Size may be part of the explanation. Men's hearts are bigger than women's and have greater pumping capacity, and men who get men's hearts fare better. But doctors think differences in hormones or immune systems between the sexes may also play a role.

The study was paid for by the federal government and led by Dr. Eric Weiss, a cardiac surgery researcher at Johns Hopkins University in Baltimore. He presented his findings Wednesday at an American Heart Association conference.

Unfortunately for many patients, the findings won't make much of a difference. About 2,700 Americans are waiting for a heart, and only 2,200 heart transplants are done each year _ some of them second operations for people whose first transplant failed, according to UNOS, the United Network for Organ Sharing, which manages the nation's transplant system.

The average wait for a heart is 108 days for women and 119 for men. Three-fourths of heart transplants are done in men, so by necessity, many must receive organs from the opposite sex.

Smaller earlier studies have found hints that gender differences may play a role in other types of transplants, such as lungs or kidneys, but this is the largest by far to find an effect.

Weiss used UNOS records on 18,240 heart transplants between 1998 and 2007. Among the recipients 77 percent of the men and 51 percent of the women were of the same gender as their donors.

The best results were seen in male-to-male transplants. The worst were in men who received hearts from women.

When the donor was bigger than the recipient, the sex difference did not affect survival. But when the donor was smaller, people did not fare as well.

"The organ may not have the strength to supply blood to the body," Weiss explained.

But the donor's gender made a difference even after size was taken into account, he found.

Matching donor and recipient by gender led to:

_ a 13 percent lower risk of organ rejection in the first year;

_ a 14 percent lower risk of rejection throughout the study, which had an average follow-up of more than three years;

_ a 24 percent drop in the risk of dying in the first 30 days after transplant;

_ and a 20 percent lower risk of dying after one year.

Why the difference? Doctors are not certain. But Dr. Maryl Johnson of the University of Wisconsin-Madison said women who have been pregnant generally have slightly worse outcomes from transplants because their immune systems have been "revved up" from carrying foreign genes from their partners through the fetus.

As for the findings, "it's a huge data set _ I don't think we can disregard it," but the issue needs more study, said Johnson, who heads a UNOS panel that sets policies for heart transplants.

In the meantime, few doctors would advise someone who needs a new heart to pass up one from a donor of the opposite sex.

"Organs are in such scarce supply that it's hard to make a blanket statement," Weiss said. "You're still much better off getting a heart transplant" than waiting and risking your own heart will give out before another becomes available.

___

On the Net:

Heart meeting: http://www.americanheart.org

UNOS: http://www.unos.org

The news follows Pfizer Inc.'s abandonment in December of an $800 million investment in torcetrapib, the leading contender in this class of drugs, because it raised the risk of heart attacks and deaths.

Heart specialists have been anxious to know whether the problems extend to all such drugs and doom this approach.

"A lot of people think it's the next big thing, and we'll need to understand what went wrong with torcetrapib to move forward," said Dr. Steven Nissen, a Cleveland Clinic heart specialist who is president of the American College of Cardiology.

The new studies, reported at the group's conference, gave a mixed answer. The Pfizer drug seems uniquely risky, but other drugs have problems, too.

And even though they and the Pfizer drug raised HDL good cholesterol as intended, that made no difference in the odds of heart attacks or deaths, or key measures of cholesterol buildup in arteries.

Doctors long have focused on lowering LDL, or bad cholesterol, to cut heart attack risk. Statins, sold as Lipitor and Zocor and also in generic form, lower LDL, which ferries fats from food into the bloodstream.

But many statin users suffer heart attacks anyway, so doctors have been trying to boost HDL, or good cholesterol _ which transports fat from the blood to the liver to be disposed of _ to further lower risk.

An extended-release niacin drug called Niaspan, sold by Kos Pharmaceuticals Inc., does this. But it can cause a prickly hot sensation called flushing that some people find intolerable. Pfizer, Merck & Co. and Swiss drug maker Roche Holding AG are testing drugs that boost HDL in a novel way.

Pfizer shares rose 7 cents to $25.73 in afternoon trading on the New York Stock Exchange while Merck stock sank 42 cents or nearly 1 percent to $44.03 on the NYSE. Meanwhile, Roche's U.S. traded shares were flat at $90.05 on the Pink Sheets.

On Monday, scientists reported the results of several studies on torcetrapib. In one, the drug boosted HDL by 61 percent, but trends in death, hospitalization and heart attacks "are all going in the wrong direction," Nissen said.

An experimental diabetes drug by Eli Lilly and Co. that is 10,000 times more potent than fibrates, a current cholesterol treatment, also proved disappointing. The new drug raised HDL but also raised the risk of kidney, heart and other serious problems, Nissen reported.

Finally, infusions of a reconstituted form of HDL developed by CSL Ltd., an Australian company, made no big difference in the burden of artery buildups in a study led by Dr. Jean-Claude Tardif of the Montreal Heart Institute.

In several of these studies there were hints of some improvements in less important measures of artery buildup, which provides "a glimmer of hope for future development of this class of drugs," Dr. Alan Tall of Columbia University writes in an editorial in the New England Journal of Medicine.

That journal and the Journal of the American Medical Association published several of the new studies.

"The bar has been raised a lot for this entire class, but I do not think we can abandon this entire approach," Nissen said.

If Baycol had been the first statin tested and research had stopped after safety problems emerged, there wouldn't even be this class of drugs, he noted. Baycol, sold by Bayer AG, was withdrawn from the market in 2001 after reports of a severe and sometimes fatal muscle disorder.

The stunning results found that angioplasty did not save lives or prevent heart attacks in non-emergency heart patients.

An even bigger surprise: Angioplasty gave only slight and temporary relief from chest pain, the main reason it is done.

"By five years, there was really no significant difference" in symptoms, said Dr. William Boden of Buffalo General Hospital in New York. "Few would have expected such results."

He led the study and gave results Monday at a meeting of the American College of Cardiology. They also were published online by the New England Journal of Medicine and will be in the April 12 issue.

Angioplasty remains the top treatment for people having a heart attack or hospitalized with worsening symptoms. But most angioplasties are done on a non-emergency basis, to relieve chest pain caused by clogged arteries crimping the heart's blood supply.

Those patients now should try drugs first, experts say. If that does not help, they can consider angioplasty or bypass surgery, which unlike angioplasty, does save lives, prevent heart attacks and give lasting chest pain relief.

In the study, only one-third of the people treated with drugs ultimately needed angioplasty or a bypass.

"You are not putting yourself at risk of death or heart attack if you defer," and considering the safety worries about heart stents used to keep arteries open after angioplasty, it may be wise to wait, said Dr. Steven Nissen, a Cleveland Clinic heart specialist and president of the College of Cardiology.

Why did angioplasty not help more?

It fixes only one blockage at a time whereas drugs affect all the arteries, experts said. Also, the clogs treated with angioplasty are not the really dangerous kind.

"Even though it goes against intuition, the blockages that are severe that cause chest pain are less likely to be the source of a heart attack than segments in the artery that are not severely blocked," said Dr. David Maron, a Vanderbilt University cardiologist who helped lead the new study.

Drugs are better today than they used to be, and do a surprisingly good job, said Dr. Elizabeth Nabel, director of the National Heart, Lung and Blood Institute.

"It may not be as bad as we thought" to leave the artery alone, she said.

About 1.2 million angioplasties are done in the United States each year. Through a blood vessel in the groin, doctors snake a tube to a blocked heart artery. A tiny balloon is inflated to flatten the clog and a mesh scaffold stent is usually placed.

The procedure already has lost some popularity because of emerging evidence that popular drug-coated stents can raise the risk of blood clots months later. The new study shifts the argument from which type of stent to use to whether to do the procedure at all.

It involved 2,287 patients throughout the U.S. and Canada who had substantial blockages, typically in two arteries, but were medically stable. They had an average of 10 chest pain episodes a week _ moderately severe. About 40 percent had a prior heart attack.

"We deliberately chose to enroll a sicker, more symptomatic group" to give angioplasty a good chance to prove itself, Boden said.

All were treated with medicines that improve chest pain and heart and artery health such as aspirin, cholesterol-lowering statins, nitrates, ACE inhibitors, beta-blockers and calcium channel blockers. All also were counseled on healthy lifestyles _ diet, exercise and smoking cessation.

Half of the participants also were assigned to get angioplasty.

After an average of 4 1/2 years, the groups had similar rates of death and heart attack: 211 in the angioplasty group and 202 in the medication group _ about 19 percent of each.

Heart-related hospitalization rates were similar, too.

Neither treatment proved better for any subgroups like smokers, diabetics, or older or sicker people.

At the start of the study, 80 percent had chest pain. Three years into it, 72 percent of the angioplasty group was free of this symptom as was 67 percent of the drug group.

That means you would have to give angioplasties to 20 people for every one whose chest pain was better after three years _ an unacceptably high ratio, Nissen said.

After five years, 74 percent of the angioplasty group and 72 percent of the medication group were free of chest pain - "no significant difference," Boden said.

The study was funded by the U.S. Department of Veterans Affairs, the Medical Research Council of Canada and a host of drug companies. Stent makers refused to help pay for the research, said scientists who led the study.

The study renewed a heated animosity between doctors who perform angioplasty and other heart specialists.

In fact, one who does the procedures and who spoke at a meeting in New Orleans sponsored by stent maker Boston Scientific Corp. was responsible for the early release of the study's results, which were not due out until Tuesday.

The study "was rigged to fail, and it did," the Wall Street Journal quoted Dr. Martin B. Leon of Columbia University telling several hundred of his colleagues Sunday night.

"A lot of people have been taking shots at us, and we need to go on the offense for awhile," the Journal reported Leon said.

He claimed to have inside knowledge of the results because he reviewed the study for the New England Journal. The journal would not comment, saying the identity of its reviewers is confidential.

The cardiology college issued a statement saying it was "extremely disappointed" results were released prematurely, "betraying the confidentiality of the scholarly process and the professional integrity of the scientific community."

The college "will be considering strong sanctions against the individual or individuals involved," the statement said.

Boston Scientific shares fell $1.05, or 6.6 percent, to close at $14.22 on the New York Stock Exchange at double their average volume.

Dr. Spencer King of Piedmont Hospital in Atlanta, a leading cardiologist who does many angioplasties, said he was disappointed in the study results.

"How many patients have interventions in which the only expectation is to reduce the use of nitroglycerin or to walk a bit faster? Most patients anticipate a better prognosis and might opt for an extended course of medical therapy if they believe they are not putting their life at excess risk," he wrote in a recent editorial in an American Heart Association journal.

In an interview at the cardiology meeting, King said he recently had surgery for back pain and did not expect permanent relief but added, "If it only held up for five years, I wouldn't be happy about it."

The new study "should lead to changes in the treatment of patients with stable coronary artery disease, with expected substantial health care savings," Dr. Judith Hochman of New York University wrote in an editorial in the journal.

An angioplasty costs roughly $40,000. The drugs used in the study are almost all available in generic form.

Maron, the Vanderbilt doctor who helped lead the study, said people should give the drugs a chance.

"Often I think that patients are under the impression that unless they have that procedure done, they're not getting the best of care and are at increased risk of having a heart attack and die," he said.

Dr. Raymond Gibbons, a Mayo Clinic cardiologist and American Heart Association president, agreed: "This trial shows convincingly that that assumption is incorrect."

Whether it was eaten raw in heart-healthy sandwiches, or in pills made of powdered or aged garlic, the strong-smelling herb had no effect on cholesterol in people whose levels were already elevated, the government-funded study found.

"If garlic was going to have a chance to work, it would have worked in this study," said researcher Christopher Gardner. But it didn't.

Garlic is a longtime folk remedy for a variety of ills, including heart disease, cancer, infections and even mosquito bites. Scientific research on its purported benefits has had conflicting results. Some previous studies suggested garlic might help lower risks for digestive and prostate cancers, or might reduce blood pressure and cholesterol levels; others found no benefit.

Health benefits have been thought to come from a sulfur-containing substance called allicin that is released when raw garlic is chopped or crushed. In lab tests, it can be applied directly to cells and has been shown to prevent cholesterol production.

But any direct benefits to the body from allicin may be diluted when garlic is eaten, said Gardner, an assistant professor of medicine at Stanford University.

Still, Gardner, a garlic lover, was optimistic when he and colleagues began their study. He called the results disappointing but said it's still possible garlic might improve cholesterol when eaten in bigger doses or by people with more severe cholesterol problems. Also, garlic could have characteristics other than influencing cholesterol that might benefit the heart, he said.

The study appears in Monday's Archives of Internal Medicine.

An Archives editorial agreed and said "the jury is still out" on whether garlic might prevent cardiovascular disease.

The study involved 192 adults aged about 50 on average with moderately elevated levels of LDL cholesterol, the bad kind that contributes to heart disease. The average LDL level was 140 milligrams per deciliter of blood, or in the borderline-high range. Below 100 is considered ideal.

Participants were randomly assigned to eat the equivalent of an average clove of garlic in either raw form or garlic pills, or dummy pills, six days weekly for six months.

Raw garlic was mixed into salsa, fat-free mayonnaise or other condiments spread on portobello mushroom sandwiches, chicken quesadillas and other specialty sandwiches. Participants in the garlic pill and dummy pill groups also got sandwiches, but without garlic.

Bad breath and body odor were reported by more than half the raw garlic eaters, and a handful of people in the supplement groups reported flatulence, but there were no major side effects. There also was virtually no effect on cholesterol levels in any of the groups.

Blood samples were taken monthly to detect any changes in cholesterol readings but found none that were statistically significant. Diet and exercise levels also were monitored to detect any changes that could affect cholesterol levels.

Robert Borris, a scientist with the Council for Responsible Nutrition, a trade group for nutritional supplement makers, said the study doesn't answer whether garlic might help regulate cholesterol levels in healthy people.

The results also don't refute scientific evidence suggesting that garlic can reduce the tendency of blood platelets to build up and form clots that could block arteries, Borris said.

"I certainly would not give up on garlic," he said.

"To be able to show the patient what's going on in their arteries is very powerful," says Dr. James Goldstein of William Beaumont Hospital in Royal Oak, Mich.

He's finding that the 3-D pictures of gunk-filled arteries can motivate patients to change their heart-risky behaviors better than lecturing them about high blood pressure or cholesterol.

On the other side, when arteries look clean, "you can say the chance that this patient would have any cardiac event in the next five years will be very, very low," adds Dr. Udo Hoffmann of Massachusetts General Hospital. "If they come back a week later with chest pain, you know it's not the heart."

Sudden chest pain sends about 6 million people to U.S. emergency rooms every year. It's the most common symptom of a heart attack, but a maddening symptom, too _ because half the time it signals something other than heart disease, and telling the difference can be tough.

The dilemma starts with describing the pain. The classic "elephant on my chest" sensation isn't what everyone experiences. Some feel not pain but a tightening of the chest. Others feel pain in the arm, neck or jaw. Some people say it felt like they had a toothache before their heart attack; others felt nausea.

"Trying to sort out whether there's a life-threatening heart problem based on symptoms alone is difficult," explains Goldstein. "Sometimes it seems obvious, and you're wrong. Sometimes the symptoms are unimpressive, and you're wrong. The implications of missing the diagnosis are disastrous."

An electrocardiogram, or EKG, sometimes catches a heart attack in progress, or an artery so unstable that one's imminent.

But at least half the time, early tests are inconclusive and patients are admitted to the hospital for repeat EKGs, blood tests and other checks that can last 24 hours _ and eventually rule out a heart attack two-thirds of the time. Patient anxiety aside, the tab for all that testing surpasses $10 billion annually.

Worse are those whose heart attacks are missed, between 2 percent and 8 percent of patients who are sent home too soon.

Cardiac catheterization _ threading a probe up into the heart to view the inside of arteries _ or stressing the heart with exercise can provide a faster answer, but both are risky so doctors until now have stuck with the wait-and-see approach.

Enter CT angiography. Doctors inject patients with a dye to illuminate artery walls. Then newer machines called 64-slice CT scanners use computerized X-rays to measure both rock-like calcium and soft fatty blockages inside arteries. Within 30 minutes, the 3-D images can show if arteries are narrowed, and how much.

Beaumont researchers studied 197 chest pain sufferers considered at low risk of a heart attack, giving half the souped-up CT scan. The noninvasive test either ruled in or ruled out heart disease in 75 percent, helping to decide who really needed to be hospitalized 11 hours faster than with routine testing, researchers report in this week's Journal of the American College of Cardiology.

Don't reserve the souped-up CTs for low-risk patients, says Mass General's Hoffmann. He tested the scans in 103 patients, 14 of whom had either a full heart attack or a dangerous condition called unstable angina. The CT scans correctly spotted blocked arteries in those patients, and correctly cleared others who had no or minimal clogs, he reported last fall in the journal Circulation.

So who should get the scans? Hoffmann and the Beaumont group both are preparing larger studies to try to settle that, and to tell if CT angiography improves patients' outcomes or just speeds the diagnosis.

Finding clean arteries or very blocked ones makes for an easy diagnosis. But if the clog is medium-sized, is it causing the chest pain and does it need immediate treatment? A CT alone won't be enough to tell, notes Hoffmann.

Nor is even this noninvasive test risk-free. CT scans do involve radiation, and the injectible dye isn't for people with kidney disease.

While some hospitals already are using the CTs to diagnose chest pain, "most physicians at this time are not familiar with a cardiac CT and what it means," Hoffmann cautions.

For now, just insisting on a thorough check may be the best consumer advice. A disturbing new study of more than 7,000 emergency room visits found blacks and women were less likely to get even that first-step EKG than other chest-pain sufferers. The study couldn't explain the disparity, but lead researcher Liliana Pezzin of the Medical College of Wisconsin suspects harried workers in overcrowded ERs were too quick to assume another cause.

"Be your own advocate," Pezzin says. "Say, 'I need to be tested.'"

The findings, from the first study ever to look at heart disease prevalence state by state, showed that states in the Southeast and Southwest were heart disease leaders. Colorado and the District of Columbia had the lowest percentages.

The results line up well with previous, state-specific reports about heart disease death rates, obesity and other risk factors, said Wayne Rosamond, an epidemiology professor at the University of North Carolina who chairs a statistics committee for the American Heart Association.

He called the report by the U.S. Centers for Disease Control and Prevention "very important. It confirms what we know about regional differences in the burden of disease."

For the nation as a whole, roughly 4 percent of those surveyed had had a heart attack. A slightly higher percentage reported angina or coronary heart disease, and 6.5 reported any of those conditions.

But in West Virginia, more than 10 percent had at least one of the conditions. The prevalence in Kentucky was nearly 9 percent, and Mississippi was No. 3, with 8 percent.

CDC researchers drew their data from a 2005 telephone survey of 356,112 U.S. adults in all 50 states, the District of Columbia, Puerto Rico and the U.S. Virgin Islands.

Participants were asked if a doctor or health care professional had told them they had experienced a heart attack, angina, or coronary heart disease. The researchers then statistically adjusted the results to correct demographic differences in state samples to better mirror the U.S. census.

The prevalence in both Colorado and the District of Columbia was a little under 5 percent, tying them for the nation's lowest rate. Hawaii was close behind.

The regional differences are believed to stem from rates of obesity, high blood pressure, high cholesterol, diabetes, smoking and other known risk factors for heart disease, said the study's lead author, Jonathan Neyer, a CDC epidemiologist.

That means the explanation would come from differences in cultural norms, poverty rates and other social factors, and not environmental causes, he said. "There's not something in the water," Neyer said.

Other findings:

_ Among those who didn't finish high school, 1 in 10 had at least one of the conditions. Among college graduates, only 1 in 20 did.

_ More than 8 percent of men had one of the conditions, but only 5 percent of women did.

_ Nearly 1 in 5 people 65 and older had at least one of the conditions. The percentages were much smaller among younger age groups.

_ The results were the same for blacks and whites, with just over 6 percent having one of the conditions. Fewer than 5 percent of Asian-Americans had any of the health problems, making them the healthiest ethnic group. American Indians and Alaska Natives had the highest prevalence, at about 11 percent.

"It has given me a new perspective on life, a new dimension," said Knipp, 61, an El Paso resident who had transplants in 1987 and 1999.

In 1995, Knipp's 17-year-old son was killed in a car accident. His organs were donated and went to at least 70 other people, Knipp said. Despite the tragedy, Knipp says he is grateful for his second _ and third _ chance at life.

"Every day I wake up and I thank God for every breath I take," Knipp said. "It's the little things in life that we really take for granted that I now realize are so wonderful, so big."

Besides celebrating the longevity of some of its patients, the renowned cardiac center marked the 25th anniversary of a program dedicated to repairing failing hearts.

The first successful heart transplant in the United States was performed at the hospital in 1968 by founder Dr. Denton Cooley, who is now surgeon-in-chief. Since then, more than 1,000 transplants have been performed there, according to hospital officials.

By the end of the year, the Texas Heart Institute could have 23 patients who have reached the 20-year survival milestone. The average heart transplant patient survives eight to 10 years. According to the American Heart Association, the five-year survival rate is 71 percent for men and 67 percent for women.

The risks were even greater when the field of transplant surgery was still evolving two decades ago.

"The real brave ones were the patients," said Dr. Branislav Radovancevic, director of the Center of Cardiac Support and associate director of Cardiovascular Surgery and Transplant Research.

Charles Washington of Oak Ridge, Tenn., was one of those patients.

In 1982, he suffered a massive heart attack, leaving his heart functioning at less than 30 percent of capacity.

"I was literally gasping for air," Washington said. After seven bypasses, Washington's health continued to deteriorate and his prognosis was bleak. Then, on March 27, 1983, Washington received a new heart, and a new appreciation for life.

Now 70, the longest-surviving Texas Heart Institute transplant recipient at nearly 24 years had the chance to watch his children and grandchildren become adults.

"It makes you really enjoy all of life, not just a special occasion," said Washington, who is four years shy of the longest-surviving heart transplant recipient in the U.S., according to the United Network for Organ Sharing in Richmond, Va.

Shortly after the surgery, Washington was attending the annual Oak Ridge dogwood blossom celebration and was taken aback by the sight of the trees in full bloom.

"I looked up, grabbed a leaf and tears came to my eye," Washington said. "I thought about the beauty and tragedy of nature. It reminded me that there was tragedy about the beauty of life. The trees blooms, they die, they come back the next year in full bloom."

"It actually reinforces the approach that we've taken for 20 years, that diabetes without major complications ... does not exclude transplantation," said Dr. W. Steves Ring, chairman of cardiovascular and thoracic surgery at the University of Texas Southwestern in Dallas. Ring, who heads up heart transplant programs at three Dallas area hospitals, was not involved in the study.

While national rules do not prevent diabetics from getting heart transplants, each transplant center has its own rules.

A spokeswoman with the United Network for Organ Sharing, which helps coordinate organ distribution, said the network doesn't know what criteria individual transplant centers use. She said 135 U.S. hospitals offer heart transplants.

Dr. John Buse, president-elect of the American Diabetes Association, said he believes that rules automatically denying heart transplants to diabetics was something that may have been more common in the past.

For the study, published online Monday in the American Heart Association journal Circulation, researchers analyzed UNOS records for survival rates of more than 20,000 people who had heart transplants between 1995 and 2005. That included 3,687 people who were diabetic.

The researchers found that nondiabetics had a median survival rate of 10.1 years, while diabetics had a survival rate of 9.3 years, a difference the study authors said was not statistically significant.

About 21 million Americans suffer from diabetes, mostly Type 2, which is linked to obesity. The disease, which significantly increases the risk for heart disease and stroke, is often associated with other cardiovascular risk factors, including high blood pressure, cholesterol problems and insulin resistance.

And more people are developing heart failure, said one of the study authors, Dr. Mark Russo, a researcher at Columbia University. A transplant is often the only solution for heart failure, when the weakened heart gradually loses its pumping power.

Russo said the study confirms doctors' intuition. While showing that many diabetics do well with a heart transplant, the research also showed that median survival for those with one complicating condition of diabetes fell to under 7 years and for those with two complications, transplant survival was under 4 years.

"Prior to this it was unclear whether diabetes mattered and what it meant if they had complications related to their diabetes," Russo said.

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.

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.

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.

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.EDITOR'S NOTE _ Lauran Neergaard covers health and medical issues for The Associated Press in Washington.__

On the Net:

Info on PFO-and-stroke studies: http://www.closurei.com and http://www.amplatzer.com

Migraine study info: http://www.pfo-migraine.com; http://www.premiumtrial.com; http://www.escapemigraine.com

The disease is the leading cause of death in the United States, killing half a million people every year.

Canola oil and certain foods made with canola oil are allowed to start making the claim, the Food and Drug Administration said Friday.

Labels can say that limited evidence suggests eating 19 grams _ about 1 1/2 tablespoons _ of canola oil daily may reduce the risk of coronary heart disease due to its unsaturated fat content, the FDA said. Canola oil should replace a similar amount of saturated fat and not increase the total number of calories a person eats each day, FDA said.

The U.S. Canola Association, which petitioned FDA for permission to make the claim, said studies show that unsaturated fat from canola oil lowers cholesterol, including LDL or "bad" cholesterol, as part of a diet low in saturated fat.

___

On the Net:

Food and Drug Administration: http://www.fda.gov/

U.S. Canola Association: http://www.uscanola.com