I can tell you what my chiro said, it seemed logical to me..
I didn't do much searching about it as it wasn't a big issue for me.

So for what it's worth...

He said compression on a vein would be more likely to have a clot due to the less action and lower oxygen levels = "used blood" more or less.
Where as the arteries have "new" fresh blood and the heart is pumping it directly out and thru the body.

But this theory probably doesn't apply if you are having a constant degree of compression.

We didn't go into any details, it sounded good to me, so I went with it.

I never was at a stage to consider surgery, but I think it is all in what sx a person has and how it affects them overall.