SAN FRANCISCO – Significantly higher rates of complications were observed in patients with indwelling retrievable inferior vena cava filters, compared with those who had permanent filters placed, results from a large single-center study showed.

"Venous thromboembolism is a significant cause of morbidity and mortality," Dr. Tina R. Desai said at the Society for Vascular Surgery Annual Meeting. "The primary treatment for this remains anticoagulation. However, since the initial introduction of the Greenfield filter in 1973, there has been a steady increase in the use of inferior vena cava filters." The introduction of retrievable filters in 2003 further contributed to this increase in use of filters, said Dr. Desai, a vascular surgeon at NorthShore University HealthSystem in Skokie, Ill.

"The retrievable filters were approved to be left in place indefinitely, and they have a theoretical advantage of being able to be retrieved when the patient no longer has a significant risk of pulmonary embolism," she said. "Interestingly, if you look at current-day studies, these retrievable filters are quite uncommonly retrieved. In fact, most of them end up being permanent."

To better understand the difference in complications between retrievable and permanent filters, Dr. Desai and her associates conducted a retrospective study of 1,234 patients who had IVC filters placed at NorthShore between 2005 and 2010. Of the 1,234 patients, 449 had retrievable filters placed while 785 had permanent filters placed.

Patients in the permanent filter group were older than those in the indwelling retrievable group (mean age, 75 vs. 64 years, respectively). They were also sicker, with significantly higher rates of cancer, hypertension, diabetes, and coronary artery disease. "Most of our filters were placed for a diagnosis of acute venous thromboembolism, with a relative minority placed for prophylactic reasons," Dr. Desai said. "All filters were placed by an interventional radiologist or a vascular surgeon. The majority of the retrievable filters were Cook Celect filters, and the majority of permanent filters were Braun Vena Tech filters. For our primary analysis, we defined complications as symptomatic events – either periprocedurally or directly related to the filter – that patients experienced."

Of the 449 retrievable filters placed, 67 of them were electively retrieved. This left a group of 382 indwelling retrievable filters. Dr. Desai reported that the rate of symptomatic complications was significantly higher in the indwelling retrievable filter group than in the permanent filter group (8.9% vs. 2.9%; P = .0001). Thrombotic complications were the most common type of symptomatic complication in both groups. They occurred more often in the retrievable filter group than in the permanent filter group (4.2% vs. 1.8%), but this difference did not reach significance.

The researchers did find a statistically significant difference in the number of device-related symptomatic complications that occurred in the indwelling retrievable filter group, compared with the permanent filter group (2.6% vs. 0.5%; P = .006). The number of systemic-related symptomatic complications was higher in the indwelling retrievable filter group than in the permanent filter group (1.3% vs. 0.4%), but this difference did not reach significance.

"In addition to the complications that we saw, we found a number of patient findings such as those shown on CT scan, which shows perforation of filter struts through the wall of the vena cava," Dr. Desai noted. "Others have made similar observations. While we don’t completely understand the significance of these symptomatic findings, it’s hard to ignore these effects when we’re trying to make decisions about whether we should be leaving these retrievable filters in place indefinitely or not."

When the researchers factored both incidental and symptomatic findings into their analysis, the rate of device-related complications was 8.9% in the indwelling retrievable filter group, compared with 0.9% in the permanent filter group, a difference that reached significance (P less than .0001).

With these findings in mind, Dr. Desai recommended that retrievable filters "only be used in conditions where retrieval is highly likely; in all other patients, permanent filters should be used when IVC filters are indicated."

She acknowledged certain limitations of the study, including the fact that its retrospective design "likely results in an underestimation of the number of asymptomatic complications," she said. "Also, we cannot draw meaningful conclusions related to the effects of anticoagulation on thrombotic complications. Organized programs to track and follow patients who receive retrievable filters are necessary to optimize retrieval rates. Further study is needed to determine the significance of asymptomatic device fracture and device penetration through the IVC."

Dr. Desai said that she had no relevant financial conflicts to disclose.

dbrunk@frontlinemedcom.com

More complications seen in retrievable vs. permanent IVC filters