(CBS News) 

Two communities are in mourning today over the sudden deaths of star athletes.

Matthew Hammerdorfer, 17, was captain of his Fort Collins, Colo. high school rugby team. During a match Saturday, he took a hit to the chest, then collapsed. an autopsy found he died due to a congenital heart defect.

Two days earlier, 16-year-old Wes Leonard collapsed and died on a Michigan basketball court, just after sinking a game-winning shot. The cause of death was determined to be an enlarged heart.

Kids in Wes Leonard’s town wanted to “be like Wes”

But how does this happen to such athletic, young people?

On “The Early Show” Monday, CBS News Medical Correspondent Dr. Jennifer Ashton explained that Matthew’s death was likely due to a congenital heart defect.

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She said Mathew’s case “was reported to be (a congenital heart defect called) Tetralogy of Fallot, which really had four different types of problems in the heart. It’s usually surgically corrected at three-to-six months. in his case, he had at least one operation to correct that. But some of the problems are never fully corrected. and with that particular congenital heart defect, it can predispose someone to electrical abnormalities, arrhythmias, abnormal heart rhythms and that likely caused his sudden cardiac death.”

“Early Show” co-anchor Chris Wragge asked, “(He was) also playing a contact sport. took a hit moments before he did collapse. Could that have been a determining factor?”

Ashton said, “We hear about these tragic cases every year, and the term for that is commotio cordis. It’s when a forceful blow to the chest strikes the heart at just this precise moment in the electrical activity of the heart that then results in cardiac standstill. Very, very rare. The coroner in his case says that they think it’s just a coincidence.”

However, with his history of heart operations, Wragge asked, should someone who has had a history of heart issues be playing contact sports?

Ashton said that’s “such a difficult question.”

She said, “The pediatric cardiologists who are responsible for clearing teenagers, boys and girls, for contact sports or competitive athletics deal with this all the time. We spoke with an expert at Montefiore Medical Center here in New York City last night who said, ‘You have to understand the social context of this. For boys, particularly, athletics is their social currency.’ So sometimes a doctor might say, ‘You’re not cleared,’ and they might go ahead and participate anyway.”

Wragge asked if heart screenings could help.

Ashton answered, “You know, to screen every child, even if they have no symptoms, is probably not feasible. But again, you want to talk to your pediatrician. Our hearts and prayers go out to the families.”

After the segment aired, Dr. Ashton addressed one portion of her interview. She pointed out, “I obviously misspoke the statistic about babies born with congenital heart defects. The true number is approximately 35,000 per year. We are proud of our accuracy in reporting medical news and are eager to correct this verbal error.”