I second Jomar

I have ATOS- but no cervical rib on either side. I did not develope a blood clot- tho I was at extreme risk of doing so. As soon as the results came out- I was instructed to limit ALL overhead activity (anything above 90 degrees) and all weight bearing activity- including push ups. You may very well have an abnormality of multiple causes- too much muscle, to thick of a first rib, too tight of a space... any number of things. From what I read of your results, I would say that you have Venous TOS as well as ATOS. Clearly you completely lose your pulse in specific positions- as did I. I have ATOS primarily, but I have VTOS involvement as well as my subclavian vein was compressed also. But again, I never developed a clot, though I was at extreme risk.
You had an arterial extam- what did this consist of? I had an ultrasound (lengthy) of both arms in all positions to view the artery, veins and moniter blood flow. This visualization was excellent and showed where, how and why there was a compression.
I suppose you could have a venogram completed as well as a further invasive artery exam, but I would suggest getting the ultrasound that I described above.
Also, as far as getting diagnosed with ATOS without a clot- that is bogus. I know the DR was an "expert" (Pixified) but it's a bogus statement that a patient doesn't have ATOS when presenting without a blood clot.
If I can be of further help, please let me know.

Jocelyn