Incidence of SCD in athletes: estimates vary 10-fold!

SCD is the leading cause of death in young athletes.1 However, the exact incidence of SCD is unknown, and it is difficult to compare incidence studies with profoundly different methodology and from widely different geographic locations. Estimates from the US range from 1:160 000 to 1:300 000 competitive athlete deaths per year due to cardiovascular diseases.1 2 These studies, while rigorous in effort, rely primarily on search of public media reports and other electronic databases and are at risk of underestimating the incidence of SCD due to the lack of a mandatory reporting system. In contrast, the Veneto region of Italy utilises a regional registry for juvenile sudden death and reported a SCD incidence of 1:28 000 for young competitive athletes (ages 12–35 years) prior to implementing a national screening program.3 Similarly, a recent prospective population-based study conducted at 11 US and Canadian cities found an incidence of SCA from cardiovascular disease of 1:27 000 in children and young adults (ages 14–24).4 Thus, initial reports may have vastly underestimated the magnitude of the problem of SCD in athletes.

It is essential that the sports medicine community clarifies the purpose of cardiovascular screening in athletes. Is the goal of screening simply to prevent SCD? Or is the goal of screening to identify children at risk with cardiovascular disorders that can be managed via medical intervention and activity modification to reduce their risk of sudden death? The American College of Cardiology contends that the ultimate objective of preparticipation screening of athletes is the detection of “silent” cardiovascular abnormalities that can lead to SCD.5 From a primary screening perspective, perhaps it is the prevalence of cardiovascular conditions with the potential for sudden death that should heavily guide our screening procedures. The combined disease prevalence of all cardiovascular disorders that predispose young athletes to SCD is estimated at 0.3% (1:333).6 In contrast to the disparities surrounding SCD incidence, this prevalence has been confirmed in many studies using ECG screening where the true positive rate for identified cardiovascular diseases ranges from 0.2% to 0.4%.3 7 8

When evaluating the potential value or limitation of including ECG in a screening protocol, it is critical to recognise that the total positive and false positive rates for any ECG screening study or practice is immensely affected by the criteria chosen to define “abnormal.” In this issue Corrado and colleagues9 present a comprehensive review on the interpretation of the ECG in athletes. Johnson and Ackerman10 also provide a persuasive report on the QTc interval, and Maron11 summarises methods to distinguish physiological from pathological hypertrophy in athletes. These references provide a modern framework to improve screening procedures in young athletes.

Time to update ECG norms?

There is an urgent need for uniform terminology when describing ECG findings in athletes. Many ECG changes once referred to as “abnormal” are now recognised as physiological and part of benign cardiac adaptation in athletes. Doctors interpreting ECGs in athletes should be familiar with common training-related ECG alterations that are normal variants. In contrast, training-unrelated ECG changes suggest the possibility of underlying pathology, require further diagnostic investigation and should be considered abnormal. In this issue, Papadakis and Sharma12 suggest that applying modern, strict ECG criteria to screen athletes can result in a low and acceptable false positive rate.

Although the debate over different screening strategies remains impassioned, it is important to appreciate that the international sports medicine community has more common purpose than it does dissent with respect to preventing SCD. There is universal agreement that SCD is catastrophic, athletes are at increased risk, effective prevention is critical and screening for occult disease is important. And, even though the precise frequency of SCD in athletes remains disputed, there is general agreement that vigorous exercise is a trigger for SCD in athletes with underlying cardiac disease.

Many challenges remain regarding SCD prevention that must be addressed through further education and research. Unfortunately, even past screening recommendations that are universally accepted, such as the use of a comprehensive personal and family questionnaire to guide the preparticipation evaluation, have not been widely adopted. Doctors conducting these evaluations should be aware of the warning symptoms and family history that may indicate the presence of a lethal cardiovascular abnormality. In addition, to effectively implement ECG screening, complex issues regarding infrastructure, cost, feasibility and doctor education must be addressed through further study. To confront these challenges we must move beyond a debate grounded in incidence estimates and false positive rates that derive from studies with vastly different methodology and terminology. While the horizon for prevention of SCD looks promising, significant work still lies ahead.

BJSM and the IOC, partners in promoting the health of sportspeople the world over, look forward to your responses via the BJSM blog, (http://blogs.bmj.com/bjsm), emails, or manuscript submissions. And please note that the IOC World Conference on Prevention of Injury and Illness in Sport, (http://www.ioc-preventionconference.org) in Monaco, 7–9 April 2011, will have SCD as one of its focus areas.