Of course there would be competition. But like I said, I'll refer to the endovascularsurgery IR's who are based out of San Jose, California which is a highly desired locale for doctors. There is an oversaturation of doctors in the Bay Area, so plenty of cardiologists, but these guys still have a very busy practice. They established a referral system with PCP's and get the patients straight from PCP's or patient self-referrals. Gvataken, the IR attending who posts on SDN from time to time and some of the other IR attendings (ie. irwarrior) who have posted here in the past have stated as long as you run a clinic you will get patients. It takes time to build a practice but it is doable.
I'm not going to lie, but I have seen a community program where the cards guys are very aggressive in PVD, and have basically taken all the peripheral work from IR. But in those cases the IR guys were not clinical, they did not admit their own patients nor run clinics. They were relegated to venous and other procedures outside the realm of the arterial system.