Inferior vena cava filter

# Overview
An inferior vena cava filter is a medical device that is implanted into the inferior vena cava to prevent pulmonary emboli (PEs). IVC filters are used in case of contraindication to anticoagulation, failure of anticoagulation or complication to anticoagulation in patients who have a venous thromboembolism disease or as a prophylactic measure for patients with high risk of pulmonary embolism.

# Indications for use
Most filters are placed under one of the following indications:
- Classic: In the presence of deep vein thrombosis and/or pulmonary embolism with:
Absolute contraindication to anticoagulation
Complication of anticoagulation
Progression of the Deep vein thrombosis (DVT) or recurrence of the pulmonary emboli (PE) despite adequate anticoagulation
- Absolute contraindication to anticoagulation
- Complication of anticoagulation
- Progression of the Deep vein thrombosis (DVT) or recurrence of the pulmonary emboli (PE) despite adequate anticoagulation
- Relative: In the presence of DVT / PE with:
Large free floating thrombus in the IVC or the iliofemoral veins
Patients with limited cardiac reserve
Non-compliant patients
- Large free floating thrombus in the IVC or the iliofemoral veins
- Patients with limited cardiac reserve
- Non-compliant patients
- Prophylactic: In the absence of DVT and PE
Major trauma
Before surgery on a patient at high risk of developing DVT / PE
- Major trauma
- Before surgery on a patient at high risk of developing DVT / PE

# Placement
IVC filters are placed endovascularly, meaning that they are inserted via the blood vessels.  Historically, IVC filters were placed surgically, but as designs changed, they could be introduced through a thin tube or catheter via percutaneous access to the venous system which can be obtained either through the femoral vein (the large vein in the groin), the internal jugular vein (the large vein in the neck.) or via the arm veins with one design. Choice of route depends mainly on the amount and location of blood clot within the venous system. To place the filter, a catheter is first directed into the IVC through the venous access using fluoroscopic guidance, followed by injection of iodinated contrast material or carbon dioxide in order to define the anatomy and caliber of the cava and to determine the level of the lowest renal vein, then the filter is introduced through the introduction sheath and deployed into the desired location, usually just below the junction of the IVC and the lowest renal vein. Alternatively, the filter can be deployed at bedside using intra vascular ultrasound guidance to evaluate the cava and determine the level of the renal veins.
Review of prior cross-sectional imaging or a venogram of the IVC is essential before deploying the filter to assess for potential anatomic variations, thrombi within the IVC, or areas of stenosis, as well as to estimate the diameter of the IVC. The size of the IVC may affect which filter is deployed, as some (such as the Bird's Nest filter) are approved to accommodate cavas larger than 28 mm. There are situations where the filter is placed above the renal veins (e.g. pregnant patients or women of childbearing age, renal or gonadal vein thrombosis, etc.). Also, if there is duplication of the IVC, the filter is placed above the confluence of the two IVCs or a filter can be placed within each IVC.

# Complications
- Puncture site hematoma or venous thrombosis
- Incorrect deployment: This may require retrieval of the device
Malpositioning
Incorrect sizing with subsequent filter embolization
Filter tilt
Failure to open completely
- Malpositioning
- Incorrect sizing with subsequent filter embolization
- Filter tilt
- Failure to open completely
- Delayed complications:
IVC thrombosis in about 5-10%
Recurrence of PE in 5-7%
IVC perforation
Caudal (towards the iliac veins), or cranial (towards the heart) migration
- IVC thrombosis in about 5-10%
- Recurrence of PE in 5-7%
- IVC perforation
- Caudal (towards the iliac veins), or cranial (towards the heart) migration

## Society of Interventional Radiology Standards of Practice Committee Classification of Complications by Outcome 

### Minor Complications
- No therapy, no consequence
- Nominal therapy, no consequence; includes overnight admission for observation only

### Major Complications
- Require therapy, minor hospitalization (<48 hours)
- Require major therapy, unplanned increase in level of care, prolonged hospitalization (>48 hours)
- Permanent adverse sequelae
- Death

# Retrieval
Most IVC filters are permanent. However, Retrievable filters are now available for use. These "retrievable" filters are designed in a way that they can be removed from the body within certain period of time, most likely through the Jugular vein.  As filters become gradually embedded in the IVC wall, filter retrieval is considered suitable in the first few weeks following implantation to reduce the risk of vessel injury. Newer designs can now be left in place for prolonged periods and retrievals after a year are now being reported. These filters include the ALN, Option, G2 Express, Tulip and Celect filters.

# Landmark trials
1.  A Clinical Trial of IVC Filters in the Prevention of PE in Patients with Proximal DVT 
- Objective:  Test the efficacy and safety of IVC filters in PE prevention using a high risk population of patients with proximal DVT.
- Methods:    Dr. Herve Decousus and his team, led a two-by-two factorial design was used to randomize 400 patients with proximal DVT who were at risk for PE to receive either an IVC filter (200 patients) or no filter (200 patients), and to receive enoxaparin (195 patients) or unfractioned heparin (205 patients).  The outcomes were the recurrent VTE rate, death rate, and major bleeding rate at day 12 and at 2 years.
- Results: At day 12; 1.1% of patients assigned to the IVC filter arm and 4.8% of patients without a filter had a symptomatic or asymptomatic PE, with an odds ratio of 0.22 and a 95% confidence interval from 0.05 to 0.90.  At two years 20.8% of patients assigned to the  IVC filter arm and 11.6% % without the filter had a recurrent DVT, with an odds ratio of 1.87, and 95 % confidence interval from 1.10 to 3.20.  There were no significant differences in mortality or other outcomes.  1.6% of patients who received low molecular heparin group (enoxaparin) and 4.2% of the unfractioned heparin group had a symptomatic or asymptomatic PE with an odds ratio of 0.38 and a 95% confidence interval from 0.10 to 1.38.  DVT
- Conclusions:  This study concluded that IVC filters had an initial benefit preventing PE, but there is an excess of recurrent DVT
without  any difference in mortality.  On the other hand; enoxaparin was similar in terms of effectiveness and safety as unfractioned heparin in the prevention of (PE).
2. PREPIC (Prevention du Risque d'Embolie Pulmonaire par Interruption Cave) study
- Objective: Eight-year follow-up study to assess the long-term effect of IVC filters.
- Methods: Four hundred patients with proximal deep-vein thrombosis with or without pulmonary embolism were randomized either to receive or not receive an IVC filter in addition to standard anticoagulant treatment for at least 3 months. Data on vital status, venous thromboembolism, and post-thrombotic syndrome were obtained once a year for up to 8 years.
- Results: Symptomatic PE occurred less frequently in the IVC filter group (6.2%) compared with the no-filter group (15.1%, p=0.008). However, DVT was more frequent in the filter group (35.7%) compared with the no-filter group (27.5%, p=0.042). Post-thrombotic syndrome and mortality rates were almost similar in both groups.
- Conclusions: Placement of an IVC filter reduced the risk of pulmonary embolism (PE), but increased the risk of DVT and had no effect on survival.

# IVC filter brands
(In alphabetical order)
- B Braun Tempofilter IVC filter (retrievable)
- B Braun VenaTech LGM IVC filter
- B Braun VenaTech LP IVC filter
- Bard G2 IVC filter
- Bard Recovery IVC filter (retrievable) (no longer sold)
- Boston Greenfield IVC filter
- Cook Birds Nest IVC filter
- Cook Celect IVC filter (retrievable)
- Cook Gunther Tulip IVC filter (retrievable)
- Cordis OptEase IVC filter (retrievable) 
- Cordis TrapEase IVC filter
- Mobin-Uddin Umbrella IVC filter (no longer sold)
- Pyramed ALN IVC filter (retrievable)
- Rex Medical Option IVC filter (retrievable) (in clinical trials)
- Simon Nitinol IVC filter
- Vena-Tech IVC filter

# Diagnostic Findings

## Inferior Vena Cava filter thrombosis

# Video of IVC Filter Deployment