Impact of concomitant surgical interventions on outcomes of septal myectomy in obstructive hypertrophic cardiomyopathy

BACKGROUND

Septal myectomy (SM) is offered to symptomatic patients with obstructive hypertrophic cardiomyopathy (oHCM) despite medical therapy. Frequently, patients undergo concomitant planned or ad-hoc mitral valve replacement (MVR), aortic valve replacement (SAVR), or coronary artery bypass grafting (CABG).

OBJECTIVES

We sought to assess characteristics and outcomes of patients with oHCM undergoing concomitant surgical interventions at the time of SM.

METHODS

The National Readmission Databases were used to identify all SM admissions in the United States (2010-2019). Patients undergoing SM were stratified into: isolated SM (±MV repair), SM + CABG only, SM + MVR, SM + SAVR, and SM + MVR + SAVR. Primary outcomes were in-hospital mortality, in-hospital adverse events, and 30-day readmission.

RESULTS

12,063 encounters of patients who underwent SM were included (56.1% isolated SM, 9.0% SM + CABG only, 17.5% SM + MVR, 13.1% SM + SAVR, and 4.3% SM + MVR + SAVR). Patients who underwent isolated SM were younger (54.3 vs. 67.1 years-old, p < 0.01) and had lower overall comorbidity burden. In-hospital mortality was lowest in isolated SM, followed by CABG only, SM + SAVR, SM + MVR, and SM + SAVR+MVR groups (2.3% vs. 3.7% vs. 5.3% vs. 6.7% vs. 13.7%, p < 0.01), respectively. SM with combined surgical interventions was associated with higher adverse in-hospital events (24.3% vs. 11.1%, p < 0.01) and 30-day readmissions (16.9% vs. 10.4%, p < 0.01). MV repair performed concomitantly with SM was not associated with increased in-hospital mortality (3.9% vs. 3.4%, p = 0.72; aOR 0.99; 95% CI: 0.54-1.80, p = 0.97]) or adverse clinical events.

CONCLUSIONS

In SM for oHCM, patients undergoing concomitant surgical interventions were characteristically distinct. Aside from MV repair, concomitant interventions were associated with worse in-hospital death, adverse in-hospital events, and 30-day readmission.

Cardiac myosin-binding protein C N-terminal interactions with myosin and actin filaments: Opposite effects of phosphorylation and M-domain mutations

N-terminal cardiac myosin-binding protein C (cMyBP-C) domains (C0-C2) bind to thick (myosin) and thin (actin) filaments to coordinate contraction and relaxation of the heart. These interactions are regulated by phosphorylation of the M-domain situated between domains C1 and C2. In cardiomyopathies and heart failure, phosphorylation of cMyBP-C is significantly altered. We aimed to investigate how cMyBP-C interacts with myosin and actin. We developed complementary, high-throughput, C0-C2 FRET-based binding assays for myosin and actin to characterize the effects due to 5 HCM-linked variants or functional mutations in unphosphorylated and phosphorylated C0-C2. The assays indicated that phosphorylation decreases binding to both myosin and actin, whereas the HCM mutations in M-domain generally increase binding. The effects of mutations were greatest in phosphorylated C0-C2, and some mutations had a larger effect on actin than myosin binding. Phosphorylation also altered the spatial relationship of the probes on C0-C2 and actin. The magnitude of these structural changes was dependent on C0-C2 probe location (C0, C1, or M-domain). We conclude that binding can differ between myosin and actin due to phosphorylation or mutations. Additionally, these variables can change the mode of binding, affecting which of the interactions in cMyBP-C N-terminal domains with myosin or actin take place. The opposite effects of phosphorylation and M-domain mutations is consistent with the idea that cMyBP-C phosphorylation is critical for normal cardiac function. The precision of these assays is indicative of their usefulness in high-throughput screening of drug libraries for targeting cMyBP-C as therapy.

The Role of Personalized Medicine in Companion Animal Cardiology

Cardiomyopathies remain one of the most common inherited cardiac diseases in both human and veterinary patients. To date, well over 100 mutated genes are known to cause cardiomyopathies in humans with only a handful known in cats and dogs. This review highlights the need and use of personalized one-health approaches to cardiovascular case management and advancement in pharmacogenetic-based therapy in veterinary medicine. Personalized medicine holds promise in understanding the molecular basis of disease and ultimately will unlock the next generation of targeted novel pharmaceuticals and aid in the reversal of detrimental effects at a molecular level.

Electrocardiographic Findings in Genotype-Positive and Non-sarcomeric Children with Definite Hypertrophic Cardiomyopathy and Subclinical Variant Carriers

In children with hypertrophic cardiomyopathy (HCM), the genotype-phenotype association of abnormal electrocardiographic (ECG) features in the backdrop of gene positivity has not been well described. This study aimed to describe the abnormal ECG findings in children with HCM harboring who have genetic variants and determine the association with major adverse cardiac events (MACE). We retrospectively analyzed 81 variants-positive, phenotype-positive (V+P+), 66 variant-positive, phenotype-negative (V+P-), and 85 non-sarcomeric subjects. We analyzed ECG findings and clinical outcomes in the three groups of subjects. Repolarization abnormalities (ST and T wave changes) and pathologic Q waves were the most common abnormalities in variant and non-sarcomeric subjects. The V+P+ group showed higher occurrence of ST segment changes and T wave abnormalities compared to V+P- group. Independent predictors of MACE included ST segment changes (OR 3.54, CI 1.20-10.47, p = 0.022). T wave changes alone did not predict outcome (OR 2.13, CI 0.75-6.07, p = 0.157), but combined repolarization abnormalities (ST+T changes) were strong predictors of MACE (OR 5.84, CI 1.43-23.7, p = 0.014) than ST segment changes alone. Maximal wall z score by echocardiography was a predictor of MACE (OR 1.21, CI 1.07-1.37, p = 0.002). Despite the presence of significant myocardial hypertrophy (z score > 4.7), voltage criteria for LVH were much less predictive. In the non-sarcomeric group, RVH was significantly associated with MACE (OR 3.85, CI 1.08-13.73, p = 0.038). These abnormal ECG findings described on the platform of known genetic status and known myocardial hypertrophy may add incremental value to the diagnosis and surveillance of disease progression in children with HCM. Select ECG findings, particularly repolarization abnormalities, may serve as predictors of MACE in children.

Radiomics applications in cardiac imaging: a comprehensive review

Radiomics is a new emerging field that includes extraction of metrics and quantification of so-called radiomic features from medical images. The growing importance of radiomics applied to oncology in improving diagnosis, cancer staging and grading, and improved personalized treatment, has been well established; yet, this new analysis technique has still few applications in cardiovascular imaging. Several studies have shown promising results describing how radiomics principles could improve the diagnostic accuracy of coronary computed tomography angiography (CCTA) and magnetic resonance imaging (MRI) in diagnosis, risk stratification, and follow-up of patients with coronary heart disease (CAD), ischemic heart disease (IHD), hypertrophic cardiomyopathy (HCM), hypertensive heart disease (HHD), and many other cardiovascular diseases. Such quantitative approach could be useful to overcome the main limitations of CCTA and MRI in the evaluation of cardiovascular diseases, such as readers' subjectiveness and lack of repeatability. Moreover, this new discipline could potentially overcome some technical problems, namely the need of contrast administration or invasive examinations. Despite such advantages, radiomics is still not applied in clinical routine, due to lack of standardized parameters acquisition, inconsistent radiomic methods, lack of external validation, and different knowledge and experience among the readers. The purpose of this manuscript is to provide a recent update on the status of radiomics clinical applications in cardiovascular imaging.

Baseline and Longitudinal Imaging of Hypertrophic Cardiomyopathy in the Era of Emerging Therapeutics

PURPOSE OF REVIEW

In this review, we will overview the baseline and longitudinal imaging modalities utilized in the care of patients with hypertrophic cardiomyopathy (HCM) with a focus on echocardiography and cardiac magnetic resonance (CMR) imaging, especially in the new era of cardiac myosin inhibitors (CMIs).

RECENT FINDINGS

Traditional therapies for hypertrophic cardiomyopathy (HCM) have been well established for decades. Attempts to investigate new drug therapy in HCM resulted in neutral clinical trials, until the discovery of cardiac myosin inhibitors (CMIs). The introduction of this new class of small oral molecules which target the hypercontractility resulting from excessive actin-myosin cross-bridging at the sarcomere level is the first therapeutic option which directly addresses the underlying pathophysiology of HCM. While imaging has always played a central role in HCM diagnosis and management, CMIs introduced a new paradigm in the use of imaging to evaluate and monitor patients with HCM. Echocardiography and cardiac magnetic resonance imaging (CMR) are the central modalities in the care of patients with HCM, but their roles and our understanding of their strengths and limitations are evolving as newer therapeutics are being investigated in clinical trials and in daily practice. In this review, we will focus the recent CMI trials and discuss the role of baseline and longitudinal imaging with echocardiography and CMR in the care of patients with HCM in the era of CMIs.

Systolic anterior motion of the mitral valve in hypertrophic cardiomyopathy: a narrative review

Background and Objective

The prevalence of hypertrophic cardiomyopathy (HCM) is estimated to be 1 in 200 to 500 individuals, with systolic anterior motion (SAM) of the mitral valve (MV) and left ventricular outflow tract (LVOT) obstruction present in 60% to 70%. In this narrative review, we aim to elucidate the pathophysiology of SAM-septal contact and LVOT obstruction in HCM by presenting a detailed review on the anatomy of the MV apparatus in HCM, examining the various existing theories pertaining to the SAM phenomenon as supported by cardiac imaging, and providing a critical assessment of management strategies for SAM in HCM.

Methods

A literature review was performed using PubMed, EMBASE, Ovid, and the Cochrane Library, of all scientific articles published through December 2021. A focus was placed on descriptive studies, reports correlating echocardiographic findings with pathologic diagnosis, and outcomes studies.

Key Content and Findings

The pathophysiology of SAM involves the complex interplay between HCM morphology, MV apparatus anatomic abnormalities, and labile hemodynamic derangements. Echocardiography and cardiac magnetic resonance (CMR) vector flow mapping have identified drag forces, as opposed to the "Venturi effect", as the main hydraulic forces responsible for SAM. The degree of mitral regurgitation with SAM is variable, and its severity is correlated with degree of LVOT obstruction and outcomes. First line therapy for the amelioration of SAM and LVOT obstruction is medical therapy with beta-blockers, non-dihydropyridine calcium-channel blockers, and disopyramide, in conjunction with lifestyle modifications. In refractory cases septal reduction therapy is performed, which may be combined with a 'resect-plicate-release' procedure, anterior mitral leaflet extension, surgical edge-to-edge MV repair, anterior mitral leaflet retention plasty, or secondary chordal cutting.

Conclusions

Recent scientific advances in the field of HCM have allowed for a maturation of our understanding of the SAM phenomenon. Cardiac imaging plays a critical role in its diagnosis, treatment, and surveillance, and in our ability to apply the appropriate therapeutic regimens. The increasing prevalence of HCM places an emphasis on continued basic and clinical research to further improve outcomes for this challenging population.

Inhibiting cardiac myeloperoxidase alleviates the relaxation defect in hypertrophic cardiomyocytes

AIMS

Hypertrophic cardiomyopathy (HCM) is characterized by cardiomyocyte hypertrophy and disarray, and myocardial stiffness due to interstitial fibrosis, which result in impaired left ventricular filling and diastolic dysfunction. The latter manifests as exercise intolerance, angina, and dyspnoea. There is currently no specific treatment for improving diastolic function in HCM. Here, we investigated whether myeloperoxidase (MPO) is expressed in cardiomyocytes and provides a novel therapeutic target for alleviating diastolic dysfunction in HCM.

METHODS AND RESULTS

Human cardiomyocytes derived from control-induced pluripotent stem cells (iPSC-CMs) were shown to express MPO, with MPO levels being increased in iPSC-CMs generated from two HCM patients harbouring sarcomeric mutations in the MYBPC3 and MYH7 genes. The presence of cardiomyocyte MPO was associated with higher chlorination and peroxidation activity, increased levels of 3-chlorotyrosine-modified cardiac myosin binding protein-C (MYBPC3), attenuated phosphorylation of MYBPC3 at Ser-282, perturbed calcium signalling, and impaired cardiomyocyte relaxation. Interestingly, treatment with the MPO inhibitor, AZD5904, reduced 3-chlorotyrosine-modified MYBPC3 levels, restored MYBPC3 phosphorylation, and alleviated the calcium signalling and relaxation defects. Finally, we found that MPO protein was expressed in healthy adult murine and human cardiomyocytes, and MPO levels were increased in diseased hearts with left ventricular hypertrophy.

CONCLUSION

This study demonstrates that MPO inhibition alleviates the relaxation defect in hypertrophic iPSC-CMs through MYBPC3 phosphorylation. These findings highlight cardiomyocyte MPO as a novel therapeutic target for improving myocardial relaxation associated with HCM, a treatment strategy which can be readily investigated in the clinical setting, given that MPO inhibitors are already available for clinical testing.

Differences in clinical features of hypertrophic cardiomyopathy with or without left ventricular enlargement

BACKGROUND

Few studies have focused on the clinical features of hypertrophic cardiomyopathy (HCM) with enlarged left ventricle (ELV).

METHODS

In this study, participants were patients with HCM (n=170), who were divided into two groups [ELV and normal left ventricle (NLV)] according to left ventricle size. Age at diagnosis, sex, complications, electrocardiogram (ECG), symptoms, drug treatment, and echocardiographic parameters were compared between the NLV (n=153) and ELV (n=17) groups.

RESULTS

The incidence of end-stage HCM (ES-HCM) among all HCM patients was 5.29%, while that of ELV was 10.0%. For all patients with HCM and those with asymmetric septal HCM (ASHCM), there were more males with ELV than NLV. Of the patients with HCM and ASHCM, left ventricular ejection fraction (LVEF) was significantly lower in the ELV group than the NLV group; accordingly, the rates of diuretics use in the ELV group were higher than those in the NLV group. Among apical HCM (ApHCM) patients, the left atrial diameter (LAd), incidence of atrial fibrillation (Af) or ST-T change, and rate of angiotensin converting enzyme inhibitor (ACEI)/angiotensin receptor blocker (ARB) use were all higher in the ELV group compared to the NLV group.

CONCLUSIONS

These findings suggest that the prevalence of ES-HCM in HCM patients with ELV was higher than those with NLV. Additionally, ELV is more common in men than women and there are differences in the clinical features of different types of HCM with ELV.

Interplay of Genotype and Substrate Stiffness in Driving the Hypertrophic Cardiomyopathy Phenotype in iPSC-Micro-Heart Muscle Arrays

INTRODUCTION

In clinical and animal studies, Hypertrophic Cardiomyopathy (HCM) shares many similarities with non-inherited cardiac hypertrophy induced by pressure overload (hypertension). This suggests a potential role for mechanical stress in priming tissues with mutation-induced changes in the sarcomere to develop phenotypes associated with HCM, including hypercontractility and aberrant calcium handling. Here, we tested the hypothesis that heterozygous loss of function of Myosin Binding Protein C (MYBCP3 +/- , mutations in which account for almost 50% of inherited HCM) combines with environmental stiffness to drive HCM phenotypes.

METHODS

We differentiated isogenic control (WTC) and MYBPC3 +/- iPSC into cardiomyocytes using small molecule manipulation of Wnt signaling, and then purified them using lactate media. The purified cardiomyocytes were seeded into "dog bone" shaped stencil molds to form micro-heart muscle arrays (μHM). To mimic changes in myocardial stiffness stemming from pressure overload, we varied the rigidity of the substrates μHM contract against. Stiffness levels ranged from those corresponding to fetal (5 kPa), healthy (15 kPa), pre-fibrotic (30 kPa) to fibrotic (65 kPa) myocardium. Substrates were embedded with a thin layer of fluorescent beads to track contractile force, and parent iPSC were engineered to express the genetic calcium indicator, GCaMP6f. High speed video microscopy and image analysis were used to quantify calcium handling and contractility of μHM.

RESULTS

Substrate rigidity triggered physiological adaptation for both genotypes. However, MYBPC3 +/- μHM showed a lower tolerance to substrate stiffness with the peak traction on 15 kPa, while WTC μHM had peak traction on 30 kPa. MYBPC3 +/- μHM exhibited hypercontractility, which was exaggerated by substrate rigidity. MYBPC3 +/- μHM hypercontractility was associated with longer rise times for calcium uptake and force development, along with higher overall Ca2+ intake.

CONCLUSION

We found MYBPC3 +/- mutations cause iPSC-μHM to exhibit hypercontractility, and also a lower tolerance for mechanical stiffness. Understanding how genetics work in combination with mechanical stiffness to trigger and/or exacerbate pathophysiology may lead to more effective therapies for HCM.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at (10.1007/s12195-021-00684-x).

Preoperative ventricular late potentials and the risk of adverse events in patients with obstructive hypertrophic cardiomyopathy undergoing septal myectomy

BACKGROUND

Ventricular late potentials (VLPs) detected by signal-averaged electrocardiogram are considered as an indicator of electrical instability in diseased myocardium. Little information exists about the VLPs and their effects on clinical prognosis in patients with obstructive hypertrophic cardiomyopathy (OHCM) undergoing septal myectomy.

METHODS

Patients with OHCM who underwent septal myectomy from January 2019 to December 2019 were prospectively enrolled. All patients underwent signal-averaged electrocardiogram. Patients were subsequently divided into two groups based on the presence or absence of VLPs. All patients were followed up after surgery to obtain information of survival status and adverse events, including all-cause mortality, congestive heart failure requiring hospitalization, new-onset stroke, and unexplained syncope.

RESULTS

In total, 128 patients (47.5±12.8 years, 57.8% male) were enrolled. There were 21 (16.4%) individuals in the VLPs-positive group and 107 (83.6%) individuals in the VLPs-negative group. There were no statistically significant differences in non-sustained ventricular tachycardia and late gadolinium enhancement on cardiovascular magnetic resonance images between the two groups. Eight adverse events were reported at the 14.9±4.1 months follow-up. The rates of adverse events in groups of VLPs-positive and VLPs-negative were 23.8% (5/21) and 2.8% (3/107) of cases, respectively. These events included three patients hospitalized for heart failure, two who experienced ischemic strokes, and three with unexplained syncope, respectively. Patients in the VLPs-positive group had a higher risk of adverse events than those in the VLPs-negative group (P<0.001). The presence of positive VLPs (hazard ratio =9.095, 95% confidence intervals: 2.080-39.776, P=0.003) was a strong independent risk factor of adverse events by multivariate Cox regression analysis. Cardiac function Class III or IV, as defined by the New York Heart Association classification, was also an independent risk factor of adverse events (hazard ratio =13.756, 95% confidence intervals: 1.667-113.510, P=0.015).

CONCLUSIONS

VLPs may increase the risk of adverse events in patients with OHCM after septal myectomy, which may be used as a screening test for further risk stratification.

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.

Myocarditis combined with hypertrophic cardiomyopathy: a case report

Myocarditis can cause ventricular wall thickening due to myocardial edema. If the condition improves, the ventricular wall thickening should gradually decrease; a persistent thickening of the patient's ventricular wall indicates the coexistence of hypertrophic cardiomyopathy (HCM) and myocarditis. A 30-year-old man was referred to our hospital with continuous chest pain accompanied by profuse sweating. He suffered from fever for two days (the maximum body temperature: 38 ℃) and the conditions improved following the use of antipyretics as self-administered medication before admission. Electrocardiogram exhibited ST-segment elevation in leads I and avL, and ST-T wave changes in leads II, III, avF, and V1-V6. Marked elevation of cardiac troponin I was found on laboratory testing. Respiratory tract infection testing showed negative results. A TORCH screen revealed positive herpes simplex virus (HSV), rubella virus (RV), and cytomegalovirus (CMV) IgG but all with negative IgM titer. Ultrasonic echocardiography showed thickness of the interventricular septum (17 mm) and diffuse left ventricular (LV) hypokinesia, without LV outflow tract obstruction. After consultation with the cardiology team, a diagnosis of myocarditis with HCM was made. Patients with myocarditis should be alerted to the possibility of HCM when there is persistent ventricular wall thickening.

Clinical impact of atrial fibrillation in a nationwide cohort of hypertrophic cardiomyopathy patients

Background

The clinical implications of atrial fibrillation (AF) in hypertrophic cardiomyopathy (HCM) patients are incompletely characterized. We investigated the impact of AF on stroke and mortality, assessed the performance of the CHA2DS2-VASc score, and explored the predictors of stroke in HCM patients.

Methods

A nationwide cohort of HCM patients (n=8,349, mean age 60.7) identified from 2010 to 2015 from the Korean National Health Insurance database were followed up for occurrence of ischemic stroke or all-cause death.

Results

During a mean follow-up of 2.5 years, the incidence rate of stroke was 2.69 and 5.87, and mortality rate was 2.06 and 4.44 per 100 person-years in non-AF and AF patients, respectively. AF was independently associated with a 60% and 50% increased risk for stroke and all-cause mortality, respectively. The AF-associated increase in risk of stroke was more prominent in HCM patients with no or few risk factors. The CHA2DS2-VASc score showed poor discrimination of stroke risk in HCM patients with AF, mostly due to the high incidence of stroke in patients with scores of 0 or 1. Traditional risk factors were not always associated with stroke in HCM patients with AF; age, heart failure, high blood pressure and GGT were the strongest predictors of stroke in this population. HCM patients without AF also showed increased incidence of stroke at CHA2DS2-VASc ≥1.

Conclusions

AF was independently associated with increased risks for stroke and all-cause mortality in patients with HCM. The CHA2DS2-VASc score showed poor discrimination of stroke risk in HCM patients with AF.

Surgical outcome for hypertrophic cardiomyopathy patients with extreme interventricular septal thickness: a propensity score matched study

Background

Hypertrophic cardiomyopathy (HCM) with extreme interventricular septal thickness (IVST) is associated with a higher incidence of adverse cardiovascular events. However, the results of these patients who underwent septal myectomy are unclear.

Methods

We studied 47 HCM patients with IVST ≥30 mm who underwent septal myectomy between 2011 and 2018 in Anzhen Hospital. After a 2:1 propensity score matching, the study cohort included 141 patients and 94 patients with IVST <30 mm.

Results

Patients with IVST ≥30 mm had a longer clinical course of disease, high incidence of syncope, palpitation, and moderate or severe mitral regurgitation. After a mean follow-up of 34.0±21.3 months, 6 patients died, including 5 with IVST ≥30 mm and 1 with IVST <30 mm. The 5-year survival free of all-cause mortality was significantly higher in patients with IVST ≥30 mm than in those with IVST <30 mm (98.9% vs. 85.7%, P=0.03). Multivariable Cox analysis revealed that IVST ≥30 mm (HR: 1.12, 95% CI: 1.01–1.25, P=0.028) was an independent risk factor for all-cause mortality. Meanwhile, left ventricular end diastole diameter (HR: 0.72, 95% CI: 0.54–0.97, P=0.031) and age (HR: 0.91, 95% CI: 0.83–0.99, P=0.025) were also independent risk factors for all-cause mortality in this special cohort. Furthermore, the incidence of NYHA class III or IV was significantly higher in patients with IVST ≥30 mm.

Conclusions

The surgical outcome was poor in a matched cohort of HCM patients with IVST ≥30 mm, which was mainly reflected by mortality and the incidence of NYHA class III or IV.

Phenotyping of hypertensive heart disease and hypertrophic cardiomyopathy using personalized 3D modelling and cardiac cine MRI

Differential diagnosis of hypertensive heart disease (HHD) and hypertrophic cardiomyopathy (HCM) is clinically challenging but important for treatment management. This study aims to phenotype HHD and HCM in 3D + time domain by using a multiparametric motion-corrected personalized modeling algorithm and cardiac magnetic resonance (CMR). 44 CMR data, including 12 healthy, 16 HHD and 16 HCM cases, were examined. Multiple CMR phenotype data consisting of geometric and dynamic variables were extracted globally and regionally from the models over a full cardiac cycle for comparison against healthy models and clinical reports. Statistical classifications were used to identify the distinctive characteristics and disease subtypes with overlapping functional data, providing insights into the challenges for differential diagnosis of both types of disease. While HCM is characterized by localized extreme hypertrophy of the LV, wall thickening/contraction/strain was found to be normal and in sync, though it was occasionally exaggerated at normotrophic/less severely hypertrophic regions during systole to preserve the overall ejection fraction (EF) and systolic functionality. Additionally, we observed that hypertrophy in HHD could also be localized, although at less extreme conditions (i.e. more concentric). While fibrosis occurs mostly in those HCM cases with aortic obstruction, only minority of HHD patients were found affected by fibrosis. We demonstrate that subgroups of HHD (i.e. preserved and reduced EF: HHDpEF & HHDrEF) have different 3D + time CMR characteristics. While HHDpEF has cardiac functions in normal range, dilation and heart failure are indicated in HHDrEF as reflected by low LV wall thickening/contraction/strain and synchrony, as well as much reduced EF.

Current state of the roles of alcohol septal ablation and surgical myectomy in the treatment of hypertrophic obstructive cardiomyopathy

Hypertrophic cardiomyopathy is a genetically determined disorder resulting in left ventricular hypertrophy. In a majority of the estimated 20 million people affected worldwide, left ventricular outflow obstruction is present at rest or with provocation. The presence and degree of obstruction influence the symptomatic presentation, treatment strategies and prognosis of affected individuals. Pharmacologic therapy with beta-adrenergic blocking drugs and calcium channel blockers is the principal treatment strategy in symptomatic patients with left ventricular outflow obstruction but is ineffective in many patients. When symptoms of exertional shortness of breath, chest pain and/or syncope prove refractory to medical therapy and there is persisting left ventricular outflow obstruction, or when there is drug intolerance, septal reduction strategies (surgical myectomy and alcohol septal ablation) are quite effective. Selection of the optimal septal reduction strategy for a given patient has become controversial and is determined largely by the medical system providing treatment strategies for the patient. Regretably, there are no randomized trials comparing myectomy and ablation and none are anticipated. The comprehensive Hypertrophic Cardiomyopathy Guideline Statements published in 2011 and 2014 differ significantly with the earlier statement favoring surgical myectomy and the more recent statement giving equal class I status to the two septal reduction strategies in adult patients with drug-refractory symptoms. Recently published studies of long-term follow-up of patients after alcohol septal ablation in Europe, where surgical myectomy is rarely performed, confirm long-term safety and effectiveness with survival free of cardiac events exceeding 96% at 15 years. The lesser degree of discomfort and more rapid recovery associated with the minimally invasive catheter-based alcohol ablation procedure coupled with the recently published long-term safety data favor an increased use of this strategy in symptomatic adult patients with hypertrophic obstructive cardiomyopathy (HOCM).

Long-term outcomes of childhood onset Noonan compared to sarcomere hypertrophic cardiomyopathy

Background

To compare outcome and cardiac pathology between patients with Noonan syndrome (N-HCM) and sarcomere protein-associated (S-HCM) childhood onset hypertrophic cardiomyopathy (HCM).

Methods

Clinical data were recorded from medical charts. Primary endpoint was survival. Secondary endpoints were survival without hospitalization, without intervention or without arrhythmic events. Functional clinical status and results from genetic testing, imaging, electrocardiographic (ECG) studies, cardiopulmonary exercise testing (CPET) and histopathology were compared between groups.

Results

Childhood HCM was diagnosed in 29 N-HCM and 34 S-HCM patients. Follow-up time was greater than 10 years in more than half of all patients. Mortality was below 7% and not different between groups. Children with N-HCM presented at a younger age and there was less time of survival without hospitalization for heart failure or intervention in N-HCM compared to S-HCM patients. Clinical functional status improved over time in N-HCM patients. On long-term follow-up, left ventricular posterior wall thickness indexed to body surface area decreased in N-HCM and increased in S-HCM patients. There was a trend to lower risk for severe arrhythmic events in N-HCM patients and only S-HCM individuals received an implantable cardioverter-defibrillator. There were no differences between groups in ventricular function, ECG and CPET parameters. Myocardial fibrosis as assessed by histopathology of myocardial specimens and cardiovascular magnetic resonance with late gadolinium enhancement or T1 mapping was present in both groups.

Conclusions

When compared to S-HCM patients, children with N-HCM have increased morbidity during early disease course, but favorable long-term outcome with low mortality, stagnation of myocardial hypertrophy, and low risk for malignant arrhythmias.

Hypertrophic cardiomyopathy: genetics and clinical perspectives

Hypertrophic cardiomyopathy (HCM) is the most common inherited heart disease and defined by unexplained isolated progressive myocardial hypertrophy, systolic and diastolic ventricular dysfunction, arrhythmias, sudden cardiac death and histopathologic changes, such as myocyte disarray and myocardial fibrosis. Mutations in genes encoding for proteins of the contractile apparatus of the cardiomyocyte, such as β-myosin heavy chain and myosin binding protein C, have been identified as cause of the disease. Disease is caused by altered biophysical properties of the cardiomyocyte, disturbed calcium handling, and abnormal cellular metabolism. Mutations in sarcomere genes can also activate other signaling pathways via transcriptional activation and can influence non-cardiac cells, such as fibroblasts. Additional environmental, genetic and epigenetic factors result in heterogeneous disease expression. The clinical course of the disease varies greatly with some patients presenting during childhood while others remain asymptomatic until late in life. Patients can present with either heart failure symptoms or the first symptom can be sudden death due to malignant ventricular arrhythmias. The morphological and pathological heterogeneity results in prognosis uncertainty and makes patient management challenging. Current standard therapeutic measures include the prevention of sudden death by prohibition of competitive sport participation and the implantation of cardioverter-defibrillators if indicated, as well as symptomatic heart failure therapies or cardiac transplantation. There exists no causal therapy for this monogenic autosomal-dominant inherited disorder, so that the focus of current management is on early identification of asymptomatic patients at risk through molecular diagnostic and clinical cascade screening of family members, optimal sudden death risk stratification, and timely initiation of preventative therapies to avoid disease progression to the irreversible adverse myocardial remodeling stage. Genetic diagnosis allowing identification of asymptomatic affected patients prior to clinical disease onset, new imaging technologies, and the establishment of international guidelines have optimized treatment and sudden death risk stratification lowering mortality dramatically within the last decade. However, a thorough understanding of underlying disease pathogenesis, regular clinical follow-up, family counseling, and preventative treatment is required to minimize morbidity and mortality of affected patients. This review summarizes current knowledge about molecular genetics and pathogenesis of HCM secondary to mutations in the sarcomere and provides an overview about current evidence and guidelines in clinical patient management. The overview will focus on clinical staging based on disease mechanism allowing timely initiation of preventative measures. An outlook about so far experimental treatments and potential for future therapies will be provided.

INDUCED PLURIPOTENT STEM CELLS FOR MODELLING ENERGETIC ALTERATIONS IN HYPERTROPHIC CARDIOMYOPATHY

Hypertrophic cardiomyopathy (HCM) is one of the most commonly inherited cardiac disorders that manifests with increased ventricular wall thickening, cardiomyocyte hypertrophy, disarrayed myofibers and interstitial fibrosis. The major pathophysiological features include, diastolic dysfunction, obstruction of the left ventricular outflow tract and cardiac arrhythmias. Mutations in genes that encode mostly for sarcomeric proteins have been associated with HCM but, despite the abundant research conducted to decipher the molecular mechanisms underlying the disease, it remains unclear as to how a primary defect in the sarcomere could lead to secondary phenotypes such as cellular hypertrophy. Mounting evidence suggests energy deficiency could be an important contributor of disease pathogenesis as well. Various animal models of HCM have been generated for gaining deeper insight into disease pathogenesis, however species variation between animals and humans, as well as the limited availability of human myocardial samples, has encouraged researchers to seek alternative 'humanized' models. Using induced pluripotent stem cells (iPSCs), human cardiomyocytes (CMs) have been generated from patients with HCM for investigating disease mechanisms. While these HCM-iPSC models demonstrate most of the phenotypic traits, it is important to ascertain if they recapitulate all pathophysiological features, especially that of energy deficiency. In this review we discuss the currently established HCM-iPSC models with emphasis on altered energetics.

Prognostic predictive value of TLR4 polymorphisms in Han Chinese population with hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most common genetic cardiac disease and is an important cause of sudden death in patients of all ages. The aim of this study was to find out whether Toll-like receptor-4 (TLR4) polymorphism is associated with HCM. To explore the association between TLR4 gene polymorphisms and HCM, 486 HCM patients and 214 healthy controls were enrolled in a case-control study of Chinese Han population. Two single nucleotide polymorphisms (SNPs) in the promoter region of TLR4 gene, -728G > C (rs11536865) and -2081G > A (rs10983755), were genotyped by PCR restriction fragment length polymorphism (PCR-RFLP). The associations between TLR4 SNPs and overall survival (OS) of HCM patients were analyzed by the Kaplan-Meier estimation method and Cox proportional hazards regression analysis. Serum TLR4 level was determined by ELISA. Our results showed that the C allelic frequency of -728G > C and A allelic frequency of -2081G > A were higher in HCM patients than those in controls (P < 0.001). The ratios of genotype frequencies for both SNPs were associated with HCM susceptibility under three genetic models (P < 0.01). Two SNPs were also associated with the OS in HCM patients (P < 0.001). The CC genotype of -728G > C and AA genotype of -2081G > A were associated with poor prognosis of HCM (P < 0.001). Moreover, HCM patients had a higher serum TLR4 level compared with the controls (242.6 pg/ml versus 135.7 pg/ml, P = 0.027). In addition, significant associations were observed between CC genotype of -728G > C or AA genotype of -2081G > A and plasma TLR4 level (P < 0.01). The results of this study indicated that TLR4 polymorphisms may be a genetic susceptibility factor for HCM in the Han Chinese population.

Myocardial perfusion reserve quantified by cardiac magnetic resonance imaging is associated with late gadolinium enhancement in hypertrophic cardiomyopathy

Late gadolinium enhancement (LGE) with cardiac magnetic resonance (CMR) imaging has demonstrated the capability of stratifying hypertrophic cardiomyopathy (HCM). Stress perfusion test of CMR can quantify myocardial perfusion reserve (MPR), but its clinical role is not determined. The purpose of this study was to investigate the relationship between MPR and LGE in patients with HCM. A total of 61 consecutive cases underwent complete evaluation with electrocardiography and CMR [cine imaging, coronary MR angiography (MRA), and stress perfusion testing with LGE]. HCM cases were diagnosed by the Japanese conventional guideline prior to this CMR study. Mild LVH was defined as more than 13 mm in maximum LV wall thickness at end diastole on the cine imaging of the CMR. MPR was calculated as the ratio of stress/rest myocardial blood flow using an intensity curve on the stress perfusion test. Cases with ischemic heart disease were excluded from the study based on clinical history and coronary MRA. There were 37 HCM and 24 mild LVH cases (average age: 60.5 ± 10.9 vs. 64.8 ± 10.8; male: 62.2 vs. 75.0%, respectively, non-significant). MPR in HCM was lower than in LVH (1.5 ± 0.5 vs. 2.2 ± 0.9, p < 0.001) and normal subjects (2.4 ± 0.9, p < 0.001). MPR in HCM with LGE (N = 34) was lower than in HCM without LGE (N = 3) (1.4 ± 0.5 vs. 2.1 ± 0.2, p = 0.014). Multiple regression analysis verified that LGE was the strongest predictor of MPR among multiple clinical parameters, including LVH, LV dysfunction (ejection fraction < 50%), and the presence of negative T wave (p < 0.001). MPR was impaired in HCM with LGE compared with HCM without LGE. The clinical role of MPR on CMR needs to be clarified by further research.

Surgical treatment for hypertrophic cardiomyopathy: a historical perspective

Our understanding of hypertrophic cardiomyopathy (HCM) as a disease entity has increased dramatically over the last half century. There has been a concerted effort by several surgical groups to develop operative techniques to relieve left ventricular outflow tract (LVOT) obstruction and alleviate symptoms. This paper traces the development of transaortic septal myectomy, the current gold standard therapy for relief of LVOT obstruction, in symptomatic patients refractory to medical treatment. In addition, we introduce newer methods for myectomy that have expanded the role of surgery in patients with various forms of HCM.

Hypertrophic obstructive cardiomyopathy: the Mayo Clinic experience

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is a primary myocardial disease characterized by left ventricular hypertrophy in the absence of other etiologies. Clinical presentation may vary from asymptomatic to sudden cardiac death. Medical treatment is the first-line therapy for symptomatic patients. Extended left ventricular septal myectomy is the procedure of choice if medical treatment is unsuccessful or intolerable.

MAYO CLINIC EXPERIENCE

More than 3,000 patients have had septal myectomy for HCM at the Mayo Clinic (MN, USA) from 1993 to 2016. Risk of hospital death after isolated septal myectomy for obstructive HCM is <1% and is similar to the risk of operation for elective mitral valve repair. Complications, such as complete heart block requiring permanent pacemaker, are uncommon (2%), although partial or complete left bundle branch block is a frequent finding on the postoperative ECG. Relief of left ventricular outflow tract (LVOT) obstruction with septal myectomy dramatically improves symptoms and exercise capacity in symptomatic patients with obstructive HCM. More than 90% of severely symptomatic patients have improvement by at least two functional classes, and reduction of outflow gradients by myectomy decreases or eliminates symptoms of dyspnea, angina and/or syncope. Basal obstruction with systolic anterior motion (SAM) is treated by transaortic myectomy. The transapical approach was applied in 115 patients with obstructive midventricular and apical variants of HCM between 1993 and 2012. All patients with midventricular obstruction had gradient relief and none developed an apical aneurysm or ventricular septal defect. Recurrent obstruction after satisfactory myectomy was rare.

CONCLUSIONS

Septal myectomy effectively and definitively relieves LVOT obstruction and cardiac symptoms in patients with obstructive HCM. In experienced centers, early mortality for isolated septal myectomy is less than 1%, and overall results are excellent and continue to improve in the current era.

Results of surgical septal myectomy for obstructive hypertrophic cardiomyopathy: the Tufts experience

BACKGROUND

For over 50 years, surgical septal myectomy has been the preferred treatment for drug-refractory heart failure symptoms in patients with obstructive hypertrophic cardiomyopathy (HCM). Over this time in the United States, the majority of myectomy operations have been performed in a small number of select referral centers.

METHODS

We have taken the opportunity to report results from the relatively new Tufts HCM Center and surgical program, incorporated 13 years ago, during which 507 myectomies (52±14 years of age; 56% male) were performed by one cardiothoracic surgeon, Dr. Hassan Rastegar.

RESULTS

Resting left ventricular (LV) outflow gradients were reduced from 56±42 mmHg preoperatively to 1.2±6.8 mmHg on most recent echocardiogram 2.0±2.5 years after surgery, and 94% of patients showed clinical improvement to NYHA functional class I or II. The first 200 myectomies were performed without mortality or major complications. Among all patients, 30-day mortality rate was 0.8%. Over follow-up of 3.2±2.8 years, 11 patients died (four due to HCM causes) with long-term survival after myectomy of 94% at 5 years (95% CI: 89-96%) and 91% at 10 years (95% CI: 84-95%), which did not differ from the age- and gender-matched general U.S. population (log-rank P=0.9).

CONCLUSIONS

This experience demonstrates that, with the appropriate support, new HCM surgical programs can provide patients successful relief of outflow obstruction, extended longevity and restored of quality of life.

Hypertrophic cardiomyopathy in children

Hypertrophic cardiomyopathy (HCM) occurs in 1 of 500 adults and is considered to be one of the most common causes of death in young people under 35 years of age. Children with HCM are usually asymptomatic and the overall annual mortality beyond the first year of life is 1%. Septal myectomy is safe and effective in children with obstructive HCM and published data shows improved late survival compared to untreated HCM. Patient selection and surgical expertise remain critical components to ensuring successful outcomes of septal myectomy, particularly when considering prophylactic myectomy in a seemingly asymptomatic patient.

Surgical management of atrial fibrillation at the time of septal myectomy

Atrial fibrillation (AF) may appear during the natural clinical course of hypertrophic cardiomyopathy (HCM). It is regarded as a complication of HCM and is a marker of advanced disease. AF is more likely to occur in untreated, obstructive HCM. Unfortunately, this represents a turning point that puts patients at increased risk of further disability, stroke and death. The presence of obstruction is an indication to proceed with septal myectomy to improve or resolve symptoms by ameliorating diastolic dysfunction. If the patient has concomitant AF, a Maze procedure should be added to the septal myectomy. This combined operation yields excellent hemodynamic benefits and potentially decreases the risk of thromboembolic events.

Novel trigenic CACNA1C/DES/MYPN mutations in a family of hypertrophic cardiomyopathy with early repolarization and short QT syndrome

Background

Hypertrophic cardiomyopathy (HCM) patients with early repolarization (ER) pattern are at higher risk of ventricular arrhythmia, yet the genetic background of this situation has not been well investigated. Here we report novel trigenic mutations detected in a Chinese family of obstructive HCM with ER and short QT syndrome (SQTS).

Methods

Proband and family members underwent detailed medical assessments. DNAs were extracted from peripheral blood leukocytes for genetic screening with next generation method. The functional characterization of the mutation was conducted in TSA201 cells with patch-clamp experiment.

Results

The proband was a 52-year-old male who had a ER pattern ECG in inferioral-lateral leads with atrioventricular block and QTc of 356 ms. He also suffered from severe left ventricular hypertrophy and dysfunction. Targeted sequencing revealed trigenic mutations: c.700G>A/p.E234K in DES, c.2966G>A/p.R989H in MYPN, and c.5918G>C/p.R1973P in CACNA1C. All mutations were also detected in his daughter with ER and mild myocardium hypertrophy. The CACNA1C-R1973P mutation caused significant reduction (68.4%) of I_Ca compared to CACNA1C-WT (n = 14 and 14, P < 0.05). The computer modeling showed that all 3 mutations were highly disease-causing. The proband received the CRT-D (cardiac resynchronizing therapy) implantation, which lowered the left ventricular outflow tract gradient (LVOTG, 124 mmHg pre vs. 27 mmHg post) and restored the LV function (LVEF 40% pre vs. 63% post).

Conclusions

The study reveals a novel CACNA1C mutation underlying the unique ER pattern ECGs with SQTS. It also shows the rare trigenic mutations are the pathogenic substrates for the complicated clinical manifestation in HCM patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-017-1180-1) contains supplementary material, which is available to authorized users.

Altered myocyte contractility and calcium homeostasis in alpha-myosin heavy chain point mutations linked to familial dilated cardiomyopathy

Mutations in the human cardiac motor protein beta-myosin heavy chain (βMHC) have been long recognized as a cause of familial hypertrophic cardiomyopathy. Recently, mutations (P830L and A1004S) in the less abundant but faster isoform alpha-myosin heavy chain (αMHC) have been linked to dilated cardiomyopathy (DCM). In this study, we sought to determine the cellular contractile phenotype associated with these point mutations. Ventricular myocytes were isolated from 2 month male Sprague Dawley rats. Cells were cultured in M199 media and infected with recombinant adenovirus containing the P830L or the A1004S mutant human αMHC at a MOI of 500 for 18 h. Uninfected cells (UI), human βMHC (MOI 500, 18 h), and human αMHC (MOI 500, 18 h) were used as controls. Cells were loaded with fura-2 (1 μM, 15 min) after 48 h. Sarcomere shortening and calcium transients were recorded in CO₂ buffered M199 media (36°±1 C) with and without 10 nM isoproterenol (Iso). The A1004S mutation resulted in decreased peak sarcomere shortening while P830L demonstrated near normal shortening kinetics at baseline. In the presence of Iso, the A1004S sarcomere shortening was identical to the βMHC shortening while the P830L was identical to the αMHC control. All experimental groups had identical calcium transients. Despite a shared association with DCM, the P830L and A1004S αMHC mutations alter myocyte contractility in completely different ways while at the same preserving peak intracellular calcium.

Advanced Imaging of Athletes: Added Value of Coronary Computed Tomography and Cardiac Magnetic Resonance Imaging

Cardiac magnetic resonance imaging and cardiac computed tomographic angiography have become important parts of the armamentarium for noninvasive diagnosis of cardiovascular disease. Emerging technologies have produced faster imaging, lower radiation dose, improved spatial and temporal resolution, as well as a wealth of prognostic data to support usage. Investigating true pathologic disease as well as distinguishing normal from potentially dangerous is now increasingly more routine for the cardiologist in practice. This article investigates how advanced imaging technologies can assist the clinician when evaluating all athletes for pathologic disease that may put them at risk.

Factors Associated with Uptake of Genetics Services for Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a common cardiovascular disorder with variable expressivity and incomplete penetrance. Clinical guidelines recommend consultation with a genetics professional as part of an initial assessment for HCM, yet there remains an underutilization of genetics services. We conducted a study to assess factors associated with this underutilization within the framework of the Health Belief Model (HBM). An online survey was completed by 306 affected individuals and at risk family members. Thirty-seven percent of individuals (113/306) had visited a genetics professional for reasons related to HCM. Genetic testing was performed on 53 % (162/306). Individuals who had undergone testing were more likely to have seen a genetics professional (p < 0.001), had relatives with an HCM diagnosis (p = 0.002), and have a known familial mutation (p < 0.001). They were also more likely to agree that genetic testing would satisfy their curiosity (p < 0.001), provide reassurance (p < 0.001), aid family members in making healthcare decisions (p < 0.001), and encourage them to engage in a healthier lifestyle (p = 0.002). The HBM components of cues to action and perceived benefits and barriers had the greatest impact on uptake of genetic testing. In order to ensure optimal counseling and care for individuals and families with HCM, awareness and education around HCM and genetic services should be promoted in both physicians and patients alike.

The role of magnetic resonance imaging in hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most common inheritable cardiac disorder, with an estimated prevalence of 1:500 in the general population. Most cases of HCM are phenotypically expressed in adolescence or early adulthood but age-related penetrance with certain phenotypes is increasingly recognized. Clinical manifestations of HCM are usually the result of systolic and/or diastolic dysfunction, left ventricular outflow tract (LVOT) obstruction, arrhythmias and sudden cardiac death (SCD). In recent years magnetic resonance imaging (MRI) has become established as an important tool for the evaluation of suspected HCM as it can reliably establish the diagnosis, help distinguish HCM from other causes of left ventricular hypertrophy (LVH) and identify those patients at greatest risk of SCD. This article reviews the current status of MRI in the evaluation of the HCM patient including imaging protocols, disease characterization and the emerging role of MRI for risk stratification and proband screening.

Relation of late gadolinium enhancement in cardiac magnetic resonance on the diastolic volume recovery of left ventricle with hypertrophic cardiomyopathy

OBJECTIVE

The purpose of the study was to investigate the influence of late gadolinium enhancement (LGE) on the diastolic volume recovery of left ventricle in patients with hypertrophic cardiomyopathy (HCM).

METHODS

Twenty-four HCM patients were studied through report-card 4.0. The presence or absence of late gadolinium enhancement was recorded according to a standardized methodology with a threshold value of six standard deviations above background. The LGE positive and negative groups were correlated to left ventricular end diastolic volume index (EDVI), left ventricular mass, left ventricular ejection fraction (EF), peak filling rate (PFR), peak ejecting rate (PER), normalized peak filling or ejecting rate (NPFR or NPER), time to peak filling or ejecting rate (TPFR or TPER), and diastolic volume recovery (DVR).

RESULTS

PFR, NPFR, SV, SVI, EF, CO, CI, FS in LGE positive group were lower than LGE negative group, DVR10-40, DVR100, end systolic volume (ESV), end systolic volume index (ESVI), ESD were higher in LGE positive group, and the differences were statistically significant. The average LGE mass (ROI, region of interest) was 20.78 g, about 13.67% of left ventricle mass in LGE positive HCM group. Pearson correlation was noted between the LGE percent (ROI%) and ESV (0.692, P<0.05), ROI% and EF (-0.718, P<0.05), ROI% and PFR (-0.534, P<0.05), DVR20-40 (0.547, 0.544, 0.906, P<0.05) etc. The correlation between ROI% and DVR40 was best (0.906, P<0.05), and the correlation between ROI% and ESVI, ROI% and EF were both bigger than 0.7, showed the correlation was good.

CONCLUSIONS

In addition to common quotas used to assess the structure and function of left ventricle in HCM, volume-time curve parameters may have potential to evaluate cardiac function in HCM. The correlation between DVR generated from volume-time curve with LGE was good, and may be a marker of effect of enhancement/scar tissue on diastolic function.

Hypertrophic cardiomyopathy associated Lys104Glu mutation in the myosin regulatory light chain causes diastolic disturbance in mice

We have examined, for the first time, the effects of the familial hypertrophic cardiomyopathy (HCM)-associated Lys104Glu mutation in the myosin regulatory light chain (RLC). Transgenic mice expressing the Lys104Glu substitution (Tg-MUT) were generated and the results were compared to Tg-WT (wild-type human ventricular RLC) mice. Echocardiography with pulse wave Doppler in 6month-old Tg-MUT showed early signs of diastolic disturbance with significantly reduced E/A transmitral velocities ratio. Invasive hemodynamics in 6month-old Tg-MUT mice also demonstrated a borderline significant prolonged isovolumic relaxation time (Tau) and a tendency for slower rate of pressure decline, suggesting alterations in diastolic function in Tg-MUT. Six month-old mutant animals had no LV hypertrophy; however, at >13months they displayed significant hypertrophy and fibrosis. In skinned papillary muscles from 5 to 6month-old mice a mutation induced reduction in maximal tension and slower muscle relaxation rates were observed. Mutated cross-bridges showed increased rates of binding to the thin filaments and a faster rate of the power stroke. In addition, ~2-fold lower level of RLC phosphorylation was observed in the mutant compared to Tg-WT. In line with the higher mitochondrial content seen in Tg-MUT hearts, the MUT-myosin ATPase activity was significantly higher than WT-myosin, indicating increased energy consumption. In the in vitro motility assay, MUT-myosin produced higher actin sliding velocity under zero load, but the velocity drastically decreased with applied load in the MUT vs. WT myosin. Our results suggest that diastolic disturbance (impaired muscle relaxation, lower E/A) and inefficiency of energy use (reduced contractile force and faster ATP consumption) may underlie the Lys104Glu-mediated HCM phenotype.