Coyotes general manager Don Maloney says the 23-year-old MacLean received CPR on Monday night at the rink in Owen Sound, Ontario. He was taken to a hospital by ambulance, then transported by air ambulance to Knight University Hospital in London, Ontario where he was admitted to cardiac ICU.
Maloney says no other information was available Tuesday.
"Our thoughts and prayers are with Brett and his family," Maloney said in a statement. "We request that everyone please respect their privacy at this time. We will provide an update on Brett's status when information is available."
MacLean was a Phoenix second-round draft pick in 2007. He played 13 games for the Coyotes in the 2010-11 season.
He was claimed off waivers by Winnipeg last Oct. 5, then waived by the Jets 23 days later. Phoenix reclaimed MacLean and assigned him to AHL Portland.
Information from The Associated Press was used in this report.