My wife had breast cancer approx. ten years ago and had radiation and chemotherapy. After her treatments were ending her oncologist discovered she had a very high heart rate and she was subsequently diagnosed with atrial fibrillation . Cardioversion has not been successful in restoring normal rhythm for more than a few days. Atenolol and Tykosyn were somewhat successful until recently. She had cancer in her other breast last year and underwent radiation treatments. The Tykosyn has now ceased being effective at all. What is the likelihood of the radiation having affected her heart and precipitated her atrial fibrillation?
It is very uncommon for radiation to precipitate atrial fibrillation especially if it on the right side. Scatter is very rare with the latest technology radiation. You haven't mentioned chemotherapy. Some chemotherapeutic agents like doxorubicin and trastuzumab can have an effect on heart, but the effect is mainly on heart muscle, though rhythm disturbances can also occur. But these effects are not long lasting, and she would revert to normal with time