Has the Doc checked your dad's TSH levels?
I had horrible,,, and I mean horrible AFIB for years until the Hospital finally checked my TSH levels and put me on Levothyroxine for my thyroid. Now I have no AFIB at all. Haven't had an attack in over two years because of the thyroid medication. My attacks were so bad you could see my chest moving and I would damn near pass out. And the chest pain was terrible not to mention how dangerous it is for your heart and can cause strokes.
Now I can drink coffee and even smoke sativa's again with no problems.
I had no idea how much control your thyroid has over your heart and organs.
My TSH levels was at 8.9
Now they stay around 1.8 to 2.4.
For someone with AFIB even 4.5 can cause problems. Believe it or not,,some Cardiologist have no clue about AFIB and your thyroid.