He is the youngest patient ever that has gone through such an operation in Vietnam. A month after the surgery, his condition has stabilized and he could walk and play normally.

However, doctors at the Vietnam-Germany Friendship Hospital, where the operation was done, reminded the family not to let the boy engage in too much physical activity or get emotional.

The boy suffered rom cardiomyopathy, a disease of the heart muscle that makes it hard for the heart to pump blood to the rest of the body, and was at the final stage of heart failure.

The condition forced him to take in high doses of cardiotonic drug regularly. It left him weak and thin, weighing just 16 kilos (35 pounds).

Doctors diagnosed that a heart transplant was the only way to save him. Fortunately, the family of a young man who was brain dead after a traffic accident made the call to donate his heart.

With all indicators of the donor and recipient matching, the hospital decided to give transplant priority to the boy, given his young age and very critical condition. Four days after the operation, the boy was able to get up, play, recognize all people and eat and drink on his own.

"This huge favor, me and my boy would never ever forget," his mother said.

Nguyen Huu Uoc, director of the Cardiovascular and Thoracic Center at the hospital, said the country receives very few organ donations from brain-dead patients each year and the chance to find a suitable heart to transplant for a child patient was almost zero.

"And therefore when such a miracle happens and a life is saved, there is no bigger happiness for us doctors."