MethodsRetrospective analysis of a nationwide registry of first-time recipients undergoing isolated heart transplant between 1984 and 2021. One-year and 5-year mortality in recipients with HCM and RCM were compared with those with dilated cardiomyopathy (DCM). ResultsWe included 3703 patients (3112 DCM; 331 HCM; 260 RCM) with a median follow-up of 5.0 [3.1-5.0] years. Compared with DCM, the adjusted 1-year mortality risk was: HCM: HR, 1.38; 95%CI, 1.07-1.78; P=.01, RCM: HR, 1.48; 95%CI, 1.14-1.93; P=.003. The adjusted 5-year mortality risk was: HCM: HR, 1.17; 95%CI, 0.93-1.47; P=.18; RCM: HR, 1.52; 95%CI, 1.22-1.89; P<.001. Over the last 20 years, the RCM group showed significant improvement in 1-year survival (adjusted R2=0.95) and 5-year survival (R2=0.88); the HCM group showed enhanced the 5-year survival (R2=0.59), but the 1-year survival remained stable (R2=0.16). ConclusionsBoth RCM and HCM were linked to a less favorable early posttransplant prognosis compared with DCM. However, at the 5-year mark, this unfavorable difference was evident only for RCM. Notably, a substantial temporal enhancement in both early and late mortality was observed for RCM, while for HCM, this improvement was mainly evident in late mortality.

The new European Society of Cardiology guideline for the management of cardiomyopathies: key messages for cardiac electrophysiologists.

Electrocardiographic findings and arrhythmias are common in cardiomyopathies. Both may be an early indication of aspecific diagnosis or may occur due to myocardial fibrosis and/or reduced contractility. Brady- and tachyarrhythmias significantly contribute to increased morbidity and mortality in patients with cardiomyopathies. Antiarrhythmic therapy including risk stratification is often challenging and plays amajor role for these patients. Thus, an "electrophysiological" perspective on guidelines on cardiomyopathies may be warranted. As the European Society of Cardiology (ESC) has recently published anew guideline for the management of cardiomyopathies, this overview aims to present key messages of these guidelines. Innovations include anew phenotype-based classification system with emphasis on amultimodal imaging approach for diagnosis and risk stratification. The guideline includes detailed chapters on dilated and hypertrophic cardiomyopathy and their phenocopies, arrhythmogenic right ventricular cardiomyopathy, and restrictive cardiomyopathy as well as syndromic and metabolic cardiomyopathies. Patient pathways guide clinicians from the initial presentation to diagnosis. The role of cardiovascular magnetic resonance imaging and genetic testing during diagnostic work-up is stressed. Concepts of rhythm and rate control for atrial fibrillation have led to new recommendations, and the role of defibrillator therapy in primary prevention is discussed in detail. Whilst providing general guidelines for management, the primary objective of the guideline is to ascertain the disease etiology and disease-specific, individualized management.

Survival analysis of tafamidis use in patients with ATTR cardiac amyloidosis

Abstract Introduction Transthyretin cardiac amyloidosis (ATTR-CM) is a condition in which amyloid fibrils are deposited within the myocardium causing a restrictive cardiomyopathy &amp; resulting heart failure condition. With increasing recognition, a challenge posed, surrounds decisions on optimal treatment strategies. For patients with predominant cardiac amyloidosis, without peripheral/autonomic nervous system involvement, targeted treatments are limited, although the medication tafamidis – a TTR stabiliser, is available since approval by the FDA in 2019 &amp; the European commission in 2020. Aim This study aims to analyse the real-world benefit of tafamidis use in patients with ATTR-CM attending the National Amyloidosis Centre (NAC), UK with regards overall survival from diagnosis when compared to those not on targeted treatment. Methods This was a retrospective study using data taken from a database at the NAC, as all patients included attend the NAC, UK. Patients on tafamidis were matched to control patients (not on targeted treatment) for age, ATTR NAC stage at diagnosis and type of ATTR (i.e. variant or wild-type). Outcome and survival analysis were determined using cox regression analysis and Kaplan-Meier curve using SPSS (V9.0). Results The demographics of patients in both groups are detailed in figure 1. There were 75 patients in both the treatment &amp; control groups. The median follow-up time from diagnosis to data acquisition in the control group was 3.7 years [IQR1.8-5.8] compared to 4.3 years [IQR 3.6-5.4] in the treatment group (p = 0.03). Of note the median duration from diagnosis to starting tafamidis was 2.1 years [1.2-3.2]. Using cox regression analysis, tafamidis use was predictive of a reduced likelihood of death (R = -1.4, p&amp;lt;0.001) [OR 0.24 95%CI 0.12-0.47]. Increasing NAC stage at diagnosis (R = 0.42, P = 0.03), [OR1.5, 95%CI 1.04-2.22] was predictive of increased likelihood of death. Increasing age (R = 0.03, p = 0.07) [OR 1.03, 95%CI 0.98-1.07] was non-significantly associated with increased likelihood of death. There was similarly a significant increase in mortality within the control/non-treatment group of patients (P&amp;lt;0.001) which was reflected in the Kaplan-Meier survival curve (p&amp;lt;0.001). Conclusions In this retrospective analysis, tafamidis use in 75 patients with ATTR-CM, initiated after a median of 2.2 year [IQR1.2-3.2] following diagnosis, was associated with significantly reduced mortality when compared to an untreated matched control group. Survival from diagnosis was similarly improved in the tafamidis group as depicted by the Kaplan-Meier curve. This real-world data suggests support for the use of tafamidis in treating those with ATTR-CM.

Impact of increased DPD scintigraphy on timing of diagnosis and prognosis of transthyretin cardiac amyloidosis over the course of ten years

Abstract Background 99mTechnetium labelled 3,3-diphosphono-1,2-propanodicarboxylic acid (99mTc-DPD) scintigraphy is a sensitive non-invasive method for imaging transthyretin cardiac amyloidosis (ATTR-CA). The emergence of novel pharmacotherapies for ATTR-CA has resulted in much greater disease awareness. Objective We aimed to assess the level of increased demand for DPD scintigraphy and its influence on the clinical phenotype of patients diagnosed with ATTR-CA over the past 10 years. Methods This was a retrospective observational cohort study of patients referred to our centre (2012–2022) for DPD scintigraphy in whom ATTR-CA was a differential diagnosis. The protocol consisted of a planar whole-body acquisition performed at 3 hours after the injection, followed by single-photon emission computed tomography imaging of the thorax. Intensity of myocardial uptake on the planar 99mTc-DPD scan was categorized as 0 to 3 according to the Perugini grading system. A diagnosis of ATTR-CA was established on the basis of heart failure symptoms together with characteristic echocardiography or cardiac magnetic resonance imaging, and a grade 2 or 3 cardiac uptake on Tc99m-DPD in the absence of biochemical evidence of a monoclonal dyscrasia. Results As of December 2022, we identified 426 DPD scans performed in 421 patients (mean age 75 ± 12 yr, 72% male) referred for 99mTc-DPD, of whom 151 subsequently had a diagnosis of ATTR-CA confirmed. Patients diagnosed with AL-CA (n=2) were excluded for the purpose of this analysis. The number of DPD scans increased significantly in 2021-2022 (211 out of 426 studies) compared with previous 2 year periods (p&amp;lt;0.01) with an increasing proportion of referrals in this period made by cardiologists (p&amp;lt;0.05). In patients diagnosed with ATTR-CA, the proportion of grade 2 versus grade 3 Perugini scans increased in 2021-2022 compared with earlier years. There was no difference in survival among patients according to DPD grading (Figure 1; log rank p = 0.35). There was also no difference in survival between patients with ATTR-CA patients and DPD negative patients presenting with other forms of restrictive cardiomyopathy (Figure 2; HR 1.46, 95%CI [0.94-2.26], log rank p= 0.09). Conclusions Based on DPD grading, patients are being referred earlier by cardiologists with suspected ATTR-CA. DPD grading does not, however, carry prognostic significance in those patients subsequently diagnosed with ATTR-CA. Patients referred but who are not subsequently diagnosed with ATTR-CA have a similarly adverse prognosis to those with ATTR-CA; this forgotten cohort of non-specific restrictive cardiomyopathy is worthy of further follow up and investigation.5 year survival for all patients

Echo-derived hemodynamic categorization for risk stratification in transthyretin cardiac amyloidosis

Abstract Background Transthyretin cardiac amyloidosis (TTR-CA) is a rare disease characterized by the deposition of abnormal proteins in the heart, which can lead to heart failure (HF) and death. Echocardiography provides valuable diagnostic and prognostic information in CA, but indices of left ventricular performance alone cannot thoroughly characterise patients with restrictive cardiomyopathy. Evaluating the hemodynamic profile by studying the forward flow and left ventricular filling pressure (LVFP) already proved its value in stratifying disease severity in patients with heart failure (HF). Purpose This study evaluated the prognostic relevance of a non-invasive hemodynamic categorization of TTR-CA patients based on the estimation of stroke volume index (SVi) and systolic pulmonary artery pressure (PAPs). Methods Baseline clinical, transthoracic echocardiogram and laboratory data were collected prospectively in patients with diagnosed TTR-CA. Patients were classified into four groups based on forward flow (SVi &amp;lt; or ≥30 ml/m2) and systolic pulmonary artery pressure (PAPs ≥ or &amp;lt;40 mmHg). The four profiles obtained were Profile-A, normal-flow, normal-pressure; Profile-B, low-flow, normal-pressure; Profile-C, normal-flow, high-pressure; Profile-D, low-flow, high-pressure. We assessed the incidence of the composite endpoint of cardiovascular death and HF hospitalization accordingly to the hemodynamic profile. We performed univariate and multivariate Cox regression using profile A as a reference for HR estimation (profile A corresponding to HR=1). Results Fifty-nine patients were enrolled in the analysis (Table). Over a mean follow-up of 35.9 months (IQR 11.7 - 51.2 months) 23 patients met the composite endpoint (10%, 23%, 43%, 60% for Profile A, B, C and D respectively). Compared to Profile A, Profile D showed the greatest risk of CV mortality and HF hospitalization (HR 10.17), followed by Profile C (HR 6.77) and B (HR 3.45), with P-value=0.015. The C-statistic for the model was 0.72. Kaplan-Meier curves confirmed that patients with PAPs &amp;gt;40 mmHg and SVi&amp;lt; 30 ml/m2 presented the highest risk of the composite endpoint (Log-rank P = 0.010) (Figure). Hemodynamic profiling remained an independent predictor of outcome even after adjusting for the NAC stage (Profile B, HR 2.26; Profile C, HR 6.96; Profile D, HR 17.13; P-value=0.0012). Conclusions The proposed echocardiographically-derived hemodynamic classification based on forward-flow and LVFP estimation is useful for TTR-CA patients risk stratification. Patients with low SVi and high PAPs have the greatest risk of CV death and HF hospitalization, even after adjustment for NAC stage. These findings highlight the importance of early detection and monitoring of hemodynamic changes in TTR-CA patients for tailored management and to improve outcomes.Table.Figure.

Characterization of AT-02, a pan-amyloid-binding peptide fusion immunoglobulin with high binding potency, complement activation, and immune cell stimulation

Abstract Background Cardiac amyloidosis is an ominous manifestation of systemic amyloidosis, notably in AL and ATTR-associated types, resulting in a restrictive hypertrophic cardiomyopathy with electrical conduction and atrioventricular strain dysfunction (1). Amyloid is not naturally cleared by the immune system due to the presence of extracellular matrix components in the deposits (2). However, recruiting and stimulating the innate immune system, notably phagocytic macrophages, is a promising strategy to effect amyloid removal. To facilitate this, we have generated AT-02, a humanized IgG1 incorporating the pan-amyloid-binding peptide, p5R (3), at the light chain C-terminus. This reagent binds diverse types of amyloid via the peptide interactions and retains immunomodulatory capacity. Purpose The goal of these studies was to characterize the bioactivity of AT-02 that underlies its potential therapeutic activity. Methods AT-02 was produced from a CHO pool using a perfusion cell culture production process, purified by Protein A, anion exchange, and cation exchange chromatographies, and characterized by mass spectrometry and SDS-capillary electrophoresis. AT-02 was biotinylated and used for immunohistochemical detection of both AL and ATTR amyloidosis in formalin fixed tissues (Figure 1A). Binding to heparin (as a surrogate for amyloid-associated hypersulfated heparan sulfate proteoglycans) and synthetic AL fibrils was studied using both ELISA and surface plasmon resonance assays (Figure 1B). Activation of complement following binding to amyloid substrates was determined using a C5b9 liberation assay in the presence of human plasma. The effect of AT-02 on amyloid fibril growth was determined using a fluorescence fibril elongation assay. In vivo clearance of amyloid and cell activation was demonstrated using a murine model of AL amyloidoma. Results AT-02 bound human cardiac amyloid in tissue sections with high specificity and intensity. The potency for heparin and synthetic amyloid fibrils, as well as human cardiac amyloid extracts, was sub-nanomolar in the ELISA assay with kinetics consistent with a high affinity antibody. In the presence of plasma, complement activation of amyloid-bound AT-02 was significantly higher as compared to controls, and the reagent inhibited synthetic amyloid fibril growth by ∼40%. Treatment of human amyloid with AT-02 expedited phagocytosis by murine macrophages in vivo and enhanced the intensity of immune response to the implanted amyloid. Conclusion Clearance of cardiac amyloid is a significant clinical unmet need for patients with systemic amyloidosis. The humanized IgG1-peptide fusion, AT-02, potently binds cardiac amyloid and may serve as an opsonin and induce macrophage-mediated phagocytosis and clearance of cardiac amyloid deposits.

Human in vitro disease modeling of ATTR cardiac amyloidosis

Abstract Background Amyloidosis is a systemic protein-folding disorder characterized by extracellular misfolded fibrillar protein aggregates that are insoluble and resistant to proteolysis, leading to progressive and vital organ damage [1]. Transthyretin amyloidosis (ATTR) is one of the primary amyloidosis types that affect the heart. Based on the TTR gene sequence, ATTR is further classified into wild-type ATTR (ATTRwt) and hereditary ATTR (ATTRv). Advanced stage TTR amyloid infiltration of the myocardium results in progressive thickening and stiffening of the ventricle wall, and symptoms of restrictive cardiomyopathy and congestive heart failure. Due to the lack of specificity of cardiac amyloidosis symptoms, misdiagnosis and delays in diagnosis are common, resulting in worsening symptoms, organ damage, and increased mortality [2]. Despite the development of several disease-modifying agents [3], current experimental cell and animal models do not adequately represent the human situation, thereby limiting disease understanding and therapeutic discovery. Purpose This project aims to develop an in vitro ATTR disease model, which is critical to define early disease stages and disease progression, map human disease-specific pathways, and screen for novel drugs or validating cutting-edge therapeutic strategies. Methods Recombinant WT-TTR and V122I mutated TTR (V122I) were prepared using E.coli protein production system. TTR purification and acid-mediated TTR-fibril were characterized by SDS-PAGE, Thioflavin T fluorescence measurement, and transmission electron microscope (EM). iPSC-derived cardiomyocytes (iPS-CMs) were differentiated using GiWi protocol as described [4,5]. iPS-CMs or HUVECs were seeded on TTR or TTR-fibril, and we measured beating rate, cell viability (AlamarBlue and LiveDead), and cell/fibril morphology using immunofluorescence. Results Purified recombinant WT and V122I TTR was successfully generated (Figure 1A). Fluorescence increase (Thioflavin T) and EM revealed the presence of TTR-fibril (Figure 1B). iPS-CMs seeded on TTR-fibril resulted in a dose- and time-dependent increase in cell death. Confocal microscopy revealed the attachment of TTR-fibril on iPS-CMs, leading to sarcomere disarray, loss of cell-to-cell coupling, resulting in irregular beating (Figure 2A). Additionally, we found drastically affected viability of HUVECs upon TTR-fibril exposure (Figure 2B). Conclusion Here, we demonstrate an established method to generate purified TTR and TTR-fibril. TTR-fibril attached to the surface of iPS-CMs decreased cell viability and functionality. Similar reduction in HUVEC viability were observed as well. These findings reflect the cytotoxicity of TTR-fibril in a human in vitro model.TTR and TTR-fibril characterizationCell viability up TTR-fibril exposure

Echocardiography-Based Deep Learning Model to Differentiate Constrictive Pericarditis and Restrictive Cardiomyopathy

BackgroundConstrictive pericarditis (CP) is an uncommon but reversible cause of diastolic heart failure if appropriately identified and treated. However, its diagnosis remains a challenge for clinicians. Artificial intelligence may enhance the identification of CP. ObjectivesThe authors proposed a deep learning approach based on transthoracic echocardiography to differentiate CP from restrictive cardiomyopathy. MethodsPatients with a confirmed diagnosis of CP and cardiac amyloidosis (CA) (as the representative disease of restrictive cardiomyopathy) at Mayo Clinic Rochester from January 2003 to December 2021 were identified to extract baseline demographics. The apical 4-chamber view from transthoracic echocardiography studies was used as input data. The patients were split into a 60:20:20 ratio for training, validation, and held-out test sets of the ResNet50 deep learning model. The model performance (differentiating CP and CA) was evaluated in the test set with the area under the curve. GradCAM was used for model interpretation. ResultsA total of 381 patients were identified, including 184 (48.3%) CP, and 197 (51.7%) CA cases. The mean age was 68.7 ± 11.4 years, and 72.8% were male. ResNet50 had a performance with an area under the curve of 0.97 to differentiate the 2-class classification task (CP vs CA). The GradCAM heatmap showed activation around the ventricular septal area. ConclusionsWith a standard apical 4-chamber view, our artificial intelligence model provides a platform to facilitate the detection of CP, allowing for improved workflow efficiency and prompt referral for more advanced evaluation and intervention of CP.

Abstract 16843: Diastolic Dysfunction Due to Structual Changes in Mutant Troponin I May Cause Restrictive Cardiomyopathy; Cryo-Electron Microscopic Analysis Using Induced Pluripotent Stem Cell Derived Cardiomyocytes

Introduction: Restrictive cardiomyopathy (RCM) is characterized by ventricular diastolic dysfunction with preserved contraction. Since there is no effective treatment other than heart transplantation, the development of novel treatment strategy by elucidating pathophysiology of RCM is an important issue under the serious donor shortage.Various troponin I mutations have been reported in patients with RCM and given that troponin I regulates the inhibition of cardiac contraction, it is possible that structural changes in mutant troponin I cause diastolic dysfunction in RCM. Recently, cryo-electron microscopy (cryo-EM) has made it possible to analyze the structure of thin filaments of muscle fibers. In this study, we applied the technology of induced pluripotent stem cell (iPSC) to cryo-EM structural analysis of thin filaments in cardiomyocytes from RCM patients with troponin I mutations. Methods: We established an iPSC line from a pediatric RCM patient with heterozygous TNNI3 mutation (R170W). Then the iPSCs were differentiated to cardiomyocytes to compare the cellular physiological, structural features. Normal adult iPS cell derived cardiomyocytes (Ctrl-iPSC-CM) were used as control. We also extracted thin filaments from iPSC-CMs and analyzed their structure with cryo-EM. Results: PCR analysis revealed the percentage of mutant alleles in TNNI3 mRNA was about 80% in the differentiated RCM-iPSC-CM, which was similar to the results in the myocardium of the same patient. The RCM-iPSC-CM demonstrated slower diastolic rate and longer diastolic time by cell motion analyses than Ctrl-iPSC-CM. Immunostaining showed a disarrayed sarcomeres in the RCM-iPSC-CM. Tthe structure of the thin filaments extracted from the RCM-iPSC-CMs observed with cryo-EM was close to that in the presence of calcium (contractile myocardium), even though the filaments were purified in the absence of calcium. Conclusions: The iPSC-derived cardiomyocytes could effectively represent the diastolic dysfunction of RCM. The structures of thin filaments were possibly explained for the phenotype of restrictive cardiomyopathy.

Abstract 18778: Patient-Derived Stem Cell Models of Pediatric Restrictive Cardiomyopathy Exhibit Increased Resting Tension and Cardiomyocyte Calcium Sensitivity

Introduction: Pediatric Restrictive Cardiomyopathy (RCM) is a genetic cardiomyopathy resulting from profoundly increased stiffness of the wall of the cardiac ventricle with normal or low normal contractility. Treatment options are limited, with most patients necessitating heart transplant. Therapies that can improve diastolic function are needed for this severe disease. However, development of novel therapies has been limited by a paucity of models of this rare disease. Here, we develop two novel models of pediatric RCM and use novel high-throughput functional analysis to measure diastolic dysfunction and defects in calcium handling. Hypothesis: Patient-derived human induced pluripotent stem cell (hiPSC) models of pediatric RCM will exhibit increased resting tension indicative of diastolic dysfunction, as well as increased calcium sensitivity. Methods: Cardiomyocytes were differentiated from hiPSCs derived from two pediatric patients with RCM, as well as a paired isogenic CRISPR-corrected lines. Cells were replated onto polyacrylamide gels and stained with calcium sensitive dyes, and contractility, resting tension, and calcium sensitivity were measured using a novel high-throughput functional imaging platform. Results: RCM cells from both patients showed elevated contractility, resting tension, and calcium sensitivity compared to their isogenic controls. Conclusions: Patient-derived RCM cells show alterations in calcium sensitivity and resting tension that recapitulate and explain the diastolic dysfunction seen in patients. These lines, combined with the high-throughput measurement platform described here, will provide a powerful platform for exploring novel therapeutic strategies for this severe disease.

Abstract 17551: Mapping the Interactome of FLNC in Restrictive Cardiomyopathy

Introduction: Filamin C (FLNC) is an actin crosslinking protein that organizes structural components of the sarcomere and signal transduction complexes. Human mutations in FLNC have been linked to dilated, hypertrophic and restrictive cardiomyopathies. The mechanism connecting mutations in FLNC to sarcomeric impairment remains undefined. We recently reported the ability to model FLNC cardiomyopathy using induced pluripotent stem cell (iPSC) derived engineered heart tissue. Here, we employ a knock-in approach to epitope tag endogenous alleles in iPSC derived cardiomyocytes to explore FLNC genotype-interactome relationships using affinity purification mass spectrometry. Methods: An iPSC line was generated from a patient with restrictive cardiomyopathy caused by an insertion deletion mutation in the ROD2 domain FLNC (c.7416_7418delGAA, p.Glu2472_Asn2473delinAsp). CRISPR-Cas9 was used to establish a corrected cell line as a wild type control. 3X-Flag motif was introduced to the N terminus of FLNC using CRISPR-Cas9. iPSCs were then differentiated into cardiomyocytes using standard techniques. Affinity purification mass spectrometry (AP-MS) was performed using the Flag epitope. Interaction data was analyzed using Perseus software. Gene ontology (GO) enrichment analysis was performed using ToppFun. Results: 3X-Flag insertion was confirmed using genomic sequencing. AP-MS identified 281 high confidence interactors of mutant FLNC and 208 interactors of wild type FLNC (FDR 0.01, log2FC &gt;1.5) when compared to IgG controls. Interestingly, 161 proteins were shared between the two genotypes. These were enriched in mitochondrial ribosomal proteins and phosphorylase kinase subunits, potentially revealing an unknown role of FLNC in mitochondria translation and metabolism. Thirty-three proteins were significantly differentially bound to mutant FLNC protein, including tropomyosin 4, caldesmon 1, and filamin A (FDR &lt;0.05, log2FC&gt;1). GO analysis of these proteins revealed enrichment of actin cytoskeleton elements, muscle contraction, and muscle system processes. Conclusions: Human mutations in FLNC lead to disruption of key protein interactions, revealing a potential mechanism for disease pathogenesis in FLNC cardiomyopathy.

Unveiling the structural and functional consequences of the p.D109G pathogenic mutation in human αB-Crystallin responsible for restrictive cardiomyopathy and skeletal myopathy

αB-Crystallin (αB-Cry) is expressed in many tissues, and mutations in this protein are linked to various diseases, including cataracts, Alzheimer's disease, Parkinson's disease, and several types of myopathies and cardiomyopathies. The p.D109G mutation, which substitutes a conserved aspartate residue involved in the interchain salt bridges, with glycine leads to the development of both restrictive cardiomyopathy (RCM) and skeletal myopathy. In this study, we generated this mutation in the α-Cry domain (ACD) which is crucial for forming the active chaperone dimeric state, using site-directed mutagenesis. After inducing expression in the bacterial host, we purified the mutant and wild-type recombinant proteins using anion exchange chromatography. Various spectroscopic evaluations revealed significant changes in the secondary, tertiary, and quaternary structures of human αB-Cry caused by this mutation. Furthermore, this pathogenic mutation led to the formation of protein oligomers with larger sizes than those of the wild-type protein counterpart. The mutant protein also exhibited increased chaperone activity and decreased chemical, thermal, and proteolytic stability. Atomic force microscopy (AFM), transmission electron microscopy (TEM), and fluorescence microscopy (FM) demonstrated that p.D109G mutant protein is more prone to forming amyloid aggregates. The misfolding associated with the p.D109G mutation may result in abnormal interactions of human αB-Cry with its natural partners (e.g., desmin), leading to the formation of protein aggregates. These aggregates can interfere with normal cellular processes and may contribute to muscle cell dysfunction and damage, resulting in the pathogenic involvement of the p.D109G mutant protein in restrictive cardiomyopathy and skeletal myopathy.

Abstract 16467: The Prevalence, Racial Distribution, and In Hospital Outcome of Percutaneous Coronary Intervention in Non ST Elevation Myocardial Infarction With Patients With Wild Type Transthyretin Cardiac Amyloidosis

Introduction: Epicardial coronary arteries are also a target for intramural amyloid deposits in cardiac amyloidosis beyond the myocardium. For patients with restrictive cardiomyopathy and some degree of stable chronic angina, the role of coronary revascularization has not been clearly shown to have additional benefits over medical management. In unstable angina and Non-ST-elevation acute coronary syndrome (NSTE-ACS) population, isolated observations have painted a grimmer prognosis. Hypothesis: We hypothesized that wild-type ATTR-CA patients with NSTEMI undergoing Percutaneous coronary interventions (PCI) had poor outcomes. We sought to establish their prevalence and uncover the determinants of these outcomes. Methods: A five-year retrospective inquiry of the National Inpatient Sample (NIS) database from 2016 to 2020 on all the patients admitted with a matching diagnosis to the ICD-10 code of interest. Results: Over the five-year span of our observation, about 1,116,170 patients were admitted to the hospital in the US with an NSTE-ACS diagnosis, of which 99% underwent PCI during the same hospitalization (1,116,065). Among the latter 1,505 patients (1%) had ATTR-CA. The most represented demographics in that subpopulation were men (69%), elderly about 74 years old on average (80%), and Whites (60%). The cumulative mortality rate among the ATTR-CA PCI group was higher (18%) than the general NSTE-ACS PCI (14%). Factors associated with survival at hospital discharge were female sex (p-value 0.008), and black race (p-value 0.019). Meanwhile, Asian race (p-value 0.0001), being in a teaching hospital (p-value 0.0001), medium to large size hospital (p-value 0.0001) were harbingers of poor outcomes including death (18%), prolonged hospitalization (about 9.5 days), and higher healthcare costs (about $127,319). Conclusions: PCI has mortality benefits in STEMI and unstable CAD. However, in the ATTR-CA with unstable CAD, this might not be the case as seen with the staggering 28% risk increase in mortality rates in our study. Percutaneous revascularization in wild-type ATTR-CA deserves its own category when clinicians are weighing the benefits and a multidisciplinary approach should be preferred.

Abstract 12265: Evaluation of Aortic Valve Calcification in Patients With Suspected Cardiac Amyloidosis

Introduction: Cardiac amyloidosis (CA) is characterized by the deposition of misfolded proteins within the heart causing a restrictive cardiomyopathy. Transthyretin (TTR) is one of the most common proteins implicated in CA, as well as in aortic stenosis (AS). The mechanism of TTR-CA associated AS is unclear. Hypothesis: We propose patients with severe AS being evaluated for transcatheter aortic valve replacement (TAVR) and suspected TTR-CA by echocardiogram will have an increased aortic valve calcium score. Secondary outcomes include post-procedural complications. Methods: This was a single-center, retrospective analysis of patients with severe AS referred to the Scripps system for TAVR between January 2017 and November 2022. A total of 496 patients were included and divided into two cohorts. The enriched (Likely CA) cohort consisted of patients with both IVS ≥1.2 cm and average mitral annular systolic s’ ≤ 6 cm/s. The unenriched (Unlikely CA) cohort met only one or none of the above echocardiographic criteria. Results: Of the 496 patients analyzed, 145 patients were in the Likely CA cohort and 351 patients were in the Unlikely CA cohort. Baseline demographics (Table 1A) and echocardiographic data (Table 1B) are shown. There was no statistically significant difference in the primary end point of aortic valve calcium score between the Likely CA and Unlikely CA cohort (p = 0.914). The Likely CA cohort had evidence of worse diastolic function and increased left ventricular dimensions. There was a non-significant trend towards an increased rate of post-procedural atrial fibrillation in the Likely CA cohort (p = 0.051). Otherwise, there was no significant difference in post-procedural complications between the two cohorts (Table 1C). Conclusions: In our analysis of patients with likely TTR-CA and AS compared to those with lone AS, there was no difference in aortic valve calcium score. This suggests aortic valve leaflet calcification is a process independent of TTR-CA.

Abstract 14114: An Extreme Case of Calcific Constrictive Pericarditis

Introduction: Constrictive pericarditis (CP) can lead to cardiac dysfunction and a range of clinical symptoms. However, differentiating it from conditions like restrictive cardiomyopathy can be challenging due to the overlapping features. Case Presentation: We present a case of a 61-year-old female with a history of atrial flutter and subsequent atrial fibrillation, experiencing worsening dyspnea on exertion, lip cyanosis, and upper abdominal constriction. Extensive diagnostic workup, including Echo, CT scan, and cardiac MRI, revealed severe biatrial enlargement, ventricular interdependence, elevated filling pressures, reduced cardiac output, and extensive pericardial thickening and calcifications ( Figures 1.a and 1.b ). These findings supported the diagnosis of extensive CP. Discussion: CP is often missed and delayed in diagnosis due to its complex hemodynamics and the non-specific symptoms. Typically, the initial imaging modality to be performed is an Echo. Specific findings such as dilated vena cava, preserved tissue velocity with annuls paradoxus, abnormal respiratory septal shift, and respiratory variations in mitral/tricuspid inflow should be first clues for potential diagnosis. Furthermore, evaluation of the hepatic vein with diastolic flow reversal during expiration is a key finding. Lack of respiratory variation in the SVC is also important. Cardiac CT will assess pericardial thickness and calcification, while cardiac MRI is key for the diagnosis by showing the pericardial thickness and fibrosis as well as the septal respiratory shift and venous congestion. An invasive hemodynamic study might be required if imaging is inconclusive. this patient’s presentation, imaging findings, exercise test results and collectively supported considering radical pericardiectomy. Conclusions: This report highlights the diagnostic challenges related to CP and the importance employing a multimodality imaging approach for accurate diagnosis.

Abstract 16780: Single Cell Profiles of Human Heart Failure and Myocardial Diseases

Background: Heart failure represents the end-stage of a range of diseases which adversely impact the heart muscle. The extent by which cellular and molecular mechanisms differ between myocardial diseases in heart failure remains incompletely understood. Methods: We performed isolation and droplet-based RNA-sequencing of 394 247 single nuclei from 103 explanted hearts from transplant and ventricular assist device recipients and 7 unused donor hearts without heart disease. After sample and nuclei level quality control, doublet removal and sample integration; principal component analysis and shared nearest neighbor clustering were used to identify distinct cell populations. Cell type composition and transcriptomic profiles were compared across donor hearts and 10 myocardial diseases (hypertrophic, dilated, ischemic, restrictive, arrythmogenic and non-compaction cardiomyopathy; rheumatic and congenital heart disease; cardiac amyloidosis and graft rejection; n=1-45/group). Results: We identified and manually annotated 14 distinct cell populations that were present across controls and myocardial diseases, including transcriptionally diverse subgroups of cardiomyocytes, endothelial cells and pericytes. Compared to controls, we observed disease-specific differences in cell populations with regards to composition, heterogeneity, and specific transcriptional profiles. Conclusions: Our results reveal differences in single cell profiles of individual heart muscle diseases compared to controls without heart disease.

Abstract 14418: Prevalence, Characteristics, and Factors Associated With Atrial Fibrillation and Flutter in Patients With Transthyretin Cardiac Amyloidosis

Introduction: Transthyretin cardiac amyloidosis (ATTR-CA) is an increasingly recognized form of restrictive cardiomyopathy in older adults. Adverse chamber remodeling from amyloid infiltration predisposes these patients to tachyarrhythmias such as atrial fibrillation/flutter (AF), which increase the risk of thromboembolic events. The goal of our study was to explore the prevalence, phenotypic characteristics, and factors associated with AF in ATTR-CA patients. Methods: This is a retrospective cohort study of 419 patients diagnosed with ATTR-CA comparing demographics and clinical characteristics between patients with and without AF at baseline. AF was ascertained based on review of prior electrocardiogram, long term monitors when performed, pacemaker interrogations if applicable, and charted history. Binary logistic regression was then performed to determine factors associated with prevalence of AF. Results: AF was prevalent in 58% (n=244) of ATTR-CA patients on initial presentation. Compared to those without AF, individuals with AF were older, of white race, exhibited NYHA class III-IV symptoms, and less frequently had variant disease (ATTRv-CA). They also had more prior stroke/TIA, chronic kidney disease, implanted pacemakers, and need for loop diuretics at baseline (Table 1). AF patients more consistently had Columbia stage II-III disease as per established biomarker cutoffs and greater left atrial volume index on echocardiogram (LAVI). On multivariable logistic regression, per point increase in Columbia score (OR 1.48, 95% CI 1.25-1.75) and per mL/m 2 increase in LAVI (OR 1.05, 95% CI 1.02-1.08) were predictive of prevalent AF, while ATTRv-CA (OR 0.19, 95% CI 0.07-0.55) was protective, all p&lt;0.05. Conclusions: More than half of ATTR-CA patients have preexisting AF. Wild-type ATTR-CA, greater Columbia staging, and a dilated LA are the main clinical factors associated with prevalent AF.