Patent Foramen Ovale (PFO)

What is a patent foramen ovale?

The foramen ovale is a small hole between the 2 upper chambers of the heart (the left atrium and the right atrium). It exists before birth and usually closes after birth.

Before birth, the fetus gets oxygen into its blood from the placenta, not from the lungs. The foramen ovale allows oxygenated blood to bypass the lungs and get pumped to the rest of the body. After birth, however, this opening can cause problems because it allows blood to bypass the lungs. The blood can't pick up enough oxygen.

There is a flap on the wall that separates the left atrium from the right atrium (the atrial septum). Before birth, the pressure on the right side is greater than on the left side, and the flap stays open. After birth, the pressure on the left side is greater than on the right side, so the flap is pushed against the septum and closes the hole. Over the first few months of life, the flap gets sealed to the septum.

Sometimes the flap does not seal. When this happens, the foramen ovale may open if the pressure on the right side of the heart becomes equal with the pressure on the left side of the heart. When the flap stays open, the foramen ovale is said to be patent.

How does it occur?

It is not known why the flap seals in some people but not in others.

What are the symptoms?

A patent foramen ovale can cause 2 kinds of problems.

If you develop blood clots in the veins in your legs, these clots can break off and float to the lungs (pulmonary embolus). If these clots are large enough, or if there are many of them, the lungs can be damaged. If you also have a patent foramen ovale, a different kind of damage can occur. It is possible for the blood clot to travel to the left side of the heart, and then to the brain (causing a stroke or TIA). It may also damage other organs in the body.

If you develop an abnormality in the blood vessels in the lung (pulmonary hypertension), the pressure in the right side of the heart may become much higher than the left side. A lot of blood flows from the right to the left before it has had a chance to pick up oxygen. This causes the overall oxygen level in the blood to drop and will make your shortness of breath much worse.

How is it diagnosed?

The best test to diagnose a patent foramen ovale is an echocardiogram. A small amount of fluid is injected into an IV during the echocardiogram. This helps the healthcare provider identify blood moving abnormally from the right side to the left side of the heart. The fluid contains tiny bubbles that are detected by the echocardiogram.

How is it treated?

If the PFO does not cause symptoms, no treatment may be needed. Scuba divers may be an exception this rule. During decompression after diving, small nitrogen bubbles may form in the blood. These bubbles may act like blood clots and cause small strokes or damage to other organs. Talk with your healthcare provider if you are an active diver, such as an instructor, divemaster, researcher, or photographer.

If PFO causes symptoms, treatment options are anticoagulants (blood thinners), surgery to close the hole, or placement of a tiny umbrella device to cover the hole. This umbrella can be placed without surgery through a catheter.

When should I call the doctor?

If you have a known PFO, regular checkups are recommended. Call your doctor if you notice a sudden increase in shortness of breath, you awake at night short of breath, or you become aware of an irregular heartbeat.