Overview of Inferior Vena Cava Filter
Pulmonary embolism, a condition where a blood clot blocks an artery in the lungs, often happens due to venous thromboembolism – a blood clot in the veins, usually in the leg. This is a common cause of death in hospital patients that can be prevented. Doctors use a combination of special devices and medicines to thin the blood in patients who are at high risk of this condition. The most common and first-line treatment for these blood clots and any resulting pulmonary embolisms is medication that thins the blood, known as anticoagulation.
However, in certain situations – such as when patients cannot take anticoagulation, this treatment fails, leads to complications or the blood clot keeps getting bigger despite adequate treatment – another approach known as an Inferior Vena Cava (IVC) filter is used. This is a device placed in the largest vein in the body (the inferior vena cava) to prevent blood clots from moving to the lungs.
The first IVC filter came into use in 1973, and currently there are two main types – permanent ones and those which can be removed. Since 2003 and 2004, when the FDA approved IVC filters that can be removed, their use has increased significantly.
However, studies show there is no difference in the total death rate in patients with deep vein thrombosis (blood clots in the leg) treated with IVC filters compared to those only treated with anticoagulation. In cases where IVC filters are used to prevent venous thromboembolism in high-risk patients, especially if they cannot take anticoagulation, these studies haven’t shown any benefit in terms of reducing death rates. In fact, IVC filters have even been associated with a higher risk of repeated deep vein thrombosis and other complications.
Anatomy and Physiology of Inferior Vena Cava Filter
To make sure a medical device called a filter is placed correctly and to avoid problems, it’s important for the doctor to understand the normal structure and any variations in a large vein in your body called the inferior vena cava (IVC). From your groin, a vein called the common femoral vein goes upwards, changing names to the external iliac vein. This vein then joins up with another vein, the internal iliac vein, to make the common iliac vein. The point at which the right and left common iliac veins come together to make the IVC happens around the level of the fifth bone in your lower back(L5).
Please note that the IVC can be divided into two parts by the veins coming from your kidneys (the right and left renal veins). These veins join with the IVC around the level of the second bone in your lower back.
In about 2% of people, there’s an unusual property called duplicate inferior vena cava (IVC). This means the person has two IVCs instead of one. This could be an issue if a person experiences a lung clot (pulmonary embolism) even after an IVC filter has been placed. This mostly happens when a certain vein (the left supracardinal vein) doesn’t disappear as it should as a person grows. Likewise, there is another unusual property that might cause difficulties with installing the filter: a vein from the left kidney wrapping around the aorta (circumaortic left renal vein). If this is the case, the filter might need to be placed above the kidneys or two filters might need to be placed. Doctors often mistake these unusual properties for swollen lymph nodes in the back of the abdomen (retroperitoneal adenopathy).
There is also a condition where the IVC measures greater than 28 mm, known as mega vena cava. Usually, the IVC filter is designed to cover an IVC up to 28 mm in diameter. However, there is a specific type of filter, called a bird’s nest filter, that can be used in larger IVCs, up to 40 mm in diameter.
Why do People Need Inferior Vena Cava Filter
Medical institutions like the American Heart Association (AHA), the American College of Chest Physicians (ACCP), and the American College of Radiology (ACR)/Society of Interventional Radiology (SIR) all suggest the use of a device called an inferior vena cava (IVC) filter for patients who have a condition called venous thromboembolic disease (VTE). The IVC filter is especially recommended for people who cannot take blood-thinning medication, need to stop taking it due to complications, or continue to experience VTE even after taking the medication.
With the introduction of removable IVC filters, their use has expanded not only to the aforementioned patients but also to others. They are useful for patients who face high chances of repeated blockages in their blood flow due to VTE, complications from blood thinners, and cancer-related VTE. The filters are also recommended for certain patients who can’t properly follow medication routines or for those who have limited heart and lung capacity. Despite their wider application, studies have shown that many of these filters are not removed from the patients. Because the removal of these filters is not yet properly guided by official rules or studies, doctors need to make a judgment call during these situations.
In some cases, IVC filters are also used for patients who are prone to the risk of VTE due to various reasons. For instance, people who can’t move much due to major injuries or operations, or those who have medical conditions like cancer that increase the tendency of their blood to form clots might be given these filters. A study was done where such patients were divided into two groups: one was given a permanent IVC filter while the other was prescribed blood thinners. Initially, the group with the installed filter experienced fewer blood flow blockages. However, after observing for two years, it was found that this group faced a much higher number of repeated VTE compared to the other group. Therefore, the effectiveness of a permanent IVC filter still remains uncertain in the long term.
When a Person Should Avoid Inferior Vena Cava Filter
Usually, putting a filter in the inferior vena cava, a large vein that carries blood from your lower body to your heart, is considered safe. There aren’t any reasons why someone absolutely shouldn’t have this type of filter placed. However, there are some situations where it might not be a good idea. For example, if a person has a serious problem with their blood clotting, which cannot be fixed and could lead to uncontrolled bleeding during the procedure. Another situation is if the person has bacteremia, a condition where bacteria are present in the bloodstream, which might lead to an infection.
Equipment used for Inferior Vena Cava Filter
If you’re getting an Inferior vena cava (IVC) filter procedure, your doctor will use several medical tools. The IVC filter is a small, cone-shaped device that helps prevent blood clots from reaching your lungs. A catheter, which is a thin, flexible tube, is used to place this filter inside your body. Your doctor will use an X-ray machine and an ultrasound machine to guide the placement of the filter. These machines create images of the inside of your body which your doctor can look at during the procedure.
You’ll be given a local anesthetic, which is a medication that will numb the area where your doctor is working, so you won’t feel any pain. An IV line, or a tube inserted into a vein in your arm, will provide any other necessary medications. You might also receive a sedative through this IV line, which will help you relax during the procedure.
Last but not least, your doctor will use a contrast dye. This is a special drug that is injected into your body to make the images on the X-ray and ultrasound clearer. It helps your doctor to see your veins and the IVC filter more easily, ensuring the procedure is done safely and properly.
Who is needed to perform Inferior Vena Cava Filter?
A procedure such as this involves a specific type of doctor known as an interventional radiologist. This expert uses imaging techniques, like X-rays or ultrasounds, to guide minor procedures. A nurse and a technologist, a professional who specializes in operating medical technology, aid the radiologist in conducting the procedure. They all play an important role in ensuring that your treatment is safe and effective.
Preparing for Inferior Vena Cava Filter
Before any medical procedures, there are important steps to follow to ensure everything goes smoothly. The doctor will conduct some tests, like checking your blood’s ability to clot (coagulation profile) and how well your kidneys are working (renal function tests). These are critical to understand the risk of excessive bleeding and whether a special dye (contrast) can be used during the procedure.
You should not eat any solid foods for eight hours before the procedure and avoid drinking liquids two hours prior.
The doctor will also review your medications. Some medicines might need to be adjusted or stopped temporarily to avoid any complications during the procedure.
In some cases, the doctor might use a special type of scan (cross-sectional imaging) to look at the inferior vena cava (a large vein that helps carry deoxygenated blood from the lower half of the body back to the heart) and to choose the best location for the procedure. If no prior images are available, the doctor might opt for a procedure called cavography. This allows the doctor to check if there are any unusual features or duplications of the vena cava, measure its diameter, and see if there are any clots that need to be dealt with.
How is Inferior Vena Cava Filter performed
The Inferior Vena Cava (IVC) filter is a medical device often placed within people who are admitted to a hospital due to the critical management needs of a condition called venous thromboembolism (VTE), which is essentially a blood clot that starts in a vein. However, it can also be inserted in an outpatient setting, meaning you wouldn’t require an extended stay in a hospital. The procedure involves inserting the filter into a major vein – usually one in the neck (called the internal jugular vein) or the thigh (femoral vein). Regardless of the vein chosen for this process, the procedure is typically performed from the right side of the body. This is because the path to the IVC is more direct on the right side and it’s generally easier for doctors to perform the procedure from this side.
How the doctor makes this insertion depends largely on the patient’s specific situation. For example, if a patient already has a tube inserted for a different treatment, cannot breathe on their own (intubated), or needs an internal ultrasound for guidance, then the femoral vein in the thigh might be a more suitable choice. The right internal jugular vein in the neck is usually preferred as it provides a direct, simple route to the IVC without disturbing any blood clot that could potentially exist in the thigh or pelvic veins.
Different types of imaging are used to guide doctors during the filter placement. These may include fluoroscopy (a type of X-ray that shows real-time moving images), duplex ultrasound (high-frequency sound waves to see how blood flows through the veins), or intravascular ultrasound (IVUS, a medical imaging methodology using a specially designed catheter with a miniaturized ultrasound probe attached). Most often, doctors use a method called fluoroscopy that is usually done in a particular room called an interventional suite. Nevertheless, if a patient cannot be moved to this room, ultrasound can be a good alternative as the filter can be inserted right at their bedside.
The procedure itself begins with cleaning the area through which the filter will be inserted. A small cut is then made in the skin, and a thin tube called a catheter is inserted. Ideally, doctors use fluoroscopic imaging to guide the procedure. The filter is pushed inside the body using the catheter. The best place for the filter is just beneath the point where the veins from the kidneys drain into the IVC. This location is seen as safe because there’s a low chance of a clot blocking the veins from the kidneys. However, in certain scenarios like pregnancy, or if there’s already a clot within the above-mentioned preferred location, the doctor may place the filter in a part of IVC above the kidney veins.
Possible Complications of Inferior Vena Cava Filter
Complications from the use of an inferior vena cava filter, a device placed in a large vein to catch blood clots, can occur during different stages: the procedure itself, after the procedure, and during the device’s removal.
During the placement procedure, the most common problems are bleeding and blood clot formation. Other complications at this stage can be the filter tilting or changing position, or the filter being placed incorrectly. These situations can make the filter less effective and more challenging to remove later.
After the procedure, some complications might include formation of big blood clots in the large vein, leading to leg pain and swelling. This can also increase the risk of a pulmonary embolism, a dangerous condition where clots travel to the lungs. Kidney failure can also occur if the blood clot extends beyond the filter. Another potential complication is the penetration of the major vein by the filter. While some designs include hooks to resist movement of the filter, these tend to increase the risk of this complication. Additionally, the filter can break, leading to fragments that could travel towards the heart and lungs.
Upon trying to remove the filter, the longer it stays, the higher the risk of complications like fracturing and damage to the vein. Therefore, removing the filter as soon as it is no longer needed is strongly advised.
Compared to permanent filters, the so-called retrievable filters, designed for temporary use and later removal, have shown to have more complications. Fracture during removal is the most common of these. On the other hand, permanent filters more commonly involve misplacement issues during procedure.
What Else Should I Know About Inferior Vena Cava Filter?
Inferior vena cava (IVC) filters are medical devices that doctors place in your body to prevent blood clots in your legs from traveling up to your lungs. But their use is debated because not enough thorough studies have been done to prove their long-term effectiveness. As it stands, most doctors make a decision to use these IVC filters based on their best judgement and past experiences.
One large trial, named the PREPIC trial, showed these filters helped limit the risk of recurring blood clots in the lungs. However, it also showed an increased risk of recurring blood clots in the legs, thus not giving a clear answer on whether it should be used over blood thinners. There is an ongoing need for more thorough studies to help doctors better decide when these IVC filters should be used.
Blood clotting is a significant cause of death among pregnant women, with them being six times more at risk compared to others. Doctors normally treat these clots with blood thinners but in some cases, like when there’s high risk of bleeding or when the clotting keeps recurring, they may place an IVC filter. But this has to be done carefully as IVC filters can also move from their original placement due to changes in the body from the pregnancy.
IVC filters that can be removed after a time (retrievable IVC filters) are now used more often. However, doctors sometimes don’t follow guidelines and fail to remove these filters leading to concerns. There have been situations where this rate of removal has varied depending on where you live or the type of medical institution. These filters are most often used in patients who can’t be treated with blood thinners, but this condition is often temporary. So, as soon as these patients can take these blood thinners, the IVC filters should ideally be removed within 30 days of insertion to reduce the chance of recurrent blood clots in your legs and IVC formation.