My Cardiologist Has Told Me That Bystolic Does Not Affect

My cardiologist has told me that Bystolic does not affect the heart rate. But with what I have read now, it does affect heart rate, and a slow heart rate is a listed side effect. Also, my previous cardiologist told me that "You don't do well with beta blockers!" Thank you. My heart rate is usually in the 50's, and my current cardiologist thinks it is o.k., but it makes me nervous. (I am 79 years old.)