Giordano delivered a hard, open-ice hit on Kadri in the first period of Tuesday night's 4-3 Calgary win, and Kadri was furious as he left the ice. Replays appeared to show him making a throat-slashing gesture toward Giordano after he returned to the bench.
Kadri said he let his emotions get the best of him.
"It's not something that I even remember really doing, to be honest," he said. "I was kind of in and out a little bit after that hit, just furious. It was an emotional reaction, and that's about it."
Kadri did go to the quiet room for a concussion evaluation, according to CBC Sports, which also reported that Kadri was penalized for a similar gesture at the 2010 world junior hockey championship.
Kadri could face a fine or suspension.
Flames coach Bob Hartley declined to comment on Kadri.
"I heard about the reaction, but I didn't see it, so I can't comment on this, but it was a good, old-time hit. Very simple," Hartley said. "We should teach kids to hit like this."
The Associated Press contributed to this report.