I did not take a beta blocker until my aortic valve replacement/pacemaker implant almost 6 years ago. Immediately after surgery, since I had a propensity toward afib, they gave me timed-release Metoprolol, 100 mg/day. It controlled my heart rate and rhythm, but I felt like I was towing around a sled full of boulders all day. I tolerated it for a while (about 3 months?), then had a talk with my cardio about it. He agreed to reduce my daily dosage to 50 mg, as a test. I felt better, but still not back to "normal." My heart rate continued to behave. After about another 3 months, I mentioned it again, and since all was well, he agreed to try reducing my dosage to 25 mg/day. That seemed to work fine for heart rate/rhythm control, and I felt even more "normal." I've stayed at 25 mg/day for over 5 years now, and have only occasional issues.