LONDON (AP) -- Fabrice Muamba's heart stopped beating on its own for 78 minutes and "in effect, he was dead in that time," Bolton's team doctor said Wednesday. The 23-year-old Bolton midfielder collapsed during an FA Cup match against Tottenham on Saturday after suffering from cardiac arrest. He was taken to London Chest Hospital where he's improving and talking to doctors after needing 15 shocks from a defibrillator. Medics tried unsuccessfully to revive Muamba for 48 minutes on Saturday before he arrived at the hospital, Bolton team doctor Jonathan Tobin said. It took another 30 minutes, after 15 shocks from a defibrillator, before the player's heart started beating again on its own. "They were working on him without his heart having a muscular beat," Tobin said. "In effect, he was dead in that time ... throughout the whole resuscitation period you are worrying. "You know the longer the resuscitation goes on the less chance there is of survival, but this is slightly different. This is a very fit 23-year-old." On Monday, the former England under-21 international started breathing independently and speaking. He likely survived because of the emergency care, which kept blood and oxygen supplied to his vital organs. Defibrillators are used to restore normal heart rhythm when there is no beat or an irregular beat. Dr Andrew Deaner, a cardiologist and Tottenham fan who was at the game Saturday, left his seat and rushed onto the field to help Muamba. "If you're going to use the term 'miraculous,' I guess it could be used here," Deaner said. "He has made a remarkable recovery so far. "Two hours after (regaining consciousness) I whispered in his ear, 'What's your name?' and he said, 'Fabrice Muamba.' I said, 'I hear you're a really good footballer' and he said, 'I try.' I had a tear in my eye." The cause of the cardiac arrest is yet to be discovered. The doctors said Muamba had undergone a routine screening for heart defects in August. He was checked again on Sunday, with the test producing a "normal" result. It is too early to say if he will return to the field. "As things stand, his life is not in danger at this time," Deaner said. "It is early days, so it is not possible to say (if he will play again)." Tobin added that the "early signs of recovery have continued." "I went to see Fabrice last night," Tobin said Wednesday. "He said, 'Hi Doc.' I asked him how he was and he said, 'Fine.'"