Sports and Exercise in Athletes with Hypertrophic Cardiomyopathy

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Key points

  • Hypertrophic cardiomyopathy (HCM), characterized by ventricular hypertrophy and relaxation abnormalities, is the most common genetic cardiovascular disease and among the leading causes of sudden cardiac death in young athletes.

  • Current guidelines of both American and European cardiology societies recommend that patients with HCM refrain from all but low-intensity sports independent of implantable cardioverter-defibrillator (ICD) use.

  • Despite theoretic concerns that exercise can increase the risk

Hypertrophic cardiomyopathy: epidemiology, pathophysiology, diagnosis, clinical course, and treatment

HCM is the most common genetic cardiovascular disease, affecting 1 in 500 people and characterized by ventricular hypertrophy and relaxation abnormalities (Fig. 1).3 The disease is not only common but also nondiscriminating; it afflicts patients around the world irrespective of geography, sex, ethnicity, and race.4, 5, 6, 7 It is also a leading cause of sudden cardiac death (SCD) in young athletes younger than 40 years.8 Although shrouded in mystery for decades after its initial description

The birth of guidelines: Bethesda and beyond

In 1985, the American College of Cardiology (ACC) sponsored the 16th Bethesda Conference, which outlined for the first time consensus recommendations to govern the participation of patients with HCM in competitive sports.13 Underlying its mission was the assumption that intensive physical activity could provoke SCD and, conversely, that limiting such activity could mitigate that risk. Although the committee made use of published data and clinical experience, it also freely acknowledged its

Comparisons to European guidelines

Although the initial recommendations were made in the United States, the European Society of Cardiology (ESC) followed soon thereafter with similar documents guiding participation of patients with various types of heart disease in both competitive and recreational sports.17, 18 The guidelines were nearly identical, save for recommendations for genotype positive–phenotype negative individuals. The ESC opted to include these individuals among the at-risk population and recommended activity

The evidence behind the guidelines

Estimates of the proportion of SCD in athletes attributable to HCM vary widely. The US National Registry of Sudden Death in Athletes, which builds its database from review of public records, reports that HCM underlies 36% of SCD.7, 8, 23 Another study using a similar approach to analyze deaths of high school and college athletes identified half of SCDs as being due to HCM.24 In stark contrast, a mandatory reporting system implemented in Northern Italy studying competitive athletes noted only 2%

The cause of sudden cardiac death in hypertrophic cardiomyopathy is rooted in an electrically unstable substrate

The precise mechanism of SCD in patients with HCM is presumed to be ventricular tachyarrhythmias, which develop as a direct result of structural abnormalities.32 At the cellular level, hypertrophied myocytes are associated with prolonged repolarization of transmembrane action potentials.33 In addition, both the composition and distribution of ion channels seen in typical myocytes are deranged in hypertrophied cells.34 When such hypertrophy occurs with regional variation, it conceivably

Does exercise increase the risk of sudden cardiac death in hypertrophic cardiomyopathy?

Given the underlying structural predisposition to rogue electrical currents in these patients, any external stress to such a system could understandably have catastrophic outcomes. Physical activity can alter blood volume, electrolytes, metabolism, catecholamine levels, and autonomic tone, any of which may contribute to a heightened risk of ventricular arrhythmias.37 Nevertheless, in a study of patients with HCM undergoing treadmill or bicycle ergometer exercise testing, only 3 of 1380

The exercise paradox in hypertrophic cardiomyopathy

Many have written of the so-called exercise paradox among adults, struggling to reconcile the many known cardioprotective benefits of physical activity with the attributed increase in risk for SCD.45 Exercise has long been embraced by the scientific community as a means of decreasing cardiovascular morbidity and mortality and has been championed by countless organizations as a public health initiative.46, 47, 48, 49 Furthermore, exercise capacity is strongly correlated with longevity.50

Challenging the guidelines

A substantial proportion of patients with HCM continue to compete at a high-intensity level, often perhaps against medical advice. Of 897 patients with HCM surveyed in one particular study, 63% reported having participated in competitive athletics, often in multiple sports.60 Case reports and case series abound that identify upper echelon athletes competing at extreme levels only to later be diagnosed with HCM.66, 67 It therefore stands to reason that unilateral restriction of all patients with

Stratification by Genetics

There has been considerable interest to risk stratify patients with HCM based on their particular genetic mutation. Lending further hope was the fact that such strategies had been successfully implemented in other inherited diseases that similarly predispose to SCD, such as long-QT syndrome.68 Several studies successfully identified a limited number of genetic defects of a particularly malignant variety.69, 70, 71 However, this once promising approach has ultimately been thwarted by an

Other avenues of prevention

Although risk stratification, be it by genetic mutation, patient demographic, or clinical presentation, allows a clinician to identify many patients at increased risk of SCD and respond by restricting activities and/or implanting an ICD, such a strategy will inevitably fail to prevent SCD entirely. A substantial proportion of patients with SCD due to HCM are actually asymptomatic until an episode of SCD, posing a major challenge for prevention efforts.8, 39, 99 In some cases, these patients

Medical-legal implications

SCD is invariably devastating to a treating physician, yet it often carries legal implications. Athletes and their families have brought litigation against physicians for what was perceived to be inappropriate clearance.105 On the other hand, athletes have also sued physicians for inappropriately restricting them from competition.106 Unfortunately, limited by the lack of established legal precedent, most cases has been settled over the years.

Guidelines certainly provide a helpful framework to

Should he be allowed to play? The case of Nicholas Knapp

Nick Knapp dreamed of playing college basketball. When team physicians at Northwestern University declared him ineligible because of a history of HCM and recent aborted SCD for which an ICD was placed, he took them to court. Although the initial ruling was in favor of Knapp, Northwestern University subsequently won the appeal.106 Knapp then enrolled at another Division I university that allowed him to compete despite his medical history. After a successful career spanning more than 3 years, his

Future directions

The current understanding of HCM and its associated risk of SCD has evolved tremendously since the disease was first characterized more than 60 years ago. Furthermore, with the advent of the ICD and AED, SCD in an athlete can now often be aborted successfully. Yet the goal of eliminating SCD entirely remains, and the significant gaps in knowledge provide ample opportunities for continued exploration. Clinical trials in the HCM population are underway, including some that hope to establish the

Summary

Contemporary guidelines freely admit to taking a necessarily conservative stance because high-quality evidence on which to base its recommendations is lacking. Yet many patients with HCM choose to continue to compete and enjoy all of the physical and mental benefits of athletics.66, 67 Ongoing research will further refine the guidelines so that the benefits to be enjoyed by many are no longer forfeited to avoid the potential harm of a select few.

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      This finding stems from early observations that many SCD victims succumbed during physical exertion16 and that HCM was the leading cause of SCD in young athletes in the United States.17 However, subsequent studies have challenged these findings and suggested that the estimated risk of SCD in athletes with HCM who compete in sports is in the range of 0.03% to 0.10% per year.18 We now know that the majority of people with HCM who suffer an SCD event do so either at a time remote from exercise or while completely at rest.19–21

    • Sudden Cardiac Death in Athletes

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      A prospective study of SCD among children and young adults conducted in Australia and New Zealand from 2010 through 2012 attributed only 6 of 54 cases (11%) of HCM during or post-exercise, whereas 20 were unexplained (37%) (37). Alpert et al. (50) condensed several published studies to generate an estimated risk of SCD for athletes due to HCM at 0.03% to 0.1%, which is comparable to contemporary published mortality rates in the overall HCM population (51). Arrhythmogenic right ventricular cardiomyopathy (ARVC) is characterized by fibrofatty replacement of the RV myocardium with variable disease expression that can increase risk of SCD, notably during exertion (52).

    • Sudden Cardiac Death in Genetic Cardiomyopathies

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      It is a global disease, with epidemiologic studies from several parts of the world reporting a similar prevalence of about 0.2% (ie, 1 in 500) in the general population, which is equivalent to at least 600,000 people affected in the United States.34 HCM can be complicated by SCD, HF, or cardioembolic stroke resulting from atrial fibrillation (AF), which affects up to 28% of patients with HCM.35 Suspicion of HCM usually follows the onset of symptoms or a cardiac event but can also arise from recognition of a heart murmur or abnormal 12-lead ECG during routine or preparticipation sports examinations, or in family cascade screening.

    • Exercise Training In Athletes With Heart Disease

      2017, Progress in Cardiovascular Diseases
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      These consensus recommendations, however, do not necessarily apply to noncompetitive, recreational activities. Mild to moderate recreational PA, tailored to individual abilities, is permissible in order to help maintain overall CV health.68,69 We prefer aerobic activities as opposed to isometric exercise in these situations.65

    • Exercise in patients with hypertrophic cardiomyopathy: A review of current evidence, national guideline recommendations and a proposal for a new direction to fitness

      2017, Journal of Science and Medicine in Sport
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      Notably, HCM was only present in 2% of cases, a significantly lower prevalence compared to reports from prior US studies, perhaps reduced by routine pre-participation screening and rigorous case ascertainment.3 Overall, the risk of SCD for actively competing athletes with HCM is likely less than 0.1% per year, considering the incidence of SCD amongst athletes and prevalence of HCM in the general population.29 The exact mechanism underlying the association between exercise and SCD remains unclear.

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      This recommendation is not dependent on the severity of LVOTO, symptoms, or previously performed septal reduction treatments.94 However, recreational physical activities are advisable and should be tailored to each patient according to their own risk profile.1,145 Most patients with hypertrophic obstructive cardiomyopathy tolerate pregnancy well, but severe LVOTO, heart failure, arrhythmias, and medication taken in the pre-pregnancy period have been identified as risk factors of adverse cardiovascular events during pregnancy.1,2,146

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    Funding sources: Dr C. Alpert, nil; Dr S.M. Day, NIH R01 GRANT11572784; Dr S. Saberi, AHA Award 11CRP7510001, MICHR UL1TR000433.

    Conflict of interest: Nil.

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