Patent foramen ovale: the common heart finding that's usually not a problem

A patent foramen ovale is a small, flap-like opening between the heart's two upper chambers that's a completely normal part of fetal circulation, allowing blood to bypass the not-yet-functioning fetal lungs — and in most people, this flap seals shut naturally shortly after birth as pressure changes in the newly functioning lungs push it closed. In roughly a quarter of adults, it doesn't fully seal and remains as an incidental finding, present but functionally inconsequential for the overwhelming majority of that group for their entire lives.

This prevalence is worth sitting with for a moment: a PFO showing up on an echocardiogram ordered for an unrelated reason is extremely common and, on its own, is not a diagnosis requiring treatment — it's closer to an anatomical variant than a disease, and the vast majority of people who have one will never experience any related symptom or complication connected to it.

The situations where a PFO does become clinically relevant are more specific: it's an area of active investigation in certain types of stroke, particularly in younger patients where a PFO potentially allowed a blood clot to bypass the lung's normal filtering function and travel directly to the brain — a mechanism called paradoxical embolism. PFO is also discussed in the context of certain migraine patterns and, notably, decompression sickness risk in divers, where the same right-to-left bypass mechanism is relevant to a different physiological process entirely.

For most people who learn they have a PFO as an incidental finding with no connection to stroke, unexplained migraine, or a specific risk activity like diving, the appropriate response is generally reassurance rather than intervention — closure procedures exist and are used in specific, carefully selected clinical scenarios, but a PFO discovered incidentally in someone without one of these specific associated conditions is not, on its own, a reason for concern or treatment.