Contemporary Therapies and Future Directions in the Management of Hypertrophic Cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is a genetic disorder caused by pathogenic variants in sarcomeric genes, leading to left ventricular hypertrophy and complex phenotypic heterogeneity. While HCM is the most common inherited cardiomyopathy, pharmacological treatment options have previously been limited and were predominantly directed towards symptom control owing to left ventricular outflow obstruction. These therapies, including beta blockers, calcium channel blockers, and disopyramide, have not been shown to affect the natural history of the disease, which is of particular concern for younger patients who have an increased lifetime risk of experiencing arrhythmias, heart failure, and sudden cardiac death. Increased knowledge of the genetic mechanisms underlying this disease in recent years has led to the development of targeted, potentially disease-modifying therapies for both obstructive and nonobstructive phenotypes that may help to prevent or ameliorate left ventricular hypertrophy. In this review article, we will define the etiology and clinical phenotypes of HCM, summarize the conventional therapies for obstructive HCM, discuss the emerging targeted therapies as well as novel invasive approaches for obstructive HCM, describe the therapeutic advances for nonobstructive HCM, and outline the future directions for the treatment of HCM.

Cardiovascular Characteristics of Patients with Genetic Variation in Desmoplakin (DSP).

BACKGROUND: Variants in the desmoplakin (DSP) gene have been recognized in association with the pathogenesis of arrhythmogenic right ventricular cardiomyopathy (ARVC) for nearly 20 years. More recently, genetic variation in DSP has also been associated with left-dominant arrhythmogenic cardiomyopathy. Data regarding the cardiac phenotypes associated with genetic variation in DSP have been largely accumulated from phenotype-first studies of ARVC. METHODS: We aimed to evaluate the clinical manifestations of cardiac disease associated with variants in DSP through a genotype-first approach employed in the University of Pennsylvania Center for Inherited Cardiovascular Disease registry. We performed a retrospective study of 19 individuals with "pathogenic" or "likely pathogenic" variants in DSP identified by clinical genetic testing. Demographics and clinical characteristics were collected. RESULTS: Among individuals with disease-causing variants in DSP, nearly 40% had left ventricular enlargement at initial assessment. Malignant arrhythmias were prevalent in this cohort (42%) with a high proportion of individuals undergoing primary and secondary prevention implantable cardioverter defibrillator implantation (68%) and ablation of ventricular arrhythmias (16%). Probands also experienced end-stage heart failure requiring heart transplantation (11%). CONCLUSIONS: Our data suggest DSP cardiomyopathy may manifest with a high burden of heart failure and arrhythmic events, highlighting its importance in the pathogenesis of dilated and arrhythmogenic cardiomyopathies. Targeted strategies for diagnosis and risk stratification for DSP cardiomyopathy should be investigated.

Left Ventricular Hypertrophy and Hypertrophic Cardiomyopathy in Adult Solid Organ Transplant Recipients.

BACKGROUND: Hypertrophic cardiomyopathy (HCM) in pediatric solid organ transplant recipients has been reported in association with use of calcineurin inhibitors. However, data on the incidence and prevalence of HCM in adult posttransplant patients are limited. We sought to describe the clinical characteristics of solid organ transplant recipients who were diagnosed with HCM from 2011 to 2021 at a single center. METHODS: Patients who had undergone solid organ transplant and exhibited left ventricular hypertrophy with left ventricular wall thickness ≥13 mm on transthoracic echocardiography were included. Clinical history, pedigree analysis, clinical genetic testing, transthoracic echocardiography, cardiac magnetic resonance imaging, treatment, and follow-up testing results were collected. Categorical variables were described as n (%). Continuous variables were described with medians and interquartile ranges and compared using the Wilcoxon rank-sum and Kruskal-Wallis tests. A 2-sided P < 0.05 was considered statistically significant. RESULTS: Three lung, 5 kidney, and 4 liver transplant recipients from 12 different families were included. Seven patients (58%) did not carry a preexisting diagnosis of hypertension, and none had a history of aortic or subaortic stenosis. A majority of patients exhibited asymmetric septal hypertrophy (67%; medial septal thickness versus left ventricular posterior wall thickness 17 versus 13 mm; P < 0.001) and dynamic left ventricular outflow tract (LVOT) obstruction (58%). All patients were managed long term with calcineurin inhibitors. Clinical genetic testing in 6 patients identified 2 with disease-causing variants in 2 sarcomere genes, myosin binding protein-C and myosin heavy chain 7. Four patients (33%) underwent successful septal reduction therapy for treatment of symptomatic LVOT obstruction. CONCLUSIONS: Symptomatic HCM with dynamic LVOT obstruction can develop in solid organ transplant recipients, and genetic testing can identify individuals with sarcomeric HCM. Medical management and septal reduction therapies are treatment options for severe symptomatic disease.

Applying Shared Decision Making to Sports Participation for a Patient With Hypertrophic Cardiomyopathy.

A patient with hypertrophic cardiomyopathy and a cardio-defibrillator implanted for primary prevention would like to compete on the ski team at his school. This case illustrates how a shared decision-making approach can be applied when counseling patients with hypertrophic cardiomyopathy about exercise and sports participation. (Level of Difficulty: Intermediate.).

Incremental prognostic value of visually estimated coronary artery calcium in patients undergoing positron emission tomography imaging.

OBJECTIVE: Visually estimated coronary artery calcium (VECAC) from chest CT or attenuation correction (AC)/CT obtained during positron emission tomography (PET)-myocardial perfusion imaging (MPI) is feasible. Our aim was to determine the prognostic value of VECAC beyond conventional risk factors and PET imaging parameters, including coronary flow reserve (CFR). METHODS: We analysed 608 patients without known coronary artery disease who underwent PET-MPI between 2012 and 2016 and had AC/CT and/or chest CT images. We used Cox regression to estimate the association of VECAC categories (≤10, 11-400, >400 Agatston units (AU)) with the primary outcome of all-cause death, acute coronary syndrome or stroke (mean follow-up 4.3±1.8 years). C-statistics assessed the relationship between PET parameters and VECAC with the primary outcome. RESULTS: Mean age was 58±11 years, 65% were women and 67% were black. VECAC ≤10, 11-400 and >400 AU was observed in 68%, 12% and 20% of subjects, respectively. Compared with VECAC ≤10, VECAC categories 11-400 (HR 2.25, 95% CI 1.24 to 4.08) and >400 AU (HR 3.05, 95% CI 1.87 to 4.98) were associated with the primary outcome after adjusting for traditional risk factors, MPI findings and CFR. Adding VECAC to a model that included PET-MPI, CFR and clinical risk factors improved the prognostic value for the primary outcomes (c-statistic 0.71 to 0.75 with VECAC, p=0.01). CONCLUSIONS: VECAC is a potent predictor of events beyond traditional risk factors and PET imaging markers, including CFR. These data further support the importance for routine VECAC implementation.

Sarcomere mutation negative hypertrophic cardiomyopathy is associated with ageing and obesity.

BACKGROUND: Despite advances in our understanding of the genetic causes of hypertrophic cardiomyopathy (HCM), a large portion of this patient population do not carry sarcomere gene mutations when screened. It remains largely unknown why patients without sarcomere mutations develop asymmetric myocardial hypertrophy. METHODS: We performed a retrospective analysis of probands with HCM who underwent genetic testing to determine if clinical phenotypes were different depending on sarcomere mutation status. A medical history, three generation family history and clinical phenotyping were performed on 127 probands with HCM. Genetic screening was performed using clinically available HCM genetic testing panels. RESULTS: We found that probands with HCM with pathogenic sarcomere mutations were over three times more likely to have a family history of HCM (66% vs 17%, p<0.0001) and were diagnosed with HCM at a much younger age (32 vs 51 years old, p<0.0001). In contrast, probands with HCM without sarcomere mutations were significantly more obese (body surface area p=0.003, body mass index p=0.04 adjusted for age) and were more likely to present with left ventricular outflow tract obstruction (p=0.0483). CONCLUSION: Patients with sarcomere mutation negative HCM present at an older age and are more obese compared with patients with sarcomere mutation positive HCM. The role of ageing and obesity in asymmetric myocardial hypertrophy warrants further investigation.

Recurrent Left Pleural Effusion Following Left Atrial Appendage Closure With the Watchman Device.

A 75-year-old woman with recent left atrial appendage closure with the Watchman device (Boston Scientific, Natick, Massachusetts) presented with recurrent left pleural effusion. The constellation of chest pain, pericardial effusion, and exudative pleural effusion were suggestive of an inflammatory process precipitated by microperforation of the fixation anchors during the Watchman placement. (Level of Difficulty: Intermediate.).

Alterations in sarcomere function modify the hyperplastic to hypertrophic transition phase of mammalian cardiomyocyte development.

It remains unclear how perturbations in cardiomyocyte sarcomere function alter postnatal heart development. We utilized murine models that allowed manipulation of cardiac myosin-binding protein C (MYBPC3) expression at critical stages of cardiac ontogeny to study the response of the postnatal heart to disrupted sarcomere function. We discovered that the hyperplastic to hypertrophic transition phase of mammalian heart development was altered in mice lacking MYBPC3 and this was the critical period for subsequent development of cardiomyopathy. Specifically, MYBPC3-null hearts developed evidence of increased cardiomyocyte endoreplication, which was accompanied by enhanced expression of cell cycle stimulatory cyclins and increased phosphorylation of retinoblastoma protein. Interestingly, this response was self-limited at later developmental time points by an upregulation of the cyclin-dependent kinase inhibitor p21. These results provide valuable insights into how alterations in sarcomere protein function modify postnatal heart development and highlight the potential for targeting cell cycle regulatory pathways to counteract cardiomyopathic stimuli.