Hypertrophic Cardiomyopathy With Left Ventricular Systolic Dysfunction: Insights From the SHaRe Registry

2024 AHA/ACC/AMSSM/HRS/PACES/SCMR Guideline for the Management of Hypertrophic Cardiomyopathy: A Report of the American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines

AIM

The "2024 AHA/ACC/AMSSM/HRS/PACES/SCMR Guideline for the Management of Hypertrophic Cardiomyopathy" provides recommendations to guide clinicians in the management of patients with hypertrophic cardiomyopathy.

METHODS

A comprehensive literature search was conducted from September 14, 2022, to November 22, 2022, encompassing studies, reviews, and other evidence on human subjects that were published in English from PubMed, EMBASE, the Cochrane Library, the Agency for Healthcare Research and Quality, and other selected databases relevant to this guideline. Additional relevant studies, published through May 23, 2023, during the guideline writing process, were also considered by the writing committee and added to the evidence tables, where appropriate.

STRUCTURE

Hypertrophic cardiomyopathy remains a common genetic heart disease reported in populations globally. Recommendations from the "2020 AHA/ACC Guideline for the Diagnosis and Treatment of Patients With Hypertrophic Cardiomyopathy" have been updated with new evidence to guide clinicians.

2024 AHA/ACC/AMSSM/HRS/PACES/SCMR Guideline for the Management of Hypertrophic Cardiomyopathy: A Report of the American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines

AIM

The "2024 AHA/ACC/AMSSM/HRS/PACES/SCMR Guideline for the Management of Hypertrophic Cardiomyopathy" provides recommendations to guide clinicians in the management of patients with hypertrophic cardiomyopathy.

METHODS

A comprehensive literature search was conducted from September 14, 2022, to November 22, 2022, encompassing studies, reviews, and other evidence on human subjects that were published in English from PubMed, EMBASE, the Cochrane Library, the Agency for Healthcare Research and Quality, and other selected databases relevant to this guideline. Additional relevant studies, published through May 23, 2023, during the guideline writing process, were also considered by the writing committee and added to the evidence tables, where appropriate.

STRUCTURE

Hypertrophic cardiomyopathy remains a common genetic heart disease reported in populations globally. Recommendations from the "2020 AHA/ACC Guideline for the Diagnosis and Treatment of Patients With Hypertrophic Cardiomyopathy" have been updated with new evidence to guide clinicians.

Emerging Themes in Genetics of Hypertrophic Cardiomyopathy: Current Status and Clinical Application

Hypertrophic cardiomyopathy (HCM), defined clinically by the presence of unexplained left ventricular hypertrophy (LVH), with wall thickness ≥ 1.5 cm, is a phenotype in search of a diagnosis, which is most often a genetically determined, cardiac exclusive, or systemic disorder. Familial evaluation and genetic testing are required for definitive diagnosis. The role of genetic findings in predicting development of disease, outcomes, and increasingly to guide management is evolving with access to larger data sets. The specific mutation and sex of the patient are important determinants that ultimately are likely to guide management. The genetic/familial evaluation is influenced by the accuracy of the clinical diagnosis and the extent/expertise of the genetic laboratory. Genetic testing in a patient with unexplained LVH without systemic manifestations will yield a definite/likely pathogenetic mutation in a sarcomere (30%-50%), regulatory/functional (10%-15%) or metabolic/syndromic (< 5%) gene associated with Mendelian inheritance. The importance of oligo- and polygenic determinants, usually in the absence of Mendelian inheritance, is under investigation with important implications, particularly related to familial evaluation and definition of risk of disease development in relatives of probands. The results of genetic testing are increasingly important in management strategies related to the use of the implantable cardioverter defibrillator for prevention of sudden death, use of myosin inhibitors for refractory symptoms in patients with and without outflow tract obstruction, and-on the immediate horizon-gene therapy. This review will focus on genetic and outcome data in sarcomeric HCM, and minor causative genes with robust evidence of their association will also be considered.

From Atrial Fibrillation Management to Atrial Myopathy Assessment: The Evolving Concept of Left Atrium Disease in Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most prevalent genetically inherited cardiovascular disorder in adults and a significant cause of heart failure and sudden cardiac death. Historically, atrial fibrillation (AF) has been considered as a critical aspect in HCM patients as it is considered to be a marker of disease progression, escalates the frequency of heart failure hospitalisations, increases the risk of thromboembolic events, and worsens quality of life and outcome. Increasing evidence suggests that AF is the result of a subtle long-standing process that starts early in the history of HCM. The process of left atrial dilation accompanied by morphologic and functional remodelling is the quintessential prerequisite for the onset of AF. This review aims to describe the current understanding of AF pathophysiology in HCM, emphasising the role of left atrial myopathy in its development. In addition, we discuss risk factors and management strategies specific to AF in the context of HCM, providing insights into the complexities and challenges of treating this specific patient population.

The Revolution of Cardiac Myosin Inhibitors in Patients With Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most common genetic cardiomyopathy worldwide and causes significant morbidity and mortality. For decades, medical treatment options have been limited and untargeted, with frequent need for invasive interventions not readily accessible to many HCM patients. More recently, our understanding of the genetic basis and pathophysiologic mechanism of HCM has grown significantly, leading to the discovery of a new class of medications, cardiac myosin inhibitors (CMIs), that shift myosin into the super-relaxed state to counteract the hypercontractility in HCM. Subsequent clinical trials have proven the mechanism and efficacy of CMIs in humans with obstructive HCM, and additional trials are under way in patients with nonobstructive HCM. With favourable results in the completed clinical trials and ongoing research on the horizon, CMIs represent a bright new era in the targeted management of HCM. This review is focused on the discovery of CMIs, provides a summary of the results of clinical trials to date, provides clinicians with a roadmap for implementing CMIs into practice, and identifies gaps in our current understanding as well as areas of ongoing investigation.

Clinical characteristics and outcome of end stage hypertrophic cardiomyopathy: Role of age and heart failure phenotypes

BACKGROUND

A minority of patients with hypertrophic cardiomyopathy (HCM) presents advanced heart failure (HF) during their clinical course, in the context of left ventricular (LV) remodeling with reduced LV ejection fraction (LVEF), or of severe diastolic dysfunction without impaired LVEF. Aim of this study was to describe a multicentric end stage (ES) HCM population and analyze clinical course and outcome among its different phenotypes.

METHODS

Data of all HCM patients from 7 Italian referral centres were retrospectively evaluated. ES was diagnosed in presence of: LVEF <50% (ES-rEF) or NYHA functional class ≥II with severe diastolic dysfunction (ES-pEF). Outcomes were: HCM-related and all-cause mortality; combined arrhythmic events; advanced HF treatments.

RESULTS

Study population included 331 ES patients; 87% presented ES-rEF and 13% ES-pEF. At ES recognition, patients with ES-pEF were more commonly females, had more frequently NYHA III/IV, atrial fibrillation and greater maximal LV wall thickness. Over a median follow-up of 5.6 years, 83 (25%) patients died, 46 (15%) experienced arrhythmic events and (26%) 85 received advanced HF treatments. Incidence of HCM-related and all-cause mortality, and of combined arrhythmic events did not differ in ES-pEF and ES-rEF patients, but ES-pEF patients were less likely to receive advanced HF treatments. Older age at ES recognition was an independent predictor of increased HCM-related mortality (p = 0.01) and reduced access to advanced HF treatments (p < 0.0001).

CONCLUSIONS

Two different HCM-ES phenotypes can be recognized, with ES-pEF showing distinctive features at ES recognition and receiving less frequently advanced HF treatments. Older age at ES recognition has a major impact on outcomes.

Signaling Pathways Associated With Prior Cardiovascular Events in Hypertrophic Cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is the most common genetic cardiomyopathy. A subset of patients experience major adverse cardiovascular events (MACEs), including arrhythmias, strokes and heart failure. However, the molecular mechanisms underlying MACEs in HCM are still not well understood. Therefore, we conducted a multicenter case-control study of patients with HCM, comparing those with and without prior histories of MACEs to identify dysregulated signaling pathways through plasma proteomics profiling.

METHODS

We performed plasma proteomics profiling of 4986 proteins. We developed a proteomics-based discrimination model in patients enrolled at 1 institution (training set) and externally validated the model in patients enrolled at another institution (test set). We performed pathway analysis of proteins dysregulated in patients with prior MACEs.

RESULTS

A total of 402 patients were included, with 278 in the training set and 124 in the test set. In this cohort, 257 (64%) patients had prior MACEs (172 in the training set and 85 in the test set). Using the proteomics-based model from the training set, the area under the receiver operating characteristic curve was 0.82 (95% confidence interval, 0.75-0.90) in the test set. Patients with prior MACEs demonstrated dysregulation in pathways known to be associated with MACEs (eg, TGF-β) and novel pathways (eg, Ras-MAPK and associated pathways).

CONCLUSIONS

In this multicenter study of 402 patients with HCM, we identified both known and novel pathways dysregulated in a subset of patients with more advanced disease.

Advances in Multi-Modality Imaging in Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is characterized by abnormal growth of the myocardium with myofilament disarray and myocardial hyper-contractility, leading to left ventricular hypertrophy and fibrosis. Where culprit genes are identified, they typically relate to cardiomyocyte sarcomere structure and function. Multi-modality imaging plays a crucial role in the diagnosis, monitoring, and risk stratification of HCM, as well as in screening those at risk. Following the recent publication of the first European Society of Cardiology (ESC) cardiomyopathy guidelines, we build on previous reviews and explore the roles of electrocardiography, echocardiography, cardiac magnetic resonance (CMR), cardiac computed tomography (CT), and nuclear imaging. We examine each modality's strengths along with their limitations in turn, and discuss how they can be used in isolation, or in combination, to facilitate a personalized approach to patient care, as well as providing key information and robust safety and efficacy evidence within new areas of research.

Role of Imaging in the Diagnosis, Evaluation, and Management of Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is increasingly recognized and may benefit from the recent approval of new, targeted medical therapy. Successful management of HCM is dependent on early and accurate diagnosis. The lack of a definitive diagnostic test, the wide variation in phenotype and the commonness of phenocopy conditions, and the presence of normal or hyperdynamic left ventricular function in most patients makes HCM a condition that is highly dependent on imaging for all aspects of management including, diagnosis, classification, predicting risk of complications, detecting complications, identifying risk for ventricular arrhythmias, evaluating choice of therapy and monitoring therapy, intraprocedural guidance, and screening family members. Although echocardiographic imaging remains the mainstay in the diagnosis and subsequent management of HCM, this disease clearly requires multimethod imaging for various aspects of optimal patient care. Advances in echocardiography hardware and techniques, development and refinement of imaging with computed tomography, magnetic resonance, and nuclear scanning, and the emergence of very focused assessments such as diastology and fibrosis imaging have all advanced the diagnosis and management of HCM. In this review, we discuss the relative utility and evidence support for these imaging approaches to contribute to improve patient outcomes.

Genetic Testing in Hypertrophic Cardiomyopathy

Genetic testing is an important tool in the diagnosis and management of patients and families with hypertrophic cardiomyopathy (HCM). Modern testing can identify causative variants in 30 to >60% of patients, with probability of a positive test varying with baseline characteristics such as known family history of HCM. Patients diagnosed with HCM should be offered genetic counseling and genetic testing as appropriate. Standard multigene panels evaluate sarcomeric genes known to cause HCM as well as genetic conditions that can mimic HCM but require different management. Positive genetic testing (finding a pathogenic or likely pathogenic variant) helps to clarify diagnosis and assists in family screening. If there is high confidence that an identified variant is the cause of HCM, at-risk family members can pursue predictive testing to determine if they are truly at risk or if they can be dismissed from serial screening based on whether they inherited the family's causative variant. Interpreting test results can be complex, and providers should make use of multidisciplinary teams as well as evidence-based resources to obtain the best possible understanding of pathogenicity.

Cancer Treatment-Related Complications in Patients With Hypertrophic Cardiomyopathy

OBJECTIVE

To describe the potential clinical cardiotoxicity of oncological treatments in a cohort of consecutive patients with hypertrophic cardiomyopathy (HCM), systematically followed-up at two national referral centers for HCM. Cardiotoxicity relates to the direct effects of cancer-related treatment on heart function, commonly presenting as left ventricular contractile dysfunction. However, limited data are available regarding cardiotoxic effects on HCM as most studies have not specifically analyzed the effects of oncological treatment in HCM populations. This gap in knowledge may lead to unjustified restriction of HCM patients from receiving curative cancer treatments.

METHODS

We retrospectively analyzed clinical and instrumental data of all consecutive HCM patients who underwent oncological treatment between January 2000 and December 2020 collected in a centralized database.

RESULTS

Of 3256 HCM patients, 121 (3.7%) had cancer; 110 (90.9%) underwent oncological surgery, 45 (37.2%) received chemotherapy, and 22 (18.2%) received chest radiation therapy (cRT). After a median follow-up of 5.2 years (Q1-Q3: 2-13 years) from oncological diagnosis, 32 patients died. The cumulative survival at 5 years was 79.9%. The cause of death was mainly attributed to the oncological condition, whereas four patients died of sudden cardiac death without receiving previous chemotherapy or cRT. No patient interrupted or reduced the dose of oncological treatment due to cardiac dysfunction. No sustained ventricular tachyarrhythmia was induced by chemotherapy or radiation therapy.

CONCLUSION

Cancer treatment was well tolerated in HCM patients. In our consecutive series, none died of cardiovascular complications induced by chemotherapy or cRT and they did not require interruption or substantial treatment tapering due to cardiovascular toxic effects. Although a multidisciplinary evaluation is necessary and regimens must be tailored individually, the diagnosis of HCM per se should not be considered a contraindication to receive optimal curative cancer treatment.

Long-term post-transplantation outcomes in patients with hypertrophic cardiomyopathy: Single-center 35-year experience

BACKGROUND

Heart transplantation (HT) is the only option for most patients with end-stage heart failure and hypertrophic cardiomyopathy (HCM) who fail medical therapy. Data on the long-term outcomes post-transplant in HCM individuals remain scarce.

METHODS

We analyzed data of 319 adult patients who underwent HT between 1984 and 2019. Patients were followed for cardiac allograft rejection, cardiac allograft vasculopathy (CAV), death, or re-transplantation.

RESULTS

Outcomes of 24 patients with HCM, 160 with ischemic, and 135 with dilated cardiomyopathy were compared. During a mean follow-up of 11.6 ± 7.2 (max 27.8), 16.7 ± 8.2 (max 32.7), and 16.1 ± 9.7 (max 34.6) years after HT in hypertrophic, ischemic, and dilated cardiomyopathy groups, respectively: 10-year survival rate was 67%, 62%, 69%, respectively (p = .04). Post-transplantation, HCM individuals more often than the other two studied groups required prolonged inotropic support (37%, 12%, 17%, respectively, p = .02), temporary mechanical circulatory support (45%, 13%, 14%, respectively, p < .01), and renal replacement therapy immediately post-HT (55%, 19%, 24%, respectively, p < .01). No significant inter-group differences were noted in the 10-year freedom from acute allograft rejection (38%, 46%, 43%, respectively, p = .38) or 10-year freedom from CAV (88%, 78%, 81%, respectively, p = .57).

CONCLUSIONS

The long-term post-transplant prognosis of adult patients with hypertrophic cardiomyopathy is favorable despite more challenging immediate post-HT course.

Exploring the Connection Between Relaxed Myosin States and the Anrep Effect

The Anrep effect is an adaptive response that increases left ventricular contractility following an acute rise in afterload. Although the mechanistic origin remains undefined, recent findings suggest a two-phase activation of resting myosin for contraction, involving strain-sensitive and posttranslational phases. We propose that this mobilization represents a transition among the relaxed states of myosin-specifically, from the super-relaxed (SRX) to the disordered-relaxed (DRX)-with DRX myosin ready to participate in force generation. This hypothesis offers a unified explanation that connects myosin's SRX-DRX equilibrium and the Anrep effect as parts of a singular phenomenon. We underscore the significance of this equilibrium in modulating contractility, primarily studied in the context of hypertrophic cardiomyopathy, the most common inherited cardiomyopathy associated with diastolic dysfunction, hypercontractility, and left ventricular hypertrophy. As we posit that the cellular basis of the Anrep effect relies on a two-phased transition of myosin from the SRX to the contraction-ready DRX configuration, any dysregulation in this equilibrium may result in the pathological manifestation of the Anrep phenomenon. For instance, in hypertrophic cardiomyopathy, hypercontractility is linked to a considerable shift of myosin to the DRX state, implying a persistent activation of the Anrep effect. These valuable insights call for additional research to uncover a clinical Anrep fingerprint in pathological states. Here, we demonstrate through noninvasive echocardiographic pressure-volume measurements that this fingerprint is evident in 12 patients with hypertrophic obstructive cardiomyopathy before septal myocardial ablation. This unique signature is characterized by enhanced contractility, indicated by a leftward shift and steepening of the end-systolic pressure-volume relationship, and a prolonged systolic ejection time adjusted for heart rate, which reverses post-procedure. The clinical application of this concept has potential implications beyond hypertrophic cardiomyopathy, extending to other genetic cardiomyopathies and even noncongenital heart diseases with complex etiologies across a broad spectrum of left ventricular ejection fractions.

The use of cardiac magnetic resonance in hypertrophic cardiomyopathy over the past 10 years [2013-2023]: a CiteSpace-based bibliometric analysis

Background

Hypertrophic cardiomyopathy (HCM) is a common genetic cardiac disorder characterized by the hypertrophy of a segment of the myocardium. Cardiac magnetic resonance (CMR) has been widely used in the assessment of HCM. However, no bibliometric assessment has been conducted on the progress of research in this field. This study thus aimed to examine the current state of research into the application of CMR in HCM and the hotspots and trends that have emerged in this field over the past decade.

Methods

A systematic search was conducted on the Web of Science regarding CMR in the assessment of HCM. The databases were searched from 2013 to June 2023. CiteSpace is an application that can be used to characterize the underlying knowledge of the scientific literature in a given field. We used it to analyze the relationship between publication year and country, institution, journal, author, bibliography, and keywords in the field of CMR for the assessment of HCM.

Results

A total of 1,427 articles were included in the analysis. In the assessment of HCM, the findings from the past decade have consistently demonstrated a progressive rise in the quantity of articles pertaining to CMR. The country with the largest number of publications was the United States [310], and the institution with the greatest number of publications was the University College London [45]. The analysis of keywords revealed the diagnosis and management of HCM with CMR to be the current research focus and emerging trend within this academic field.

Conclusions

This study used a novel approach to visually analyze the use of CMR in HCM assessment. The current research trajectory in CMR consists of the diagnosis and management of patients with HCM. Although most studies confirmed the indispensability of CMR in the assessment of HCM, larger-scale cohorts are still needed to more comprehensively evaluate the role of CMR in the differential diagnosis, pre- and post-treatment assessment, and long-term management of patients with HCM.

Profiling cardiomyocytes at single cell resolution reveals COX7B could be a potential target for attenuating heart failure in cardiac hypertrophy

Cardiac hypertrophy can develop to end-stage heart failure (HF), which inevitably leading to heart transplantation or death. Preserving cardiac function in cardiomyocytes (CMs) is essential for improving prognosis in hypertrophic cardiomyopathy (HCM) patients. Therefore, understanding transcriptomic heterogeneity of CMs in HCM would be indispensable to aid potential therapeutic targets investigation. We isolated primary CM from HCM patients who had extended septal myectomy, and obtained transcriptomes in 338 human primary CM with single-cell tagged reverse transcription (STRT-seq) approach. Our results revealed that CMs could be categorized into three subsets in nonfailing HCM heart: high energy synthesis cluster, high cellular metabolism cluster and intermediate cluster. The expression of electron transport chain (ETC) was up-regulated in larger-sized CMs from high energy synthesis cluster. Of note, we found the expression of Cytochrome c oxidase subunit 7B (COX7B), a subunit of Complex IV in ETC had trends of positively correlation with CMs size. Further, by assessing COX7B expression in HCM patients, we speculated that COX7B was compensatory up-regulated at early-stage but down-regulated in failing HCM heart. To test the hypothesis that COX7B might participate both in hypertrophy and HF progression, we used adeno associated virus 9 (AAV9) to mediate the expression of Cox7b in pressure overload-induced mice. Mice in vivo data supported that knockdown of Cox7b would accelerate HF and Cox7b overexpression could restore partial cardiac function in hypertrophy. Our result highlights targeting COX7B and preserving energy synthesis in hypertrophic CMs could be a promising translational direction for HF therapeutic strategy.

Circulating Acylcarnitines Associated with Hypertrophic Cardiomyopathy Severity: an Exploratory Cross-Sectional Study in MYBPC3 Founder Variant Carriers

Hypertrophic cardiomyopathy (HCM) is a relatively common genetic heart disease characterised by myocardial hypertrophy. HCM can cause outflow tract obstruction, sudden cardiac death and heart failure, but severity is highly variable. In this exploratory cross-sectional study, circulating acylcarnitines were assessed as potential biomarkers in 124 MYBPC3 founder variant carriers (59 with severe HCM, 26 with mild HCM and 39 phenotype-negative [G + P-]). Elastic net logistic regression identified eight acylcarnitines associated with HCM severity. C3, C4, C6-DC, C8:1, C16, C18 and C18:2 were significantly increased in severe HCM compared to G + P-, and C3, C6-DC, C8:1 and C18 in mild HCM compared to G + P-. In multivariable linear regression, C6-DC and C8:1 correlated to log-transformed maximum wall thickness (coefficient 5.01, p = 0.005 and coefficient 0.803, p = 0.007, respectively), and C6-DC to log-transformed ejection fraction (coefficient -2.50, p = 0.004). Acylcarnitines seem promising biomarkers for HCM severity, however prospective studies are required to determine their prognostic value.

Evolving Contemporary Management of Atrial Fibrillation in Hypertrophic Cardiomyopathy

Atrial fibrillation (AF) is the most common sustained arrhythmia in hypertrophic cardiomyopathy (HCM) with clinical and subclinical episodes occurring in nearly one-half of patients. AF in HCM historically has been characterized as a decisive disease complication associated with substantial risk for thromboembolic stroke and increased morbidity and mortality. However, there have been many advances in treatment strategy resulting in improved outcomes for this patient group. For example, stroke risk in HCM has been greatly reduced by using systemic oral anticoagulation initiated after the first clinical (symptomatic) AF episode, usually with preference given to direct anticoagulants over warfarin. In contrast, stroke risk scoring systems (such as CHA2DS2-VASc score) are not informative in HCM given the substantial potential for stroke events in patients with low scores, and therefore should not be used for anticoagulation decisions in this disease. A novel risk score specifically designed for HCM (HCM-AF score) can reliably identify most patients with HCM at risk for future AF. Although a strategy focused on controlling ventricular rate is effective in asymptomatic (or minimally symptomatic) patients with AF, restoring and maintaining sinus rhythm is required for most patients with marked AF symptom burden and impaired quality of life. Several antiarrhythmic drugs such as sotalol, disopyramide, and amiodarone, can be effective in suppressing AF episodes; albeit safe, long-term efficacy is supported by only limited data. Catheter AF ablation has emerged as an important treatment option for some patients, although freedom from AF after a single ablation is relatively low (35% at 3 years), multiple ablations and the concomitant use of antiarrhythmic drugs can control AF with more than two-thirds of patients maintaining sinus rhythm at 5 years. Surgical AF ablation with biatrial Cox-Maze IV performed as an adjunctive procedure during myectomy can reduce symptomatic AF episodes (70% of patients free from AF at 5 years). For the vast majority of patients who have HCM with AF, the implementation of contemporary therapies has allowed for improved quality of life and low HCM-related mortality.

Mavacamten: a first-in-class myosin inhibitor for obstructive hypertrophic cardiomyopathy

Mavacamten is a first-in-class, targeted, cardiac-specific myosin inhibitor approved by the US Food and Drug Administration for the treatment of adults with symptomatic New York Heart Association Classes II and III obstructive hypertrophic cardiomyopathy (oHCM). Mavacamten was developed to target the hyper-contractile phenotype, which plays a critical role in the pathophysiology of the disease. In Phase 2 and 3 clinical trials, mavacamten was well tolerated, reduced left ventricular outflow tract gradients, improved exercise capacity and symptoms, and was associated with improvements in other clinically relevant parameters, such as patient-reported outcomes and circulating biomarkers. In addition, treatment with mavacamten was associated with evidence of favourable cardiac remodelling in multi-modality imaging studies. Mavacamten substantially reduced guideline eligibility for septal reduction therapy candidates with oHCM and drug-refractory symptoms. In this article, the available efficacy and safety data from completed and ongoing clinical studies of mavacamten in patients with symptomatic oHCM are reviewed. Longer term extension studies may help address questions related to the positioning of mavacamten in current oHCM management algorithms, interactions with background therapy, as well as the potential for disease modification beyond symptomatic relief of left ventricular outflow tract obstruction.

End-stage Hypertrophic Cardiomyopathy with Advanced Heart Failure in Patients Carrying MYH7 R453 Variants: A Case Series

The MYH7 R453 variant has been identified in inherited hypertrophic cardiomyopathy (HCM) and is associated with sudden death and a poor prognosis. The detailed clinical course of HCM with the MYH7 R453 variant, from a preserved to a reduced left ventricular ejection fraction, has not been reported. We identified the MYH7 R453C and R453H variants in three patients who progressively developed advanced heart failure requiring circulatory support and summarized the clinical course and echocardiographic parameters of these patients over the years. Because of the rapid disease progression, we consider genetic screening for patients with HCM imperative for future prognosis stratification.

State-of-the-art document on optimal contemporary management of cardiomyopathies

Cardiomyopathies represent significant contributors to cardiovascular morbidity and mortality. Over the past decades, a progress has occurred in characterization of the genetic background and major pathophysiological mechanisms, which has been incorporated into a more nuanced diagnostic approach and risk stratification. Furthermore, medications targeting core disease processes and/or their downstream adverse effects have been introduced for several cardiomyopathies. Combined with standard care and prevention of sudden cardiac death, these novel and emerging targeted therapies offer a possibility of improving the outcomes in several cardiomyopathies. Therefore, the aim of this document is to summarize practical approaches to the treatment of cardiomyopathies, which includes the evidence-based novel therapeutic concepts and established principles of care, tailored to the individual patient aetiology and clinical presentation of the cardiomyopathy. The scope of the document encompasses contemporary treatment of dilated, hypertrophic, restrictive and arrhythmogenic cardiomyopathy. It was based on an expert consensus reached at the Heart Failure Association online Workshop, held on 18 March 2021.

Genetic Contribution to End-Stage Cardiomyopathy Requiring Heart Transplantation

BACKGROUND

Many cardiovascular disorders propel the development of advanced heart failure that necessitates cardiac transplantation. When treatable causes are excluded, studies to define causes are often abandoned, resulting in a diagnosis of end-stage idiopathic cardiomyopathy. We studied whether DNA sequence analyses could identify unrecognized causes of end-stage nonischemic cardiomyopathy requiring heart transplantation and whether the prevalence of genetic causes differed from ambulatory cardiomyopathy cases.

METHODS

We performed whole exome and genome sequencing of 122 explanted hearts from 101 adult and 21 pediatric patients with idiopathic cardiomyopathy from a single center. Data were analyzed for pathogenic/likely pathogenic variants in nuclear and mitochondrial genomes and assessed for nonhuman microbial sequences. The frequency of damaging genetic variants was compared among cardiomyopathy cohorts with different clinical severity.

RESULTS

Fifty-four samples (44.3%) had pathogenic/likely pathogenic cardiomyopathy gene variants. The frequency of pathogenic variants was similar in pediatric (42.9%) and adult (43.6%) samples, but the distribution of mutated genes differed (P=8.30×10-4). The prevalence of causal genetic variants was significantly higher in end-stage than in previously reported ambulatory adult dilated cardiomyopathy cases (P<0.001). Among remaining samples with unexplained causes, no damaging mitochondrial variants were identified, but 28 samples contained parvovirus genome sequences, including 2 samples with 6- to 9-fold higher levels than the overall mean levels in other samples.

CONCLUSIONS

Pathogenic variants and viral myocarditis were identified in 45.9% of patients with unexplained end-stage cardiomyopathy. Damaging gene variants are significantly more frequent among transplant compared with patients with ambulatory cardiomyopathy. Genetic analyses can help define cause of end-stage cardiomyopathy to guide management and risk stratification of patients and family members.

Ventricular arrhythmias in patients with hypertrophic cardiomyopathy: Prevalence, distribution, predictors, and outcome

BACKGROUND

Hypertrophic cardiomyopathy (HCM) carries an increased risk of sudden cardiac death. Ventricular fibrillation (VF) is thought to be the common culprit arrhythmia.

OBJECTIVE

The purpose of this study was to describe the incidence and predictors of sustained ventricular arrhythmias (VTAs) in HCM patients.

METHODS

We retrospectively analyzed all patients with HCM and an implantable cardioverter-defibrillator (ICD) from a prospectively derived registry in 2 tertiary medical centers. Clinical, electrocardiographic, echocardiographic, ICD interrogation, and genetic data were collected and compared, first between patients with and without VTAs and then between patients with only VF and those with ventricular tachycardia (VT) with or without VF.

RESULTS

Of the 1328 HCM patients, 207 (145 [70%] male; mean age 33 ± 16 years) were implanted with ICDs. Over a mean follow-up of 10 ± 6 years, 37 patients with ICDs (18%) developed sustained VTAs. These were associated with a family history of sudden cardiac death and a personal history of VTAs (P = .036 and P = .001, respectively). Sustained monomorphic VT was the most common arrhythmia (n = 26, 70%) and was linked to decreased left ventricular (LV) ejection fraction and increased LV end-systolic and end-diastolic diameters. Antitachycardia pacing (ATP) successfully terminated 258 (79%) of the 326 VT events. Mortality rates were comparable between patients with and without VTAs (4 [11%] vs 29 [17%]; P = .42) and between those with and without ICDs (24 [16%] vs 85 [20%]; P = .367).

CONCLUSION

VT rather than VF is the most common arrhythmia in patients with HCM; it is amenable to ATP and is associated with lower LV ejection fraction and higher LV diameters. Therefore, ATP-capable devices may be considered in HCM patients with these LV features.

Imaging in Hypertrophic Cardiomyopathy: Beyond Risk Stratification

A multimodality imaging evaluation in hypertrophic cardiomyopathy is often used for risk stratification. Recent developments in imaging have allowed for better diagnosis, prognosis, and decision-making for a variety of therapies from medical to interventional. Echocardiography and magnetic resonance have been integral in evaluating subtype, left ventricular function, tissue characterization, left atrial measurements, valvular function, and presence of left ventricular aneurysm and outflow tract obstruction. These factors have helped to quantify risk of atrial fibrillation and determine the likely usefulness of pharmacologic therapy and septal reduction therapy. This review covers these in detail.

Left ventricular global longitudinal strain as a prognosticator in hypertrophic cardiomyopathy with a low-normal left ventricular ejection fraction

AIMS

The aim of this study was to investigate the prognostic utility of left ventricular (LV) global longitudinal strain (LV-GLS) in patients with hypertrophic cardiomyopathy (HCM) and an LV ejection fraction (LVEF) of 50-60%.

METHODS AND RESULTS

This retrospective cohort study included 349 patients with HCM and an LVEF of 50-60%. The primary outcome was a composite of cardiovascular death, including sudden cardiac death (SCD) and SCD-equivalent events. The secondary outcomes were SCD/SCD-equivalent events, cardiovascular death (including SCD), and all-cause death. The final analysis included 349 patients (mean age 59.2 ± 14.2 years, men 75.6%). During a median follow-up of 4.1 years, the primary outcome occurred in 26 (7.4%), while the secondary outcomes of SCD/SCD-equivalent events, cardiovascular death, and all-cause death occurred in 15 (4.2%), 20 (5.7%), and 34 (9.7%), respectively. After adjusting for age, atrial fibrillation, ischaemic stroke, LVEF, and left atrial volume index, absolute LV-GLS (%) was independently associated with the primary outcome [adjusted hazard ratio (HR) 0.88, 95% confidence interval (CI) 0.788-0.988, P = 0.029]. According to receiver operating characteristic analysis, 10.5% is an optimal cut-off value for absolute LV-GLS in predicting the primary outcome. Patients with an absolute LV-GLS ≤ 10.5% had a higher risk of the primary outcome than those with an absolute LV-GLS > 10.5% (adjusted HR 2.54, 95% CI 1.117-5.787, P = 0.026). Absolute LV-GLS ≤ 10.5% was an independent predictor for each secondary outcome (P < 0.05).

CONCLUSIONS

LV-GLS was an independent predictor of a composite of cardiovascular death, including SCD/SCD-equivalent events, in patients with HCM and an LVEF of 50-60%. Therefore, LV-GLS can help in risk stratification in these patients.

Multimodality Imaging in Patients with Hypertrophic Cardiomyopathy and Atrial Fibrillation

Ventricular hypertrophy is associated with diastolic dysfunction, resulting in increased left atrial (LA) pressure, enlargement, fibrosis, and decreased LA function. Hypertrophic cardiomyopathy (HCM) is characterized by myocyte disarray, myocardial fibrosis, and hypertrophy. Notably, a thickened and noncompliant LV results in the impairment of diastolic function. These conditions promote LA remodeling and enlargement, which contribute to developing and maintaining atrial fibrillation (AF). AF is an atrial arrhythmia that occurs frequently in HCM, and evaluating the morphology and physiology of the atrium and ventricle is important for treatment and prognosis determination in HCM patients with AF. In addition, it provides a clue that can predict the possibility of new AF, even in patients not previously diagnosed with AF. Cardiac magnetic resonance (CMR), which can overcome the limitations of transthoracic echocardiography (TTE), has been widely used traditionally and even enables tissue characterization; moreover, it has emerged as an essential imaging modality for patients with HCM. Here, we review the role of multimodal imaging in patients with HCM and AF.

The predictive value of cardiac MRI strain parameters in hypertrophic cardiomyopathy patients with preserved left ventricular ejection fraction and a low fibrosis burden: a retrospective cohort study

Background

Prompt interventions prevent adverse events (AE) in hypertrophic cardiomyopathy (HCM). We evaluated the pattern and the predictive role of feature tracking (FT)-cardiac magnetic resonance (CMR) imaging parameters in an HCM population with a normal left ventricular ejection fraction (LVEF) and a low fibrosis burden.

Methods

The CMR and clinical data of 170 patients, consisting of 142 HCM (45 ± 15.7 years, 62.7% male) and 28 healthy (42.2 ± 11.26 years, 50% male) subjects, who were enrolled from 2015 to 2020, were evaluated. HCM patients had a normal LVEF with a late gadolinium enhancement (LGE) percentage below 15%. Between-group differences were described, and the potent predictors of AE were determined. A P-value below 0.05 was considered significant.

Results

LV global longitudinal, circumferential, and radial strains (GLS, GCS, and GRS, respectively) and the LV myocardial mass index (MMI) were different between the healthy and HCM cases (all Ps < 0.05). Strains were significantly impaired in the HCM patients with a normal MMI. A progressive decrease in LVGLS and a distinct fall in LVGCS were noted with a rise in MMI. AE were predicted by LVGLS, LVGCS, and the LGE percentage, and LVGCS was the single robust predictor (HR, 1.144; 95% CI, 1.080-1.212; P = 0.001). An LVGCS below 16.2% predicted AE with 77% specificity and 58% sensitivity.

Conclusions

LV strains were impaired in HCM patients with a normal EF and a low fibrosis burden, even in the presence of a normal MMI. CMR parameters, especially FT-CMR values, predicted AE in our HCM patients.

Sudden Death Risk Assessment in Hypertrophic Cardiomyopathy Across the Lifespan: Reconciling the American and European Approaches

Hypertrophic cardiomyopathy (HCM) is the most prevalent inherited cardiac disease. Since the modern description of HCM more than seven decades ago, great focus has been placed on preventing its most catastrophic complication: sudden cardiac death (SCD). Implantable cardioverter-defibrillators (ICD) have been recognized to provide effective prophylactic therapy. Over the years, two leading societies, the European Society of Cardiology (ESC) and the American Heart Association/American College of Cardiology (AHA/ACC), have proposed risk stratification models to assess SCD in adults. European guidelines rely on a risk calculator, the HCM Risk-SCD, while American guidelines propose a stand-alone risk factor approach. Recently, risk prediction models were also developed in the pediatric population. This article reviews the latest recommendations on the risk stratification of SCD in HCM and summarises current indications for ICD use.

Predictive Factors for Decreasing Left Ventricular Ejection Fraction and Progression to the Dilated Phase of Hypertrophic Cardiomyopathy

Patients with hypertrophic cardiomyopathy (HCM) may progress to the dilated phase (DHCM). This study aimed to identify the predictive factors for DHCM progression, including left ventricular (LV) ejection fraction (LVEF < 50%) or decreased LV contraction (LVEF < 60%). The study included 291 patients enrolled in our hospital's HCM registry who were grouped based on their poststudy LVEF (LVEF of ≥60%, 50-59%, and <50%). Predictive factors of an LVEF of <50% or <60% were determined. Further, the effects of percutaneous transluminal septal myocardial ablation (PTSMA) on long-term systolic LV function and DHCM development were investigated. LVEF was ≥60%, 50-59%, and <50% in 239, 33, and 19 patients, respectively, during the follow-up period (mean: 64.9 months). Multivariate analyses indicated baseline atrial fibrillation (AF), nonsustained ventricular tachycardia (NSVT), and left ventricular diameter at end-systole (LVDs) as significant predictors of DHCM. Using a scoring method based on AF, NSVT, and LVDs, patients with 2 and 3 points had a significantly higher risk of developing DHCM. PTSMA in 78 HCM patients demonstrated no significant effect on long-term LVEF changes or DHCM development. We concluded that AF, NSVT, and LVDs are significant predictors of DHCM development. However, a validation study with a larger population is required.

Left Ventricular Systolic Dysfunction in Patients Diagnosed With Hypertrophic Cardiomyopathy During Childhood: Insights From the SHaRe Registry

BACKGROUND

The development of left ventricular systolic dysfunction (LVSD) in hypertrophic cardiomyopathy (HCM) is rare but serious and associated with poor outcomes in adults. Little is known about the prevalence, predictors, and prognosis of LVSD in patients diagnosed with HCM as children.

METHODS

Data from patients with HCM in the international, multicenter SHaRe (Sarcomeric Human Cardiomyopathy Registry) were analyzed. LVSD was defined as left ventricular ejection fraction <50% on echocardiographic reports. Prognosis was assessed by a composite of death, cardiac transplantation, and left ventricular assist device implantation. Predictors of developing incident LVSD and subsequent prognosis with LVSD were assessed using Cox proportional hazards models.

RESULTS

We studied 1010 patients diagnosed with HCM during childhood (<18 years of age) and compared them with 6741 patients with HCM diagnosed as adults. In the pediatric HCM cohort, median age at HCM diagnosis was 12.7 years (interquartile range, 8.0-15.3), and 393 (36%) patients were female. At initial SHaRe site evaluation, 56 (5.5%) patients with childhood-diagnosed HCM had prevalent LVSD, and 92 (9.1%) developed incident LVSD during a median follow-up of 5.5 years. Overall LVSD prevalence was 14.7% compared with 8.7% in patients with adult-diagnosed HCM. Median age at incident LVSD was 32.6 years (interquartile range, 21.3-41.6) for the pediatric cohort and 57.2 years (interquartile range, 47.3-66.5) for the adult cohort. Predictors of developing incident LVSD in childhood-diagnosed HCM included age <12 years at HCM diagnosis (hazard ratio [HR], 1.72 [CI, 1.13-2.62), male sex (HR, 3.1 [CI, 1.88-5.2), carrying a pathogenic sarcomere variant (HR, 2.19 [CI, 1.08-4.4]), previous septal reduction therapy (HR, 2.34 [CI, 1.42-3.9]), and lower initial left ventricular ejection fraction (HR, 1.53 [CI, 1.38-1.69] per 5% decrease). Forty percent of patients with LVSD and HCM diagnosed during childhood met the composite outcome, with higher rates in female participants (HR, 2.60 [CI, 1.41-4.78]) and patients with a left ventricular ejection fraction <35% (HR, 3.76 [2.16-6.52]).

CONCLUSIONS

Patients with childhood-diagnosed HCM have a significantly higher lifetime risk of developing LVSD, and LVSD emerges earlier than for patients with adult-diagnosed HCM. Regardless of age at diagnosis with HCM or LVSD, the prognosis with LVSD is poor, warranting careful surveillance for LVSD, especially as children with HCM transition to adult care.

Long-Term Prevalence of Systolic Dysfunction in MYBPC3 Versus MYH7-Related Hypertrophic Cardiomyopathy

BACKGROUND

The 2 sarcomere genes most commonly associated with hypertrophic cardiomyopathy (HCM), MYBPC3 (myosin-binding protein C3) and MYH7 (β-myosin heavy chain), are indistinguishable at presentation, and genotype-phenotype correlations have been elusive. Based on molecular and pathophysiological differences, however, it is plausible to hypothesize a different behavior in myocardial performance, impacting lifetime changes in left ventricular (LV) function.

METHODS

We reviewed the initial and final echocardiograms of 402 consecutive HCM patients with pathogenic or likely pathogenic MYBPC3 (n=251) or MYH7 (n=151) mutations, followed over 9±8 years.

RESULTS

At presentation, MYBPC3 patients were less frequently obstructive (15% versus 26%; P=0.005) and had lower LV ejection fraction compared with MYH7 (66±8% versus 68±8%, respectively; P=0.03). Both HCM patients harboring MYBPC3 and MYH7 mutations exhibited a small but significant decline in LV systolic function during follow-up; however, new onset of severe LV systolic dysfunction (LV ejection fraction, <50%) was greater among MYBPC3 patients (15% versus 5% among MYH7; P=0.013). Prevalence of grade II/III diastolic dysfunction at final evaluation was comparable between MYBPC3 and MYH7 patients (P=0.509). In a Cox multivariable analysis, MYBPC3-positive status (hazard ratio, 2.53 [95% CI, 1.09-5.82]; P=0.029), age (hazard ratio, 1.03 [95% CI, 1.00-1.06]; P=0.027), and atrial fibrillation (hazard ratio, 2.39 [95% CI, 1.14-5.05]; P=0.020) were independent predictors of severe systolic dysfunction. No statistically significant differences occurred with regard to incidence of atrial fibrillation, heart failure, appropriate implanted cardioverter defibrillator shock, or cardiovascular death.

CONCLUSIONS

MYBPC3-related HCM showed increased long-term prevalence of systolic dysfunction compared with MYH7, in spite of similar outcome. Such observations suggest different pathophysiology of clinical progression in the 2 subsets and may prove relevant for understanding of genotype-phenotype correlations in HCM.

Imaging cardiac hypertrophy in hypertrophic cardiomyopathy and its differential diagnosis

PURPOSE OF REVIEW

The aim of this study was to review imaging of myocardial hypertrophy in hypertrophic cardiomyopathy (HCM) and its phenocopies. The introduction of cardiac myosin inhibitors in HCM has emphasized the need for careful evaluation of the underlying cause of myocardial hypertrophy.

RECENT FINDINGS

Advances in imaging of myocardial hypertrophy have focused on improving precision, diagnosis, and predicting prognosis. From improved assessment of myocardial mass and function, to assessing myocardial fibrosis without the use of gadolinium, imaging continues to be the primary tool in understanding myocardial hypertrophy and its downstream effects. Advances in differentiating athlete's heart from HCM are noted, and the increasing rate of diagnosis in cardiac amyloidosis using noninvasive approaches is especially highlighted due to the implications on treatment approach. Finally, recent data on Fabry disease are shared as well as differentiating other phenocopies from HCM.

SUMMARY

Imaging hypertrophy in HCM and ruling out other phenocopies is central to the care of patients with HCM. This space will continue to rapidly evolve, as disease-modifying therapies are under investigation and being advanced to the clinic.

Cardiac Myosin Inhibitors for Managing Obstructive Hypertrophic Cardiomyopathy: JACC: Heart Failure State-of-the-Art Review

Hypertrophic cardiomyopathy (HCM) is frequently caused by pathogenic variants in genes encoding sarcomere proteins and is characterized by left ventricular (LV) hypertrophy, hypercontractility, and-in many cases-left ventricular outflow tract (LVOT) obstruction. Despite standard management, obstructive HCM (oHCM) can still cause substantial morbidity, highlighting the critical need for more effective disease-specific therapeutic approaches. Over the past decade, improved understanding of the molecular pathobiology of HCM has culminated in development of cardiac myosin inhibitors (CMIs), a novel drug class that in recent randomized clinical trials has been shown to decrease LVOT obstruction, improve exercise capacity, and ameliorate symptom burden in patients with oHCM. Although promising, areas of uncertainty remain, including the long-term safety and efficacy of CMIs and whether they have the potential to modify progression of disease. Herein, we review key milestones in the clinical development of CMIs, contextualize CMIs with established oHCM therapies, and discuss future challenges and opportunities for the use of CMIs across the HCM spectrum.

A novel αB-crystallin R123W variant drives hypertrophic cardiomyopathy by promoting maladaptive calcium-dependent signal transduction

Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiovascular disorder affecting 1 in 500 people in the general population. Characterized by asymmetric left ventricular hypertrophy, cardiomyocyte disarray and cardiac fibrosis, HCM is a highly complex disease with heterogenous clinical presentation, onset and complication. While mutations in sarcomere genes can account for a substantial proportion of familial cases of HCM, 40%-50% of HCM patients do not carry such sarcomere variants and the causal mutations for their diseases remain elusive. Recently, we identified a novel variant of the alpha-crystallin B chain (CRYABR123W) in a pair of monozygotic twins who developed concordant HCM phenotypes that manifested over a nearly identical time course. Yet, how CRYABR123W promotes the HCM phenotype remains unclear. Here, we generated mice carrying the CryabR123W knock-in allele and demonstrated that hearts from these animals exhibit increased maximal elastance at young age but reduced diastolic function with aging. Upon transverse aortic constriction, mice carrying the CryabR123W allele developed pathogenic left ventricular hypertrophy with substantial cardiac fibrosis and progressively decreased ejection fraction. Crossing of mice with a Mybpc3 frame-shift model of HCM did not potentiate pathological hypertrophy in compound heterozygotes, indicating that the pathological mechanisms in the CryabR123W model are independent of the sarcomere. In contrast to another well-characterized CRYAB variant (R120G) which induced Desmin aggregation, no evidence of protein aggregation was observed in hearts expressing CRYABR123W despite its potent effect on driving cellular hypertrophy. Mechanistically, we uncovered an unexpected protein-protein interaction between CRYAB and calcineurin. Whereas CRYAB suppresses maladaptive calcium signaling in response to pressure-overload, the R123W mutation abolished this effect and instead drove pathologic NFAT activation. Thus, our data establish the CryabR123W allele as a novel genetic model of HCM and unveiled additional sarcomere-independent mechanisms of cardiac pathological hypertrophy.

Recent Advances in Translational Research for Heart Failure in Japan

Despite decades of intensive research and therapeutic development, heart failure remains a leading cause of death worldwide. However, recent advances in several basic and translational research fields, such as genomic analysis and single-cell analysis, have increased the possibility of developing novel diagnostic approaches to heart failure. Most cardiovascular diseases that predispose individuals to heart failure are caused by genetic and environmental factors. It follows that genomic analysis can contribute to the diagnosis and prognostic stratification of patients with heart failure. In addition, single-cell analysis has shown great potential for unveiling the pathogenesis and/or pathophysiology and for discovering novel therapeutic targets for heart failure. Here, we summarize the recent advances in translational research on heart failure in Japan, based mainly on our studies.

Stage-specific therapy for hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most common inherited myocardial disease and is defined by otherwise unexplained left ventricular hypertrophy. The main complications include heart failure and arrhythmias such as atrial fibrillation and ventricular arrhythmias. Current treatment rests on septal reduction therapies, prevention of sudden cardiac death through implantable cardioverter defibrillator, and use of drugs such as beta-blockers, calcium antagonists, or amiodarone. In the last years, new pharmacological agents specifically targeting the pathophysiology of the disease have been developed with encouraging results in terms of functional capacity and symptoms improvement from clinical trials. In this review, we summarize the possible treatment approaches for each phase of the natural history of the disease: pre-phenotype expression, classic phenotype, adverse remodelling, and overt dysfunction.

Computational modeling of electromechanical coupling in human cardiomyocyte applied to study hypertrophic cardiomyopathy and its drug response

BACKGROUND AND OBJECTIVE

Knowledge of electromechanical coupling in cardiomyocyte and how it is influenced by various pathophysiological factors is fundamental to understanding the pathogenesis of myocardial disease and its response to medication, which is however hard to be thoroughly addressed by clinical/experimental studies due to technical limitations. At this point, computational modeling offers an alternative approach. The main objective of the study was to develop a computational model capable of simulating the process of electromechanical coupling and quantifying the roles of various factors in play in the human left ventricular cardiomyocyte.

METHODS

A new electrophysiological model was firstly built by combining several existing electrophysiological models and incorporating the mechanism of electrophysiological homeostasis, which was subsequently coupled to models representing the cross-bridge dynamics and active force generation during excitation-contraction coupling and the passive mechanical properties of cardiomyocyte to yield an integrative electromechanical model. Model parameters were calibrated or optimized based on a large amount of experimental data. The resulting model was applied to delineate the characteristics of electromechanical coupling and explore underlying determinant factors in hypertrophic cardiomyopathy (HCM) cardiomyocyte, as well as quantify their changes in response to different medications.

RESULTS

Model predictions captured the major electromechanical characteristics of cardiomyocyte under both normal physiological and HCM conditions. In comparison with normal cardiomyocyte, HCM cardiomyocyte suffered from systemic changes in both electrophysiological and mechanical variables. Numerical simulations of drug response revealed that Mavacamten and Metoprolol could both reduce the active contractility and alleviate calcium overload but had marked differential influences on many other electromechanical variables, which theoretically explained why the two drugs have differential therapeutic effects. In addition, our numerical experiments demonstrated the important role of compensatory ion transport in maintaining electrophysiological homeostasis and regulating cytoplasmic volume.

CONCLUSIONS

A sophisticated computational model has the advantage of providing quantitative and integrative insights for understanding the pathogenesis and drug responses of HCM or other myocardial diseases at the level of cardiomyocyte, and hence may contribute as a useful complement to clinical/experimental studies. The model may also be coupled to tissue- or organ-level models to strengthen the physiological implications of macro-scale numerical simulations.

Disease modeling of desmosome-related cardiomyopathy using induced pluripotent stem cell-derived cardiomyocytes

Cardiomyopathy is a pathological condition characterized by cardiac pump failure due to myocardial dysfunction and the major cause of advanced heart failure requiring heart transplantation. Although optimized medical therapies have been developed for heart failure during the last few decades, some patients with cardiomyopathy exhibit advanced heart failure and are refractory to medical therapies. Desmosome, which is a dynamic cell-to-cell junctional component, maintains the structural integrity of heart tissues. Genetic mutations in desmosomal genes cause arrhythmogenic cardiomyopathy (AC), a rare inheritable disease, and predispose patients to sudden cardiac death and heart failure. Recent advances in sequencing technologies have elucidated the genetic basis of cardiomyopathies and revealed that desmosome-related cardiomyopathy is concealed in broad cardiomyopathies. Among desmosomal genes, mutations in PKP2 (which encodes PKP2) are most frequently identified in patients with AC. PKP2 deficiency causes various pathological cardiac phenotypes. Human cardiomyocytes differentiated from patient-derived induced pluripotent stem cells (iPSCs) in combination with genome editing, which allows the precise arrangement of the targeted genome, are powerful experimental tools for studying disease. This review summarizes the current issues associated with practical medicine for advanced heart failure and the recent advances in disease modeling using iPSC-derived cardiomyocytes targeting desmosome-related cardiomyopathy caused by PKP2 deficiency.

Cardiomyocyte Apoptosis Is Associated with Contractile Dysfunction in Stem Cell Model of MYH7 E848G Hypertrophic Cardiomyopathy

Missense mutations in myosin heavy chain 7 (MYH7) are a common cause of hypertrophic cardiomyopathy (HCM), but the molecular mechanisms underlying MYH7-based HCM remain unclear. In this work, we generated cardiomyocytes derived from isogenic human induced pluripotent stem cells to model the heterozygous pathogenic MYH7 missense variant, E848G, which is associated with left ventricular hypertrophy and adult-onset systolic dysfunction. MYH7E848G/+ increased cardiomyocyte size and reduced the maximum twitch forces of engineered heart tissue, consistent with the systolic dysfunction in MYH7E848G/+ HCM patients. Interestingly, MYH7E848G/+ cardiomyocytes more frequently underwent apoptosis that was associated with increased p53 activity relative to controls. However, genetic ablation of TP53 did not rescue cardiomyocyte survival or restore engineered heart tissue twitch force, indicating MYH7E848G/+ cardiomyocyte apoptosis and contractile dysfunction are p53-independent. Overall, our findings suggest that cardiomyocyte apoptosis is associated with the MYH7E848G/+ HCM phenotype in vitro and that future efforts to target p53-independent cell death pathways may be beneficial for the treatment of HCM patients with systolic dysfunction.

Hypertrophic, Dilated, and Arrhythmogenic Cardiomyopathy: Where Are We?

Cardiomyopathies are a heterogeneous group of structural, mechanical, and electrical heart muscle disorders which often correlate with life-threatening arrhythmias and progressive heart failure accounting for significant cardiovascular morbidity and mortality. Currently, cardiomyopathies still represent a leading reason for heart transplantation worldwide. The last years have brought remarkable advances in the field of cardiomyopathies especially in terms of understanding the molecular basis as well as the diagnostic evaluation and management. Although most cardiomyopathy treatments had long focused on symptom management, much of the current research efforts aim to identify and act on the disease-driving mechanisms. Regarding risk assessment and primary prevention of sudden cardiac death, additional data are still pending in order to pave the way for a more refined and early patient selection for defibrillator implantation. This review summarizes the current knowledge of hypertrophic, dilated and arrhythmogenic cardiomyopathy with a particular emphasis on their pathophysiology, clinical features, and diagnostic approach. Furthermore, the relevant ongoing studies investigating novel management approaches and main gaps in knowledge are highlighted.

Cardiac Resynchronization Therapy and Hypertrophic Cardiomyopathy: A Comprehensive Review

Hypertrophic cardiomyopathy (HCM) is an inherited primary myocardial disease characterized by asymmetrical/symmetrical left ventricle (LV) hypertrophy, with or without LV outflow tract (LVOT) dynamic obstruction, and poor prognosis. Cardiac resynchronization therapy (CRT) has emerged as a minimally invasive tool for patients with heart failure (HF) with decreased LV ejection fraction (LVEF) and prolonged QRS duration of over 120 ms with or without left bundle branch block (LBBB). Several HCM patients are at risk of developing LBBB because of disease progression or secondary to septal myomectomy, while others might develop HF with decreased LVEF, alleged end-stage/dilated HCM, especially those with thin myofilament mutations. Several studies have shown that patients with myectomy-induced LBBB might benefit from left bundle branch pacing or CRT to relieve symptoms, improve exercise capacity, and increase LVEF. Otherwise, patients with end-stage/dilated HCM and prolonged QRS interval could gain from CRT in terms of NYHA class improvement, LV systolic performance increase and, to some degree, LV reverse remodeling. Moreover, several electrical and imaging parameters might aid proper selection and stratification of HCM patients to benefit from CRT. Nonetheless, current available data are scarce and further studies are still required to accurately clarify the view. This review reassesses the importance of CRT in patients with HCM based on current research by contrasting and contextualizing data from various published studies.

Cardiomyocyte apoptosis contributes to contractile dysfunction in stem cell model of MYH7 E848G hypertrophic cardiomyopathy

Missense mutations in myosin heavy chain 7 ( MYH7 ) are a common cause of hyper-trophic cardiomyopathy (HCM), but the molecular mechanisms underlying MYH7 -based HCM remain unclear. In this work, we generated cardiomyocytes derived from isogenic human induced pluripotent stem cells to model the heterozygous pathogenic MYH7 missense variant, E848G, which is associated with left ventricular hypertrophy and adultonset systolic dysfunction. MYH7 E848G/+ increased cardiomyocyte size and reduced the maximum twitch forces of engineered heart tissue, consistent with the systolic dysfunction in MYH7 E848G HCM patients. Interestingly, MYH7 E848G/+ cardiomyocytes more frequently underwent apoptosis that was associated with increased p53 activity relative to controls. However, genetic ablation of TP53 did not rescue cardiomyocyte survival or restore engineered heart tissue twitch force, indicating MYH7 E848G/+ cardiomyocyte apoptosis and contractile dysfunction are p53-independent. Overall, our findings suggest that cardiomyocyte apoptosis plays an important role in the MYH7 E848G/+ HCM phenotype in vitro and that future efforts to target p53-independent cell death pathways may be beneficial for the treatment of HCM patients with systolic dysfunction.

Precision and genomic medicine for dilated and hypertrophic cardiomyopathy

Cardiomyopathy develops through an interaction of genetic and environmental factors. The clinical manifestations of both dilated cardiomyopathy and hypertrophic cardiomyopathy are diverse, but genetic testing defines the causative genes in about half of cases and can predict clinical prognosis. It has become clear that cardiomyopathy is caused not only by single rare variants but also by combinations of multiple common variants, and genome-wide genetic research is important for accurate disease risk assessment. Single-cell analysis research aimed at understanding the pathophysiology of cardiomyopathy is progressing rapidly, and it is expected that genomic analysis and single-cell molecular profiling will be combined to contribute to more detailed stratification of cardiomyopathy.

Differences in phenotypes, symptoms, and survival in patients with cardiomyopathy-a prospective observational study from the Sahlgrenska CardioMyoPathy Centre

Introduction

Cardiomyopathy is the fourth most common cause of heart failure. The spectrum of cardiomyopathies may be impacted by changes in environmental factors and the prognosis may be influenced by modern treatment. The aim of this study is to create a prospective clinical cohort, the Sahlgrenska CardioMyoPathy Centre (SCMPC) study, and compare patients with cardiomyopathies in terms of phenotype, symptoms, and survival.

Methods

The SCMPC study was founded in 2018 by including patients with all types of suspected cardiomyopathies. This study included data on patient characteristics, background, family history, symptoms, diagnostic examinations, and treatment including heart transplantation and mechanical circulatory support (MCS). Patients were categorized by the type of cardiomyopathy on the basis of the diagnostic criteria laid down by the European Society of Cardiology (ESC) working group on myocardial and pericardial diseases. The primary outcomes were death, heart transplantation, or MCS, analyzed by Kaplan-Meier and Cox proportional regression, adjusted for age, gender, LVEF and QRS width on ECG in milliseconds.

Results

In all, 461 patients and 73.1% men with a mean age of 53.6 ± 16 years were included in the study. The most common diagnosis was dilated cardiomyopathy (DCM), followed by cardiac sarcoidosis and myocarditis. Dyspnea was the most common initial symptom in patients with DCM and amyloidosis, while patients with arrhythmogenic right ventricular cardiomyopathy (ARVC) presented with ventricular arrythmias. Patients with ARVC, left-ventricular non-compaction cardiomyopathy (LVNC), hypertrophic cardiomyopathy (HCM), and DCM had the longest time from the debut of symptoms until inclusion in the study. Overall, 86% of the patients survived without heart transplantation or MCS after 2.5 years. The primary outcome differed among the cardiomyopathies, where the worst prognosis was reported for ARVC, LVNC, and cardiac amyloidosis. In a Cox regression analysis, it was found that ARVC and LVNC were independently associated with an increased risk of death, heart transplantation, or MCS compared with DCM. Further, female gender, a lower LVEF, and a wider QRS width were associated with an increased risk of the primary outcome.

Conclusions

The SCMPC database offers a unique opportunity to explore the spectrum of cardiomyopathies over time. There is a large difference in characteristics and symptoms at debut and a remarkable difference in outcome, where the worst prognosis was reported for ARVC, LVNC, and cardiac amyloidosis.

Role and Clinical Importance of Progressive Changes in Echocardiographic Parameters in Predicting Outcomes in Patients With Hypertrophic Cardiomyopathy

BACKGROUND

The prognostic utility of follow-up transthoracic echocardiography (FU-TTE) in patients with hypertrophic cardiomyopathy (HCM) is unclear, specifically in terms of whether changes in echocardiographic parameters in routine FU-TTE parameters are associated with cardiovascular outcomes.

METHODS

From 2010 to 2017, 162 patients with HCM were retrospectively enrolled in this study. Using echocardiography, HCM was diagnosed based on morphological criteria. Patients with other diseases that cause cardiac hypertrophy were excluded. TTE parameters at baseline and FU were analyzed. FU-TTE was designated as the last recorded value in patients who did not develop any cardiovascular event or the latest exam before event development. Clinical outcomes were acute heart failure, cardiac death, arrhythmia, ischemic stroke, and cardiogenic syncope.

RESULTS

Median interval between the baseline TTE and FU-TTE was 3.3 years. Median clinical FU duration was 4.7 years. Septal trans-mitral velocity/mitral annular tissue Doppler velocity (E/e'), tricuspid regurgitation velocity, left ventricular ejection fraction (LVEF), and left atrial volume index (LAVI) at baseline were recorded. LVEF, LAVI, and E/e' values were associated with poor outcomes. However, no delta values predicted HCM-related cardiovascular outcomes. Logistic regression models incorporating changes in TTE parameters had no significant findings. Baseline LAVI was the best predictor of a poor prognosis. In survival analysis, an already enlarged or increased size LAVI was associated with poorer clinical outcomes.

CONCLUSIONS

Changes in echocardiographic parameters extracted from TTE did not assist in predicting clinical outcomes. Cross-sectionally evaluated TTE parameters were superior to changes in TTE parameters between baseline and FU at predicting cardiovascular events.

Left Ventricular Apical Aneurysm in Fabry Disease: Implications for Clinical Significance and Risk Stratification

Background A previously underrecognized phenotype of left ventricular apical aneurysm (LVAA) has been increasingly identified in Fabry disease. This study explored LVAA's clinical prevalence and its prognostic implications over a long-term follow-up. Methods and Results We retrospectively analyzed 268 consecutive patients with Fabry disease at a tertiary medical center. Patients with increased left ventricular mass index were recognized as having left ventricular hypertrophy (LVH). LVAA was identified using either echocardiography or cardiovascular magnetic resonance imaging. Two patients with ischemic LVAA were excluded. The primary end point was a composite of cardiovascular events, including heart failure hospitalization, sustained ventricular tachycardia, ischemic stroke, and all-cause mortality. Of 266 enrolled patients, 105 (39.5%) had LVH (age 58.5±11.9 years, 48.6% men), and 11 (10.5%) had LVAA. Over 49.3±34.8 months of follow-up, 25 patients with LVH experienced composite events, including 9 heart failure hospitalizations, 4 sustained ventricular tachycardia, 6 ischemic strokes, and 15 mortalities. In patients with LVH, those with LVAA had a significantly higher risk of composite events and lower event-free survival than those without LVAA (8 [72.7%] versus 17 [18.1%], log-rank P<0.001). LVAA was independently associated with an increased risk of composite events (hazard ratio, 3.59 [95% CI, 1.30-9.91]; P=0.01) after adjusting for age, sex, advanced heart failure, renal function, dyslipidemia, atrial fibrillation, left ventricular ejection fraction, left ventricular diastolic function, and left ventricular mass index. Conclusions LVAA is present in approximately 10% of patients with Fabry disease and LVH. It is associated with an increased risk of adverse cardiovascular events and may necessitate aggressive treatment.

Prognosis of patients with hypertrophic cardiomyopathy and low-normal left ventricular ejection fraction

OBJECTIVE

To investigate whether low-normal left ventricular ejection fraction (LVEF) is associated with adverse outcomes in hypertrophic cardiomyopathy (HCM) and evaluate the incremental value of predictive power of LVEF in the conventional HCM sudden cardiac death (SCD)-risk model.

METHODS

This retrospective study included 1858 patients with HCM from two tertiary hospitals between 2008 and 2019. We classified LVEF into three categories: preserved (≥60%), low normal (50%-60%) and reduced (<50%); there were 1399, 415, and 44 patients with preserved, low-normal, and reduced LVEF, respectively. The primary outcome was a composite of SCD, ventricular tachycardia/fibrillation and appropriate implantable cardioverter-defibrillator shocks. Secondary outcomes were hospitalisation for heart failure (HHF), cardiovascular death and all-cause death.

RESULTS

During the median follow-up of 4.09 years, the primary outcomes occurred in 1.9%. HHF, cardiovascular death, and all-cause death occurred in 3.3%, 1.9%, and 5.3%, respectively. Reduced LVEF was an independent predictor of SCD/equivalent events (adjusted HR (aHR) 5.214, 95% CI 1.574 to 17.274, p=0.007), adding predictive value to the HCM risk-SCD model (net reclassification improvement 0.625). Compared with patients with HCM with preserved LVEF, those with low-normal and reduced LVEF had a higher risk of HHF (LVEF 50%-60%, aHR 2.457, 95% CI 1.423 to 4.241, p=0.001; LVEF <50%, aHR 7.937, 95% CI 3.315 to 19.002, p<0.001) and cardiovascular death (LVEF 50%-60%, aHR 2.641, 95% CI 1.314 to 5.309, p=0.006; LVEF <50%, aHR 5.405, 95% CI 1.530 to 19.092, p=0.009), whereas there was no significant association with all-cause death.

CONCLUSIONS

Low-normal LVEF was an independent predictor of HHF and cardiovascular death in patients with HCM.

Single coronary ostium with obstructive hypertrophic cardiomyopathy treated using the Morrow procedure: a case report

BACKGROUND

Hypertrophic cardiomyopathy is a commonly inherited heart disease. In addition, single coronary artery (SCA) is a rare congenital anomaly of the coronary arteries. And SCA concomitant with severe hypertrophic obstructive cardiomyopathy (HOCM) has seldom been reported in the literature. However, such cases have not been reported to be treated with the Morrow procedure.

CASE PRESENTATION

Herein, we presented a case of a 64-year-old female diagnosed with a single left coronary artery with severe HOCM. The HOCM was treated with the Morrow procedure. The patient was discharged on the seventh postoperative day and was asymptomatic during the follow-up.

CONCLUSION

To our knowledge, this is the first study reporting a single left coronary artery with severe HOCM treated with the Morrow procedure. In addition, myocardial protection by cardioplegia antegrade perfusion was safe for the patient with SCA and HOCM.