Caval filter is also known as inferior vena cava filter. It is an artificially produced device, which is protecting its "wearer" against pulmonary embolism. They are commonly used in patients at high risk of pulmonary embolism when there is no other solution.
The filter looks like a small "net", which is capable of capturing blood clots in the bloodstream (emboli). This net is implanted into the inferior vena cava by an endoscopic procedure. The most common source of such blood clots is the deep vein thrombosis of the lower extremities. When such thrombus tears off, it may travel into the inferior vena cava and through the right side of the heart into the lung blood vessels.
The implantation of the filter requires puncture of a major vein (usually femoral or jugular vein), which is used for inserting a catheter, which deploys the caval filter to the desired area. The filters may be either permanent, or temporary. Temporary filters should be removed within few weeks after their insertion.
A patient was hospitalized for swollen lower limb with extensive deep vein thrombosis. Anticoagulation therapy has been introduced. However, during further examination, suspected ovarian tumor has been found. Due to the need of surgical treatment, the anticoagulation therapy had to be temporarily discontinued. The current risk of pulmonary embolism in this period required the implantation of a temporary caval filter. The endovascular procedure was successfully performed and the affected ovary has been removed. Fortunately, histological examination found that the tumor was benign. After surgery, the caval filter was removed and the anticoagulation therapy has been again introduced.
The filters are typically used in patients with deep vein thrombosis (with- or without contemporary pulmonary embolism), where the anticoagulant agents can not be used. Quite advantageous is the temporary inferior vena cava filter in a patient with deep vein thrombosis, who has to undergo a major surgical intervention (and can not be anticoagulated).
The puncture of a major vein may be associated with bleeding. The caval filter may loosen and travel with the bloodstream into the heart and it may also become a source of new blood clots, because it is a foreign material. When we leave the temporary filter in the vein for too long, it may grow into the venous wall and its removal can cause serious injury of the inferior vena cava.
Caval filter is not used so often as classical anticoagulation therapy. If the pharmacotherapy is inefficient or can not be used, the caval filter is a very effective method of protecting the patient against pulmonary embolism.