I am awaiting my appointment with the specialist for my hyperthyroidism so no, I have not been told it is because of the hyperthyroidism but since irregular heartbeat is a symptom of hyperthyroidism due to palpitations I would say it could be. I am 67 and have had this for a long time, not sure how it slipped through the cracks for the last ten years. I thought feeling bad was just a part of life until I found a new doctor.