These devices can be either removed (retrievable filters) or altered in some way to no longer function as a filter while remaining in the IVC (convertible filters), although the latter are not yet commercially available. The retrieval of a filter is accomplished during a second percutaneous procedure through either a jugular or femoral venous access, using a snaring or other retrieval device. Left in place, optional filters function as permanent filters. These devices are considered distinct from temporary filters, which are tethered by an intravascular catheter or guidewire, are sometimes externalised though a venous access site and must be removed within a specified timeframe.

Retrievable IVC filters for short-term caval interruption are being utilised with increasing frequency. The availability of retrievable IVC filters has contributed to the progressive relaxation of the indications for filter placement. These changes in clinical practice are occurring in the absence of prospective, randomised trials confirming an actual benefit of removal of VC filters. In response to this lack of information, a multidisciplinary consensus panel has developed guidelines for the use of optional IVC filters. The members of the group were drawn from interventional radiology, trauma and vascular surgery and internal medicine (see Panel Members at the end of the article).
The goal of the group was to produce a guidelines document for all physicians using optional VC filters. The discussion focused on optional filters (retrievable or convertible) as a general class of devices, rather than on specific filters. The panel addressed the indications for placement of optional filters, recommending follow-up while filters are in place, the evaluation of patients before discontinuation of filtration and the management of patients after the procedure. The final document was published in March 2006.¹

Why the Interest in Optional Filters?
The first-line treatment and prevention of venous thromboembolism (VTE) remains pharmacological with anticoagulation.² When a patient is at high risk of PE and anticoagulants are contraindicated or have failed, an IVC filter is usually placed. Filters do not treat established PE or deep vein thrombosis (DVT), nor do they prevent the development of new VTE. However, permanent VC filters are strongly believed to increase the longterm risk of DVT without reducing the overall mortality from VTE.³,⁴ Despite over 40 years of clinical experience, the role of permanent filters in patients with VTE remains a controversial area.^2,5,6

There are many risk factors for VTE and some, such as trauma or surgery, are transient.⁷ Along similar lines, the contraindication of anticoagulation in patients with, or at risk of, VTE may also be temporary. It seems reasonable that patients transiently at high risk of clinically significant PE and/or with transient contraindications of anticoagulation may not require permanent caval interruption. This reasoning, based on extrapolation from admittedly deficient data, is, in part, driving the use of optional VC filters.⁸

What Are the Indications for Optional Filters?
All optional filters are approved for permanent implantation. Optional and permanent filters, as two classes of devices, perform with similar efficacy and safety profiles.⁹ In clinical practice, many optional filters often become permanent as a result of changes in the patient’s clinical status, loss of patient to follow-up or inability to technically retrieve the device. No retrievable filter can be placed with an absolute certainty of removal. For this reason, the existing indications for permanent filters are wholly applicable to retrievable filters (see Table 1). There are no newly identified patient populations for whom permanent filters are absolutely contraindicated and optional filters are indicated.

Table 1: Indications and Contraindications for AllVena Cava Filters

VTE = venous thromboembolism, e.g. deep vein thrombosis (DVT) and/or pulmonaryembolism (PE); AC = anticoagulation; * = primary prophylaxis not feasible due tohigh bleeding risk, inability to monitor the patient for VTE, etc.