CHICAGO (AP) -- Medical filters that stop blood clots from reaching the lungs can move or break and cause life-threatening problems for patients, the government and a medical journal report said Monday.

In an advisory to doctors and patients, the Food and Drug Administration said it has received more than 900 reports about problems with these filters since 2005. Problems can arise when filters are left inside veins too long. The devices can shift, and pieces can break off, drift through the bloodstream and perforate vital organs including the heart, according to adverse event reports on FDA's Web site.

The filters are inserted inside a large abdominal vein, and have spidery metal legs to stop blot clots from traveling to the lungs. Some are permanent but many are for short-term use and are removable.

The FDA says doctors should consider removing filters if a patient's risk of clots subsides.

"It's thought that too many retrievable filters stay in permanently because patients are lost to follow-up," or doctors don't know problems can occur when the devices are left in long-term, the FDA's Dr. Bram Zuckerman said in a phone interview Monday. He is director of FDA's Center for Devices and Radiological Health's Division of Cardiovascular Devices.

Zuckerman said doctors and patients with filters should discuss whether removal is an option.

There have been no recalls. But the FDA said it will issue a final statement, which could range from another advisory to a device recall, when it completes an analysis of data on filter problems.

Blood clots affect more than 200,000 people nationwide each year and are usually treated with blood-thinning drugs. Implanted filters are an alternative for people who can't take these drugs or who develop clots despite medication.

About 30,000 filters are implanted each year. Several brands are sold and Zuckerman said problems have been seen with all retrievable filters. Some reports to the FDA involve patients who died but Zuckerman said blood clot patients often are very sick to begin with so it's unknown if filters played a role in any deaths.

A report about one maker's devices used at a Pennsylvania hospital appeared online Monday in Archives of Internal Medicine.

The report involved 80 patients at York Hospital in York, Pa. who received filters made by a division of C.R. Bard, Inc., a New Jersey-based medical device maker.

Overall, 16 percent of the patients had a filter break. Among patients who had an older version, 25 percent had a filter break and drift away -- an "astounding" rate, Dr. Rita Redberg, the journal's editor, said in a published commentary.

Redberg said York Hospital's breakage rate suggests that more than 7,000 U.S. patients may have fractured filters. Zuckerman said York's rate seems high and may not be nationally representative.

In a statement, Bard said filters "have protected the lives of thousands of patients who otherwise would have had limited treatment options or may have suffered severe complications."

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