An injection of steroid for bursitis caused a bout of afib for which I was hospitalized. Investigate the prednisone.
Careful with the prednisone. That can give your some symptoms if you don't manage your dosage correctly.
I hope you get your answers.
I could have written your post. It hits you like a hammer and it takes a while to figure out that you are probably not going to die from this, even though it feels like it. Continue your check ups so you know you are safe and then work on qwelling the anxiety. Self talk, slow breathing, counseling, medications like Xanax have all helped me. This can be managed -- don't give up, your life IS NOT over. Keeping you in my thoughts, hang in there.