I had hyperthyroidism 20 yrs ago they use radiation since then am on med. 6 months ago had a/f also found hyperthyroid is this possible n cause a/f?

Maybe. If your dose of thyroid replacement is too high for you, this could be a risk factor for atrial fibrillation. Have a full thyroid panel done and reviewed by a physician knowledgeable in interpreting those results. In the meantime it is important to control the atrial fibrillation and its risks. Good luck!