About three days if all goes well, but (without wanting to worry you) occasionally complications can ensue - bleeding at site, clots being thrown off down leg, procedure not working. I'd be cautious about booking anything until you are sure it has all gone well -at least have a low threshold for bailing out, you don't want anyone feeling pressurised to fly before they are ready. Blocked arteries in leg are sometimes associated with furry arteries elsewhere eg the heart so not always a good idea to reduce O2 at altitude esp after a major procedure. Oxygen supply to the leg will also be worse up high.
All that said, the vast majority are completely uneventful so don't get too worried
Hope it all goes well,
GM