What Causes Tiredness Inspite Of Being On Toprol?

Hi I am presently taking Toprol XL and have been since 2005. I have 4 cardiac stents due to blockages in my arteries discovered in 2005. I take Toprol XL 25mg once a day along with Plavix 75, Aspirin 80, Simasvastin 40, and Lisinispril 40.. I also take Advair to prevent asthma. I have been feeling really tired this past year and my cardiologist has thought about taking me off the Toprol, but wants to do the stress test first. I no longer do the nuclear test due to concerns about the radiation dose. I would like to know what can I expect if I do get off the Toprol.