Angiograms are the gold standard for seeing inside your coronary arteries and they can measure the blood flow rate/pressure anywhere
in those arteries. After my 6th
Angiogram, I had to ask them to start using my other leg because all the scar tissue was starting to get a bit painful with each new procedure.
On a personal note, there is nothing to fear. It's better to remain calm and see the fascinating technology with awe.