The consultant who worked on Fabrice said he was effectively dead for an hour. On Beeb news tonight. The fact he's responding to questions and recognises his family is nothing short of a miracle. The consultant also said that short of your heart stopping in hospital, a cup final is about the second best place to do it, since the place was knee deep in medics.
Edited to add: There was a consultant cardiologist watching the match. He spotted they were giving Muamba cpr so he asked his brother if he thought he should go down. The upshot was they spoke to a steward they knew to get him on the pitch and the cardiologist basically saved Muamba's life and then accompanied him to hospital. He said he spoke to him briefly and said "I hear you're a footballer" and Muamba said "I try", whereupon the cardiologist started blubbing.