right to the left side of the circulation,” said Dr. Patrick
O’Gara, associate professor of medicine at Harvard
Medical School and executive director of the Shapiro
Cardiovascular Center. Depending on whether the clot
takes a right or left turn as it exits the heart, it can travel to
the brain and cause stroke or TIA. Statistically speaking,
the odds of this happening are low, but it can happen.
HOW WOULD YOU KNOW?
Finding out whether you have a PFO is not easy, and
it’s something that isn’t usually investigated unless a
patient is having symptoms like severe migraines, TIA or
stroke. Although the prevalence of PFO is about 25 percent
in the general population, this increases to about 40 to 50
percent in patients who have stroke of unknown cause,
referred to as cryptogenic stroke. This is especially true
in patients who have had a stroke before age 55. In some
cases, the PFO combines with another condition, such as
atrial fibrillation, to increase the risk of stroke.
For survivors who don’t have a definitive cause of their
stroke, Dr. O’Gara suggests meeting with their neurologist
to discuss the possibility of PFO. “There are many causes
of stroke and having a PFO accounts for only a very small
number,” Dr. O’Gara said. PFO is diagnosed with an
echocardiogram. An echocardiogram, also called a cardiac
echo, creates an image of the heart using ultrasound.
WHAT’S TO BE DONE?
There is currently no FDA-approved treatment for
PFOs. “The greatest myth about PFOs is that they must be
closed. The vast majority of them require no treatment,”
Dr. O’Gara said. “If someone has one that is related to
symptoms, they can be treated with aspirin, warfarin or
Of course, drugs don’t close the hole, “so the aim of drug
treatment is to prevent a clot from forming in the first place,”
Dr. Thaler said. Nothing will close it except open-heart
surgery or a closure device placed by a catheter threaded from
the groin through the veins to the heart. There are currently
no approved catheter-closure devices designed for PFOs.
Until recently, PFOs were closed with devices approved for
repairing ASDs. While the FDA does not prohibit this off-label
use, there is no scientific evidence indicating whether blood
thinners or catheter-closure devices are the better solution.
Several clinical trials are comparing the two approaches.
“We are encouraging doctors to put their patients into the
trials rather than perform off-label closures,” Dr. Thaler said.
The American Academy of Neurology, the American Heart
Association and the American Stroke Association have all
come out in favor of clinical trials.
Until the trials are completed there will be few definitive
conclusions as to the best course of action is for treating PFO.
“Unfortunately doctors are advising patients very confidently
about either using medicine or a closure device,” Dr. Thaler
said. “Neither position is supported by the medical literature,
and that’s why we’re doing the clinical trials.”
For information on PFOs and the clinical trials, visit
here is interest among researchers
as to a possible link between PFO
and “migraine with aura,” a migraine
headache preceded by neurological
symptoms such as a flashing light in one
corner of the person’s vision. The time
between the appearance of the aura and
the headache is usually several minutes.
“About 50 percent of those who have
migraine with aura have a PFO,” Dr. Thaler
said. “Those who have migraine without
aura have PFO numbers similar to the
general population, about 25 percent.”
Not all people with PFO experience
migraines, nor do all migraine sufferers
have PFOs. Although there is anecdotal
evidence that closing the PFO eliminates
migraines in those who have both, there is
no clinical evidence supporting that course
of treatment. “We simply don’t know if
treating or closing the PFO will predictably
help the migraine,” Dr. O’Gara said.
PFO and Migraine
view of a PFO
In a normal heart (left), the foramen
ovale has closed, separating the
right atrium (RA) from the left
atrium (LR); in a heart with a PFO,
venous blood leaks from the right
atrium into the left atrium, then out
to the body