Sad news. He had some problems recently with an irregular heartbeat. From an AP article on Yahoo:
QUOTE
Zholtok missed games twice last year while playing with the Minnesota Wild, and suffered from dizziness and fatigue.
After leaving a game in January 2003, he was kept in a hospital overnight for observation. He was diagnosed with an irregular heartbeat, or arrhythmia. After missing seven games, he was cleared to return to the lineup.