The Bolton Wanderers doctor Jonathan Tobin says footballer Fabrice Muamba was in effect dead for 78 minutes following his on-field collapse.
Doctors say it is too early to predict whether he will play football again.
Muamba suffered a cardiac arrest in Wanderers' FA Cup tie against Tottenham Hotspur at White Hart Lane on Sunday.
Dr Tobin says Muamba was given two defibrillator shocks on the pitch, one in the players' tunnel and a further 13 in the ambulance on the way to hospital but none worked.
He says Muamba's heart stopped beating for more than an hour and the doctors at White Hart Lane and the London Chest Hospital saved his life.