Scott,
I'm happy to hear that your son passed the venogram and that he is able to come off of the anti-coagulants. However, there is a possibility that your son may have arterial TOS- not a great possibility but one non the less. I have similar symptoms to your son (do a search for my name- also in introductions) and have been DX'd with ATOS. I passed my venogram with flying colors in 08. But failed miserably in the TOS positional doppler/ultrasound a few weeks ago- confirming that my left subclavian artery is severely compressed when my arm is above 90 degrees. Limiting all blood flow.
Please seek further consultation/testing to confirm/deny ATOS. I different Surgeon from the one I saw in 08 found that it was ATOS instead of possible VTOS.

Hope this helps, please feel free to PM me with questions,
Jocelyn