A heart rate of 45 is too low. Do you have any symptoms, such as dizziness, lightheadedness? If you do have these symptoms, then it is strongly suggested that the slow heart rate is problematic, as it decreases heart blood output with resultant decreased blood perfusion to the brain.
One thing curious is that you have afib. In general, most patients with afib have a fast or a normal heart rate. It is very uncommon to have a heart rate of only 45. I do recommend you get a Holter test, which is the electrocardiogram that can record your heart rate and rhythm for 24 hours continuously.