The following are key points to remember from a contemporary review of sudden cardiac arrest and death in competitive and recreational athletes:

1. Defining an athlete:
   • The medical literature broadly defines athletes as people who participate in competitive sports that require systematic and intensive training; however, the definition also should include noncompetitive recreational athletes who participate in exercise or physical activities for enjoyment or to improve physical fitness.
   • Athletes span all age ranges; the term “Masters athlete” generally is used to refer to athletic individuals at least 35 years old who participate in competitively sanctioned sports or high-level sporting or recreational physical activities.
2. Historical perspective: Cardiovascular and sports science have been influenced by cases of high-visibility sudden cardiac arrest or sudden cardiac death (SCD) in athletes with resulting changes in clinical practice. Examples include:
   • The 1984 SCD of Jim Fixx, a 52-year-old runner with uncontrolled cardiovascular disease (CVD) risk factors, leading to the recognition of CVD as a risk for SCD in athletes.
   • The 1986 SCD of Flo Hyman, a 31-year-old volleyball player due to aortic dissection, leading to the recognition of aortic disease as a cause of SCD in athletes.
   • The 1990 SCD of Hank Gathers, a 23-year-old basketball player following a dose reduction of beta-blocker therapy prescribed for a history of ventricular tachycardia (VT), leading to the recognition of inadequate medical management as a risk for SCD.
   • The 2003 SCD of Marc-Vivien Foé, a 28-year-old soccer player who, like Gathers, received no early cardiopulmonary resuscitation (CPR), contributing to the recognition of the importance of an emergency action plan (EAP) in the treatment of victims of SCD.
3. Epidemiology of SCD in young athletes:
   • There are limitations in the ability to accurately measure the rates of SCD in young athletes, with available estimates between 1 in 2,400 person-years and 1 in 417,000 person-years.
   • Men have a 2-fold to 10-folder higher risk compared to women; Black athletes have an up-to-5-fold greater risk compared to White athletes; and SCD risk is higher in association with basketball, soccer, cycling, and American football compared to other sports.
4. Epidemiology of SCD in Masters athletes:
   • The majority of exercise-related SCD occurs in athletes ≥35 years old.
   • There is a so-called “exercise paradox,” such that vigorous habitual exercise reduces the risk of atherosclerotic CVD risk factors and incident disease, yet individuals with underlying CVD transiently increase the risk of an acute event during vigorous exercise.
   • Accurate estimates of the rates of SCD in Masters athletes are limited; among fully trained participants in competitive events, estimates of SCD are approximately 0.54 per 100,000 participants in half-marathons, 0.39 per 100,000 participants in marathons, and 1.74 per 100,000 participants in US triathlons.
5. Causes of SCD in young athletes:
   • Cases of SCD in competitive athletes <35 years old often are linked to inherited, structural, or congenital forms of heart disease (e.g., hypertrophic cardiomyopathy, congenital coronary artery anomalies, mitral valve prolapse with high-risk features, and arrhythmogenic cardiomyopathy), congenital and primary genetic arrhythmia syndromes (Wolff-Parkinson-White syndrome, long QT syndrome, and catecholaminergic polymorphic VT), and acquired conditions (myocarditis, commotio cordis, idiopathic myocardial fibrosis, and toxins or drugs [including performance-enhancing drugs]).
   • However, the most common cause of death among young competitive athletes is autopsy-negative sudden unexplained death.
6. Causes of SCD in Masters athletes:
   • Among Masters athletes, SCD during exercise most commonly is associated with atherosclerotic coronary artery disease (CAD).
   • Both acute plaque rupture with acute coronary syndrome and stable ischemic heart disease with demand ischemia provoking an ischemic arrhythmia are likely mechanisms for SCD in these Masters athletes.
7. Primary prevention of SCD in young competitive athletes:
   • Pre-participation evaluation should be performed for symptoms, family history, or physical findings representative of cardiac conditions associated with an increased risk of exercise-mediated SCD or underlying disease progression. However, the pre-participation evaluation is of limited sensitivity for disease detection.
   • Pre-participation 12-lead ECG can improve the ability to detect some (ion channelopathies, accessory pathways, genetic cardiomyopathies) but not all conditions (anomalous coronary origins, aortopathies, adrenergically mediated arrhythmias) associated with increased risk; but is associated with false-positives that are more common among Black athletes. There are conflicting data as to whether pre-participation ECG use is associated with improved mortality beyond the screening history and physical examination.
   • There are not sufficient data to support the use of additional testing such as cardiac imaging or exercise testing for routine athletic screening.
8. Primary prevention of SCD in Masters athletes:
   • Although routine exercise testing of asymptomatic people in the general population is not associated with reduced mortality, guidelines from some organizations recommend screening exercise testing among Masters athletes with ≥1 coronary risk factor.
   • The prognostic implications of CT-derived coronary calcium in Masters athletes are not established.
9. Secondary prevention of SCD in young competitive athletes:
   • An EAP should be emphasized for all organized competitive sports.
   • The core elements of an EAP are immediate recognition of SCD, performance of high-quality CPR, immediate access to an automatic external defibrillator (AED), and regular reviews and AED practice drills.
10. Secondary prevention of SCD in Masters athletes:
    • Masters athletes with atherosclerotic CAD who survive SCD should undergo risk stratification that includes assessment of left ventricular systolic function, residual ischemia, and inducible malignant ventricular arrhythmias. Cardiac rehabilitation and guideline-directed medical therapy should be instituted.
    • As with young competitive athletes, an EAP is a crucial component of secondary prevention for Masters athletes who suffer SCD.
11. Future directions:
    • Additional investigation is required to address unexplained racial disparities between Black and White athletes in the incidence of SCD.
    • There is a need to better identify athletes at risk of SCD, potentially including unique ECG findings.
    • Additional efforts should be made to better clarify the true incidence of SCD in young competitive athletes to help better improve primary prevention screening strategies.

Clinical Topics: Arrhythmias and Clinical EP, Prevention, Sports and Exercise Cardiology, Implantable Devices, SCD/Ventricular Arrhythmias

Keywords: Athletes, Death, Sudden, Cardiac, Heart Arrest, Primary Prevention, Secondary Prevention

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