Parker Helmerich of Tulsa, Oklahoma, was celebrated by friends and family with a drive-by birthday parade for his first birthday, which fell on Dec. 11.

The celebration at home was a long time coming for Parker, who was diagnosed with two heart conditions shortly after birth, diagnoses that came as total surprises to his parents, Faith and David Helmerich.

"I was already sending out texts [to family and friends], like, 'Everything's great. He's looking good, feeling good,'" David Helmerich recalled of the moments after his first child's birth. "And then it just came to a grinding halt, almost, and that's when the whole journey started."

The Helmerichs said Parker started having difficulty breathing around 30 minutes after he was born. Subsequent tests discovered the newborn had critical pulmonary valve stenosis, a congenital heart defect caused by a blocked pulmonary valve, according to Oklahoma Children's Hospital, where Parker was treated.

After being born "perfectly healthy," according to his parents, Parker was quickly intubated and life-flighted to Oklahoma Children's Hospital in Oklahoma City, over 100 miles from the family's home in Tulsa.

At Oklahoma Children's Hospital, the Helmerichs said they learned their son would need to undergo a cardiac catheterization and would likely need multiple subsequent open heart surgeries.

While undergoing what was expected to be a routine cath procedure, Parker suffered life-threatening complications that required 30 minutes of CPR to keep him alive. He spent the next week on an extracorporeal membrane oxygenation machine, or ECMO, which removes carbon dioxide from the blood and sends back blood with oxygen to the body, allowing the heart and lungs time to rest and heal.

The Helmerichs credit Dr. Harold Burkhart, director of the Pediatric Cardiothoracic Surgical Program at Oklahoma Children's Hospital, with saving Parker's life by performing CPR.

Burkhart also helped diagnose Parker's second heart condition, cardiomyopathy, a disease of the heart muscle that can lead to serious conditions, including heart failure.

According to Burkhart, it is an "incredibly random" occurrence to have both of Parker's conditions, cardiomyopathy and pulmonary valve stenosis, each of which are rare on their own.

"To have them both is incredibly random and just really unfortunate luck," Burkhart told "GMA." "It's nothing that happens during the pregnancy, nothing that happens with the parents. It's just that this was way he was born, and this was what he had when he was born."

After receiving Parker's cardiomyopathy diagnosis, the Helmerichs learned Parker would need a heart transplant, and fast. At the time he was placed on the transplant waiting list, Parkers was just 2 months old.

Currently, more than 103,000 adults and children are on the national transplant waiting list, according to the U.S. Health Resources and Services Administration.

"It's very difficult to find transplants, because there aren't enough donors in his weight and age group," Burkhart said of Parker's young age, adding, "It's really a race against him being able to do with his current heart and not getting sicker and be in a situation where he wouldn't survive by the time a heart finally becomes available."

For nearly eight months, the Helmerichs made Parker's hospital room at Oklahoma Children's Hospital their home, celebrating holidays and Parker's half-birthday there. With each phone call or knock on the door they received, the Helmerichs said they wondered if it would be the lifesaving heart they were waiting for.

"It was hard to go to sleep at night knowing that at any point, you could get a phone call or you could miss a phone call that was going to be the one to tell you they'd found Parker's perfect heart," Faith Helmerich said. "You didn't want to sleep through those kind of phone calls, but you also had to be realistic, and the team was very realistic with us, telling us, 'It's going to be a long wait.'"

In early October, after months of waiting, the Helmerichs said they were watching football together in Parker's room when the hospital's transplant cardiologist came in to speak with them.

"He talked to me [about football] for about five minutes and then decided to say, 'I think you're going to be a little bit busy tonight, so you might not have some time for football,'" Faith Helmerich recalled. "And that was his way of telling us that he had found Parker's perfect heart."

Less than 24 hours later, on Sunday, Oct. 6, Parker underwent a successful, lifesaving heart transplant.

"It was a big day when it happened," Burkhart said of Parker's heart transplant, the first to happen at Oklahoma Children's Hospital in nearly 30 years. "We had people that came in that weren't on call, that had no reason to be there other than they wanted to help and be part of this.

He continued, "We had essentially a double operating room with the personnel that came in to help out to make sure that it went smoothly, as well as people in the ICU after double-covering to make sure that they could focus their attention on Parker while giving attention to all the other patients."

After several weeks of recovery in the hospital, Parker was discharged from Oklahoma Children's Hospital just before Thanksgiving.

He currently takes medications twice a day and is on a temporary G-tube while he learns to eat on his own but is expected to go on to live a normal and healthy life, according to Burkhart.

Since being home, the Helmerichs said they have been able to enjoy everyday joys like giving Parker his first bath and taking him for walks in his stroller through the neighborhood.

On Christmas morning, the family said they will not take a moment for granted, especially considering where they were last holiday season.

"Last year at Christmas, he was intubated and was very sick. He'd just come off ECMO," David Helmerich said. "We had the best time we could given the circumstances, but this year it'll be a whole new deal."

For the rest of Parker's life, the Helmerichs said they'll be eternally grateful for the family of his heart donor, who gave him a second chance at life.

"I can't imagine what they were going through when they had to make the decision to have their child be an organ donor," Faith Helmerich said. "I cannot imagine, and we cannot be more grateful for the gracious gift that they gave us. They gave Parker a second chance at life, and without that gesture, he would not be here with us today."

"We will never be able to thank you enough for saving Parker's life," she added, referring to the donor's family.