Hi I do not know about any research about this. however, when I had been on T3 a little while ( blood tests showed I needed it) my hypertension ( high) became Hypotension, ( low ) some times dangerously low, I had to stop one of my cardiac pills because of this. Still on the low side.
On the subject mentioned of AF. This is not normally diagnosed with an ECG as intermittent for many years and lots of people never have it permanently, more serious if so. Best and most reliable way is taking the Heart Rate(pulse) manually, both when you think you have AF and when you do not. The heart rate swings, very noticeably. I did enquire extensively , recently about machine doing this. None of them are considered correct by medics and in fact the companies who make them,( I phoned,) say that only the BP part of them is tested I am in permanent AF and indeed have found this to be so.
If HR seems all over the place, some of the time. The only way to diagnose AF is if you have "funny" HR readings hen to have a 24 or better still a 7 day monitor, GP or cardio, that does lots of little ECG`s and is fairly foolproof The other way is to be on a normal ecg monitor in hospital, for some time. You can have days with no AF. The BP tends to be low at the time of being in AF This testing did not exist years ago and I had many ECG`s and echo`s, the cardios and other docs, and certainly me knew some thing was very wrong. With AF it is vital to be on anti coagulation to avoid clots.but normal life is still the same.
I hope this is some help to you.