Screening young people for risk of sudden cardiac death

Screening has an essential role in sudden cardiac death, says Dr Jonathan Holliday.

Each year in the UK, about 400 outwardly healthy young people die from undiagnosed heart conditions. More than half of those deaths would be preventable if the diagnosis was known.

The most common causes are the cardiomyopathies, in which there is an intrinsic, structural problem of heart muscle. The hypertrophic form (HCM) is thought to have a prevalence of about one in 500, of which is at least 50 per cent is familial. It has an autosomal dominant inheritance.

Patients may be asymptomatic or have such mild symptoms that they do not seek assistance. Others may have symptoms of fatigue or shortness of breath, while the more severely affected may complain of palpitations, or even angina or syncope.

Consider cardiomyopathy
Syncope in children should prompt the consideration of cardiomyopathy. Sudden death may occur in 4-6 per cent of children with HCM.

Diagnosis is by echocardiography, but the ECG is rarely normal. Symptom control is with beta-blockers and calcium-channel blockers, but in the high-risk patient, an implantable defibrillator is required.

Dilated cardiomyopathy (DCM), as its name suggests, results in a dilated ventricle with poor contractility. This leads to heart failure.

It is important to rule out the more common causes of heart failure, particularly ischaemic heart failure.

Overall, 35 per cent of cases of DCM are familial, with the rest attributed to alcohol, viral myocarditis or toxic chemicals.

Early diagnosis is important because mortality increases sharply once persistent heart failure sets in. Heart failure and the occasional resultant AF can increase the risk of emboli, and anticoagulation may be required.

Again, there are going to be some in whom the risk of sudden cardiac death is so great that an implantable defibrillator is required.

Arrhythmogenic right ventricular cardiomyopathy is a fibrofatty replacement of the myocardium. It has autosomal dominant inheritance and at least 50 per cent are familial. ECG is usually abnormal and echocardiography shows a dilated, poorly contractile ventricle. The risk of death comes from ventricular tachyarrhythmia and therapy is aimed at treating that, again an implantable defibrillator may be required.

Finally, there is restrictive cardiomyopathy, the least common, defined by the rigidity of the ventricular walls. It has been suggested that this may be a form of HCM. Patients with this condition present with symptoms of heart failure, but a substantial proportion present with embolic symptoms. Arrhythmias are rare in this group.

In the ion channelopathies, there are no structural abnormalities to find in death. Here, a genetic problem results in dysfunction of the ion channels through the myocardial cell wall and an increased risk of ventricular arrhythmia.

Other conditions
These conditions are rare, with even the most common, long QT syndrome (LQTS), having a prevalence of one in 5,000. In LQTS, too little potassium passes to the cell.

In Brugada syndrome (a condition more common in people with genetic origins in South East Asia), the problem of too little sodium passing to the cell also occurs.

More structural causes of sudden cardiac death include valvular disease, anomalous coronary arteries, connective tissue disorders (such as Marfan syndrome) and even the common mitral valve prolapse.

Screening
The evidence for screening young people is based on a body of work from Italy. Since 1971, Italian law has required every athlete to undergo an annual clinical evaluation to obtain approval for their participation in competitive sports.

Researchers at the University of Padua studied sudden deaths among athletes and non-athletes (aged 35 years or less) from 1979 to 1996. The causes of sudden death in both populations were compared and the pathological findings in the athletes were related to their clinical histories and ECGs.

Cardiovascular reasons for disqualification from participation in sports were investigated and follow-up performed on a consecutive series of 35,735 young athletes who underwent pre-participation screening during the same period. Of the 269 sudden deaths in young people, 49 occurred in competitive athletes (44 male, five female; mean age 23). The most common causes of sudden death in athletes were arrhythmogenic right ventricular cardiomyopathy (22.4 per cent), coronary atherosclerosis (18.4 per cent) and anomalous origin of a coronary artery (12.2 per cent).

HCM caused only one sudden death among the athletes (2 per cent), but caused 16 sudden deaths in the non-athletes (7.3 per cent). HCM was detected in 22 athletes (0.07 per cent) at pre-participation screening and accounted for 3.5 per cent of the cardiovascular reasons for disqualification. None of the disqualified athletes with HCM died during a mean follow-up period of 8.2 years.

In 1996, the American Heart Association consensus panel recommendations stated that pre-participation cardiovascular screening for young athletes was justifiable on ethical, medical and legal grounds.

The 2004 Lausanne Recommendations for pre-participation cardiovascular screening were published and supported a two-step screening process.

In February 2005, the Study Group of Sport Cardiology of the European Society of Cardiology published a consensus statement which recommended the clearance of all young athletes involved in organised sports programmes.

Solutions
Various screening solutions are available but routine cardiac screening remains the preserve of elite athletes, and national sports associations.

Cardiologists have started offering to come into schools to screen pupils by echocardiography. Private companies now offer the full service of a pre-screening questionnaire, ECG and echocardiography. However screening is expensive in time and money.

The best hope for mass screening rests with questionnaires (to pick up high-risk individuals who have a history of faintness or syncope with exercise or a positive family history) and ECG.

This is the system employed at the school where I work. It has been delivered there by the national charity Cardiac Risk in the Young (CRY) for the past four years. CRY produces an information leaflet, application and consent form. We mail it to parents and set a deadline for applications.

All participants undergo high-quality ECG testing and the ECGs are then assessed, with any doubtful cases called back for echocardiography at no additional cost. Screening is voluntary and the bill is picked up by the parent.

So far we have only found one student who required interventional therapy.

Dr Holliday is a GP in Eton, Berkshire, and a member of Cardiac Risk in the Young (CRY)

This article was originally published in MIMS Cardiovascular. To register to receive copies go to www.hayreg.co.uk/specials

Case study sudden cardiac death
I work in a school of 1,300 boys aged 13-18 years. Sadly, I have seen two cases of sudden cardiac death.

The first boy was 14. He had recently started at the school and was being treated for asthma. When he complained of a tight chest and shortness of breath with exercise, I thought this was his asthma. Physical examination was normal and there was no family history. On the day he died, he had gone out to play rugby as normal. He was walking back to the changing rooms when he suddenly felt unwell. He died before reaching the hospital. Subsequent post-mortem examination showed a hypertrophied left ventricle.

My second case happened in 2005. Aged 17, this young man was playing for the local rugby team when he collapsed. A couple of players in his team were paramedics and they tried to resuscitate him, initially with some success, but he was dead by the time he arrived at the hospital. He had no previous symptoms of any kind. The post mortem declared that he died of an arrhythmia and that he had congenitally small coronary arteries.

It is likely that screening would have picked this up. It is equally likely his registration medical examination would not.

References

Corrado D, Basso C, Schiavon M, Thiene et al. Screening for hypertrophic cardiomyopathy in young athletes. N Engl J Med 1998; 339: 364-9.

Corrado D, Pelliccia A, Bjornstad H H et al. Cardiovascular pre-participation screening of young competitive athletes for prevention of sudden death: proposal for a common European protocol. Eur Heart J 2005; 26: 516-24.

Resources

CRY - Cardiac risk in the young - www.c-r-y.org.uk.

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