05/14/2010 at 12:00 PM EDT
A year after Tristan Moulton was born, he was diagnosed with a degenerative disease called spinal muscular atrophy type 2, and his parents, Travis and Melissa, were told he wouldn't live past the age of 4.
Now 6, Tristan, who loves watching Cars
and playing hide-and-seek with his nurses, is beating those odds, but his world is tough: He's wheelchair-bound, requires 24-hour care and has already been airlifted to the hospital three times this year, due to pneumonia-related complications.
So when his parents agreed to get him a puppy in April, they hoped it would be a bright spot in his life. They took him to a Yorkshire terrier breeder 65 miles from their home in Victor, Idaho, and told him he could have any dog he wanted. He picked the runt of the 12-week-old litter, and named him Max.
"They bonded from first sight," Melissa, 33, tells PEOPLE. "I think Tristan saw himself in Max. Max was the runt, and Tristan is the smallest too."
Tristan held Max all the way home and played with him constantly over the next two days. "He was basically Tristan's best friend right away," says Melissa. Heart-Wrenching Discovery
But Melissa noticed that the puppy was breathing hard and seemed weak. Travis took Max to see his cousin, Jason Moulton, a veterinarian 90 minutes away in Blackfoot. "I listened to his heart," says Jason, "and it was rattling like an old Maytag machine."
He did an ultrasound and realized that the 1.2-lb. puppy had a congenital heart defect that leads to abnormal blood flow between the heart and lungs. "He was already in congestive heart failure," Jason says. "I told them there was nothing we could do."
Devastated, Travis and Melissa took Max home. "It broke my heart," Melissa says. "We'd gotten Max for Tristan. Tristan's a fighter, and we wanted him to experience some joy in his life rather than going through the life experience of losing someone you care about."
Even worse was the fact that Jason told them Max might have a chance if they could bring him to a Seattle veterinary cardiologist. The cost of the surgery would be upwards of $5,000, which, with medical bills for their only son, the Moultons couldn't afford.
So they gently told Tristan that Max was sick, and the boy looked at them, confused, Melissa says. "He kept saying over and over, 'Mom, take Max to the doctor. Take Max to the doctor.' He couldn't understand why we weren't helping him." Beating the Odds
Meanwhile, Adam Petersen, another vet at Jason's veterinary practice, heard about the situation and approached Jason. "This dog just wasn't going to make it without surgery," Adam says. "But if we were able to pull it off, he'd live a normal life. I told Jason we had to try."
The problem was, neither vet had ever done a complex heart procedure like the one Max needed. So Jason's sister-in-law put his practice in touch with Dr. Jacob DeLaRosa, 42, the chief of cardiac surgery at Portneuf Medical Center in Pocatello. "He told me the story," DeLaRosa says, "and I said, 'I'd love to come down and help you.' "
The next day, DeLaRosa (pictured), who had never operated on a dog before, brought a scrub nurse and his physician's assistant 25 miles up Interstate-15 to Blackfoot. It wasn't until he got there that he learned about Max's importance to Tristan. "Before, it was just saving one life," he says. "Now, it was more significant. For a little boy who's come so far in his own life, I wanted to make sure the puppy lived. The boy wasn't supposed to make it, and neither was the puppy. I wanted to change that."
Within 90 minutes of the surgery, Max was awake and barking and was expected to make a full recovery – and live the expected lifespan of a Yorkie, which could be up to 20 years.
"[I] left, feeling like the Lone Ranger," says the surgeon, who didn't charge the Moultons a dime for his services. "I'm just so proud I was able to help."
Now, Max is home, and he's by Tristan's side virtually 24 hours a day, playing a gentle game of tug of war, chasing balls or curling up by Tristan's side for a nap. "They have a little unspoken bond," mom Melissa says. "Tristan and Max, they've both beaten the odds. They're two little miracles."For more on Dr. DeLaRosa and Operation Yorkie, pick up the latest issue of PEOPLE, on newsstands now.Read more hero stories on PEOPLEPets.com:'Doggie Underground Railroad' Spares Pups from Death Soldier, Dog to Trek 7,000 Miles to Help Military Families