Venous thromboebolism, or VTE, is a serious medical condition. In it, a blood clot forms deep inside the veins found within the arms, pelvis or leg. This clot can travel up to the lungs or heart. Those blood clots that form and stay within the deepest veins of the pelvis and upper and lower extremities are known as deep venous thromboses, or DVTs. A DVT on its own is not a life threatening condition. However, if it travels to the lungs, it can become a pulmonary embolism, or PE, and that can be deadly as it stops normal blood flow from reaching the lungs.

Treatment for DVTs and PEs

When someone presents with a DVT or PE, the first step is to make sure no more blood clots form and to stop the ones that are already there from becoming larger. This is initially done by prescribing anti-coagulation medication, known as blood thinners. However, not every patient is able to take this type of medication. For instance, someone who has just had surgery can often not be prescribed this type of treatment.

If someone is unable to take anti-coagulation medication, or if it does not resolve the issue, they may be prescribed an inferior vena vaca, or IVC, filter. IVC filters are also often prescribed to those patients who have had recurrent PEs or blood clots, even if the therapy they have received should have been successful.

As such, an IVC filter is usually prescribed if:

• Someone has a recurrent VTE, even if they have been treated with anti-coagulation medication.
• Someone who cannot take anticoagulants due to recent surgery, bleeding, trauma or allergies and adverse reactions to these types of drugs.

What Is an IVC Filter?

IVC filters are small devices that look like a metal cage. They have been designed to prevent a blood clot from going up to the lungs. The IVC filter is placed within the inferior vena cava, which is the largest vein in the human body and is responsible for carrying blood to the heart. Usually, it is inserted just underneath the kidneys by using a catheter deployment device.

An interventional cardiologist, interventional radiologist or vascular surgeon will usually perform this procedure. The procedure is done under local anesthetic, with some medication to help patients relax. The insertion site is numbed and a small incision is then made. This is usually in the groin or in the neck. Naturally, patients are monitored throughout the procedure. Once the incision is made, a catheter is then inserted into the large vein. This will help the surgeon to guide the filter into the correct position within the vena cava. They will use x-ray guidance to find the best placement. Before the filter is deployed, the vena cava will be imaged and sized. Once the filter is in place, the catheter is removed and the incision site is bandaged up. Activity should only be limited for a short period of time if the insertion site is in the groin, but most procedures are completed on an outpatient basis.

Two types of IVC filters exist, which are the permanent and the retrievable models. The decision in terms of which one to use must be made by a physician. Usually, they will look at particular risk factors, whether or not you can take anticoagulants and how long you will be at risk of developing further clots. It is important to understand that having an IVC filter in place does not stop a new clot from forming. In most cases, patients will also be prescribed blood thinning medication.

IVC Filter Removal

Removable filters should be retrieved as soon as a physician believes that a patient is no longer at significant risk from a DVT or VTE. The FDA’s official recommendation is that the filter is removed between 29 and 54 days after implantation, so long as protection from PE is no longer required. Unfortunately, however, it appears that this does not happen. In fact, in a recent study, it was found that out of 679 retrievable IVC filters, only 58 had been taken out. Additionally, 13 unsuccessful removal attempts were made. These were unsuccessful because:

• The devices became embedded in 8 different patients.
• The devices protruded through the veins of 3 different patients.
• The devices migrated to an abnormal position with 2 patients.
• A blood clot was located inside the filter with 1 patient.

How Is an IVC Filter Removed?

The removal of an IVC filter is similar to its insertion. First, an x-ray dye or contrast is injected around the site of the filter. This will ensure that there are no blood clots underneath the filter, indicating that the removal can go ahead. A snare inside a catheter will then be guided to the hook that is found at the top of the filter. The filter is then enveloped in a sheath and taken out of the body.

PRESERVE Study

The FDA commissioned the Predicting the Safety and Effectiveness of Inferior Vena Cava Filters (PRESERVE) study as a result of the fact that so many negative reports were received in terms of not just the usage but also the removal of IVC filters. In fact, some manufacturers of these fillers are facing individual and class action lawsuits because of it. The PRESERVE study aims to identify the inherent dangers with IVC fillers and why so many adverse reports have been noted. It is also looking into best practices in terms of filter removal.

Additional Resources:

• Eight-year follow-up of patients with permanent vena cava filters in the prevention of pulmonary embolism: the PREPIC (Prevention du Risque d’Embolie Pulmonaire par Interruption Cave) randomized study.Eight-year follow-up of patients with permanent vena cava filters in the prevention of pulmonary embolism: the PREPIC (Prevention du Risque d’Embolie Pulmonaire par Interruption Cave) randomized study.
• Inferior Vena Cava Filter Placement and Removal
• Removing Retrievable Inferior Vena Cava Filters: FDA Safety Communication
• Predicting the Safety and Effectiveness of Inferior Vena Cava Filters (PRESERVE) study