After Pettersson scored in the first round for Vancouver, Reimer got his right pad on J.T. Miller's shot in the second and made the save against Bo Horvat in the third to end the game.
"Horvat came in, and he's obviously a highly skilled player," Reimer said. "I just tried to wait him out and not give him too much net. Luckily enough, I was able to get a glove on it."
The Canucks are 14-3-1 in their past 18 games.
"I thought our team was outstanding tonight," Vancouver coach Travis Green said. "I thought it was a pretty intense game, probably fitting that it went into overtime and then a shootout."