Phenotypes of hypertrophic cardiomyopathy. An illustrative review of MRI findings

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.

Advanced Computed Tomography and Magnetic Resonance Imaging in Ischemic and Nonischemic Cardiomyopathies

Cardiomyopathies represent a diverse group of heart diseases that can be broadly classified into ischemic and nonischemic etiologies, each requiring distinct diagnostic approaches. Noninvasive imaging modalities, such as computed tomography (CT) and magnetic resonance imaging (MRI), play a pivotal role in the diagnosis, risk stratification, and prognosis of these conditions. This paper reviews the characteristic CT and MRI findings associated with ischemic cardiomyopathy (ICM) and nonischemic cardiomyopathy (NICM), focusing on their ability to provide detailed anatomical, functional, and tissue characterization. In ICM, CT and MRI reveal myocardial scarring, infarct size, and coronary artery disease, while MRI further distinguishes tissue viability through late gadolinium enhancement (LGE). Conversely, nonischemic cardiomyopathies demonstrate a wide array of findings, with MRI's LGE pattern analysis being particularly critical for identifying specific subtypes, such as restrictive, hypertrophic, or dilated cardiomyopathies. By comparing the strengths and limitations of these modalities, this paper highlights their complementary roles in improving diagnostic accuracy, risk stratification, prognosis, and therapeutic decision making in both ischemic and nonischemic cardiomyopathies.

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.

Austrian consensus statement on the diagnosis and management of hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most common inherited heart disease that is characterized by left ventricular hypertrophy unexplained by secondary causes. Based on international epidemiological data, around 20,000-40,000 patients are expected to be affected in Austria. Due to the wide variety of clinical and morphological manifestations the diagnosis can be difficult and the disease therefore often goes unrecognized. HCM is associated with a substantial reduction in quality of life and can lead to sudden cardiac death, especially in younger patients. Early and correct diagnosis, including genetic testing, is essential for comprehensive counselling of patients and their families and for effective treatment. The latter is especially true as an effective treatment of outflow tract obstruction has recently become available in the form of a first in class cardiac myosin ATPase inhibitor, as a noninvasive alternative to established septal reduction therapies. The aim of this Austrian consensus statement is to summarize the recommendations of international guidelines with respect to the genetic background, pathophysiology, diagnostics and management in the context of the Austrian healthcare system and resources, and to present them in easy to understand algorithms.

A Cautionary Tale of Hypertrophic Cardiomyopathy-From "Benign" Left Ventricular Hypertrophy to Stroke, Atrial Fibrillation, and Molecular Genetic Diagnostics: A Case Report and Review of Literature

This case report concerns a 48-year-old man with a history of ischemic stroke at the age of 41 who reported cardiac hypertrophy, registered in his twenties when explained by increased physical activity. Family history was positive for a mother with permanent atrial fibrillation from her mid-thirties. At the age of 44, he had a first episode of persistent atrial fibrillation, accompanied by left atrial thrombosis while on a direct oral anticoagulant. He presented at our clinic at the age of 45 with another episode of persistent atrial fibrillation and decompensated heart failure. Echocardiography revealed a dilated left atrium, reduced left ventricular ejection fraction, and an asymmetric left ventricular hypertrophy. Cardiac magnetic resonance was positive for a cardiomyopathy with diffuse fibrosis, while slow-flow phenomenon was present on coronary angiography. Genetic testing by whole-exome sequencing revealed three variants in the patient, c.309C > A, p.His103Gln in the ACTC1 gene, c.116T > G, p.Leu39Ter in the PLN gene, and c.5827C > T, p.His1943Tyr in the SCN5A gene, the first two associated with hypertrophic cardiomyopathy and the latter possibly with familial atrial fibrillation. This case illustrates the need for advanced diagnostics in unexplained left ventricular hypertrophy, as hypertrophic cardiomyopathy is often overlooked, leading to potentially debilitating health consequences.

Post-hoc standardisation of parametric T1 maps in cardiovascular magnetic resonance imaging: a proof-of-concept

BACKGROUND

In cardiovascular magnetic resonance imaging parametric T1 mapping lacks universally valid reference values. This limits its extensive use in the clinical routine. The aim of this work was the introduction of our self-developed Magnetic Resonance Imaging Software for Standardization (MARISSA) as a post-hoc standardisation approach.

METHODS

Our standardisation approach minimises the bias of confounding parameters (CPs) on the base of regression models. 214 healthy subjects with 814 parametric T1 maps were used for training those models on the CPs: age, gender, scanner and sequence. The training dataset included both sex, eleven different scanners and eight different sequences. The regression model type and four other adjustable standardisation parameters were optimised among 240 tested settings to achieve the lowest coefficient of variation, as measure for the inter-subject variability, in the mean T1 value across the healthy test datasets (HTE, N = 40, 156 T1 maps). The HTE were then compared to 135 patients with left ventricular hypertrophy including hypertrophic cardiomyopathy (HCM, N = 112, 121 T1 maps) and amyloidosis (AMY, N = 24, 24 T1 maps) after applying the best performing standardisation pipeline (BPSP) to evaluate the diagnostic accuracy.

FINDINGS

The BPSP reduced the COV of the HTE from 12.47% to 5.81%. Sensitivity and specificity reached 95.83% / 91.67% between HTE and AMY, 71.90% / 72.44% between HTE and HCM, and 87.50% / 98.35% between HCM and AMY.

INTERPRETATION

Regarding the BPSP, MARISSA enabled the comparability of T1 maps independently of CPs while keeping the discrimination of healthy and patient groups as found in literature.

FUNDING

This study was supported by the BMBF / DZHK.

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.

Hypertrophic cardiomyopathy in MYBPC3 carriers in aging

Hypertrophic cardiomyopathy (HCM) is characterized by abnormal thickening of the myocardium, leading to arrhythmias, heart failure, and elevated risk of sudden cardiac death, particularly among the young. This inherited disease is predominantly caused by mutations in sarcomeric genes, among which those in the cardiac myosin binding protein-C3 (MYBPC3) gene are major contributors. HCM associated with MYBPC3 mutations usually presents in the elderly and ranges from asymptomatic to symptomatic forms, affecting numerous cardiac functions and presenting significant health risks with a spectrum of clinical manifestations. Regulation of MYBPC3 expression involves various transcriptional and translational mechanisms, yet the destiny of mutant MYBPC3 mRNA and protein in late-onset HCM remains unclear. Pathogenesis related to MYBPC3 mutations includes nonsense-mediated decay, alternative splicing, and ubiquitin-proteasome system events, leading to allelic imbalance and haploinsufficiency. Aging further exacerbates the severity of HCM in carriers of MYBPC3 mutations. Advancements in high-throughput omics techniques have identified crucial molecular events and regulatory disruptions in cardiomyocytes expressing MYBPC3 variants. This review assesses the pathogenic mechanisms that promote late-onset HCM through the lens of transcriptional, post-transcriptional, and post-translational modulation of MYBPC3, underscoring its significance in HCM across carriers. The review also evaluates the influence of aging on these processes and MYBPC3 levels during HCM pathogenesis in the elderly. While pinpointing targets for novel medical interventions to conserve cardiac function remains challenging, the emergence of personalized omics offers promising avenues for future HCM treatments, particularly for late-onset cases.

Improved Cardiac Performance and Decreased Arrhythmia in Hypertrophic Cardiomyopathy With Non-β-Blocking R-Enantiomer Carvedilol

BACKGROUND

Hypercontractility and arrhythmia are key pathophysiologic features of hypertrophic cardiomyopathy (HCM), the most common inherited heart disease. β-Adrenergic receptor antagonists (β-blockers) are the first-line therapy for HCM. However, β-blockers commonly selected for this disease are often poorly tolerated in patients, where heart-rate reduction and noncardiac effects can lead to reduced cardiac output and fatigue. Mavacamten, myosin ATPase inhibitor recently approved by the US Food and Drug Administration, has demonstrated the ability to ameliorate hypercontractility without lowering heart rate, but its benefits are so far limited to patients with left ventricular (LV) outflow tract obstruction, and its effect on arrhythmia is unknown.

METHODS

We screened 21 β-blockers for their impact on myocyte contractility and evaluated the antiarrhythmic properties of the most promising drug in a ventricular myocyte arrhythmia model. We then examined its in vivo effect on LV function by hemodynamic pressure-volume loop analysis. The efficacy of the drug was tested in vitro and in vivo compared with current therapeutic options (metoprolol, verapamil, and mavacamten) for HCM in an established mouse model of HCM (Myh6R403Q/+ and induced pluripotent stem cell (iPSC)-derived cardiomyocytes from patients with HCM (MYH7R403Q/+).

RESULTS

We identified that carvedilol, a β-blocker not commonly used in HCM, suppresses contractile function and arrhythmia by inhibiting RyR2 (ryanodine receptor type 2). Unlike metoprolol (a β1-blocker), carvedilol markedly reduced LV contractility through RyR2 inhibition, while maintaining stroke volume through α1-adrenergic receptor inhibition in vivo. Clinically available carvedilol is a racemic mixture, and the R-enantiomer, devoid of β-blocking effect, retains the ability to inhibit both α1-receptor and RyR2, thereby suppressing contractile function and arrhythmias without lowering heart rate and cardiac output. In Myh6R403Q/+ mice, R-carvedilol normalized hyperdynamic contraction, suppressed arrhythmia, and increased cardiac output better than metoprolol, verapamil, and mavacamten. The ability of R-carvedilol to suppress contractile function was well retained in MYH7R403Q/+ iPSC-derived cardiomyocytes.

CONCLUSIONS

R-enantiomer carvedilol attenuates hyperdynamic contraction, suppresses arrhythmia, and at the same time, improves cardiac output without lowering heart rate by dual blockade of α1-adrenergic receptor and RyR2 in mouse and human models of HCM. This combination of therapeutic effects is unique among current therapeutic options for HCM and may particularly benefit patients without LV outflow tract obstruction.

Magnetic Resonance Left Ventricle Mass-Index/Fibrosis: Long-Term Predictors for Ventricular Arrhythmia in Hypertrophic Cardiomyopathy—A Retrospective Registry

Objective: We aimed to study the long-term association of LV mass index (LVMI) and myocardial fibrosis with ventricular arrhythmia (VA) in a population of patients with confirmed hypertrophic cardiomyopathy (HCM) using cardiac magnetic resonance imaging (CMR). Methods: We retrospectively analyzed the data in consecutive HCM patients confirmed on CMR referred to an HCM clinic between January 2008 and October 2018. Patients were followed up yearly following diagnosis. Baseline demographics, risk factors and clinical outcomes from cardiac monitoring and an implanted cardioverter defibrillator (ICD) were analyzed for association of LVMI and LV late gadolinium enhancement (LVLGE) with VA. Patients were then allocated to one of two groups according to the presence of VA (Group A) or absence of VA (Group B) during the follow-up period. The transthoracic echocardiogram (TTE) and CMR parameters were compared between the two groups. Results: A total of 247 patients with confirmed HCM (age 56.2 ± 16.6, male = 71%) were studied over the follow-up period of 7 ± 3.3 years (95% CI = 6.6–7.4 years). LVMI derived from CMR was higher in Group A (91.1 ± 28.1 g/m2 vs. 78.8 ± 28.3 g/m2, p = 0.003) when compared to Group B. LVLGE was higher in Group A (7.3 ± 6.3% vs. 4.7 ± 4.3%, p = 0.001) when compared to Group B. Multivariable Cox regression analysis showed LVMI (hazard ratio (HR) = 1.02, 95% CI = 1.001–1.03, p = 0.03) and LVLGE (HR = 1.04, 95% CI = 1.001–1.08, p = 0.04) to be independent predictors for VA. Receiver operative curves showed higher LVMI and LVLGE with a cut-off of 85 g/m2 and 6%, respectively, to be associated with VA. Conclusions: LVMI and LVLGE are strongly associated with VA over long-term follow-up. LVMI requires more thorough studies to consider it as a risk stratification tool in patients with HCM.

Thin and hypokinetic myocardial segments in cats with cardiomyopathy

INTRODUCTION/OBJECTIVES

Thin and hypokinetic myocardial segments (THyMS) represent adverse ventricular (LV) remodeling in human hypertrophic cardiomyopathy. We describe the echocardiographic features and outcome in cats with THyMS, and in a subpopulation, the echocardiographic phenotype before LV wall thinning was detected (pre-THyMS).

ANIMALS

Eighty client-owned cats.

MATERIALS AND METHODS

Retrospective multicenter study. Clinical records were searched for cats with THyMS, defined as LV segment(s) with end-diastolic wall thickness (LVWT) <3 mm and hypokinesis in the presence of ≥one LV segment(s) with LVWT >4 mm and normal wall motion. When available, echocardiograms pre-THyMS were assessed. Survival time was defined as time from first presentation with THyMS to death.

RESULTS

Mean thickest LV wall segment (MaxLVWT) was 6.1 mm (95% CI 5.8-6.4 mm) and thinnest (MinLVWT) was 1.7 mm (95% CI 1.6-1.9 mm). The LV free wall was affected in 74%, apex in 13% and septum in 5%. Most cats (85%) presented with heart failure and/or arterial thromboembolism. Median circulating troponin I concentration was 1.4 ng/mL ([range 0.07-180 ng/mL]). Prior echocardiography results were available for 13/80 cats, a mean of 2.5 years pre-THyMS. In segments subsequently undergoing thinning, initial MaxLVWT measured 6.7 mm (95% CI 5.8-7.7 mm) vs. 1.9 mm (95% CI 1.5-2.4 mm) at last echocardiogram (P<0.0001). Survival data were available for 56/80 cats, median survival time after diagnosing THyMS was 153 days (95% CI 83-223 days). Cardiac histopathology in one cat revealed that THyMS was associated with severe transmural scarring.

CONCLUSIONS

Cats with THyMS had advanced cardiomyopathy and a poor prognosis.

Cardiac Multimodality Imaging in Hypertrophic Cardiomyopathy: What to Look for and When to Image

Hypertrophic cardiomyopathy (HCM), now recognized as a common cardiomyopathy of complex genomics and pathophysiology, is defined by the presence of left ventricular hypertrophy of various morphologies and severity, significant hemodynamic consequences, and diverse phenotypic, both structural and clinical, profiles. Advancements in cardiac multimodality imaging, including echocardiography, cardiac magnetic resonance imaging, and cardiac computed tomography, with and without angiography have greatly improved the diagnosis of HCM, and enable precise measurements of cardiac mass, volume, wall thickness, function, and physiology. Multimodality imaging provides comprehensive and complementary information and hasemerged as the bedrock for the diagnosis, clinical assessment, serial monitoring, and sudden cardiac death risk stratification of patients with HCM. This review highlights the role of cardiac multimodality imaging in the modern diagnosis and management of HCM.

Catheter Ablation for Ventricular Arrhythmias in Hypertrophic Cardiomyopathy

Implantable cardioverter-defibrillators are the mainstay of therapy for prevention of sudden cardiac death in high-risk patients with hypertrophic cardiomyopathy (HCM). Catheter ablation is a useful option for patients with recurrent, drug refractory monomorphic ventricular tachycardia (VT), and device therapy. Compared with other nonischemic substrates, there are limited data on the role and outcomes of catheter ablation in HCM. The challenges of VT ablation in HCM patients include deep intramural and epicardial substrates, suboptimal power delivery, and higher recurrence due to progression of disease. Patient selection, using cardiac MRI scar localization, and optimizing ablation techniques can improve outcomes in these patients.

Role of cardiac magnetic resonance (CMR) in planning ventricular septal myomectomy in patients with hypertrophic obstructive cardiomyopathy (HOCM)

Septal myectomy is currently the gold standard treatment for symptomatic patients with hypertrophic obstructive cardiomyopathy (HOCM). The procedure needs to be tailored and performed in a personalized fashion, taking into consideration the anatomic and physiologic heterogeneity of this disease. The extent and location of surgical myectomy will depend on the location of the hypertrophy, with the goal of widening the outflow tract and improve the function of the mitral valve. CMR helps to identify hypertrophy not well visualized by TTE, providing more accurate wall thickness measurements and differentiating HOCM from other causes of LV hypertrophy. CMR also helps identify an abnormal attachment of papillary muscle to the MV or to the septal myocardium and mitral valve pathology. A collaborative approach with cardiac surgeons, radiologists and cardiologists will optimize preoperative planning to improve the success for surgical myectomy.

Energy Metabolism on Mitochondrial Maturation and Its Effects on Cardiomyocyte Cell Fate

Alterations in energy metabolism play a major role in the lineage of cardiomyocytes, such as the dramatic changes that occur in the transition from neonate to newborn. As cardiomyocytes mature, they shift from a primarily glycolytic state to a mitochondrial oxidative metabolic state. Metabolic intermediates and metabolites may have epigenetic and transcriptional roles in controlling cell fate by increasing mitochondrial biogenesis. In the maturing cardiomyocyte, such as in the postnatal heart, fatty acid oxidation increases in conjunction with increased mitochondrial biogenesis driven by the transcriptional coregulator PGC1-α. PGC1-α is necessary for mitochondrial biogenesis in the heart at birth, with deficiencies leading to postnatal cardiomyopathy. While stem cell therapy as a treatment for heart failure requires further investigation, studies suggest that adult stem cells may secrete cardioprotective factors which may regulate cardiomyocyte differentiation and survival. This review will discuss how metabolism influences mitochondrial biogenesis and how mitochondrial biogenesis influences cell fate, particularly in the context of the developing cardiomyocyte. The implications of energy metabolism on stem cell differentiation into cardiomyocytes and how this may be utilized as a therapy against heart failure and cardiovascular disease will also be discussed.

Society for Cardiovascular Magnetic Resonance 2021 cases of SCMR and COVID-19 case collection series

The Society for Cardiovascular Magnetic Resonance (SCMR) is an international society focused on the research, education, and clinical application of cardiovascular magnetic resonance (CMR). "Cases of SCMR" is a case series hosted on the SCMR website ( https://www.scmr.org ) that demonstrates the utility and importance of CMR in the clinical diagnosis and management of cardiovascular disease. The COVID-19 Case Collection highlights the impact of coronavirus disease 2019 (COVID-19) on the heart as demonstrated on CMR. Each case in series consists of the clinical presentation and the role of CMR in diagnosis and guiding clinical management. The cases are all instructive and helpful in the approach to patient management. We present a digital archive of the 2021 Cases of SCMR and the 2020 and 2021 COVID-19 Case Collection series of nine cases as a means of further enhancing the education of those interested in CMR and as a means of more readily identifying these cases using a PubMed or similar literature search engine.

Comparison of Nonclassic and Classic Phenotype of Hypertrophic Cardiomyopathy Focused on Prognostic Cardiac Magnetic Resonance Parameters: A Single-Center Observational Study

Patients with nonclassic phenotypes (NCP)—more advanced stages of hypertrophic cardiomyopathy (HCM)—constitute an intriguing and heterogeneous group that is difficult to diagnose, risk-stratify, and treat, and often neglected in research projects. We aimed to compare cardiac magnetic resonance (CMR) parameters in NCP versus classic phenotypes (CP) of HCM with special emphasis given to the parameters of established and potential prognostic importance, including numerous variables not used in everyday clinical practice. The CMR studies of 88 patients performed from 2011 to 2019 were postprocessed according to the study protocol to obtain standard and non-standard parameters. In NCP, the late gadolinium enhancement extent expressed as percent of left ventricular mass (%LGE) and left ventricular mass index (LVMI) were higher, left atrium emptying fraction (LAEF) was lower, minimal left atrial volume (LAV min) was greater, and myocardial contraction fraction (MCF) and left ventricular global function index (LVGFI) were lower than in CP (p < 0.001 for all). In contrast, HCM risk score and left ventricular maximal thickness (LVMT) were similar in NCP and CP patients. No left ventricular outflow tract obstruction (LVOTO) was observed in the NCP group. Left ventricular outflow tract diameter (LVOT), aortic valve diameter (Ao), and LVOT/Ao ratio were significantly higher and anterior mitral leaflet (AML)/LVOT ratio was lower in the NCP compared to the CP group. In conclusion, significant differences in nonstandard CMR parameters were noted between the nonclassic and classic HCM phenotypes that may contribute to future studies on disease stages and risk stratification in HCM.

Long-Lasting Myocardial and Skeletal Muscle Damage Evidenced by Serial CMR During the First Year in COVID-19 Patients From the First Wave

Introduction

This observational CMR study aims to characterize left-ventricular (LV) damage, which may be specifically attributed to COVID-19 and is distant in time from the acute phase, through serial CMR performed during the first year in patients with no prior cardiac disease.

Methods

This study included consecutive patients without any prior history of cardiac disease but with a peak troponin-Ic &gt; 50 ng/ml at the time of the first COVID-wave. All had a CMR in the first months after the acute phase, and some had an additional CMR at the end of the first year to monitor LV function, remodeling, and abnormalities evocative of myositis and myocarditis - i.e., increased T1/T2 relaxation times, increased extracellular volume (ECV), and delayed contrast enhancement.

Results

Nineteen consecutively admitted COVID-19 patients (17 men, median age 66 [57–71] years) were included. Eight (42%) had hypertension, six (32%) were obese, and 16 (84%) had suffered an acute respiratory distress syndrome. The 1st CMR, recorded at a median 3.2 [interquartile range: 2.6–3.9] months from the troponin peak, showed (1) LV concentric remodeling in 12 patients (63%), (2) myocardial tissue abnormalities in 11 (58%), including 9 increased myocardial ECVs, and (3) 14 (74%) increased ECVs from shoulder skeletal muscles. The 2nd CMR, obtained at 11.1 [11.0–11.7] months from the troponin peak in 13 patients, showed unchanged LV function and remodeling but a return to normal or below the normal range for all ECVs of the myocardium and skeletal muscles.

Conclusion

Many patients with no history of cardiac disease but for whom an increase in blood troponin-Ic ascertained COVID-19 induced myocardial damage exhibited signs of persistent extracellular edema at a median 3-months from the troponin peak, affecting the myocardium and skeletal muscles, which resolved within a one-year time frame. Associations with long-COVID symptoms need to be investigated on a larger scale now.

Clinical Trial Registration

NCT04753762 on the ClinicalTrials.gov site.

Anatomical-MRI Correlations in Adults and Children with Hypertrophic Cardiomyopathy

Hypertrophic Cardiomyopathy (HCM) is the most frequent hereditary cardiovascular disease and the leading cause of sudden cardiac death in young individuals. Advancements in CMR imaging have allowed for earlier identification and more accurate prognosis of HCM. Interventions aimed at slowing or stopping the disease's natural course may be developed in the future. CMR has been validated as a technique with high sensitivity and specificity, very few contraindications, a low risk of side effects, and is overall a good tool to be employed in the management of HCM patients. The goal of this review is to evaluate the magnetic resonance features of HCM, starting with distinct phenotypic variants of the disease and progressing to differential diagnoses of athlete's heart, hypertension, and infiltrative cardiomyopathies. HCM in children has its own section in this review, with possible risk factors that are distinct from those in adults; delayed enhancement in children may play a role in risk stratification in HCM. Finally, a number of teaching points for general cardiologists who recommend CMR for patients with HCM will be presented.

Subclinical Hypertrophic Cardiomyopathy in Elite Athletes: Knowledge Gaps Persist

Subclinical hypertrophic cardiomyopathy (HCM) is a phenotypic entity that has emerged from the increased use of cardiovascular magnetic resonance imaging in the evaluation and family screening of patients with HCM. We describe the case of a competitive athlete with a sarcomere gene mutation and family history of HCM who was found to exhibit the subclinical HCM phenotype on cardiovascular magnetic resonance imaging in the absence of left ventricular hypertrophy. We discuss the clinical uncertainties in her management. (Level of Difficulty: Advanced.).

Cardiac magnetic resonance in the assessment of hypertrophic cardiomyopathy phenotypes and stages - pictorial review

The aim of this paper is to present recent advances in hypertrophic cardiomyopathy (HCM) diagnosis and treatment based on a literature review. Special emphasis has been placed on the role of cardiac magnetic resonance imaging (CMR) for the assessment of morphological and functional consequences of different stages of HCM including prognostication. The text is illustrated with the images and data of the HCM patients diagnosed with CMR study in our hospital. CMR is an important tool, particularly relevant in novel risk factors and LV dysfunction groups. The HCM group with overt left ventricular dysfunction is underrecognized, often labelled by clinicians as dilated cardiomyopathy. Advanced diagnostic and management strategies effectively influence the natural history of HCM.

Cardiovascular magnetic resonance detects microvascular dysfunction in a mouse model of hypertrophic cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) related myocardial vascular remodelling may lead to the reduction of myocardial blood supply and a subsequent progressive loss of cardiac function. This process has been difficult to observe and thus their connection remains unclear. Here we used non-invasive myocardial blood flow sensitive CMR to show an impairment of resting myocardial perfusion in a mouse model of naturally occurring HCM.

METHODS

We used a mouse model (DBA/2 J; D2 mouse strain) that spontaneously carries variants in the two most susceptible HCM genes-Mybpc3 and Myh7 and bears the key features of human HCM. The C57BL/6 J (B6) was used as a reference strain. Mice with either B6 or D2 backgrounds (male: n = 4, female: n = 4) underwent cine-CMR for functional assessment at 9.4 T. Left ventricular (LV) wall thickness was measured in end diastolic phase by cine-CMR. Quantitative myocardial perfusion maps (male: n = 5, female: n = 5 in each group) were acquired from arterial spin labelling (cine ASL-CMR) at rest. Myocardial perfusion values were measured by delineating different regions of interest based on the LV segmentation model in the mid ventricle of the LV myocardium. Directly after the CMR, the mouse hearts were removed for histological assessments to confirm the incidence of myocardial interstitial fibrosis (n = 8 in each group) and small vessel remodelling such as vessel density (n = 6 in each group) and perivascular fibrosis (n = 8 in each group).

RESULTS

LV hypertrophy was more pronounced in D2 than in B6 mice (male: D2 LV wall thickness = 1.3 ± 0.1 mm vs B6 LV wall thickness = 1.0 ± 0.0 mm, p < 0.001; female: D2 LV wall thickness = 1.0 ± 0.1 mm vs B6 LV wall thickness = 0.8 ± 0.1 mm, p < 0.01). The resting global myocardial perfusion (myocardial blood flow; MBF) was lower in D2 than in B6 mice (end-diastole: D2 MBFglobal = 7.5 ± 0.6 vs B6 MBFglobal = 9.3 ± 1.6 ml/g/min, p < 0.05; end-systole: D2 MBFglobal = 6.6 ± 0.8 vs B6 MBFglobal = 8.2 ± 2.6 ml/g/min, p < 0.01). This myocardial microvascular dysfunction was observed and associated with a reduction in regional MBF, mainly in the interventricular septal and inferior areas of the myocardium. Immunofluorescence revealed a lower number of vessel densities in D2 than in B6 (D2 capillary = 31.0 ± 3.8% vs B6 capillary = 40.7 ± 4.6%, p < 0.05). Myocardial collagen volume fraction (CVF) was significantly higher in D2 LV versus B6 LV mice (D2 CVF = 3.7 ± 1.4% vs B6 CVF = 1.7 ± 0.7%, p < 0.01). Furthermore, a higher ratio of perivascular fibrosis (PFR) was found in D2 than in B6 mice (D2 PFR = 2.3 ± 1.0%, B6 PFR = 0.8 ± 0.4%, p < 0.01).

CONCLUSIONS

Our work describes an imaging marker using cine ASL-CMR with a potential to monitor vascular and myocardial remodelling in HCM.

Relation of atrial electromechanical delay to P-wave dispersion on surface ECG using vector velocity imaging in patients with hypertrophic cardiomyopathy

OBJECTIVES

Heterogeneity of structural and electrophysiologic properties of atrial myocardium is common characteristic in hypertrophic cardiomyopathy (HCM). We assessed the dispersion of atrial refractoriness on surface ECG using P-wave dispersion (PWD) and its relation to atrial electromechanical functions using vector velocity imaging (VVI) in HCM population.

METHODS

Seventy-nine HCM patients (mean age: 43.7 ± 13 years, 67% male) were compared with 25 healthy individuals as control. P-wave durations, Pmax and Pmin , P-wave dispersion (PWD), and P terminal force (PTF) were measured from 12-lead ECG. LA segmental delay (TTP-d) and dispersion (TTP-SD) of electromechanical activation were derived from atrial strain rate curves.

RESULTS

HCM patients had longer PR interval, PW duration, higher PWD, PTF, QTc compared to control (p < .001). HCM patients were classified according to presence of PWD into two groups, group I with PWD > 46 ms (n = 25) and group II PWD ≤ 46 ms (n = 54). Group I showed higher prevalence of female gender, higher PTF, QTc interval, left ventricular outflow tract (LVOT) obstruction, p < .01, LVOT gradient (p < .001), LV mass index (p < .01), E/E' (p < .01), and severe mitral regurgitation (p < .001). Moreover, PWD was associated with increased atrial electromechanical delay (TTP-d) and LA mechanical dyssynchrony (TTP-SD), p < .001. LA segmental delay and dispersion of electromechanical activation were distinctly higher among HCM patient.

CONCLUSION

PWD is simple ECG criterion, and it is associated with more severe HCM phenotype and LA electromechanical delay while PTF is linked only to atrial remodeling.

Cardiac magnetic resonance in hypertrophic and dilated cardiomyopathies

Cardiomyopathies are a heterogeneous entity. The progress in the field of genetics has allowed over the years to determine its origin more and more often. The classification of these pathologies has changed over the years; it has been updated with new knowledge. Imaging allows to define the phenotypic characteristics of the different forms of cardiomyopathy. Cardiac magnetic resonance (CMR) allows a morphological evaluation of the associated (and sometimes pathognomonic) cardiac findings of any form of cardiomyopathy. The tissue characterization sequences also make magnetic resonance imaging unique in its ability to detect changes in myocardial tissue. This review aims to define the features that can be highlighted by CMR in hypertrophic and dilated forms and the possible differential diagnoses. In hypertrophic forms, CMR provides: precise evaluation of wall thickness in all segments, ventricular function and size and evaluation of possible presence of areas of fibrosis as well as changes in myocardial tissue (measurement of T1 mapping and extracellular volume values). In dilated forms, cardiac resonance is the gold standard in the assessment of ventricular volumes. CMR highlights also the potential alterations of the myocardial tissue.

The role of echocardiography for diagnosis and prognostic stratification in hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most frequent cardiac disease with genetic substrate, affecting about 0.2-0.5% of the population. While most of the patients with HCM have a relatively good prognosis, some are at increased risk of adverse events. Identifying such patients at risk is important for optimal treatment and follow-up. While clinical and electrocardiographic information plays an important role, echocardiography remains the cornerstone in assessing patients with HCM. In this review, we discuss the role of echocardiography in diagnosing HCM, the key features that differentiate HCM from other diseases and the use of echocardiography for risk stratification in this setting (risk of sudden cardiac death, heart failure, atrial fibrillation and stroke). The use of modern echocardiographic techniques (deformation imaging, 3D echocardiography) refines the diagnosis and prognostic assessment of patients with HCM. The echocardiographic data need to be integrated with clinical data and other information, including cardiac magnetic resonance, especially in challenging cases or when there is incomplete information, for the optimal management of these patients.

Protein Thermodynamic Destabilization in the Assessment of Pathogenicity of a Variant of Uncertain Significance in Cardiac Myosin Binding Protein C

In the era of next generation sequencing (NGS), genetic testing for inherited disorders identifies an ever-increasing number of variants whose pathogenicity remains unclear. These variants of uncertain significance (VUS) limit the reach of genetic testing in clinical practice. The VUS for hypertrophic cardiomyopathy (HCM), the most common familial heart disease, constitute over 60% of entries for missense variants shown in ClinVar database. We have studied a novel VUS (c.1809T>G-p.I603M) in the most frequently mutated gene in HCM, MYBPC3, which codes for cardiac myosin-binding protein C (cMyBPC). Our determinations of pathogenicity integrate bioinformatics evaluation and functional studies of RNA splicing and protein thermodynamic stability. In silico prediction and mRNA analysis indicated no alteration of RNA splicing induced by the variant. At the protein level, the p.I603M mutation maps to the C4 domain of cMyBPC. Although the mutation does not perturb much the overall structure of the C4 domain, the stability of C4 I603M is severely compromised as detected by circular dichroism and differential scanning calorimetry experiments. Taking into account the highly destabilizing effect of the mutation in the structure of C4, we propose reclassification of variant p.I603M as likely pathogenic. Looking into the future, the workflow described here can be used to refine the assignment of pathogenicity of variants of uncertain significance in MYBPC3.