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Among healthy older adults who were followed for more than a decade, the presence of a patent foramen ovale (PFO) was not associated with ischemic stroke or subclinical cerebrovascular disease, researchers found.

After adjustment for potential confounders, asymptomatic individuals with a PFO were not more likely to have a stroke (hazard ratio 1.10, 95% CI 0.64 to 1.91) or an MRI-detected silent brain infarct (adjusted odds ratio 1.15, 95% CI 0.50 to 2.62), according to Marco Di Tullio, MD, of Columbia University in New York City, and colleagues.

A PFO also was not associated with a greater risk of combined vascular events (adjusted HR 1.13, 95% CI 0.81 to 1.57), the researchers reported online in the Journal of the American College of Cardiology.

The results "suggest that PFO should not be considered a significant risk factor for cerebrovascular events in the general population" and "reaffirm that no preventive treatment is needed in asymptomatic subjects with an incidentally detected PFO," the authors wrote.

They noted that the findings are consistent with prior population-based studies and discordant with case-control studies in which PFO has been strongly associated with stroke risk.

"The combined information of the negative population studies and positive case-control ones suggests that a small subgroup of individuals with a PFO at high stroke risk may exist, but their effect on the stroke incidence in a general population sample is diluted when all individuals with PFO are considered," Di Tullio and colleagues wrote, adding that it remains unclear how to identify those high-risk individuals.

In addition, two randomized trials testing whether plugging a PFO would reduce the risk of recurrent stroke failed to show a benefit for the plugged group. The results were reported last year at the Transcatheter Cardiovascular Therapeutics meeting.

The researchers examined the relationship between PFO and both clinical and subclinical cerebrovascular disease among 1,100 stroke-free individuals, older than 39, from the Northern Manhattan Study; a subset of 360 individuals underwent brain MRI scans.

Overall, 14.9% of the cohort had a PFO detected by transthoracic echocardiography. The rate was slightly higher (16.7%) in the subset that underwent brain imaging.

Through an average follow-up of 11 years, 10.1% of the overall cohort had an ischemic stroke -- 9.2% of individuals with a PFO and 10.3% of the others without PFO.

The risk of stroke did not differ based on the presence or absence of a PFO after adjustment for age, sex, atrial fibrillation, diabetes, hypertension, hypercholesterolemia, and smoking.

Of the individuals who underwent MRI, 14.4% had a silent brain infarct detected -- 16.7% of those with a PFO and 14% of the rest. The presence of a PFO was not associated with subclinical cerebrovascular disease after multivariate adjustment.

The findings were consistent regardless of whether the PFO was associated with an atrial septal aneurysm.

In an accompanying editorial, Deeb Salem, MD, and David Thaler, MD, of Tufts Medical Center in Boston, noted that the high average age of the study cohort (about 68) influenced the interpretation of the findings because previous studies have shown a stronger relationship between PFO and stroke in younger individuals.

The weakening of the relationship in older individuals could be related to the increasing presence of various competing causes of stroke.

"Conventional vascular diseases likely 'drowned out' the PFO-associated risk that might have been detectable in a study of younger subjects," Salem and Thaler wrote.

They also pointed to the use of transthoracic echocardiography to detect PFO in the study. That test has been shown to have a sensitivity of only about 50%, making it likely that some of the individuals in the non-PFO group in the current study actually had a PFO, they wrote.

"Unfortunately, these data do not settle this issue [of the association between PFO and stroke]," they wrote.

"If a population at risk from their PFOs is going to be identified before their first stroke, it needs to be done in people who are in their 20s and 30s (and perhaps 40s), with PFO status defined by transesophageal echo or transcranial Doppler and perhaps also described in detail beyond present/absent, and with or without atrial septal aneurysm," they wrote.

"A focus on asymptomatic subpopulations that may be at higher risk of a first-ever stroke -- e.g., migraine with aura, obstructive sleep apnea, and those with silent infarcts -- is likely to increase the success of the next population-based study," they added.

From the American Heart Association: