SOCHIPE - Soc. Chilena de Pediatría



Sudden cardiac death in young athletes

Causes, athlete's heart, and screening guidelines

Jonathan A. Drezner, MD

VOL 108 / NO 5 / OCTOBER 2000 / POSTGRADUATE MEDICINE

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CME learning objectives

* To review the causes of sudden cardiac death in young athletes

* To understand the physiologic changes seen in so-called athlete's heart

* To recognize key features of the preparticipation sports evaluation

The author discloses no financial interests in this article.

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Preview: The sudden, unexpected death of a young athlete from a cardiac cause, while rare, often captures the public's attention and raises questions about the need for more comprehensive screening before athletes are allowed to participate in vigorous sports. In this article, Dr Drezner addresses the questions surrounding such tragedies and discusses the causes of sudden cardiac death, the physiologic adaptations seen in so-called athlete's heart, and guidelines for cardiovascular screening.

Drezner JA. Sudden cardiac death in young athletes: causes, athlete's heart, and screening guidelines. Postgrad Med 2000;108(5):37-50

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When a young athlete dies unexpectedly, the impact often extends beyond the local community and medical establishment to attract regional and national media attention. As a result, primary care and sports medicine physicians are often asked to screen athletes for relatively rare cardiac-related diseases that may predispose an athlete to sudden death.

Physicians involved in the care of athletes play the dominant role in prevention of sudden cardiac death and should be familiar with its various causes and the current recommendations for screening of athletes before their participation in sports.

This article outlines the major causes of sudden cardiac death, reviews the physiologic cardiovascular adaptations seen in so-called athlete's heart, and defines key features of the preparticipation sports evaluation.

Background and prevalence

Sudden cardiac death in an athlete has been defined as nontraumatic and unexpected sudden cardiac arrest that occurs within 6 hours of a previously normal state of health (1). In athletes less than 35 years of age, congenital cardiovascular disease is usually responsible. This catastrophic event typically occurs during or shortly after training or competition, suggesting that intense physical exertion is a precipitating factor (2). Recently, the list of recognized cardiovascular risks during athletic competition has been expanded to include cardiac arrest resulting from blunt trauma to the chest wall in the absence of underlying cardiovascular disease (3).

The earliest documented case of sudden cardiac death occurred in 490 BC, when Pheidippides, a Greek soldier and conditioned runner, ran from Marathon to Athens to announce military victory over Persia, only to deliver his message, then collapse and die (4). More recently, the sudden deaths of a number of high-profile athletes--Olympic gold medal skater Sergei Grinkov in 1995, professional basketball player Reggie Lewis in 1993, college basketball player Hank Gathers in 1990, Olympic volleyball champion Flo Hyman in 1986--have received national publicity, raising public interest in this infrequent event. Young competitive athletes are generally perceived as the healthiest segment of our society, and their unexpected collapse often sparks public debate on prevention of sudden cardiac death and the appropriateness of established screening guidelines.

Fortunately, sudden cardiac death in young athletes is rare. Its exact prevalence is unknown, since there is no national database to track death in athletes. The largest available studies estimate the risk among high school and collegiate athletes to be between 1 per 100,000 and 1 per 300,000 each year (5-7). An estimated 50 to 100 cases occur in the United States annually (6,8).

Researchers have also found that sudden cardiac death is about five times more common in males than in females (5). The incidence increases in persons over 35 years of age, largely because of the increasing prevalence of atherosclerotic heart disease. Estimates of the incidence in the older population of joggers or people who exercise vigorously range from 1 per 15,000 to 1 per 18,000 (9,10).

Causes of sudden cardiac death

Most cases of sudden cardiac death in young people are secondary to congenital cardiac abnormalities. The common denominator in all cases is the development of electrical instability that leads to a fatal arrhythmia (8). Table 1 lists the various causes of sudden cardiac death in young athletes.

Table 1. Causes of sudden cardiac death in young athletes

Most common

Hypertrophic cardiomyopathy

Idiopathic left ventricular hypertrophy

Congenital coronary artery anomalies

Less common

Ruptured aortic aneurysm

Myocarditis

Dilated cardiomyopathy

Arrhythmogenic right ventricular dysplasia

Aortic valve stenosis

Tunneled left anterior descending coronary artery

Atherosclerotic coronary artery disease

Rare

Wolff-Parkinson-White syndrome

Long QT syndrome

Mitral valve prolapse

Commotio cordis

Drugs

Unknown/other

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Hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy is the most common cause of sudden cardiac death in young competitive athletes. Maron and associates (2) studied autopsy results of 134 athletes who died of cardiovascular causes and found that hypertrophic cardiomyopathy accounted for 36% of the deaths. This familial autosomal dominant disorder has variable expression. Its prevalence is 1 per 500 in the general US population and higher in blacks (11). Researchers have found more than 100 mutations in genes encoding proteins for the cardiac sarcomere that result in hypertrophic cardiomyopathy (3).

Characteristic morphologic features of hypertrophic cardiomyopathy include asymmetric left ventricular hypertrophy (usually involving the ventricular septum), left ventricular wall thickness of 16 mm or more (normal, ................
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