"In the general population, it does not appear there is a direct association between the detection of a PFO and having a stroke," says Irene Meissner, M.D., Mayo Clinic neurologist and lead study researcher. "Our study looked at the general population with PFO; if you detect PFO in someone who has already had a stroke, one cannot immediately assume that the PFO is causative."
Adds Bijoy Khandheria, M.D., chair of the Division of Cardiology 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."
PFO 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 Dr. Meissner.
According to the study researchers, PFOs are now detected more often, usually by chance, due to more frequent use of cardiovascular imaging. Physicians now send patients more often to have transesophageal echocardiograms -- heart scans via a probe inserted into the esophagus -- which are conducted to detect a variety of heart conditions. A transesophageal echocardiogram is considered the best test to detect a hole in the heart, indicates Dr. Meissner.
The current practice of closing PFOs derives from many observational research studies demonstrating higher incidence of PFO in stroke patients, according to the Mayo Clinic researchers. The methodologies for many of these studies were problematic, however, according to Dr. Meissner.
How Findings Apply to Patients with PFO
Due to the lack of association between PFO 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 Dr. Khandheria. "Just because you have a hole, you don't automatically need to have it closed. You don't need to panic."
Dr. 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 PFO and have not had neurologic symptoms, I'd advise them to sit tight. They don't need heart surgery to close the PFO."
How Findings Apply to Patients Who Have Experienced Stroke
The investigators emphasize that their findings do not lead to specific clinical recommendations for patients with PFO who have already suffered a stroke, as their study examined people randomly selected from the general population, rather than a group of stroke patients.
Drs. Meissner and Khandheria offer other insights relating to patients with PFO 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 Dr. Khandheria.
Second, it is important to bear in mind that PFO as a cause for stroke is often diagnosed by deduction in cases where there are no other plausible explanations, according to Dr. Meissner. "If you've had a stroke and have a PFO, 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 PFO closure."
Dr. Khandheria also encourages those who have a PFO 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 PFO closing procedure, associated risks of closure, and the lack of guarantee that PFO closure will prevent another stroke.
The study investigators also note that two multicenter trials are under way to test the relevance of a PFO in patients who have suffered a stroke.
How the Study was Conducted
In the Mayo Clinic study, 585 randomly selected people 45 years or older from the general population in Olmsted County, Minn., home of Mayo Clinic, were studied with a transesophageal echocardiography to detect PFO. Of this group, an echocardiographer identified PFO in 140, or 24.3 percent. After a median follow-up of 5.1 years, 41 subjects experienced cerebrovascular events -- inadequate blood flow to the brain -- 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 PFO is not an independent risk factor for stroke. The researchers also found no difference in risk for stroke by size of PFO in this study.
Other Mayo Clinic researchers who contributed to this study include: John Heit, M.D.; George Petty, M.D.; Sheldon Sheps, M.D.; Gary Schwartz, M.D.; Jack Whisnant, M.D.; David Wiebers, M.D.; Yoram Agmon, M.D.; Jody Covalt; Tanya Petterson and Teresa Christianson.
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