Patent Foramen Ovale: What You Should Know

In recent years, many people who have echocardiograms are being surprised with the information that they have a congenital cardiac condition called “patent foramen ovale,” or PFO. 

The advice these people receive after being given this diagnosis will vary wildly. Some doctors will want to treat them with warfarin or aspirin to try to prevent blood clots. Others will recommend an invasive heart procedure to install a special device to close the PFO. Still, other doctors will tell them that a PFO has no real significance at all and that no therapy is required.

This article summarizes what is known about PFO and attempts to place the current controversy regarding its treatment into perspective.

Doctor checking patient's heart
jacoblund / istock 

What Is a PFO?

In the developing fetus, the foramen ovale is an opening that is normally present in the atrial septum (the thin structure that separates the right atrium from the left atrium), which allows blood to flow freely from the right atrium directly into the left atrium. This flow of blood from the right atrium to the left atrium is necessary during fetal development, as it allows the circulating blood to bypass the developing lungs. (A fetus receives its oxygenated blood from its mother, through the placenta.)

At birth, when a baby begins to breathe, the pressure in the left atrium rapidly increases and pressure in the right atrium decreases. This pressure gradient causes a flap of tissue to impose itself over the foramen ovale, effectively closing it. At this point, blood no longer is able to flow across the foramen ovale, from the right to the left atrium.

In most people, this flap of tissue closing the foramen ovale becomes sealed, so the foramen ovale effectively no longer exists. However, in about one out of four normal adults (25 percent), the tissue flap is not completely sealed off and relies on the higher pressure in the left atrium to keep the foramen ovale closed. When the pressure in the right atrium becomes intermittently higher than in the left atrium (as can occur, for instance, when coughing), for those brief intervals the foramen ovale can open, and, momentarily, blood can again flow from the right atrium across to the left atrium. These people are said to have a patent foramen ovale. A close look at the heart's structure and how it works can provide a better understanding of this mechanism.

How Is PFO Diagnosed?

Doctors diagnose PFOs with echocardiography. Not all PFOs are the same, and some are much more difficult to detect than others. In a few cases, the PFO is fairly obvious and would be noticed by almost any echocardiographer. More often, special maneuvers are necessary to identify a PFO, including trans-esophageal echocardiography, injecting contrast material into the bloodstream (the “bubble study”), and even applying positive pressure to the airway through a special breathing apparatus. The harder the echocardiographer works to identify a PFO, the more likely he or she is to see one.

In some people, the flap of tissue that covers the foramen ovale can develop a balloon-like bulge, which is called an atrial septal aneurysm (ASA.) In most cases, an ASA is accompanied by a PFO, so these two conditions are generally associated with one another. The ASA and PFO are thus very similar, and it is probably not incorrect to think of an ASA as a slightly exaggerated (and perhaps somewhat more significant) instance of a PFO.

What Is the Significance of a PFO?

Cryptogenic stroke: The reason doctors are concerned about PFOs is that, during those transient episodes when the right atrial pressure is higher than the left atrial pressure, blood can flow from the right atrium to the left atrium. If an embolus(a blood clot that moves through the vascular system) happens to be traveling through the right atrium at that moment, it too can enter the left atrium. From the left atrium, the clot can then flow through the left ventricle, and from there enter the arterial system, to any part of the body. If the clot goes to the brain, it could cause a stroke. Thus, the chief concern regarding a PFO is that it might lead to an increased risk of stroke.

It is now believed that PFO is one cause of “cryptogenic stroke” — that is, a stroke whose cause remains unknown after a full medical evaluation. However, because the prevalence of PFOs is so high, especially if you look for them hard enough, simply finding a PFO in a person who has had a stroke by no means proves the PFO was responsible for the stroke.

Recent studies have suggested that in people under the age of 60 who have had a cryptogenic stroke, and who also have a large PFO (or a PFO associated with an ASA), closing the PFO has been associated with a reduced risk of recurrent stroke. (PFOs can be closed with a special implant that can be inserted via a catheter.)

However, PFO closure is not a risk-free procedure, and the benefit from doing so has been seen only in very carefully screened patients. This is because most cryptogenic strokes are not caused by PFOs, even when a PFO is identified. PFO closure should be considered in stroke survivors only after a full evaluation by both a cardiologist and a neurologist.

Migraines: Some studies have suggested that migraine headaches are more common in people who have PFOs. But other population studies have shown no association between PFOs and migraines. So even an association between migraines and PFO is questionable. Furthermore, no plausible physiologic theories have been identified as to how a PFO might cause migraines.

The lack of such a theory has not prevented some doctors from recommending PFO closure devices in migraine sufferers. Some who performed this procedure reported that people with migraines experienced a reduction in symptoms. Because of this claim, a randomized trial was organized to study whether PFO closure was effective. This sham-controlled study, published in 2008, showed no benefit at all with PFO closure.

At this point, there is little reason to believe that PFOs are a cause of migraine headaches. Offering PFO closure to migraine sufferers is to inappropriately take advantage of the fact that they are all-too-often desperate for anything that someone claims might help them. Most people with migraines can achieve reasonable control of their symptoms if they can find a caring doctor and work closely with him or her.

Platypnea-orthodeoxia syndrome. Platypnea-orthodeoxia syndrome is a rare condition in which a person becomes short of breath and suffers from low blood oxygen levels while in the upright position. This condition requires not only a PFO but also some other cardiac condition that causes the PFO to open when a person stands up. Generally, this “other condition” is an additional structural abnormality in the heart that promotes blood flow from the right atrium into the left atrium. Closing the PFO is generally one of the steps required to treat this rare syndrome.

A Word From Verywell

Patent foramen ovale is a “modern” medical diagnosis, made prevalent only in the past few decades with the advent of echocardiography. While PFO is thought to be an uncommon cause of cryptogenic stroke, in the large majority of people who are diagnosed to have a PFO, no medical problems are likely ever to result from it.

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