When Bowie 16-year-old Miles Davis returned to classes at the Nora School in Silver Spring earlier this school year, other students didn't know how to treat him. He'd just had open-heart surgery to implant a left ventricular assist device, a mechanical pump to help his failing heart, and he wore a battery pack around his waist to keep it operating.

They worried about jostling the batteries or tube leading to his heart, and generally "walked on eggshells" around him, said Head of School Dave Mullen.

Now, five months after the surgery, students ask to change or hold his batteries. And they call him "Iron Man," a reference to the machinery in his chest and the superhero-sized grace with which he's dealt with his circumstances.

"In situations like these, people will often say, ‘So-and-so matured so much, so quickly,'" said Dr. George Ruiz, who specializes in structural heart problems and treated Miles at Children's National Medical Center and Washington Hospital Center in Washington, D.C. "Miles was already incredibly mature. But he's also easygoing and happy. He hasn't been pounded into the ground by life. Perspective is so much a part of how illness manifests itself, and Miles met this challenge with resilience, defiance and optimism."

Last March, Miles, who played on his school's soccer and basketball teams, suddenly couldn't walk up the stairs without sitting to rest. Craytonia Davis, a pediatrician, and Janice Davis, a social worker, took their son to Anne Arundel Medical Center with what they thought was pneumonia.

There, they learned Miles' heart was failing for an unknown reason and that he'd need to transfer to the cardiac intensive care unit at Children's National Medical Center.

"That just totally took me aback," Janice Davis said. "I was not ready to be there."

Even more frustrating was that doctors couldn't say what went wrong.

Miles' heart may have become inflamed as his body fought off a virus, Ruiz said. A host of other factors, from genetic issues to electrolyte imbalances, can also cause a young, otherwise healthy teen's heart to fail, Ruiz said.

Without immediate action, Miles' prognosis was "dismal," Ruiz said.

By summer, after several rounds of hospitalizations and medications, doctors started talking about starting Miles on an investigational drug to rebuild his heart muscle and implanting a left ventricular assist device to let his heart rest and regain strength.

Ruiz said the strength of Miles' optimism became increasingly apparent as treatment options narrowed. Ruiz and Miles, who had been on a low-sodium diet for months, had a running joke about a post-surgery trip to Ben's Chili Bowl in Washington, D.C.

"In the midst of all this craziness, he was like, ‘Hey, if I get through this, can we go to Ben's Chili Bowl?'" Ruiz said. "I was like, ‘Look, man, you can't go to Ben's Chili Bowl. As your doctor, I can't tell you that's OK.'"

Miles is cheerful and talkative, with a soft, sweet voice and an easy smile. He speaks about the past year with the calm optimism that Ruiz said carried him through his treatment.

"The whole time, it was sort of like, ‘OK, I'm sick. I need a heart device. Life goes on,'" Miles said. "It was scary at times, but I always knew I was going to get better."

Doctors implanted the device on Aug. 17. Weeks later, Miles was attending class at the Nora School via Web cam using a laptop teachers named the "Miles Macintosh" and making plans to go back to school later in the fall.

The transition back to life as a normal teen wasn't free of complications. Miles must carry the battery pack everywhere he goes, and those around him must be trained in how to respond if the device has problems. He can't drive the car he got for his 16th birthday because its airbags could damage the device. He can no longer play basketball or soccer, he can't run for any reason and he has to eat a low-fat, low-sodium diet.

But he can walk to classes, attend field trips and generally live like the average teen.

On a recent night, he took a trip to Ben's Chili Bowl with his parents and Ruiz.

"For me, going to Ben's Chili Bowl was one of my proudest moments, not as much as a doctor, but as a person," Ruiz said. "Sometimes, the smallest victories leave us with the greatest joy. Who would ever think a hot dog could symbolize so much?"