Hello, 
As long as you are not having any symptoms, such as 
lightheadedness, dizziness, or weakness, there would be no reason to be concerned about 
sinus bradycardia of above 50. 
You may want to get an EKG just to make sure that there is no 
heart block or signs of 
heart disease causing the bradycardia, but in most cases, you will have sinus bradycardia, which above the rate of 50 would be fairly common and not associated with any health problems or risks. 
Actually, if you have low thyroid, the medication used to treat that may help bring your 
heart rate up over time.
 If you do start to notice symptoms as I mentioned above, you will likely need to see a heart rhythm doctor and a pacemaker may need to be considered.
Hope I have answered your query. Let me know if I can assist you further.
Take care
Regards,
Dr Aaron Branch, General & Family Physician