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1. Sudden Cardiac Death in Athletes

Sudden cardiac death (SCD) is a very rare event but particularly tragic affecting apparently healthy young or early middle-aged people. Sudden cardiac death occurs in approximately one per 100,000 young athletes per year, generally in matches or training, but also occasionally at rest.^[1]

Common categories of sudden cardiac death causes are:

• Cardiomyopathies
• Conduction disorders
• Coronary artery disease
• Commotio cordis
• Unknown causes, thought to possibly be related most often to Myocarditis associated with viral illness

Cardiomyopathies and conduction diseases are responsible for the majority of sudden cardiac death in young athletes (< 30 years old), whereas Coronary artery disease (often latent in a relatively young person) increases in risk with age and is by far the most common cause of sudden cardiac death in an athlete >35 years old. Commotio cordis is less common but caused by an external force rather than an intrinsic abnormality of the heart.

2. Prevention of Sudden Cardiac Death in Athletes

2.1. Classification of Sports for Risk of Sudden Cardiac Death

Sports have been classified into varying risks for Sudden Cardiac Death for competitive athletes.^[2][3] Sports with high static and dynamic forces are those that present the greatest risk, bearing in mind that for individual athletes playing in these sports the risks are still very small. Rowing, cycling and basketball are amongst the sports with the highest annual risk.^[4] Football (soccer) provides the highest number of young athletes who suffer cardiac arrest, being a medium risk sport that is played extensively worldwide. The risk is higher in male athletes than female athletes.

2.2. Screening of Athletes to Prevent Sudden Cardiac Death

Screening of athletes to prevent SCD is a controversial area. Generally medical screening is considered to be potentially valuable for conditions or diseases that are relatively common and not useful for conditions that are rare, due to the likely high number of false positives. SCD is rare and hence screening necessarily has a high rate of false positives (that is, athletes flagged as being potentially unsafe to participate in high level sport but who would not die if they did continue to play sport). Nevertheless, because of the fear of SCD and occupational requirement to train and compete at extremely high intensity in professional and elite sport, screening is established as a standard of care in many countries of the world.^[5] The country with the most established program of screening for cardiac disease in athletes is Italy, which requires this to be done by law. Over many decades the rate of SCD in Italy has reduced, probably due to nationwide screening.^[6] Some experts question whether the rate may have been reduced through other means, and whether the disqualification of many young people from playing vigorous sport annually is worth it.^[7]

International guidelines have been agreed to regarding what constitutes a normal and abnormal athletic ECG when screening asymptomatic athletes.^[8][9]

In Europe, the UK and Australia,^[10] the standard of care is generally to include an ECG as part of the standard screening program. Whilst ECGs are done for many athletes in the USA, the standard of care is more likely to be an annual history & physical examination, with an ECG only performed if any item of concern with the clinical presentation.^[11]

A major charity in the UK is Cardiac Risk in the Young (CRY) which performs regular screenings.

2.3. Athletic Event Management to Respond to Cardiac Arrest

Whilst screening may be attractive as a means to prevent cardiac arrest, there is more evidence that prevention of actual death relates more to survival from a cardiac arrest when it occurs.^[12] The vast majority of non-hospital cardiac arrests in the community do not survive, because of fatal delays (of only minutes) from arrest to cardiopulmonary resuscitation and cardioversion using an Automated external defibrillator.

A wall-mounted Automated External Defibrillator (AED) at a sporting venue. https://handwiki.org/wiki/index.php?curid=1859405

In theory, cardiac arrest at a sporting event whilst very rare can be predicted and hence the survival rate from arrest should be higher. Not all stadia and athletic fields have AEDs present, particularly at amateur level. And not all events have well-trained event staff (doctors, paramedics and staff qualified in basic life support). Finally, even with AEDs and staff present, because of the rarity of cardiac arrest in the community especially in young people, event staff may not be well or recently trained to respond, or may not be concentrating at the time of an arrest.

Event planning is therefore a key component of Sports Cardiology, even though event planning would not normally be a concern of a medical specialty. Making sure that there are sufficiently trained medical, paramedical and other trained staff or volunteers at sporting events, ready availability of AEDs or ambulances or both, and that those qualified people are ready to respond to an arrest, probably leads to a greater lowering of the rates of sudden cardiac death in sport than any other measure. Hence, having an excellent understanding of the parameters of safe event planning is a core subject in Sports Cardiology.

3. Management of Known Heart Disease in Athletes

3.1. Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) or HOCM (O = obstructive) is considered the most common cause of sudden cardiac death in young athletes that may be preventable. However the difficulty is that it overlaps with the more Athlete Heart syndrome and vast majority of discovered cases are mild, making it unclear about whether it is safe to continue playing intense sport.

3.2. Arrhythmogenic Right Ventricular Cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is less common than HCM but usually more clearly progressive, associated with intense activity and usually has more clear indication to avoid highly intense sporting activities. It is more common in certain genetic backgrounds. Much of the reduction in deaths in Italy since the advent of nationwide screening has been thought to be due to ARVC reduction.

3.3. Long QT Syndrome

Long QT syndrome is a familial condition that is uncommon, but is a known source of sudden death in young people. It can cause cardiac arrest during athletic activity but also when doing other activities that raise heart rate.

3.4. Brugada Syndrome

Brugada syndrome is a familial condition that is also very uncommon, and also a known source of sudden death in young people. Many of the deaths occur when inactive and it is less commonly a cause of sudden death playing sport.

3.5. Atrial Fibrillation in Athletes

Atrial fibrillation (AF) is more common in the inactive, elderly population than the inactive young population. There is a reverse J-shaped curve, however, in that elite athletes doing very arduous sport have a higher rate of AF than moderately active people. Whereas the AF that occurs in the inactive elderly population is known to be associated with increase risk of stroke, it is unknown whether athletic AF increases the risk of sudden death or stroke. AF in athletes can be treated with a minimally-invasive procedure known as ablation.

3.6. Wolff–Parkinson–White Syndrome

Wolff–Parkinson–White syndrome (WPW) syndrome is a known cause of arrhythmia in young people. It causes supraventricular tachycardia during exercise. Most of the time this causes cessation of exercise when the SVT occurs. It can lead to cardiac arrest but generally does not. It can also be successfully treated by a minimally-invasive procedure known as ablation.

3.7. Implantable Cardioverter-Defibrillators in Athletes

An Implantable cardioverter-defibrillators (ICD device) can be used in an athlete who has either had a previous cardiac arrest or is known to be at very high risk for cardiac arrest to trigger an internal shock to cardiovert the heart in the event of a fatal rhythm occurring.