Chances for both sides abounded in the third period.
The Russians have now won a medal at the world junior hockey championship for seven consecutive years.
Jonathan Dahlen had Sweden's lone goal while goalie Felix Sandstrom made 24 saves.
Guryanov jumped on the loose puck and put it between Sandstrom's legs just 33 seconds into the extra session.
The Swedes, who outshot Russia 39-26, were the faster and more dangerous team for much of the game.
Sweden’s Markus Naslund set the all-time record with 13 goals in 1993, while Russia’s Pavel Bure had 12 in 1991.