@chickenfarmer I can't help with expertise, but I can provide my interaction between hypothyroidism and Afib. In December 2024 I was being prepped for Cataract surgery on my right eye and was found to be in Afib. No symptoms that I could feel. 2 weeks before that I had Cataract surgery on my left eye, no Afib. Blood work then showed that my TSH levels were low. All my previous blood work for years and years showed no TSH problems. Levothyroxine was prescribed and my TSH levels are in the normal range. I had a cardioversion done in February 2025 which put me back in sinus rhythm and then a pulse field ablation in May 2025. Since then, no Afib episodes. I have autoimmune system problems, so I requested that I be tested for Hashimoto's Syndrome which is known to cause hypothyroidism. The test was positive for Hashimoto's. There is no cure for Hashimoto's all you can do his work on the impact, which is hypothyroidism. Since starting on Levothyroxine, I have never varied the dosage up or down. Did the Hashimoto's trigger hypothyroidism which in turn triggered the heart to go into Afib? Know way of really knowing. All I know is that my TSH, T4, T3 and T2 levels are in the normal range, and I have had no Afib episodes since February of 2025.