AVI SERVICES

IVC Filters

Guidelines for the Use of Retrievable and Convertible Vena Cava Filters: Report from Society of Interventional Radiology Multidisciplinary Consensus Conference

Between 350,000 and 600,000 people each year in this country are affected by blood clots and between 100,000 and 180,000 people die of pulmonary embolism each year.

IVC filters are a treatment option for those individuals who can’t take bloodthinning drugs or who develop clots despite medication and remain at risk for pulmonary embolism. Some types of IVC filters, called “retrievable IVC filters” can later be removed by an interventional radiologist.

Removable vena cava filters for temporary protection from pulmonary embolism (PE) were first proposed in 1967. In 2003 and 2004, the United States Food and Drug Administration approved changes to the instructions for use of three existing permanent filters to allow percutaneous retrieval.

Indications for Placement of Optional Vena Cava Filters

Venous Thromboembolism
There are numerous risk factors for venous thromboembolism (VTE), including malignancy, thrombophilias, recent major surgery or trauma, increased age, acute major medical illness, previous VTE, and morbid obesity. Some of these risk factors are transient, such as major surgery and trauma, whereas others are permanent and may even increase in importance over time. Careful evaluation of each patient for the presence of risk and duration of the period at risk for VTE is important when selecting a prevention or treatment strategy.

The primary means of prevention and therapy of VTE is pharmacologic, such as systemic administration of anticoagulant agents. Anticoagulant therapy usually entails an acceptably small risk of bleeding and other complications.
Role of Vena Cava Filters in Treatment and Prophylaxis of VTE

The sole function of vena cava filters is to prevent clinically significant PE by trapping venous emboli. Vena cava filters do not prevent or treat venous thrombosis. In general, the use of vena cava filters is indicated when primary therapy cannot be started, must be stopped, or is insufficient to protect patients from clinically significant PE who are at high risk. When used in patients at risk of developing VTE but who do not yet have it, the purpose of the filter is to prevent clinically significant PE should deep vein thrombosis (DVT) occur. Filters placed for so-called prophylactic indications do not provide prophylaxis for development of DVT.
Indications for Optional Filters

In general, indications for all vena cava filters have been divided into absolute, relative, and prophylactic categories.
Management of Patients with an optional Vena Cava Filter

Patients with optional vena cava filters require tracking and routine follow-up for several reasons. The window of retrievability varies for each device, patient conditions may change such that discontinuation of the filter is no longer desired or safe, and primary physicians may require guidance on the timing of filter discontinuation. Preferably, the physician who places the filter should perform this follow-up.

Patients with VTE and a vena cava filter should undergo primary therapy at the first safe opportunity regardless of the presence of a vena cava filter.
When to Consider Discontinuation of Vena Cava Filtration

Specific Recommendations for Patients with VTE
Several studies suggest that symptomatic PE is most likely to occur within 2-3 weeks of the initial episode of VTE. The duration of highest risk for clinically significant PE during primary therapy should be estimated individually for each patient.

Specific Recommendations for Patients without VTE
Patients in whom filters are placed for prophylaxis should be treated with primary prophylaxis as soon as possible according to published guidelines.
Patient Evaluation Before Discontinuation of Filtration

Procedural Evaluation
Patients suspected of having new, recurrent, or progressive VTE on the basis of symptoms or clinical findings should undergo diagnostic imaging procedures to resolve this question before proceeding. Routine coagulation measurements and complete blood counts are appropriate for the assessment of patients receiving therapeutic anticoagulation. Renal function assessment should be considered in patients at risk for contrast agent nephropathy.

Patients without a known diagnosis of VTE should undergo imaging of the lowerextremity veins such as duplex venous US before discontinuation of filtration. A finding of DVT in these patients requires postponement of filter discontinuation and initiation of primary therapy if not contraindicated.

Patients should be seen in clinic by an Interventional Radiologist to evaluate for filter removal.
What is Inferior Vena Cava Filter Placement and Removal?

In an inferior vena cava filter placement procedure, interventional radiologists use image guidance to place a filter in the inferior vena cava (IVC), the large vein in the abdomen that returns blood from the lower body to the heart.

Blood clots that develop in the veins of the leg or pelvis, a condition called deep vein thrombosis (DVT), occasionally break up and large pieces of the clot can travel to the lungs. An IVC filter traps large clot fragments and prevents them from traveling through the vena cava vein to the heart and lungs, where they could cause severe complications or even death.

Until recently, IVC filters were available only as permanently implanted devices. Newer filters, called optional retrievable filters, may be left in place permanently or have the option to be removed from the blood vessel later. This removal may be performed when the risk of clot traveling to the lung has passed. Removal of an IVC filter eliminates any long term risks of having the filter in place. It does not address the cause of the deep vein thrombosis or coagulation. Your referring physician will determine if blood thinners are still necessary.
How does the procedure work?

Using image guidance, a catheter is inserted through the skin into a blood vessel in the neck or groin and advanced to the inferior vena cava in the abdomen. The IVC filter is then placed through the catheter and into the vein where it will attach itself to the walls of the blood vessel.

To remove an IVC filter, a special catheter is advanced to the site of the filter in the inferior vena cava. A removable IVC filter has a small hook or knob at one end that enables the catheter to take hold of and withdraw it from the body.
How is the procedure performed?

Image-guided, minimally invasive procedures such as inferior vena cava filter placement and removal are most often performed by a specially trained interventional radiologist in an interventional radiology suite.

This procedure is often done on an outpatient basis. However, some procedures may require admission. Please consult with your physician.

You will be positioned on your back.

You will be connected to monitors that track your heart rate, blood pressure and pulse during the procedure.

A nurse or technologist will insert an intravenous (IV) line into a vein in your hand or arm so that sedative medication can be given intravenously. You may also receive general anesthesia.

Your physician will numb the area with a local anesthetic.

The area of your body where the catheter is to be inserted will be shaved, sterilized and covered with a surgical drape.

A very small nick is made in the skin at the site.

Using image-guidance, a catheter (a long, thin, hollow plastic tube) is inserted through the skin into a blood vessel and maneuvered to the treatment site.

A contrast material may be injected into the inferior vena cava to help guide the catheter and verify the placement of the IVC filter in the blood vessel.

At the end of the procedure, the catheter will be removed and pressure will be applied to stop any bleeding. The opening in the skin is then covered with a dressing. No sutures are needed.

Your intravenous line will be removed.

The procedure is usually completed within one hour.
What are the benefits vs. risks?
Benefits

No surgical incision is needed—only a small nick in the skin that does not have to be stitched closed.
The IVC filter allows patients to avoid the side affects of medications called blood thinners that prevent blood clots from forming.

Risks

Any procedure where the skin is penetrated carries a risk of infection. The chance of infection requiring antibiotic treatment appears to be less than one in 1,000.
There is a very slight risk of an allergic reaction if contrast material is injected.
Any procedure that involves placement of a catheter inside a blood vessel carries certain risks. These risks include damage to the blood vessel, bruising or bleeding at the puncture site and infection.
There is a chance that the IVC filter can lodge in the wrong place, change position or injure a nearby organ.
The IVC filter may break loose and travel to the heart or lungs causing injury or death.
Rarely, IVC filters become so filled with clots that they block all flow in the blood vessel causing swelling in the legs.
In some cases, retrievable filters cannot be removed.