Each athlete was given an electrocardiogram that was reviewed immediately by hospital pediatric cardiologist Victoria Vetter. If Vetter saw anything abnormal in the results, she would refer the child for additional testing.
Vetter said that in the last week, the hospital had treated three student athletes - in field hockey, basketball, and cross-country - for sudden cardiac arrest.
At the Upper Dublin screening, among the students to come in for testing were Shane Vereb, 14, and brother Michael, 15. Each attends Pope John Paul II High School in Royersford and plays soccer, basketball, and baseball.
Their father has more than a passing interest in screening: State Rep. Michael Vereb (R., Montgomery) cosponsored legislation to set standards for preventing sudden cardiac arrest and death in student athletes. Gov. Corbett signed the bill last June, making Pennsylvania the first state with such a law protecting student athletes.
Vereb said he wanted to put his money where his mouth was. "How can I expect other parents to be aware and screen if I don't get my own kids screened?" he asked.
Under the new law, schools and organizers of sports are encouraged to hold informational meetings at the start of playing seasons to discuss warning signs and symptoms. Parents and students, meanwhile, must sign statements that they are aware of the issue and health risks.
Websites for Pennsylvania's departments of education and health also have posted guidelines and information.
Vereb said the law will require "self-policing." It stipulates that if an athlete exhibits symptoms, the student cannot return to a sport until approved by a physician or nurse practitioner.
"If someone faints or loses consciousness," Vereb said, "just giving Gatorade is not an alternative anymore."
An eighth grader from Sandy Run Middle School, Paige Florin, 12, reached out to Simon's Fund to conduct the screening at Upper Dublin. A gymnast and dancer, Florin worked on organizing and publicizing the event as a project for her bat mitzvah.
"It can happen anywhere," Florin said. "You're running on the field, and your heart stops."
Simon's Fund was started by Phyllis and Darren Sudman of Plymouth Meeting, whose newborn son died unexpectedly in 2005. Tested afterward, Phyllis Sudman learned she had a heart abnormality, Long QT Brugada syndrome, and had probably passed it on to her son.
She said the group has funded the screening of close to 5,000 children. For every 100 children, one was found to have a potentially fatal heart condition, she said.
Vetter, the Children's Hospital cardiologist, said it was difficult to say how many student athletes die each year from sudden cardiac arrest given that there is no national registry.
She said Children's Hospital was collaborating with Simon's Fund to analyze data to determine the best way to identify those at risk. She said there was debate in the medical community over whether such mass screenings are cost-effective and might, in fact, unnecessarily heighten parents' anxiety.
Such an argument, however, did not deter Gary Scott of Upper Dublin. He brought sons Jason, 11, and Evan, 14, for screening Sunday.
"The way I look at it," Scott said, "anything you do to prevent something from happening, why not do it?"
Contact Jennifer Lin at 215-854-5659 or firstname.lastname@example.org, or on Twitter @j_linq.