that depends on the conditioning of the client. From that perspective the approach is not any different than for every other client. I am providing a link to a 1 – 10 RPE scale https://www.google.com/search?q=rpe+vs+heart+rate+scale&espv=2&biw=1600&…. A very deconditioned client may start at 2 or 3.
Since beta blockers are usually prescribed for high blood pressure, the physician may also give you some guidance.