What Are Some Examples of IVC Filters?

Temporary IVC Filters

Celect (Cook Medical, Bloomington, IN, USA)

This is a newer design that is based on the Günther Tulip filter and designed to be more easily retrievable. It is made of Conichrome® which is a cobalt- chromium-nickel-molybdenum-iron alloy. It has a single-cone design and incorporates secondary struts, designed to centerre the filter at deployment and throughout its duration of use.

Günther Tulip (Cook Medical, Bloomington, IN, USA)

The predecessor to the Celect, it was approved for use in Europe in 1992. It consists of 4 legs, each 44mm in length, and has 12 filter wires in total. It is also made of Conichrome® and has similar insertion requirements to the Celect. No limit on the retrieval window has been set. A retrieval success rate of 94% at 12 weeks was identified in a recent study.

G2 / Denal (Bard Peripheral Vascular, Tempe, AZ, USA)

This nitinol (nickel-titanium alloy) filter has a conical shape with 6 legs and 6 filter wires arranged in 2 offset layers. It has elastic fixation hooks designed to allow easier removal. Maximum caval diameter for insertion is 28mm and it requires a 7F sheath. One study found a 95% retrieval success rate, with median indwell time of 144 days and the longest indwell time of 300 days. FDA approved for permanent use in 2005 and for retrievable use in 2008.

OptEase (Cordis, Miami Lakes, FL, USA)

This nitinol hypotube filter is a modified version of the permanent TrapEase filter. It has a double-basket design for dual-level filtration and has side struts with unidirectional fixation barbs to protect against cephalad migration. It can be inserted via jugular, femoral or antecubital approaches but has a hook at the caudal end only and therefore may be retrieved only by a femoral approach. However this can be useful where the jugular veins are thrombosed. Maximum caval diameter for insertion is 30mm. It requires a relatively small 6F introducer system. A 2009 study found a retrieval success rate of 93% but with a mean interval of 11 days. Some studies have suggested a higher rate of IVC thrombosis due to the double-basket design; overall rates range from 0 to 12.5%. The retrieval window as indicated by the manufacturer is relatively short at 23 days. FDA approved for permanent use in 2002 and retrievable use in 2004.

ALN filter (ALN Implants Chirurgicaux, Ghisonaccia, France)

This filter is made from 316L stainless steel alloy that is nonferromagnetic and is MR compatible. It has a dual level arrangement with 6 short hooked legs to ensure fixation to the caval wall and 3 longer legs for centering. There is no recommendation from the manufacturer regarding retrieval window; the longest documented retrieval interval is 25 months. A 2008 study recorded a retrieval success rate of 99% after a mean interval of 93 days. FDA approved for permanent and retrievable use in 2008. CE marked.

Option (Rex Medical, distributed by Argon Medical Devices)

This is a newer design, laser cut from a single piece of nitinol for greater strength. It has a conical shape with 6 struts and a caudal hook. It is inserted via a 5F system, the smallest on the market. Maximum caval diameter is 32mm. A 2010 study recorded a retrieval success rate of 92% with mean interval of 67 days.

Crux filter (Crux Biomedical, Menlo Park, CA, USA)

This has a novel design with two nitinol spiral elements crimped at the ends to form a symmetric double-looped helical structure. A filter mesh designed to capture clots is attached to one loop. Three fixation anchors are crimped to the opposite loop, two of which are located at the loop midpoints and the third at the tail end. Each end has a retrieval element for capture by a snare via jugular or femoral access. The symmetrical design is intended to self-centerre the filter.

Permanent Filters

Titanium Greenfield (Boston Scientific, Natick, MA, USA)

This is a conical filter descended from the original Kimray-Greenfield filter. It has 6 struts, each with a curved hook. It is made of beta III titanium alloy with elastic properties but still requires a relatively large 12F system for insertion. Initial studies identified an unacceptable 30% rate of tilting, penetration and migration. This led to a modification of the hooks to reduce penetration. There are good long- term patency rates with low rates of thrombosis. The Greenfield designs are regarded as the standard IVC filters because of their long track record. FDA approved in 1989. CE marked.

TRAPEASE (Cordis, Miami Lakes, FL, USA)

This has a similar design to the OptEase described above. One difference is the provision of proximal and distal hooks designed to prevent migration in either the caudal or cephalad directions.

Gianturco-Roehm Bird’s Nest (Cook Medical, Bloomington, IN, USA)

This has a unique design with two V-shaped struts supporting a random tangle of very fine wires. This is the only filter that can be used in megacavas (up to 40mm diameter).

Simon Nitinol Filter

VenaTechFilter

What Are The Risks of IVC Filter Removal?

IVC filter removal is generally regarded as a safe procedure that can be performed using minimally invasive techniques on an outpatient basis.

As with any endovascular procedure, filter retrieval imparts a risk of bleeding. This may occur from the incision (which typically ranges from 3-5mm) or from adherence of the filter components to the inferior vena cava. Significant bleeding from IVC filter removal is a rare phenomenon and is typically treated with mechanical pressure on the site of bleeding (either with manual compression or angioplasty balloon tamponade).

IVC filters may be fractured during retrieval, and fractured components may migrate to the chest. Fracture is usually the result of mechanical fatigue of the filter components, often seen in the setting of prolonged dwell times. For this reason, a detailed conversation regarding the risks of removing filters with prolonged dwell times is necessary. It should be emphasized that continuing to keep an IVC filter in place also may result in filter fracture and the risk-benefit of retrieval in these patients is not well known. Thus, these cases are determined on a case-by-case basis.

As previously discussed, filter struts may penetrate the IVC and enter structures such as the small intestines (common), bone (rare), and arteries (rare). In such cases, removal of the IVC filter imparts a small risk of damaging these structures. Again, the specific risks of filter removal in situations such as these must be considered on a case-by-case basis.

Is It Possible to Remove a "Permanent" IVC Filter?

Yes, permanent IVC filters are commonly removed. Permanent IVC filters are distinguished from their removable counterparts by absence of a retrieval hook. Many permanent filters are otherwise very similar in design and can be removed using the comparable techniques used in removal of temporary ones. 

Just because a “permanent” IVC filter is placed, doesn’t necessarily mean that the filter has to stay in place forever. Many physicians choose to place permanent IVC filters, making the assumption that they carry an improved safety profile relative to removable filters. The Greenfield filter is an example of a common permanent IVC filter that has been used for decades. Some permanent IVC filters have been associated with decreased rates of long-term complications relative to retrievable filters. However, fracture, blood clot formation, and penetration of the IVC are seen with relative frequency with many of these permanent devices.

Removal of permanent IVC filters is distinguished from temporary filters in that they are not explicitly addressed in the 2010 FDA statement regarding IVC filter removal. In clinical practice, removal of permanent filters depends on several factors, including patient age, dwell time, and ongoing need for the IVC filter.

Figure: An example of a "permanent" Greenfield filter that was removed after nearly 4 years dwell time

How Long Can I Wait After Placement to Have My IVC Filter Removed?

The length of time an IVC filter stays in place after implantation is referred to as dwell time.

There is no dwell time that prohibits IVC filter removal. However, it is true that a longer dwell time could increase the complexity of IVC filter retrieval and increase the likelihood of unsuccessful retrieval. For this reason, most physicians recommend consultation for IVC removal at the earliest possible time interval after it is no longer needed. This is ideally within 3-6 months of placement. Prolonged dwell times exceeding 1 year do not prohibit removal. However, this should warrant a detailed conversation with the interventionalist regarding benefits of removal and possible risks.

Should I Have My IVC Filter Removed?

The answer to this question is complex and depends on a number of factors, including but not limited to: ongoing need for the filter, date of placement, type of IVC filter, presence of symptoms or imaging findings that may warrant removal. It is important to understand the potential risks of both keeping and removing an IVC filter. The rationale for IVC filter removal is provided below:


IVC filters may migrate or break over time

The inferior vena cava is a dynamic structure that expands and contracts with each heartbeat. While most IVC filters have superb design and engineering, the cumulative stress on the metal components of a filter over years of dwell time can cause components to break, rendering the filter less effective or causing it to migrate. IVC filters that migrate to the heart can result in significant health risks including arrhythmia and need for open cardiac surgery. From 2005 to 2014, nearly one thousand IVC filter complications were reported to the FDA. Of these, 328 involved device migration, 146 involved embolizations (detachment of device components), and 56 involved filter fracture. While this number of reported complications is significant, it is likely that the extent of IVC filter-related problems greatly exceeds those reported to the FDA. This led to the FDA to release a recommendation in 2010 that reads: “The FDA recommends that implanting physicians and clinicians responsible for the ongoing care of patients with retrievable IVC filters consider removing the filter as soon as protection from PE is no longer needed.” The full FDA safety communication statement can be viewed http://www.fda.gov/MedicalDevices/Safety/AlertsandNotices/ucm221676.htm.


IVC Filter Components May Penetrate the IVC and Cause Symptoms

IVC filters are designed with radial force, meaning the struts of the filter place an outward force on the wall of the inferior vena cava. Radial force is one important aspect ofif IVC filter design that allows the collapsed IVC filter to open and adhere to the IVC wall after deployment from a vascular sheath. Radial force is necessary to minimize filter migration and allows deployment from relatively small vascular sheaths, but carries an important downside. The constant outward force on the IVC can result in perforation of the filter strut beyond the wall of the IVC. This is a very common phenomenon, occurring on 79% of patients in one study[AB1] . Although strut perforation is common, in some patients the IVC filter strut may touch or enter an adjacent structure such as the aorta, small intestines, or spine. A perforated IVC filter strut has potential to damage or irritate any of these adjacent structures and cause pain.

For more information regarding strut perforation, please view an article published in the Journal of Vascular and Interventional Radiology: http://www.jvir.org/article/S1051-0443(15)00594-1/pdf.


IVC Filters May Cause Formation of Additional Blood Clots
Although IVC filters are designed to mitigate the negative impact of blood clot formation, there is emerging evidence that indwelling IVC filters are associated with very high rates of deep venous thrombosis. The exact mechanism by which this happens is not totally clear, however there are two likely factors that contribute: 1) An indwelling IVC filter creates turbulent blood flow in the IVC and 2) the body’s reaction to an IVC filter results in narrowing of the IVC in and around the filter. It is likely that one or both of the factors lead to more stagnant blood return from the legs, increasing the likelihood of deep venous thrombosis. This occurs in an estimated 13% of patients (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4736520/).


Long term, large-burden of DVT predisposes patients for post thrombotic syndrome (PTS), a debilitating disease where circulation to and form the legs is reduced. PTS is associated with chronic leg pain, skin ulcerations, and in extreme cases may contribute to gangrene.

Figure 3 – An example of a patient with leg ulcers related to post thrombotic syndrome 

[AB1]http://www.ncbi.nlm.nih.gov/pubmed/26233837

How is an IVC Filter Removed?

The process of removing an IVC filter begins with a clinical consultation with an interventional radiologist who specializes in IVC filter removal. A number of factors are reviewed including the reason for IVC filter placement, currently blood thinner medication, the type of filter placed (if known), the dwell time of the IVC filter, and other pertinent aspects of the medical history. This is important to ensure that there is no ongoing need for the IVC filter and to evaluate the likelihood of successful retrieval.

In patients deemed eligible, the IVC filter may be removed in a fashion that mimics filter placement. Retrievable filters have a hook at one or both ends and a collapsible design. Through a small incision just above the clavicle, the venous system is accessed and a looped wire is used to grab the hook – this wire appears similar to a small lasso. Once the hook is secured, a hollow plastic tube called a vascular sheath is advanced over the IVC filter which collapses inside the sheath. The IVC filter and sheath are removed and a small bandage is applied to the incision.

In a certain proportion of patients, this conventional technique fails to successfully remove the IVC filter. Conventional methods typically fail as a result of tissue growth around the hook of the IVC filter, the body’s natural response to a foreign object. When this occurs, a number of “advanced techniques” can be used to secure the filter including various wires and catheters, and small grasping forceps. Forceps are particularly useful, and have been associated with high rates of retrieval success. This is detailed in a manuscript published in the Journal of Vascular and Interventional Radiology: http://www.jvir.org/article/S1051-0443(16)30025-2/abstract.

Procedural time for IVC filter removal is rarely greater than 1 hour, and the majority that can be removed with conventional techniques take less than 15 minutes. Procedures may be performed under either sedation or general anesthesia depending on the type of filter, medical comorbidities and patient preference. Patients typically must fast at least 6 hours prior to the procedure and are observed for 2 hours after successful IVC filter removal.

Figure 2 – Artist rendition of a filter retrieval. From http://circinterventions.ahajournals.org/content/6/5/560 

What Is An IVC Filter?

An IVC filter is a small metal basket that is typically implanted in the largest vein in the abdomen, the inferior vena cava (IVC). Once in place, an IVC filter functions to “trap” blood clots that may form in the legs and travel to the lungs.

A majority of blood clots form in the deep veins of the legs - a condition known as deep venous thrombosis, or DVT. This is usually a result of prolonged immobility, although prior surgery, dehydration, pregnancy, and various genetic conditions can contribute. DVT is usually accompanied by leg pain and swelling and can result in long-term damage to the structure of the leg veins. However, it is not typically a life-threatening condition.

If a blood clot dislodges from the leg veins and travels to the lungs, it may compromise the ability of the lungs to transfer oxygen into the blood or make it difficult for the heart to pump blood to the lungs. This is known as a pulmonary embolus (PE), and is the source of an estimated 100,000 deaths in the US each year. In order to reduce the considerable mortality risk associated with PE, IVC filters are often placed as a preventative measure in patients.

There are three common scenarios in which IVC filters are usually placed: 1) Patients with known DVT to prevent development of PE 2) Patients who already have PE, to prevent worsening condition from additional PE 3) In patients with no known history of DVT or PE but who will undergo a surgery that imparts a high risk of developing DVT. Orthopedic hip surgeries and pelvic GYN surgeries are common examples.

IVC filters are designed for deployment via the jugular vein in the neck or the femoral vein in the leg. This procedure is described in detail in the following video illustration: https://vimeo.com/18934756.

While IVC filter design varies among manufacturers, each contains an expandable metal structure that can be delivered into the IVC via a small-bore hollow delivery sheath (see figure 1 below). The metallic construct of the filter permits blood flow through the IVC while inhibiting the flow of sizeable blood clots from veins in the legs to the lungs.

Figure 1 – IVC filter artist rendition. From http://sdmi-lv.com/services/ivc-filter-placement/