Maloney was given oxygen by medical crews and was taken into an ambulance at the arena.
Earlier in the evening his boxer Price was beaten in a shock result in front of his home Liverpool crowd.
"Frank was talking to a friend outside the press conference, held his head suddenly and went down on his knees," said American promoter Don Majeski who saw the incident in The Telegraph.
"He was then put on his back and his legs were placed upwards over a chair. He was on the floor around five minutes.
"The police then cleared the onlookers from the area and an ambulance was called."
Maloney has undergone heart surgery in the past, and collapsed once before, when one of his fighters - Darren Sutherland - committed suicide in 2010.