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Caval Filtration
Venous thromboembolism (VTE) is a significant cause of morbidity and mortality. The most feared condition is pulmonary embolism (PE) resulting from deep vein thrombosis (DVT) dislodging from the lower extremity or pelvis, or, less commonly from the upper extremity, embolizing to the lungs. Nonfatal PE is diagnosed in approximately 400,000 to 630,000 patients per year in the United States with an additional 50,000 to 200,000 fatalities annually. Within the United States, DVT/PE is currently the number one cause of preventable hospital death. Anticoagulation is the first-line treatment and prophylaxis for PE.
Inferior vena cava (IVC) ligation and, subsequently, filtration was developed to prevent symptomatic PE via capturing clot and preventing emboli from reaching the pulmonary circulation. This idea of PE prevention is more than 100 years old. In 1874, John Hunter described femoral vein ligation to prevent PE. IVC interruption for PE prevention was performed as early as 1910, with Fredrick Trendelenburg performing IVC ligation in the setting of postpartum pelvic thrombophlebitis. IVC ligation was effective in preventing PE but was associated with a 14% operative mortality rate and a 33% risk of chronic venous stasis. Ligation was replaced by compartmentalization of the IVC with sutures, staples, or clips, thereby reducing venous stasis, but unfortunately, this technique did not improve operative mortality rate (12%). To reduce operative mortality, the first endoluminal filter, the Mobin-Uddin umbrella, was introduced in 1967. With a reverse cone design, use of the Mobin-Uddin device was terminated because of a 60% rate of IVC occlusion. The cone-shaped Greenfield filter marked the start of the current era of permanent IVC filters and remains in use. The first percutaneous placement of a Greenfield filter, rather than surgical exposure of the femoral or jugular vein, was reported in 1984. Since then, numerous devices designed for percutaneous insertion have been developed. In 2003, the Food and Drug Administration (FDA) approved a retrievable IVC filter, leading to a drastic rise in utilization in relation to the incidence of PE and DVT. In 2010, the FDA issued an advisory related to the morbidity and mortality associated with filter placement, directing physicians to follow all patients with IVC filters and to remove the filter when no longer clinically indicated. Since then there have been numerous lawsuits implicating doctors and device manufacturers related to IVC filters. In recent years there has been a subsequent marked decrease in filter utilization. In response to the FDA warning, IVC filter clinics have gained popularity to help increase retrieval rate.
Indications
The indication for caval filtration varies between major societal guidelines. The only universally agreed-upon indication for IVC filter placement is for the prevention of PE in patients with known VTE and a contraindication to anticoagulation. The Society of Interventional Radiology Guidelines also support placement in patients with VTE and complications from anticoagulation, failure of anticoagulation, and clot progression despite anticoagulation. Societal guidelines regarding IVC filter placement are depicted in Table 72.1 .
TABLE 72.1
Major Societal Guidelines for Inferior Vena Cava Filter Placement
| Society | Guideline |
|---|---|
| Society of Interventional Radiology |
|
| CHEST/American College of Chest Physicians |
|
| American Heart Association |
|
DVT , deep vein thrombosis; ICU , intensive care unit; IVC , inferior vena cava; PE , pulmonary embolism; VTE , venous thromboembolism.
Contraindications
There are very few contraindications for caval filtration. One absolute contraindication for an IVC filter is lack of a location to place the filter, for example occlusion or absence of the IVC. In these conditions blood returns to the heart through a collateral venous network that typically consists of multiple tortuous and small veins, preventing large blood clots from traveling to the pulmonary circulation. However, if a large collateral venous pathway develops over time, placement of a filter into the azygos or hemiazygos vein can be considered. A second absolute contraindication to percutaneous IVC filter placement is lack of access to the IVC in cases when all possible access sites—jugular, subclavian, and femoral veins—are occluded.
Coagulopathy or uncontrollable hemostasis is a relative contraindication for percutaneous procedures in general. However, because of the relatively small insertion profile (as low as 6F), the availability of jugular delivery systems, and the use of ultrasound-guided venous puncture, IVC filters can be safely placed in almost every patient. Other medical conditions that could interfere with IVC filter placement include allergy to iodinated contrast agents and/or renal insufficiency. Alternative contrast agents (gadolinium or CO 2 ) can be used in these patients, allowing safe filter placement. CO 2 venography before filter placement is safe and accurate in most patients and underestimated IVC diameter in only 3.3%. Although allergic reactions to IVC filters have been reported, this is rare. In patients with bacteremia, risks versus benefits should be considered; however, superinfection of the IVC filter is rare.
Controversial/Extended Indications
IVC filters may be placed in the prophylactic setting in patients without known PE or DVT but with significant risk factors. In the mid-2000s, there was rapid increase in IVC filter placement, with a tripling of the rate of prophylactic filter placement. Most prophylactic filters were placed in the setting of trauma; however. preoperative placement for bariatric, orthopedic, and spine surgery also occurred. Currently, only the Society of Interventional Radiology Guidelines support prophylactic placement.
Certain high-risk patients may also be reasonable candidates for IVC filter placement. These can be divided into three categories. First, patients with large burden of clot including iliocaval DVT and massive PE, especially in patients with limited cardiopulmonary reserve, may benefit from placement. Second, periprocedural placement before VTE intervention such as thrombolysis and thrombectomy can be considered. Third, IVC filters can be considered in patients with potential difficulties with anticoagulation including compliance or who are at high risk for anticoagulation-related complication.
Superior vena cava filter placement is safe and effective, but remains an off-label use. PE from an upper extremity DVT has a very low incidence, roughly 2%, and is likely clinically insignificant. The somewhat unclear benefit has to be weighed against the possible risk of superior vena cava filter placement, which includes cardiac tamponade.
Equipment
IVC filters can be divided into four categories: (1) permanent, (2) retrievable (optional or removable), (3) convertible, and (4) temporary. A permanent filter has no design features intended for removal. Retrievable filters are engineered with aspects allowing percutaneous removal. Currently, all retrievable IVC filters are FDA-approved for permanent filtration. Convertible filters remain within the IVC but have the ability to open and no longer provide filtration. Finally, temporary filters must be removed, and are typically tethered to an external catheter or wire. There are no studies comparing filters between or within categories for comparative effectiveness.
Filter selection is frequently secondary to operator preference and availability; however, some patient factors should be considered. The approved maximum IVC diameter is variable by device. Additionally, for patients requiring permanent filtration, the literature does suggest permanent IVC filters have a better long-term complication profile than retrievable filters and tend to be cheaper.
Technique
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