An estimated 1 to 3/100,000 apparently healthy young athletes die suddenly during exercise. Males are affected up to 10 times more often than females. Basketball and football players in the US and soccer players in Europe may be at highest risk (1 General references An estimated 1 to 3/100,000 apparently healthy young athletes die suddenly during exercise. Males are affected up to 10 times more often than females. Basketball and football players in the... read more ).
In young athletes, sudden cardiac death has many causes (see table Causes of Sudden Cardiovascular Death in Young Athletes Causes of Sudden Cardiovascular Death in Young Athletes 
). The most common cause of sudden cardiac death was thought to be hypertrophic cardiomyopathy Hypertrophic Cardiomyopathy Hypertrophic cardiomyopathy is a congenital or acquired disorder characterized by marked ventricular hypertrophy with diastolic dysfunction (eg, due to valvular aortic stenosis, coarctation... read more 
. More recent studies suggest that hypertrophic cardiomyopathy accounts for a lower proportion of sudden cardiac deaths and that the majority of sudden cardiac deaths occur in patients whose hearts are found to be structurally normal during autopsy (2, 3 General references An estimated 1 to 3/100,000 apparently healthy young athletes die suddenly during exercise. Males are affected up to 10 times more often than females. Basketball and football players in the... read more ).
Commotio cordis (sudden ventricular tachycardia or fibrillation after a blow to the precordium) is a risk in athletes with thin, compliant chest walls even when no cardiovascular disorder is present. The blow may involve a moderate-force projectile (eg, baseball, hockey puck, lacrosse ball) or impact with another player during a vulnerable phase of myocardial repolarization.
Other causes include inherited arrhythmia syndromes (eg, long QT syndrome Torsades de Pointes Ventricular Tachycardia Torsades de pointes ventricular tachycardia is a specific form of polymorphic ventricular tachycardia in patients with a long QT interval. It is characterized by rapid, irregular QRS complexes... read more , Brugada syndrome Brugada Syndrome Brugada syndrome is an inherited channelopathy causing an increased risk of ventricular tachycardia (VT) and ventricular fibrillation (VF) leading to syncope and sudden death. (See also Overview... read more ). Some young athletes die of aortic aneurysm rupture Overview of Aortic Aneurysms Aneurysms are abnormal dilations of arteries caused by weakening of the arterial wall. Common causes include hypertension, atherosclerosis, infection, trauma, systemic rheumatic diseases, and... read more 
(in Marfan syndrome Marfan Syndrome Marfan syndrome consists of connective tissue anomalies resulting in ocular, skeletal, and cardiovascular abnormalities (eg, dilation of ascending aorta, which can lead to aortic dissection)... read more 
).
In older athletes, sudden cardiac death is typically caused by
Occasionally, hypertrophic cardiomyopathy or valvular disease is involved.
In other conditions underlying sudden death in athletes (eg, asthma Asthma Asthma is a disease of diffuse airway inflammation caused by a variety of triggering stimuli resulting in partially or completely reversible bronchoconstriction. Symptoms and signs include dyspnea... read more , heatstroke Heatstroke Heatstroke is hyperthermia accompanied by a systemic inflammatory response causing multiple organ dysfunction that may result in death. Symptoms include temperature > 40° C and altered mental... read more , complications related to use of illicit or performance-enhancing drugs), ventricular tachycardia or fibrillation is a terminal, not a primary, event.
Symptoms and signs are those of cardiovascular collapse; diagnosis is obvious.
Immediate treatment with advanced cardiac life support is successful in < 20%; the percentage may increase as distribution of community-based, automated external defibrillators (AEDs) expands. In fact, studies have demonstrated that the presence of AEDs can increase the neurologically intact survival rates to over 80% (4 General references An estimated 1 to 3/100,000 apparently healthy young athletes die suddenly during exercise. Males are affected up to 10 times more often than females. Basketball and football players in the... read more ). For survivors, treatment is management of the underlying condition. In some cases, an implanted cardioverter-defibrillator may ultimately be required.
General references
1. Maron BJ, Haas TJ, Ahluwalia A, et al: Demographics and epidemiology of sudden deaths in young competitive athletes: From the United States National Registry. Am J Med 129:1170–1177, 2016. doi: 10.1016/j.amjmed.2016.02.031
2. Finocchiaro G, Papadakis M, Robertus JL, et al: Etiology of sudden death in sports: insights from a United Kingdom regional registry. J Am Coll Cardiol 67:2108–2115, 2016. doi: 10.1016/j.jacc.2016.02.062
3. Harmon KG, Asif IM, Klossner D, Drezner JA: Incidence of sudden cardiac death in National Collegiate Athletic Association athletes. Circulation 123:1594–1600, 2011. doi: 10.1161/CIRCULATIONAHA.110.004622
4. Johri AM, Poirier P, Dorian P, et al: Canadian Cardiovascular Society/Canadian Heart Rhythm Society joint position statement on the cardiovascular screening of competitive athletes. Can J Cardiol 35:1-11, 2019. doi: 10.1016/j.cjca.2018.10.016
Cardiovascular Screening for Sports Participation
Athletes are commonly screened to identify risk before participation in sports. In the United States, they are reevaluated every 2 years (if high school age) or every 4 years (if college age or older). In Europe, screening is repeated every 2 years regardless of age.
Screening recommendations in the US for college-age young adults—as well as for children and adolescents—include the following:
Medical, family, and drug history (including use of performance-enhancing drugs and drugs that predispose to long QT syndrome Torsades de Pointes Ventricular Tachycardia Torsades de pointes ventricular tachycardia is a specific form of polymorphic ventricular tachycardia in patients with a long QT interval. It is characterized by rapid, irregular QRS complexes... read more )
Physical examination (including blood pressure and supine and standing cardiac auscultation)
Selected testing based on findings on history and physical examination
European guidelines differ from American guidelines in that a screening electrocardiogram Electrocardiography The standard electrocardiogram (ECG) provides 12 different vector views of the heart’s electrical activity as reflected by electrical potential differences between positive and negative electrodes... read more (ECG) is recommended for all children, adolescents, and college-age athletes.
The Canadian Guidelines recommend screening in three tiers:
History/questionnaire
Physical examination
ECG only when indicated according to clinical findings
Testing follows if clinically warranted (1 Cardiovascular screening reference An estimated 1 to 3/100,000 apparently healthy young athletes die suddenly during exercise. Males are affected up to 10 times more often than females. Basketball and football players in the... read more ).
Screening for older adults (35 years or older) with risk factors may include incremental symptom-limited exercise testing Stress Testing In stress testing, the heart is monitored by electrocardiography (ECG) and often imaging studies during an induced episode of increased cardiac demand so that ischemic areas potentially at risk... read more 
, especially if they have been sedentary for a number of years.
History and examination are neither sensitive nor specific; false-negative and false-positive findings are common because prevalence of cardiac disorders in an apparently healthy population is very low. Use of screening ECG or echocardiography would improve disease detection but would produce even more false-positive diagnoses and is impractical at a population level.
Genetic testing for hypertrophic cardiomyopathy Hypertrophic Cardiomyopathy Hypertrophic cardiomyopathy is a congenital or acquired disorder characterized by marked ventricular hypertrophy with diastolic dysfunction (eg, due to valvular aortic stenosis, coarctation... read more or long QT syndrome Torsades de Pointes Ventricular Tachycardia Torsades de pointes ventricular tachycardia is a specific form of polymorphic ventricular tachycardia in patients with a long QT interval. It is characterized by rapid, irregular QRS complexes... read more is not recommended or even feasible for the screening of athletes.
Selected testing
Athletes with a family history or symptoms or signs of hypertrophic cardiomyopathy Hypertrophic Cardiomyopathy Hypertrophic cardiomyopathy is a congenital or acquired disorder characterized by marked ventricular hypertrophy with diastolic dysfunction (eg, due to valvular aortic stenosis, coarctation... read more , long QT syndrome Torsades de Pointes Ventricular Tachycardia Torsades de pointes ventricular tachycardia is a specific form of polymorphic ventricular tachycardia in patients with a long QT interval. It is characterized by rapid, irregular QRS complexes... read more , or Marfan syndrome Marfan Syndrome Marfan syndrome consists of connective tissue anomalies resulting in ocular, skeletal, and cardiovascular abnormalities (eg, dilation of ascending aorta, which can lead to aortic dissection)... read more require further evaluation. Typically evaluation includes one or both of the following ,
ECG
Echocardiography
Confirmation of any of these disorders may preclude sports participation.
If ECG reveals Mobitz type II heart block Second-degree AV block Atrioventricular (AV) block is partial or complete interruption of impulse transmission from the atria to the ventricles. The most common cause is idiopathic fibrosis and sclerosis of the conduction... read more 
, complete heart block Third-degree AV block Atrioventricular (AV) block is partial or complete interruption of impulse transmission from the atria to the ventricles. The most common cause is idiopathic fibrosis and sclerosis of the conduction... read more , true right bundle branch block, or left bundle branch block, or there is clinical or electrocardiographic evidence of supraventricular or ventricular rhythm disorders, a search for cardiac disease is required.
Athletes with presyncope or syncope can also be evaluated for anomalous coronary arteries if the above noninvasive tests are not helpful, using
Cardiac catheterization
If an enlarged aorta is detected on echocardiography (or incidentally), further assessment is needed.
Recommendations for sports participation
Athletes should be counseled against use of illicit and performance-enhancing drugs. Patients with mild or moderate valvular heart disease may participate in vigorous activity; however, patients with severe valvular heart disease, particularly of the stenotic variety, should not participate in competitive sports or high-intensity recreational sports. Patients with most structural or arrhythmogenic heart disorders (eg, hypertrophic cardiomyopathy Hypertrophic Cardiomyopathy Hypertrophic cardiomyopathy is a congenital or acquired disorder characterized by marked ventricular hypertrophy with diastolic dysfunction (eg, due to valvular aortic stenosis, coarctation... read more , coronary artery anomalies, arrhythmogenic right ventricular dysplasia) should not participate in competitive sports or high-intensity recreational sports.
Cardiovascular screening reference
1. Johri AM, Poirier P, Dorian P, et al: Canadian Cardiovascular Society/Canadian Heart Rhythm Society joint position statement on the cardiovascular screening of competitive athletes. Can J Cardiol 35:1-11, 2019. doi: 10.1016/j.cjca.2018.10.016
Key Points
Sudden cardiac death during exercise is rare and may be due to hypertrophic cardiomyopathy, but many patients have a structurally normal heart at autopsy (younger athletes) or coronary artery disease (older athletes).
Screen younger participants (children through young adults) with history and physical examination; those with abnormal findings or positive family history should have ECG and/or echocardiography.
Screen older participants with risk factors (particularly if they have been sedentary for a number of years) with history, physical examination, and usually an exercise stress test.
Recommend against participation in athletes with severe valvular disease and most structural or arrhythmogenic heart disorders (eg, hypertrophic cardiomyopathy).
More Information
The following English-language resources may be useful. Please note that THE MANUAL is not responsible for the content of these resources.
Baggish AL, Battle RW, Beaver TA, et al: Recommendations on the use of multimodality cardiovascular imaging in young adult competitive athletes: A report from the American Society of Echocardiography in collaboration with the Society of Cardiovascular Computed Tomography and the Society for Cardiovascular Magnetic Resonance. J Am Soc Echocardiogr 33 (5): 523–549, 2020. doi: 10.1016/j.echo.2020.02.009
Johri AM, Poirier P, Dorian P, et al: Canadian Cardiovascular Society/Canadian Heart Rhythm Society joint position statement on the cardiovascular screening of competitive athletes. Can J Cardiol 35:1–11, 2019. doi: 10.1016/j.cjca.2018.10.016
Martinez MW, Kim JH, Shah, AB, et al: Exercise-induced cardiovascular adaptations and approach to exercise and cardiovascular disease. JACC State-Of-The-Art Review, J Am Col Cardiol 78 (14):1454-1470, 2021.
