Imagine, as a spectator at a local high school soccer game, you suddenly see a player collapse and die on the soccer field. This athlete, who was apparently healthy and in extraordinary physical condition, displayed no outward signs or symptoms leading up to the collapse. Although this tragedy seems surreal, nearly 500,000 people die each year from sudden cardiac death (SCD) either in an emergency center or without ever reaching a hospital (1).
Sudden cardiac death is defined as death resulting from an abrupt loss of heart function (1). Although coronary artery disease is the predominant cause of SCD in adults (2,3), hereditary or congenital cardiovascular structural abnormalities are usually the underlying cause in younger individuals (4) (Table). Of these congenital abnormalities, hypertrophic cardiomyopathy accounts for approximately one third of all cases of SCD (5). Hypertrophic cardiomyopathy is an inherited condition that involves enlargement of the cells of the heart muscle, especially those in the wall of the left ventricle. As a result, the main pumping chamber of the heart thickens. This abnormal growth can cause electrical conduction disturbances and threatening heart rhythms. The precise mechanism by which SCD is precipitated by exercise remains unclear; however, malignant ventricular arrhythmias are believed to be responsible for the ultimate fatality (2).
In most individuals, SCD often is the first indication of an underlying heart condition, with a fatal arrhythmic event occurring in 85% to 90% of SCD cases (6). Men account for approximately 75% of reported SCD cases (7); moreover, SCD is more common among the African American population for age-adjusted mortality rates than in other racial groups (8).
Although most cases of SCD occur in the general population who have no known history of coronary artery disease, its occurrence in children, adolescents, young adults, and athletes garners the most attention. Incidents of SCD in children, adolescents, and young adults are relatively rare, with a reported rate of 1.3 to 8.5 per 100,000 patient-years (9). Additionally, SCD occurs at a rate of 1 death per 200,000 high school-aged athletes (10). Thus, although such fatal instances are rare, these numbers still represent a considerable number of deaths in those younger than the age of 20 each year (11).
CONTEMPORARY SCREENING RECOMMENDATIONS
SCD has become a public health concern with emphasis on finding ways to reduce cardiovascular fatalities through improved screening mechanisms and providing immediate medical responses to such events. In 1996, the American Heart Association (AHA) proposed screening guidelines as a potential strategy to identify high school and college athletes who may have underlying cardiac abnormalities, putting them at an increased risk for developing SCD (12). These recommendations were updated in 2007 and include 12 items (8 personal and family history questions and 4 physical examination items) that should be part of a thorough prescreening evaluation (13). During the prescreening evaluation, positive identification of 1 or more of the 12 items serves as a trigger for a referral for a more comprehensive cardiovascular examination (13). Although these recommendations exist, there are currently no uniform laws that define the duties of sport governing bodies or educational institutions regarding preparticipation screening of athletes. In fact, in the absence of such regulations, most teams rely on either the team physician or, in the case of high school athletes, the personal physician to complete an adequate preparticipation screening. Currently, these screenings consist of personal and family histories and a brief physical examination. However, the cost-to-benefit ratio in identifying athletes at risk for SCD provided by these general screenings has been questioned.
In 2005, the European Society of Cardiology released a consensus statement recommending a uniform and systematic preparticipation screening that expanded current guidelines to include a 12-lead electrocardiogram (ECG) (14). This strategy was proposed after experiences in Italy during which mandatory medical evaluations, including 12-lead ECGs, were used to screen more than 6 million athletes (10% of the Italian population) in an effort to prevent SCD. During the initial 17-year experience (from 1979 to 1996), 33,735 young athletes from Padova, Italy, were screened, resulting in 621 (1.8%) being excluded from athletic competition because of clinically relevant cardiovascular abnormalities (14). Additionally, 3,016 (8.9%) were referred for follow-up echocardiography to rule out hypertrophic cardiomyopathy. Of this group, 22 (0.7%) were positively identified as having this significant heart abnormality (14).
As it stands, current screening practices used in the United States do not possess sufficient sensitivity to identify certain cardiac abnormalities associated with SCD. However, limitations exist with noninvasive cardiac testing that makes use of routine screenings tenuous at best. Considerations of cost, the low specificity of the ECG in identifying cardiac abnormalities in athletic populations, and the overwhelming burden on available medical resources make these screenings impractical on a large scale (13). However, the potential benefits of adding some noninvasive testing to prescreening procedures cannot be ignored.
Given that most cases of SCD do not involve athletes and that exercise and vigorous activity can acutely raise the risk for developing a cardiac event (15,16), emphasis has been placed on the emergency preparedness of fitness facilities and sporting venues, with focus on early intervention in the event of SCD. In 2002, the AHA and the American College of Sports Medicine (ACSM) (17) supplemented previously released recommendations that addressed safety concerns at health and fitness facilities. These recommendations stated that fitness facilities should possess the ability to react appropriately and rapidly to cardiovascular emergencies. Additionally, the use of preparticipation screening, planning, rehearsal for emergencies, and the placement of automated external defibrillators in all health and fitness facilities was recommended to enhance the safety of exercise(17). Unfortunately, such recommendations have not been widely adopted because low compliance has been cited in facilities, particularly with respect to preparticipation screening and emergency preparedness (18). Additionally, university-based fitness facilities also demonstrate poor compliance with the AHA/ACSM recommendations (19).
The unpredictable nature of exertion-related SCD highlights the importance of preparticipation screening and a rapid emergency response. Although uncertainty surrounds the feasibility of universal prescreening programs for athletes because of the many challenges regarding its implementation, need for follow-up evaluations, and costs, current AHA and ACSM guidelines should be widely promulgated and adhered to. Although our ability to accurately identify individuals who are susceptible to SCD remains imperfect, the implementation of a well-planned and rehearsed emergency response algorithm, including the availability and use of an automated external defibrillator, should assist in reducing the number of exercise-related fatalities each year. The challenge is yours!
1. Nabel, E.G. Cardiovascular disease. The New England Journal of Medicine
2. Maron, B.J., S.E. Epstein, and W.C. Roberts. Causes of sudden death in competitive athletes. Journal of the American College of Cardiology
3. Roberts, W.O., and B.J. Maron. Evidence for decreasing occurrence of sudden cardiac death associated with the marathon. Journal of the American College of Cardiology
4. Maron, B.J., J. Shirani, L.C. Poliac, et al. Sudden death in young, competitive athletes: clinical, demographic, and pathological profiles. The Journal of the American Medical Association
5. Maron, B.J. Hypertrophic cardiomyopathy: a systemic review. The Journal of the American Medical Association
6. Myerburg, R.J., K.M. Kessler, and A. Castellanos. Sudden cardiac death. Structure, function, and time-dependence of risk. Circulation
85(1 suppl):I2-10, 1992.
7. Zipes, D.P., and H.J. Wellens. Sudden cardiac death. Circulation
8. Centers for Disease Control and Prevention (CDC). State-specific mortality from sudden cardiac death-United States, 1999. MMWR Morbidity and Mortality Weekly Report
9. Liberthson, R.R. Sudden death from cardiac causes in children and young adults. The New England Journal of Medicine
10. Basso, C., B.J. Maron, D. Corrado, et al. Clinical profile of congenital coronary artery anomalies with origin from the wrong aortic sinus leading to sudden death in young competitive athletes. Journal of the American College of Cardiology
11. Turakhia, M., and Z.H. Tseng. Sudden cardiac death: epidemiology, mechanisms, and therapy. Current Problems in Cardiology
12. Maron, B.J., P.D. Thompson, J.C. Puffer, 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
13. Maron, B.J., P.D. Thompson, M.J. Ackerman, et al. Recommendations and considerations related to preparticipation screening for cardiovascular abnormalities in competitive athletes: 2007 update: a scientific statement from the American Heart Association Council on Nutrition, Physical Activity, and Metabolism: endorsed by the American College of Cardiology Foundation. Circulation
14. Corrado, D., A. Pelliccia, H.H. Bjornstad, et al. Cardiovascular pre-participation screening of young competitive athletes for prevention of sudden death: proposal for a common European protocol: consensus statement of the Study Group of Sport Cardiology of the Working Group of Myocardial and Pericardial Diseases of the European Society of Cardiology. European Heart Journal
15. Siscovick, D.S., N.S. Weiss, R.H. Fletcher, et al. The incidence of primary cardiac arrest during vigorous exercise. The New England Journal of Medicine
16. Albert, C.M., M.A. Mittleman, C.U. Chae, et al. Triggering of sudden death from cardiac causes by vigorous exertion. The New England Journal of Medicine
17. Balady, G.J., B. Chaitman, C. Foster, et al. Automated external defibrillators in health/fitness facilities: supplement to the AHA/ACSM recommendations for Cardiovascular screening, staffing, and emergency policies at health/fitness facilities. Circulation
18. McInnis, K., W. Herbert, D. Herbert, et al. Low compliance with national standards for cardiovascular emergency preparedness at health clubs. Chest
19. Herbert, W.G., D.L. Herbert, K.J. McInnis, et al. Cardiovascular emergency preparedness in recreation facilities at major US universities: college fitness center emergency readiness. Preventive Cardiology
American College of Sports Medicine and American Heart Association. Exercise and Acute Cardiovascular Events: Placing the Risks into Perspective: Joint Position Stand. Medicine & Science in Sports & Exercise®
39(5):886-897, 2007. View free online at www.acsm-msse.org
and click on "Position Stands."