Dr. Lam, LAF question

For a few years now, my mom has been having symptoms of LAF. Her attacks occur on average about 1-3 times a month, and last anywhere from a few minutes to a few days. She has had multiple cardiology tests, including a 2 day nuclear stress treadmill test, ekgs, etc. She wore a heart monitor for a while and they were able to catch it on the monitor. The thing is, however, all her tests are coming back normal. Despite that, her doctor said he'll just put her on meds to regulate her heart rate. I don't think this is a good idea, if they don't know what is causing these episodes. She has hypothyroidism, which she takes hormones for, and nodules on her thyroid, which they are just watching. She says she has no anxiety, so she doesn't think they are anxiety attacks. Could her thyroid be causing this? Do you have any recommendations? Thanks.