The May issue of Vascular Disease Management features clinical review, case reports, and an interview. In their paper, “Vena Cava Filters: Too Often, Too Many or Just Right?” Drs. Kumar and Slovut provide an excellent review of the science and increased utilization of vena cava filters in contemporary practice. They appropriately note that there is profound discrepancy in the use of these devices among physicians and a paucity of level-1 evidence from randomized trials. They cite the complications, particularly late increased risk of subsequent deep venous thrombosis.
Pulmonary emboli are a massive health issue and a common cause of death, particularly in hospitalized patients. The source of these emboli are usually thrombus in the veins of the lower extremities. Large thrombus burden in the ileofemoral veins poses the greatest risk of fatal pulmonary emboli. Predisposing risk factors include hyperthrombogenicity, stasis, and injury as described by Virchow in the 19th century. Unfortunately many fatal emboli occur with little or no obvious warning signs. Despite adoption of in-hospital measures aimed at lessening the risk of developing deep venous thrombosis (compression hose and antithrombotic medications when not contraindicated), pulmonary embolus has remained one of the leading causes of death in hospitalized patients and is a common cause of sudden death in the general population. Although anticoagulants such as heparin and warfarin (as well as many newer anticoagulants) have been helpful in lessening thromboembolic complications, these agents aren’t universally successful in preventing pulmonary emboli and are not tolerated by patients with bleeding disorders or extensive injuries.
Surgical ligation of the IVC was shown to be effective at decreasing pulmonary emboli in high-risk patients having active recurrent pulmonary emboli but was limited by procedural risk and morbidity. The introduction of percutaneous filter devices provided a far less morbid means by which a barrier to clot migration could be achieved. Unfortunately filters are not benign. They are innately thrombogenic and multiple studies have reported an increased risk of filter thrombosis, leg DVT (most commonly on the side from which the filter was placed with femoral access), filter migration, and filter erosion through the wall of the vena cava. Subsequent development of retrievable filters expanded the use of filters in high-risk patients, as there was potential to remove the filter after the risk of embolus declined. It was reasoned that this could decrease the incidence of these complications. Although the majority of filters placed today are designed to be retrievable, at least half are never removed.
Cost is an issue, especially because there are no clear guidelines and very little data on cost-benefit ratio, particularly in some of the lower risk patients. Ethically evaluating cost and benefit could be impossible for some patients because of extreme mortality risk such as very limited pulmonary reserve and obvious “free-floating” iliofemoral thrombus, or borderline hemodymanics and proven PE with residual iliofemoral thrombus. There is agreement on the use of filters in patients who have DVT and where anticoagulation is contraindicated.
There have been improvements in filter design and methods of implantation and removal. Filters can be placed utilizing ultrasound guidance with no need for contrast. There has been a dramatic reduction in device delivery profiles. Perhaps it is appropriate at this time to evaluate outcomes utilizing different access sites. The most common complication of IVC filter placement is thrombosis of the femoral vein from which the filter was placed when a femoral approach is utilized. Would routine use of internal jugular vein access decrease this risk and decrease the risk of embolization of ileofemoral thrombus during insertion? Would routine filter removal diminish the risk of filter occlusion and filter erosion of the vena cava. Would careful measurement of the IVC diameter prior to filter placement diminish the risk of filter migration? Are there designs that are less thrombogenic or coatings that could lessen the possibility of filter thrombosis?
We need to perfect the science and the art of filter placement and work toward a better understanding of the indications.