The patent's assignee is
News editors obtained the following quote from the background information supplied by the inventors: "The present invention pertains generally to the field of vascular filters for capturing embolic material in the blood flow. More particularly, the present invention relates to withdrawal of a temporary vena cava filter ('VCF') disposed near the distal end of a catheter having a catheter body and an outer sheath concentrically disposed over the catheter body.
"The accepted standard of care for patients with venous thromboembolism (VTE) is anticoagulant therapy. Inferior vena cava (IVC) filters are reserved for those patients who fail anticoagulant therapy, or have a complication or contraindication to anticoagulant therapy. Until the early 1970's, the only method of IVC interruption was surgical, either by clipping, ligation, or plication. The first clinical experience of an endoluminally-placed device to interrupt IVC flow was reported by Mobin-Uddin et al. in 1969. However, it was not until the introduction of a stainless steel umbrella-type filter by Greenfield et al. in 1973 that an effective method of endoluminally trapping emboli while simultaneously preserving IVC flow became possible. Indeed, for many years, the Greenfield filter set a benchmark by which newer filters were measured. Early generations of filters were inserted by surgical cut-down and venotomy. Eventually filters were able to be inserted percutaneously: initially through large 24 Fr sheaths, though newer generations of filters are able to be delivered through 6 Fr systems.
"Despite the safety and efficacy of modern day filters, systemic anticoagulation remains the primary treatment for VTE. Either unfractionated or low molecular weight heparin followed by three months of oral anticoagulation in patients with proximal deep venous thrombosis (DVT) is approximately 94% effective in preventing pulmonary embolism (PE) or recurrent DVT. The routine placement of IVC filters in addition to anticoagulation in patients with documented DVT was investigated by Decousus et al. in a randomized trial. Decousus H, Leizorovicz A, Parent F, et al. A clinical trial of vena caval filters in the prevention of pulmonary embolism in patients with proximal deep-vein thrombosis. N Engl J Med 1998; 338:409-415. This study revealed that the use of a permanent filter in addition to heparin therapy significantly decreased the occurrence of PE within the first 102 days compared to those without a filter. However, no effect was observed on either immediate or long-term mortality, and by 2 years, the initial benefit seen in the group of patients with filters was offset by a significant increase in the rate of recurrent DVT.
"Despite the efficacy of anticoagulant therapy in the management of VTE, there are certain situations and conditions in which the benefits of anticoagulation are outweighed by the risks of instituting such a therapy. These include contraindications and complications of anticoagulant therapy. In such circumstances, there may be absolute or relative indications for filter insertion.
"Currently, there are eight different types of permanent cava filters that are
"Well-founded concerns over the long-term complications of permanent IVC filters, particularly in younger patients in need of PE prophylaxis with a temporary contraindication to anticoagulation, has led to the development of temporary and retrievable filters. Temporary filters remain attached to an accessible transcutaneous catheter or wire. These have been used primarily in
"Currently no consensus exists as to which patients have an indication for a retrievable filter. However, it is generally accepted that patients at high risk for pulmonary embolism or with documented PE and with a temporary contraindication to anticoagulation are candidates.
"Certain circumstances preclude the placement of a filter in the infrarenal IVC. This includes thrombus extending into the infrarenal IVC, renal vein thrombosis or pregnancy. The safety of suprarenal placement of IVC filters is well documented, with no reported instances of renal dysfunction and no differences in the rates of filter migration, recurrent PE or caval thrombosis.
"The rate of upper extremity DVT is on the rise. This is predominantly due to an increasing number of patients having short- and long-term upper extremity catheters. In one study, 88% of patients found to have an upper extremity DVT had a central venous catheter present at the site of thrombosis at the time of diagnosis or within the previous two weeks. Pulmonary embolism may complicate upper extremity DVT in 10-16% of cases. In patients who have such a complication or contraindication to anticoagulation, a filter can be safely placed immediately below the confluence of the brachiocephalic veins. However, misplacement of an SVC filter is theoretically more likely than with an IVC filter because of the relatively short target area for deployment.
"The most common imaging modality used for filter insertion is fluoroscopy, performed either in an interventional suite or an operating room. Bedside placement of filters has inherent advantages, particularly for critically ill patients in intensive care settings where transport can be avoided. Portable fluoroscopy, surface duplex ultrasound and intravascular ultrasound (IVUS) have all been used to assist with bedside filter placement.
"VCF placement frequently occurs concomitantly with central access line placement or in critically ill patients that already have a central access line in place. Heretofore, however, there have been few devices which combine the function of a central access catheter and a removable VCF. Examples of a catheter coupled to a VCF that is useful both as a central venous access catheter for administration of intravenous fluids, bioactive agents, contrast agents, flushing agents, pressurized fluids for mechanical thrombolysis and/or withdrawal of blood samples and for capture of thrombus or emboli are presented in U.S. patent application Ser. No. 11/849,225, filed
As a supplement to the background information on this patent application, NewsRx correspondents also obtained the inventor's summary information for this patent application: "In one aspect of the present invention there is provided a temporary venous filter retrieval apparatus, comprising a first sheath for establishing access to a patient's blood vessel and a second sheath deliverable through a lumen of the first sheath and of sufficient diameter to capture a wholly or partially uncollapsed venous filter residing with a patient's vasculature.
"In accordance with another aspect of the present invention there is provided a method for retrieving a vena cava filter in use at a treatment site which consists of delivering a retrieval sheath concentrically over a catheter attached to the vena cava filter, the retrieval sheath being capable of enveloping a wholly or partially uncollapsed vena cava filter there within for removal from the patient.
"The present invention may be configured for either a femoral approach or a jugular approach to the inferior vena cava. VCFs are typically deployed infrarenaly, but may also be deployed suprarenaly. It will be understood that within the inferior vena cava blood flow is superior, i.e., toward the patients head. Thus, in all embodiments, the VCF will be positioned so that it opens inferiorly, i.e., away from the patient's head and toward the direction of the blood flow. It will be appreciated, therefore, that in the present invention, the VCF will have a different axial orientation on the central access catheter depending upon whether the device is intended for use in a femoral approach or a jugular approach.
"Regardless of the axial orientation of the VCF, embolic material captured within the VCF may be of sufficient size so as to inhibit the filter from being fully collapsed for withdrawal through the outer sheath. Thus, there exists the potential need for retrieval of the VCF via an alternative to the outer sheath.
BRIEF DESCRIPTION OF THE DRAWINGS
"FIG. 1A is a side elevational view of an exemplary catheter with a VCF in an unexpanded state.
"FIG. 1B is a side elevational view of the exemplary catheter of FIG. 1A with the VCF in an expanded state.
"FIG. 1C is an expanded view of the distal end of the catheter of FIG. 1B.
"FIG. 2 is an illustration of the use of an introducer sheath at a treatment site.
"FIG. 3 is an illustration of embolus captured within a VCF.
"FIG. 4A is an illustration of a step in an alternative method of VCF retrieval.
"FIG. 4B is an illustration of another step in an alternative method of VCF retrieval.
"FIG. 4C is an illustration of a further step in an alternative method of VCF retrieval.
"FIG. 4D is an illustration of yet another step in an alternative method of VCF retrieval.
"FIG. 4E is an illustration of a still further step in an alternative method of VCF retrieval.
"FIG. 4F is an illustration of another step in an alternative method of VCF retrieval.
"FIG. 4G is an illustration of yet another step in an alternative method of VCF retrieval.
"FIG. 4H is an illustration of a further step in an alternative method of VCF retrieval.
"FIG. 4I is an illustration of yet a further step in an alternative method of VCF retrieval."
For additional information on this patent application, see: Steinmetz, Jeffrey N. Temporary Filter Retrieval Apparatus and Method. Filed
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