AMANDA BELGER was a healthy and fit 21-year-old mother of two young children when, a year ago, she collapsed and died. There were, apparently, no warning symptoms.

Amanda’s name became added to the list of those who have died from what has become known as “sudden death syndrome” – a list that includes four to six under the age of 35 a week.

Sandra Armstrong, Amanda’s mother, says: “The suddenness of the death was shocking and bewildering.”

One initial suggestion was that Amanda had undetected epilepsy and her death was due to a swift and fatal seizure. Sandra and her second husband, Godfrey Armstrong, a musician, thought that explanation unlikely.

Last November, six months after Amanda’s death, a coroner concluded that she had had a sudden and fatal cardiac arrhythmia caused by a disruption in the heart’s wiring. The specific abnormality is known as “long QT syndrome” and is inherited.

Subsequent tests this year by Professor William McKenna, a cardiologist at St George’s Hospital, south London, and a leading researcher in sudden death syndrome, suggest that Amanda’s children – Liam, three, and Ella, now 15 months – have signs of the same defect. The peak age for such deaths is between 12 and 35.

The children will now be assessed regularly and, when old enough, may be treated with drugs such as beta-blockers or may be fitted with a defibrillator, the size of a matchbox, which can be implanted under the skin to kickstart the heart at the first sign of trouble.

In the past, such cruelly sudden deaths in young people were accepted as rare and inexplicable acts of fate. Now, thanks largely to the charity Cardiac Risk in the Young (CRY), we know that such deaths are more common than once thought. The charity, supported by Prof McKenna and by sportsmen including Ian Botham and Sir Stephen Redgrave, campaigns for more awareness among the public and GPs of the risks and potential symptoms.

The charity advocates a national screening programme for heart abnormalities in young people and research into their prevalence and genetic histories. Despite the growing awareness, many of the 200 or more unexplained sudden deaths a year are recorded by coroners as due to natural causes. CRY says: “Until coroners are required to refer the hearts in such cases to specialists, we will never know the true figures.”

Sudden death syndrome is the umbrella term used for about 10 cardiac conditions affecting heart muscles and the electrical activity of the heart. Some are less common than others. Many who die suddenly are physically very active; some are professional athletes or talented sporting teenagers. A few years ago, the death of Daniel Yorath, 15, an aspiring footballer who had just signed for Leeds, captured the headlines when he died playing in the garden.

Sport itself does not lead to heart trouble, says Alison Cox, who founded CRY with her husband, Mark Cox, the leading British tennis player in the Seventies. “But pushing the body to physical extremes could exacerbate an undetected abnormality.” One specific defect known as “hypertrophic cardiomyopathy” is the most common form and is said to account for about half the sudden deaths in athletes.

When the Coxes’ son Steven, an outstanding junior tennis player, went on a sports scholarship to an American college they learnt – just in time – about the risk. A few years earlier, a student at the college died suddenly and, fearing litigation, the college introduced screening for all young people on intensive sports programmes. Steven was found to have early signs of a potentially dangerous abnormality. Now 27, he has given up his tennis career.

Dr Sanjay Sharma, a consultant cardiologist at Lewisham University Hospital, explains that in some young athletes, intensive training is associated with structural changes in the heart that may simulate a suspicious heart problem.

He says: “Giving reassurance that there is no risk in such cases is important, but it should be done only by a cardiologist experienced in assessing young athletes.” Already, sports clubs are more alert to the legal and medical risks, and many insist on heart tests for young athletes.

Sandra Armstrong wished she had known of the long QT syndrome. “My daughter’s death was waiting to happen. There have been at least two unexplained sudden deaths in Amanda’s father’s family.” She says subsequent tests show that several older members have signs of the syndrome, though they remain healthy.

Detection of potential risk through an electrocardiogram, a recording of the heart’s electrical activity, is painless and relatively simple. And, at £35, it is affordable, says CRY, which would like to see such testing introduced more widely on the NHS.

Doctors look at the ECG recording for unusual warning “blips” and if necessary carry out further tests. These include an echocardiogram, an ultrasound check on the movement of heart valves.

Sudden deaths are shattering. The Armstrongs are now bringing up Amanda’s children. Nothing, says Sandra, can bring back her “lovely, good-looking young daughter”, but she is determined to speak up for others who may be at risk. “We have to detect these abnormalities. Even if children are not tested, there are symptoms such as fainting attacks, dizziness or palpitations that could herald trouble. We need sharper focus by GPs on symptoms they often dismiss as transient, and advice on how to avoid trouble if you are at risk.

“Sudden loud noise is known to be a possible trigger of sudden death in those with long QT syndrome. It is possible that a door blown shut downstairs might have accounted for Amanda’s death. Most people I know had never heard of these disorders until Amanda died.”

Spotting heart defects early.

This month, the hearts of up to 1,000 students, aged 14 to 16, in state schools in the Western Isles, are to be screened. The aim is to discover more about the prevalence and potential risk of unsuspected heart defects.

Ethical approval for giving the children ECG tests has been given, and soon parents will receive letters explaining the research in detail and asking for their consent and cooperation. The research is expected to take several years, with advice and treatment for children considered at risk. CRY is supporting the study, which will also consider the psychological impact of ECG testing.

The study, led by Dr Sharma, sets a precedent. So far, screening in schools has only happened at independent schools. CRY recommends that all young elite athletes should consider screening. In some countries, such as Italy, it is mandatory for those participating in sport. ECG tests for athletes are available at the CRY Centre of Sports Physiology at the British Olympic Medical Centre in north London. Experience with elite athletes, says Dr Sharma, suggests that about four per cent of those tested need further investigation.

What is certain, says Dr Sharma, is that the families of anyone who has died of sudden death syndrome should have an ECG check. “We can classify the risk, treat if necessary and advise on potential symptoms and how to stay out of trouble.”

Symptoms include excessive breathlessness, chest pain, palpitations, fainting fits, blackouts and dizziness while exercising. Those with a problem are usually advised to avoid situations that might lead to sudden and potentially life-threatening “adrenalin surges”.

Sudden deaths have been reported following a swimmer jumping into cold water or sudden loud noises, such as an alarm clock or doctor’s bleep – this may have triggered the death of one young doctor who apparently died suddenly in his sleep. · CRY: 01737 363222; http://www.c-r-y.org.uk