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Release Date: August 30, 2006
Athletes are generally thought to be very healthy, so when sudden cardiac death (SCD) occurs in this population, it is a particularly unexpected and high-profile event. But just as in the general population, athletes can harbor undiagnosed cardiac disease and congenital abnormalities that unknowingly put them at high risk for SCD. Moreover, intensive athletic activities may trigger life-threatening arrhythmias in susceptible subjects. It is noteworthy that athletic training can result in physiologic adaptations in the heart (including atrial dilatation and hypertrophy) and autonomic changes in heart rate control (such as sinus bradycardia, atrioventricular [AV] nodal conduction disturbances, and atrial fibrillation [AF]) that can be difficult at times to distinguish from more serious structural or arrhythmia problems.
Although the word "athlete" can be defined in various ways, the 36th Bethesda Conference on sports eligibility recommendations for athletes with cardiovascular abnormalities defines a competitive athlete as "one who participates in an organized team or sport that requires regular competition against others as a central component, places a high premium on excellence and achievement, and requires some form of systematic (and usually intense) training."[1] While this definition generally applies to younger individuals participating in high school, college, and professional sports, it may also be used to describe older athletes (> 35 years) involved in competitive master's sports programs, including individuals who first entered competitive sports at an older age.
It is well accepted in the medical community that those who fit this definition should undergo some type of preparticipation medical screening in order to determine whether any undiagnosed cardiac condition increases their risk of SCD and thus affects their eligibility to safely participate in competitive sports activities. This is particularly relevant in light of recent high-profile cases of sudden death among young athletes and the liability and legal concerns that have been raised. Physicians are increasingly being held accountable (via malpractice suits) for sports eligibility decisions that affect high school and college athletes, and this trend shows no signs of abating. For this reason, it is particularly helpful and important that physicians adhere strictly to screening guidelines set forth by the American Heart Association (AHA) and other similar professional groups. In addition, potential therapeutic options should be taken into consideration when appropriate.
Although the risk of SCD in the athletic population as a whole is not precisely known, it is believed to be quite low. In the United States, the actual number of athletes who die of cardiovascular or related causes each year is estimated to be < 300. This is a small fraction when we consider that the number of people of all ages who participate in organized sports is in the millions.[1] Although a vast majority of SCD events are believed secondary to a [VT] arrhythmia (ventricular tachycardia or ventricular fibrillation [VF]), there are other causes that occur in both the general population as well as athletes. These include acute rupture of aortic aneurysm, pulmonary embolism, and intracranial hemorrhage.
It is important to remember that SCD risk varies according to the age, underlying health, physical activity, and conditioning of the athlete. Studies suggest that the annual risk of SCD in adults is about 1:15,000 in those who participate in casual jogging vs approximately 1:50,000 in marathon runners. The risk for younger athletes, such as those who are involved in high school and college competitive sports, is estimated at 1:200,000 to 1:300,000 per school year.[2] The accuracy of these estimates has been questioned, however, and some believe they may underestimate the actual risk since the estimates are based on local incidence reports and small population studies.
SCD risk is a particular concern for older athletes, particularly those first taking up competitive sports at an older age, since the prevalence of coronary artery disease (CAD) is higher in this population and aerobic cardiovascular function naturally declines with age. The paradox in the older population is that while physical inactivity over time has been linked to a number of adverse health effects, including the development of CAD, obesity, and increased mortality, and while regular physical activity clearly has been shown to prevent or delay the progression of CAD, sudden vigorous physical exercise in people over age 40 is also associated with risks, including a higher risk of sudden death or myocardial infarction, particularly if the person is not accustomed to such activities. Although the benefits of exercise still outweigh the risks, older athletes are advised to undergo careful screening to identify any cardiac problems before participating in regular competitive sports activities.
Male athletes are more commonly afflicted with SCD than women (the male-female ratio of SCD has been estimated at up to 10:1).[3] This may be attributed to the fact that more males participate in competitive sports and there is a tendency for higher-intensity training among males. However, male gender itself may be a risk factor for sports-related SCD due to the higher prevalence of cardiac abnormalities and premature CAD in male athletes than in female athletes.[3] This is supported by studies of nonathletes. Among male nonathletes, an estimated 6% of 17% of all cases of SCD occur in association with acute exertion, while studies suggest that women have a much lower rate of exertion-related SCD -- as low as 1 in 36.5 million hours of exertion -- and this risk declines in women who engage in regular, moderate to vigorous exercise.[4]
SCD risk also may vary widely by country or geographic region, depending on ethnic and genetic variations as well as varying levels of training intensity for athletes around the world. The problem of SCD in athletes has been well studied in Italy. For instance, the results of a large, 21-year, prospective, population-based study of young athletes in the Veneto region, by Corrado and colleagues,[5] quantified the risks of physical activity in adolescents and young adults (Table 1). The results suggest that physical activity significantly increases the risk of sudden death in young adults due to undiagnosed cardiovascular conditions. The authors reported an annual sudden death incidence of 2.3 per 100,000 overall (2.62 in males and 1.07 in females) among adolescent and young adults (age 12 to 35 years) participating in competitive sports, compared with an SCD rate of 1 in 100,000 for the entire cohort of 12- to 35-year-olds in that region (both athletes and nonathletes) (Table 1). This differs significantly from US estimates, possibly as a result of the more robust, prospective study design, which provided over 2.3 million athlete-years of observation during its 21-year duration; a higher average age of athletes in the Italian series (mean age 23 years); and/or genetic and training differences between the countries.
| Athletes (n = 55) |
Nonathletes (n = 245) |
P | |
|---|---|---|---|
| Mean age (yrs) | 23.1 | 23.9 | 1.0 |
| Gender | |||
| Male | 50 | 170 | .002 |
| Female | 5 | 75 | |
| Circumstances of death | |||
| Exercise related | 49 (89%) | 22 (9%) | < .001 |
| During effort | 40 | 9 | |
| After effort | 9 | 7 | |
| Unrelated to exercise | 6 (11%) | 225 (91%) | |
| Medical history | |||
| Family history of SD | 5 (9%) | 27 (11%) | .8 |
| Previous symptoms | 18 (32%) | 56 (23%) | .2 |
| ECG abnormalities/arrhythmias | 22 (40%) | 36/63 (57%) | .1 |
ECG = electrocardiogram; SD = sudden death
The results of the Italian study are summarized in Figure 1. The rate of sudden death from cardiovascular disease was 2.1 per 100,000 athletes per year, compared with 0.7 per 100,000 nonathletes per year (relative risk, 2.8; 95% CI 1.4-2.8; P < .001). The relative risk of sudden death from all causes among athletes vs nonathletes was 2.5 (95% CI 1.8-3.4; P < .0001). It is important to remember that the actual number of SCD events was still quite low in this study. Over the 21-year study period, only 300 sudden deaths occurred in the entire 12- to 35-year-old population, which numbered nearly 1.4 million; 55 of these deaths occurred in athletes. However, the study clearly demonstrates the higher risks of sudden death by any cause and the risk of cardiovascular sudden death in young people who engage in competitive sports activities and have underlying cardiovascular diseases.
There are a number of underlying cardiac conditions that increase the risk of SCD in athletes (Table 2).[6] Congenital heart disorders are the most common associated disorders found in those under age 35 and are estimated to account for at least 40% of sudden deaths in young athletes in the United States.[7] Chief among these is hypertrophic cardiomyopathy (HCM), which is fairly common in the general population (occurring in 1 of every 500 individuals); this condition is responsible for an estimated one third of SCD cases in young athletes. Other common congenital causes include arrhythmogenic right ventricular cardiomyopathy (ARVC), Marfan syndrome, and ion channel abnormalities, such as long QT syndrome. These genetically linked diseases may account for an additional 10% of SCD cases.[8]
| Age Group | Cardiovascular Causes of SCD |
|---|---|
| Adults (age > 35 yrs) | Atherosclerotic coronary artery disease |
| Young, competitive athletes (age ≤ 35 yrs) | Hypertrophic cardiomyopathy |
| Arrhythmogenic right ventricular cardiomyopathy | |
| Myocarditis | |
| Aortic rupture | |
| Valvular disease | |
| Pre-excitation syndromes and conduction diseases | |
| Ion channel disease | |
| Congenital heart disease, operated or unoperated |
Of interest, in the prospective study performed in Italy, discussed above,[5] the most common abnormalities associated with SCD in young athletes were ARVC and premature CAD, rather than HCM, as is the case in the United States. However, as the authors point out, preparticipation screening for HCM has been well established in Italy for the past 20 years, and it has been successful in preventing SCD by restricting athletes with HCM from participating in competitive athletics. As a result, few competitive athletes in Italy have HCM. The Italian researchers also postulate that the high incidence of ARVC in the study may be due to study protocols that ensured careful postmortem morphologic examination of the heart. ARVC may often go undiagnosed during standard pathologic examination, since it rarely is associated with cardiomegaly and usually spares the left ventricle. The diagnosis of ARVC is difficult clinically,[9] but probably is less common in the United States than in Italy.
CAD is the most common disorder associated with SCD in athletes aged > 35 years, but it is less commonly found in younger athletes, at least in the United States. Older athletes also may have important undiagnosed congenital or acquired diseases that could increase their risk of sudden death, including HCM, aortic stenosis, dilated cardiomyopathy, mitral valve prolapse, and myocarditis. Moreover, older athletes are more susceptible to developing heart rhythm disturbances such as AF, sick sinus syndrome, and atrioventricular block, which can sometimes precipitate VF.
Commotio cordis is the term used for SCD caused by acute blunt trauma to the chest. This is usually caused by a hard projectile, such as a hockey puck or baseball, and results in ventricular fibrillation. Recent studies indicate that the blunt trauma occurs during the vulnerable period of cardiac repolarization triggering the arrhythmia, similar to a paced complex or low energy shock timed to the upslope of the T-wave. This is more common in young athletes and children because they have more compliant chest walls, thus transmitting the energy from the projectile to the heart. Of note, commotio cordis does not require nor is it associated with congenital heart disease or predisposition to ventricular arrhythmias.[10] This was not recognized as a cause of SCD in the older Italian series.[5]
The causes of sudden death in young athletes from the US Registry and from the Italian study are featured in Tables 3 and 4.[1,5] Note that the leading causes of sudden death were HCM and commotio cordis in the US Registry vs atherosclerotic CAD and ARVC in the Italian cohort.
| Cause | No. of Athletes (%) |
|---|---|
| Hypertrophic cardiomyopathy | 102 (26.4) |
| Commotio cordis | 77 (19.9) |
| Coronary artery anomalies | 53 (13.7) |
| Left ventricular hypertrophy of indeterminate cause | 29 (7.5) |
| Myocarditis | 20 (5.2) |
| Ruptured aortic aneurysm (Marfan syndrome) | 12 (3.1) |
| Arrhythmogenic right ventricular cardiomyopathy | 11 (2.8) |
| Tunneled (bridged) coronary artery | 11 (2.8) |
| Aortic valve stenosis | 10 (2.6) |
| Atherosclerotic coronary artery disease | 10 (2.6) |
| Dilated cardiomyopathy | 9 (2.3) |
| Myxomatous mitral valve degeneration | 9 (2.3) |
| Asthma (or other pulmonary condition) | 8 (2.1) |
| Heat stroke | 6 (1.6) |
| Drug abuse | 4 (1.0) |
| Other cardiovascular cause | 4 (1.0) |
| Long QT syndrome? | 3 (0.8) |
| Cardiac sarcoidosis | 3 (0.8) |
| Trauma causing structural cardiac injury | 3 (0.8) |
| Ruptured cerebral artery | 3 (0.8) |
*Data are from the registry of the Minneapolis Heart Institute Foundation.
?The long QT syndrome was documented on clinical evaluation.
| Cause | Total (N = 300) |
Athletes (n = 55) |
Nonathletes (n = 245) |
|---|---|---|---|
| Cardiovascular | 259 | 51 | 208 |
| Atherosclerotic CAD | 58 | 10 | 48 |
| ARVC | 37 | 12 | 25 |
| Myocarditis | 32 | 5 | 27 |
| Mitral valve prolapse | 27 | 6 | 21 |
| Disease of the conduction system | 25 | 4 | 21 |
| HCM | 23 | 1 | 22 |
| Aortic rupture | 12 | 1 | 11 |
| Dilated cardiomyopathy | 11 | 1 | 10 |
| Anomalous origin of CAD | 8 | 7 | 1 |
| Nonatherosclerotic CAD | 7 | 0 | 7 |
| Myocardial bridge | 6 | 2 | 4 |
| Aortic valve stenosis | 4 | 0 | 4 |
| Postoperative congenital heart disease | 4 | 0 | 4 |
| Pulmonary thromboembolism | 4 | 1 | 3 |
| Long QT syndrome | 1 | 1 | 0 |
| Noncardiovascular | 23 | 3 | 20 |
| Asthma | 10 | 0 | 10 |
| Cerebral berry aneurysm | 6 | 1 | 5 |
| Cerebral embolism | 5 | 2 | 3 |
| Other | 2 | 0 | 2 |
| Unexplained | 18 | 1 | 17 |
ARVC = arrhythmogenic right ventricular cardiomyopathy; CAD = coronary artery disease; HCM = hypertrophic cardiomyopathy
Strenuous sports training and the emotional stress of sports competitions can have a number of detrimental effects on the heart in patients with underlying CAD or inherited cardiac disorders. In young competitive athletes, the mechanism of SCD typically involves acute triggers that aggravate underlying structural heart disease. And intensive sports training, over time, also can produce structural changes in the heart that can aggravate preexisting conditions. Patients with HCM, for example, may experience episodes of exercise-induced ischemia during intensive training that can result in myocardial cell death and fibrosis, which can trigger electrical instability leading to VF. Similarly, patients with ARVC who engage in strenuous activity may, over a period of time, experience right ventricular volume overload and cavity enlargement leading to ventricular atrophy and ventricular arrhythmias.[7]
One of the most striking examples of how strenuous exercise can affect underlying heart abnormalities and increase the risk for SCD involves athletes with undiagnosed Wolff-Parkinson-White (WPW) syndrome. Patients with this disease experience both paroxysmal arrhythmias, such as AV reentry tachycardia, and pre-excitation due to an accessory pathway. Up to one third of individuals with WPW may also develop AF, which puts them at particularly high risk. In these patients, AF can lead to VF and sudden death as a result of rapid antegrade conduction over the accessory pathway.[7] Some studies suggest that exercise is associated with an increased risk of VF in athletes with WPW. In fact, it is estimated that half of all WPW patients experience sudden death as the first manifestation of their disease, and this usually occurs during exercise or emotional stress.[11] Overall, the risk of SCD in athletes with WPW ranges from 0.15% to 0.2%; however, symptomatic WPW patients have a higher risk, estimated at up to 2.2%.[12]
External defibrillation is the most common method of resuscitation following SCD, and automated external defibrillators (AEDs) are now widely available to both professional and school athletic departments, enabling early defibrillation during sporting events. However survival rates in athletes treated with AEDs appear to be relatively low, particularly in younger patients with inherited cardiac abnormalities. One small survey study of sports medicine specialists, presented at this year's American College of Cardiology Annual Scientific Session in Atlanta, Georgia,[13] reported an overall resuscitation rate of 63.6% (using AEDs or manual techniques delivered by sports medicine physicians) during 22 episodes of SCD in athletes. Of interest, rates of successful defibrillation were higher (71.4%) in athletes > 30 years of age and lower (50%) in those ≤ 30 years of age. As expected, the most common underlying causes of SCD were HCM in those aged ≤ 30 years and CAD in those aged > 30 years. The results suggest that underlying disorders, such as CAD, commonly found in older athletes may be more amenable to resuscitation than inherited disorders found in younger individuals. An alternative explanation is that SCD may not be recognized as quickly in young athletes, who may initially be thought to be experiencing a seizure or syncope. Such delays in treatment can reduce the efficacy of external defibrillation.
Other small studies also have noted limited early defibrillation success and poor survival rates in young, high school, and college-aged athletes, despite the use of immediate cardiopulmonary resuscitation and prompt AED. Moreover, it is important to remember that while the majority of SCD cases in athletes occur on the playing field, in some cases, life-threatening ventricular arrhythmias may arise when the athlete is at rest or asleep, when timely treatment may be difficult to obtain.
The relatively low survival rates observed in young athletes who experience sudden cardiac arrest underscore the importance of thorough preparticipation screening to identify any underlying disease prior to commencing competitive sports activities. However, preparticipation screening of athletes varies in scope and frequency worldwide, and it has a number of important pitfalls. Given the large number of athletes (estimated at 10-12 million per year)[8] who require screening and the low incidence of SCD in this population, screening tests must be carefully balanced to ensure they are cost-effective, and this requirement limits the scope of tests that can be offered. In addition, primary care physicians may have problems discerning potentially serious problems, such as subtle heart murmurs, and it may be difficult for these practitioners to decide when follow-up with a specialist is warranted. This can lead to judgment errors involving both eligibility and ineligibility decisions.
As summarized in Table 5, the AHA recommends a 12-point screening protocol for young competitive athletes that includes personal medical history to detect problems such as syncope, exertional dyspnea, or exertional chest pain; family medical history to identify premature sudden death or heart disease in close relatives; and a physical examination.[8] The latter should include assessment for heart murmur (using precordial auscultation in both supine and standing positions), femoral pulses, stigmata of Marfan syndrome, and blood pressure measurement. When potential problems are detected during this routine screening, the patient should be referred for a specialty consultation that includes noninvasive testing. It is important that all tests and diagnostic assessments be completed before the physician signs the eligibility form clearing the patient for sports participation.
| Personal Medical History | Exertional chest pain/discomfort |
| Syncope/near syncope | |
| Excessive exertional and otherwise unexplained dyspnea/fatigue associated with exercise | |
| Prior recognition of heart murmur | |
| Elevated blood pressure | |
| Family Medical History | Premature death (sudden or otherwise) related to heart disease in relatives |
| Disability from heart disease in close relative younger than 50 years of age | |
| Specific knowledge of hypertrophic or dilated cardiomyopathy, ion channelopathies such as long QT syndrome, Marfan syndrome, or clinically important arrhythmias | |
| Physical Examination | Heart murmur* |
| Femoral pulses to exclude aortic coarctation | |
| Physical stigmata of Marfan syndrome | |
| Brachial artery blood pressure (sitting position) |
*Supine and standing to identify murmur of dynamic left ventricular outflow tract obstruction.
Preparticipation screening using the above protocol is also recommended for older athletes prior to participation in masters sports training programs, ie, organized, competitive sports designed specifically for people age > 35 years. In this case, screening is used primarily to identify occult cardiovascular disease with the potential to cause SCD, myocardial infarction, stroke, or heart failure triggered by intense athletic activity or burst exertion.[2] In older athletes with a moderate-to-high risk profile for CAD who want to engage in vigorous, competitive sports activities, the addition of exercise electrocardiographic (ECG) testing is also recommended as an effective and inexpensive screening test for myocardial ischemia.
According to guidelines released jointly in 2001 by the World Heart Federation, the International Federation of Sports Medicine, and the AHA,[2] an exercise ECG screening test should be used for men > 40-45 years of age or for women > 50-55 years of age (or postmenopausal) with ≥ 1 independent coronary risk factors, such as hypercholesterolemia or dyslipidemia, elevated low-density lipoprotein cholesterol, reduced high-density lipoprotein cholesterol, systemic hypertension, current or recent cigarette smoking, diabetes mellitus, or a history of myocardial infarction or SCD in a first-degree relative aged < 60 years. Exercise testing is also recommended for masters' athletes of any age with symptoms suggestive of CAD and for all athletes aged ≥ 65 years. A positive test requires further diagnostic evaluation. It is reasonable to combine the stress test with cardiac imaging (either nuclear or echo) in those individuals with baseline ECG abnormalities that preclude accurate assessment of potential exercise-induced ischemia.
The Multiple Risk Factor Intervention Trial (MRFIT) found that asymptomatic individuals who develop a positive exercise ECG test have up to a 15 times higher risk of a future coronary event (5 times higher in women), including angina pectoris, acute myocardial infarction, or sudden death, than those who have a normal exercise ECG.[2] The Seattle Heart Watch Study reported that asymptomatic men aged > 40 years with > 1 coronary risk factor and > 2 abnormal features on exercise ECG had a 30-fold increased risk over a 5-year period.[2]
The guidelines do not endorse the use of exercise ECG testing to screen all asymptomatic masters' athletes because nonselective use in low-risk populations is associated with poor positive predictive accuracy and a high rate of false-positive tests. Nor do the guidelines recommend 12-lead ECG for use in all asymptomatic older athletes, given the variability of ECG patterns in those undergoing athletic training. However, the authors do concede the value of screening ECG to identify unexpected findings, such as a healed myocardial infarction, and genetic disorders, such as HCM, long-QT syndrome, Brugada syndrome, WPW, and ARVC. For these reasons, 12-lead ECG is recommended as part of the routine evaluation for all masters' athletes aged > 40 years.
Another test that may be used to assess older athletes is diagnostic echocardiography, which the guidelines state is indicated when clinical, historical, or physical findings suggest the possibility of valvular heart disease, HCM, ARVC, or prior myocardial infarction.[2]
Some physicians also advocate for more extensive screening in young athletes, including the use of 12-lead ECG, in order to better detect hidden cardiac disorders, particularly HCM. However, 12-lead ECG has not been included as part of routine screening recommendations in the United States, primarily because it is not believed to be cost-effective in this age group due to its low specificity.
Although 12-lead ECG is rarely used as a first-line screening tool for young athletes in the United States, it is employed frequently in some parts of Europe, for example in Italy, where a thorough preparticipation screening protocol employing 12-lead ECG, along with patient history and physical exam, has been in place for competitive athletes of all ages for over 25 years. Despite the apparent success of this program, preparticipation screening of athletes in Europe still varies considerably from country to country, with many requiring no prescreening qualification at all.
In an attempt to help standardize and improve screening protocols across Europe, the European Study Group on Sports Cardiology of the European Society of Cardiology (ESC) published a set of guidelines in 2005 that recommend strongly the implementation of 12-lead ECG as part of a preparticipation screening protocol for young athletes.[3] The guidelines, summarized in Figure 2, suggest a European standard for medical evaluation of competitive athletes that includes a complete personal and family history; physical examination, including blood pressure measurement; and 12-lead ECG as the first-line screening tests. Patients with positive findings on any of these tests should be referred for further evaluation with echocardiography, stress testing, 24-hour Holter monitoring, cardiac magnetic resonance imaging, and/or angiography, as needed.
The guidelines recommend that this screening should be repeated on a regular basis at least every 2 years. This is important, since, as others have pointed out, cardiac abnormalities associated with SCD can present at any age (HCM, for example, does not always present by early adulthood and may manifest as late-onset disease). Thus, a normal finding at any particular point has a relatively low negative predictive value for future arrhythmic events.
The European guidelines make a strong case for including 12-lead ECG as part of a routine screening protocol. According to the guideline authors, retrospective analyses that looked at athletes who died of sudden death have found that fewer than 1% received an accurate diagnosis with only a standard history and physical exam. By contrast, ECG findings are abnormal in the vast majority of patients with HCM, and abnormal ECGs also were documented in the majority of athletes who died of sudden death from ARVC.
The guidelines also point out that 12-lead ECG is more cost-effective than echocardiography for population-based screening, and the data from a previously reported Italian study by Corrado and colleagues[14] suggest that 12-lead ECG may be as sensitive as echocardiography screening in detecting HCM in young athletes. During this study, over 33,000 athletes were screened and 3016 (8.9%) were referred for echocardiographic evaluation based on a positive history, abnormal physical findings, or ECG abnormalities. Twenty-two of these athletes were diagnosed with HCM, with an estimated screening specificity of more than 90%. Overall, this study demonstrated that 12-lead ECG has a 77% greater power for detecting HCM compared with history and physical exam alone. On the basis of these data, it is estimated that the Italian screening protocol is 3 times more cost-effective than the screening protocol used in the United States.
In addition to detecting HCM, 12-lead ECG may also help physicians detect other serious abnormalities, including ARVC, dilated cardiomyopathy, long QT syndrome, Brugada syndrome, and WPW. Moreover, early CAD may produce abnormalities on ECG that could raise suspicion, although this is a less common occurrence.
Of importance, the European guidelines state that the screening evaluation should be performed by a physician with specific training to reliably identify clinical signs and symptoms associated with exercise-related sudden death. In Italy, this involves physicians who attend 4-year postgraduate residency training programs in sports medicine or sports cardiology, and who work in sports medicine centers exclusively set up for athlete screening and evaluation, a level of physician involvement currently available only to professional sports participants in the United States.
In addition to standard screening assessment tests, there are a number of new tests under development that may prove useful as risk assessment tools for athletes with CAD and other cardiac disorders. Microvolt T-wave alternans (MTWA) testing, for example, detects small variations in the T-wave on ECG that are associated with higher risk of ventricular arrhythmias and sudden death. A small Italian study (N = 43, mean age 34 years) presented at this year's Heart Rhythm Society meeting[15] demonstrated a significant correlation between an abnormal MTWA result and inducibility of ventricular arrhythmias during electrophysiologic testing (EPS) in a group of athletes who were symptomatic for ventricular tachyarrhythmias (all had experienced symptoms of frequent and complex ventricular arrhythmias, including frequent premature ventricular complexes, nonsustained VT, palpitation, syncope, or presyncope). The study also demonstrated a significant difference between athletes with positive and negative MTWA tests with regard to the occurrence of SCD, VF, and VT, suggesting that the test could be helpful for stratifying risk in this patient population. The Kaplan-Meier survival analysis showed a 100% rate of endpoint-free survival among patients with a negative MTWA test and a 62.5% rate in subjects with an abnormal (positive or indeterminate) test, suggesting that MTWA can predict spontaneous malignant arrhythmic events in athletes with ventricular arrhythmias.
In addition, there was a positive correlation between MTWA test results and EPS results. Patients with a negative MTWA test were significantly more likely to have a negative EPS study, whereas those with an "abnormal" TWA test were significantly more likely to have a positive EPS study, demonstrating good predictive value of MTWA for EPS results. The significance of the latter finding, however, is less clear, as EPS is not a marker of sudden death risk in many patient cohorts (eg, those with HCM or long-QT syndrome).
This study adds to the growing body of evidence that has come out recently in favor of MTWA as a risk-stratification tool. Earlier this year, a large, prospective, multicenter trial published in the Journal of the American College of Cardiology[16] found that MTWA testing can identify patients with heart disease who are at high and low risk of experiencing a life-threatening ventricular arrhythmia, thus helping physicians decide who best to evaluate further for implantable cardioverter defibrillator (ICD) therapy. Publication of these and other results led the Centers for Medicare and Medicaid Services in March 2006 to issue a national coverage policy for MTWA testing as a means to help stratify arrhythmia vulnerability risk.
There are many other tests used to risk-stratify for SCD. Holter monitoring has been suggested to be useful in athletes, as frequent and complex arrhythmias are more likely observed in subjects at high risk for SCD. In addition, QT dispersion, QT variability, baroreceptor sensitivity, and heart rate variability are other tests that may have predictive value for SCD in other populations. However, their role in the screening of athletes is not well defined.
If cardiac abnormalities are identified during preparticipation screening, the physician is responsible for assessing risk and determining the eligibility of the athlete to participate in competitive sports. Eligibility depends not only on the health of the participant but also upon the intensity of the sports activity under consideration and the demands it places on the heart (Figure 3).[17] Patients with cardiovascular abnormalities are not automatically excluded from competitive sports, but may be eligible to participate in some sports while being restricted from others. Another factor to consider is the emotional and stress components the athlete attaches to the activity. Even some relatively low-impact sports, such as golf, can create significant increases in blood pressure, heart rate, and myocardial contractility under competitive situations simply due to the athlete's stress level.
To aid in eligibility determination, various sports have been classified according to their static (isometric) and dynamic (isotonic) components, as shown in Figure 3.[17] This classification refers to the way the muscles are used during the activity. Most sports have both static and dynamic components, and those with either a sustained static component or a very high resistance dynamic component are classified as high-intensity exercise. Many athletes involved in sports of this type will experience increased cardiac mass and structural remodeling over time, which may adversely affect any underlying cardiac disease. Moreover, in some sports, the training is more intense than the competition itself, and this must also be considered when determining eligibility. In some cases, it may be necessary to modify the training regimen to reduce the cardiovascular impact. All eligibility determinations should be individualized to the patient.
Current guidelines for sports participation eligibility in athletes with established cardiovascular diseases were set forth by the 36th Bethesda Conference.[1] The recommendations stress that "temporary or permanent sports disqualification be confined to individual athletes with probable or conclusive evidence of disease, rather than those with only borderline findings or the presumption of a diagnosis." This follows along the lines of recommendations from other groups, most of which stress that eligibility and disqualification decisions should be conservative and follow established guidelines to avoid liability issues. Physicians should avoid disqualifying athletes from sports participation without probable or definitive evidence of disease.[8] That being said, when the evidence of disease is clear, physicians should not hesitate to recommend against sports participation. Several malpractice lawsuits have been fought over misdiagnosis and failure to disqualify athletes from competitive sports. Physicians may also be held accountable for negligence if medications are withheld in order to improve sports performance. Drugs such as beta-blockers are necessary medications for several cardiac diseases, including systemic hypertension, HCM, and long QT syndrome, but they are known to affect athletic performance adversely, and they may be contraindicated in some sports. Similarly, the efficacy and safety of antiarrhythmic drugs are unproven in athletes.
The text below summarizes the basic guidelines for patients with genetically linked cardiomyopathies, such as HCM, and those with CAD, which are among the most common problems encountered. Detailed recommendations on other conditions, including valvular disease, congenital heart defects, systemic hypertension, and arrhythmias are beyond the scope of this article.
Guidelines from the Bethesda Conference recommend a conservative approach for competitive athletes with HCM and ARVC.[18] As noted above, HCM is one of the most frequent causes of SCD in young athletes in the United States, and athletic activity in these patients has clearly been associated with increased risk. However, because the disease is diverse, there is no reliable, single factor to predict risk in these athletes. For these reasons, the guidelines stress that the goal of eligibility decisions in patients with HCM should be to encompass all preventable sudden deaths, even if that means some athletes will be excluded from sports participation unnecessarily. The guidelines state that athletes with a probable or unequivocal clinical diagnosis of HCM should be excluded from most competitive sports, with the possible exception of low-intensity (class IA) sports. This recommendation is independent of age, gender, and phenotypic appearance and does not differ with symptoms, left ventricular (LV) outflow obstruction, or prior treatment with drugs or major interventions, including placement of an ICD. Similarly, physicians are advised to exclude athletes with ARVC from most competitive sports, with the possible exception of low-intensity activities.
With regard to HCM patients who have received an ICD for primary or secondary prevention of SCD, the guidelines further point out that the potential for exercise-related changes in intravascular volume and electrolyte disturbances, neurohormonal activity, and myocardial ischemia decrease the absolute reliability of ICDs in the setting of HCM. In addition, the potential for device malfunction and the risk of traumatic injury during ICD discharge further warrant caution. As a result, the physicians are advised to exclude HCM patients with an ICD from participation in contact and most noncontact sports, with the exception of low-intensity sports.
Physicians are also advised to be conservative in their sports eligibility criteria for noncompetitive athletes with genetic cardiovascular diseases.[7] The AHA eligibility guidelines for this group are summarized in Table 6. According to the AHA panel, patients with genetic cardiovascular diseases can safely participate in most moderate or low-intensity forms of recreational exercise, but the following activities should be avoided:
| Intensity Level | HCM | LQTS | Marfan Syndrome | ARVC | Brugada Syndrome |
|---|---|---|---|---|---|
| High | |||||
| Basketball | 0 | 0 | 2 | 1 | 2 |
| Body building? | 1 | 1 | 0 | 1 | 1 |
| Ice hockey? | 0 | 0 | 1 | 0 | 0 |
| Racquetball/squash | 0 | 2 | 2 | 0 | 2 |
| Rock climbing? | 1 | 1 | 1 | 1 | 1 |
| Running (sprinting) | 0 | 0 | 2 | 0 | 2 |
| Skiing (downhill)? | 2 | 2 | 2 | 1 | 1 |
| Skiing (cross-country) | 2 | 3 | 2 | 1 | 4 |
| Soccer | 0 | 0 | 2 | 0 | 2 |
| Tennis (singles) | 0 | 0 | 3 | 0 | 2 |
| Touch (flag) football | 1 | 1 | 3 | 1 | 3 |
| Windsurfing | 1 | 0 | 1 | 1 | 1 |
| Moderate | |||||
| Baseball/softball | 2 | 2 | 2 | 2 | 4 |
| Biking | 4 | 4 | 3 | 2 | 5 |
| Modest hiking | 4 | 5 | 5 | 2 | 4 |
| Motorcycling? | 3 | 1 | 2 | 2 | 2 |
| Jogging | 3 | 3 | 3 | 2 | 5 |
| Sailing | 3 | 3 | 2 | 2 | 4 |
| Surfing | 2 | 0 | 1 | 1 | 1 |
| Swimming (lap) | 5 | 0 | 3 | 3 | 4 |
| Tennis (doubles) | 4 | 4 | 4 | 3 | 4 |
| Treadmill/stationary bicycle | 5 | 5 | 4 | 3 | 5 |
| Weightlifting (free weights)? | 1 | 1 | 0 | 1 | 1 |
| Hiking | 3 | 3 | 3 | 2 | 4 |
| Low | |||||
| Bowling | 5 | 5 | 5 | 4 | 5 |
| Golf | 5 | 5 | 5 | 4 | 5 |
| Horseback riding? | 3 | 3 | 3 | 3 | 3 |
| Scuba diving | 0 | 0 | 0 | 0 | 0 |
| Skating | 5 | 5 | 5 | 4 | 5 |
| Snorkeling | 5 | 0 | 5 | 4 | 4 |
| Weights (non-free-weights) | 4 | 4 | 0 | 4 | 4 |
| Brisk walking | 5 | 5 | 5 | 5 | 5 |
*Recreational sports are categorized with regard to high, moderate, and low levels of exercise and graded on a relative scale (from 0-5) for eligibility with 0-1 indicating generally not advised or strongly discouraged; 4-5 indicating probably permitted; and 2-3 indicating intermediate and to be assessed clinically on an individual basis. The designations of high, moderate, and low levels of exercise are equivalent to an estimated > 6, 4-6, and < 4 metabolic equivalents, respectively.
?These sports involve the potential for traumatic injury, which should be taken into consideration for individuals with a risk for impaired consciousness.
ARVC = arrhythmogenic right ventricular cardiomyopathy; HCM = hypertrophic cardiomyopathy; LQTS = long-QT syndrome
In patients with diagnosed CAD, the risk of a life-threatening event generally increases with the extent of the disease, as well as LV systolic dysfunction, inducible ischemia, and electrical instability.[19] However, in athletes with CAD, SCD is often observed in those with mild coronary stenoses or those with less extensive disease, which reduces the applicability of standard CAD risk assessment in this cohort. Risk stratification for athletes with CAD, as outlined by the 36th Bethesda Conference, involves 2 levels of risk: "mildly increased" and "substantially increased."
Those at mildly increased risk include CAD patients with:
Those classified at substantially increased risk include CAD patients with:
Coronary angiography is not required, but is recommended in athletes with exercise-induced ischemia who participate in sports against medical advice. According to the guidelines, athletes in the group at mildly increased risk are generally considered eligible to participate in low dynamic and low or moderate static competitive sports (class IA and IIA) but are recommended to avoid intensely competitive situations. These athletes should undergo a reevaluation on an annual basis. Conversely, athletes in the substantially increased risk category should generally be restricted to low-intensity competitive sports (class IA). The guidelines also stress that athletes with CAD be informed of important symptoms to be aware of during exercise, including chest, arm, jaw, or shoulder pain and unusual dyspnea) and should be told to cease their sports activity and contact their physicians if such symptoms occur.
Therapeutic options that enable athletes with cardiovascular diseases to play competitive sports are limited; however, they should be considered whenever possible. Ablation can be considered in patients with certain arrhythmias, including those with WPW who have documented paroxysmal supraventricular tachycardia and AF; these individuals have an increased risk of rapidly conducted AF and SCD. Ablation may also be considered in athletes with AF, since pharmacologic treatments, including rate-control drugs and antiarrhythmic drugs, can be problematic in athletes. For example, class I antiarrhythmics can convert AF into atrial flutter, which can conduct 1:1 to the ventricles during exercise. Coronary revascularization should be considered in those patients with documented ischemia. Similarly, surgical revascularization should be performed in those with coronary anomalies. Although surgical myomectomy or pecutaneous alcohol septal ablation can relieve outflow tract obstruction in HCM, it is unknown whether these interventions reduce the risk of SCD. Accordingly, the same restrictions on activity should be recommended after as they were before the procedure.
Increasingly, individuals at risk for SCD are receiving ICDs for primary or secondary prevention, and growing numbers of these patients are seeking to participate in recreational or even competitive sports. According to the AHA guidelines for noncompetitive sports eligibility,[7] patients with genetic cardiovascular diseases who have an ICD "may participate in a wide variety of noncompetitive and noncontact physical activities," although the presence of the ICD may restrict participation in certain sports, particularly those with a risk of bodily trauma that may disrupt the lead system, or levels of physical exertion that may trigger an inappropriate shock. The recommendations stress that young patients with these disorders receive a dual-chamber ICD with algorithms that discriminate between ventricular and supraventricular arrhythmias to reduce the risk of inappropriate shocks during exercise. In addition, the rate cutoff for therapy should be set high. Of note, dual chamber devices have shorter battery life and a higher incidence of lead complications. These factors should be considered in the choice of devices, particularly for young patients who may require multiple lifetime pulse generator replacements.
In addition to these recommendations, the 36th Bethesda Conference outlined several considerations for competitive athletes with ICDs.[1] Although conceding that little clinical evidence is available in this regard and differences of opinion exist, the panel recommended that patients with an ICD, whether for primary or secondary prevention, should be disqualified from most competitive sports, with the exception of low-intensity, class IA activities. This includes sports that potentially involve bodily trauma. The panel raised several points of concern regarding athletes with ICDs, including the possibility that the device will not perform effectively at peak exercise, the likelihood of a sinus tachycardia-triggered inappropriate shock, and the risk for physical injury to the athlete or other competitors if a shock is delivered. According to the panel, "the presence of an implantable device in high-risk patients with cardiovascular disease should not be regarded as protective therapy, and therefore a justification for permitting participation in competitive sports that otherwise would be restricted." Similarly, the panel recommended against participation by pacemaker-dependent athletes in most competitive sports that potentially involve bodily trauma that could damage the device.
Despite these conservative guidelines, a recent survey of electrophysiologists reveals that physician recommendations on sports eligibility in patients with ICDs vary widely, and many patients with ICDs do, in fact, participate in vigorous and even competitive sports, even though the safety of sports participation in this patient population is unknown.[20] Results of the survey are summarized in Figures 4 and 5 and in Table 7 . Only 10% of survey respondents said they recommend that their ICD patients avoid all sports more vigorous than golf and 42% reported that at least 1 ICD patient in their practice engaged in competitive-level sports. Forty percent of respondents said their patients had experienced ICD shocks during sports activities, but few adverse consequences were reported; the most common was lead damage attributed to repetitive-motion activities such as weight-lifting and golf. Most respondents reported that they individualize sports participation recommendations for each patient.
| Activity | Patient Participation (Any) | Patient Participation (Competitive) | Shocks Received | |||
|---|---|---|---|---|---|---|
| N | % | N | % | N | % | |
| Basketball | 163 | 27 | 92 | 15 | 70 | 11 |
| Running/jogging/track | 150 | 24 | 61 | 10 | 107 | 17 |
| Skiing (snow/water) | 96 | 16 | 12 | 2 | 42 | 7 |
| Tennis | 83 | 14 | 43 | 7 | 44 | 7 |
| Baseball/softball | 64 | 10 | 45 | 7 | 19 | 3 |
| Bicycling | 63 | 10 | 17 | 3 | 36 | 6 |
| Swimming | 57 | 9 | 22 | 4 | 38 | 6 |
| Soccer | 47 | 8 | 32 | 5 | 15 | 2 |
| Hockey | 30 | 5 | 7 | 1 | 12 | 2 |
| Football | 22 | 4 | 8 | 1 | 5 | 1 |
| Weightlifting | 17 | 3 | 3 | < 1 | 13 | 2 |
| Scuba | 12 | 2 | 0 | < 1 | 3 | < 1 |
| Hunting | 12 | 2 | 0 | < 1 | 9 | 1 |
| Volleyball | 11 | 2 | 6 | 1 | 5 | 1 |
| Rock/mountain climbing | 9 | 1 | 0 | < 1 | 5 | 1 |
| Lacrosse | 7 | 1 | 4 | < 1 | 4 | < 1 |
| Surfing/windsurfing | 7 | 1 | 1 | < 1 | 6 | 1 |
| Racquetball/squash | 6 | 1 | 6 | 1 | 3 | < 1 |
| Ice/roller skate/skateboard | 5 | 1 | 1 | < 1 | 2 | < 1 |
| Rugby | 4 | < 1 | 2 | < 1 | 1 | < 1 |
| Wrestling | 4 | < 1 | 2 | < 1 | 2 | < 1 |
| Rodeo/equestrian | 4 | < 1 | 4 | < 1 | 1 | < 1 |
| Rowing | 2 | < 1 | 2 | < 1 | 0 | 0 |
| Skydiving | 2 | 2 (<1%) | 0 | < 1 | 0 | 0 |
Values refer to the number (%) of physicians citing at least 1 patient who participates in, (first and second column) or received a shock during (third column), each sport.
The management of competitive athletes at risk for SCD is complex and challenging. These are high-visibility cases that foster intense emotions, despite a relatively low incidence. Accordingly, good patient communication and counseling are critical for optimal care. Despite the lack of controlled randomized data to guide diagnosis, treatment, and recommendations, consensus guidelines are very helpful in this setting. Such guidelines help to protect the physician from litigation risk and use the best evidence-based data available for treatment.
Supported by an independent educational grant from St. Jude Medical.
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Michael R. Gold, MD, PhD
Professor of Medicine, Medical University of South Carolina, Charleston; Chief of Cardiology, Director, Heart and Vascular Center, Medical University of South Carolina, Charleston
Disclosure: Michael R. Gold, MD, PhD, has disclosed that he has received grants for clinical research from Guidant, Medtronic, and St. Jude. Dr. Gold has also disclosed that he has served as an advisor or consultant to Guidant and Medtronic.
Ariana Del Negro
Associate Editorial Director, Medscape Cardiology
Disclosure: Ariana Del Negro has disclosed no relevant financial relationships.