Sudden cardiac death and how to stop it happening

Article at a glance

Olympique Lyonnais Stadium, Lyon, 26 June 2003. In the 71st minute of the Confederation Cup semi-final between Cameroon and Colombia, the 28-year-old Cameroonian midfielder Marc-Vivien Foe collapsed. In the few minutes it took to stop play and administer treatment Foe suffered a cardiac arrest and died. An autopsy later confirmed the presence of hypertrophic obstructive cardiomyopathy (HOCM or HCM), a congenital condition that had been dormant until that evening.

The surprise caused by Foe’s death was best summed up by a fan who wrote: ‘I was and still am deeply saddened and shocked by the news of Marc’s sudden death. How could this happen to such a young, fit and strong man like Marc? How could he just fall to the ground and die?’

Although exercise in young people usually brings a host of physical and psychological benefits, for a very small minority rigorous physical activity is a serious threat to life. Most deaths in young people are caused by ‘inherited or congenital structural and functional abnormalities’ of the heart that trigger cardiac arrhythmias and result in sudden cardiac death (SCD)(1).

Barry Maron, a US physician and leading researcher on SCD, has identified the most common causes of death in young people(2), and has been central to the publication of guidelines for those with these conditions and their involvement in competitive sports(3,4) (see table 1, below).

Table 1: Top causes of sudden death in young athletes and recommendations for participation in sport
Cause of death	Incidence (% of total SCD deaths)	Recommended participation levels
Hypertrophic Cardiomyopathy (HCM) and conditions highly suggestive of HCM	33.9	Should only participate in low intensity competitive sports (eg, bowls)
Commotio cardis	19.9	None
Coronary artery anomalies	13.7	Should only participate in competitive sports six months after surgical correction provided
Myocarditis	5.2	Should be excluded from competitive sports for six months and only allowed to return provided
Ruptured aortic aneurysm	3.1	Those at risk of this condition may participate in moderate-intensity sports provided there is no family history of SCD and aortic root size is within safe limits

Hypertrophic obstructive cardiomyopathy (HOCM)

HOCM is the single largest cause of SCD in young athletes, occurring in 1 in 500 members of the general population. The condition is characterised by a marked thickening (hypertrophy) of the muscle cells (myocardium) of the heart’s left ventricle. In 90% of cases, the wall separating the chambers of the heart is also involved.

This prevents blood from leaving the left ventricle and passing normally through the aorta. The combination of outflow obstruction and the thickening results in widespread electrical instability and can lead to a marked increase in ventricular arrhythmias and sudden cardiac death.

At present 3% of adults and 6% of children with HCM die each year. In the UK, HCM was brought to the public’s attention by the death in 1992 of Daniel Yorath, a promising young footballer and son of Terry Yorath, the manager of the Welsh football team at the time. Daniel’s case highlights two important issues that can make diagnosing HCM difficult:

• A young professional footballer who had recently signed to Leeds United, Daniel was physically fit and in excellent health. Although HCM can present with symptoms of chest pain, breathlessness and loss of consciousness (which can sometimes lead to seizures), most youngsters are free from symptoms and lead normal, active lives.
• HCM can be inherited from affected parents, but in most cases there is no family history. In Daniel’s family history there was no reason to suspect HCM – indeed, Terry Yorath had been a successful professional footballer for many years.

It is clear from Daniel Yorath’s case that a thorough history is not enough to identify all cases of HCM. Further investigations usually involve a physical examination and an electrocardiogram (ECG) and cardiac echocardiography. Genetic tests can be done, but these are not widely available.

Commotio cardis

This is where sudden cardiac death is caused by a blunt, often innocent, non-penetrating blow to the chest. In a study published in 2002, 128 cases of commotio cardis had been identified among young athletes in the US over a five-year period. The study found that most victims were male (95%), aged under 18 (72%), and died immediately on the scene (82%)(5).

While most (68%) cases occurred during organised sporting events such as baseball and ice hockey matches, the authors found that the rest had taken place in playgrounds, parks or gardens as a result of innocent blows to the chest. It has been suggested that improvements in protective equipment and better access to portable defibrillators would help to prevent this condition from occurring.

Coronary artery abnormalities

Normally the heart receives its blood supply from the right and left coronary arteries. These emerge from two distinct points in the aorta, situated just above the aortic valve. Rarely, the left coronary artery can emerge from the site normally reserved for the right coronary artery. This tends to produce a pronounced kink at the origin of the artery, which during exercise leads to compression of the blood vessel between the aorta and the pulmonary vessels.

The result is a sudden drop in the blood supply to the left ventricle and the destruction of large segments of heart muscle. Although this condition can be cured with surgery, it is difficult to diagnose, often only identifiable with invasive procedures such as coronary angiography.

Myocarditis

Myocarditis is an inflammatory disease that causes destruction of the heart muscle wall, which can result in both heart failure and sudden cardiac death. Innocuous viral infections, with symptoms of flu or a common cold, are the most common cause of myocarditis. It is thought that up to 5% of those with an acute viral illness have some degree of myocarditis.

Although this tends to resolve quickly and leave no long-term effects, a small minority can either deteriorate rapidly or develop a more persistent condition (chronic active myocarditis) which may take months or even years to shake off. Both of these conditions are capable of triggering arrhythmias and causing SCD. It therefore makes sense for young athletes to avoid exercise during a viral illness and to seek medical attention when they experience cardiac symptoms such as chest pain, undue breathlessness or loss of consciousness.

Ruptured aortic aneurysm

The largest group of youngsters at risk from a ruptured aortic aneurysm are those with Marfan’s syndrome. This distinctive condition is inherited directly from one parent and is associated with abnormalities in the formation of connective tissue. The result is a number of clinical features (see box opposite) that can be identified on physical examination, and a high risk of developing abnormalities in the aorta. Provided that the dimensions of the aorta remain within normal limits, those with Marfan’s Syndrome may participate safely in a wide range of competitive sports.

Other causes of SCD

A number of other diseases and conditions can be responsible for sudden death in young athletes. Although congenital abnormalities account for most deaths, other causes such as asthma and heat stroke can also be responsible. In recent years the increasing use of stimulants such as amphetamines and cocaine has been implicated, though without conclusive evidence. In approximately 2% of SCD no definitive cardiac cause can be found(1).

How to identify those at risk

In 1982 the Italian government brought in a Medical Protection of Athletic Activities Act, which ensured that all young athletes who wished to participate in organised sports activities underwent a regular screening assessment. The assessment had three components: a comprehensive medical history, a physical examination and an electrocardiogram.

The results are impressive: while levels of HCM in the population are similar to those in the United States, reports of sudden death from HCM are unheard of in Italy(6). The American Heart Association has acknowledged this and has stated that: ‘Some form of pre-participation cardiovascular screening for high-school and collegiate athletes is justifiable and compelling, based on ethical, legal and medical grounds(7).
So what should be done? The three components in the Italian screening programme seem an appropriate place to start:

Individual history

A small number of those at risk will reveal clues that may help to identify their condition. In the US, the Sudden Arrhythmia Death Syndrome Foundation recommends a nine-point questionnaire (aimed at parents) for the first stage of SCD screening (see table 2).

Table 2: The Sudden Arrhythmia Death Syndrome Foundation Questionnaire
	Yes	No
Has your child fainted or passed out during exercise, emotion or startle?
Has your child fainted or passed out after exercise?
Has your child had extreme fatigue associated with exercise (different from other children)?
Has your child ever had unusual or extreme shortness of breathe during exercise?
Has your child ever had discomfort, pain or pressure in his chest during exercise?
Has your child ever been diagnosed with an unexplained seizure disorder?
Are there any family members who had an unexpected, unexplained death before the age of 50 (including SIDS, car accident, drowning)?
Are there any family members who died of heart problems before the age of 50?
Are there any family members who have unexplained fainting or seizures?

Physical examination

This should be completed by a trained physician and should focus primarily on the cardiovascular system.

Electrocardiogram (ECG)

The 12-lead ECG is abnormal in 95% of those with HCM and often shows irregularities in other fatal coronary abnormalities. Unfortunately in a number of highly trained young athletes, abnormal recordings are common, such as slow heart beat or some forms of heart block which in older sedentary people would indicate a problem. Nevertheless, any abnormal readings should then be followed up.

The next step in the diagnostic process is echocardiography. The echocardiogram provides a highly detailed view of structural abnormalities in the heart and is considered to be the ‘gold standard’ test for identifying HCM, aortic root disease and changes in left ventricle dysfunction which characterise severe cases of myocarditis.

Conclusion

It has proved incredibly difficult to adopt a standardised screening programme for sudden cardiac death. With the exception of Italy, no state-wide programme exists in western Europe to identify those at risk. Even in the United States, where the impetus for screening is greatest, only 17 states have adopted a strategy deemed ‘adequate’ by the American Heart Association.

In the US alone, four million youngsters participate in regular competitive exercise. This means that as many as 8,000 individuals may be living with HCM and putting their lives at risk every time they step on to a basketball court or a football pitch. Shouldn’t something better be done?

Jeremy Windsor is an anaesthetist at the University College London Hospital and research assistant at the Institute of Human Health and Performance at University College London. As a member of the Xtreme Medical Expedition, he summited Mt Everest in May 2007

References

1. Sudden death in young athletes. New Eng J Med 2003; 349:1064-75
2. Sudden death in young competitive athletes: clinical, demographic and pathological profiles 1996; JAMA 276:199-204
3. Profile of preparticipation cardiovascular screening for high school athletes 1998; JAMA 279:1817-9
4. Risk of competitive sport in young athletes with heart disease. Heart 2003; 89:710-4
5. Clinical profile and spectrum of commotion cardis. JAMA 2002; 287:1142-6
6. Evidence for efficacy of the Italian national pre-participation screening programme for identification of hypertrophic cardiomyopathy in competitive athletes. European Heart Journal 2006; 27:2196-2200
7. Insights into methods for distinguishing athlete’s heart from structural heart disease with particular emphasis on hypertrophic cardiomyopathy. Circulation; 91:1596-1601