Patent foramen ovale is not an independent risk factor for stroke

Researchers at Mayo Clinic have found that a patent foramen ovale ( PFO ), a small hole between the two upper chambers of the heart, does not predestine an individual to a stroke later in life.

Findings appear in the Journal of the American College of Cardiology.

"In the general population, it does not appear there is a direct association between the detection of a patent foramen ovale and having a stroke," says Irene Meissner, at Mayo Clinic and lead study researcher. " Our study looked at the general population with patent foramen ovale; if you detect patent foramen ovale in someone who has already had a stroke, one cannot immediately assume that the patent foramen ovale is causative."

Adds Bijoy Khandheria, at Mayo Clinic in Arizona and study author, " Our findings show that the hole is not always the guilty party in a stroke; it may be an innocent bystander. If someone says you have a tiny hole in your heart, it's not doom and gloom. After following patients in our study with small holes in the heart for five years, their risk for stroke was no different than those who did not have the hole."

Patent foramen ovale is a common, benign, congenital condition occurring in one out of four people in which the partition between the upper right and left heart chambers fails to close shortly after birth. PFO also is often a stealth condition. " Most people don't know they have this -- it's usually a silent condition," says Meissner.

According to the study researchers, PFOs are now detected more often, usually by chance, due to more frequent use of cardiovascular imaging.
A transesophageal echocardiogram is considered the best test to detect a hole in the heart.

The current practice of closing PFOs derives from many observational research studies demonstrating higher incidence of patent foramen ovale in stroke patients.

Due to the lack of association between patent foramen ovale and later stroke found in this study, the Mayo Clinic investigators indicate that closure surgery should not be reflexive.

" We now see that a hole in the heart leading to stroke is not borne out in our study, the largest transesophageal echocardiogram-based study of the general population," says Khandheria. " Just because you have a hole, you don't automatically need to have it closed. You don't need to panic."

Meissner agrees. " More people are now getting PFOs repaired unnecessarily," she says. " Some don't need to be fixed. For patients who know they have a patent foramen ovale and have not had neurologic symptoms, I'd advise them to sit tight. They don't need heart surgery to close the patent foramen ovale."

The investigators emphasize that their findings do not lead to specific clinical recommendations for patients with patent foramen ovale who have already suffered a stroke, as their study examined people randomly selected from the general population, rather than a group of stroke patients.

Meissner and Khandheria offer other insights relating to patients with patent foramen ovale who have had a stroke. First, they point out that it's important to verify that what's deemed a stroke is in fact a stroke. Symptoms such as dizziness, numbness or weakness are at times misinterpreted as a transient ischemic attack -- sometimes dubbed a ministroke -- says Khandheria.

Second, it is important to bear in mind that patent foramen ovale as a cause for stroke is often diagnosed by deduction in cases where there are no other plausible explanations, according to Meissner. " If you've had a stroke and have a patent foramen ovale, you can't make the automatic assumption that it's related," she says. " If you've had a stroke, what you need is a careful neurologic assessment by a neurologist to determine the possible underlying causes of the stroke so that an appropriate decision can be made regarding the need for patent foramen ovale closure."

Khandheria also encourages those who have a patent foramen ovale and have experienced stroke to see a neurologist who might "search harder for other causes before recommending closure" due to the invasive nature of a patent foramen ovale closing procedure, associated risks of closure, and the lack of guarantee that patent foramen ovale closure will prevent another stroke.

The study investigators also note that two multicenter trials are under way to test the relevance of a patent foramen ovale in patients who have suffered a stroke.

In the Mayo Clinic study, 585 randomly selected people 45 years or older from the general population in Olmsted County, were studied with a transesophageal echocardiography to detect patent foramen ovale.

Of this group, an echocardiographer identified patent foramen ovale in 140, or 24.3 percent.

After a median follow-up of 5.1 years, 41 subjects experienced cerebrovascular events such as death due to cerebrovascular disease, ischemic stroke or transient ischemic attack.

After the researchers adjusted the findings for patients' ages and existing diseases unrelated to stroke, they found that patent foramen ovale is not an independent risk factor for stroke.
The researchers also found no difference in risk for stroke by size of patent foramen ovale in this study.

Source: Mayo Clinic, 2005