You are not permitted to download, save or email this image. Visit image gallery to purchase the image.
Despite making 10 changes to the side defeated by Ireland in Dublin, Wales looked slick and cohesive in the opening stages and ended up going over for five tries.
Hadleigh Parkes and North scored within the first seven minutes but the early Welsh onslaught was checked by a smart finish from Matteo Minozzi, one of the few bright sparks in another disappointing Italian campaign.
With the visitors beginning to grow into the contest, Wales did not help themselves with Liam Williams sin-binned at the end of the first half and Gareth Davies early in the second.
In between, Cory Hill added the hosts' third try before North forced his way over for his second in the 66th minute.
Justin Tipuric added a fifth and Mattia Bellini went over for a late consolation in the closing stages.
A late yellow card for Tommaso Benvenuti helped Wales seal a victory that lifts them above England, France and Scotland into second with one round of matches to play.
Defeat, though, only extended Italy's winless run to 16 Six Nations games.
A game featuring the two lowest-scoring sides in this year's championship saw a remarkable start with three tries coming within a breathless, end-to-end opening 10 minutes.
First, centre Parkes burst through the Italian defence to touch down from close range before his midfield partner, Owen Watkin, picked off a stray Maxime Mbanda pass and surged clear before feeding the towering winger North to stroll over.
Any thoughts of a Wales procession quickly evaporated, however, when the lively fullback Minozzi skipped clear of two tackles before finishing smartly in the corner.
After the frantic opening, some semblance of calm ensued and after Gareth Anscombe kicked a penalty for a 17-7 lead, Williams received a yellow card for dangerous contact on Minozzi on the stroke of halftime.
Wales' numerical disadvantage had little effect with Hill flying over for his first international try in the 42nd minute.
With the clock running down on Williams' 10-minute punishment, Davies saw yellow for knocking the ball down but, despite playing almost a quarter of the game with a one-man advantage, the Italians were unable to cut the deficit.
Restored to 15, North then collected an offload from replacement Rhys Patchell to seal the bonus point before the ever-impressive Tipuric crossed in the corner to seal victory in the closing stages.