Inferior vena cava filter | |
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![]() Inferior vena cava filter - Gunther Tulip. [1] | |
Other names | IVC filter |
Specialty | Cardiovascular |
An inferior vena cava filter is a medical device made of metal that is implanted by vascular surgeons or interventional radiologists into the inferior vena cava to prevent a life-threatening pulmonary embolism (PE) or venous thromboembolism (VTE). [2] [3]
The filter is designed to trap a blood clot and prevent its travel to the lung where it would form a pulmonary embolism. [4] [3] Their effectiveness and safety profile is well established, and they may be used when anticoagulant treatment is not sufficient. [5]
Results from the PREPIC study and other studies which have shown many long-term complications of IVC filters led to the introduction of retrievable IVC filters. [6] The first retrievable IVC filters were approved by FDA in 2003 and 2004. [7]
In 2012, the American College of Chest Physicians recommended IVC filters for those with contraindications to anticoagulation who either have acute PE or acute proximal deep vein thrombosis (above the knee). [8] [9]
The first IVC filter was created by Kazi Mobin-Uddin who published his findings in 1969 in the New England Journal of Medicine. [10] [11] [12] [13] The Mobin-Uddin filter was later replaced by the Greenfield filter developed by Lazar Greenfield which had a lower rate of filter related complications. [12]
While the ability to retrieve a filter does exist for many models, it cannot be guaranteed that all cases of filter placement will allow for, or be indicated for retrieval. Thus, the requirements and indications for permanent placement of filters is used to decide on when to use both permanent and temporary IVC filters. [14]
Long-term risk factors must be considered as well, to include life expectancy of more than six months following insertion, and the ability of the patient to comply with anticoagulation therapy. [5] The decision to use a filter that is temporary vs permanent basically is tied to the expected duration of time that protection is needed to prevent pulmonary emboli from passing to the heart and lungs. One such guideline is outlined below: [14]
While many studies have been done on the efficacy of Vena Cava filters, there still have not been any major studies done on the actual placement and removal of the filters regarding standard guidelines. Which is why the Society of Interventional Radiology created a multidisciplinary panel that developed the following guidelines to see if someone qualifies for implantation:[ citation needed ]
These are patients that should strongly consider having IVC filter placement, as they are at greatest risk of pulmonary embolus.
This is a maybe category; normally it represents patients who could benefit from an IVC filter, but may be just fine without one as well.[ citation needed ]
These are usually very controversial reasons to do an IVC filter, and most radiologists and doctors generally will not recommend an IVC filter if other options are available instead.
There is no current published data confirming the benefit of removing an IVC. Because of this, the Society of Interventional Radiology created a multidisciplinary panel that developed the following guidelines to see if someone qualifies for removal: [5]
An IVC filter, just by doing its job properly (catching embolic material), can eventually fill up with embolic material and cause a circulatory impairment that may warrant revision with vascular surgery (new filter, stent additions, or otherwise). A representative case has been reported in science journalism of the type that reports interesting unusual causes and solutions of symptoms; [16] in this instance, the symptom was orthostatic hypotension. [16] Physicians speculate that this problem is uncommon but nonetheless worth consideration in differential diagnosis. [16]
In those with initial acute proximal DVT or acute PE who had IVC filters placed instead of anticoagulation, and who have their risk of bleeding resolve, the American College of Chest Physicians suggested, in 2012, that they receive a standard course of anticoagulation. [8] [9] While IVC filters are associated with a long term risk of DVT, [17] they are not, alone, reason enough to maintain extended anticoagulation. [8] [9]
The main function of a vena cava filter is to prevent death from massive pulmonary emboli. Long-term clinical follow-up studies have shown that this is accomplished in 96% of cases having a standard stainless-steel Greenfield filter. [18]
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In August, 2010, the FDA released an Initial Communication on the Risk and Adverse events associated with Long Term use of an inferior vena cava filter. [19] Over a period of about 5 years, they identify 921 events. While not the majority of cases, that number still represents a statistical significance of the use of long-term IVCs.
Of these IVC filter side effects, 328 involved device migration, 146 involved embolizations after detachment of device components, 70 involved perforation of the IVC, and 56 involved filter fracture. Much of the medical community believes that this large number of adverse events is related to the heart filter remaining in place for longer than necessary.
Common issues relating to failure, to include death (the other 4% of cases) include:
While these side effects are not common (less than 10-20% of patients), many do report issues stemming from the placement and complication of the IVC while inside of the body. [20]
Numerous small published articles and case studies report describe similar issues to the above. Most notably:
Even though the cases above are the exception, and not the rule, most radiologists object to doing prophylactic filter insertions in patients who do not have thromboembolic diseases. [32] For the most part, whenever possible, interventional radiologists would rather start the patient on anticoagulants than use an IVC, even if requested or referred via a doctor. [33]
While most IVC filters are made of non-ferromagnetic materials, there are a few types that are weakly ferromagnetic. Accordingly, IVC filters fall under the MRI Safe and MRI Conditional categories depending mostly on type of material used during construction. Rarely will one find an MRI Not Safe IVC filter, as most of the steel, and other ferromagnetic material devices have been discontinued via the FDA.[ citation needed ]
IVC filters are attached to the vena cava via hooks on their ends. Some are compression springs, which compress outward onto the side wall of the vena cava; however, they still have small hooks that retain their location. These hooks aid in the anchoring and healing process, as they allow the tissues to 'ingrow' around them, securing the IVC in place. It is unlikely, then, after 4 to 6 weeks of healing, that an MRI of 1.5 tesla, up to 3 tesla, will cause any level of dislodging to occur to the IVC filter.[ citation needed ]
Studies of MR examination of both animals and humans, with implanted IVC filters, have not reported complications or symptomatic filter displacement. [34] [35] [36] [37] [38] [39]
Several animal studies have even used "real-time" MR for the placement of IVC filters to check for rotation, sheering, and other artifacts. [40] [41]
As part of the 'routing' survey for MRI studies, patients who have IVC filters will often need verification from the doctor, or medical records, to state that the IVC is safe for the MRI. Most patients with weakly or non-safe ferromagnetic implants will be given a card, which they keep on their person at all time, that can help isolate if it is safe to do an MRI.
For patients who have been denied MRI scans for safety reasons, doctors usually recommend the CT scan with contrast as an alternative.
Most IVC filters that have been tested have been labeled as “MRi safe”; the remainder of IVC filters that have been tested are “MR conditional.” Patients who have been treated with nonferromagnetic IVC filters can undergo MR examination any time after filter implantation. In patients who have been treated with a weakly ferromagnetic IVC filter (Gianturco bird nest IVC filter [Cook], stainless steel Greenfield vena cava filter [Boston Scientific]), it is advised that the patient wait at least six weeks before undergoing an MR examination (because these older devices initially may not be anchored as firmly in place as other devices discussed in the present context), unless there is a strong clinical indication to perform the MR examination sooner after implantation, and as long as there is no reason to suspect that the device is not positioned properly or that it is not firmly in place. Most studies of IVC filters have generally been conducted at 1.5 tesla or less, although many IVC filters have now been evaluated at 3 tesla and deemed acceptable for MR examination. [42] [43]
IVC filters are placed endovascularly, meaning that they are inserted via the blood vessels. Historically, IVC filters were placed surgically, but with modern filters that can be compressed into much thinner catheters, access to the venous system can be obtained via the femoral vein (the large vein in the groin), the internal jugular vein (the large vein in the neck) or the arm veins with one design. Choice of route depends mainly on the number and location of any blood clot within the venous system. To place the filter, a catheter is guided into the IVC using fluoroscopic guidance, then the filter is pushed through the catheter and deployed into the desired location, usually just below the junction of the IVC and the lowest renal vein. [44]
Review of prior cross-sectional imaging or a venogram of the IVC is performed before deploying the filter to assess for potential anatomic variations, thrombi within the IVC, or areas of stenoses, as well as to estimate the diameter of the IVC. Rarely, ultrasound-guided placement is preferred in the setting of contrast allergy, chronic kidney disease, and when patient immobility is desired. The size of the IVC may affect which filter is deployed, as some (such as the Birds Nest) are approved to accommodate larger cavae. 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 thromboses, etc.). Also, if there is duplication of the IVC, the filter is placed above the confluence of the two IVCs [45] or a filter can be placed within each IVC. [46]
The concept of a removable IVC filter was first conceived in 1967. [47] In 2003 and 2004 that the United States Food and Drug Administration first approved retrievable filters. [48] In 2005 that the Society of Interventional Radiology (SIR) convened a multidisciplinary conference to address the clinical application of nonpermanent vena cava filters.[ citation needed ]
Retrievable filters are fitted with a device (varying from model to model) that allows them to be easily snared and pulled back into a catheter and removed from the body, often through the jugular vein. Prior to 2004, filters that had been in the IVC for less than three weeks were considered suitable to attempt retrieval, as filters that have been in place longer might have been overgrown by cells from the IVC wall and there was an increased risk of IVC injury if the filter is dislodged. Newer designs, and developments in techniques mean that some filters can now be left in for prolonged periods and retrievals after a year are now being reported. [49] This would include the ALN, Bard G2 and G2x, Option, Tulip and Celect filters.[ citation needed ]
It is important to note that the clinical exam prior to the removal of the filter is vital in understanding both the risk and pathophysiological effects removing the filter will have on the patient. Doctors and medical professionals must consider several key factors (see Indications for removing IVC filters).[ citation needed ]
Veins are blood vessels in the circulatory system of humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are those of the pulmonary and fetal circulations which carry oxygenated blood to the heart. In the systemic circulation, arteries carry oxygenated blood away from the heart, and veins return deoxygenated blood to the heart, in the deep veins.
Thrombosis is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel is injured, the body uses platelets (thrombocytes) and fibrin to form a blood clot to prevent blood loss. Even when a blood vessel is not injured, blood clots may form in the body under certain conditions. A clot, or a piece of the clot, that breaks free and begins to travel around the body is known as an embolus.
Pulmonary embolism (PE) is a blockage of an artery in the lungs by a substance that has moved from elsewhere in the body through the bloodstream (embolism). Symptoms of a PE may include shortness of breath, chest pain particularly upon breathing in, and coughing up blood. Symptoms of a blood clot in the leg may also be present, such as a red, warm, swollen, and painful leg. Signs of a PE include low blood oxygen levels, rapid breathing, rapid heart rate, and sometimes a mild fever. Severe cases can lead to passing out, abnormally low blood pressure, obstructive shock, and sudden death.
Venous thrombosis is the blockage of a vein caused by a thrombus. A common form of venous thrombosis is deep vein thrombosis (DVT), when a blood clot forms in the deep veins. If a thrombus breaks off (embolizes) and flows to the lungs to lodge there, it becomes a pulmonary embolism (PE), a blood clot in the lungs. The conditions of DVT only, DVT with PE, and PE only, are all captured by the term venous thromboembolism (VTE).
Factor V Leiden is a variant of human factor V, which causes an increase in blood clotting (hypercoagulability). Due to this mutation, protein C, an anticoagulant protein that normally inhibits the pro-clotting activity of factor V, is not able to bind normally to factor V, leading to a hypercoagulable state, i.e., an increased tendency for the patient to form abnormal and potentially harmful blood clots. Factor V Leiden is the most common hereditary hypercoagulability disorder amongst ethnic Europeans. It is named after the Dutch city of Leiden, where it was first identified in 1994 by Rogier Maria Bertina under the direction of Pieter Hendrick Reitsma. Despite the increased risk of venous thromboembolisms, people with one copy of this gene have not been found to have shorter lives than the general population. It is an autosomal dominant genetic disorder with incomplete penetrance.
The inferior vena cava is a large vein that carries the deoxygenated blood from the lower and middle body into the right atrium of the heart. It is formed by the joining of the right and the left common iliac veins, usually at the level of the fifth lumbar vertebra.
Deep vein thrombosis (DVT) is a type of venous thrombosis involving the formation of a blood clot in a deep vein, most commonly in the legs or pelvis. A minority of DVTs occur in the arms. Symptoms can include pain, swelling, redness, and enlarged veins in the affected area, but some DVTs have no symptoms.
The azygos vein is a vein running up the right side of the thoracic vertebral column draining itself towards the superior vena cava. It connects the systems of superior vena cava and inferior vena cava and can provide an alternative path for blood to the right atrium when either of the venae cavae is blocked.
Thromboembolism is a condition in which a blood clot (thrombus) breaks off from its original site and travels through the bloodstream to obstruct a blood vessel, causing tissue ischemia and organ damage. Thromboembolism can affect both the venous and arterial systems, with different clinical manifestations and management strategies.
Inferior vena cava syndrome (IVCS) is a very rare constellation of symptoms resulting from either an obstruction, or stenosis of the inferior vena cava. It can be caused by physical invasion or compression by a pathological process or by thrombosis within the vein itself. It can also occur during pregnancy. Pregnancy leads to high venous pressure in the lower limbs, decreased blood return to the heart, decreased cardiac output due to obstruction of the inferior vena cava, sudden rise in venous pressure which can lead to placental separation, and a decrease in kidney function. All of these issues can arise from lying in the supine position during late pregnancy which can cause compression of the inferior vena cava by the uterus. Symptoms of late pregnancy inferior vena cava syndrome consist of intense pain in the right hand side, muscle twitching, hypotension, and fluid retention.
Paget–Schroetter disease is a form of upper extremity deep vein thrombosis (DVT), a medical condition in which blood clots form in the deep veins of the arms. These DVTs typically occur in the axillary and/or subclavian veins.
Post-thrombotic syndrome (PTS), also called postphlebitic syndrome and venous stress disorder is a medical condition that may occur as a long-term complication of deep vein thrombosis (DVT).
Venous stasis, or venostasis, is a condition of slow blood flow in the veins, usually of the legs.
Congenital stenosis of vena cava is a congenital anomaly in which the superior vena cava or inferior vena cava has an aberrant interruption or coarctation.
Superficial thrombophlebitis is a thrombosis and inflammation of superficial veins presenting as a painful induration (thickening) with erythema, often in a linear or branching configuration with a cordlike appearance.
Intermittent pneumatic compression is a therapeutic technique used in medical devices that include an air pump and inflatable auxiliary sleeves, gloves or boots in a system designed to improve venous circulation in the limbs of patients who have edema or the risk of deep vein thrombosis (DVT), pulmonary embolism (PE), or the combination of DVT and PE which is venous thrombeombolism (VTE).
Blood clots are a relatively common occurrence in the general population and are seen in approximately 1-2% of the population by age 60. Typically, blood clots develop in the deep veins of the lower extremities, deep vein thrombosis (DVT) or as a blood clot in the lung, pulmonary embolism. A very small number of people who develop blood clots have a more serious and often life-threatening condition, known as thrombotic storm (TS). TS is characterized by the development of more than one blood clot in a short period of time. These clots often occur in multiple and sometimes unusual locations in the body and are often difficult to treat. TS may be associated with an existing condition or situation that predisposes a person to blood clots, such as injury, infection, or pregnancy. In many cases, a risk assessment will identify interventions that will prevent the formation of blood clots.
Superficial vein thrombosis (SVT) is a blood clot formed in a superficial vein, a vein near the surface of the body. Usually there is thrombophlebitis, which is an inflammatory reaction around a thrombosed vein, presenting as a painful induration with redness. SVT itself has limited significance when compared to a deep vein thrombosis (DVT), which occurs deeper in the body at the deep venous system level. However, SVT can lead to serious complications, and is therefore no longer regarded as a benign condition. If the blood clot is too near the saphenofemoral junction there is a higher risk of pulmonary embolism, a potentially life-threatening complication.
Kazi Mobin-Uddin was an American surgeon specializing in vascular surgery research.
Thrombosis prevention or thromboprophylaxis is medical treatment to prevent the development of thrombosis in those considered at risk for developing thrombosis. Some people are at a higher risk for the formation of blood clots than others, such as those with cancer undergoing a surgical procedure. Prevention measures or interventions are usually begun after surgery as the associated immobility will increase a person's risk.