I'm an interventional cardiologist (and Kiss CCR diver/instructor) who spends his days opening clogged coronary arteries and closing PFOs.
Unfortunately, a nuclear stress test is designed to look at blood flow to the heart but does not image the atrial septum (where a PFO would be). The best test for a PFO would be a transesophageal echo with the injection of agitated saline.
I just wrote an article about PFO in this month's issue of Underwater Journal (
Underwater Journal). After reading it, if I can be of any help, PM me.
Best of luck on your stress test!
Doug