Familial hypertrophic cardiomyopathy. Cardiac ultrasonic abnormalities in genetically affected subjects without echocardiographic evidence of left ventricular hypertrophy

Histopathology of the Mitral Valve Residual Leaflet in Obstructive Hypertrophic Cardiomyopathy

BACKGROUND

Mitral valve (MV) elongation is a primary hypertrophic cardiomyopathy (HCM) phenotype and contributes to obstruction. The residual MV leaflet that protrudes past the coaptation point is especially susceptible to flow-drag and systolic anterior motion. Histopathological features of MVs in obstructive hypertrophic cardiomyopathy (OHCM), and of residual leaflets specifically, are unknown.

OBJECTIVES

The purpose of this study was to characterize gross, structural, and cellular histopathologic features of MV residual leaflets in OHCM. On a cellular-level, we assessed for developmental dysregulation of epicardium-derived cell (EPDC) differentiation, adaptive endocardial-to-mesenchymal transition and valvular interstitial cell proliferation, and genetically-driven persistence of cardiomyocytes in the valve.

METHODS

Structural and immunohistochemical staining were performed on 22 residual leaflets excised as ancillary procedures during myectomy, and compared with 11 control leaflets from deceased patients with normal hearts. Structural components were assessed with hematoxylin and eosin, trichrome, and elastic stains. We stained for EPDCs, EPDC paracrine signaling, valvular interstitial cells, endocardial-to-mesenchymal transition, and cardiomyocytes.

RESULTS

The residual leaflet was always at A2 segment and attached by slack, elongated and curlicued, myxoid chords. MV residual leaflets in OHCM were structurally disorganized, with expanded spongiosa and increased, fragmented elastic fibers compared with control leading edges. The internal collagenous fibrosa was attenuated and there was collagenous tissue overlying valve surfaces in HCM, with an overall trend toward decreased leaflet thickness (1.09 vs 1.47 mm, P = 0.08). No markers of primary cellular processes were identified.

CONCLUSIONS

MV residual leaflets in HCM were characterized by histologic findings that were likely secondary to chronic hemodynamic stress and may further increase susceptibility to systolic anterior motion.

Behind Enemy Lines: Vital Echocardiographic Data Prior to Ventricular Arrhythmia Ablation

Ventricular arrhythmias (VA) are a major cause of sudden cardiac death (SCD). Echocardiography is the first widely available imaging tool which guides VA management strategies. Along with other invasive and noninvasive imaging techniques, it provides essential information for identification of VA substrate such as differentiation between ischemic and non-ischemic etiology and identification of structural heart disease. Both classic as well as novel echocardiographic techniques such as left ventricular strain measurement and mechanical dispersion assessment provide prognostic information and assist in risk stratification. Furthermore, intracardiac echocardiography may have an adjunctive role for the VA ablation by providing real-time visualization of cardiac structures, continuous monitoring of catheter location and early recognition of procedural complications. This review gathers all relevant information that echocardiography may offer prior to VA ablation procedures.

Intrinsic mitral valve alterations in hypertrophic cardiomyopathy sarcomere mutation carriers

Aims

Mitral valve (MV) abnormalities are recognized features of hypertrophic cardiomyopathy (HCM), and there is preliminary evidence suggesting they are intrinsic phenotypic manifestations of sarcomere mutations, present in mutation carriers without left ventricular (LV) hypertrophy (subclinical HCM). However, further study is required to characterize the nature of these changes and their functional impact. Thus, we performed comprehensive echocardiographic analysis of MV structure and function on a genotyped population.

Methods and results

MV and papillary muscle echocardiographic parameters were measured in 192 genotyped individuals, including 50 overt HCM, 79 subclinical HCM, and 63 mutation-negative, healthy relatives as normal controls. Compared to controls, subclinical HCM subjects had elongated anterior MV leaflets relative to LV end-diastolic volume index (0.57 ± 0.02 vs. 0.51 ± 0.02 mm/mL/m2, P = 0.013) and anteriorly displaced papillary muscles [decreased papillary-septal separation (31.1 ± 0.7 vs. 34.2 ± 0.9 mm, P = 0.004) and relative antero-posterior position ratio of the papillary muscles (0.67 ± 0.01 vs. 0.71 ± 0.01, P = 0.011]. Similar findings were identified comparing overt HCM to controls. These MV changes were associated with an increased prevalence of systolic anterior motion (SAM) of the MV amongst subclinical HCM subjects.

Conclusions

Sarcomere mutations are associated with primary abnormalities of the MV apparatus, specifically excess anterior leaflet length relative to LV cavity size and anterior displacement of the papillary muscles; both features predisposing to SAM. These abnormalities appear to be early phenotypic consequences of sarcomere mutations, observed in mutation carriers with normal LV wall thickness.

Galectin-3: A Novel Biomarker Predicts Sudden Cardiac Death in Hypertrophic Cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy is a primary cardiac disease characterized by left ventricular hypertrophy, myocyte hypertrophy and irregularities and interstitial fibrosis in the absence of any cardiac or systemic diseases and may lead to sudden cardiac death (SCD). Galectin-3 is a β-galactoside-binding lectin that has been associated with cardiac fibrosis and inflammation. In this study, we aimed to investigate the relationship between serum galectin-3 levels and the criteria for 5-year sudden death risk, recently defined in the European Society of Cardiology guidelines (2014), in patients with hypertrophic cardiomyopathy.

MATERIALS AND METHODS

A total of 52 hypertrophic cardiomyopathy patients were enrolled in the study. Patients were questioned for sudden death risk predictors as outlined in the 2014 European Society of Cardiology guideline. A standardized clinical evaluation was carried out on the basis of previously described prognostic variables to calculate the 5-year risk of SCD. Blood samples were taken from all patients to measure serum galectin-3 levels. A statistical significance level of P < 0.05 was accepted in all tests.

RESULTS

We found that there was a significant correlation between the estimated 5-year risk of SCD and serum levels of galectin-3.

CONCLUSIONS

Galectin-3 may be an inexpensive and easily accessible parameter to predict arrhythmia risk. In addition, it can be used to determine antiarrhythmic prophylaxis as a predictor of an arrhythmia storm in implantable cardioverter defibrillator-implanted patients who are not available for magnetic resonance imaging.

Wolff-Parkinson-White Syndrome with Ventricular Hypertrophy in a Brazilian Family

BACKGROUND PRKAG2 syndrome diagnosis is already well-defined as Wolff-Parkinson-White syndrome (WPW), ventricular hypertrophy (VH) due to glycogen accumulation, and conduction system disease (CSD). Because of its rarity, there is a lack of literature focused on the treatment. The present study aimed to describe appropriate strategies for the treatment of affected family members with PRKAG2 syndrome with a long follow-up period. CASE REPORT We studied 60 selected individuals from 84 family members (32 males, 53.3%) (mean age 27±16 years). Patients with WPW and/or VH were placed in a group of 18 individuals, in which 11 (61.1%) had VH and WPW, 6 (33.3%) had isolated WPW, and 1 (5.6%) had isolated VH. Palpitations occurred in 16 patients (88.9%), chest pain in 11 (61.1%), dizziness in 13 (72.2%), syncope in 15 (83.3%), and dyspnea in 13 (72%). Sudden cardiac death (SCD) occurred in 2 (11.1%), and 2 patients with cardiac arrest (CA) had asystole and pre-excited atrial flutter-fibrillation (AFL and AF) as the documented mechanism. Transient ischemic attack (TIA) and learning/language disabilities with delayed development were observed. Genetic analysis identified a new missense pathogenic variant (p.K290I) in the PRKAG2 gene. Cardiac histopathology demonstrated the predominance of vacuoles containing glycogen derivative and fibrosis. The treatment was based on hypertension and diabetes mellitus (DM) control, antiarrhythmic drugs (AD), anticoagulation, and radiofrequency catheter ablation (RCA). Six patients (33.3%) underwent pacemaker implantation (PM). CONCLUSIONS The present study describes the clinical treatment for a rare cardiac syndrome caused by a PRKAG2 mutation.

The Burden of Early Phenotypes and the Influence of Wall Thickness in Hypertrophic Cardiomyopathy Mutation Carriers: Findings From the HCMNet Study

Importance

Sarcomere mutations and left ventricular (LV) hypertrophy (LVH) are cardinal features of hypertrophic cardiomyopathy (HCM). However, little is known about the full spectrum of phenotypic manifestations or how LVH influences disease expression.

Objectives

(1) To characterize and assess phenotypic burden in sarcomere mutation carriers (genotype positive [G+]) and (2) to investigate the correlation between LV wall thickness (LVWT) and other disease features in mutation carriers.

Design, Setting, and Participants

This investigation was a cross-sectional, multicenter observational study in the setting of the HCMNet network of HCM clinical centers. Mutation carriers with LVH (G+/LVH+), mutation carriers without LVH (G+/LVH-), and healthy related control individuals (G-/LVH-) were enrolled through HCMNet sites. A total of 193 participants were enrolled and underwent study procedures. Participants were enrolled between April 9, 2010, and January 30, 2012. Study analysis was performed between June 2015 and May 2016.

Exposures

The primary stratifying variables were the presence of a sarcomere mutation and measures of LVWT.

Main Outcomes and Measures

Variables from standardized exercise testing, echocardiography, cardiac magnetic resonance imaging, serum biomarker measurement, and electrocardiography were compared across study cohorts.

Results

Analyses were performed in 178 participants, including 81 G+/LVH+ (mean [SD] age at baseline, 27 [14] years), 55 G+/LVH- (20 [10] years), and 42 G-/LVH- (18 [8] years). All mutation carriers had smaller LV cavity, higher ratio of LVWT to diastolic diameter, and higher echocardiographic LV ejection fraction than controls. A phenotypic burden score was evaluated as the cumulative number of 7 traits (changes on electrocardiography; decreased LV systolic, diastolic diameter, or septal E' velocity; higher ratio of LVWT to diastolic diameter; serum troponin level; and natriuretic peptide level) in each individual. The mean (SE) phenotypic burden was 4.9 (0.2) phenotypes per individual in G+/LVH+, 2.4 (0.2) in G+/LVH-, and 1.3 (0.2) in controls (P < .001). Classification and regression tree analysis identified an LV end-diastolic dimension z score less than -1.85 or the combination of an LV end-diastolic dimension z score of -1.85 or higher and a septal E' velocity z score less than -0.52 as having 74% accuracy in discriminating G+/LVH- participants from controls. In mutation carriers, clinical variables demonstrated a continuous correlation with LVWT, generally without a clear cutoff signifying pathologic transition.

Conclusions and Relevance

G+/LVH- individuals demonstrated altered cardiac dimensions and function and a higher burden of early phenotypes than healthy G- controls. Two methods discriminated phenotypic subgroups, namely, a sum across 7 traits and a regression tree-based rule that identifies constellations of distinguishing factors. Greater LVWT is associated with more prominent cardiac abnormalities in a continuous, although not always linear, manner. A single value of LVWT could not dichotomize the presence or absence of disease.

The mechanisms, diagnosis and management of mitral regurgitation in mitral valve prolapse and hypertrophic cardiomyopathy

Valvular disease is a frequent cardiac pathology leading to heart failure and, ultimately, death. Mitral regurgitation, defined as the inability of the two mitral leaflets to coapt, is a common valvular disease and a self sustained pathology. A better understanding of the mitral valve histological layers provides a better understanding of the leaflet and chordae changes in mitral valve prolapse. Mitral valve prolapse may occur in myxomatous degenerative abnormalities, connective tissue disorders or in sporadic isolated cases. It is the most common mitral abnormality of non-ischemic cause leading to severe surgery-requiring mitral regurgitation. In addition to standard echocardiographic investigations, newly implemented three-dimensional techniques are being used and they permit a better visualisation, from the so-called ‘surgical view’, and an improved evaluation of the mitral valve. Hypertrophic cardiomyopathy is the most frequent inherited myocardial disease caused by mutations in various genes encoding proteins of the cardiac sarcomere, leading to a marked left ventricular hypertrophy unexplained by other comorbidities. The pathological echocardiographic hallmarks of hypertrophic cardiomyopathy are left ventricular hypertrophy, left ventricular outflow tract obstruction and systolic anterior motion of the mitral valve. The systolic anterior motion of the mitral valve contributes to the development of mitral regurgitation and further narrows the left ventricular outflow tract, leading to more severe symptomatology. Cardiac magnetic resonance imaging accurately measures the left ventricular mass, the degree of diastolic function and it may also be used to distinguish phenotypic variants. The clinical outcome of patients with these pathologies is mostly determined by the selected option of treatment. The purpose of surgical correction regarding mitral valve involvement is to restore valvular competence. Surgery has proven to be the only useful treatment in preventing heart failure, improving symptomatology and reducing mortality. Our approach wishes to enhance the understanding of the mitral valve’s involvement in hypertrophic cardiomyopathy and mitral valve prolapse from genetic, haemodynamic and clinical perspectives, as well as to present novelties in the grand field of treatment.

Mitral valve disease--morphology and mechanisms

Mitral valve disease is a frequent cause of heart failure and death. Emerging evidence indicates that the mitral valve is not a passive structure, but--even in adult life--remains dynamic and accessible for treatment. This concept motivates efforts to reduce the clinical progression of mitral valve disease through early detection and modification of underlying mechanisms. Discoveries of genetic mutations causing mitral valve elongation and prolapse have revealed that growth factor signalling and cell migration pathways are regulated by structural molecules in ways that can be modified to limit progression from developmental defects to valve degeneration with clinical complications. Mitral valve enlargement can determine left ventricular outflow tract obstruction in hypertrophic cardiomyopathy, and might be stimulated by potentially modifiable biological valvular-ventricular interactions. Mitral valve plasticity also allows adaptive growth in response to ventricular remodelling. However, adverse cellular and mechanobiological processes create relative leaflet deficiency in the ischaemic setting, leading to mitral regurgitation with increased heart failure and mortality. Our approach, which bridges clinicians and basic scientists, enables the correlation of observed disease with cellular and molecular mechanisms, leading to the discovery of new opportunities for improving the natural history of mitral valve disease.

Targeted Mybpc3 Knock-Out Mice with Cardiac Hypertrophy Exhibit Structural Mitral Valve Abnormalities

MYBPC3 mutations cause hypertrophic cardiomyopathy, which is frequently associated with mitral valve (MV) pathology. We reasoned that increased MV size is caused by localized growth factors with paracrine effects. We used high-resolution echocardiography to compare Mybpc3-null, heterozygous, and wild-type mice (n = 84, aged 3–6 months) and micro-CT for MV volume (n = 6, age 6 months). Mybpc3-null mice showed left ventricular hypertrophy, dilation, and systolic dysfunction compared to heterozygous and wild-type mice, but no systolic anterior motion of the MV or left ventricular outflow obstruction. Compared to wild-type mice, echocardiographic anterior leaflet length (adjusted for left ventricular size) was greatest in Mybpc3-null mice (1.92 ± 0.08 vs. 1.72 ± 0.08 mm, p < 0.001), as was combined leaflet thickness (0.23 ± 0.04 vs. 0.15 ± 0.02 mm, p < 0.001). Micro-CT analyses of Mybpc3-null mice demonstrated increased MV volume (0.47 ± 0.06 vs. 0.15 ± 0.06 mm³, p = 0.018) and thickness (0.35 ± 0.04 vs. 0.12 ± 0.04 mm, p = 0.002), coincident with increased markers of TGFβ activity compared to heterozygous and wild-type littermates. Similarly, excised MV from a patient with MYBPC3 mutation showed increased TGFβ activity. We conclude that MYBPC3 deficiency causes hypertrophic cardiomyopathy with increased MV leaflet length and thickness despite the absence of left ventricular outflow-tract obstruction, in parallel with increased TGFβ activity. MV changes in hypertrophic cardiomyopathy may be due to paracrine effects, which represent targets for therapeutic studies.

Evaluation of left ventricular diastolic function by global strain rate imaging in patients with obstructive hypertrophic cardiomyopathy: a simultaneous speckle tracking echocardiography and cardiac catheterization study

BACKGROUND

Impaired left ventricular (LV) diastolic function is a common pathophysiological feature of patients with hypertrophic cardiomyopathy (HCM). The noninvasive evaluation of diastolic function in these patients remains a challenge. Speckle tracking echocardiography (STE) provides direct information on intrinsic myocardial function and may improve the diagnostic of diastolic dysfunction in HCM patients.

METHODS AND RESULTS

We retrospectively analyzed 51 patients with obstructive HCM (HOCM). Strain rate (SR) curves were obtained for 18 different segments of the LV myocardium. The peak SR during the isovolumic relaxation period (SRIVR ) and the peak early diastolic strain rate (SRE ) were measured for each segment. Cardiac catheterization was performed within 24 hours after echocardiographic analysis. LV end-diastolic pressure (LVEDP) was measured and time constant of myocardial relaxation (τ) was calculated. We therefore correlated STE-derived with invasive indices and compared it with flow and tissue Doppler measurements. SRIVR and SRE were significantly reduced in all 51 HOCM patients (0.16 ± 0.09%/sec and 0.71 ± 0.25%/sec).The ratio of peak early mitral inflow velocities to SRIVR and SRE (E/SRIVR and E/SRE ) correlated well with LVEDP (r = 0.760, P < 0.001; r = 0.401, P = 0.004). Receiver operating characteristic analysis shown E/SRE ratio had the largest under curve area in predicting HOCM patients with seriously elevated LVEDP. In addition, SRIVR and SRE significantly related with τ (r = -0.611, P < 0.001; r = -0.369, P = 0.008).

CONCLUSIONS

Diastolic function was seriously impaired in HOCM patients. The E/SRE ratio can be used to predict LVEDP with acceptable accurate in HOCM patients. In addition, SRIVR is a reliable parameter to assess LV relaxation in patients with HOCM.

Comparison of echocardiographic and cardiac magnetic resonance imaging in hypertrophic cardiomyopathy sarcomere mutation carriers without left ventricular hypertrophy

BACKGROUND

Left ventricular hypertrophy (LVH) typically manifests during or after adolescence in sarcomere mutation carriers at risk for developing hypertrophic cardiomyopathy. Guidelines recommend serial imaging of mutation carriers without LVH (G+/LVH-) to monitor for phenotypic evolution, but the optimal strategy is undefined. Compared with echocardiography (echo), cardiac MRI (CMR) offers improved endocardial visualization and potential to assess scar. However, the incremental advantage offered by CMR for early diagnosis of hypertrophic cardiomyopathy is unclear. Therefore, we systematically compared echo and CMR in G+/LVH- subjects.

METHODS AND RESULTS

A total of 40 sarcomere mutation carriers with normal echo wall thickness (<12 mm or z score <2.5 in children) underwent concurrent CMR. Mean age was 21.7±11.1 years, 55% were female. If left ventricular wall thickness seemed nonuniform, the size and location of relatively thickened segments were noted. Late gadolinium enhancement was assessed with CMR. Diagnostic agreement between echo and CMR was good (90%), although CMR measurements of left ventricular wall thickness were ≈19% lower than echo. Four subjects had mild hypertrophy (12.6-14 mm; ≤2 segments) appreciated by CMR but not echo. No subjects had late gadolinium enhancement. During median 35-month follow-up, 2 subjects developed overt hypertrophic cardiomyopathy, including 1 with mild LVH by CMR at baseline.

CONCLUSIONS

Echo is unlikely to miss substantial LVH; however, CMR identified mild hypertrophy in ≈10% of mutation carriers with normal echo wall thickness. CMR may be a useful adjunct in hypertrophic cardiomyopathy family screening, particularly in higher risk situations, or if echocardiographic images are suboptimal or suggest borderline LVH.

The mitral valve in hypertrophic cardiomyopathy: old versus new concepts

Elongation and pathological thickening of the mitral valve (MV) is commonly seen in hypertrophic cardiomyopathy (HCM), and its pathogenic basis is poorly understood. Associated features include mal-positioning of the papillary muscles and MV, as well as systolic anterior motion (SAM) of the MV leaflets, which can worsen the turbulence and dynamic left ventricular outflow tract (LVOT) gradient. Coaptation of the MV leaflets depends on both anterior and posterior leaflet length and position, and failure of either to optimally adapt in this setting can result in mitral regurgitation or worsened LVOT obstruction. The cause of MV enlargement in HCM is not currently understood, and several different hypotheses may be relevant. The lack of correlation between MV size and the severity of left ventricular hypertrophy, as well as the early findings in genetically predisposed individuals with sarcomere mutations, suggest that it may be an intrinsic aspect of HCM in certain individuals. Other evidence points to a reactive process in the setting of excess production of paracrine growth factors in diseased myocardium that may influence valve overgrowth. Improved understanding of the responsible adaptive mechanisms will pave the way for studies targeted on the prevention and treatment of MV disease in HCM.

Diastolic dysfunction without left ventricular hypertrophy is an early finding in children with hypertrophic cardiomyopathy-causing mutations in the beta-myosin heavy chain, alpha-tropomyosin, and myosin-binding protein C genes

OBJECTIVES

We investigated the presence of left ventricular hypertrophy (LVH) and features of diastolic dysfunction in genotype-confirmed children from families with hypertrophic cardiomyopathy (HCM) and healthy control children.

BACKGROUND

In subjects with HCM-causing mutations, LVH usually does not evolve until adolescence. Diastolic dysfunction has not been systematically evaluated in children carrying HCM-causing mutations.

METHODS

All children (aged 1.5-16.7 years) from 14 HCM families with identified disease-causing mutations (the Arg719Trp mutation in the beta-myosin heavy chain gene [MYH7], the Asp175Asn mutation in the alpha-tropomyosin gene [TPM1], the Gln1061X mutation in the myosin-binding protein C gene [MYBPC3], and the IVS5-2A-->C mutation in the MYBPC3 gene) and 53 matched control children were examined with electrocardiography and 2- and 3-dimensional echocardiography (2DE and 3DE). Natriuretic peptides were measured in children from HCM families and 67 control children.

RESULTS

Of 53 children from HCM families, 27 (51%) had a disease-causing mutation (G+). G+ children had slightly thicker septum on 2DE compared with the control children (P = .004), but only 3 (11%) of 27 G+ children exceeded the 95th percentile values of the body surface area-adjusted maximal LV thickness of healthy children (the major echocardiographic criterion for HCM). However, prolonged isovolumetric relaxation time, increased left atrial volume on 3DE, or increased levels of NT-proANP, all features suggestive of diastolic dysfunction, were found in 14 (52%) of 27 G+ children.

CONCLUSIONS

In children with HCM-causing mutations, signs of diastolic dysfunction are found in about half of the cases, as LVH is present only in small percentage of these children.

Hypertrophic cardiomyopathy in childhood

Hypertrophic cardiomyopathy (HCM) is a heterogeneous and relatively common genetic cardiac disease that has been the subject of intense scrutiny and investigation for over 40 years. HCM is an important cause of disability and death in patients of all ages, although unexpected sudden death in the young is perhaps the most devastating component of the natural history. Therefore, while HCM is uncommon in pediatric cardiology practice, it is nevertheless a disease of great importance to young people and those clinicians charged with their care. Due to marked heterogeneity in clinical expression, natural history and prognosis, diagnostic and management strategies often represent a dilemma (and even the source of controversy) to both primary care clinicians and cardiovascular specialists. Consequently, it is timely to place perspective and clarify many of these relevant clinical issues, and profile the rapidly evolving concepts regarding HCM, especially as they may impact on this disease in childhood.

Relation of left ventricular thickness to age and gender in hypertrophic cardiomyopathy

Left ventricular (LV) wall thickening is the most consistent clinical marker of hypertrophic cardiomyopathy (HC), and characteristically increases substantially during adolescence. In this study, we used 2-dimensional echocardiography to develop a cross-sectional profile of LV wall thicknesses in adult patients with HC. We studied a regional community-based cohort of 239 consecutively enrolled patients (aged 18 to 91 years). On average, maximum LV wall thickness decreased relative to increasing age (p = 0.007) within 4 age groups: 22.8 +/- 5.1 mm (18 to 39 years) to 22.1 +/- 5.1 mm (40 to 59 years) to 21.1 +/- 3.7 mm (60 to 74 years) to 20.8 +/- 3.6 mm (>or=75 years). The LV thickness index (summation of wall thicknesses in all 4 segments) also decreased with age (p = 0.017): 63.0 +/- 12.2 mm to 59.8 +/- 11.9 mm to 58.3 +/- 10.4 mm to 57.9 +/- 9.8 mm. Decreasing magnitude of LV hypertrophy was independently associated with increasing age, but not with other relevant disease variables, such as symptoms and outflow obstruction. However, when separated by gender, this inverse relation between age and LV wall thickness was statistically significant only for women (p = 0.007). In conclusion, in an unselected HC cohort, cross-sectional analysis showed a modest but statistically significant inverse relation between age and LV hypertrophy that was largely gender-specific for women. This association constitutes another facet of the natural history of this complex and heterogenous disease and may reflect disproportionate occurrence of premature death in young patients with HC with marked hypertrophy or possibly gradual LV remodeling.