HR + power zones concern

For the past 3 weeks I’ve been experiencing an unusually high HR which is more evident on my outside rides (at temperatures between 0-9 degrees Celsius). Inside is high too, just not as significant as outside.

I use a power meter to train and is set to my FTP. I test my FTP regularly.

I am currently suffering anxiety/depression and my doctor says this is the reason for my unusually high heart rate.

My main concern is with implications for my training if I continue to train at power. For example, if using my max HR as a guide (192), 70-75% of that is 134.- 144. Currently, I can’t even spin backwards without my HR reaching 130! If I did use my HR to train I believe I would be wasting my time.

Typically, my current HR at the high end of z2 (using 5 zone model) is at around 160bpm (which is where it used to be for sweetspot). Low end of z2 is 150-155bpm.

Another thing I noticed is that during the rides, my HR tends to drift downwards rather than upwards at the same power output. Here is a ride with data for reference:

Can anyone comment on what the implications could be if I continued to train at power? Is this something anyone else has experienced?