If lying flat on your back with arms at your sides causes you to lose blood flow in an arm (or both arms), is that diagnostic regarding having pec minor vs. VTOS vs. ATOS?

This happens to me and the longer I lie there, the more it feels like the pinch point is over the armpit.

Also, has anyone overcome this particular problem with conservative treatment (and which treatment(s) if so)?

I'm doing pec minor stretches, but I just recently started again so it's too early to tell how much they'll help.