Exercise in Hypertrophic Cardiomyopathy

The Role of Genetics in the Management of Heart Failure Patients

Over the last decades, the relevance of genetics in cardiovascular diseases has expanded, especially in the context of cardiomyopathies. Its relevance extends to the management of patients diagnosed with heart failure (HF), given its capacity to provide invaluable insights into the etiology of cardiomyopathies and identify individuals at a heightened risk of poor outcomes. Notably, the identification of an etiological genetic variant necessitates a comprehensive evaluation of the family lineage of the affected patients. In the future, these genetic variants hold potential as therapeutic targets with the capability to modify gene expression. In this complex setting, collaboration among cardiologists, specifically those specializing in cardiomyopathies and HF, and geneticists becomes paramount to improving individual and family health outcomes, as well as therapeutic clinical results. This review is intended to offer geneticists and cardiologists an updated perspective on the value of genetic research in HF and its implications in clinical practice.

Clinical scenarios of hypertrophic cardiomyopathy-related mortality: Relevance of age and stage of disease at presentation

The evolving epidemiology of hypertrophic cardiomyopathy (HCM) has progressively changed our perception of HCM-related mortality. However, recent studies detailing individual causes of death based on age and clinical setting are lacking. Thus, the present study aimed to describe the modes of death in a consecutive cohort of HCM patients based on presenting clinical features and stage of disease.

METHODS

By retrospective analysis of a large HCM cohort, we identified 161 patients with >1 year follow-up who died between 2000 and 2020 and thoroughly investigated their modes of death. HCM stage at presentation was defined as "classic", "adverse remodeling" or "overt dysfunction".

RESULTS

Of the 161 patients, 103 (64%) died of HCM-related causes, whereas 58 (36%) died of non-HCM-related causes. Patients who died of HCM-related causes were younger than those who died of non-HCM related causes. The most common cause of death was heart failure (HF). Sudden cardiac death (SCD) ranked third, after non cardiovascular death, and mostly occurred in young individuals. The proportion of HF related death and SCD per stage of disease was 14% and 27% in "classic", 38% and 21% in "adverse remodeling" and 74% and 10% in "overt dysfunction".

CONCLUSIONS

Most HCM patients die due to complications of their own disease, mainly in the context of HF. While SCD tends to be juvenile, HF related deaths often occur in age groups no longer amenable to cardiac transplant. Modes of death vary with the stage of disease, with SCD becoming less prevalent in more advanced phases, when competitive risk of HF becomes overwhelming.

Hypertrophic Cardiomyopathy: Updates Through the Lens of Sports Cardiology

Purpose of review

This review will summarize the distinction between hypertrophic cardiomyopathy (HCM) and exercise-induced cardiac remodeling (EICR), describe treatments of particular relevance to athletes with HCM, and highlight the evolution of recommendations for exercise and competitive sport participation relevant to individuals with HCM.

Recent findings

Whereas prior guidelines have excluded individuals with HCM from more than mild-intensity exercise, recent data show that moderate-intensity exercise improves functional capacity and indices of cardiac function and continuation of competitive sports may not be associated with worse outcomes. Moreover, recent studies of athletes with implantable cardioverter defibrillators (ICDs) demonstrated a safer profile than previously understood. In this context, the updated American Heart Association/American College of Cardiology (AHA/ACC) and European Society of Cardiology (ESC) HCM guidelines have increased focus on shared decision-making and liberalized restrictions on exercise and sport participation among individuals with HCM.

Summary

New data demonstrating the safety of exercise in individuals with HCM and in athletes with ICDs, in addition to a focus on shared decision-making, have led to the most updated guidelines easing restrictions on exercise and competitive athletics in this population. Further athlete-specific studies of HCM, especially in the context of emerging therapies such as mavacamten, are important to inform accurate risk stratification and eligibility recommendations.

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.

Biomarkers of cardiovascular stress and fibrosis in preclinical hypertrophic cardiomyopathy

Objective

Sarcomeric gene mutation carriers without overt left ventricular hypertrophy (G+/LVH-) can harbour subclinical changes in cardiovascular structure and function that precede the development of hypertrophic cardiomyopathy (HCM). We sought to investigate if circulating biomarkers of cardiovascular stress and collagen metabolism among G+/LVH- individuals, measured at rest and following exercise provocation, yield further insights into the underlying biology of HCM.

Methods

We studied 76 individuals with overt HCM, 50 G+/LVH- individuals and 41 genotype-negative related controls enrolled in a cross-sectional, multicentre observational study (HCMNet). Biomarkers of cardiac stress (N-terminal pro-B-type natriuretic peptide, NT-proBNP; high-sensitivity troponin I, hsTnI; soluble ST2) and fibrosis (carboxy-terminal propeptide of procollagen type I; C-terminal telopeptide of type I collagen; galectin-3; periostin) were measured.

Results

Individuals with overt HCM had elevated NT-proBNP and hsTnI compared with G+/LVH- subjects and controls at rest, along with an exaggerated increase in NT-proBNP and hsTnI in response to exercise. We found no detectable differences in resting or exercise-provoked biomarker profiles of cardiovascular stress and fibrosis among G+/LVH- individuals compared with healthy controls despite subtle echocardiographic differences in cardiac structure and function.

Conclusion

Dynamic exercise testing exaggerated resting differences in natriuretic peptides and troponin elevations among individuals with overt HCM. In contrast, we found no differences in biomarker profiles of cardiovascular stress and fibrosis among G+/LVH- individuals compared with controls even after maximal exercise provocation. Our findings highlight the need for continued investigation into early phenotypes of sarcomeric gene mutations and the evolution of HCM.

Physical activity and other health behaviors in adults with hypertrophic cardiomyopathy

The clinical expression of hypertrophic cardiomyopathy (HC) is undoubtedly influenced by modifying genetic and environmental factors. Lifestyle practices such as tobacco and alcohol use, poor nutritional intake, and physical inactivity are strongly associated with adverse cardiovascular outcomes and increased mortality in the general population. Before addressing the direct effect of such modifiable factors on the natural history of HC, it is critical to define their prevalence in this population. A voluntary survey, drawing questions in part from the 2007 to 2008 National Health and Nutrition Examination Survey (NHANES), was posted on the HC Association website and administered to patients with HC at the University of Michigan. Propensity score matching to NHANES participants was used. Dichotomous and continuous health behaviors were analyzed using logistic and linear regression, respectively, and adjusted for body mass index and propensity score quintile. Compared to the matched NHANES participants, the patients with HC reported significantly less alcohol and tobacco use but also less time engaged in physical activity at work and for leisure. Time spent participating in vigorous or moderate activity was a strong predictor of self-reported exercise capacity. The body mass index was greater in the HC cohort than in the NHANES cohort. Exercise restrictions negatively affected emotional well-being in most surveyed subjects. In conclusion, patients with HC are less active than the general United States population. The well-established relation of inactivity, obesity, and cardiovascular mortality might be exaggerated in patients with HC. More data are needed on exercise in those with HC to strike a balance between acute risks and the long-term health benefits of exercise.

Prevalence and spectrum diseases predisposing to sudden cardiac death: are they the same for both the athlete and the nonathlete?

Sudden cardiac death (SCD) is a rare but devastating event among young people. The precise scale of the event remains undefined. This uncommon but catastrophic event usually is proved to be the consequence of varied unsuspected congenital or acquired cardiovascular diseases. Hypertrophic cardiomyopathy and coronary artery anomalies are the two most frequent causes of SCD. Most commonly, SCD resulting from these diseases occurs during or immediately after exercise. This report highlights the prevalence and spectrum of SCD-predisposing diseases and how they are affected by athletic participation. In addition, disease-specific guidelines for sports participation are addressed.

Disease pathways and novel therapeutic targets in hypertrophic cardiomyopathy

As described in earlier reviews in this series on the molecular basis of hypertrophic cardiomyopathy (HCM), HCM is one of the archetypal monogenic cardiovascular disorders to be understood at the molecular level. Twenty years after the discovery of the first HCM disease gene, genetic studies still confirm that HCM is principally a disease of the sarcomere. At the biophysical level, myofilament mutations generally enhance Ca(2+) sensitivity, maximal force production, and ATPase activity. These defects ultimately appear to converge on energy deficiency and altered Ca(2+) handling as major common paths leading to the anatomic (hypertrophy, myofiber disarray, and fibrosis) and functional features (pathological signaling and diastolic dysfunction) characteristic of HCM. In this review, we provide an account of the consequences of HCM mutations and describe how specifically targeting these molecular features has already yielded early promise for novel therapies for HCM. Although substantial efforts are still required to understand the molecular link between HCM mutations and their clinical consequences, HCM endures as an exemplar of how novel insights derived from molecular characterization of Mendelian disorders can inform the understanding of biological processes and translate into rational therapies.

Impact of polymorphisms in the renin–angiotensin–aldosterone system on hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a clinically heterogeneous autosomal dominant heart disease characterised by left ventricular hypertrophy in the absence of another cardiac or systemic disease that is capable of producing significant wall thickening. Microscopically it is characterised by cardiomyocyte hypertrophy, myofibrillar disarray and fibrosis. The phenotypic expression of HCM is multifactorial, with the majority of cases occurring secondary to mutations in genes encoding the sarcomere proteins. In conjunction with the genetic heterogeneity of HCM, phenotypic expression also exhibits a high level of variability even within families with the same aetiological mutation, and may be influenced by additional genetic factors. Polymorphisms of the renin–angiotensin–aldosterone system (RAAS) represent an attractive hypothesis as potential disease modifiers, as these genetic variants alter the ‘activation status’ of the RAAS, which leads to more left ventricular hypertrophy through different pathways. The main objective of this review is to provide an overview of the role of different polymorphisms identified in the RAAS, in patients with HCM.