Hypertrophic Cardiomyopathy from A to Z: Genetics, Pathophysiology, Imaging, and Management

Assessing right ventricular deformation in hypertrophic cardiomyopathy patients with preserved right ventricular ejection fraction: a 3.0-T cardiovascular magnetic resonance study

To assess the global and regional right ventricular (RV) deformation in hypertrophic cardiomyopathy (HCM) patients with preserved right ventricular ejection fraction (RVEF) using 3.0-T cardiovascular magnetic resonance tissue tracking (CMR-TT). Eighty-two HCM patients and 32 age- and sex-matched healthy controls were enrolled. HCM patients were divided into groups depending on the presence or absence of right ventricular hypertrophy (RVH), RV late gadolinium enhancement (RV-LGE), and left ventricular outflow tract obstruction (LVOTO), respectively. The RV global and apical longitudinal peak strain (LPS) in HCM patients with RVH were significantly lower than that in HCM patients without RVH and controls (P < 0.05). The global, apical and mid-ventricular LPS in HCM patients with RV-LGE were significantly lower than that in HCM patients without RV-LGE and controls (P < 0.05). Lower LPS was demonstrated in HCM patients without RV-LGE compared with controls in apical and mid-ventricular levels (P < 0.05). No significant difference was found regarding global and regional LPS in HCM patients with LVOTO compared without LVOTO (all P > 0.05). CMR-TT was able to detect subclinical RV myocardial deformation prior to RVEF impairment, which was more severe in the presence of RVH and RV-LGE.

Exome sequencing identifies a FHOD3 p.S527del mutation in a Chinese family with hypertrophic cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is the most common inheritable cardiac disease and is characterised by unexplained ventricular myocardial hypertrophy. HCM is highly heterogeneous and is primarily caused by the mutation of genes encoding sarcomere proteins. As a result of its genetic basis, we investigated the underlying cause of HCM in a Chinese family by whole-exome sequencing.

METHODS

Whole-exome sequencing was performed for seven clinically diagnosed HCM family members and the resulting single nucleotide variants associated with cardiac hypertrophy or heart development were analysed by a polymerase chain reaction and Sanger sequencing.

RESULTS

A non-frameshift deletion mutation (p.S527del) of Formin Homology 2 Domain Containing 3 (FHOD3) was detected in all of the affected family members and was absent in all unaffected members, with the exception of one young member. Moreover, three single nucleotide variants associated with heart development and morphogenesis were identified in the proband but were absent in the other affected subjects.

CONCLUSIONS

This is the first HCM family case of FHOD3 (p.S527del) variation in Asia. Additionally, RNF207 (p.Q268P), CCM2 (p. E233K) and SGCZ (p.Q134X) may be related to the clinical heterogeneity of the family. The present study could enable the provision of genetic counseling for this family and provide a basis for future genetic and functional studies.

Apical variant hypertrophic cardiomyopathy "multimodality imaging evaluation"

Apical variant hypertrophic cardiomyopathy (AHCM) is characterized by asymmetric hypertrophy of the left ventricular (LV) apex. T wave inversions of variable degree, particularly in the left precordial leads, and left ventricular hypertrophy (LVH) are common EKG findings in AHCM. Echocardiography is typically the initial imaging modality used in the diagnosis and evaluation of AHCM. The diagnosis is made when the LV apex has apical wall thickness of ≥ 15 mm or a ratio of apical to basal LV wall thickness of ≥ 1.3 at end-diastole. The use of microbubble contrast agents with echocardiography is helpful for visualization of the apex. Cardiac magnetic resonance (CMR) has the advantage of a large field of view and the ability to perform tissue characterization. Late gadolinium enhancement (LGE) sequences are essential in the assessment of potential areas of myocardial scarring. Cardiac computed tomography (CCT) has the advantage of being able to evaluate coronary arteries in addition to assessing cardiac anatomy and function. A "Solar Polar" map pattern is the characteristic feature of AHCM on myocardial perfusion imaging (MPI) in cases not associated with apical aneurysm (APA). Recognition of typical perfusion patterns in AHCM patients is not only important in the diagnostic evaluation of this disease process, but also for avoiding unnecessary and costly tests. The purpose of this article is to review the imaging features of AHCM from different imaging modalities and assess the value added of each modality in the diagnosis of AHCM.

Screening of MYH7 gene mutation sites in hypertrophic cardiomyopathy and its significance

BACKGROUND

There have been few reports of mutations in the beta-myosin heavy chain (MYH7) gene in hypertrophic cardiomyopathy (HCM), which is associated with sudden cardiac death caused by HCM. This study aimed to screen the mutation sites in the sarcomeric gene MYH7 in Chinese patients with HCM. We also planned to analyze the pathogenicity of the mutation site as well as its significance in clinical and forensic medicine.

METHODS

From January 2006 to June 2017, autopsy cases were collected from the Department of Pathology, the Affiliated Hospital of Qingdao University. The experiment was to detect MYH7 gene status in formalin-fixed paraffin-embedded tissues from 18 independent autopsy cases who suffered HCM related sudden death (fatal HCM) and 20 cases without cardiomyopathy. Common mutation exon fragments of MYH7 gene were amplified by polymerase chain reaction. The end-of-deoxygenation method and gene cloning method were further performed to analyze the mutation sites. Homologous comparison among mutant sites was conducted using BLAST online database.

RESULTS

The 1336th nucleotide of MYH7 gene at exon 14 was converted from T to G in one HCM case, resulting in the conversion of threonine (Thr) at position 446 to proline (Pro). In another case, the 1402th nucleotide at exon 14 was converted from T to C, resulting in the conversion of phenylalanine (Phe) at position 468 to leucine (Leu). Homologous comparison results showed that the two amino acid residues of Thr446 and Phe468 are highly conserved among different species.

CONCLUSIONS

Our results showed fatal HCM harbored mutations of Thr446Pro and Phe468Leu in the MYH7 gene. It is significant for clinical and forensic medicine to further explore the functions and detailed mechanisms of these mutations.

Assessment of ventricular tachyarrhythmia in patients with hypertrophic cardiomyopathy with machine learning-based texture analysis of late gadolinium enhancement cardiac MRI

OBJECTIVE

To assess the diagnostic value of machine learning-based texture feature analysis of late gadolinium enhancement images on cardiac magnetic resonance imaging (MRI) for assessing the presence of ventricular tachyarrhythmia (VT) in patients with hypertrophic cardiomyopathy.

MATERIALS AND METHODS

This retrospective study included 64 patients with hypertrophic cardiomyopathy who underwent cardiac MRI and 24-hour Holter monitoring within 1 year before cardiac MRI. There were 42 men and 22 women with a mean age of 48.13±13.06 (SD) years (range: 20-70 years). Quantitative textural features were extracted via manually placed regions of interest in areas with high and intermediate signal intensity on late gadolinium-chelate enhanced images. Feature selection and dimension reduction were performed. The diagnostic performances of machine learning classifiers including support vector machines, Naive Bayes, k-nearest-neighbors, and random forest for predicting the presence of VT were assessed using the results of 24-hour Holter monitoring as the reference test. All machine learning models were assessed with and without the application of the synthetic minority over-sampling technique (SMOTE).

RESULTS

Of the 64 patients with hypertrophic cardiomyopathy, 21/64 (32.8%) had VT. Of eight machine learning models investigated, k-nearest-neighbors with SMOTE exhibited the best diagnostic accuracy for the presence or absence of VT. k-nearest-neighbors with SMOTE correctly identified 40/42 (95.2%) VT-positive patients and 40/43 (93.0%) VT-negative patients, yielding 95.2% sensitivity (95% CI: 82.5%-99.1%), 93.0% specificity (95% CI: 79.8%-98.1%) and 94.1% accuracy (95% CI: 88.8%-98%).

CONCLUSION

Machine learning-based texture analysis of late gadolinium-chelate enhancement-positive areas is a promising tool for the classification of hypertrophic cardiomyopathy patients with and without VT.

MRI native T1 and T2 mapping of myocardial segments in hypertrophic cardiomyopathy: tissue remodeling manifested prior to structure changes

OBJECTIVE

The aim of this study was to examine the local myocardial segments in hypertrophic cardiomyopathy (HCM) by MRI T1 and T2 mapping, and to investigate how tissue remodeling correlates with structural and functional remodeling in HCM.

METHODS

47 patients with HCM and 19 healthy volunteers were enrolled in this study. All subjects underwent cardiac MRI at 3.0 T. Native T1 and T2 values, end-diastolic wall thickness (EDTH), and percentage of systolic wall thickening (PSWT) were assessed in the left ventricular segments according to the American Heart Association model. Myocardial segments were categorized as normal, non-hypertrophic, mild-hypertrophic, moderate-hypertrophic, and severe-hypertrophic based on EDTH. The difference among all five groups, and the correlation between native T1 and T2 values, EDTH, and PSWT were evaluated.

RESULTS

Native T1 and T2 values were significantly elevated in both non-hypertrophic and hypertrophic segments of HCM patients compared to controls (both p < 0.001). PSWT was preserved in non-hypertrophic segments (p = 0.838), while significantly impaired (p < 0.001) in hypertrophic segments. Native T1 value of severe hypertrophic segments in HCM was significantly higher than segments of mild and moderate hypertrophy (p < 0.05).

CONCLUSION

In HCM patients, the non-hypertrophic myocardial segments already demonstrated significantly elevated T1 and T2 values, despite normal wall thickness and preserved contraction function. The finding suggests that tissue remodeling may precede morphological and functional remodeling in HCM. MRI native T1 and T2 mapping can provide additional value for HCM diagnosis at an early stage.

ADVANCES IN KNOWLEDGE

Myocardial tissue remodeling, as detected by MRI native T1 and T2 mapping, occurs earlier than morphological and functional changes in HCM patients.

Exploring the Continuum of Hypertrophic Cardiomyopathy-From DNA to Clinical Expression

The concepts underlying hypertrophic cardiomyopathy (HCM) pathogenesis have evolved greatly over the last 60 years since the pioneering work of the British pathologist Donald Teare, presenting the autopsy findings of “asymmetric hypertrophy of the heart in young adults”. Advances in human genome analysis and cardiac imaging techniques have enriched our understanding of the complex architecture of the malady and shaped the way we perceive the illness continuum. Presently, HCM is acknowledged as “a disease of the sarcomere”, where the relationship between genotype and phenotype is not straightforward but subject to various genetic and nongenetic influences. The focus of this review is to discuss key aspects related to molecular mechanisms and imaging aspects that have prompted genotype–phenotype correlations, which will hopefully empower patient-tailored health interventions.

Phenotypes of hypertrophic cardiomyopathy. An illustrative review of MRI findings

Objective

The purpose of this article is to review how cardiac MRI provides the clinician with detailed information about the hypertrophic cardiomyopathy (HCM) phenotypes, assessing its morphological and functional consequences.

Conclusion

An understanding of cardiac MRI manifestations of HCM phenotypes will aid early diagnosis recognition and its functional consequences.

Teaching Points

• The phenotypic variability of HCM expands beyond myocardial hypertrophy, to include morphological and functional manifestations, ranging from subtle anomalies to remodelling of the LV with progressive dilatation and thinning of its wall.

• The stages of HCM, which are based on the clinical evidence of disease progression, include subclinical HCM, the classic HCM phenothype, adverse remodelling and overt dysfunction, or end-stage HCM.

• Cardiac MRI provides the clinician with detailed information regarding the HCM phenotypes and enables the assessment of its functional consequences.

Differential diagnosis of thickened myocardium: an illustrative MRI review

Objectives

The purpose of this article is to describe the key cardiac magnetic resonance imaging (MRI) features to differentiate hypertrophic cardiomyopathy (HCM) phenotypes from other causes of myocardial thickening that may mimic them.

Conclusions

Many causes of myocardial thickening may mimic different HCM phenotypes. The unique ability of cardiac MRI to facilitate tissue characterisation may help to establish the aetiology of myocardial thickening, which is essential to differentiate it from HCM phenotypes and for appropriate management.

Teaching points

• Many causes of myocardial thickening may mimic different HCM phenotypes.

• Differential diagnosis between myocardial thickening aetiology and HCM phenotypes may be challenging.

• Cardiac MRI is essential to differentiate the aetiology of myocardial thickening from HCM phenotypes.

Classifying Cardiac Actin Mutations Associated With Hypertrophic Cardiomyopathy

Mutations in the cardiac actin gene (ACTC1) are associated with the development of hypertrophic cardiomyopathy (HCM). To date, 12 different ACTC1 mutations have been discovered in patients with HCM. Given the high degree of sequence conservation of actin proteins and the range of protein–protein interactions actin participates in, mutations in cardiac actin leading to HCM are particularly interesting. Here, we suggest the classification of ACTC1 mutations based on the location of the resulting amino acid change in actin into three main groups: (1) those affecting only the binding site of the myosin molecular motor, termed M-class mutations, (2) those affecting only the binding site of the tropomyosin (Tm) regulatory protein, designated T-class mutations, and (3) those affecting both the myosin- and Tm-binding sites, called MT-class mutations. To understand the precise pathogenesis of cardiac actin mutations and develop treatments specific to the molecular cause of disease, we need to integrate rapidly growing structural information with studies of regulated actomyosin systems.

Homozygous missense MYBPC3 Pro873His mutation associated with increased risk for heart failure development in hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a primary autosomal‐dominant disorder of the myocardium with variable expressivity and penetrance. Occasionally, homozygous sarcomere genetic variants emerge while genotyping HCM patients. In these cases, a more severe HCM phenotype is generally seen. Here, we report a case of HCM that was diagnosed clinically at 39 years of age. Initial symptoms were shortness of breath during exertion. Successively, he developed a wide array of severe clinical manifestations, which progressed to an ominous end‐stage heart failure that resulted in heart transplantation. Genotype analysis revealed a missense MYBPC3 variant NM_000256.3:c.2618C>A,p.(Pro873His) that presented in the homozygous form. Conflicting interpretations of pathogenicity have been reported for the Pro873His MYBPC3 variant described here. Our patient, presenting with two copies of the variant and devoid of a normal allele, progressed to end‐stage heart failure, which supports the notion of a deleterious effect of this variant in the homozygous form.

Texture analysis and machine learning of non-contrast T1-weighted MR images in patients with hypertrophic cardiomyopathy-Preliminary results

PURPOSE

To test in a first proof-of-concept study whether texture analysis (TA) allows for the detection of myocardial tissue alterations in hypertrophic cardiomyopathy (HCM) on non-contrast T1-weighted cardiac magnetic resonance (CMR) images using machine learning based approaches.

METHODS

This retrospective, IRB-approved study included 32 patients with known HCM. Thirty patients with normal CMR served as controls. Regions-of-interest for TA encompassing the left ventricle were drawn on short-axis non-contrast T1-weighted images using a freely available software package. Step-wise dimension reduction and texture feature selection was performed for selecting features enabling the detection of myocardial tissue alterations in HCM patients on non-contrast T1-weighted CMR images.

RESULTS

Comparing HCM patients and controls, four texture features were identified showing significant differences between groups (Grey-level Non-uniformity [GLevNonU]: 74 ± 17 vs. 38 ± 9, p < .001; Energy of wavelet coefficients in low-frequency sub-bands [WavEnLL]: 58 ± 5 vs. 48 ± 10, p < .001; Fraction: 0.70 ± 0.07 vs. 0.78 ± 0.05, p < .001; Sum Average: 16.6 ± 0.4 vs. 17.0 ± 0.5, p = .007). A model containing the single parameter GLevNonU proved to be the best for differentiating between HCM patients and controls with a sensitivity/specificity of 91%/93%. A cut-off of GLevNonU ≥46 allowed for distinguishing HCM patients from controls with a sensitivity/specificity of 94%/90%. Even in patients without late gadolinium enhancement (LGE), the defined cut-off led to a differentiation of LGE- patients from healthy controls with 100% sensitivity and 90% specificity.

CONCLUSIONS

TA on non-contrast T1-weighted images allows for the detection of myocardial tissue alterations in the setting of HCM with excellent accuracy, delivering potential novel parameters for a non-contrast assessment of myocardial texture alterations.

NEXT GENERATION SEQUENCING HELPS IN DIFFERENTIAL DIAGNOSIS OF PATHOLOGICAL LEFT VENTRICULAR HYPERTROPHY IN ELITE ATHLETES

To detect the reason of left ventricular hypertrophy (LVH) may be difficult in some cases especially in elite athletes. Object. To evaluate the efficiency of next generation sequencing (NGS) genetic test in differential diagnostics of pathological LVH in elite athletes. Material and methods. Analysis of echocardiographic data from 791 elite athletes revealed 15 individuals with LVH > 12 mm (1,9%). Based on the criteria of abnormality (asymmetric, severe and changes on electrocardiogram) 5 (0,6%) athletes were selected for genetic test. TruSight Cardio panel (“Illumina”) was used to identify variants of 174 genes with known associations to inherited cardiac conditions. Results. In 3 out of 5 athletes the pathogenic variants in MBPC3 and LMNA genes previously associated with HCM and other CMs were found. One athlete with negative genetic test result had severe untreated arterial hypertension as a possible cause for LVH. The second athlete didn’t have LVH in magnetic resonance imaging. Conclusions. In elite athletes, the asymmetric LVH should be considered as pathological finding which requires comprehensive clinical evaluation and NGS genetic test.

Detection of concentric left ventricular wall hypertrophy by contrast-enhanced non-electrocardiogram-gated chest computed tomography

BACKGROUND

No established measure of concentric left ventricular wall hypertrophy (cLVH) on routine computed tomography (CT) of the adult chest currently exists. The objective of this study was to identify and test linear measures for the detection of cLVH using transthoracic echocardiography (TTE) as the reference standard.

METHODS

Contrast-enhanced non-electrocardiogram-gated chest CTs acquired within two weeks of TTE were retrospectively evaluated. Two radiologists independently made trans-axial measurements in the proximal half of the left ventricle at its approximate widest internal diameter: maximum septal thickness (sept), maximum lateral wall thickness (lat), and inner (I_d) and outer (O_d) wall-wall diameters at the level of greatest combined myocardial thickness. The sum of sept and lat, hereafter Th_max, and modified cross-sectional area (A_mod = O_d² - I_d²) were calculated. Sept, lat, Th_max, and A_mod were evaluated by receiver operating characteristic (ROC) curves using TTE as the reference standard. Thresholds were optimized for specificity and applied to a validation cohort. Inter-rater agreement was assessed by a simple unweighted Kappa statistic (κ).

RESULTS

Sept and A_mod were selected based on areas under the ROC curves of 0.75 and 0.71, respectively, using 100 CTs. Thresholds of 1.6 cm and 30 cm², respectively, showed similar specificities of 98% with sensitivities of 27% and 30%, respectively. Applied to a validation cohort of 100 CTs, sept had higher combined positive predictive value (75%), inter-rater agreement (κ = 0.58), specificity (91%), and sensitivity (24%).

CONCLUSION

Linear measures demonstrate utility in the diagnosis of cLVH on routine contrast-enhanced chest CT.

Early marker of regional left ventricular deformation in patients with hypertrophic cardiomyopathy evaluated by MRI tissue tracking: The effects of myocardial hypertrophy and fibrosis

PURPOSE

To evaluate the regional left ventricular (LV) myocardial strain of early stage hypertrophic cardiomyopathy (HCM) patients by magnetic resonance (MR) tissue tracking.

MATERIALS AND METHODS

In all, 114 adult HCM patients classified as NYHA I or II and 32 healthy volunteers were enrolled and underwent 3.0T MR examination. Vertical 2-chamber long axis, horizontal 4-chamber, and short axis cine sequence as well as late gadolinium enhancement images (LGE) were scanned. The cardiac function, regional LV tissue tracking variables, end-diastolic wall thickness (EDTH), and LGE extent were measured.

RESULTS

In the HCM group, 38 were NYHA I and 76 were NYHA II. By regional analysis, peak strain (PS) and peak displacement (PD) with radial, circumferential direction of hypertrophic segments (n = 283) were significantly lower than nonhypertrophic segments (n = 1541) (all P < 0.05). Radial PS was significantly correlated with LVEDTH (r = -0.467, P < 0.0001). Radial PD was negatively associated with LVEDTH (r = -0.331, P < 0.0001). The PS and PD of all directions were decreased in segments with LGE (n = 723) compared with those without LGE (n = 1101) (all P < 0.05). In addition, radial PS and PD were negatively associated with LGE extent (radial PS, r = -0.441; radial PD, r = -0.274; both P < 0.0001). All strain parameters showed excellent inter- and intraobserver agreements.

CONCLUSION

Decreased regional LV myocardial strain hypertrophic and fibrotic segments of early-stage HCM patients can be measured by MR tissue tracking based on routine cine images. Moreover, myocardial strain may decrease with the increasing of myocardial hypertrophy as well as fibrosis.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2017;46:1368-1376.