I had the same surgery and was prescribed Metropolol after surgery which gave me depression and low energy. I told the cardiologist to change me back to Atenolol that I was taking before surgery. I regained my energy and started feeling happy the next day. The cardiologist told me that metropolol is a lypolitic agent that crosses blood-brain barrier and this is why I was feeling so down. Ask your cardiologist to try a different medication.I didn't like metoprolol it affected my sex life. It did however make me very calm during family "discussions" They prescribed it after surgery. I asked my cardio if I still needed it and since I was on lisinopril for blood pressure he took me off. No problems.