IVC or inferior vena cava filters are small, metallic devices that get inserted by an interventional radiologist into the inferior vena cava, the large vein that drains blood from the legs back to the heart and lungs. The main reason for placing these devices is for people who have had or are at risk of having a blood clot in their legs and cannot receive blood thinning agents for prevention or treatment.
There are several reasons why a person may not be able to safely take blood thinning agents (i.e. anticoagulation):
- Failure of anticoagulation - e.g. development of blood clot (DVT) or clots in the lungs, i.e. pulmonary emboli (PE), while taking adequate doses of blood thinning agents (e.g. Coumadin or Heparin)
- Contraindication to anticoagulation - e.g. the patient has another medical condition such as brain cancer/metastases, recent stroke, impending or recent surgery.
- High risk patients - e.g. patients who are immobilized after hip surgery or trauma
- Large clots in the IVC or iliac veins which are at high risk of dislodging and travelling to the lungs
Most IVC filters are designed for permanent use. But some newer devices are designed to be removed after a period of use, typically six weeks to six months.
An article in Medpage Today highlights the risks of these retrievable filters. As with any medical procedure or implantable device, the risks, benefits and alternatives must be weighed carefully with every instance.
Retrievable filters allow us to filter blood of patients who typically do not need a permanent safety net. These may be people who are undergoing gastric bypass or hip or knee surgery. They may be young individuals who recently suffered a trauma and are expected to recover and regain normal mobility.
The difficulty understanding or recognizing permanent vs retrievable filters is that they are inserted in the same way and act and perform the same function. This similarity is why most newer filters pass through FDA inspections with relative ease. The similar design and function allows them to undergo less scrutiny than a novel device might. The hope is that the similarity of design and makeup of each device may connote similar safety profiles.
By understanding the benefits and limitations of these devices, doctors can help their patients most effectively. Understanding the risks of these devices helps to ensure patient safety. Discuss the nuances of permanent versus retrievable filter with your physician if you or a loved one require one of these safety nets.
For an expanded discussion and explanation of IVC filters, please click here for a useful eMedicine article.