updated 10/31/2006 11:13:51 AM ET 2006-10-31T16:13:51

One in five adults has a little hole in the heart. Most will never know it. But the defect may play a role in certain strokes and severe migraines, leading thousands to get devices implanted to seal it shut.

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The problem: Doctors haven’t yet proved when the hole is harmful, and whether fixing the heart in turn helps the head.

It’s a controversy dividing cardiologists, even as use of the umbrella-shaped implants steadily rises. Now the Food and Drug Administration has taken an unusual step to push manufacturers to settle the issue, stopping promotion of the expensive implants.

“What’s really incumbent upon us now is proving these relationships and proving that closing the hole is beneficial,” says Dr. Robert Sommer of Columbia University Medical Center, who implants the devices and is helping to study them.

Everyone is born with a tiny flap-like opening between the heart’s two upper chambers. Usually, it grows shut during infancy. But in at least 20 percent of the population, the opening doesn’t heal over, a defect called “patent foramen ovale” or PFO.

Hole linked to blood clots
When blood returns to the heart, it’s supposed to go to the lungs to pick up more oxygen and be filtered clean. A PFO can allow some blood to seep back into circulation without that filtering step. The theory: That could allow small blood clots or other substances into the bloodstream, traveling straight to the brain.

What’s the evidence? It’s mostly circumstantial. Among people who have strokes at a young age — 55 or under — with no apparent risk factors, up to 60 percent also have a hole in the heart. By some estimates, that could equal 30,000 to 60,000 strokes a year.

In the late 1990s, cardiologists started aggressively sealing PFOs in stroke survivors, in hopes of lowering their risk for further strokes. They threaded tiny implants into the heart through a hole in the groin, pulling them against the PFO’s flap to seal it shut.

Then some implant recipients started reporting an odd side effect: Their migraine headaches went away. Subsequent research suggested at least 40 percent of people who suffer a severe type of migraine — the kind that comes with an “aura” or visual disturbance — have fairly large PFOs.

'We need the data'
None of that research proves a PFO actually causes the ailments, cautioned Dr. Joseph Carrozza of Boston’s Beth Israel Deaconness Hospital, in a debate about whether to close the holes at an international cardiology meeting last week.

“Association is not causation,” Carrozza said, noting that the vast majority of people with PFOs will never report symptoms, and that PFO closure occasionally causes such serious side effects as blood clots and irregular heartbeats.

“I would argue passionately ... we need the data.”

Studies comparing the $23,000 implants to stroke-fighting drugs are going on now. Yet PFO closure already is widespread in Europe. And until this week, the FDA had allowed two manufacturers to market implants here for repeat-stroke sufferers, under a special rule that lets promising devices for rare conditions sell before there’s final proof that they work.

But with PFO closure no longer rare, the FDA has withdrawn that special approval, urging makers NMT Medical and AGA Medical to finish their studies and tightening, slightly, how stroke patients get the devices in the meantime. Both makers have pledged to push forward, although Sommer notes that repeat-stroke sufferers often want their PFOs closed despite the controversy, and thus won’t enter a study.

Migraine patients to test implants
Proponents say migraines may settle the questions faster — because the only way a migraine sufferer can receive a PFO-closing implant today is through a clinical trial. Three major U.S. studies have begun recruiting hundreds of patients whose aura-inducing migraines overwhelm medications. Those patients would test competing implants.

Among them is the first dissolvable implant, NMT’s BioStar, made of collagen that’s designed to hold the PFO closed until the heart’s own cells seal it over, and then to degrade. “It’s designed to repair this defect in a very natural way,” said Dr. Michael Mullen of London’s Royal Brompton Hospital, who reported promising results from BioStar’s first human safety test in the journal Circulation last week.

Next up: trying to weld PFOs shut with heat, beaming radiofrequency energy into the heart, instead of using an implant. Studies have begun in Europe.

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