As a tech diver/instructor and interventional cardiologist, I agree completely with the staff at Duke Dive Medicine above. Mitral regurgitation is not a contraindication to diving as long as you have normal heart muscle function and adequate exercise tolerance. As mentioned, the main reommendation for diving with a PFO is to dive conservatively and limit your venous bubble load -- avoid decompression diving, long safety stops, nitrox, etc.
By the way, I am doing a research study in conjuction with Divers Alert Network (DAN) looking at divers with PFO. All of the information is available at [not allowed to post URL] DAN: Divers Alert Network - Scuba Diving and Dive Safety Association.
Many thanks.