The second patient to receive a pioneering artificial heart has left hospital and is living a “completely normal life”, the French heart transplant specialist behind the mechanical organ said on Friday.

Sprightly academic Professor Alain Carpentier, 81, told Le Parisien newspaper that the 68-year-old unnamed patient’s recovery after his operation last summer was “a miracle”.

“He told us that he went out for lunch without any assistance 70 kilometres from his home in Nantes [western France],” Carpentier said. “There couldn’t be a more beautiful demonstration of someone leading a completely normal life.”

The patient, who was discharged from hospital on January 2, was given his new heart in August 2014. The device, which is essentially a mechanical pump with an internal control system to regulate the blood flow, relies on batteries which are worn by the patient.

The first person to receive the heart, 76-year-old Claude Danu, died in March 2014, 74 days after his operation.

The second recipient of the artificial heart, made by French company Carmat, is doing much better, and Carpentier praised the progress in a man “who walks much better than I do”.

“Three weeks ago I spent an afternoon with him at the Nantes Hospital [where he received the treatment] and it was a staggering experience,” he said. “Patients with his illness normally have swollen legs and are unable to even hold a conversation.”

“But in five months since his operation, he is no longer even aware of his new heart which is now an integral part of him,” he added. “I asked him if he wanted to go out for a walk and he jumped on his exercise bike to show off his fitness. I even had to tell him to slow down a bit! “

Carpentier, who has been working for the last 35 years on his artificial heart, said he had often thought he would “never see the say”.

“I am completely bowled over,” he said.

Carmat's share price jumped 8.6 percent on Friday on news of the patient's remarkable recovery.

France24