Angiogram

The procedure is called an angiogram and is well discussed at the page linked to below. Don't be put off by the basic claim, read on and learn from those who've been there, if you find yourself confronted with approving the procedure just bear in mind the final words of "MMaslek" (about half way down the page).
https://www.inspire.com/groups/womenheart/discussion/angiogram-dye-injections/

The results are in

So they had their wicked way with me and stuck a tube (catheter-very thin tube) in my groin to roam around in my heart and inject dye to enable (X-Ray?) viewing of my heart and it's blood supply arteries. Turns out I'm very lucky, I have a restriction caused by some partially dislodged plaque buildup. Medication is the preferred mode of treatment for this problem, plus a healthy dose of exercise and healthy eating.

So would a lie down help?

After a weary while of dull, annoying pain the thought of a lie down seems sensible

Oh, it's just annoying....

So after an hour it becomes annoying and you just want it to stop

That persistent pain, what is it?

So you get up in the morning and go about your usual tasks and then after a while realise there's a dull, persistent pain in your chest that wasn't there earlier. It must have crept up on me, I don't remember it starting.
After a while I began to dismiss it to a gastric problem due to it's persistence, and arguably wanted to disregard a cardiac episode, the pain just didn't seem "bad enough" , it was just annoying and prolonged.....