Hi everyone, I am new to this site. In march of 2013 I was fitted with a pacemaker due to 3 sec heart stoppages. Immediately after I was diagnosed with a-fib. My natural hr is around 50. I am tired, weak and very short of breath. My cardiologist set the lower hr at 50. My question is would I not feel better if she was to set the lower limit to say 60bpm, or is this sort of thing not done.