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Other Heart Disease - PFO

Patent Foramen Ovale (PFO)

What is it?

PFO is a common congenital heart defect that has only recently been identified as a possible cause of stroke. The foramen ovale is a hole between the chambers of the fetal heart, enabling blood to enter the left atrium from the right atrium. This blood contains oxygen from the mother’s placenta, which moves into the right ventricle and is pumped to the baby’s body. After birth, the baby is breathing on its own so this blood flow is no longer needed. In most people, the foramen ovale closes within the first year of life. In 1 in 4 adults, however, the hole does not close completely—a condition called patent foramen ovale, or PFO. PFO is equally common in women and men.

How is it related to stroke?

The current theory is that PFO may be responsible for many previously unexplained strokes, especially in younger patients. According to the theory, clots from the veins in the lower legs travel back to the right atrium. In the normal heart, these clots would be pumped from the right ventricle into the lungs and stop there. In patients with a PFO, the clot can pass through the opening and be pumped from the left ventricle to the brain, causing a stroke or TIA. There is ongoing debate about whether PFOs are responsible for most unexplained strokes, or whether there is some other cause.

Because a PFO usually doesn’t cause any heart problems, most people don’t know they have it. It is most often discovered when someone suffers an unexplained stroke.

How does it affect my stroke risk?

PFO is present in 30% to 40% of patients who have an unexplained stroke.13 Currently, the evidence remains split on whether having a PFO really makes you more likely to suffer a stroke, with some studies finding a strong risk and some finding no association.

Many small observational studies have found an association between PFO and risk of stroke, which has driven the development of drug regimens and implantable devices to prevent stroke in these patients. For example, a study of 503 consecutive stroke patients (38% were women) found that PFO patients of any age were 3 to 4 times as likely as their peers to suffer an unexplained stroke.14, 15

However, more recently several large population-based studies have concluded that having a PFO does not increase stroke risk after other stroke risk factors are taken into account.16 In the prospective Northern Manhattan Study that followed 1100 people (58% were women) 39 years of age or older for 7 years, people with a PFO had no increased stroke risk after adjustment for other risk factors.17 This was true in both men and women and in people of all races.

For now, the jury is still out, and research into the relationship between PFOs and stroke is ongoing. Future randomized trials should be able to determine who, if anyone, with a PFO has an elevated stroke risk, and exactly how great the risk is.

What can I do to prevent stroke?

A PFO is usually not detected unless tests are performed to identify possible causes of stroke, but occasionally it will be found on its own. In these patients, no special treatment is necessary.

Patients whose PFO is discovered after an unexplained stroke or TIA are often treated with a blood thinner such as warfarin (Coumadin) or anti-clotting drugs such as clopidogrel (Plavix) or aspirin to prevent stroke.

Another option for the prevention of recurrent stroke is to close the foramen ovale. This can be done with minimally invasive surgery, or with a noninvasive method in which a catheter (like the one used for an angiogram) is inserted into the heart through a vein in the groin, where it deploys a device that permanently closes the hole.

Most studies of PFO treatment with medicine or devices have been too small to determine whether they really prevent future strokes, so current treatment decisions are usually based on physician and patient preferences.18 There are several large prospective clinical trials underway to try to find out whether PFO treatment really helps to prevent stroke, and which treatment is best.

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