The condition was discovered when the 26-year-old Czech was evaluated for shortness of breath.

The nature of his condition requires him to be on blood thinners for several months and he will be unable to play hockey during this time, Avalanche team physician Dr. David Mellman said in a statement on the team's website (avalanche.nhl.com).

Fleishmann was acquired from the Washington Capitals on November 30 and has scored 21 points in 22 games for the Avalanche. He has 31 points in 45 games combined with Colorado and Washington.