乌鸦传媒

CHICAGO -- A clinic dedicated to inferior vena cava (IVC) filter management appears to boost safe use, according to one center's experience.

The filter retrieval rate jumped from 29% to 62% after establishing such a clinic (P<0.001) at Northwestern University in Chicago, Ramona Gupta, MD, and colleagues there found.

The clinic lost fewer patients to follow-up and extended duration of filter use, the group reported at the Society of Interventional Radiology meeting.

Taken together -- the higher patient retention and longer filter use -- maximized the filter's availability to fight thromboembolic risk during the high risk period while at the same time reducing possible complications by prompt removal once that period is over, she suggested.

Centers all across the country are starting up similar clinics, and they have the potential to see the same good results, commented session moderator William Kuo, MD, of Stanford University in Palo Alto, Calif.

The growth in the number of clinics is a tacit recognition that follow-up of patients in whom filters were inserted was overlooked in the past, noted John A. Kaufman, MD, of the Oregon Health & Science University Hospital in Portland, who likewise was not involved in the study but called it important.

The FDA also recognized the problem with a warning last August that these retrievable filters -- implanted to prevent pulmonary emboli and other thromboembolic events -- have caused hundreds of cases of device migration, perforation, embolization stemming from the filter, and filter fracture.

The agency recommended removing the IVC filter as soon as the pulmonary embolism risk subsides, since fracture and migration risks appear to increase the longer the filter remains in the body.

"These patients are in some sense orphans," Kaufman said. "They come from many different practitioners, they have many different medical problems, they come through to get their filter and they go back to all these different practitioners who may not have a good sense of how to follow these filters and when they should come out."

That was the case at Northwestern before it instituted a filter clinic in January 2009, as there had been no routine coordinated follow-up for these patients, Gupta explained.

Typically referring physicians delay contacting interventional radiologists until "their patients were candidates for retrieval," she told attendees at the session.

By contrast, the clinic employed dedicated interventional radiologists and a dedicated clinical nurse coordinator, who did most of the leg work phoning patients and keeping track of them in a comprehensive database, Gupta noted.

The clinic contacted referring physicians and patients two weeks after filter placement and the correspondence continued until the filter was removed or converted to permanent status as a result of a clinical decision.

Only 0.6% of the 165 IVC filter patients seen in 2009 after the clinic was established were lost to follow-up compared with 10% of the 369 with IVC filters placed from 2000 to 2008 before the clinic (P<0.0001).

The duration of implantation rose from 0.55 to 1.13 months between the two periods as well (P<0.001), which Gupta suggested maximized the benefit of the device.

Not all patients need their filter removed if close follow-up suggests continued embolic risk or no need for removal, such as when used in a cancer patient who becomes terminal, Kaufman noted, calling the 62% rate of retrieval achieved by the clinic "about right."

The increase in filter retrievals didn't appear to be related to technical failures and was against a backdrop of rates in the pre-clinic period that weren't out of the ordinary compared with historic controls.

The researchers did, however, caution that their data were limited and based on retrospective review.