From PEOPLE Magazine Click to enlarge
Kaitlin Forbes had nailed a line drive to the outfield and rounded first base in a softball game one afternoon in May 2005 when she started to feel dizzy and weak. A few seconds later, "I collapsed," she says.

And just like that the popular sophomore athlete at New York's Rhinebeck High School went into sudden cardiac arrest—the term doctors use when the heart abruptly stops beating. Within seconds her gym teacher Ron Keefe started chest compressions and sent for help; then he, along with a second gym teacher and the school nurse, placed the pads of an automated external defibrillator on Kaitlin's chest and applied an electric shock to restart her heart while they waited for paramedics to come. Arriving at the hospital, Kaitlin's parents, Linda and Darren, found Kaitlin "screaming and cursing," Linda recalls. "I thought, 'Thank God—that takes brain activity.'"

Kaitlin—who soon learned that her heart had become enlarged after a case of walking pneumonia—had a pacemaker implanted and went on with life. Then, on July 28, 2006, something shocking happened: Her best friend and softball and basketball teammate Maggie O'Malley, 17, after returning from a Broadway show, began vomiting at home. Several hours later she was dead, another victim of sudden cardiac arrest. An autopsy later revealed that her heart, like Kaitlin's, had become enlarged, most likely after an illness. "It was so hard losing her," says Kaitlin, now 19 and a sophomore at Dutchess Community College. Others in town were alarmed: "Everyone was on edge, wondering who's next?" Linda says.

Kaitlin, Linda and Maggie's still-grieving mom, Pat, decided to take action. For while sudden cardiac arrest is relatively rare in young people, it is a major killer—some 300,000 Americans die each year—and correctly administered cardiopulmonary resuscitation can mean the difference between life and death (see box). In August 2006 the three women launched the Heart Safe Club of Rhinebeck (at maggieomalley.org), getting certified to teach CPR. To date they and a dozen young friends Kaitlin recruited have trained about 300 people. Lobbying local officials and raising donations, they've also placed 25 portable defibrillators around town. "They've transformed their community by making it a safer one," says Dr. Vinay Nadkarni, a consultant to the American Heart Association.

Townspeople agree. "Students, teachers, all kinds of people are certified in CPR because of them," says Dr. John Sabia, emergency-services director at Northern Dutchess Hospital. One trainee is Kim Wright, 36, whose 70-year-old father has heart problems. "I know now," Wright says, "I can respond fast and accurately if anything happens."

Such comments are a comfort to Kaitlin, who remembers her best friend sitting out the season with her after doctors told Kaitlin she could no longer play basketball. Maggie "was there for me," Kaitlin says. And now, she adds, "I think she'd be extremely proud."