The present invention pertains to thrombus filters. In particular, the present invention relates to thrombus filters which can be securely affixed at a selected location in the vascular system and removed when no longer required.
In recent years, pulmonary embolism has become an increasingly common medical emergency. Pulmonary embolisms may be caused by venous thrombosis, which in turn may be caused by blood flow retention, venous intima damage or coagulation abnormalities. Emergency or prophylactic treatments for these conditions includes anti-coagulant therapy, thrombolytic therapy, thrombectomy and inferior vena cava blocking procedures.
Among these therapeutic options, when an inferior vena cava blocking procedure is selected, one option is to perform a laparotomy under general anesthesia during which the inferior vena cava is ligated, sutured and shortened, or clipped. A laparotomy however, requires a general anesthetic and is susceptible to thrombosis formation due to the discontinuation of anti-coagulate therapy prior to surgery. Another option is to intravenously insert a thrombus filter into the inferior vena cava which requires a local anesthetic. Percutaneous filter insertion is now widely employed since it requires only a local anesthetic. However, such filters become affixed in the inner vena cava wall by neointimal hyperplasia within two or three weeks after being implanted, after which they cannot be removed percutaneously.
Prior thrombus filters which may be removed percutaneously have included generally linear or column-like struts which tend to transfer forces along the longitudinal axis of the struts. If the vessel is compressed asymmetrically, the filter elongates forcing the struts into the vessel wall which may damage the vessel.