These filters trap blood clots. But for most patients, they are not a good idea, Temple study says

In patients with blood clots in the veins of their legs — a debilitating condition called deep-vein thrombosis — physicians sometimes implant miniature filters to prevent the clots from migrating to the lungs.

But the devices can break and perforate blood vessels, and there is little evidence they save lives, leading some medical societies to conclude they are not worth the risk.

Yet there is some question whether the clot-trapping filters might be a sound approach for a subset of patients who undergo an additional procedure in which physicians use a catheter to deliver clot-busting drugs directly to a clot in the legs.

The answer, according to a new study led by a Temple University cardiologist, is still no.

In a group of more than 7,000 patients who underwent the catheter procedure, those who also had a filter implanted were no more likely to survive their hospital visit than those who did not get a filter, the authors reported this week in the journal JACC Cardiovascular Interventions.

What's more, patients who received the filters were more likely to suffer a hematoma — an abnormal mass of partly clotted blood. And they stayed in the hospital longer, running up a bigger bill. Average hospital charges were $104,000 for those who got the filters vs. $93,000 for those who did not.

The filters are small, basket-like devices made of wire, placed in a vein in the abdomen called the inferior vena cava.

In general, physicians should avoid using the devices in patients with deep-vein thrombosis, unless they cannot tolerate the standard treatment with blood-thinning medicines, said senior author Riyaz Bashir, a professor at Temple's Katz School of Medicine.

> > READ MORE: Five lessons from the death of Maroon 5 manager Jordan Feldstein

"If somebody is able to take blood-thinning medicine, there is no reason to put a filter in," said Bashir, director of vascular and endovascular medicine at Temple University Hospital.

One limitation of the study was that patients were not randomly chosen to receive a filter, meaning that authors could not rule out other factors that might determine how well the devices functioned. Still, the research suggests that the filters are inappropriate in most cases, according to McMaster University physicians Mark Crowther and Andrea Cervi, who wrote an editorial that accompanied the study.

"The authors are to be congratulated on this study, which provides a sobering counterpoint to the high frequency of IVC filter use," Crowther and Cervi wrote.

Deep-vein thrombosis leads to 600,000 hospital visits a year in the United States. When a clot breaks loose and travels to the lungs, it is called a pulmonary embolism — a dangerous condition that was blamed in the December 2017 death of Jordan Feldstein, manager of the group Maroon 5.

Symptoms of deep-vein thrombosis can include aching, throbbing, and swelling in the legs. It is more common in older people, though Feldstein was just 40. Other risk factors include obesity and cigarette smoking.