Is your cardiologist aware of the rate?
How high of a dosage are you taking of the beta blocker
? You may want to ask your doctor's permission to lower your dosage by 1/4 or 1/2 to see if your heart rate rebounds. If you feel better on the lower dosage, then...problem solved.
I take Metoprolol. When I began taking it, my HR dropped, as did my already low BP. I have a tendency to faint sometimes, and on the BB my tendency increased 10 fold. So, I dropped back to 1/2 pill and voila...