To The Editor:
I offer my views in response to the debate on IVC filters. Numerous papers have been published with varying degrees of scientific validity. I offer my perspective after many decades as a clotter.
The very premise that a foreign body can prevent clots is incompatible with Virchow’s triad of factors that result in thrombosis: stasis of blood flow, hypercoagulability, and endothelial injury. All of the facts about IVC filters fulfill his postulates: this is a foreign body in the circulation, it alters flow, damages the vessel wall as the prongs dig into the vessel wall (seen on CT scans), and increases “clottability” due to exposure of blood to a foreign surface.
Despite decades of arguing against the use of an IVC filter in a large number of patients in whom this device is currently continuing to be placed, the view that an IVC filter prevents blood clots is highly prevalent in many different classes of physicians. The IVC filter is often equated with an anticoagulant in the management of venous thromboembolism (VTE), so placement of the filter allows the patient to be discharged early – thus providing extra revenue for hospitals (i.e., the filter placement procedure, X-ray machine usage, and earlier discharge) and radiologists (i.e., placing and retrieving the filter).
Those who place IVC filters also argue that it will prevent a lawsuit in the event of a subsequent complication. When a patient is seen in the emergency room and an ultrasound for a blood clot is positive, the IVC filter is sometimes placed because the patient is routed from the ER to the interventional radiology department– before any legitimate hematology consult is obtained. Though this is done in the interest of saving time (and reducing length of stay), one really needs a hematologist with a focus on hemostasis to address this issue – not an oncologist who also doubles as a hematologist, as is common practice in some settings.
The most dangerous situation is one where the patient is in an intense hypercoagulable state, comprising a combination of inherited and acquired disorders. This is particularly true of heparin-induced thrombocytopenia and thrombosis (HITT), where the added insult of a foreign body is especially harmful. I have seen instances of patients who present with extensive thromboses and, after the IVC filter is placed, HITT accelerates, leading to venous gangrene of the lower extremity. HITT is still a frequently missed diagnosis, as is the development of thrombi proximal to the filter (an obvious source for PE).
I believe clot extension occurs due to the common practice of inadequate anticoagulation and a false feeling of security on the part of physicians placing these devices. The critical importance of and primacy of anticoagulation gets lost in this transaction.
There needs to be an aggressive campaign to educate individuals about the fundamentals of thrombosis care. The ever-rapid admission and discharge scenario currently in place does not allow much room for an informed debate that must, of necessity, involve a well-informed patient.
Finally, many interventional radiology physicians refuse to write a consult note – as they ought to – and simply feel they are doing a procedure ordered by a physician. They are often offended when I insist that they write a consult and obtain informed consent (including perforation, floating into the right atrium, perforation through the duodenum, and the fact that the filter does not obviate the need for proper anticoagulation) for a procedure that they perform.
—Rajalaxmi McKenna, MD
Southwest Medical Consultants
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