I was just told that I have a-fib.  I had a normal EKG a year ago, but also had treatment for breast cancer that included doxarubacin and cytoxin, then taxol, followed by radiation.  The cancer was bilateral, and I had lumpectomies.  Could the a-fib be a result of the cancer treatment?
Yes Treatment for cancer can cause atrial fibrillation. Radiation and medication for cancer chemotherapy like Duxoroubicin, Taxa and to less extent other medications are cardio toxic, such that they affect the Heart muscle causing inflammation.  When this inflammation subsides there is some residual fibrosis in between the heart muscle. This fibrosis acts as substrate for rhythm disturbances, common among them is a trial fibrillation.  A 2 d echocardiography more precise Cardiac MRI is suggested to know extent of any damage to the heart. In many causes though there is no decrease in pumping of the heart (mechanical) , still arrhythmia may happen sue to electrical disturbances.  Let me know if any clarification needed.  Regards Chat Doctor. 