Event monitor-fast heart rate

I am a 34 year old female. I had my first child 10 months ago and since have been diagnosed with PPD, Hashimoto's Disease (first hyper thyroid now hypo thyroid). When my thyroid problems started I noticed fast heartrate over 100 resting. I was hyper thyroid at that time. I was put on a beta blocker. When my thyroid went to normal then to hypo my heart rate went back to normal. I was then put on Synthroid to treat my hypo thyroid. It gave me horrible anxiety, panic attacks, and fast heart rate so bad I drove myself to the ER. They did tests and sent me hOme with a referral to a cardiologist. That was about 3 weeks ago. I stopped the Synthroid. I had a stress test and a sonogram of my heart before and after stress test and my results are normal. I am now wearing an event mOnitor till the beginning of August. It goes off automatically when I walk/jog. I have also recorded a few times when I would get anxious with a fast heart rate. My question is what will they find on the event monitor that didn't come up during the stress test? Is anyone else being treated for thyroid problems and heart problems? What could be causing fast heartrate all of the sudden? It never gets over 125 and doesn't last more than an hour or so.

[Jerry_NJ]

To one of your questions, the wearable heart monitor will record what may have been missed during the short time you were monitored for the stress test.  For some reason our hearts seem to "know" it is being watched (EKG, Stethoscope, other short term listen) and behaves itself better than when it can't be caught.  The monitor with catch anything that happens over a long period of time, it should get everything that is normal and not normal.