Screening for risk of sudden cardiac death

People affected by this are young and outwardly healthy, so screening has an essential role. By Dr Jonathan Holliday

Each year in the UK, about 400 outwardly healthy young people die from undiagnosed heart conditions. Not the most common cause of death, but when you consider that more than half of those deaths are preventable if only the diagnosis is known, and that the age is so young (average age 17 years), it is obvious why it is of such importance to society, as well as to parents.

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 1 in 500, of whom at least 50 per cent are familial. It has an autosomal dominant inheritance.

Patients may be asymptomatic or have such mild symptoms as not to 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.

CASE STUDIES

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 with a friend when he suddenly felt unwell. He sat down at the foot of a tree and there he died. Subsequent post mortem examination showed a hypertrophied left ventricle.

The trouble is that these boys look perfectly fit and normal. This is a common finding, even for paediatricians. In one study, 13 out of 357 children were found to have cardiac anomalies on the basis of echocardiography and Doppler.3 The paediatrician reported no cardiac abnormalities from his examination of all 357, while the paediatric cardiologist detected abnormal cardiac findings in seven of the 13 on physical examination.

My second case happened in February 2005. Aged not quite 18, this young man had arrived from Australia as a gap student to work in a prep school, but within days, he was dead. He was playing for the local rugby fourth XV 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 him up. It is equally likely his registration medical examination would not.

Consider cardiomyopathy
Syncope must be taken seriously in children and should always 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 and all of the common symptoms that can come from it.

The important thing is to rule out other (most commonly ischaemic) causes of 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 rises sharply once persistent heart failure sets in. The thrust of treatment is gaining symptom control with diuretics, early use of ACE inhibitors, beta-blockers and digoxin. 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 has only recently been recognised. In this condition, there is a fibrofatty replacement of the myocardium. At least 50 per cent are familial and it has autosomal dominant inheritance. 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, although an implantable defibrillator may be required.

Finally, there is restrictive cardiomyopathy, the least common of the four, defined by the rigidity of the ventricular walls. It has been suggested that this may be a form of HCM. Patients with this condition usually 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, the genetic problem results in dysfunction of the ion channels through the myocardial cell wall. The wrong amounts of charged ions are in the wrong place, resulting in electrical dysfunction and an increased risk of ventricular arrhythmia.

These conditions are rare, with even the most common, long QT syndrome (LQTS) having a prevalence of 1 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), too little sodium passes to the cell. Although not all individual cases have a defective gene isolated, this is increasingly so. The genetic picture is clouded by variable penetration and variable position of the defective gene, but it is gradually being worked out.

Other more structural causes of sudden cardiac death include valvular disease, anomalous coronary arteries, connective tissue disorders (for example, Marfan syndrome and Ehler-Danlos syndrome) and even the common mitral valve prolapse.

Screening
So, who should we screen and how should we do it? The evidence is all based on a huge body of work from Italy.1 Since 1971, Italian law has required every athlete to undergo an annual clinical evaluation to obtain approval for their participation in competitive sports.

In the Veneto region, researchers at the University of Padua prospectively 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 (+/-SD) age, 23+/-7). 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+/-5 years.

Screening can save lives, but at what cost? 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.

In 2004, the Lausanne Recommendations for pre-participation cardiovascular screening were published under the umbrella of the IOC Medical Commission. This recommends a two-step screening process. Step one consists of a personal history questionnaire, a family history questionnaire, a physical examination and (after the onset of puberty) an ECG.

Step two is for those cases with positive personal or family history, or positive physical or ECG findings, and comprises further evaluation by an age-appropriate cardiac specialist with investigation as required. This may include trans-thoracic echocardiography, maximal exercise testing and 24-hour ECG monitoring. The right to privacy of the athlete is stressed.

In February 2005, a consensus statement of the Study Group of Sport Cardiology of the European Society of Cardiology was published.2 This statement recommended clearance of all young athletes involved in organised sports programmes, on the basis of two principles: first, the proven efficacy of systematic screening by 12-lead ECG (in addition to history and physical examination) to identify hypertrophic cardiomyopathy - the leading cause of sports-related sudden death - and to prevent athletic field fatalities. The second principle was the potential screening ability in detecting other lethal cardiovascular diseases presenting with ECG abnormalities.

The NSF for CHD was published in March 2005. Chapter eight sets out markers of good practice in sudden cardiac death which require GPs to refer patients with relevant symptoms or a positive family history to a specialist.

Solutions
Various screening solutions are available around the country, but there is so far no countrywide policy. Routine cardiac screening remains the preserve of elite athletes, national sports associations and professional sports clubs. We are now seeing cardiologists offering to come into schools to screen pupils by echocardiography. Private companies are now offering the full service of pre-screening questionnaire, ECG and echocardiography. But such screening is expensive in time (testing alone takes about 30 minutes) and money.

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

This is the system employed at our school and we have used Cardiac Risk in the Young (CRY) to deliver it for the past four years. CRY is a national charity, one of whose aims is to promote a national screening programme for cardiac disease in young people. CRY produces an information leaflet and the application and consent forms. We mail it to parents with one of the standard mailings at the end of a term and set a deadline for applications at the start of the next term.

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. Some may need 24-hour ECG monitoring and we have so far arranged for those few to be assessed at the local cardiology unit.

Typically, we screen 120 pupils a year at £35 each. Screening is voluntary and the bill is picked up by the pupil. Of the 120, we expect five or so to require categorisation with echocardiography or 24-hour ECG, but so far, we have only found one who required interventional therapy (ablation of aberrant pathway in a case of Wolfe-Parkinson-White syndrome).

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

References
1. Corrado D, Basso C, Schiavon M, Thiene G. Screening for hyper-trophic cardiomyopathy in young athletes. NEJM 1998;339:364-9.
2. Corrado D, Pelliccia A, Bjornstad HH et al. Cardiovascular pre-participation screening of young competitive athletes for prevention of sudden death: proposal for a common European protocol. Consensus Statement of the Study Group of Sport Cardiology of the Working Group of Cardiac Rehabilitation and Exercise Physiology and the Working Group of Myocardial and Pericardial Diseases of the European Society of Cardiology. Eur Heart J 2005;26(5):516-24.
3. Steinberger J, Moller JH, Berry JM, Sinaiko AR. Echocardiographic diagnosis of heart disease in apparently healthy adolescents. Paediatrics 2000;105:815-18.

Further resources
CRY (Cardiac Risk in the Young)
The Cardiomyopathy Association
CHD NSF -
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