The condition, known as hypertrophic cardiomyopathy, is one of the most common causes of sudden cardiac death - when the heart abruptly stops beating.

Storm's disease was caught on an electrocardiogram (ECG), a test of the heart's electrical signals, done by volunteer doctors who visited his school, the Waubonsie Valley High School in Aurora, Illinois, near his hometown of Naperville, as part of a community screening program offered to all students.

"There was nothing - no lightheadedness, no reason for me to believe that anything was wrong," Storm, now 17, said almost two years after that test.

He believes it may have saved his life, but the idea of screening all young athletes for heart conditions is controversial.

Italy and many other European countries already screen teen and adult athletes before they play sports, and some researchers have called for regular testing of U.S. kids and teens as well to try to prevent rare but deadly cardiac arrests. But so far, data haven't definitively shown that screening could reliably weed out only the most at-risk kids and do so at a price that wouldn't break the bank.

Based on Italian data, British researchers have calculated that close to 800 athletes like Storm would have to be kept out of sports, even given available treatment options, for every death prevented.

Not only that, but "you tell them that they're basically walking around with a ticking time bomb," said Dr. Anders Holst, from Copenhagen University Hospital in Denmark, adding that the vast majority will be scared unnecessarily.

Sudden cardiac death kills an estimated 100 to 1,000 children in the U.S. every year - an estimate that's so wide because reliable records of the deaths haven't been kept.

Because many young people with heart conditions never have symptoms, the diseases typically aren't caught until after a tragedy.

Wes Leonard was a 16-year-old high school basketball player from Fennville, Michigan, who collapsed after sinking a game-winning shot in March 2011. He was pronounced dead from sudden cardiac arrest due to dilated cardiomyopathy - when the heart becomes weakened and enlarged.

Some experts believe that if more young athletes were screened early on, a number of those deaths could be prevented.

One such proponent is Dr. Joseph Marek, a cardiologist from the Midwest Heart Foundation in Oakbrook Terrace, Illinois, who directs the screening program that tested Christopher Storm.

"We've identified a good number of kids who had life-threatening conditions who were unaware," Marek said.

QUESTIONS AND LIMITATIONS

Most doctors acknowledge that screening isn't a perfect solution. Although an ECG can run as low as $10, costs add up when millions of kids are screened.

And some results are false positives suggesting abnormalities in actually healthy hearts. In one study, 7 percent of all ECG-screened athletes needed additional testing, which can add up to $2,000 per person.

Even if more invasive tests confirm underlying problems, it's usually impossible to tell which kids would have died as a result and which would never have had any trouble, researchers said.

The evidence supporting ECG screening comes largely from Italy, which implemented a program to screen all teens and adults in organized sports in 1982. (reut.rs/JyNuPz).

After 20 to 25 years of collecting data, Dr. Gaetano Thiene from the University of Padua Medical School and his colleagues say they've shown that screening and disqualifying some athletes saved lives.

In the Veneto region the number of young athletes, male and female, dying of sudden cardiac arrest fell from one in 28,000 each year to one in 250,000, according to a 2006 study published in the Journal of the American Medical Association.

By law, Italians aren't eligible for competitive sports until their hearts are cleared by a doctor.

Thiene said about 1 percent of Italian athletes are disqualified and referred for treatment based on ECG and other test results.

WHEN NOT IN ROME

Many doctors question whether the Italian results can be applied to the U.S. population.

For one, ECG screening is less accurate in non-Caucasians, according to Dr. Charles Berul, chief of cardiology at Children's National Medical Center in Washington, D.C.

The rate of sudden cardiac death in Americans is also lower, matching that of Italians who have already passed screening tests.

The early Italian figures "might have just been a blip to begin with," said Dr. Anne Dubin, a pediatric cardiologist at Stanford University and the Children's Heart Center in Palo Alto, California.

"Or it could be that there are certain genetic rhythm problems that are inherent in Italy that we have here but not to the same extent," she said.

Other European countries have followed Italy's lead and implemented ECG screening for young athletes. A study group for the European Society of Cardiology determined the evidence warrants such tests.

Danish cardiologists broke from the European Society of Cardiology on screening, according to Holst of Copenhagen University Hospital.

He compared ECGs to prostate-specific antigen tests for prostate cancer. U.S. and European doctors intuitively thought PSA tests would save lives long before there was much evidence, he said. Yet recent reports, including one from a U.S.-wide trial, have suggested the harm of over-treatment may not be worth any small potential screening benefit.

FINDING ANSWERS

Researchers would need a "gold standard" trial - in which young athletes are randomly assigned to get ECGs or not - to determine if screening is worthwhile, Holst said.

That would require a huge number of athletes and decades of follow-up.

"It's not feasible in my view," he said.

"I'm afraid I don't have any clue as to how we are going to get a definitive answer. But until we one day might get that, I think we should just step down."

Cardiologist Dr. Robert Myerburg from the University of Miami Miller School of Medicine doesn't support waiting for persuasive data.

"I think we ought to implement (screening)," he said. "Some number of deaths can be prevented as we're going along, as we're doing the research."

Organizing a federal screening program probably isn't realistic in the United States, Myerburg said, but individual states can start screening high school athletes, he suggested.

Marek, from the Midwest Heart Foundation, said communities can sponsor in-school screening if local cardiologists are willing to volunteer to save money.

Without them, adding an ECG screening program to a traditional history and physical would cost $117 per athlete, or about $69,000 per "quality" year of life saved, according to the National Institutes of Health. The bar for cost-effectiveness is typically considered to be $50,000 per quality life-year saved.

Using a lower ECG price, Stanford researchers said screening could be cost-effective. According to their model, if the 3.7 million student-athletes deemed to be potentially at risk were screened, 183,000 would be referred for further testing. One in six of those would get results confirming a heart problem. The cost would be just under $43,000 per life-year saved.

Depending on the particular abnormality, treatment can include heart medications, surgery or exercise restrictions only.

For Christopher Storm's condition, doctors placed an implantable cardioverter defibrillator and pacemaker in his chest to keep his heartbeat regular.

He's allowed to exercise as long as his heart rate stays below 155 beats per minute. He can't run competitively but plays pick-up basketball with his friends, who let him stay on one half of the court.

"The biggest thing for me is, I'm always hearing about the athletes who collapse on the court or on the field... from the exact same thing that I have," Storm said.

The American Heart Association recommends a physical and history only for kids starting sports.

"I certainly understand the desire to want to do something, but we need to be cautious about that," said Dr. Jonathan Kaltman, a medical officer at the National Heart, Lung, and Blood Institute in Bethesda, Maryland.

"We need to be able to confidently say that we're doing more good than harm before launching a screening program that's going to affect many, many lives."

(Editing by Ivan Oransky, Prudence Crowther and Claudia Parsons)

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