The Bolton Wanderers midfielder collapsed and almost died during an FA Cup match against Tottenham in March, with the player being clinically dead for 78 minutes.
But thanks to the efforts of the medical staff attending him - including a consultant cardiologist who happened to be at White Hart Lane - Muamba pulled through, and has been slowly getting better. The 24-year-old has been building up his fitness levels recently by jogging and playing tennis, and had hoped to return to the game.
His hopes of playing again have been dealt a heavy blow, however, with Belgium-based cardiologist Pedro Brugada telling him at a recent consultation that he needs another operation.
"Fabrice wants to resume his career but the number one priority has got to be his health," a source told the Daily Mirror. "That is all those closest to him are concerned about."
The former England U21 star already has a pacemaker installed in his chest, and said a few weeks ago that he was, "improving slowly but surely.
"I am just enjoying life and travelling. It is a great privilege to be able to live with the assistance of a respiratory machine or something like that. It is fantastic," he said recently in an interview with Spanish newspaper AS.
"I am making small steps every day. I am still being medicated and we will see what happens. I have to co-ordinate with my doctor and see what he says but I'll never say never."