An estimated 1 to 3 per 100,000 apparently healthy young athletes develop an abrupt-onset heart rhythm abnormality Overview of Abnormal Heart Rhythms Abnormal heart rhythms (arrhythmias) are sequences of heartbeats that are irregular, too fast, too slow, or conducted via an abnormal electrical pathway through the heart. Heart disorders are... read more 
and die suddenly during exercise. Males are affected up to 10 times more often than females. Basketball and football players in the United States and soccer players in Europe may be at highest risk.
Causes of Sudden Cardiac Death in Athletes
Generally, the causes of sudden death during exercise are very different in young athletes than in older athletes. However, in all athletes, asthma Asthma Asthma is a condition in which the airways narrow—usually reversibly—in response to certain stimuli. Coughing, wheezing, and shortness of breath that occur in response to specific triggers are... read more 
, heatstroke Heatstroke Heatstroke is a life-threatening condition that results in very high body temperature and malfunction of many organ systems, which may be fatal. (See also Overview of Heat Disorders.) Heatstroke... read more , and the use of performance-enhancing or recreational drugs may help trigger death due to sudden abnormal heart rhythms.
Young athletes
In young athletes, most sudden cardiac death occurs in people who have no abnormality of the heart structure. When there is an abnormality of heart structure, the most common one is abnormal thickening of the heart muscle (hypertrophic cardiomyopathy Hypertrophic Cardiomyopathy Hypertrophic cardiomyopathy includes a group of heart disorders in which the walls of the ventricles (the two lower chambers of the heart) thicken (hypertrophy) and become stiff. Most cases... read more 
).
Other heart disorders that are present from birth, such as long QT syndrome Torsades de Pointes Ventricular Tachycardia Torsades de pointes ventricular tachycardia is a specific type of ventricular tachycardia that occurs in people who have a particular disorder of the heart's electrical activity called a long... read more or Brugada syndrome Cardiac Channelopathies Cardiac channelopathies are abnormalities in heart cell proteins that control heart electrical activity and thus can cause heart rhythm disturbances. (See also Overview of Abnormal Heart Rhythms... read more , cause abnormal heart rhythms and may also cause sudden death in young athletes.
Less commonly, undetected heart enlargement (dilated cardiomyopathy Dilated Cardiomyopathy Dilated cardiomyopathy is a group of heart muscle disorders in which the ventricles (the two lower chambers of the heart) enlarge (dilate) but are not able to pump enough blood for the body’s... read more 
) may be present in a young person who has no symptoms, and the person may die suddenly during or after vigorous exercise. Inflammation of the heart muscle, usually due to a viral infection (myocarditis Myocarditis Myocarditis is inflammation of the muscle tissue of the heart (myocardium) that causes tissue death. Myocarditis may be caused by many disorders, including infection, toxins and drugs that affect... read more ), can cause heart enlargement and abnormal rhythms, such as ventricular tachycardia Ventricular Tachycardia Ventricular tachycardia is a heart rhythm that originates in the ventricles (lower chambers of the heart) and produces a heart rate of at least 120 beats per minute (the normal heart rate is... read more 
, leading to sudden cardiac death.
Abnormalities of the coronary arteries (coronary artery disease Overview of Coronary Artery Disease (CAD) Coronary artery disease is a condition in which the blood supply to the heart muscle is partially or completely blocked. The heart muscle needs a constant supply of oxygen-rich blood. The coronary... read more 
), especially when one of the arteries takes an abnormal path through, rather than on top of, the heart muscle, may also cause sudden death in athletes when the compression cuts off blood flow to the heart during exercise.
Young athletes with inherited conditions, such as Marfan syndrome, Marfan Syndrome Marfan syndrome is a rare hereditary disorder of connective tissue, resulting in abnormalities of the eyes, bones, heart, blood vessels, lungs, and central nervous system. This syndrome is caused... read more 
that cause weakness in the wall of the aorta (the major artery leading from the heart) may develop a tear (aortic dissection Aortic Dissection An aortic dissection is an often fatal disorder in which the inner layer (lining) of the aortic wall tears and separates from the middle layer of the aortic wall. Most aortic dissections occur... read more ) or a bulge (aortic aneurysm Overview of Aortic Aneurysms and Aortic Dissection The aorta, which is about 1 inch (2.5 centimeters) in diameter, is the largest artery of the body. It receives oxygen-rich blood from the left ventricle of the heart and distributes it to all... read more ) that can rupture and lead to massive bleeding and sudden death.
Rarely, young, thin athletes may also have sudden heart rhythm disturbances if they experience a strong blow to the area directly over the heart (commotio cordis Commotio cordis Blunt injury to the heart is a blow to the chest that bruises the heart muscle, tears (ruptures) the heart's walls, or damages a heart valve. People may feel that their heart is pounding or... read more ) even when they have no heart disorder. The blow often involves a fast-moving projectile such as a baseball, hockey puck, or lacrosse ball or impact with another player.
Older athletes
In older athletes, the most common cause is
Occasionally, hypertrophic cardiomyopathy Hypertrophic Cardiomyopathy Hypertrophic cardiomyopathy includes a group of heart disorders in which the walls of the ventricles (the two lower chambers of the heart) thicken (hypertrophy) and become stiff. Most cases... read more or heart valve disease Overview of Heart Valve Disorders Heart valves regulate the flow of blood through the heart's four chambers—two small, round upper chambers (atria) and two larger, cone-shaped lower chambers (ventricles). Each ventricle has... read more 
is a cause.
Symptoms of Sudden Cardiac Death in Athletes
Some athletes have warning signs such as fainting or shortness of breath. Often, however, athletes do not recognize or report these symptoms, and the first sign is that the person suddenly stops breathing and collapses.
Screening for Risk of Sudden Cardiac Death in Athletes
Screening before exercise participation
People are commonly screened by their doctor before starting an exercise program Starting an Exercise Program People should consult their doctor before beginning competitive sports or an exercise program. Doctors ask about known medical disorders in the person and family members and about symptoms the... read more . Doctors screen people who have medical disorders and also those who do not think they have any medical disorders. People without known medical disorders should typically be checked because some serious disorders do not cause problems until people exercise. People in the United States 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 no matter what the athlete's age.
Doctors always ask people questions and do a physical examination, but they do testing only when the person's age and reported symptoms are cause for concern. Questions focus on three areas:
Symptoms such as chest pain or discomfort, fainting or near-fainting, fatigue, and difficulty breathing, particularly when these symptoms occur during vigorous exercise
Family history, particularly any history of family members who fainted or died during exercise, or who died suddenly before about age 50
Use of certain prescription, performance enhancing, and illegal drugs
The physical examination focuses on listening to the heart with a stethoscope for heart murmurs that indicate a possible heart disorder and measuring blood pressure with the person lying down and again while the person is standing.
For younger people, doctors typically do not do any tests unless something abnormal is identified in the person's history or is found during the physical examination. Routine use of electrocardiography (ECG) screening of young athletes is not considered practical in the United States. However, if findings suggest a heart problem, doctors typically do ECG Electrocardiography Electrocardiography (ECG) is a quick, simple, painless procedure in which the heart’s electrical impulses are amplified and recorded. This record, the electrocardiogram (also known as an ECG)... read more 
, echocardiography Echocardiography and Other Ultrasound Procedures Ultrasonography uses high-frequency (ultrasound) waves bounced off internal structures to produce a moving image. It uses no x-rays. Ultrasonography of the heart (echocardiography) is one of... read more 
, or both.
For people over age 35, doctors may also do ECG and exercise stress testing Stress Testing Stressing the heart (by exercise or by use of stimulant drugs to make the heart beat faster and more forcibly) can help identify coronary artery disease. In coronary artery disease, blood flow... read more 
before approving vigorous exercise.
If a heart disorder is found, the person may need to stop participating in competitive sports and undergo further testing. Some people with severe heart disease, such as hypertrophic cardiomyopathy Hypertrophic Cardiomyopathy Hypertrophic cardiomyopathy includes a group of heart disorders in which the walls of the ventricles (the two lower chambers of the heart) thicken (hypertrophy) and become stiff. Most cases... read more , should not participate in competitive sports. However, most people with heart disease may participate in noncompetitive sports. Increased activity is directly related to better health outcomes such as a decrease in "bad" cholesterol levels (low-density lipoproteins), prevention of high blood pressure, and reduction of body fat. Regular exercise is routinely included in care plans for people with most forms of heart disease (cardiac rehabilitation Rehabilitation for Heart Disorders Cardiac rehabilitation is useful for some people who have had a recent heart attack, have heart failure or coronary artery disease that has recently developed or suddenly worsened, or had heart... read more ).
Treatment of Sudden Cardiac Death in Athletes
Resuscitation
If people stop breathing and collapse, immediate treatment is with
Use of an automated external defibrillator if available
Resuscitation is continued in the emergency department. If the person survives, doctors treat the condition that caused the abnormal rhythm. Sometimes doctors place an implantable cardioverter-defibrillator Implantable Cardioverter-Defibrillator (ICD) There are many causes of abnormal heart rhythms (arrhythmias). Some arrhythmias are harmless and do not need treatment. Sometimes arrhythmias stop on their own or with changes in lifestyle,... read more , which continually monitors the person's heart rhythm and delivers a shock to return the rhythm to normal if needed.
Automated External Defibrillator: Jump-Starting the Heart
An automated external defibrillator (AED) is a device that can detect and correct a type of abnormal heart rhythm called ventricular fibrillation. Ventricular fibrillation causes cardiac arrest. AEDs are easy to use. The American Red Cross and other organizations provide training sessions on the use of AEDs. Most training sessions take only a few hours; but it is possible to use an AED even if you have never participated in a training course. Different AEDs have somewhat different instructions for use. The instructions are written on the AED, and most modern AEDs also use voice prompts to direct the user in each step. AEDs are available in many public gathering places, such as stadiums, airports, and concert halls. People who are told by their doctor that they are likely to develop ventricular fibrillation but who do not have an implanted defibrillator may want to purchase an AED for home use by family members, who should be trained in its use.  |
More Information
The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
Nick of Time Foundation: This organization works to increase survival of sudden cardiac arrest with awareness, "hands-only" CPR training, advocacy for having defibrillators in all public places, and access to screening for young athletes.
