I honestly think that this ending was perfect. Higuchi changing his profession from heart surgeon to emergency medicine was a sign of growth to me. Him moving on from his past/mistakes and taking on a different route seems a lot more realistic than him suddenly having to perform a heart surgery on his lover and saving his life - considering he seems to still be dealing and coping with his past failure.
It's just my personal insight and opinion IF it were to go the ANGSTY way as I had a feeling it was possible for it to be that way. Though it wasn't, so the ending works too.
It honestly would've been a better ending if it went the predictable way, which is Higuchi having end up performing Tenju's surgery and overcoming his fear and they build each other's trust and love from then on. I would be lying if I say I'm satisfied with the ending, buttt as long as they're happy I'm fine with it I guess