The stainless steel Greenfield filter (Fig. 32.1), introduced in 1972 and deployed using an open venotomy and 24 French sheath, was the first successful endoluminal caval interruption device. Although the Mobin–Udin filter preceded the Greenfield filter, it was plagued by IVC thrombosis and its use was abandoned [25]. The Greenfield IVC filter consists of a cone of six steel wires ending in tethering, recurved hooks. The conical design of the Greenfield filter allows for two-thirds of the filter cone could be filled with thrombus while leaving 50% of the caval diameter patent [26]. This allows for a large amount of thrombus to be captured within the filter without impeding flow through the caval and around the captured thrombus and promotes the native fibrinolytic system to lyse the clot. Percutaneous introduction techniques evolved 12 years later, followed by a proliferation of other devices including deviations from the conical filter design, lower-profile devices, and ultimately retrievable filters.

An ideal filter would be securely fixed within the vena cava , biocompatible, non-thrombogenic, low profile, easy to deploy and retrieve, and have a low complication rate. While newer devices have some of these characteristics, the perfect filter does not exist. Retrievable devices must be less secure than permanent filters. Access-related complications persist, despite lower-profile deployment systems. Caval thrombosis, recurrent PE, and fracture are still major concerns to be dealt with. Table 32.2 depicts features of an ideal IVC filter.

Once indications are confirmed and the decision made to place a filter, preparation includes a thorough physical exam, review of basic laboratory data, and evaluation of pertinent imaging. With few exceptions, inferior vena cava filters should be placed with the intent for removal; however, all currently available temporary filters carry approval for permanent use. Access for an infrarenal filter is most easily obtained via the right common femoral vein, as this provides the most direct route for device deployment and comfort for the operator. If right common femoral venous access is precluded, the right internal jugular vein is a reasonable second choice. The left common femoral vein, although feasible, is less desirable as the left common iliac vein drains into the IVC via an acute angle which may direct the filter delivery system into the right lateral wall of the inferior vena cava , causing the filter to tilt. Lab data, including creatinine and a coagulation profile, should be obtained. Anticoagulation should be held for 2–4 h prior to the procedure. Imaging, including venous duplex studies, CT venogram, or MRV, should be reviewed with specific attention focused on determining patency of the iliofemoral veins and vena cava. If computed tomography or magnetic resonance imaging is available in the preoperative period, these studies may help delineate anatomic features of the inferior vena cava which may alter the surgical plan by identifying the location of the renal veins, caval diameter, the presence of a circumaortic or retroaortic left renal vein , or duplicated IVC.

The IVC develops between the 6th and 8th week of gestation from growth and regression of three paired cardinal veins. Anatomic variants arise due to abnormalities in the process and become relevant in patients requiring a filter as their presence may necessitate alteration of the surgical plan in up to 3–15% of cases.

The common femoral vein is identified using ultrasound. Obtaining access over the femoral head is critical to facilitate gentle manual compression at the conclusion of the case. Overaggressive compression of the femoral vein has been cited as one possible cause for perioperative venous thrombosis. Appropriate position is confirmed by placing a clamp at the intended access site and shooting a spot view under fluoroscopy. The groin is then anesthetized, and a 2–3 mm skin incision is made with an 11-blade scalpel. The common femoral vein is percutaneously cannulated with a double-wall needle, and a soft wire (Glidewire, Bentson, or J-wire) is advanced into the IVC under continuous fluoroscopic guidance. A 10 cm No. 5 French sheath is then advanced over the wire, into the common femoral vein , using Seldinger’s technique . A flush catheter is then advanced over the wire and an iliocavogram obtained (Fig. 32.2). At this point, the surgeon should take note of several key factors:

Occasionally, venacavogram may fail to clearly identify the renal veins. In this instance, the renal veins should be selectively catheterized and injected to eliminate any ambiguity in their location. Most available filters are 60 mm in length or shorter. The exception is the Bird’s Nest filter which is 80 mm in length.

Once the anatomy is confirmed and appropriate measurements are made, the device is opened and placed through the long delivery sheath which accompanies each filter. Although most IVC filters have similar deployment systems , each device has its own idiosyncrasies which the surgeon must consider. Deployment typically involves advancing the delivery sheath, under fluoroscopic guidance, to a point just below the lowest renal vein. Deploying the device as close to the renal veins as possible is important to avoid creating a low-flow zone above the filter and below the vein which could create a nidus for thrombosis outside the filter . The dilator and wire are then removed while precisely maintaining sheath position in the IVC. The filter is then inserted into the delivery sheath and advanced to the end of the sheath under fluoroscopic surveillance. To deploy the filter, the delivery system is immobilized with one hand, while the other pulls the sheath back. Most filters deploy fully with this technique, but some have additional steps to facilitate more precise delivery and to avoid tilting and uncontrolled forward advancement of the filter. Once deployed, completion venography is performed to document the final position and ensure patency of the IVC and renal veins (Fig. 32.3). The device delivery system is removed from the access point and manual compression is held to achieve hemostasis. A completion spot film is then obtained to document the final position of the IVC filter for future reference if needed.

Some patients may be poor candidates for fluoroscopically guided IVC filter placement due to clinical instability and inability to transfer to an operating room or have prohibitively elevated creatinine levels precluding the use of contrast media. Under such circumstances, placing an IVC filter is still possible with the aid of a portable intravascular ultrasound (IVUS) system brought to the bedside. IVUS allows for precise device deployment without the use of contrast, and data suggest that intravascular ultrasound measurements are more accurate than those obtained with traditional contrast venography, which tends to overestimate IVC diameter. Despite these advantages, there are several caveats to this technique. The learning curve is steep and rates of filter malposition range from 2 to 8%, attributable primarily to inexperience leading to misidentification of normal anatomy and failure to appreciate abnormal anatomy [27]. Familiarity with basic wires and IVUS interpretation is a prerequisite to any attempt at IVUS-guided IVC filter placement.