Sudden Cardiac Death in Competitive Athletes Christopher A. McGrew, MD 1

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udden cardiac death (SCD) in athletes has been defined as an ‘‘unexpected sudden cardiac death that occurs within 6 hours of a previously normal state of health.’’7 Competitive athlete has been defined as ‘‘one who participates in an organized team or individual sport that requires competition against others as a central component, places a high premium on excellence and achievement, and requires some form of systematic training.’’11 An important facet of determining competitive activity is whether the athlete is able to use proper judgment in assessing when to appropriately extricate himself (or herself) from the event should that become necessary.8

EPIDEMIOLOGY There is a large reservoir of competitive athletes in the United States, with approximately 5 million participants at the high school, college, and professional levels. This does not include an unspecified number of competitors at the youth, middle school, and masters levels, for which reliable numbers are not available.10 Despite this large number of competitors, sudden death in an athlete, especially a young athlete, is a rare event. Estimates vary greatly depending on the age of the athlete, the source of the sampling population, the sports activity, and the definition of sudden death. Studies from the National Center for Catastrophic Sports Injury Research15 identified 160 nontraumatic athlete deaths in high school and college organized sports between July 1983 and June 1993, of which 88% were of cardiac etiology. The estimated incidence of sudden death in this group of competitive athletes was 7.47:1 000 000 per year in males and 1.33:1 000 000 per 1

Professor, Department of Orthopedics and Rehabilitation, Department of Family and Community Medicine, University of New Mexico Health Sciences Center, Albuquerque, NM. Send correspondence to Christopher McGrew, Department of Orthopedics and Rehabilitation, Department of Family and Community Medicine, University of New Mexico Health Sciences Center, 2211 Lomas NE, Albuquerque, NM 87106. Email: [email protected]

Journal of Orthopaedic & Sports Physical Therapy

ETIOLOGIES The causes of SCD in competitive athletes are represented by a variety of cardiovascular abnormalities and lesions. In the athlete greater than 35 years of age, far and away the most common cause of SCD death is atherosclerotic coronary artery disease. In the younger athlete (less than 35 years of age), the vast majority of sudden deaths are due to several congenital cardiac malformations along with a variety of other lesions (Table 1).10 Other than a ruptured aortic aneurysm, the final common pathway for death in these lesions noted in Table 1 is the development of a malignant and ultimately fatal arrhythmia. Some of the more common conditions are discussed briefly below: 589

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Key Words: arrhythmia, cardiovascular system, heart disease, medical screening

year in females. Additionally, the study noted that the majority of these deaths came in football and basketball.15 In older athletes, estimates of the frequency of sudden cardiac death may exceed that of younger athletes with a range of 1:15 000 to 1:50 000 per year in those over 35 years of age. (As in the younger group, a disproportionate number of these deaths are in males.) Considering such a relatively low prevalence, the heightened awareness and intense interest in sudden death in athletes often fueled by the news media is out of proportion to its actual impact as a public health concern.9

CLINICAL

Sudden cardiac death in competitive athletes is a rare event in spite of the large numbers participating in organized sports. These tragic episodes usually receive significant media coverage and stimulate intense discussion in the lay and medical communities about how future occurrences might be avoided. This clinical commentary will review a variety of issues concerning sudden cardiac death in competitive athletes, including epidemiology, causes, screening methods, and potential for prevention. J Orthop Sports Phys Ther 2003;33:589-593.

TABLE 1. Causes of sudden cardiac death in competitive athletes less than 35 years of age. Most Common • • •

Hypertrophic cardiomyopathy Congenital coronary anomalies Myocarditis Less Common

• • •

Idiopathic left ventricular hypertrophy Dilated cardiomyopathy Ruptured aortic aneurysm (associated with Marfan’s syndrome) Aortic valvular stenosis Arrhythmogenic right ventricular dysplasia Atherosclerotic coronary artery disease Wolff-Parkinson-White syndrome Long QT syndrome Mitral valve prolapse Commotio cordis Substance abuse (eg, cocaine) Unknown

• • • • • • • • •

TABLE 2. History and physical exam components. Journal of Orthopaedic & Sports Physical Therapy® Downloaded from www.jospt.org at on January 25, 2017. For personal use only. No other uses without permission. Copyright © 2003 Journal of Orthopaedic & Sports Physical Therapy®. All rights reserved.

History Questions for Cardiovascular Screening • • •

Previous chest pain or discomfort with exercise? Syncope or near syncope with exercise? ‘‘Unusual,’’ excessive, or unexpected shortness of breath and/or fatigue with exercise? Heart murmur or increased blood pressure? Close relative developed significant disability or died before age 50 from cardiovascular disease? Anyone in family with heart conditions such as hypertrophic cardiomyopathy, dilated cardiomyopathy, long QT syndrome, Marfan’s syndrome, or arrhythmias?

• • •

Physical Exam: Key Points • •

Brachial blood pressure in the sitting position Precordial auscultation in both supine and standing positions Assessment of femoral artery pulses to rule out coarctation of the aorta Recognition of physical stigmata of Marfan’s syndrome

• •

• Hypertrophic cardiomyopathy (HCM) is an autosomal-dominant congenital disorder characterized by left ventricular outflow obstruction with asymmetric septal hypertrophy and marked disarray of ventricular muscle fibers. HCM is of great importance because it is probably the most common cause of sudden cardiac death in athletes. This condition can predispose individuals to malignant ventricular arrhythmias leading to syncope or sudden death either at rest or with exertion. HCM is often clinically silent, but a personal or family history of unexplained syncope, especially effort syncope or sudden-death events, is an important clinical clue. The physical exam may reveal a murmur that increases when the athlete moves from the supine to the standing position. The diagnosis is best confirmed 590

with 2-dimensional and M-mode echocardiography.12 • Congenital coronary anomalies include a variety of abnormal anatomical variations of the right and left coronaries as well as hypoplastic vessels. These anomalies are rarely identified because patients usually do not experience warning symptoms and noninvasive diagnosis is difficult. Sudden death is often the first manifestation of this condition. These abnormalities should be considered in athletes with exertional syncope or nearfatal arrhythmias. Detailed echocardiography may give clues, but usually congenital coronary anomalies are confirmed through angiography.3 • Acute myocarditis is a rare but potentially devastating condition that is most commonly caused by viruses. Coxsackie B virus has been implicated in 50% of cases.1 Myocarditis is probably underrepresented in statistics on sudden cardiovascular death in athletes. Myocarditis is suspected clinically by manifestations of fatigue, exertional dyspnea, syncope, palpitations, arrhythmias, or acute congestive heart failure in the presence of left ventricular dilation. • Atherosclerotic coronary artery disease is the most common cause of sudden cardiac death in the athlete greater than 35 years of age. Attention to risk factors and to the early symptoms of ischemia, angina, and other effort-related symptoms should be just as aggressively pursued in younger athletes as in older athletes.

SCREENING Ideally, the purpose of screening is to provide medical clearance for participation in competitive sports through routine and systematic evaluations intended to identify clinically relevant and preexisting cardiovascular abnormalities and thereby theoretically reduce the risks associated with competitive sports. The use of screening tests, however, should be evaluated by epidemiological criteria for determining effectiveness and not merely by media or public opinion. Screening strategies for the prevention of SCD in competitive athletes is put into perspective by estimating disease prevalence and the sensitivity and specificity of the screening tests. It has been estimated that 200 000 competitive asymptomatic athletes would need to be screened to potentially identify 1 athlete who would die as a result of competition.2 Even if there was a very precise tool to screen for sudden death with a sensitivity and specificity of 99%, the low prevalence of disease would yield a positive predictive value of only 0.05%. In other words, only 1 positive test out of every 2000 would be correctly positive and 1999 would be falsely positive.12 J Orthop Sports Phys Ther • Volume 33 • Number 10 • October 2003

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TABLE 3. Physical stigmata of Marfan’s syndrome. Skeletal • • • • •

Arm span greater than height Chest wall deformities Kyphoscoliosis High-arched palate Hyperextensible joints Cardiovascular

• •

Murmur of aortic regurgitation Murmur of mitral regurgitation Ocular

• •

Myopia Ectopia lentis (dislocated lens)

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J Orthop Sports Phys Ther • Volume 33 • Number 10 • October 2003

clinically important arrhythmias. Additionally, in athletes over 35 years of age, personal histories of coronary risk factors should be emphasized (eg, elevated cholesterol, diabetes, family history). The guidelines promulgated by the AHA acknowledged that the accuracy of some responses from young athletes might depend on their level of compliance and knowledge of their past medical history. Younger athletes (less than 18 years of age) should complete the history in conjunction with a parent or guardian, if possible. The cardiovascular physical examination should include, but not necessarily be limited to, the following: precordial auscultation to identify heart murmurs, assessment of the femoral artery pulses to exclude coarctation of the aorta, recognition of the physical stigmata of Marfan’s syndrome3 (Table 3), and brachial blood pressure measurement in the sitting position. Auscultation should be done in both the supine and standing positions to identify any particular heart murmurs consistent with dynamic left ventricular outflow obstruction (eg, hypertrophic cardiomyopathy). A proper setting (ie, private and quiet) that allows appropriate auscultation is obviously important. When cardiovascular abnormalities are identified or suspected on screening, the athlete should undergo further evaluation by testing such as an electrocardiogram, exercise stress testing, and echocardiography. Selective exercise testing in men older than 40 and women older than 50 who plan to engage in regular physical training and competitive sports may be indicated if the clinician suspects coronary artery disease on the basis of risk factors. (Older athletes should be routinely counseled about prodromal cardiovascular symptoms such as exertional chest pain.) The AHA cardiovascular preparticipation screening guidelines state that it is not reasonable to recommend the routine use of noninvasive testing, such as exercise stress testing or echocardiography, without

CLINICAL

The American Heart Association (AHA) has published a scientific statement that specifically addresses the need for a rational and cost-effective strategy for the cardiovascular component of a preparticipation exam.9 Key components of this strategy include focused areas of the history and physical exam. (It should be remembered that screening for cardiovascular disease is usually part of a more general preparticipation physical exam.) It is generally accepted that a standardized screening program by history and physical exam alone will not guarantee detection of many critical cardiovascular abnormalities in large populations of apparently healthy athletes. However, the AHA recommends that this still be done and is justifiable based on ‘‘ethical, legal, and medical grounds.’’ Noninvasive testing can enhance the diagnostic power of the standard history and physical exam; however, it is not reasonable to recommend routine use of such tests as 12-lead electrocardiography, echocardiography, or graded exercise testing for detection of cardiovascular disease in large populations of athletes given the sensitivity and specificity values mentioned above. The AHA recommends that athletic screening be performed by a health care worker with ‘‘the requisite training, medical skills, and background to reliably obtain a detailed cardiovascular history and perform a physical examination and recognize heart disease.’’10 Part of the qualifications for those doing the examinations is an awareness of the normal variations resulting from adaptations to physical training, also known as the ‘‘athletic heart syndrome.’’ The higher vagal tone associated with training may result in bradyarrhythmias, including marked sinus arrhythmia, atrialventricular disassociation with junctional escape rhythm, intermittent types I and II atrioventricular (AV) blocks, and, in rare cases, intermittent third-degree block. The higher forms of AV block can be considered normal variants only if they are transient and disappear with exercise. On physical exam, these arrhythmias can translate to hyperdynamic carotid pulses due to bradycardia and increased stroke volume. The third and fourth heart sounds may also be a normal adaptation to training. The highly trained athlete can also exhibit a variety of alterations on the electrocardiogram.4 Key questions in the cardiovascular screening history should include those that would determine prior occurrence of syncope or near syncope associated with exercise, chest pain or unexpected and unexplained shortness of breath or fatigue associated with exercise, past detection of a heart murmur or increased blood pressure, family history of premature death or significant disability from cardiovascular disease in a close relative younger than 50 years of age, and the occurrence of certain conditions such as hypertrophic cardiomyopathy, dilated cardiomyopathy, Marfan’s syndrome, long QT syndrome, or

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specific indications from the history or physical exam. This recommendation is based on both practicality and cost efficiency, along with the low rate of SCD in athletes and the relatively low frequency of the cardiovascular lesions responsible for these rare deaths. The AHA guidelines also note that despite the ability of noninvasive testing to enhance the diagnostic power of the standard history and physical examination, ‘‘widespread use of noninvasive testing in athletic populations would likely result in a good deal more false positives than true positive results.’’10 On a final note, it is important to make an effort to increase the general public’s awareness about the limitations associated with the preparticipation screening of competitive athletes to avoid misconceptions about the principle and efficacy of the screening process. It is not possible to achieve a zero-risk circumstance in competitive sports and consequently there is implied acceptance of risk on the part of athletes (and their guardians if they are not of legal age).5 It must be made clear to all involved parties that passing a preparticipation sports screening exam is not a guarantee of freedom from potentially silent disease processes that could result in sudden death. In a retrospective study8 of 134 athletes who suffered sudden cardiac death, 115 had undergone standard preparticipation screening and 15 had undergone individualized medical evaluation for heart disease. Among these, an accurate diagnosis was made in only 8 (6%) of athletes prior to death.9

PREVENTION Prevention of all or most sudden cardiac death in competitive athletes is a laudable, but probably impossible, goal to achieve. It is reasonable that the current status of prevention can be improved, however. Two areas are theoretically the most important to address. One is primary screening and the other is secondary prevention after recognition of the athlete with cardiovascular disease.

Primary Screening It would seem reasonable that adherence to the AHA guidelines for preparticipation cardiovascular screening, despite acknowledged limitations, would somewhat improve detection of athletes at risk. According to a recent study by Pfister et al,13 a small minority of the institutions surveyed adhered to these guidelines. Unfortunately, there are no published evidenced-based studies to support the assumption that uniform screening can reduce sudden cardiac death in competitive athletes. Continued research is necessary, especially with respect to such issues as the optimal frequency for exams, the most appropriate questionnaire, and the role of noninvasive investigations and procedures. 592

Secondary Intervention Appropriate management of those athletes with known cardiovascular disease should theoretically decrease the likelihood of sudden death during competitive athletics. (Obviously, this would be the case if the athlete was disqualified from competition completely.) Cardiovascular abnormalities should be evaluated with respect to the 26th Bethesda Conference7 consensus panel recommendations for the final determination of eligibility for future athletic competition. The Bethesda report classifies individual sports according to the type and intensity of exercise and the danger of bodily injury from collision or the consequences of syncope. This detailed, comprehensive report provides useful guidance to physicians with regard to the acceptable medical risks of athletic participation in patients with known cardiovascular abnormalities. Further research is needed in the area of risk stratification within the group of athletes with hypertrophic cardiomyopathy to determine whether some of these athletes are potentially safe to participate in competitive sports. Additionally, it would be helpful to have prospective studies which follow athletes who have been disqualified from organized competitive sports because of cardiovascular conditions to record their natural history of physical activity and participation in strenuous, but not necessarily ‘‘officially organized,’’ activity. Finally, the use of automated external defibrillators (AEDs) in the athletic competition setting merits further study, because in nearly all cases the final premorbid event of sudden death in athletes is ventricular fibrillation. The chance of survival after cardiac arrest from ventricular fibrillation decreases by 10% for every minute that defibrillation is delayed and AEDs have been shown to improve outcomes in sudden arrhythmic collapses in the general population (usually suffering from typical coronary artery disease) outside of hospitals.14 At this time, AEDs have not yet proven to be effective in athletic-related sudden death (primarily the younger athlete suffering from a congenital condition or myocarditis) and their expense is still a barrier for many institutions.

SUMMARY The sudden death of a competitive athlete is usually a dramatic and highly publicized tragedy. It must be emphasized, however, that the prevalence of cardiac disease is low in athletes and that sudden death in competitive athletes is a very rare event, despite public perceptions fueled by media coverage. Common causes include a relatively small number of predictable pathologies with differences primarily based on the age of the athlete. Screening for athletes is likely to be a low-yield process given the low prevalence of disease and the limitations of the screening process, but at the very least, a standardJ Orthop Sports Phys Ther • Volume 33 • Number 10 • October 2003

ized approach, as outlined by the AHA,9,10 should be adopted. For those athletes with known cardiovascular conditions, the 26th Bethesda guidelines7 are a good starting point for evaluation and management of participation questions.

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11. 12. 13. 14.

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1. Batra AS, Lewis AB. Acute myocarditis. Curr Opin Pediatr. 2001;13:234-239. 2. Epstein SE, Maron BJ. Sudden death and the competitive athlete: perspectives on preparticipation screening studies. J Am Coll Cardiol. 1986;7:220-230. 3. Graham TP, Jr., Bricker JT, James FW, Strong WB. 26th Bethesda conference: recommendations for determining eligibility for competition in athletes with cardiovascular abnormalities. Task Force 1: congenital heart disease. Med Sci Sports Exerc. 1994;26:S246-253. 4. Huston TP, Puffer JC, Rodney WM. The athletic heart syndrome. N Engl J Med. 1985;313:24-32. 5. Maron BJ, Brown RW, McGrew CA, Mitten MJ, Caplan AL, Hutter AM, Jr. Ethical, legal and practical considerations affecting medical decision-making in competitive athletes. J Am Coll Cardiol. 1994;24:854-860. 6. Maron BJ, Mitchell JH. Revised eligibility recommendations for competitive athletes with cardiovascular abnormalities. Med Sci Sports Exerc. 1994;26:S223-226. 7. Maron BJ, Shirani J, Poliac LC, Mathenge R, Roberts WC, Mueller FO. Sudden death in young competitive

CLINICAL

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REFERENCES

athletes. Clinical, demographic, and pathological profiles. JAMA. 1996;276:199-204. Maron BJ, Thompson PD, Puffer JC, et al. Cardiovascular preparticipation screening of competitive athletes. A statement for health professionals from the Sudden Death Committee (clinical cardiology) and Congenital Cardiac Defects Committee (cardiovascular disease in the young), American Heart Association. Circulation. 1996;94:850-856. McGrew CA. Clinical implications of the AHA preparticipation cardiovascular screening guidelines. Athl Ther Today. 2000;5:52-56. Mitchell JH, Maron BJ, Epstein SE. 16th Bethesda Conference: Cardiovascular abnormalities in the athlete: recommendations regarding eligibility for competition. October 3-5, 1984. J Am Coll Cardiol. 1985;6:11861232. Maron BJ, Epstein SE, Roberts WC. Causes of sudden death in competitive athletes. J Am Coll Cardiol. 1986;7:204-214. O’Connor FG, Kugler JP, Oriscello RG. Sudden death in young athletes: screening for the needle in a haystack. Am Fam Physician. 1998;57:2763-2770. Pfister GC, Puffer JC, Maron BJ. Preparticipation cardiovascular screening for US collegiate student-athletes. JAMA. 2000;283:1597-1599. Valenzuela TD, Roe DJ, Nichol G, Clark LL, Spaite DW, Hardman RG. Outcomes of rapid defibrillation by security officers after cardiac arrest in casinos. N Engl J Med. 2000;343:1206-1209. Van Camp SP, Bloor CM, Mueller FO, Cantu RC, Olson HG. Nontraumatic sports death in high school and college athletes. Med Sci Sports Exerc. 1995;27:641647.