A patent foramen ovale (PFO) is essentially a hole in the heart. The foramen ovale is an opening, similar to a small flap, between the heart's top left and right chambers (atria). Everyone is born with this opening, which is essential to the blood flow of the developing fetus. After birth, this opening generally seals itself closed within a few months as the heart begins its normal function of pumping blood on its own. But if the opening doesn’t close and remains open as a hole, it becomes a PFO, which happens in about 25 percent of the U.S. population.1 There’s no definitive cause for why it happens, although some researchers believe genetics may play a role. In most cases, the PFO causes no problems, and a person goes on to live a normal, healthy life. However, in some cases, a PFO has been linked to other health issues, such as migraines and ischemic stroke. Studies have also found that some people with a PFO suffer a cryptogenic stroke. Without other identified factors, these strokes may be related to a PFO.
The heart serves as a pumping system; to understand it, it is best to understand exactly how the heart works. In short, the heart is divided into four chambers: the left and right atria and the left and right ventricles. A thick wall called the septum separates the left side of the heart from the right. The valves, or one-way doors within the heart, separate the atria from the ventricles. The valves carefully regulate blood flow through the heart’s chambers. The walls of the heart and the valves keep the blood on a “one-way street” through the heart and out to the body and back.
In those with a PFO, minimal blood usually crosses freely between the right and left atria due to the small pressure difference between these two chambers. However, activities (lifting heavy weights, for example) or changes in the chest geometry (after surgery, for example) can lead to changes in the pressures inside the heart, leading to more blood passing from the right atrium to the left atrium through the PFO. For many people, the pressure change is usually not felt and does not lead to a problem in most cases. However, any particles in the blood or any type of blood clot can pass through the PFO, move out of the heart, and travel to the brain, which may cause a stroke.