It's massive, hugely traumatic surgery, taking the patient past what was considered the point of death a century ago, bringing them back alive, and all with the aid of some of the most powerful drugs in modern medicine's arsenal.
And if your heart is needing transplantation in the first place, you'll be running far below optimal for blood O2 and a dozen other things.
It'd be more surprising if it didn't result in significant change.
> if your heart is needing transplantation in the first place, you'll be running far below optimal for blood O2 and a dozen other things.
that's not obvious on the face of it from a mechanical standpoint. I'd you're sick enough to need one, wouldn't we just give you a mechanical temporary replacement, and keep that one going as high as possible instead as low as possible?