Heart ultrasound is used to diagnosis patent foramen ovale (PFO). A saline solution is shaken vigorously to create microbubbles and then injected into the body. Ultrasound detects the flow of the microbubbles through the heart, showing if they travel through a hole between the atrial (upper) chambers, thus diagnosing PFO. There is no serious risk involved; this noninvasive procedure does not require radiation. Check out the example of how to diagnose patent foramen ovale from Dr. Khandheria of Aurora Health Care.