Patients who are at high risk for developing blood clots are regularly given inferior vena cava filters in Chicago hospitals and around the nation. While the filters have been used for years in this application, recent studies are starting to question not only the potential side effects of the IVC filters and their efficacy, but also the way doctors are handling their use and removal following treatment.
Why are IVC filters necessary?
Some patients are more susceptible than others to forming blood clots within their blood vessels. According to University of Michigan Department of Vascular Surgery, this is a potentially dangerous condition known as deep vein thrombosis. DVT can develop anywhere in the body, but is most common in the legs and thighs. If the blood clot breaks loose and travels through the veins it could block blood flow to the lungs in a condition known as pulmonary embolism. If large enough, the clot could block blood flow in and around the heart itself. This condition can cause patients severe chest pain, organ damage, and often results in death. Pulmonary embolism-related deaths are estimated to occur 200,000 times every year in the U.S.
Years ago, doctors developed inferior vena cava filters for treatment of patients who do not respond well to, or are unable to safely use anticoagulants. The inferior vena cava is the largest vein in the human body. All deoxygenated blood from the body’s lower extremities is carried through the IVC back to the heart and then into the lungs where it becomes oxygenated once more. All blood that passes through the lower body must pass through the IVC to reach the heart. The filter is designed to catch and hold onto clots that pass through the IVC in order to prevent them from traveling to the heart and lungs, causing large, fatal pulmonary emboli. Over time, enzymes in the blood break down the clots on the filter, and blood is left clot free.
Inferior vena cava filter placement
According to the National Center for Biotechnology Information, when a filter is placed within the IVC, surgeons will utilize either the femoral vein in the groin or the internal jugular vein in the neck to act as a transport to the IVC. Using special tools, contrast dyes, and x-rays, the doctor guides a special catheter containing the filter until it is in place in the IVC just below the kidneys. If there is already a clot in the IVC, placement may be moved above the kidneys. The doctor then deploys the filter, which stays in place in a pressure fit against the walls of the vein, and removes the catheter.
A study: potential complications without any benefits
A recent study in the Journal of the American Medical Association Internal Medicine found that these filters may not be as safe as many healthcare professionals once believed them to be. Researchers highlighted the severe lack of concrete data from randomized controlled trials that demonstrate the long-term safety and efficacy of using these IVC filters. Currently, there is nothing that indicates that the benefits of these filters outweigh the potential harm they may cause, and placing the filters may be a form of medical malpractice in some situations. The study included a review of 952 patient records, all of which included patients who received retrievable IVC filters. Findings include the following:
- Eight percent of patients who had an IVC filter in place still developed DVT.
- 5 percent of patients with an IVC filter in place developed pulmonary embolism.
- Many patients received their filters after they could have begun receiving anticoagulant therapy.
- Patients developed severe complications with their filters in one percent of cases. These complications include filter migration along the IVC, the formation of large, potentially deadly clots at the filter site, and perforation of the IVC or other veins. While these cases could indicate the use of a defective medical product, even one percent of total cases indicate that more than defective products are to blame.
- Of 679 patients with retrievable filters, only 8.5 percent were successfully removed.
- 3 percent of attempted removals of the filters failed.
Overall, half of venous thromboembolism events that occurred in patients with IVC filters happened in those who received their filter as a preventative measure but did not show any actual signs of DVT at the time. Researchers conclude that the use of IVC filters to prevent and treat DVT and their resulting migratory clots does not promote optimal outcomes because rates of DVT and venous thromboembolism remain high even after filter placement. The potentially harmful practices of leaving the retrievable filters in place and failure to use anticoagulant therapy at the right time were factors in the researchers’ findings. Additionally, the researchers called for more studies detailing the long-term effects of unretrieved removable filters.
Another study found in the journal Circulation followed 400 patients eight years after their permanent IVC filters were placed to prevent pulmonary embolism. Researchers found that these filters reduce the risk of patients developing pulmonary embolism, but increased the likelihood that they would develop DVT. Additionally, there was no change in the survival rate between those with filters and those without. This may indicate that systemic use of IVC filters in the general population for prevention is not proper, and may cause patients unnecessary harm.
The U.S. Food and Drug Administration has received nearly 1000 reports of adverse events involving IVC filters, many of which they attributed to extended use of retrievable filters. In response, the FDA issued a warning reminding doctors that these devices that are intended for short-term use and recommending that they be removed immediately once the threat for pulmonary embolism has passed. With nearly 20 percent of retrieval attempts failing, however, doctors and patients should both consider the potential consequences of IVC filter use prior to their implementation.