T1 measurements identify extracellular volume expansion in hypertrophic cardiomyopathy sarcomere mutation carriers with and without left ventricular hypertrophy

A Multidimensional Approach to Understanding Genetic Diversity, Risk Stratification, and Personalized Interventions in Pediatric Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) in children presents unique challenges distinct from adult manifestations, with potentially devastating consequences, including sudden cardiac death. This comprehensive review synthesizes current evidence on the pathophysiology, clinical presentation, and management of pediatric HCM, highlighting critical differences from adult populations. While affecting approximately 1 in 500 individuals, pediatric HCM demonstrates more significant etiological heterogeneity, with up to 35% of cases stemming from non-sarcomeric causes, including RASopathies, metabolic disorders, and syndromic conditions. This etiological diversity contributes to variable disease trajectories and treatment responses, creating a significant research gap in pediatric-specific management protocols. Current pharmacological approaches primarily employ beta-blockers as first-line therapy, with calcium channel blockers serving as alternatives for intolerant patients. However, these conventional medications manage symptoms without addressing underlying pathophysiology or preventing disease progression. Emerging investigational therapies, including angiotensin receptor blockers and myosin inhibitors like mavacamten, show promise in preliminary studies but lack robust pediatric-specific evidence. Surgical interventions, including septal myectomy and the modified Konno procedure, demonstrate efficacy in medication-refractory cases but carry higher complication risks in younger patients. The critical research gap lies in developing targeted therapeutic approaches for pediatric-specific HCM subtypes, particularly those associated with syndromic and metabolic disorders. Additionally, risk stratification models for sudden cardiac death prevention remain inadequately validated in pediatric populations. This review identifies the urgent need for pediatric-focused clinical trials investigating both conventional and novel therapies alongside the development of age-appropriate risk assessment tools to guide personalized management strategies for this vulnerable population.

The Role of Cardiac Magnetic Resonance Imaging in the Management of Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most common genetic cardiomyopathy, caused by either sarcomere protein or other gene mutations. It is a complex and highly heterogeneous disorder, with phenotypes ranging from asymptomatic to severe disease, characterized by asymmetric left ventricular (LV) hypertrophy unexplained by loading conditions, which is also associated with myocardial fiber disarray, and preserved or increased ejection fraction without LV dilation. Comprehensive personal and family history, physical examination, and ECG testing raise suspicion of HCM, and echocardiogram represents the first-line imaging modality for confirming a diagnosis. Moreover, contrast-enhanced cardiac magnetic resonance (CMR) imaging has increasingly emerged as a fundamental diagnostic and prognostic tool in HCM management. This article reviews the role of CMR in HCM identification and differentiation from phenotypic mimics, characterization of HCM phenotypes, monitoring of disease progression, evaluation of pre- and post-septal reduction treatments, and selection of candidates for implantable cardioverter-defibrillator. By providing information on cardiac morphology and function and tissue characterization, CMR is particularly helpful in the quantification of myocardial wall thickness, the detection of hypertrophy in areas blind to echocardiogram, subtle morphologic features in the absence of LV hypertrophy, myocardial fibrosis, and apical aneurysm, the evaluation of LV outflow tract obstruction, and the assessment of LV function in end-stage dilated HCM.

Proteomic Analysis of Valsartan for Attenuating Disease Evolution in Early Sarcomeric Hypertrophic Cardiomyopathy (VANISH) Clinical Trial

BACKGROUND

In hypertrophic cardiomyopathy (HCM), the mechanisms through which pathogenic sarcomere variants (G+) lead to left ventricular hypertrophy (LVH) are not understood.

METHODS

VANISH (Valsartan for Attenuating Disease Evolution in Early Sarcomeric Hypertrophic Cardiomyopathy) was a multicenter, double-blind, placebo-controlled randomized trial testing valsartan's ability to attenuate phenotypic progression in early sarcomeric (G+LVH+) and subclinical HCM (G+LVH-). The outcome was a composite Z score reflecting cardiac remodeling from baseline to year 2 (end of study). Baseline and year 2 blood samples were used to quantify 276 proteins using a proximity extension assay (Olink, Sweden). We explored relative differences in protein abundance between early and subclinical HCM at baseline. In addition, we compared proteomic changes between baseline and year 2 in subclinical HCM participants who experienced phenotypic conversion to early HCM (converters) versus nonconverters; early HCM participants receiving valsartan versus placebo; and in association with changes in Z score. Comparisons were made using t test/Mann-Whitney U test, linear mixed models, and generalized linear models, correcting for multiple testing.

RESULTS

Circulating proteins were analyzed in 192 participants (32 subclinical and 160 early HCM [81 allocated to valsartan]). NT-proBNP (N-terminal pro-B-type natriuretic peptide) differentiated early from subclinical HCM and tracked with phenotypic progression in early HCM (1-unit worsening in Z score associated with a 27% increase in NT-proBNP [95% CI, 17-37%]). Some extracellular matrix remodeling proteins showed higher abundance (tissue-type plasminogen activator) in early compared with subclinical HCM or tracked with disease progression (decorin) in early HCM. Growth factors had higher relative abundance in early HCM (fibroblast growth factor-21). While no individual protein was able to distinguish converters from nonconverters, multiprotein the panels lipocalin 2, lectin-like oxidized low-density lipoprotein receptor 1, and either NT-proBNP or interleukin-17 receptor A, could distinguish these groups.

CONCLUSIONS

NT-proBNP was the most robust protein to track progression. Studying pathways involving growth factors and extracellular matrix remodeling may yield additional insights into mechanisms behind disease progression.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT01912534.

The Antifibrotic Effects of Eplerenone in Hypertrophic Cardiomyopathy: A Randomized Clinical Trial

BACKGROUND

Fibrosis plays a central role in hypertrophic cardiomyopathy (HCM), contributing to symptoms via impaired systolic and diastolic function and ventricular arrhythmias.

OBJECTIVES

The aim of this study was to determine if eplerenone has an antifibrotic effect in nonobstructive HCM (resting left ventricular outflow tract gradient <30 mm Hg).

METHODS

This was a randomized, double-blind, placebo-controlled trial of eplerenone in 61 patients with nonobstructive HCM over 12 months. The primary endpoint was native T1 time on cardiac magnetic resonance as an index of diffuse fibrosis. Secondary endpoints included changes in diastolic function.

RESULTS

Thirty patients were randomized to 50 mg eplerenone and 31 to placebo. There was a reduction in native T1 time within the eplerenone group (1,315 ± 134 ms at baseline vs 1,259 ± 92 ms at 12 months; P = 0.041), with no significant change in the placebo group (1,234 ± 28 ms at baseline vs 1,238 ± 70 ms at 12 months; P = 0.854). This represents a 3.7% ± 9% reduction in native T1 with eplerenone compared with a 1.1% ± 9% increase with placebo (P = 0.07). There was no significant change in functional status or markers of diastolic function (such as E/e' ratio or mitral E/A ratio).

CONCLUSIONS

In patients with nonobstructive HCM, there was a reduction in myocardial T1 time with eplerenone, consistent with a reduction in diffuse myocardial fibrosis. Larger and longer trials are needed to confirm this finding and explore whether it translates into improved exercise capacity or a reduction in mortality over time. (Anti-fibrotic role of eplerenone on diffuse myocardial fibrosis and diastolic function in patients with hypertrophic cardiomyopathy; ACTRN12613000065796).

Comparison of GRE versus SSFP-based cardiac T1-mapping in device patients

BackgroundCardiac magnetic resonance (CMR) is challenging in patients implanted with metallic devices, such as pacemakers or defibrillators, given metallic susceptibility artifacts. The technique of T1-mapping investigates interstitial fibrosis. The most used method for myocardial T1-mapping is the modified Look-Locker Inversion recovery sequence (MOLLI) using balanced steady-state free precession (SSFP). However, SSFP is susceptible to off-resonance artifacts, leading to errors. Gradient echo (GRE) sequences are less prone to these artifacts.PurposeTo investigate whether T1-mapping using GRE was comparable to SSFP in this population.Material and MethodsPre/post-contrast T1-mapping was performed on 16 devices utilizing MOLLI with SSFP and GRE strategies at 1.5 T, as well as 10 non-device controls. The difference in mean T1 time by SSFP versus GRE (both pre- and post-contrast for each slice) for device patients was analyzed.ResultsNative T1 for the device cohort was 1053 ± 94 ms for SSFP and 969 ± 83 ms for GRE. GRE T1 measurements were shorter than SSFP measurements (difference over all slices for SSFP vs. GRE pre-/post-contrast were 74 ms and 27 ms). Mean λ for GRE (devices) was 0.520 ± 0.194 (p = 0.30). λ for SSFP (devices) was 0.536 ± 0.124 (P = 0.08). There was no difference in λ between SSFP versus GRE in device patients (P = 0.91). The percentage of segments identified as artifact on T1 maps for device patients was 24% and 45% for GRE and SSFP, respectively.ConclusionCompared to SSFP, T1 values using GRE were consistently shorter, while λ values remained equivalent. There was less visual artifact on GRE images, suggesting advantageous utility over SSFP in patients with cardiac devices.

Use of Advanced Echocardiographic Modalities to Discriminate Preclinical Hypertrophic Cardiomyopathy Mutation Carriers From Non-Carriers

BACKGROUND

It remains challenging to determine which hypertrophic cardiomyopathy (HCM) family members will subsequently develop HCM. Standard 2-dimensional and conventional Doppler echocardiography have been unable to reliably distinguish HCM genotype-positive and phenotype-negative (G+P-) from genotype-negative and phenotype-negative (G-P-) family members. We aimed to determine if advanced echocardiographic modalities can discriminate HCM G+P- from G-P- individuals.

METHODS

Comprehensive echocardiography including speckle tracking evaluation of myocardial deformation and color M-mode were performed in 199 participants aged ≥16 years who had undergone genetic testing from families with a known HCM pathogenic variant: 58 G+P-, 39 G-P-, and 102 overt patients with HCM (genotype-positive and phenotype-positive). The primary analysis compared these measures in all G+P- and G-P- individuals. A secondary analysis was undertaken in younger subjects (age ≤40 years).

RESULTS

Comparing G+P- and G-P- individuals, there were no significant differences in left ventricular ejection fraction, cavity size, wall thickness and outflow tract gradient, and tissue Doppler-derived myocardial velocities; however, septal/posterior wall thickness ratio was higher (1.06±0.09 versus 1.02±0.04, P=0.007). G+P- individuals had significantly lower color M-mode flow propagation velocity (color M-mode velocity propagation, 42.6 cm/s [interquartile range, 34.5-48.5 cm/s] versus 51.0 cm/s [interquartile range, 45.2-61.0 cm/s]; P<0.001) and higher global longitudinal strain (P=0.021), circumferential strain (P=0.003), and peak apical rotation (P=0.005). Multivariable logistic regression identified 2 independent predictors (color M-mode velocity propagation and peak apical rotation). A derived regression equation allowed reasonable discrimination of G+P- individuals with a sensitivity of 82.6% and specificity of 72.2% (P<0.0001) at the optimal cutoff. Similar findings were demonstrated when the analysis was restricted to younger subjects, although in addition to color M-mode velocity propagation and apical rotation, left ventricular ejection fraction was also independently predictive.

CONCLUSIONS

In HCM family members, color M-mode velocity propagation and apical rotation provide good sensitivity and specificity for identifying mutation carriers and may represent early disease markers before the onset of hypertrophy. Longitudinal studies involving larger cohorts are required to validate these findings.

Valsartan and Cardiac Remodeling in Early-Stage Hypertrophic Cardiomyopathy: The VANISH Randomized Clinical Trial Cardiac Magnetic Resonance Substudy

Importance

Valsartan has been shown to attenuate phenotypic progression among individuals with early-stage sarcomeric hypertrophic cardiomyopathy (HCM). Myocardial tissue characterization by cardiac magnetic resonance (CMR) imaging may enhance mechanistic insights, but whether valsartan influences these parameters remains uncertain.

Objective

To evaluate the treatment effects of valsartan on myocardial structure, function, and tissue parameters in early-stage sarcomeric HCM.

Design, Setting, and Participants

This prespecified CMR substudy of the VANISH (Valsartan for Attenuating Disease Evolution in Early Sarcomeric Hypertrophic Cardiomyopathy) randomized clinical trial evaluated treatment effects of valsartan vs placebo on myocardial structure, function, and tissue parameters and was conducted from April 2014 through July 2019 at 17 international sites. Individuals aged 8 to 45 years with early-stage HCM aged between 8 and 45 years and with no or minimal symptoms were eligible for inclusion.

Interventions

Treatment with placebo or valsartan (80 mg per day for children weighing <35 kg, 160 mg per day for children weighing ≥35 kg, or 320 mg per day for adults aged 18 years or older).

Main Outcomes and Measures

The primary outcome was mean change in CMR parameters between baseline and year 2, including indexed extracellular volume (iECV), indexed intracellular volume (iICV), and late gadolinium enhancement (LGE). Mean between-group differences in CMR parameters between baseline and year 2 were evaluated using multivariable mixed-effects linear regression models.

Results

Overall, 137 of 178 VANISH participants (77.0%) underwent CMR imaging at baseline and year 2. Among these participants, mean (SD) age was 23 (10) years, and 51 participants (37.2%) were female. Baseline characteristics and CMR parameters were well balanced between treatment groups. Higher LGE, iECV, and iICV at baseline were associated with higher cardiac biomarker levels and more pronounced cardiac remodeling. Between baseline and year 2, valsartan appeared to increase left ventricular (LV) end-diastolic volume index (mean difference [MD], 3.3 mL/m2; 95% CI, 0.4-6.2; P = .03), suggesting treatment benefit, but did not significantly impact LV mass index (MD, -2.9 g/m2; 95% CI, -6.1 to 0.2; P = .07) or LV ejection fraction. Similarly, valsartan appeared to reduce decline in right ventricular volumes. Valsartan appeared to significantly reduce iICV progression (MD, -5.0 mL/m2; 95% CI, -9.7 to -0.4; P = .03), but did not impact iECV (MD, 0.0 mL/m2; 95% CI, -1.4 to 1.3; P = .95) or LGE progression (MD, 0.5%; 95% CI, -0.4 to 1.3; P = .30).

Conclusions and Relevance

These findings enhance mechanistic insights into the effect of valsartan in early-stage HCM, showing potential benefits on biventricular remodeling and myocardial intracellular volume. Further research to identify cellular mechanisms of valsartan on HCM progression is needed.

Trial Registration

ClinicalTrials.gov Identifier: NCT01912534.

The Complex Puzzle of Hypertrophic Phenotype: A Practical Approach for the Clinician

Left ventricular hypertrophy (LVH) represents a frequent observation in clinical practice. Nonetheless, the hypertrophic phenotype emerges as a common manifestation of diverse conditions, thereby presenting a diagnostic conundrum for clinicians. Differentiation among the etiologies of LVH is imperative for therapy decision-making, as different approaches must be implemented for distinct conditions, such as LVH secondary to loading changes, hypertrophic cardiomyopathy (HCM), or HCM mimics. In some instances, an erroneous or late diagnosis may lead to a progression of the underlying disease with worsening functional capacity, high morbidity and mortality. The rational use of cardiovascular multimodality imaging is of great importance when carried out in addition to a thorough clinical assessment and correlated with electrocardiographic findings, providing clues to fill the gaps, being, most of the time, the missing piece to solve this challenging puzzle. An integrative approach is of paramount importance for the evaluation of these patients, as they are often followed by several specialties, with varied systemic manifestations. Although a multidisciplinary team is needed for an optimized follow-up of these patients, the most important player in this journey is the clinician, whose mission is to bring together all the red flags and coordinate all the data for an assertive diagnosis. The objective of this review is to provide a pragmatic methodology, highlighting important clues for discriminating among the diverse conditions that result in LVH.

Advances in the study and treatment of genetic cardiomyopathies

Cardiomyopathies are primary disorders of the heart muscle. Three key phenotypes have been defined, based on morphology and arrhythmia burden: hypertrophic cardiomyopathy (HCM), with thickened heart muscle and diastolic dysfunction; dilated cardiomyopathy (DCM), with left ventricular enlargement and systolic dysfunction; and arrhythmogenic cardiomyopathy (ACM), with right, left, or biventricular involvement and arrhythmias out of proportion to systolic dysfunction. Genetic discoveries of the molecular basis of disease are paving the way for greater precision in diagnosis and management and revealing mechanisms that account for distinguishing clinical features. This deeper understanding has propelled the development of new treatments for cardiomyopathies: disease-specific, mechanistically based medicines that counteract pathophysiology, and emergent gene therapies that aim to intercept disease progression and restore cardiac physiology. Together, these discoveries have advanced fundamental insights into cardiac biology and herald a new era for patients with cardiomyopathy.

CT and MR Imaging of Cardiomyopathies in Clinical Practice-An Approach After an Abnormal Echocardiogram or Electrocardiogram

Cardiomyopathies represent a diverse group of myocardial disorders characterized by structural and functional abnormalities in the absence of significant coronary artery disease or other primary causes. This review highlights the diagnostic and prognostic value of cardiac magnetic resonance and computed tomography in the assessment of cardiomyopathies. While echocardiography remains the first-line imaging modality, cardiac magnetic resonance (CMR) and cardiac computerized tomography (CCT) offer superior tissue characterization, morphological assessment, and functional evaluation, crucial for phenotyping cardiomyopathies into hypertrophic, dilated, restrictive, arrhythmogenic, and non-dilated left ventricular subtypes. For hypertrophic cardiomyopathy, CMR enables precise identification of fibrosis, hypertrophy distribution, and risk stratification for sudden cardiac death. CMR is pivotal in identifying phenocopies, like cardiac amyloidosis and Anderson-Fabry disease, and differentiating between pathological and physiological remodeling in athlete's heart. For dilated cardiomyopathy, late gadolinium enhancement, T1 mapping, and extracellular volume measurements aid in distinguishing etiologies and predicting adverse outcomes. In arrhythmogenic right ventricular cardiomyopathy, CMR demonstrates superior sensitivity for detecting structural abnormalities in the right ventricle, and the presence of fibrosis which is associated with arrhythmic risk. CCT main roles are excluding coronary artery disease and complementing CMR. This review proposes a diagnostic pathway integrating multimodality imaging for clinical management in cardiomyopathies.

Myocardial disarray and fibrosis across hypertrophic cardiomyopathy stages associate with ECG markers of arrhythmic risk

AIMS

Myocardial disarray, an early feature of hypertrophic cardiomyopathy (HCM) and a substrate for ventricular arrhythmia, is poorly characterized in pre-hypertrophic sarcomeric variant carriers (SARC+LVH-). Using diffusion tensor cardiac magnetic resonance (DT-CMR) we assessed myocardial disarray and fibrosis in both SARC+LVH- and HCM patients and evaluated the relationship between microstructural alterations and electrocardiographic (ECG) parameters associated with arrhythmic risk.

METHODS AND RESULTS

Sixty-two individuals (24 SARC+LVH-, 24 HCM, and 14 matched controls) were evaluated with multi-parametric CMR including stimulated echo acquisition mode DT-CMR, and blinded quantitative 12-lead ECG analysis. Mean diastolic fractional anisotropy (FA) was reduced in HCM compared with SARC+LVH- and controls (0.49 ± 0.05 vs. 0.52 ± 0.04 vs. 0.53 ± 0.04, P = 0.009), even after adjustment for differences in extracellular volume (ECV) (P = 0.038). Both HCM and SARC+LVH- had segments with significantly reduced diastolic FA relative to controls (54 vs. 25 vs. 0%, P = 0.002). Multiple repolarization parameters were prolonged in HCM and SARC+LVH-, with corrected JT interval (JTc) being most significant (354 ± 42 vs. 356 ± 26 vs. 314 ± 26 ms, P = 0.002). Among SARC+LVH-, JTc duration correlated negatively with mean diastolic FA (r = -0.6, P = 0.002). In HCM, the JTc interval showed a stronger association with ECV (r = 0.6 P = 0.019) than with mean diastolic FA (r = -0.1 P = 0.72). JTc discriminated SARC+LVH- from controls [area under the receiver operator curve 0.88, confidence interval 0.76-1.00, P < 0.001], and in HCM correlated with the European Society of Cardiology HCM sudden cardiac death risk score (r = 0.5, P = 0.014).

CONCLUSION

Low diastolic FA, suggestive of myocardial disarray, is present in both SARC+LVH- and HCM. Low FA and raised ECV were associated with repolarization prolongation. Myocardial disarray assessment using DT-CMR and repolarization parameters such as the JTc interval demonstrate significant potential as markers of disease activity in HCM.

Advancing Cardiovascular Diagnostics: The Expanding Role of CMR in Heart Failure and Cardiomyopathies

Cardiovascular magnetic resonance (CMR) imaging has become a cornerstone in the diagnosis, risk stratification, and management of cardiovascular disease (CVD), particularly heart failure (HF) and cardiomyopathies. Renowned as the gold standard for non-invasive quantification of ventricular volumes and ejection fraction, CMR delivers superior spatial and temporal resolution with excellent tissue-blood contrast. Recent advancements, including T1, T2, and T2* mapping, extracellular volume quantification, and late gadolinium enhancement, enable precise tissue characterization, allowing early detection of myocardial changes such as fibrosis, edema, and infiltration. These features provide critical insights into the pathophysiological mechanisms underlying HF phenotypes and diverse cardiomyopathies, enhancing diagnostic accuracy and guiding therapeutic decisions. This review explores the expanding role of CMR in CV disease, highlighting its diagnostic value in HF and in several cardiomyopathies, as well as its contribution to improving patient outcomes through detailed tissue characterization and prognosis.

Circulating microRNA as promising biomarkers in hypertrophic cardiomyopathy: can advanced cardiac magnetic resonance unlock new insights in research?

Hypertrophic cardiomyopathy (HCM) is a genetic cardiac disorder associated with an increased risk of arrhythmias, heart failure, and sudden cardiac death. Current imaging and clinical markers are not fully sufficient in accurate diagnosis and patient risk stratification. Although known cardiac biomarkers in blood are used, they lack specificity for HCM and primarily stratify for death due to heart failure in overt cases. Non-coding RNAs, particularly microRNAs, have emerged as promising biomarkers due to their role in regulating gene expression in both healthy and pathological hearts. Circulating microRNA signatures may dynamically reflect the progression of HCM, offering potential utility in diagnosis and disease monitoring as well as inform biologic pathways for innovative therapeutic strategies. However, studying microRNAs in cardiovascular diseases is still in its early stages and poses many challenges. This review focuses on emerging research perspectives using advanced cardiac magnetic resonance techniques. We presume, that the search for circulating miR signatures associated with specific adverse myocardial features observed on cardiac magnetic resonance imaging - such as fibrosis, disarray, and microvascular disease - represents a promising direction in HCM research.

Investigating cardiac genetic background in sudden infant death syndrome (SIDS)

Sudden infant death syndrome (SIDS) is still the leading cause of death for newborns in developed countries. The pathophysiological mechanisms have not been fully clarified, but in some of SIDS cases variants of genes associated with inherited cardiac conditions are found. In this study, an analysis of SCD-related genes was performed to determine the prevalence of rare pathogenic (P) or likely pathogenic (LP) variants that could provide an unambiguous explanation for the fatal event. A cohort of 76 SIDS cases underwent Next-Generation Sequencing (NGS) analysis with a custom panel of SCD-related genes. Rare variants were classified according to the guidelines provided by the American College of Medical Genetics and Genomics (ACMG) and the specifications of the ClinGen association. Post-mortem genetic testing identified 50 (65.8%) carriers of at least one variant in SCD genes. 104 rare genetic variants were found, 65.4% in genes encoding structural proteins. Only 4 out of 76 cases (5.3%) hosted at least a P or LP variant found in genes with structural or structural/arrhythmogenic functions (SLC22A5, SCN5A, MYL3and TTN). 99 variants were classified as of uncertain significance (VUS). The difference in the distribution of variants between gene groups by function was not statistically significant (chi square, p = 0,219). Despite this, most of the variants concerned structural genes that were supposed to have a close interaction with ion channels, thus providing an explanation for the arrhythmic event. Segregation analysis, reclassification of VUS variants and identification of new associated genes could clarify the implications of the current findings.

Genetic Testing Practices and Pathological Assessments in Patients With End-stage Heart Failure Undergoing Heart Transplantation and Left Ventricular Assist Device Use

BACKGROUND

Genetic cardiomyopathies (CMs) are increasingly recognized as causes of end-stage heart failure (ESHF). Identification of a genetic etiology in ESHF has important prognostic and family implications. However, genetic testing practices are understudied in patients with ESHF.

METHODS

This single-center, retrospective study included consecutive patients with ESHF who underwent heart transplantation (HT) or left ventricular assist device (LVAD) implantation between 2018 and 2023. Data, including genetic testing and pathology reports, were collected from the electronic medical records. Analyses of demographic and clinical characteristics were stratified by genetic-testing completion and the presence of clinically actionable variants. Logistic regression was performed to evaluate for associations between histology findings and genetic variants.

RESULTS

A total of 529 adult patients (mean age 57 years) were included in the study and were predominantly male (79%, 422/529) and non-white (61%, 322/529). Genetic testing was performed in 54% (196/360) of patients with either nonischemic or mixed CMs. A clinically actionable result was identified in 36% (70/196) of patients, of whom only 43% (30/70) had genetic counselor referrals. The most common genetic variants were TTN (32%, 24/75), MYBPC3 (13%, 10/75) and TTR (11%, 8/75). Clinically actionable variants were identified in patients with known heart failure precipitators such as alcohol use. In multivariable analysis, the presence of interstitial fibrosis, specifically diffuse, on pathology was significantly associated with a clinically actionable variant (aOR 2.29, 95% CI [1.08-4.86]; P = 0.03).

CONCLUSION

Patients with ESHF and with nonischemic or mixed CM who were undergoing advanced therapies had low uptakes of genetic services, including testing and counselors, despite high burdens of genetic disease. Pathology findings such as interstitial fibrosis may provide insight into genetic etiology. The underuse of services suggests a need for implementation strategies to improve uptake.

Clinical Applications of Cardiac Magnetic Resonance Parametric Mapping

Cardiovascular magnetic resonance (CMR) imaging is widely regarded as the gold-standard technique for myocardial tissue characterization, allowing for the detection of structural abnormalities such as myocardial fatty replacement, myocardial edema, myocardial necrosis, and/or fibrosis. Historically, the identification of abnormal myocardial regions relied on variations in tissue signal intensity, often necessitating the use of exogenous contrast agents. However, over the past two decades, innovative parametric mapping techniques have emerged, enabling the direct quantitative assessment of tissue magnetic resonance (MR) properties on a voxel-by-voxel basis. These mapping techniques offer significant advantages by providing comprehensive and precise information that can be translated into color-coded maps, facilitating the identification of subtle or diffuse myocardial abnormalities. As unlikely conventional methods, these techniques do not require a substantial amount of structurally altered tissue to be visually identifiable as an area of abnormal signal intensity, eliminating the reliance on contrast agents. Moreover, these parametric mapping techniques, such as T1, T2, and T2* mapping, have transitioned from being primarily research tools to becoming valuable assets in the clinical diagnosis and risk stratification of various cardiac disorders. In this review, we aim to elucidate the underlying physical principles of CMR parametric mapping, explore its current clinical applications, address potential pitfalls, and outline future directions for research and development in this field.

Genetics of hypertrophic cardiomyopathy: established and emerging implications for clinical practice

Pathogenic variation in genes encoding proteins of the cardiac sarcomere is responsible for 30%-40% of cases of hypertrophic cardiomyopathy. The main clinical utility of genetic testing is to provide diagnostic confirmation and facilitation of family screening. It also assists in the detection of aetiologies, which require distinct monitoring and treatment approaches. Other clinical applications, including the use of genetic information to inform risk prediction models, have been limited by the challenge of establishing robust genotype-phenotype correlations with actionable consequences, but new data on the interaction between rare and common genetic variation, as well as the emergence of therapies targeting disease-specific pathogenic mechanisms, herald a new era for genetic testing in routine practice.

Phenotypic Spectrum of Subclinical Sarcomere-Related Hypertrophic Cardiomyopathy and Transition to Overt Disease

Genetic hypertrophic cardiomyopathy (HCM) is classically caused by pathogenic/likely pathogenic variants in sarcomere genes (G+). Currently, HCM is diagnosed if there is unexplained left ventricular (LV) hypertrophy with LV wall thickness ≥15 mm in probands or ≥13 mm in at-risk relatives. Although LV hypertrophy is a key feature, this binary metric does not encompass the full constellation of phenotypic features, particularly in the subclinical stage of the disease. Subtle phenotypic manifestations can be identified in sarcomere variant carriers with normal LV wall thickness, before diagnosis with HCM (G+/LV hypertrophy-; subclinical HCM). We conducted a systematic review to summarize current knowledge about the phenotypic spectrum of subclinical HCM and factors influencing penetrance and expressivity. Although the mechanisms driving the development of LV hypertrophy are yet to be elucidated, activation of profibrotic pathways, impaired relaxation, abnormal Ca2+ signaling, altered myocardial energetics, and microvascular dysfunction have all been identified in subclinical HCM. Progression from subclinical to clinically overt HCM may be more likely if early phenotypic manifestations are present, including ECG abnormalities, longer mitral valve leaflets, lower global E' velocities on Doppler echocardiography, and higher serum N-terminal propeptide of B-type natriuretic peptide. Longitudinal studies of variant carriers are critically needed to improve our understanding of penetrance, characterize the transition to disease, identify risk predictors of phenotypic evolution, and guide the development of novel treatment strategies aimed at influencing disease trajectory.

"Interstitial fibrosis is associated with left atrial remodeling and adverse clinical outcomes in selected low-risk patients with hypertrophic cardiomyopathy"

BACKGROUND

Cardiovascular magnetic resonance (CMR) extracellular volume (ECV) allows non-invasive detection of myocardial interstitial fibrosis, which may be related to diastolic dysfunction and left atrial (LA) remodeling in hypertrophic cardiomyopathy (HCM). While the prognostic role of LGE is well-established, interstitial fibrosis and LA dysfunction are emerging novel markers in HCM. This study aimed to explore the interaction between interstitial fibrosis by ECV, LA morpho-functional parameters and adverse clinical outcomes in selected low-risk patients with HCM.

METHODS

115 HCM patients and 61 matched controls underwent CMR to identify: i) interstitial fibrosis by ECV in hypertrophied left ventricular LGE-negative remote myocardium (r-ECV); ii) LA indexed maximum (LAVi max) and minimum (LAVi min) volumes, ejection fraction (LA-EF) and strain (reservoir εs, conduit εe and booster εa), by CMR feature-tracking. 2D-echocardiographic assessment of diastolic function was also performed within 6 months from CMR. A composite endpoint including worsening NYHA class, heart failure hospitalization, atrial fibrillation and all-cause death was evaluated at 2.3 years follow-up. HCM patients were divided into two groups, according to r-ECV values of controls.

RESULTS

Patients with r-ECV ≥29% (n = 45) showed larger LA volumes (LAVimax 63 vs. 54 ml/m2, p < 0.001; LAVimin 43 vs. 28 ml/m2, p 〈0001), worse LA function (εs 16 vs. 28%, εe 8 vs. 15%, εa 8 vs. 14%, LA-EF 33 vs. 49%, all p < 0.001) and elevated Nt-proBNP (1115 vs. 382 pg/ml, p = 0.002). LA functional parameters inversely correlated with r-ECV (εs r = -0.54; LA-EF r = -0.46; all p < 0.001) and E/e' (εs r = -0.52, LA-EF r = -0.46; all p < 0.006). r-ECV ≥29% and LAVi min >30 ml/m2 have been identified as possible independent factors associated with the endpoint.

CONCLUSIONS

In HCM diffuse interstitial fibrosis detected by increased r-ECV is associated with LA remodeling and emerged as a potential independent predictor of adverse clinical outcomes, on top of the well-known prognostic impact of LGE.

The Role of Magnetic Resonance Imaging in Cardiomyopathies in the Light of New Guidelines: A Focus on Tissue Mapping

Cardiomyopathies (CMPs) are a group of myocardial disorders that are characterized by structural and functional abnormalities of the heart muscle. These abnormalities occur in the absence of coronary artery disease (CAD), hypertension, valvular disease, and congenital heart disease. CMPs are an increasingly important topic in the field of cardiovascular diseases due to the complexity of their diagnosis and management. In 2023, the ESC guidelines on cardiomyopathies were first published, marking significant progress in the field. The growth of techniques such as cardiac magnetic resonance imaging (CMR) and genetics has been fueled by the development of multimodal imaging approaches. For the diagnosis of CMPs, a multimodal imaging approach, including CMR, is recommended. CMR has become the standard for non-invasive analysis of cardiac morphology and myocardial function. This document provides an overview of the role of CMR in CMPs, with a focus on tissue mapping. CMR enables the characterization of myocardial tissues and the assessment of cardiac functions. CMR sequences and techniques, such as late gadolinium enhancement (LGE) and parametric mapping, provide detailed information on tissue composition, fibrosis, edema, and myocardial perfusion. These techniques offer valuable insights for early diagnosis, prognostic evaluation, and therapeutic guidance of CMPs. The use of quantitative CMR markers enables personalized treatment plans, improving overall patient outcomes. This review aims to serve as a guide for the use of these new tools in clinical practice.

Cardiac Magnetic Resonance Feature-Tracking Identifies Preclinical Abnormalities in Hypertrophic Cardiomyopathy Sarcomere Gene Mutation Carriers

BACKGROUND

Assessing myocardial strain by cardiac magnetic resonance feature tracking (FT) has been found to be useful in patients with overt hypertrophic cardiomyopathy (HCM). Little is known, however, of its role in sarcomere gene mutation carriers without overt left ventricular hypertrophy (subclinical HCM).

METHODS

Thirty-eight subclinical HCM subjects and 42 healthy volunteers were enrolled in this multicenter case-control study. They underwent a comprehensive cardiac magnetic resonance study. Two-dimensional global radial, circumferential, and longitudinal strain of the left ventricle (LV) were evaluated by FT analysis.

RESULTS

The subclinical HCM sample was 41 (22-51) years old and 32% were men. FT analysis revealed a reduction in global radial strain (29±7.2 versus 47.9±7.4; P<0.0001), global circumferential strain (-17.3±2.6 -versus -20.8±7.4; P<0.0001) and global longitudinal strain (-16.9±2.4 versus -20.5±2.6; P<0.0001) in subclinical HCM compared with control subjects. The significant differences persisted when considering the 23 individuals free of all the structural and functional ECG and cardiac magnetic resonance abnormalities previously described. Receiver operating characteristic curve analyses showed that the differential diagnostic performances of FT in discriminating subclinical HCM from normal subjects were good to excellent (global radial strain with optimal cut-off value of 40.43%: AUC, 0.946 [95% CI, 0.93-1.00]; sensitivity 90.48%, specificity 94.44%; global circumferential strain with cut-off, -18.54%: AUC, 0.849 [95% CI, 0.76-0.94]; sensitivity, 88.10%; specificity, 72.22%; global longitudinal strain with cut-off, -19.06%: AUC, 0.843 [95% CI, 0.76-0.93]; sensitivity, 78.57%; specificity, 78.95%). Similar values were found for discriminating those subclinical HCM subjects without other phenotypic abnormalities from healthy volunteers (global radial strain with optimal cut-off 40.43%: AUC, 0.966 [95% CI, 0.92-1.00]; sensitivity, 90.48%; specificity, 95.45%; global circumferential strain with cut-off, -18.44%: AUC, 0.866 [95% CI, 0.76-0.96]; sensitivity, 92.86%; specificity, 77.27%; global longitudinal strain with cut-off, -17.32%: AUC, 0.838 [95% CI, 0.73-0.94]; sensitivity, 90.48%; specificity, 65.22%).

CONCLUSIONS

Cardiac magnetic resonance FT-derived parameters are consistently lower in subclinical patients with HCM, and they could emerge as a good tool for discovering the disease during a preclinical phase.

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.

Anderson-Fabry Disease: Red Flags for Early Diagnosis of Cardiac Involvement

Anderson-Fabry disease (AFD) is a lysosome storage disorder resulting from an X-linked inheritance of a mutation in the galactosidase A (GLA) gene encoding for the enzyme alpha-galactosidase A (α-GAL A). This mutation results in a deficiency or absence of α-GAL A activity, with a progressive intracellular deposition of glycosphingolipids leading to organ dysfunction and failure. Cardiac damage starts early in life, often occurring sub-clinically before overt cardiac symptoms. Left ventricular hypertrophy represents a common cardiac manifestation, albeit conduction system impairment, arrhythmias, and valvular abnormalities may also characterize AFD. Even in consideration of pleiotropic manifestation, diagnosis is often challenging. Thus, knowledge of cardiac and extracardiac diagnostic "red flags" is needed to guide a timely diagnosis. Indeed, considering its systemic involvement, a multidisciplinary approach may be helpful in discerning AFD-related cardiac disease. Beyond clinical pearls, a practical approach to assist clinicians in diagnosing AFD includes optimal management of biochemical tests, genetic tests, and cardiac biopsy. We extensively reviewed the current literature on AFD cardiomyopathy, focusing on cardiac "red flags" that may represent key diagnostic tools to establish a timely diagnosis. Furthermore, clinical findings to identify patients at higher risk of sudden death are also highlighted.

Functional significance of myocardial activity at 18F-FAPI PET/CT in hypertrophic cardiomyopathy identified by cardiac magnetic resonance feature-tracking strain analysis

PURPOSE

This study aimed to evaluate the functional significance of 18F-labeled fibroblast activation protein inhibitor (18F-FAPI) activity in hypertrophic cardiomyopathy (HCM) by comparison with cardiac magnetic resonance feature-tracking (CMR-FT) strain analysis.

METHODS

A total of 49 HCM patients were included in this study. Two independent control groups of healthy participants with a matched age and sex to the HCM patients were also enrolled. Left ventricular (LV) 18F-FAPI activity was analyzed for extent (FAPI%) and intensity (maximum target-to-background ratio, TBRmax). The CMR tissue characterization parameters of the LV included late gadolinium enhancement, native T1 value, and extracellular volume fraction. LV strain analysis was performed in radial, circumferential, and longitudinal peak strains (PS).

RESULTS

Intense LV myocardial 18F-FAPI uptake was observed in HCM patients, whereas no obvious uptake was detected in healthy participants (median TBRmax, 9.1 vs. 1.2, p < 0.001). The strain parameters of HCM patients, compared with healthy participants, were significantly impaired (mean radial PS, 23.5 vs. 36.0, mean circumferential PS, -14.5 vs. -20.0, and mean longitudinal PS, -9.9 vs. -16.0, all p < 0.001). At segmental levels, there was a moderate correlation between 18F-FAPI activity and strain parameters. The number of positive 18F-FAPI uptake segments (n = 653) was higher than that of hypertrophic segments (n = 190) and positive CMR tissue characterization segments (n = 525) (all p < 0.001). In segments with negative CMR tissue characterization findings, the strain capacity of positive 18F-FAPI uptake segments was lower than that of negative 18F-FAPI uptake segments (median radial PS, 30.5 vs. 36.1, p = 0.026 and median circumferential PS, -18.4 vs. -19.7, p = 0.041).

CONCLUSION

18F-FAPI imaging can partially reflect the potential strain reduction in HCM patients. 18F-FAPI imaging detects more involved myocardium than CMR tissue characterization techniques, and the additionally identified myocardium has impaired strain capacity.

Current use of cardiac MRI in animals

Cardiovascular magnetic resonance (CMR) imaging has evolved to become an indispensable tool in human cardiology. It is a non-invasive technique that enables objective assessment of myocardial function, size, and tissue composition. Recent innovations in magnetic resonance imaging scanner technology and parallel imaging techniques have facilitated the generation of parametric mapping to explore tissue characteristics, and the emergence of strain imaging has enabled cardiologists to evaluate cardiac function beyond conventional metrics. As veterinary cardiology continues to utilize CMR beyond the reference standard, clinical application of CMR will further expand our capabilities. This article describes the current use of CMR and adoption of more recent advances such as T1/T2 mapping in veterinary cardiology.

Predicting Development of Hypertrophic Cardiomyopathy and Disease Outcomes in Cats

Echocardiography is the gold standard imaging modality to diagnose hypertrophic cardiomyopathy (HCM) in cats. Echocardiographic features can predict both cats at an increased risk of developing HCM and cats with HCM at an increased risk of developing cardiovascular events or experiencing cardiac death. Left atrial dysfunction seems to be an important feature of HCM, as it is an early phenotypic abnormality and is also associated with worse outcome.

Evaluation of cardiac fibrosis and subclinical cardiac changes in children with sickle cell disease using magnetic resonance imaging, echocardiography, and serum galectin-3

BACKGROUND

Myocardial fibrosis has recently been proposed as one of the contributing factors to the diverse pathogenicity of cardiomyopathy in sickle cell disease.

OBJECTIVE

In this study, cardiac fibrosis and subclinical cardiac changes in children with sickle cell disease were evaluated using cardiac magnetic resonance imaging (MRI), tissue Doppler echocardiography and serum galectin-3.

MATERIALS AND METHODS

The study included 34 children with sickle cell disease who were compared with a similar number of healthy controls. Cardiac MRI was used to evaluate late gadolinium enhancement, native T1 mapping, extracellular volume, and T2* for estimation of iron load. Cardiac function and myocardial performance index (MPI, evaluated by tissue Doppler echocardiography) and serum galectin-3 were compared to controls.

RESULTS

The mean age of the included patients was 13.3 ± 3.2 years. Myocardial iron load by T2* was normal. The mean level of extracellular volume (35.41 ± 5.02%) was significantly associated with the frequency of vaso-occlusive crises (P = 0.017) and negatively correlated with hemoglobin levels (P = 0.005). Galectin-3 levels were significantly higher among cases than controls (P = 0.00), at a cutoff value on the receiver operating characteristic curve of 6.5 ng/ml, sensitivity of 82.5% and specificity of 72.8%. The extracellular volume was significantly higher in cases, with a MPI > 0.4.

CONCLUSION

Diffuse interstitial myocardial fibrosis can be detected early in children with sickle cell disease using T1 mapping and is associated with a high frequency of vaso-occlusive crisis. MPI of the left ventricle and serum galectin-3 are recommended screening tools for subclinical cardiac abnormalities.

Myocardial Fibrosis in Hypertrophic Cardiomyopathy: A Perspective from Fibroblasts

Hypertrophic cardiomyopathy (HCM) is the most common inherited heart disease and the leading cause of sudden cardiac death in young people. Mutations in genes that encode structural proteins of the cardiac sarcomere are the more frequent genetic cause of HCM. The disease is characterized by cardiomyocyte hypertrophy and myocardial fibrosis, which is defined as the excessive deposition of extracellular matrix proteins, mainly collagen I and III, in the myocardium. The development of fibrotic tissue in the heart adversely affects cardiac function. In this review, we discuss the latest evidence on how cardiac fibrosis is promoted, the role of cardiac fibroblasts, their interaction with cardiomyocytes, and their activation via the TGF-β pathway, the primary intracellular signalling pathway regulating extracellular matrix turnover. Finally, we summarize new findings on profibrotic genes as well as genetic and non-genetic factors involved in the pathophysiology of HCM.

Multimodality imaging of hypertrophic cardiomyopathy

The diagnosis and management of hypertrophic cardiomyopathy (HCM) requires multimodality imaging. Transthoracic echocardiogram (TTE) remains the first-line imaging modality to diagnose HCM identifying morphology and obstruction, which includes left ventricular outflow obstruction, midcavitary obstruction and systolic anterior motion. Cardiac magnetic resonance imaging (CMR) can adjudicate equivocal cases, rule out alternative diagnoses and evaluate for risk factors of sudden cardiac death. Imaging with TTE or transesophageal echocardiogram can also guide alcohol septal ablation or surgical myectomy respectively. Furthermore, TTE can guide medical management of these patients by following peak gradients. Thus, multimodality imaging in HCM is crucial throughout the course of these patients' care.

Quantification of myocardial extracellular volume without blood sampling

Aims

Cardiac magnetic resonance (CMR) T1 relaxation time mapping is an established technique primarily used to identify diffuse interstitial fibrosis and oedema. The myocardial extracellular volume (ECV) can be calculated from pre- and post-contrast T1 relaxation times and is a reproducible parametric index of the proportion of volume occupied by non-cardiomyocyte components in myocardial tissue. The conventional calculation of the ECV requires blood sampling to measure the haematocrit (HCT). Given the high variability of the HCT, the blood collection is recommended within 24 h of the CMR scan, limiting its applicability and posing a barrier to the clinical routine use of ECV measurements. In recent years, several research groups have proposed a method to determine the ECV by CMR without blood sampling. This is based on the inverse relationship between the T1 relaxation rate (R1) of blood and the HCT. Consequently, a 'synthetic' HCT could be estimated from the native blood R1, avoiding blood sampling.

Methods and results

We performed a review and meta-analysis of published studies on synthetic ECV, as well as a secondary analysis of previously published data to examine the effect of the chosen regression modell on bias. While, overall, a good correlation and little bias between synthetic and conventional ECV were found in these studies, questions regarding its accuracy remain.

Conclusion

Synthetic HCT and ECV can provide a 'non-invasive' quantitative measurement of the myocardium's extracellular space when timely HCT measurements are not available and large alterations in ECV are expected, such as in cardiac amyloidosis. Due to the dependency of T1 relaxation times on the local setup, calculation of local formulas using linear regression is recommended, which can be easily performed using available data.

Circulating MicroRNAs Identify Early Phenotypic Changes in Sarcomeric Hypertrophic Cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is the most common genetic cardiomyopathy. Pathogenic germline variation in genes encoding the sarcomere is the predominant cause of disease. However diagnostic features, including unexplained left ventricular hypertrophy, typically do not develop until late adolescence or after. The early stages of disease pathogenesis and the mechanisms underlying the transition to a clinically overt phenotype are not well understood. In this study, we investigated if circulating microRNAs (miRNAs) could stratify disease stage in sarcomeric HCM.

METHODS

We performed arrays for 381 miRNAs using serum from HCM sarcomere variant carriers with and without a diagnosis of HCM and healthy controls. To identify differentially expressed circulating miRNAs between groups, multiple approaches were used including random forest, Wilcoxon rank sum test, and logistic regression. The abundance of all miRNAs was normalized to miRNA-320.

RESULTS

Of 57 sarcomere variant carriers, 25 had clinical HCM and 32 had subclinical HCM with normal left ventricular wall thickness (21 with early phenotypic manifestations and 11 with no discernible phenotypic manifestations). Circulating miRNA profile differentiated healthy controls from sarcomere variant carriers with subclinical and clinical disease. Additionally, circulating miRNAs differentiated clinical HCM from subclinical HCM without early phenotypic changes; and subclinical HCM with and without early phenotypic changes. Circulating miRNA profiles did not differentiate clinical HCM from subclinical HCM with early phenotypic changes, suggesting biologic similarity between these groups.

CONCLUSIONS

Circulating miRNAs may augment the clinical stratification of HCM and improve understanding of the transition from health to disease in sarcomere gene variant carriers.

Role of cardiovascular magnetic resonance in the clinical evaluation of left ventricular hypertrophy: a 360° panorama

Left ventricular hypertrophy (LVH) is a frequent imaging finding in the general population. In order to identify the precise etiology, a comprehensive diagnostic approach should be adopted, including the prevalence of each entity that may cause LVH, family history, clinical, electrocardiographic and imaging findings. By providing a detailed evaluation of the myocardium, cardiovascular magnetic resonance (CMR) has assumed a central role in the differential diagnosis of left ventricular hypertrophy, with the technique of parametric imaging allowing more refined tissue characterization. This article aims to establish a parallel between pathophysiological features and imaging findings through the broad spectrum of LVH entities, emphasizing the role of CMR in the differential diagnosis.

Circulating Biomarkers in Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy is the most common genetic heart disease. Biomarkers, molecules measurable in the blood, could inform the clinician by aiding in diagnosis, directing treatment, and predicting outcomes. We present an updated review of circulating biomarkers in hypertrophic cardiomyopathy representing key pathologic processes including wall stretch, myocardial necrosis, fibrosis, inflammation, hypertrophy, and endothelial dysfunction, in addition to their clinical significance.

Athletic Activity for Patients With Hypertrophic Cardiomyopathy and Other Inherited Cardiovascular Diseases: JACC Focus Seminar 3/4

As explored throughout this JACC Focus Seminar series, participation in regular exercise offers significant positive benefits for cardiovascular health. However, patients with underlying inherited cardiovascular diseases, such as hypertrophic cardiomyopathy, have historically been restricted from sports participation because of the risk of sudden cardiac death. Over the last decade, new data has challenged this restrictive approach. Today, the notion of individualized, patient-centered shared decision-making is being progressively adopted to guide patients with an inherited cardiovascular disease to decide if they can undertake regular exercise, or even if they can participate in competitive sports. Here in this part 3 of a 4-part seminar series, we focus on these concepts and recent data with respect to exercise and the heart in patients with hypertrophic cardiomyopathy and other inherited cardiovascular diseases, with particular emphasis on participation in recreational and competitive sports for these individuals.

Automated Dual-energy Computed Tomography-based Extracellular Volume Estimation for Myocardial Characterization in Patients With Ischemic and Nonischemic Cardiomyopathy

OBJECTIVES

We aimed to validate and test a prototype algorithm for automated dual-energy computed tomography (DECT)-based myocardial extracellular volume (ECV) assessment in patients with various cardiomyopathies.

METHODS

This retrospective study included healthy subjects (n=9; 61±10 y) and patients with cardiomyopathy (n=109, including a validation cohort n=60; 68±9 y; and a test cohort n=49; 69±11 y), who had previously undergone cardiac DECT. Myocardial ECV was calculated using a prototype-based fully automated algorithm and compared with manual assessment. Receiver-operating characteristic analysis was performed to test the algorithm's ability to distinguish healthy subjects and patients with cardiomyopathy.

RESULTS

The fully automated method led to a significant reduction of postprocessing time compared with manual assessment (2.2±0.4 min and 9.4±0.7 min, respectively, P <0.001). There was no significant difference in ECV between the automated and manual methods ( P =0.088). The automated method showed moderate correlation and agreement with the manual technique ( r =0.68, intraclass correlation coefficient=0.66). ECV was significantly higher in patients with cardiomyopathy compared with healthy subjects, regardless of the method used ( P <0.001). In the test cohort, the automated method yielded an area under the curve of 0.98 for identifying patients with cardiomyopathies.

CONCLUSION

Automated ECV estimation based on DECT showed moderate agreement with the manual method and matched with previously reported ECV values for healthy volunteers and patients with cardiomyopathy. The automatically derived ECV demonstrated an excellent diagnostic performance to discriminate between healthy and diseased myocardium, suggesting that it could be an effective initial screening tool while significantly reducing the time of assessment.

Ablation of lysophosphatidic acid receptor 1 attenuates hypertrophic cardiomyopathy in a mouse model

Myocardial fibrosis is a key pathologic feature of hypertrophic cardiomyopathy (HCM). However, the fibrotic pathways activated by HCM-causing sarcomere protein gene mutations are poorly defined. Because lysophosphatidic acid is a mediator of fibrosis in multiple organs and diseases, we tested the role of the lysophosphatidic acid pathway in HCM. Lysphosphatidic acid receptor 1 (LPAR1), a cell surface receptor, is required for lysophosphatidic acid mediation of fibrosis. We bred HCM mice carrying a pathogenic myosin heavy-chain variant (403+/-) with Lpar1-ablated mice to create mice carrying both genetic changes (403+/- LPAR1 -/-) and assessed development of cardiac hypertrophy and fibrosis. Compared with 403+/- LPAR1WT, 403+/- LPAR1 -/- mice developed significantly less hypertrophy and fibrosis. Single-nucleus RNA sequencing of left ventricular tissue demonstrated that Lpar1 was predominantly expressed by lymphatic endothelial cells (LECs) and cardiac fibroblasts. Lpar1 ablation reduced the population of LECs, confirmed by immunofluorescence staining of the LEC markers Lyve1 and Ccl21a and, by in situ hybridization, for Reln and Ccl21a. Lpar1 ablation also altered the distribution of fibroblast cell states. FB1 and FB2 fibroblasts decreased while FB0 and FB3 fibroblasts increased. Our findings indicate that Lpar1 is expressed predominantly by LECs and fibroblasts in the heart and is required for development of hypertrophy and fibrosis in an HCM mouse model. LPAR1 antagonism, including agents in clinical trials for other fibrotic diseases, may be beneficial for HCM.

Society for Cardiovascular Magnetic Resonance/European Society of Cardiovascular Imaging/American Society of Echocardiography/Society for Pediatric Radiology/North American Society for Cardiovascular Imaging Guidelines for the use of cardiovascular magnetic resonance in pediatric congenital and acquired heart disease : Endorsed by The American Heart Association

Cardiovascular magnetic resonance (CMR) has been utilized in the management and care of pediatric patients for nearly 40 years. It has evolved to become an invaluable tool in the assessment of the littlest of hearts for diagnosis, pre-interventional management and follow-up care. Although mentioned in a number of consensus and guidelines documents, an up-to-date, large, stand-alone guidance work for the use of CMR in pediatric congenital 36 and acquired 35 heart disease endorsed by numerous Societies involved in the care of these children is lacking. This guidelines document outlines the use of CMR in this patient population for a significant number of heart lesions in this age group and although admittedly, is not an exhaustive treatment, it does deal with an expansive list of many common clinical issues encountered in daily practice.

Society for Cardiovascular Magnetic Resonance/European Society of Cardiovascular Imaging/American Society of Echocardiography/Society for Pediatric Radiology/North American Society for Cardiovascular Imaging Guidelines for the Use of Cardiac Magnetic Resonance in Pediatric Congenital and Acquired Heart Disease: Endorsed by The American Heart Association

Cardiovascular magnetic resonance has been utilized in the management and care of pediatric patients for nearly 40 years. It has evolved to become an invaluable tool in the assessment of the littlest of hearts for diagnosis, pre-interventional management and follow-up care. Although mentioned in a number of consensus and guidelines documents, an up-to-date, large, stand-alone guidance work for the use of cardiovascular magnetic resonance in pediatric congenital 36 and acquired 35 heart disease endorsed by numerous Societies involved in the care of these children is lacking. This guidelines document outlines the use of cardiovascular magnetic resonance in this patient population for a significant number of heart lesions in this age group and although admittedly, is not an exhaustive treatment, it does deal with an expansive list of many common clinical issues encountered in daily practice.

The Impact of Mavacamten on the Pathophysiology of Hypertrophic Cardiomyopathy: A Narrative Review

Hypertrophic cardiomyopathy (HCM) is a chronic, progressive disease of the cardiomyocyte with a diverse and heterogeneous clinical presentation and course. This diversity and heterogeneity have added to the complexity of modeling the pathophysiological pathways that contribute to the disease burden. The development of novel therapeutic approaches targeting precise mechanisms within the underlying biology of HCM provides a tool to model and test these pathways. Here, we integrate the results of clinical observations with mavacamten, an allosteric, selective, and reversible inhibitor of cardiac myosin, the motor unit of the sarcomere, to develop an integrated pathophysiological pathway model of HCM, confirming the key role of excess sarcomeric activity. This model may serve as a foundation to understand the role of HCM pathophysiological pathways in the clinical presentation of the disease, and how a targeted therapeutic intervention capable of normalizing sarcomeric activity and repopulating low-energy utilization states may reduce the impact of these pathways in HCM and potentially related disease states.

Study protocol: MyoFit46-the cardiac sub-study of the MRC National Survey of Health and Development

BACKGROUND

The life course accumulation of overt and subclinical myocardial dysfunction contributes to older age mortality, frailty, disability and loss of independence. The Medical Research Council National Survey of Health and Development (NSHD) is the world's longest running continued surveillance birth cohort providing a unique opportunity to understand life course determinants of myocardial dysfunction as part of MyoFit46-the cardiac sub-study of the NSHD.

METHODS

We aim to recruit 550 NSHD participants of approximately 75 years+ to undertake high-density surface electrocardiographic imaging (ECGI) and stress perfusion cardiovascular magnetic resonance (CMR). Through comprehensive myocardial tissue characterization and 4-dimensional flow we hope to better understand the burden of clinical and subclinical cardiovascular disease. Supercomputers will be used to combine the multi-scale ECGI and CMR datasets per participant. Rarely available, prospectively collected whole-of-life data on exposures, traditional risk factors and multimorbidity will be studied to identify risk trajectories, critical change periods, mediators and cumulative impacts on the myocardium.

DISCUSSION

By combining well curated, prospectively acquired longitudinal data of the NSHD with novel CMR-ECGI data and sharing these results and associated pipelines with the CMR community, MyoFit46 seeks to transform our understanding of how early, mid and later-life risk factor trajectories interact to determine the state of cardiovascular health in older age.

TRIAL REGISTRATION

Prospectively registered on ClinicalTrials.gov with trial ID: 19/LO/1774 Multimorbidity Life-Course Approach to Myocardial Health- A Cardiac Sub-Study of the MCRC National Survey of Health and Development (NSHD).

T1 Mapping and Extracellular Volume in Cardiomyopathy Showing Left Ventricular Hypertrophy: Differentiation Between Hypertrophic Cardiomyopathy and Hypertensive Heart Disease

Background

Methods

Results

Conclusion

Myocardial tissue imaging with cardiovascular magnetic resonance

Alteration in myocardial tissue, such as myocardial fibrosis, edema, inflammation, or accumulation with amyloid, lipids, or iron, has an important role in the cardiac remodeling that leads to diastolic and/or systolic dysfunction and the development of chronic heart failure, increasing the risk of adverse cardiovascular events. Thus, the early detection of changes at myocardial tissue level has great diagnostic and prognostic potential. The gold standard technique to assess these myocardial alterations is endomyocardial biopsy. However, this has been limited to a few patients due to the invasive nature, sampling errors, and its inability to assess the entire myocardium. Cardiovascular magnetic resonance (CMR) has emerged as the gold standard imaging not only for assessing cardiac volume, function quantification, and viability but also for noninvasive myocardial tissue characterization over the past decade. Its ability to characterize myocardial tissue composition is unique among noninvasive imaging modalities in cardiovascular disease. Currently, multi-parametric myocardial characterization with T1, T2, and extracellular volume has the potential to identify and track diffuse pathology in various diseases. In this review article, we present the role of established and emerging CMR techniques in myocardial tissue characterization, with an emphasis on T1 and T2 mapping, in clinical practice.

Exercise prescription in individuals with hypertrophic cardiomyopathy: what clinicians need to know

Hypertrophic cardiomyopathy (HCM) is the most frequently cited cause of exercise-related sudden cardiac death (SCD) in young individuals and has claimed the lives of some high-profile athletes. The circumstantial link between exercise and SCD from HCM has resulted in conservative exercise recommendations which focus on activities that should be avoided rather than the minimal amount of physical activity required to reap the multiple rewards of exercise. Consequently, most patients with HCM are confined to a sedentary lifestyle through fear of SCD, with accruing risk factors such as obesity and low cardiorespiratory fitness that confer a worse prognosis. Recent exercise programmes in asymptomatic and symptomatic individuals with HCM have shown that mild and moderate exercise is safe and accompanied by increased functional capacity and improved quality of life. Population studies also reveal that individuals with HCM in the higher quartiles of self-reported physical activity have lower total cardiovascular mortality compared with those in the lower quartiles. The impact of vigorous exercise on the natural history of HCM is unknown, although current experience suggests that affected adults with mild morphology and absence of high-risk factors may partake in such activity without adverse events. This review highlights the evidence base that has resulted in a paradigm shift in the approach to exercise in HCM and liberalised recent international exercise guidelines in HCM. Practical tips for prescribing exercise in symptomatic patients and relevant precautions are provided to aid clinicians when recommending exercise as part of the management plan for all patients with HCM.

Myocardial Parametric Mapping by Cardiac Magnetic Resonance Imaging in Pediatric Cardiology and Congenital Heart Disease

Parametric mapping, that is, a pixel-wise map of magnetic relaxation parameters, expands the diagnostic potential of cardiac magnetic resonance by enabling quantification of myocardial tissue-specific magnetic relaxation on an absolute scale. Parametric mapping includes T₁ mapping (native and postcontrast), T₂ and T₂* mapping, and extracellular volume measurements. The myocardial composition is altered in various disease states affecting its inherent magnetic properties and thus the myocardial relaxation times that can be directly quantified using parametric mapping. Parametric mapping helps in the diagnosis of nonfocal disease states and allows for longitudinal disease monitoring, evaluating therapeutic response (as in Thalassemia patients with iron overload undergoing chelation), and risk-stratification of certain diseases. In this review article, we describe various mapping techniques and their clinical utility in congenital heart disease. We will also review the available literature on normative values in children, the strengths, and weaknesses of these techniques. This review provides a starting point for pediatric cardiologists to understand and implement parametric mapping in their practice.

Natural history of hypertrophic cardiomyopathy in cats from rehoming centers: The CatScan II study

BACKGROUND

The natural history of hypertrophic cardiomyopathy (HCM) in cats has been mainly studied in cats referred for suspected heart disease, which can skew the results towards cats with clinical signs. Few data are available on factors associated with development of HCM in cats.

HYPOTHESES

(1) Clinical variables can predict which cats will develop HCM; (2) HCM in cats not referred for suspected heart disease is associated with a low rate of cardiovascular events.

ANIMALS

One hundred seven cats from rehoming centers without a history of clinical signs of cardiac or systemic disease at the time of adoption.

METHODS

Prospective longitudinal study. After rehoming, shelter cats were reexamined for serial echocardiograms. Cox regression analysis was used to identify predictors of development of HCM in cats that were normal at baseline. Adverse cardiovascular events including heart failure, thromboembolism, or sudden death were recorded.

RESULTS

Cats were monitored for a median of 5.6 [1.2-9.2] years. At baseline, 68/107 cats were normal, 18/107 were equivocal and 21/107 had HCM. Nineteen cats developed HCM during the study period. The factors at baseline associated with increased hazard of developing HCM were lower left atrial fractional shortening, higher left ventricular fractional shortening, and higher body weight. Cardiovascular events were observed in 21% of cats with HCM.

CONCLUSIONS AND CLINICAL IMPORTANCE

Cardiovascular events were common in cats with HCM from a rehoming center study sample. Lower left atrial systolic function appears to precede overt HCM.

Novel Morphological Features on CMR for the Prediction of Pathogenic Sarcomere Gene Variants in Subjects Without Hypertrophic Cardiomyopathy

Background: Carriers of pathogenic DNA variants (G+) causing hypertrophic cardiomyopathy (HCM) can be identified by genetic testing. Several abnormalities have been brought forth as pre-clinical expressions of HCM, some of which can be identified by cardiovascular magnetic resonance (CMR). In this study, we assessed morphological differences between G+/left ventricular hypertrophy-negative (LVH-) subjects and healthy controls and examined whether CMR-derived variables are useful for the prediction of sarcomere gene variants.

Methods: We studied 57 G+ subjects with a maximal wall thickness (MWT) < 13 mm, and compared them to 40 healthy controls matched for age and sex on a group level. Subjects underwent CMR including morphological, volumetric and function assessment. Logistic regression analysis was performed for the determination of predictive CMR characteristics, by which a scoring system for G+ status was constructed.

Results: G+/LVH- subjects were subject to alterations in the myocardial architecture, resulting in a thinner posterior wall thickness (PWT), higher interventricular septal wall/PWT ratio and MWT/PWT ratio. Prominent hook-shaped configurations of the anterobasal segment were only observed in this group. A model consisting of the anterobasal hook, multiple myocardial crypts, right ventricular/left ventricular ratio, MWT/PWT ratio, and MWT/left ventricular mass ratio predicted G+ status with an area under the curve of 0.92 [0.87–0.97]. A score of ≥3 was present only in G+ subjects, identifying 56% of the G+/LVH- population.

Conclusion: A score system incorporating CMR-derived variables correctly identified 56% of G+ subjects. Our results provide further insights into the wide phenotypic spectrum of G+/LVH- subjects and demonstrate the utility of several novel morphological features. If genetic testing for some reason cannot be performed, CMR and our purposed score system can be used to detect possible G+ carriers and to aid planning of the control intervals.