Scope of the problem

Almost without exception, sudden cardiac arrest (SCA) in athletes under 35 years of age results from the presence of structural or functional heart disease. The most common causes of SCA in the young in the United States are hypertrophic cardiomyopathy (HCM), other cardiomyopathies, coronary artery anomalies, electrical abnormalities including long QT syndrome and catecholaminergic polymorphic ventricular tachycardia, myocarditis, aortic rupture and others.1 2 3 The precise occurrence of SCA associated with these conditions in athletes is unknown but has been estimated to be around 1 in 100 000 in the US, with other estimates of 1 in 50 000 to 1 in 200 000.4 5 6 SCA is reported to occur nine times more frequently in men and boys than in women and girls.6 7 In addition, in the United States, the incidence of SCA is five times greater in African–Americans than in Caucasians.8

While congenital heart defects are the most common of the birth defects (8 per 1000 live births), not all are easily identified, and those most commonly associated with SCA are often subtle and difficult to recognise in young individuals. Identification may occur because of physical signs such as a heart murmur, or because of symptoms such as exertional syncope, chest pain, palpitations, or exercise intolerance. Others may be identified because of family history or after a family member is found to have an inherited cardiovascular condition or has experienced SCA.

Prevention of sudden cardiac arrest

To prevent SCA, a predisposing disease condition must be identified, and early intervention provided, such as medication, lifestyle alterations, and defibrillation devices, in order to decrease the risk of sudden cardiac death. At the present time, the best method to identify children at risk for SCA is still controversial.9 10 11 12 13 14 15 Recent articles have suggested that it is time to readdress these issues.16 17 18 Data from countries with electrocardiographic (ECG) screening have demonstrated that ECG screening can identify children and adolescents with undiagnosed conditions that predispose to SCA and is more sensitive in identifying those at risk for SCA than history or physical exam alone.15 19 20 In Italy, national preparticipation ECG screening for those aged over 25 years has resulted in competitive sports restrictions in individuals found to be at risk for SCA and a decrease in SCA of 89%.14 This led to a Consensus Statement from the European Society of Cardiology that recommended the addition of an ECG to the preparticipation history and physical examination.21 The primary screening tool currently employed in the United States for those involved in athletics, recommended by a panel of experts, includes only the preparticipation history and physical exam, with little data available to indicate its efficacy or effectiveness in the population to identify those at risk or to prevent SCA.13

Exercise and the heart

The problem with exercise is that it is known to trigger ventricular arrhythmias that lead to SCA in susceptible individuals with underlying heart conditions, both diagnosed and undiagnosed. Up to 90% of SCA in athletes occurs while the individual is engaged in vigorous activity or sports.3 While the degree to which abstention from some or all sports might change the risk of death is unclear, recent reports from the Italian screening programme suggest that preparticipation screening that includes an ECG has the potential to significantly decrease the occurrence of sudden cardiac death.14 21

Activity guidelines

If a cardiac condition is identified, the athlete’s physician should provide a recommendation for sports participation and for physical activity in general. With the myriad of congenital heart defects and cardiac conditions known to predispose to SCA, this can be a daunting task. Fortunately, there are guidelines drafted by panels of experts that have been published in the United States, the 36th Bethesda Conference (BC#36), and European Society of Cardiology (ESC), as well as a joint report contrasting these two guidelines that provide assistance to those making recommendations on activity levels and sports participation.16 22 23

We present a summary of the recommendations from these reports and a discussion of the potential difficulties associated with following these guidelines when advising individuals. All recommendations from these reports focus on young “competitive athletes”, defined as “individuals who are aged 35 years or less and are engaged in a regular fashion in exercise training as well as participating in official athletic competitions…placing high premium on athletic excellence and achievement… [exhibiting] a strong inclination to extend themselves physically to their limits and to improve performance”.22 Additionally, there is an American Heart Association Scientific Statement guideline for recreational activity for individuals with genetic cardiovascular diseases (AHA).24

These recommendations are suggested as broad guidelines to be applied to individuals after a thorough evaluation by a practitioner who is familiar with the individual. It is not uncommon for these recommendations to meet resistance from those who have been participating in sports and who value that participation. The physician must weigh the theoretical increase in the risk of sudden death associated with activity or exercise against the social, psychological, and health benefits of sports participation.25 26 27 28

General principles

There are a number of general principles to keep in mind before applying specific activity recommendations. These are well outlined in the 2005 AHA recommendations.24 The following are particularly important for children with high risk conditions for SCA. Burst exertion is best avoided, leading to the recommendation to avoid activities which require sudden sprinting efforts. Instead, a stable consistent form of exercise, such as recreational jogging or biking, is better tolerated. Extremes of environment such as excessive heat or cold should be avoided. Moderation is best in all activities, but adolescents respond to peer pressure and will often “compete” even in recreational activities. Extreme sports such as hang gliding, sky diving, and bungee jumping should be avoided. The use of substances to enhance performance or the combination of physical activity with stimulant drugs, high levels of caffeine, alcohol, or illicit drugs can be a fatal mistake in susceptible individuals with high-risk cardiac conditions. Acceptable less risky alternatives should be suggested. Additionally, one should have a familiarity with the classification of sports that is generally used in these documents, which includes dynamic and static components and the level of intensity from low to medium to high, as shown in fig 2 of the BC#36.29

Hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most common cause of sudden cardiac death in children and young adults in the United States.30 31 32 33 34 The frequency of death associated with HCM has been estimated to be between 1% to 6% per person per year, with the highest incidence between the ages of 12 and 35.30 It is estimated that only 10 to 20% of patients with HCM are susceptible to SCA.35 While our ability to risk stratify these individuals is limited, it has been suggested that the following place the athlete with HCM at higher risk: aborted SCA, unexplained syncope, extreme left ventricular hypertrophy with septal thickness >30 mm, decrease in blood pressure with exercise, family history of SCA, and non-sustained ventricular tachycardia.36

Sudden death in HCM is thought to be associated with myocardial cellular disarray in the left ventricular myocardium, resulting in increased frequency of re-entrant ventricular tachyarrhythmias. In addition, the presence of small vessel disease in abnormal intramural coronary arteries can result in ischaemia, myocardial death, and intramural scarring, ultimately contributing to the electrical instability of the ventricle.30 Exercise has been hypothesised to result in greater hypertrophy of the already disordered myocardium and increase the metabolic demand on the myocardium, increasing the likelihood of a life-threatening arrhythmia. The general consensus has been that patients with HCM should refrain from participation in all competitive sports, with the possible exception of low-intensity, low-static sports, such as golf. It is agreed that isometric exercises such as weight lifting, football and wrestling should be avoided. The European document is more restrictive than the Bethesda Conference #36, which allows gene-positive but phenotype and symptom-negative individuals to participate in low-level physical activity.16 23 37 Given the emotional and psychological difficulties in restricting activity after an individual has already established a strong interest in the sport, we would suggest that some type of sport that is low-intensity, such as golf or bowling, be introduced at a young age to direct the person’s interests in another direction rather than having to switch recommendations in later adolescence. Additional research is needed to resolve the differences in these recommendations in the preclinical gene-positive group.

Arrhythmogenic right ventricular cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a primary myocardial disease, associated with the replacement of normal myocardial cells with fibrous and fibrofatty tissue.38 Similarly to HCM, these changes result in an increased frequency of ventricular tachyarrhythmias and sudden death. While HCM is the most common cause of SCA in the United States, ARVC is the most common cause of SCA in Italy, where it has been reported that exercise in children with ARVC is associated with a fivefold increase in the relative risk of death compared with no exercise.13 The general consensus is that patients with ARVC, like those with HCM, should refrain from participation in all competitive sports, with the possible exception of low-intensity, non-contact sports.16 23 37

Dilated cardiomyopathy

Dilated cardiomyopathy (DCM), while less frequent than either HCM or ARVC, represents a significant cause of sudden cardiac death in the young. This condition is characterised by LV dilation, impaired systolic function, and segmental wall motion abnormalities.39 The increase in metabolic demand associated with competitive exercise can result in cardiac ischaemia, leading to arrhythmias. While there is limited data on the relative risks associated with exercise in children with DCM, consensus recommendations in the United States suggest that these patients should be excluded from all competitive sports.37 The ESC suggests that patients with no symptoms, no family history of sudden death, ejection fraction ⩾40%, normal blood pressure response to exercise, and no ventricular arrhythmias might be allowed to participate in low-moderate dynamic and low-static sports, such as golf, volleyball, and baseball.23

Long-QT syndrome (LQTS)

LQTS is a disorder of delayed ventricular repolarisation characterised by prolongation of the QT interval on the ECG. The aetiology is known to be primarily related to abnormalities in ion channels or the macromolecular complex associated with the ion channel.40 SCA can result from superimposed adrenergic stimulation during exercise, leading to triggering of ventricular arrhythmias, including the characteristic torsades de pointes, a form of ventricular tachycardia.3 7 41 The prevalence of LQTS is estimated to be 1:2500,42 and associated mortality ranges from 0.3% to 2% per year, dependent on age, QTc, and genetic locus.43 Patients with LQT1 appear to be at a particularly increased risk of sudden death with exercise, especially when swimming and diving. Patients with LQT2 appear to be at increased risk in the presence of loud noises such as a starter’s buzzer or pistol as well as from emotional stimuli.44 The BC#36 defined LQTS as a QTc >470 ms in boys and >480 ms in girls.45 It concluded that even asymptomatic patients who meet the criteria should be restricted to low-intensity activities. They further stated that genotype-positive, phenotype-negative patients should be given no restrictions, except for those with LQT1, who should be advised against swimming and diving.46 The ESC used less strict criteria to define LQTS (>440 ms in boys and >460 ms in girls) and recommended the exclusion of children with genotype-positive LQTS from all sports, “even without documented major arrhythmic events”.16 23 For children with borderline QTc, they recommended close periodic surveillance. The AHA recreational guidelines did not provide QTc criteria, but commented on the importance of restricting “extreme activities”, such as amusement park rides and bungee jumping, swimming and diving in patients with LQT1, and activities that involve loud, sudden noises, such as races whose starts are signalled by pistol shots, in patients with LQT2.27

Brugada syndrome

The Brugada syndrome is characterised by findings of right bundle branch block and ST segment elevation in the precordial leads on ECG, and is known to be associated with an abnormality in the sodium channel in 15 to 30% of cases.47 48 In patients with Brugada syndrome and prior syncope or aborted SCA, the risk of ventricular fibrillation or SCA over a 3 year follow-up period was shown to be 40%.49 It is believed that patients with Brugada syndrome are at increased risk of sudden death in the setting of elevated body temperature, such as that experienced during exercise. For these reasons, all consensus panels recommended that patients with Brugada syndrome avoid most physical activity. While the BC#36, unlike the ESC, allows for low-intensity sports, it does restrict patients to this category of participation even after implantable cardioverter defibrillator placement.16 23 45

Catecholaminergic polymorphic ventricular tachycardia

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is associated with exercise-induced polymorphic ventricular tachycardia and a high risk of sudden death, in the setting of a normal resting ECG. All three consensus panels recommended that patients with CPVT avoid virtually all forms of physical activity, as well as extreme activities.16 23 45

Wolff–Parkinson–White syndrome

Wolff–Parkinson–White syndrome (WPW) is characterised by ventricular pre-excitation. It is estimated to occur in 0.1% to 0.3% of the population.50 While sudden death is rare, some patients are at risk, especially those with atrial fibrillation with rapid conduction to the ventricle that could lead to ventricular fibrillation.51 For this reason, ablation is recommended for patients with syncope, presyncope, multiple accessory pathways, or ventricular rates >240 beats/min. The ESC recommends that an electrophysiological study be used to risk stratify these individuals.23 There is no consensus on how to guide asymptomatic patients, or how to guide young patients.

Abnormal origin of the coronary arteries

Personal medical cardiac history may be more helpful than the ECG in identifying some of the other causes of SCA in children, particularly congenital anomalies of the coronary arteries, which occur with a prevalence of 0.2% in children and adolescents.52 In patients with coronary abnormalities, the physical exam is usually normal. Up to 40% of these patients have symptoms prior to SCA, and up to 20 to 30% may have ischaemic changes on ECG.4 52 The Italian data indicate a strong correlation between athletics and death from abnormal origin of the coronary arteries.14 We agree that patients with this condition should be restricted from all competitive sports prior to surgical intervention. The risks postoperatively are not clearly defined at this time and should be made on an individual basis after appropriate testing, including evaluation during exercise.

Structural or congenital heart disease

Congenital heart disease is a broad category encompassing hundreds of anomalies. Specific recommendations for each of these conditions go beyond the scope of this paper, but there are general principles discussed in the various guidelines that can help guide the physician.53 Areas of particular risk and concern are patients with increased pulmonary vascular resistance and heart failure. Consideration should be given to prevent collision and bodily contact in patients with conduits, mechanical valves and postoperative status, particularly for individuals on anticoagulation. Postoperative subjects are advised to wait 3–6 months prior to athletic participation, depending on the specific condition and result.

Connective tissue disorders

Marfan syndrome and Ehlers–Danlos are connective tissue disorders associated with substantial risk of aortic dissection or rupture. Recommendations uniformly state that children with Ehlers–Danlos should not participate in any kind of competitive sports.37 Recommendations for Marfan syndrome are more flexible in the Bethesda Conference #36, due to the wide range of phenotypic expression. If the aortic root is <40 mm (Z-score <2), with no mitral regurgitation, and no family history of sudden death or aortic dissection, then low-intensity sports such as distance running or swimming are allowed. The ESC guidelines only allow recreational sports.16 23

Implantable cardiac devices and pacemakers

It is recommended that patients with implantable cardiac devices and pacemakers be restricted from participation in contact sports, due to the possibility of physical damage to these devices.16 54 Other restrictions are based on the underlying condition that precipitated the placement of these devices.

Alternatives

While it may be more straightforward to have a strict list of guidelines to follow, adolescents will often challenge or disregard recommendations. Even if not allowed to participate on scholastic teams, they often will maintain a high level of activity and compete in other venues. Thus, it is more practical to engage the individual adolescent or younger child and to find a compromise, when possible in select circumstances, to afford as much protection as possible while gaining understanding and cooperation in following medical advice. These alternative recommendations need to be carefully and thoughtfully individualised based on the underlying cardiac pathology. For example, with soccer or another similar sport that requires a goalie, such a position may become a means by which an otherwise restricted child or adolescent may participate. One must enlist the coach to agree only to play the child in that position and not to make them practise the team drills, weight lifting or running exercises. The child must also be of such a temperament that the goalie position is not stressful. Similarly, place kicking in football is another potential alternative for selected individuals if participation is limited to that one activity and training is modified. Many baseball or softball coaches will be willing to play a child in an infield position and agree not to make them do running drills or lift weights. Other athletes may be willing to be the team manager, but the psychological effect of this type of position must be carefully considered. All of these alternatives require a good deal of time, conversation, and cooperation between the athlete, family, school, coach, and physician.

Physical education classes

A child or adolescent with a cardiac condition often has difficulty regarding the school’s physical activity curriculum. At times, these children are asked to participate in more strenuous activities than appropriate, while at other times they are prohibited from even the most unthreatening of play activities. The concept for these children is to find a balance that will not put them at risk but will allow as much participation in healthy activities with their friends as possible. The psychological and physiological implications of restriction from activity must be weighed against the risks of physical activity. This means that the practitioner must often provide the school with an individualised plan with specific restrictions when indicated. Certainly, the consensus guidelines can be followed and extrapolated to physical education classes, but schools often want very specific recommendations. It is helpful to ask for a copy of the school Physical Education curriculum that can serve as a check list for acceptable activities. Communication with the school nurse and physical education teacher to clarify recommendations may be necessary. In the US, these types of children may be advised not to participate in the activities associated with the “President’s Physical Fitness Test” or “Mile Run”; they may be allowed to select less competitive activities that consist of low-intensity participation during regular physical education classes and at the end of year “Field Days”. For those who have conditions that predispose to dizziness or syncope, activities such as rope climbing should be avoided. Weight lifting may need to be completely prohibited or instructions provided for moderation specifying the number of repetitions and sets.

Automated external defibrillators (AED)

While an AED should not be considered a reason to allow physical activity that would not otherwise be recommended, every school should have the resources to resuscitate and defibrillate any individual on their premises who experiences an unexpected SCA. Particularly, schools with individuals with high-risk conditions should be prepared by having an AED and trained personnel who can perform cardiopulmonary resuscitation and use the AED for secondary prevention of SCA, if needed.

Discussion

These recommendations represent a composite of expert opinions.16 22 23 27 They are intended to guide the practitioner as he or she advises a child or young adult who has been diagnosed with one of these conditions. As the guidelines state, an organisation might be legally supported in refusing to allow a child or young adult to participate in competitive sports based on these criteria, but a practitioner, considering patient-specific characteristics, would not commit malpractice in deviating from these guidelines.55 Indeed, these recommendations do not address the more subtle, individual factors that must be evaluated, such as the patient’s age and developmental stage at diagnosis and current level of activity. It is very different to tell the parents of a 2-year-old that they should encourage their child to pursue interests other than sports than it is to tell the 17-year-old captain of the football team, who has a college athletic scholarship, that he ought to stop playing to prevent a potential incalculable risk of dying. All adolescents feel invincible, and, although it is very difficult for everyone at this stage to make lifestyle changes, activity restrictions are sometimes necessary to reduce the risk of a catastrophic event.

For a very young child, the feelings of loss and isolation associated with a diagnosis that is not understood can often be mitigated by suggesting selection of different activities and participation in non-competitive groups that confer similar social and psychological benefits as sports, but without the risk of SCA.3 56 The particular difficulty that arises in treating this age group is the fact that children may not think abstractly and understand the purpose of the restrictions. This can lead to significant distortions in understanding of the disease. Thus, the practitioner will need to continue periodic discussion regarding the condition and clarify issues as the child ages and is better able to understand. This emphasises the importance of continuity and long-term follow-up in managing children with identified cardiac disorders.57 The psychological impact on teenagers and preteens, and even elementary school children, in families in which success through athletic achievement has been emphasised heavily, is more immediate, and, perhaps, more profound. It is important for practitioners to be cognisant of the fact that, during this stage of development, a child’s sense of identity is often intrinsically linked to a select few areas in which he or she has received overt praise, such as athletic or academic achievement. The sudden loss of one of these areas can produce a tremendous sense of despair as children are forced abruptly to question and redefine their identities.58

For adolescents and young adults, the psychological implications are more complicated. For a select few there might be economic considerations associated with stopping athletic competition for those who were hoping to obtain scholarships for higher education or to play professionally. Fortunately, for the majority of individuals, the importance of sports participation declines significantly with age, as the constraints associated with work and family take priority. In young adults, the diagnosis often raises questions about mortality, in the context of greater social and personal responsibilities.59 In counselling such patients, it can be helpful for a practitioner to spend time describing the information that is known and answering questions, in order to give patients a greater sense of control.60

Another limitation of these guidelines is that they distinguish between organised and non-organised sports, calling only the former “competitive”. In practical application, this is a false dichotomy; many children are as competitive, and as demanding of their heart on the playground as they are in organised sports. A physician should keep this in mind when advising children and their families.

Conclusions

Sudden cardiac death in the young is a rare but devastating occurrence, largely associated with cardiac conditions with poorly defined risk profiles. It is challenging for practitioners to advise such patients and their families, but some data do exist, and different groups of experts have developed consensus statements that can be used to guide physicians through this process. More research is needed to further delineate the relative risks associated with these conditions and sports participation, so that the physician can better advise affected individuals. It is important to realise and to impart to children, adolescents, and their families that an active life is possible with careful planning and moderation.