Inferior vena cava filters are a form of preventative treatment for pulmonary embolism (PE). While they are an important tool in the world of thrombosis, there is a lot of confusion about what these filters do and who they should be used for. Dr. Piotr Sobieszczyk, a member of the interventional cardiology team at Brigham and Women’s Hospital, was kind enough to speak with NATF and to shed some light on this often misunderstood preventative treatment.
IVC filter with quarter for size comparison
What is an IVC filter?
“An IVC filter is a metal umbrella or metal scaffolding, which is placed in the inferior vena cava to filter the blood flowing from the legs to the veins,” explained Dr. Sobieszczyk. “It is designed to capture blood clots that may develop in the legs and dislodge, keeping them from migrating and going to the pulmonary artery.”
The inferior vena cava (IVC) is the largest vein in the body and is responsible for bringing blood from the legs to the heart and lungs. In patients with deep vein thrombosis (DVT), blood clots can break off and travel to the lungs through this vein, causing pulmonary embolism (PE). IVC filters act as a net, allowing blood to flow through them but catching the blood clots before they reach the lungs.
IVC filters are not the best treatment for everyone. They are for patients with existing DVT, who cannot safely be on anticoagulation therapy. This may be because their bodies don’t react well to anticoagulation medications or they can’t be on the medication for a procedural reason. For example, filters may be used in patients who need their anticoagulation treatment interrupted for surgical reasons.
Permanent vs. Retrievable
There are two types of filters that doctors use, permanent filters and retrievable filters. The different uses of both have evolved greatly over time.
“[The permanent filter] has been around for several decades and initially it was a rather bulky device,” explained Dr. Sobieszczyk. “It was a surgical procedure that required an incision in the vein and the leg and positioning through a very large port catheter.”
Today, IVC filters are implanted through an IV or catheter that is placed in the common femoral vein, which can be found on top of the leg and hip joint, or in the jugular vein. Physicians can implant them through other veins, but the jugular vein and common femoral vein are the most common. It is considered a minimally invasive surgery, involving only local anesthesia.
Permanent filters are currently used if the risk of a recurrent blood clot is high and anticoagulation therapy is not an option. This could be patients whose bodies’ react negatively to blood thinners or patients who experience recurrent PE, despite being on anticoagulation therapy. Greenfield filters and Trapeze filters are an example of permanent filters.
Retrievable filters were developed after permanent filters, when doctors realized their patients would benefit from something more temporary.
“With the technological advances and the recognition that many patients would benefit from temporary protection and temporary filter placement, there was interest in developing a filter that could be put in for an unspecified period of time during which the patients were vulnerable and could not be anticoagulated and needed some protection from a PE,” explained Dr. Sobieszczyk. “But [the filter] could then, with return of health or anticoagulation… be retrieved and not in place forever. That led to the advent of retrievable filters.”
Retrievable filters are now the most commonly used. Their design is similar to that of permanent filters, but they are built to be retrieved after several months, once the danger of a PE has gone down.
What are the risks of an IVC filter?
As with all medications and medical procedures, the IVC filter comes with its own set of risks and complications.
“The risks associated with IVC filter placement are related to it being a foreign body, which in itself has a small risk of triggering thrombus formation in the IVC filter,” noted Dr. Sobieszczyk. “We know that over time, IVC filters are associated with increasing the risk of DVT.”
In some cases, metal fragments from the filter can break off and flow to the heart and lungs. However, Dr. Sobieszczyk noted that this is very rare in more modern devices. Filters can also move from where they were originally placed or can penetrate the walls of the IVC.
In order to avoid these risks, it’s important that patients receive follow-up care after they’ve had a filter put it. This is especially important for retrievable filters, which should be removed as soon as they aren’t needed.
“The need for the filter should be reassessed on a regular basis and retrieved as soon as possible,” explained Dr. Sobieszczyk. “With a retrievable filter, a basic principal is that you need to reassess and reevaluate the patient on a regular basis. How frequently depends on what the indication for the IVC filter was.”
Retrievable filters should ideally be removed within six months, however a disconnect in patient care can cause a breakdown in this process. Dr. Sobieszczyk has seen patients with these filters still in two years after their placement.
“The longer you wait, the harder it becomes to retrieve the filter,” remarked Dr. Sobieszczyk.
He stressed the importance of self-advocacy in patients. They need to serve as their own advocates and ask their doctor about filter removal. Awareness around the differences between permanent and retrievable filters can be lacking among some physicians, which can lead to filters being in place for too long.
What lies in store for the future of filters?
According to Dr. Sobieszczyk, fewer and fewer filters are being implanted. Doctors are more selective of which patients need them. They have also become better at following up with patients for filter retrieval. There is an increasing focus on safety, both in how patients are cared for and in the design of the filters themselves.
“There’s a constant drive to make these filters safer and less likely to cause any mechanical problems,” Dr. Sobieszczyk explained. “There’s constant development of easier to retrieve filters”
As filters become safer, their importance in the battle against thrombosis grows. They are an important preventative tool for the patients who rely on them. Increased patient and provider awareness is key to ensuring patients using them receive the best care possible.