Hi,
what do you mean with "Physiotherapy". What are you going to treat?
If you are referring to general mobilisations: It's cardiac surgery with post surgical cardiac complications ... you will have to ask the Anaesthetist or Cardiologist.
They will have set up a post surgical rehab plan including guidelines for boundaries of blood pressure/ heart rate/ oxygen saturation etc. variations. That's my view.
Cheers,
Fyzzio