Hello – I’m not familiar with that specific issue occurring after a tetanus shot, but this link will allow you to report a reaction. This process is managed by the U.S. FDA and Centers for Disease Control – and the data is used to spot potential vaccine issues.
The 200 bpm must have been terrifying. Hopefully, your endocrinologist is in the loop, is monitoring your levels accordingly, and is having a discussion with you about treatment options – instead of the ER staff trying to get you stabilized and sending you out the door!
This piece from Mayo Clinic on beta blockers might also be worth a read – any chance you are also dealing with diabetes?