What Causes Dizziness And Cough After A Bypass Surgery?

I had 4 bypasses in 08, they put me on atenol, lisopril, and simvastatin. After about 3 months of doing fine, I started having same symptoms as before surgery. Mainly getting dizzy when getting up, and exerting myself, even coughing hard, I will get dizzy. I stopped taking the atenol on my own because my blood pressure was good with out it. Also, I cut the lisopril down to 5mg from 20 on my own. I drink more water. I have had a noticable ringing of my left ear for over a year and now it is very loud, and I am loosing hearing in it. I was wondering if the medications could be causing some of these symtoms and or the lack of medications.