While one randomized trial has shown that IVC filter placement concurrent with full-dose anticoagulation decreases the risk of subsequent pulmonary embolism in the short term, the placement of IVC filters also significantly increases the long-term risk of deep venous thrombosis (20.8% at 2 years with IVC filter placement vs. 11.6% without, and 35.7% vs. 27.5% at 8 years).^5,6 Long-term complications associated with IVC filter placement are particularly important to consider because IVC filter placement has increased dramatically over the last 2 decades.⁷

In recent years, IVC filters that can be subsequently retrieved have been developed. These filters can be left in place during the acute, high-risk phase of developing a pulmonary embolism and can be removed when the indication for filter placement is no longer present. During removal, a catheter is advanced to the site of the filter in the vena cava and attaches to a small hook or knob at the end of the catheter, allowing for retrieval. Manufacturers generally recommend retrieval between 10 and 14 days after placement;⁸ however, one article described retrievable filters with dwell times ranging from 9 to 150 days.³ Single-center retrospective studies examining IVC filter retrieval in medical-surgical patients have shown retrieval attempt rates ranging from 14–45%,^9–12 whereas prospective case series to demonstrate the feasibility of IVC filter retrieval have reported much higher retrieval attempt rates, ranging from 56–99%.^13–18

All available electronic admission notes, discharge summaries, transfer summaries, and radiology procedure notes were reviewed and data collected using a formal chart abstraction tool. Data were collected on patient demographics (age, sex, primary language, and race/ethnicity), clinical comorbid conditions, indication, type and placement of the IVC filter, and finally, whether there was a documented plan to remove the filter. In the subgroup of patients who had retrievable filters placed and who were discharged alive, we reviewed all subsequent UCSF radiology procedure notes to determine whether or not the filter was removed at a later date. In patients who underwent attempted filter retrieval, radiology procedure notes were reviewed to obtain information on retrieval success rates and complications during retrieval.

For patients with retrievable filters who did not undergo filter retrieval, we reviewed the chart to determine whether there were documented contraindications to removing the filter. We considered patients who had contraindications to filter removal as those with limited life expectancy (metastatic cancer, hospice), a contraindication to anticoagulation, or those who were at persistent high risk for pulmonary embolism despite anticoagulation.

IVC filters are not benign clinical interventions. Complications of filter placement include immediate issues such as problems with filter positioning, filter tilting, and technical malfunctions.²¹ In addition, IVC filters increase the risk for later deep venous thrombosis^5,6 as well as rarer complications such as insertion site thrombosis,²² perforation of the inferior vena cava,^22,23 and filter migration to the heart or lungs.^24,25 These complications highlight the importance of ensuring timely removal of filters in appropriate patients.

Our study found that filter retrieval plans were less likely in patients who had a history of cancer and who were not placed on anticoagulants at discharge, a finding that most likely reflects ongoing contraindications to anticoagulation and the need for continued filter retention. However, we also found than 21.6% of patients without plans for filter retrieval had no clear contraindication to retrieval, and that these patients were more likely to be on non-medicine services and be aged 50–69 years. Knowledge of these risk factors could be helpful in developing strategies to improve the rate of appropriate filter retrieval. Although our study was unable to determine the exact reasons for retaining the filter, it is possible that ambiguity as to which service was responsible for the decision on filter removal contributed. Strategies to improve communication between services, such as by designating the service that placed the filter as responsible for follow-up and retrieval²⁶ or by tasking nursing staff to help with follow-up plans²⁷, may clarify role responsibilities and improve plans for filter retrieval. In any case, developing clearer guidelines addressing which patients are appropriate candidates for retrieval and establishing standard lines of responsibility could potentially reduce the rates of inappropriate filter retention. Patients, too, may not always be informed or understand the potential harms of permanent IVC filter placement and should be educated about the importance of appropriate follow-up after filter placement.

In many situations, it may be justifiable to elect not to remove the filter. Such reasons include ongoing contraindications to anticoagulation, large emboli found within the filter or large occlusive thrombus distal to the filter, or poor patient prognosis.¹⁵ The optimal management of these patients in regard to long-term anticoagulation in the presence of an IVC filter is less clear. The proportion of patients in our study undergoing attempted filter retrieval are lower than studies of trauma patients,^28–30 prospective case series to demonstrate IVC filter retrieval feasibility,^13–18 and studies examining medical-surgical patients outside the US.^10–12 However, our rates are comparable to those obtained at another retrospective single-center study of medical-surgical patients at an academic medical center in the US.⁹ Finding thrombus within the IVC filter, the most common complication precluding filter retrieval in our study, has been commonly described in other studies.^{3,10,16,18,23}

There are several limitations to our study. Patients were identified from a single medical center, limiting generalizability. We lacked consistent long-term follow-up, which limited our ability to identify long-term complications. Our reliance on medical chart review may not have completely captured the entire decision-making process around filter placement, nor completely ascertained the contraindications to retrieval. Variation in the amount of information contained in retrospective patient records could have yielded incomplete information on indications for retention.

John F. Mission, Email: john.mission/at/ucsf.edu.

Robert K. Kerlan, Jr., Email: bob.kerlan/at/radiology.ucsf.edu.

Justin H. Tan, Email: justin.tan/at/gmail.com.

Margaret C. Fang, Phone: +1-415-5027100, Fax: +1-415-5142094, Email: mfang/at/medicine.ucsf.edu.