The defenseman missed the past five games because of personal reasons.
"The Vegas Golden Knights wholeheartedly support Alex and the Pietrangelos and ask that the family's privacy be respected at this time," the Golden Knights said in a statement.
Pietrangelo, who last played Nov. 26, has 21 points (three goals, 18 assists) in 23 games this season. He leads Vegas in time on ice per game (23:29) and assists, and is tied with forwards Mark Stone and Jonathan Marchessault for third in points.
"That's one of those ones that we're working with Alex and supporting him and when he's ready, he'll come back," Golden Knights coach Bruce Cassidy said Wednesday.
Vegas (19-8-1), which leads the Pacific Division, lost 5-1 to the New York Rangers on Wednesday.
