Inferior Vena Cava Filters, May-Thurner Syndrome, and Vein Stents

What Is an IVC Filter? What Is Its Purpose? Patients who have a blood clot in their leg, referred to as deep vein thrombosis (DVT), are at risk of the clot breaking off and traveling toward the lung. It gets to the lung via the big vein in the abdomen (Figure 1), called the inferior vena cava (IVC). The traveling clot is called an embolus. Once it reaches the lung (after having passed through the right chambers of the heart) and becomes lodged in the lung, it is called a pulmonary embolism (PE). A filter can be inserted into the IVC (Figure 1) to catch and trap a traveling clot, preventing it from reaching the lung. Such filters used to be called Greenfield filters, but a variety of differently shaped filters now exist, so a more generic and better term is IVC filter. Filters can be nonremovable and thus are permanent, or they can be removable and thus can be left in for only a few weeks or months. Figure 1. The main image shows a filter in the big vein in the abdomen, preventing a clot that breaks off a deep vein thrombosis from reaching the lung. The traveling clot gets caught in the filter, thus protecting the lung. Some filters have a hook at their top (oval inset), allowing them to be removed with a catheter once they are not needed any more; these are called removable or transient inferior vena cava filters. ### How Is an IVC Filter Placed? Filters are typically placed by a radiologist or vascular surgeon or cardiologist through a vein in either the neck or the groin and then deployed via a catheter into the correct position in the IVC (Figure 1). The placement itself is relatively straightforward and takes only 10 to 15 minutes. Together with preparations, the procedure may take 30 to 45 minutes; it can be done as …