Though the hit did not connect, you can see that Trouba clearly leads with his elbow in an attempt to knock down Armia. I get maybe he didn't purposefully think about throwing the elbow and that it could have been a natural reaction to being further away from Armia than he thought, but by rule an attempted elbow like that should result in a two-minute minor.
This is a dirty hit. I get he is trying to make a play, but he did not glide into Athanasiou one bit, and he even extended his arms upward to inflict more bodily harm. This should have been a two-minute charging penalty at the least.