Panagiotis Baltzis gets a peck on the cheek from his mother, Nadia Valerio, at a press conference at Montreal's Children Hospital on Friday. (Sidhartha Banerjee/Canadian Press)

Doctors at the Montreal Children's Hospital are calling it a miracle: a young boy will be alive to celebrate his first birthday after his heart failed.

Panagiotis Baltzis came to the hospital on Dec. 18, at the age of five months, after his parents noticed he wasn't putting on weight or growing.

When a cardiac surgeon told the parents that Panagiotis was in imminent danger, they thought the doctor was mixing them up with another family.

"He was very ill, because his heart was beating very, very quickly, in an abnormal fashion," Dr. Charles Rohlicek, a cardiologist at the hospital who was one of the first to examine the boy, said Friday.

The boy's heart was pumping at 230 beats per minute, almost twice the normal rate.

It turned out the problem was acute congestive heart failure. By the beginning of January, the boy was in worse condition. Doctors said he needed to be put on a heart and lung machine — a mass of tubes and instruments larger than a refrigerator. The family had five minutes to decide to put him on the machine.

One of the main complications of the life support system is bleeding, especially in the patient's brain.

"I remember walking in when they put him on the machine and falling on my knees," recalled the baby's father, Athanasios Baltzis, as he choked back tears.

"The first thing that went through my mind is, 'What have I done to this little baby?'"

'There's something weird'

Panagiotis couldn't remain on the life support system indefinitely, but no donor heart was available. The medical team decided to put the boy on an experimental, external mechanical device known as the Berlin Heart.

Then something unexpected happened.

"You know, we had become experts in looking at his vital signs," Baltzis said. "I went up to him [the doctor], and I said, "There's something weird. His blood pressure has two peaks. He's never had that in the last little while.' And he just ran off."

It was two heart beats: the Berlin Heart and the baby's own, starting back up again.

After two weeks, doctors noticed the boy's left ventricle was starting to squeeze normally. Again, Panagiotis's parents made a life-or-death decision to turn off the artificial heart and hope his own heart would take over.

It did. At the end of January, the boy woke up and his mother was once again able to hold him in her arms.

"It feels amazing," said his mother, Nadia Valerio.

Doctors say he is the youngest, smallest child in Canadian history to recover this way.

To have this child come back to my clinic fine and say 'mama' is, I think, a miracle," Rohlicek said.

Panagiotis remains on medication to control his heart rhythm, and he will need surgery again in a few years, but doctors expect it will be much easier to fix his arrhythmia.