This is worth a read, there was also an article in Wet Notes that I'll try and find for you.
Everything You wanted To Know About PFOs and Decompression Illness, But Were Too Busy Decompressing to Ask
Though your chances of getting bent are relatively low, your risk increases five to 13-fold in the presence of a patent foramen ovale (PFO), which may enlarge and become problematic with age. Skin bends anyone? Here cardiologist and rebreather instructor Doug Ebersole explains the latest...