Hypertrophic Cardiomyopathy

Hypertrophic obstructive cardiomyopathy: review of surgical treatment

Hypertrophic cardiomyopathy ranks among the most common congenital cardiac diseases, affecting up to 1 in 200 of the general population. When it causes left ventricular outflow tract obstruction, treatment is guided to reduce symptoms and the risk of sudden cardiac death. Pharmacologic therapy is the first-line treatment, but when it fails, surgical myectomy or percutaneous ablation of the hypertrophic myocardium are the standard therapies to eliminate subaortic obstruction. Both surgical myectomy and percutaneous ablation are proven safe and effective treatments; however, myectomy is the gold standard with a significantly lower complication rate and more complete and lasting reduction of left ventricular outflow tract obstruction.

Left ventricular systolic function changes in hypertrophic cardiomyopathy patients detected by the strain of different myocardium layers and longitudinal rotation

BACKGROUND

Impairment of left ventricular (LV) longitudinal function has an important role in hypertrophic cardiomyopathy (HCM). This research investigated an association between the longitudinal strain of different myocardial layers, longitudinal rotation and the LV systolic function of HCM patients.

METHODS

The research was performed on 36 HCM patients and 36 healthy subjects. The peak systolic longitudinal strain of the subendocardial, midmyocardial, and subepicardial layers was measured using 2-dimensional speckle tracking echocardiography (2D-STE). The apical long-axis and 4- and 2- chamber views were acquired via 2D Doppler echocardiography. The curve of the longitudinal rotation was traced at 17 timepoints in the analysis of 2 cardiac cycles.

RESULTS

Compared with healthy subjects, in HCM patients regional LV peak systolic longitudinal strain was less, not only in hypertrophied LV myocardium, but also in non-hypertrophied myocardium. The rotational degrees of the midmyocardial-septal, apex, and lateral wall of HCM patients were significantly different from that of normal subjects, as follows. In HCM patients, clockwise longitudinal rotation was found. The interventricular septum thickness at end-diastole positively correlated with the peak longitudinal systolic strain of the subendocardial, the midmyocardial, and the subepicardial layers. The area under ROC curve values for subendocardial, midmyocardial and subepicardial layers in HCM patients were 0.923, 0.938, 0.948.

CONCLUSION

In HCM patients, the longitudinal function was damaged, even with normal LV ejection fraction. The peak longitudinal systolic strain of the subendocardial, midmyocardial, and subepicardial layers, and the longitudinal rotation detected by 2D-STE, are very sensitive predictors of systolic function in patients with HCM.

Troponins, intrinsic disorder, and cardiomyopathy

Cardiac troponin is a dynamic complex of troponin C, troponin I, and troponin T (TnC, TnI, and TnT, respectively) found in the myocyte thin filament where it plays an essential role in cardiac muscle contraction. Mutations in troponin subunits are found in inherited cardiomyopathies, such as hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM). The highly dynamic nature of human cardiac troponin and presence of numerous flexible linkers in its subunits suggest that understanding of structural and functional properties of this important complex can benefit from the consideration of the protein intrinsic disorder phenomenon. We show here that mutations causing decrease in the disorder score in TnI and TnT are significantly more abundant in HCM and DCM than mutations leading to the increase in the disorder score. Identification and annotation of intrinsically disordered regions in each of the troponin subunits conducted in this study can help in better understanding of the roles of intrinsic disorder in regulation of interactomes and posttranslational modifications of these proteins. These observations suggest that disease-causing mutations leading to a decrease in the local flexibility of troponins can trigger a whole plethora of functional changes in the heart.

The Genetic and Molecular Bases for Hypertrophic Cardiomyopathy: The Role for Calcium Sensitization

Hypertrophic cardiomyopathy (HCM) affects millions of people around the world as one of the most common genetic heart disorders and leads to cardiac ischemia, heart failure, dysfunction of other organ systems, and increased risk for sudden unexpected cardiac deaths. HCM can be caused by single-point mutations, insertion or deletion mutations, or truncation of cardiac myofilament proteins. The molecular mechanism that leads to disease progression and presentation is still poorly understood, despite decades of investigations. However, recent research has made dramatic advances in the understanding of HCM disease development. Studies have shown that increased calcium sensitivity is a universal feature in HCM. At the molecular level, increased crossbridge force (or power) generation resulting in hypercontractility is the prominent feature. Thus, calcium sensitization/hypercontractility is emerging as the primary stimulus for HCM disease development and phenotypic expression. Cross-bridge inhibition has been shown to halt HCM presentation, and myofilament desensitization appears to reduce lethal arrhythmias in animal models of HCM. These advances in basic research will continue to deepen the knowledge of HCM pathogenesis and are beginning to revolutionize the management of HCM.

Tp-e interval and Tp-e/QTc ratio as novel surrogate markers for prediction of ventricular arrhythmic events in hypertrophic cardiomyopathy

OBJECTIVE

Hypertrophic cardiomyopathy (HCM) as a common genetic heart disease characterized by ventricular hypertrophy and myocardial fibrosis is significantly associated with a higher risk of fatal ventricular arrhythmic events (VAEs). We aimed to assess the interval between the peak and the end of the electrocardiographic T wave (Tp-e) and Tp-e/corrected QT (QTc) ratio as candidate markers of ventricular arrhythmias in patients with HCM.

METHODS

In this single-center, prospective study, a total of 66 patients with HCM and 88 controls were enrolled. The patients were divided into two groups: those with VAEs (n=26) and those without VAEs (n=40). Tp-e interval and Tp-e/QTc ratio were measured using a 12-lead electrocardiogram.

RESULTS

Tp-e interval was significantly longer and Tp-e/QTc ratio were significantly higher in HCM patients than in the controls. In correlation analysis, maximal left ventricular (LV) thickness also has a significant positive correlation with Tp-e interval (r=0.422, p<0.001) and Tp-e/QTc ratio (r=0.348, p<0.001). Finally, multivariable regression analysis showed that a history of syncope, Tp-e interval [OR (odds ratio): 1.060; 95% confidence interval (CI): 1.005-1.117); p=0.012], Tp-e/QTc ratio (OR: 1.148; 95% CI: 1.086-1.204); p=0.049], and maximal LV thickness were independent predictors of VAEs in patients with HCM.

CONCLUSION

Our findings suggested that prolonged Tp-e interval and increased Tp-e/QTc ratio may be good surrogate markers for the prediction of VAEs in HCM.

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

Hypertrophic cardiomyopathy (HCM) is a heterogeneous group of diseases related to sarcomere gene mutations exhibiting heterogeneous phenotypes with an autosomal dominant mendelian pattern of inheritance. The disorder is characterized by diverse phenotypic expressions and variable natural progression, which may range from dyspnea and/or syncope to sudden cardiac death. It is found across all racial groups and is associated with left ventricular hypertrophy in the absence of another systemic or cardiac disease. The management of HCM is based on a thorough understanding of the underlying morphology, pathophysiology, and clinical course. Imaging findings of HCM mirror the variable expressivity and penetrance heterogeneity, with the added advantage of diagnosis even in cases where a specific mutation may not yet be found. The diagnostic information obtained from imaging varies depending on the specific stage of HCM-phenotype manifestation, including the prehypertrophic, hypertrophic, and later stages of adverse remodeling into the burned-out phase of overt heart failure. However, subtle or obvious, these imaging findings become critical components in diagnosis, management, and follow-up of HCM patients. Although diagnosis of HCM traditionally relies on clinical assessment and transthoracic echocardiography, recent studies have demonstrated increased utility of multidetector computed tomography (CT) and particularly cardiac magnetic resonance (MR) imaging in diagnosis, phenotype differentiation, therapeutic planning, and prognostication. In this article, we provide an overview of the genetics, pathophysiology, and clinical manifestations of HCM, with the spectrum of imaging findings at MR imaging and CT and their contribution in diagnosis, risk stratification, and therapy.

Cardiomyopathies and anaesthesia

Cardiomyopathy is considered as a heart muscle disease of multiple aetiologies, unlike other cardiac diseases related to a definitive pathophysiology. With more and more research and with the advent of genetic analysis pin pointing the disease causing mutations, causative factors have been defined and classifications and definitions have changed over time. Patients with these conditions present to anaesthesiologists in elective and emergency situations, placement of automated internal cardioverter defibrillator (AICD) devices or biventricular pacing but may also be diagnosed at anaesthetic pre-assessment. We describe cardiomyopathies such as dilated cardiomyopathy, hypertrophic cardiomyopathy, post-partum cardiomyopathy and Takotsubo cardiomyopathy in brief and their anaesthetic management.

Sex-related differences in the associations between plasma free fatty acid levels and clinical features in patients with hypertrophic cardiomyopathy

Background

Previous studies have indicated that inefficient energy utilization may play a pivotal role in hypertrophic cardiomyopathy (HCM). However, whether plasma free fatty acid (FFA), a main energy substrate of heart, has an effect on HCM remains unclear. Besides, several studies have suggested sex-related differences in HCM features and FFA metabolism. Here, we aimed to explore the association between plasma FFA levels and HCM and potential effects of sex on this relation.

Methods

A total of 412 patients (age 47.8 ± 12.7 years, 243 males (59.0%)) with HCM were recruited. Complete medical history was collected. Echocardiography and cardiovascular magnetic resonance imaging (CMRI) were performed. Fasting plasma FFA was determined by clinical laboratory. Left ventricular mass (LVM), maximum wall thickness (MWT), and left atrium diameter (LAD) were assessed with CMRI.

Results

The median FFA levels were 0.38 (interquartile range (IQR) 0.27–0.52) mmol/L in men and 0.40 (IQR 0.30–0.59) mmol/L in women. The FFA levels were significantly lower in men compared with those in women (p = 0.005). Compared with women, men had greater LVM index (LVMI) (96.8 ± 37.6 vs. 78.6 ± 31.5 g/m², p < 0.001). FFA levels in male patients correlated positively with LVM, LVMI, LAD, cholesterol levels, high-density lipoprotein-cholesterol (HDL-C) levels, heart rate, and systolic blood pressure (SBP). However, none of these variables were significantly associated with sqrt (FFA) in female patients except a borderline correlation of LAD (p = 0.050). Multiple linear regression analysis was performed in male patients and revealed that HDL-C (β = 0.191, p = 0.002), heart rate (β = 0.182, p = 0.004), SBP (β = 0.167, p = 0.007), LVMI (β = 0.132, p = 0.032), and LAD (β = 0.165, p = 0.009) were independently associated with increasing FFA levels.

Conclusions

In patients with HCM, LVMI, LAD, HDL-C, SBP, and heart rate were independently associated with increasing plasma FFA levels in males, whereas not in females. These results suggest that sex may affect the pathogenesis of HCM through influencing FFA metabolism. And these sex-related differences should be taken into account in therapeutic approaches to influence myocardial FFA metabolism in HCM.

Recent Advances in the Molecular Genetics of Familial Hypertrophic Cardiomyopathy in South Asian Descendants

The South Asian population, numbered at 1.8 billion, is estimated to comprise around 20% of the global population and 1% of the American population, and has one of the highest rates of cardiovascular disease. While South Asians show increased classical risk factors for developing heart failure, the role of population-specific genetic risk factors has not yet been examined for this group. Hypertrophic cardiomyopathy (HCM) is one of the major cardiac genetic disorders among South Asians, leading to contractile dysfunction, heart failure, and sudden cardiac death. This disease displays autosomal dominant inheritance, and it is associated with a large number of variants in both sarcomeric and non-sarcomeric proteins. The South Asians, a population with large ethnic diversity, potentially carries region-specific polymorphisms. There is high variability in disease penetrance and phenotypic expression of variants associated with HCM. Thus, extensive studies are required to decipher pathogenicity and the physiological mechanisms of these variants, as well as the contribution of modifier genes and environmental factors to disease phenotypes. Conducting genotype-phenotype correlation studies will lead to improved understanding of HCM and, consequently, improved treatment options for this high-risk population. The objective of this review is to report the history of cardiovascular disease and HCM in South Asians, present previously published pathogenic variants, and introduce current efforts to study HCM using induced pluripotent stem cell-derived cardiomyocytes, next-generation sequencing, and gene editing technologies. The authors ultimately hope that this review will stimulate further research, drive novel discoveries, and contribute to the development of personalized medicine with the aim of expanding therapeutic strategies for HCM.

Harmful effect of epinephrine on postreperfusion syndrome in an elderly liver transplantation recipient with sigmoid ventricular septum: A case report

INTRODUCTION

As a common morphological change of aging heart, sigmoid ventricular septum is frequently found during routine preoperative evaluation, but often disregarded because of its little clinical importance. However, in this report, we describe a 70-year old patient with sigmoid ventricular septum who developed severe hemodynamic deterioration during liver transplantation because of its unique morphology of heart.

METHODS

During the course of reperfusion of the graft, patient's hemodynamics were closely monitored using transesophageal echocardiography.

RESULTS

Immediately after graft reperfusion, epinephrine was given as a treatment of choice for postreperfusion syndrome. Surprisingly, however, hemodynamic derangement persisted and became even worse. Intraoperative transesophageal echocardiography revealed left ventricular outflow tract obstruction resulting from systolic anterior motion of the mitral valve leaflet. Therefore, the patient was treated with phenylephrine and fluid bolus under the guidance of transesophageal echocardiography.

CONCLUSION

As more elderly recipient present for liver transplantation surgery nowadays, left ventricular outflow tract obstruction should always be considered as a possible cause for hemodynamic instability during reperfusion period. In addition, transesophageal echocardiography is a useful tool for both diagnosis of hemodynamic derangement and guidance for appropriate management during liver transplantation surgery.

Identification of novel biomarker candidates for hypertrophic cardiomyopathy and other cardiovascular diseases leading to heart failure

In-depth proteome discovery analysis represents new strategy in an effort to identify novel reliable specific protein markers for hypertrophic cardiomyopathy and other life threatening cardiovascular diseases. To systematically identify novel protein biomarkers of cardiovascular diseases with high mortality we employed an isobaric tag for relative and absolute quantitation (iTRAQ) proteome technology to make comparative analysis of plasma samples obtained from patients suffering from non-obstructive hypertrophic cardiomyopathy, stable dilated cardiomyopathy, aortic valve stenosis, chronic stable coronary artery disease and stable arterial hypertension. We found 128 plasma proteins whose abundances were uniquely regulated among the analyzed cardiovascular pathologies. 49 of them have not been described yet. Additionally, application of statistical exploratory analyses of the measured protein profiles indicated the relationship in pathophysiology of the examined cardiovascular pathologies.

A Long Term Follow-up Study of Carriers of Hypertrophic Cardiomyopathy Mutations

BACKGROUND

Adults who test positive for a mutation associated with the development of hypertrophic cardiomyopathy (HCM) but who have not manifested left ventricular hypertrophy (LVH) at the time of that diagnosis are now commonly identified in the era of genetic testing. There are little published data, however, on the long-term outlook for these phenotypically normal gene carriers.

METHODS

Fifteen genotype positive/LVH negative patients with HCM were identified, seven of which were children when first diagnosed as gene carriers. Fourteen were followed up with clinical examinations, electrocardiography and echocardiography to determine if their clinical status had changed over time. Measurements included electrocardiographic changes, changes in wall thickness, diastolic function and global longitudinal stain.

RESULTS

Ten participants were followed up for a total of 18 years, two for a total of 17 years, one for 11 years and one for 8 years. In addition, magnetic resonance imaging (MRI) studies were performed on 11 participants. Eleven participants carried a mutation for the MYBPC3 gene and three carried a mutation for the MYH7 gene. One patient, an adult at the time of initial investigation, developed phenotypic features of HCM on echocardiography and MRI, one an increase in wall thickness diagnostic for HCM only on MRI and another to be borderline for HCM on MRI.

CONCLUSION

Hypertrophic cardiomyopathy can develop in adult life in carriers who may be negative for LVH at the time of gene diagnosis and warrants periodic supervision of carriers throughout their lives.

The role of intraoperative transesophageal echocardiographic monitoring in a patient with hypertrophic cardiomyopathy undergoing laparoscopic surgery

Hypertrophic cardiomyopathy (HCM) presents a significant perioperative challenge. Anesthetic drugs, patient positioning, and surgical technique can provoke worsening left ventricular outflow tract obstruction and hemodynamic deterioration. In this case report, we present the perioperative management of a 70-year-old male with a history of HCM who underwent a robotic laparoscopic prostatectomy. Discussion focuses on the utilization of echocardiographic guidance in the care of patients with HCM undergoing noncardiac surgery, as well as the pathophysiology of laparoscopic insufflation and its effects on left ventricular outflow tract obstruction in HCM.

Adenosine triphosphate-sensitive potassium channels and cardiomyopathies (Review)

Cardiomyopathies have been indicated to be one of the leading causes of heart failure. Though it was indicated that genetic defects, viral infection and trace element deficiency were among the causes of cardiomyopathy, the etiology has remained to be fully elucidated. Cardiomyocytes require large amounts of energy to maintain their normal biological functions. Adenosine triphosphate-sensitive potassium channels (KATP), composed of inward-rectifier potassium ion channel and sulfonylurea receptor subunits, are present on the cell surface and mitochondrial membrane of cardiac muscle cells. As metabolic sensors sensitive to changes in intracellular energy levels, KATP adapt electrical activities to metabolic challenges, maintaining normal biological functions of myocytes. It is implied that malfunctions, mutations and altered expression of KATP are associated with the pathogenesis of conditions including c hypertrophy, diabetes as well as dilated, ischemic and endemic cardiomyopathy. However, the current knowledge is only the tip of the iceberg and the roles of KATP in cardiomyopathies largely remain to be elucidated in future studies.