Update – Yep, the Lich King has over 100M health in 25-man heroic mode.
Professor Putricide (Heroic) World First Kill by Paragon
Paragon just defeated Professor Putricide in heroic mode and gets another world first kill in Icecrown Citadel. They killed all the end-wing bosses and the lich king is next on the list. Congratulations to them.
However, killing the Lich King in heroic mode might be harder than it looks. According to the russian guild Экзорсус (EU-Ревущий фьорд) the Lich King heroic mode has been buffed in 10-man instances and his health was buffed from 22.5M to 29.5M, making the fight look a lot harder now. It wouldn't be surprising if the buff also affected the 25-man version of the encounter.