The Flames piled pucks on the Canucks net early, building up a 7-1 edge in shots while creating a half-dozen scoring chances, perhaps the best coming from Mikael Backlund who skated right down the middle and took a pass from Mangiapane and then snapped a wrister that Holtby swallowed up.
Calgary went to the powerplay at 5:15 when Vancouver rookie Nils Hoglander was called for hooking Rasmus Andersson as the Flames blueliner tried to skate the puck out from behind his net, spinning him into Markstrom.
Right off the draw, Tkachuk tipped a Johnny Gaudreau shot from the half-boards that Holtby managed to get a piece of and send wide.
Later in the advantage, Horvat opted to hold and fire the puck on a short-handed 2-on-1, Markstrom sending the puck up and into the net with his blocker.
Leivo got the visitors on the board at 9:30 with his sixth goal of the year.
He created a turnover as Jonah Gadjovich tried to clear the puck with a lunge right near the Vancouver blueline, then settled down a bouncing puck and flicked a lovely backhand up-and-over the outstetched right pad of Holtby.
Ruzicka was sent off for interference at 12:50 giving the Canucks their first man-up but the Flames were able to kill it off despite some good looks by the homeside.
The Flames kept up the offensive pressure in the second, Holtby coming across to rob Dillon Dube with a pad save on what looked like a sure-thing for the young forward early on.
Leivo then drove around Olli Juolevi and threw the puck out front on a Flames rush, the biscuit going off the skate of Lucic and into the net at 5:48, Michael Stone picking up the other helper. It was Lucic's 10th goal of the season.
Connor Mackey - playing in his fourth game of the season - was tagged for a boarding call on Matthew Highmore, then fought Gadjovich who came after him and got the instigator call.
Tkachuk made it 3-0 when he skated into the Canucks end and fired a shot that missed the net and bounced off the end boards and right back out to him, and he made no mistake on the second chance to put it home.
Not long after, Backlund's shot beat Holtby but not the post, however the forward was high-sticked by Boeser on the play putting Calgary on another man advantage, this time for four minutes.
They finished the middle stanza with another powerplay but were 0-4 after 40 minutes of play.
The Canucks scored their second of the night on the powerplay in the third, Tyler Graovac beating Markstrom at 2:30, before Boeser added another PP marker at 7:47.
Then it was J.T. Miller scoring short-handed at 11:28 to pull his side within one.
Not long after, Horvat was sprung on a partial breakaway but Markstrom made the stop.
Boeser then tied it up with 2:02 to go.
Dube drove in with less than minute left, Holtby making the first save but then Dube got the rebound and drove behind the net for a wraparound that the Vancouver 'tender managed to get his toe on to keep it knotted at five and force OT.
THEY SAID IT:
Adam Ruzicka on making his NHL debut:
"It was a great feeling being out there with the boys. First of all, we got the win, which is really positive. It was a sureal feeling to get the first one and I hope there are many more to come."
Darryl Sutter on Ruzicka's game:
"Adam, I thought early was a little tentative. Then he won a couple faceoffs, got banging around a little bit and then got better."
On how the game played out:
"It was just special teams. Our penalty killing wasn't very good in the third, and our powerplay wasn't very good all night. Wasn't a whole lot going on out there."