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The Greenfield Vena Cava Filter is a small metal device designed to protect against a life threatening condition called pulmonary embolism. The filter is permanently implanted in a large vein, called the vena cava. As you can see, the filter has six legs that are joined together at the top forming a cone. It is this unique shape that allows the Greenfield Filter to effectively protect against pulmonary embolism while allowing blood to flow through it. Since its introduction in 1972, over 125,000 patients have had a Greenfield Vena Cava Filter implanted to protect them from pulmonary embolism. Why do I need a Greenfield Vena Cava Filter? If you have been diagnosed with deep vein thrombosis (DVT), a condition in which blood clots (thrombi) form in the veins of the leg, you may need a Greenfield? Vena Cava Filter. Veins are blood vessels that return blood to the heart. Any factor that promotes blood clotting can put an individual at risk for DVT. For example, prolonged immobility causes blood to pool in the veins of the legs, increasing the chance of clot formation. Likewise, an underlying medical condition, injury, certain diseases and some drugs may alter the body's normal blood clotting mechanism. A potentially serious complication of DVT is pulmonary embolism. The process of pulmonary embolism begins when a clot in the leg suddenly dislodges. The clot, now called an embolus, travels through the veins and into the vena cava. This is the large central vein that returns blood to the heart. The heart pumps the blood (and the embolus) received from the vena cava into the pulmonary artery which carries it to the lungs. Because branches of the pulmonary artery are much smaller in diameter than the vena cava, the embolus can block the flow of blood to the lungs. Pulmonary embolism can be life threatening because the body's oxygen supply can be cut off. In most cases, patients with DVT are given drugs called anticoagulants to prevent pulmonary embolism. These drugs slow down blood clotting. However, some patients cannot take these drugs because the risk of bleeding is too high or the drugs prove ineffective. These patients require alternate means of protection from pulmonary embolism. How does the Greenfield Vena Cava Filter work? The Greenfield Filter is permanently implanted in the vena cava where it prevents pulmonary embolism by capturing blood clots (emboli) before they can be transported to the lung. When an embolus enters the cone-shaped Greenfield Filter, it is directed toward the center of the filter and trapped. The Greenfield Filter is designed to allow adequate blood flow around the captured clot. Over time, a natural process called clot lysis will dissolve the trapped embolus. How does the doctor implant the Greenfield Vena Cava Filter? The doctor uses a specially designed system to place the filter. This system is introduced through either a vein in the groin or the neck and then guided to the vena cava. When the doctor releases the filter from the introducer system, the hooks at the base of the legs attach securely to the wall of the vena cava permanently implanting the filter. Can the Greenfield Filter become clogged? In rare instances, the filter may trap an embolus large enough to obstruct the flow of blood through it. However, the Greenfield Filter is designed to provide blood flow even when almost entirely filled with clot. The continuous flow of blood helps the body's natural process of clot lysis dissolve the trapped clot. Leg swelling may indicate that an embolus has obstructed blood flow through the filter. If you experience unusual, new leg swelling, contact your doctor immediately. Should I restrict my activities? Once the filter is in place, you will not be aware if its presence. The filter should not limit your normal activities in any way. Simply follow your doctor's advice about resumption of activity. Can my body reject the Greenfield Filter? No. The Greenfield Filter is made of a metal that has been used for years to make surgical implants such as hip, knee and heart valve replacements. Do I need any medication because of the Greenfield Filter? No. However, your doctor may prescribe an anticoagulant such as Coumadin® or aspirin if you are at continued risk for DVT. The Greenfield Filter protects you from pulmonary embolism but does not treat the underlying process of DVT. Does the Greenfield Filter have to be changed periodically? No. The Greenfield Filter is a permanent implant. Its design promotes the normal process of clot lysis. Therefore, captured clots will be naturally dissolved by the body. Will I have to go to the doctor more often because of the Greenfield Filter? Your doctor will determine how often you need to be seen. Typically, patients with filters have periodic examinations to check the position of the filter and the flow of blood through it. This can be done with X-ray and ultrasound examinations. You should tell any doctor not familiar with your case that you have a filter in place. Will my Greenfield Filter set off a metal detector? No. The amount of metal is not large enough to activate metal detectors. Will I be able to have an M.R.I. exam? Yes. The filter in no way precludes you from having an M.R.I.. However, you should tell the doctor ordering the exam that you have a filter in place.