Removable vena cava filter for reduced trauma in collapsed configuration

Information

  • Patent Grant
  • 7699867
  • Patent Number
    7,699,867
  • Date Filed
    Monday, April 18, 2005
    19 years ago
  • Date Issued
    Tuesday, April 20, 2010
    14 years ago
Abstract
The present invention provides a removable vena cava filter for capturing thrombi in a blood vessel. The filter comprises a plurality of primary struts having first ends attached together along a longitudinal axis. Each primary strut has an arcuate segment extending from the first end to an anchoring hook. The primary struts are configured to move between an expanded state for engaging the anchoring hooks with the blood vessel and a collapsed state for filter retrieval or delivery. Each primary strut are configured to cross another primary strut along the longitudinal axis in the collapsed state such that the arcuate segments occupy a first diameter greater than a second diameter occupied by the anchoring hooks in the collapsed state for filter retrieval or delivery.
Description
BACKGROUND OF THE INVENTION

The present invention relates to medical devices. More particularly, the invention relates to a removable vena cava clot filter that can be percutaneously placed in and removed from the vena cava of a patient.


Filtering devices that are percutaneously placed in the vena cava have been available for over thirty years. A need for filtering devices arises in trauma patients, orthopedic surgery patients, neurosurgery patients, or in patients having medical conditions requiring bed rest or non-movement. During such medical conditions, the need for filtering devices arises due to the likelihood of thrombosis in the peripheral vasculature of patients wherein thrombi break away from the vessel wall, risking downstream embolism or embolization. For example, depending on the size, such thrombi pose a serious risk of pulmonary embolism wherein blood clots migrate from the peripheral vasculature through the heart and into the lungs.


A filtering device can be deployed in the vena cava of a patient when, for example, anticoagulant therapy is contraindicated or has failed. Typically, filtering devices are permanent implants, each of which remains implanted in the patient for life, even though the condition or medical problem that required the device has passed. In more recent years, filters have been used or considered in preoperative patients and in patients predisposed to thrombosis which places the patient at risk for pulmonary embolism.


The benefits of a vena cava filter have been well established, but improvements may be made. For example, filters generally have not been considered removable from a patient due to the likelihood of endotheliosis of the filter or fibrous reaction matter adherent to the endothelium during treatment. After deployment of a filter in a patient, proliferating intimal cells begin to accumulate around the filter struts which contact the wall of the vessel. After a length of time, such ingrowth prevents removal of the filter without risk of trauma, requiring the filter to remain in the patient. As a result, there has been a need for an effective filter that can be removed after the underlying medical condition has passed.


Moreover, conventional filters commonly become off-centered or tilted with respect to the hub of the filter and the longitudinal axis of the vessel in which it has been inserted. As a result, the filter including the hub and the retrieval hook engage the vessel wall along their lengths and potentially become endothelialized therein. This condition is illustrated in prior art FIG. 1a in which a prior art filter 113 has been delivered by a delivery sheath 125 through the vessel 150 of a patient. In the event of this occurrence, there is a greater likelihood of endotheliosis of the filter to the blood vessel along a substantial length of the filter wire. As a result, the filter becomes a permanent implant in a shorter time period than otherwise.


Furthermore, further improvements may be made related to the delivery or retrieval of vena cava filters. For delivery of vena cava filters, an introducer system having an introducer tube may be percutaneously inserted in the vena cava of a patient through the femoral vein or the jugular vein. A part of an introducer assembly 120 is illustrated in prior art FIG. 1b in which the prior art filter 113 is percutaneously delivered through the jugular vein 154 of a patient. As shown, the filter 113 in its collapsed configuration is placed at the distal end 121 of an inner sheath 122 with anchoring hooks 116 of the filter 113 extending past the distal end 121. An outer sheath 126 is then disposed over the inner sheath 122 to avoid undesirably scratching or scraping of the anchoring hooks 116 against the introducer tube 130. The inner and outer sheaths 122, 126 along with a pusher member 132 are then moved together through the introducer tube 130 to deliver the filter 113 to the vena cava of the patient.


It has been a challenge to design a vena cava filter with features that lessen the concerns of undesirably scratching or scraping of the anchoring hooks against outer walls of an introducer tube or a blood vessel while maintaining the effectiveness of the filter.


BRIEF SUMMARY OF THE INVENTION

One embodiment of the present invention generally provides a removable vena cava filter configured for simplified delivery to and retrieval from the vena cava of a patient. The filter is shaped for improved delivery and retrieval. The filter includes primary struts, each of which having an arcuate segment that extends to an anchoring hook. In a collapsed state, each primary strut is configured to cross another primary strut along a center axis of the filter such that the arcuate segments occupy a first diameter greater than a second diameter occupied by the anchoring hooks. As a result, the arcuate segments widen a path in a vessel when the filter is retrieved. Thus, the filter is able to be retrieved with greater ease and with a reduced likelihood of undesirably scratching or scraping of the anchoring hooks against outer walls of a blood vessel in the collapsed state.


The present invention provides a removable vena cava filter for capturing thrombi in a blood vessel. In one embodiment, the filter comprises a plurality of primary struts having first ends attached together along a longitudinal axis. Each primary strut has an arcuate segment extending from the first end to an anchoring hook. The primary struts are configured to move between an expanded state for engaging the anchoring hooks with the blood vessel and a collapsed state for filter retrieval or delivery. Each primary strut are configured to cross another primary strut along the longitudinal axis in the collapsed state such that the arcuate segments occupy a first diameter greater than a second diameter occupied by the anchoring hooks in the collapsed state for filter retrieval or delivery.


In another embodiment, the filter further comprises a plurality of secondary struts having connected ends attached together along the longitudinal axis and extending therefrom to free ends to centralize the filter in the expanded state in the blood vessel. The filter further comprises a hub configured to axially house the first ends of the plurality of primary struts. The filter further includes a retrieval hook extending from the hub opposite the plurality of primary struts for removal of the filter from the blood vessel.


In yet another embodiment, the present invention provides a removable filter assembly for capturing thrombi in a blood vessel. In this embodiment, the assembly comprises the removable filter and an introducer tube in which the removable filter in the collapsed state is disposed for retrieval or delivery.


In certain embodiments, pairs of secondary struts are positioned between pairs of primary struts. Each pair of secondary struts is twisted together near the connected ends of the secondary struts to form a twisted section. The twisted sections of the secondary struts effectively stiffen the struts to enhance their centering capabilities to prevent the filter from tilting when the filter is deployed in the blood vessel. Hence, engagement between the struts and the blood vessel is minimized which reduces the potential for the struts to become endothelialized within the blood vessel. A further feature of the twisted sections is that they prevent or at least minimize the secondary struts from entangling with the primary struts.


Further aspects, features, and advantages of the invention will become apparent from consideration of the following description and the appended claims when taken in connection with the accompanying drawings.





BRIEF DESCRIPTION OF THE DRAWINGS


FIG. 1
a is a side view of a prior art filter deployed through the vasculature of a patient;



FIG. 1
b is a side view of an introducer assembly including the prior art filter to be delivered to the vena cava of a patient;



FIG. 2 is an illustration of the anatomy of the renal veins, the iliac veins, and the vena cava in which one embodiment of a vena cava filter of the present invention is deployed;



FIG. 3
a is a side perspective view of one embodiment of the vena cava filter in an expanded state;



FIG. 3
b is a side view of the vena cava filter of FIG. 3a in a collapsed state and disposed in an introducer tube;



FIG. 4 is an enlarged view of a portion of a second arcuate portion of a primary strut of the vena cava filter;



FIG. 5 is a cross-sectional view of a hub of the filter in FIG. 3 taken along line 5-5;



FIG. 6
a is a cross-sectional view of the vena cava depicting the filter partially deployed leading with the removal hook;



FIG. 6
b is a cross-sectional view of the vena cava depicting the filter partially deployed leading with the anchoring hooks;



FIG. 7 is a cross-sectional view of the vena cava in which the filter of FIG. 3 has been deployed;



FIG. 8
a is a cross-sectional view of the vena cava of FIG. 7a taken along line 8-8;



FIG. 8
b is a cross-sectional view of the vena cava of FIG. 7a taken along line 8-8 depicting another embodiment of the filter;



FIG. 9
a is a cross-sectional view of a blood vessel in which a retrieval sheath engages primary struts of the filter in FIG. 3 for removal;



FIG. 9
b is a cross-sectional view of a blood vessel in which the retrieval sheath includes the filter in the collapsed state for removal;



FIG. 10 is a cross-sectional view of a blood vessel showing a vena cava filter deployed within the blood vessel in accordance with another embodiment of the invention; and



FIG. 11 is a view of the blood vessel and filter of FIG. 10 taken along the line 11-11.





DETAILED DESCRIPTION OF THE INVENTION

In accordance with one embodiment of the present invention, FIG. 2 illustrates a vena cava filter 10 implanted in the vena cava 50 for the purpose of lysing or capturing thrombi carried by the blood flowing through the iliac veins 54, 56 toward the heart and into the pulmonary arteries. As shown, the iliac veins merge at juncture 58 into the vena cava 50. The renal veins 60 from the kidneys 62 join the vena cava 50 downstream of juncture 58. The portion of the vena cava 50, between the juncture 58 and the renal veins 60, defines the inferior vena cava 52 in which the vena cava filter 10 has been percutaneously deployed through the femoral veins. Preferably, the vena cava filter 10 has a length smaller than the length of the inferior vena cava 52. If the lower part of the filter extends into the iliac veins, filtering effectiveness will be compromised and if the filter wires cross over the origin of the renal veins the filter wires might interfere with the flow of blood from the kidneys.


This embodiment of the present invention will be further discussed with reference to FIGS. 3-9 in which filter 10 is shown. FIG. 3a illustrates filter 10 in an expanded state and comprising four primary struts 12 each having first ends that emanate from a hub 11. Hub 11 attaches by crimping first ends 14 of primary struts 12 together at a center point A in a compact bundle along a central or longitudinal axis X of the filter. The hub 11 has a minimal diameter for the size of wire used to form the struts. Preferably, the primary struts 12 are formed from a superelastic material, stainless steel wire, Nitinol, cobalt-chromium-nickel-molybdenum-iron alloy, or cobalt chrome-alloy, or any other suitable material that will result in a self-opening or self-expanding filter. In this embodiment, the primary struts 12 are preferably formed from wire having a round cross-section with a diameter of at least about 0.015 inches. Of course, it is not necessary that the primary struts have a round or near round cross-section. For example, the primary struts 12 could take on any shape with rounded edges to maintain non-turbulent blood flow therethrough.


Each primary strut 12 includes an arcuate segment 16 having a soft S-shape. Each arcuate segment 16 is formed with a first curved portion 20 that is configured to softly bend away from the longitudinal or central axis X of the filter 10 and a second curved portion 23 that is configured to softly bend toward the longitudinal axis of the filter 10. Due to the soft bends of each arcuate segment 16, a prominence or a point of inflection on the primary strut 12 is substantially avoided to aid in non-traumatically engaging the vessel wall.


The primary struts 12 terminate at anchoring hooks 26 that will anchor in the vessel wall when the filter 10 is deployed at a delivery location in the blood vessel. The primary struts 12 are configured to move between an expanded state for engaging the anchoring hooks 26 with the blood vessel and a collapsed state or configuration for filter retrieval or delivery. In the expanded state, each arcuate segment 16 extends arcuately along a longitudinal axis X (as shown in FIG. 3a) and linearly relative to a radial axis R (as shown in FIG. 8a) from the first end 14 to the anchoring hook 26. As shown in FIG. 8a, the primary struts 12 radially extend from the first ends 14, defining the radial axis R. In this embodiment, the primary struts 12 extend linearly relative to the radial axis R and avoid entanglement with other struts.


As discussed in greater detail below, the soft bends of each arcuate segment 16 allow each primary strut 12 to cross another primary strut 12 along the longitudinal axis X in the collapsed state such that each anchoring hook 26 faces the longitudinal axis X for filter retrieval or delivery.


When the filter 10 is deployed in a blood vessel, the anchoring hooks 26 engage the walls of the blood vessel to define a first axial portion to secure the filter in the blood vessel. The anchoring hooks 26 prevent the filter 10 from migrating from the delivery location in the blood vessel where it has been deposited. The primary struts 12 are shaped and dimensioned such that, when the filter 10 is freely expanded, the filter 10 has a diameter of between about 25 mm and 45 mm and a length of between about 3 cm and 7 cm. For example, the filter 10 may have a diameter of about 35 mm and a length of about 5 cm. The primary struts 12 have sufficient spring strength that when the filter is deployed the anchoring hooks 26 will anchor into the vessel wall.


In this embodiment, the filter 10 includes a plurality of secondary struts 30 having connected ends 32 that also emanate from hub 11. Hub 11 attaches the connected ends 32 by crimping at the center point A of the secondary struts 30 together with the primary struts 12. In this embodiment, each primary strut 12 has two secondary struts 30 in side-by-side relationship with the primary strut 12. The secondary struts 30 extend from the connected ends 32 to free ends 34 to centralize the filter 10 in the expanded state in the blood vessel. As shown, each secondary strut 30 extends arcuately along the longitudinal axis and linearly relative to the radial axis from the connected end 32 to the free end 34 for engaging the anchoring hooks 26 with the blood vessel. As with the primary struts 12, the secondary struts 30 extend linearly relative to the radial axis and avoid entanglement with other struts.


The secondary struts 30 may be made from the same type of material as the primary struts 12. However, the secondary struts 30 may have a smaller diameter, e.g., at least about 0.012 inches, than the primary struts 12. In this embodiment, each of the secondary struts 30 is formed of a first arc 40 and a second arc 42. The first arc 40 extends from the connected end 32 away from the longitudinal axis X. The second arc 42 extends from the first arc 40 towards the longitudinal axis X. As shown, two secondary struts 30 are located on each side of one primary strut 12 to form a part of a netting configuration of the filter 10. The hub 11 is preferably made of the same material as the primary struts and secondary struts to minimize the possibility of galvanic corrosion or molecular changes in the material due to welding.


When freely expanded, free ends 34 of the secondary struts 30 will expand radially outwardly to a diameter of about 25 mm to 45 mm to engage the vessel wall. For example, the secondary struts 30 may expand radially outwardly to a diameter of between about 35 mm and 45 mm. The second arcs 42 of the free ends 34 engage the wall of a blood vessel to define a second axial portion where the vessel wall is engaged. The secondary struts 30 function to stabilize the position of the filter 10 about the center of the blood vessel in which it is deployed. As a result, the filter 10 has two layers or portions of struts longitudinally engaging the vessel wall of the blood vessel. The length of the filter 10 is preferably defined by the length of a primary strut 12.


Furthermore, the diameter of the hub 11 is defined by the size of a bundle containing the primary struts 12 and secondary struts 30. In this embodiment, the eight secondary struts 30 minimally add to the diameter of the hub 11 or the overall length of the filter 10, due to the reduced diameter of each secondary strut 30. This is accomplished while maintaining the filter 10 in a centered attitude relative to the vessel wall and formed as a part of the netting configuration of the filter 10. As shown, removal hook 46 extends from hub 11 opposite primary and secondary struts 12 and 30.


In this embodiment, each arcuate segment 16 has a thickness of at least about 0.015 inch and a tensile strength of between about 285,000 pounds per square inch (psi) and 330,000 psi. Each anchoring hook 26 is integral with the arcuate segment 16 and has the thickness and the tensile strength of the arcuate segment. Each secondary strut 30 has a thickness of at least about 0.012 inch and a tensile strength of between about 285,000 psi and 330,000 psi.



FIG. 3
b illustrates the filter 10 in a collapsed state disposed in a delivery/retrieval tube 94 for delivery or retrieval. As shown, the filter 10 is shaped for each primary strut 12 to cross another primary strut 12 along the longitudinal axis X. As a result, in the collapsed state, the anchoring hooks 26 are configured to invert or inwardly face the longitudinal axis X for retrieval and delivery of the filter 10. This inverted or inwardly facing configuration of the anchoring hooks 26 allows for simplified delivery and retrieval of filter 10. For example, a concern that the anchoring hooks 26 may scrape, scratch, or tear the inner wall of a delivery/retrieval tube is eliminated, since the filter 10 of the present invention is shaped to have the anchoring hooks 26 face each other in the collapsed state. In fact, a set of inner and outer delivery/retrieval sheaths (see prior art FIG. 1b) may be eliminated during the delivery or retrieval of the filter 10 through the jugular or femoral vein. Rather, merely one delivery/retrieval tube with a loop snare mechanism may be used to deliver or retrieve the filter 10 of the present invention.


In the collapsed state, each primary strut 12 is configured to cross another primary strut 12 along the longitudinal axis X such that the arcuate segments 16, first curved portions 20 or second curved portions 23, occupy a first diameter D1. In this embodiment, the first diameter is greater than a second diameter D2 occupied by the anchoring hooks 26 for filter retrieval or delivery. It has been found that the first diameter of the arcuate segments 16 serves to clear a path of retrieval, reducing radial force from the sheath or blood vessel on the anchoring hooks 26 during removal of the filter 10 from a patient. Reducing the radial force on the anchoring hooks 26 assists in preventing the anchoring hooks 26 from scraping, scratching, or tearing the inner wall of a sheath during removal of the filter 10 from a patient.


In this embodiment of the present invention, it is to be noted that the filter 10 may be delivered or retrieved by any suitable introducer (delivery or retrieval) tube. However, it is preferred that the introducer tube has an inside diameter of between about 4.5 French and 16 French, and more preferably between about 6.5 French and 14 French. Thus, the collapsed state of the filter may be defined by the inside diameter of an introducer tube.



FIG. 4 illustrates primary strut 12 including distal bend 43 formed thereon and extending outwardly radially from the longitudinal axis X. As shown in FIG. 4, the distal bend 43 may extend outwardly at an angle between about 0.5 degree to 2 degrees, preferably 1.0 degree. The distal bend 43 allows the filter 10 to filter thrombi effectively at a smaller inside diameter of a blood vessel than otherwise would be possible while maintaining the ability to collapse for delivery or retrieval.



FIG. 5 illustrates a cross-sectional view of the filter 10 of FIG. 3a at hub 11. As shown, the hub 11 houses a bundle of first ends 14 of the four primary struts 14 and connected ends 32 of secondary struts 30. FIG. 5 further depicts the configurations of the primary and secondary struts 12 and 30. In this embodiment, the primary struts 12 are spaced between two secondary struts 30. Of course, the primary struts 12 may be spaced between any other suitably desired number of secondary struts 30 without falling beyond the scope or spirit of the present invention.


In this embodiment, FIGS. 6a and 6b both illustrate the filter 10 partially deployed in inferior vena cava 52. FIG. 6a shows the filter 10 being delivered by a delivery tube 48 through the femoral vein of a patient and FIG. 6b shows the filter 10 being delivered by a delivery tube 50 through the jugular vein of a patient. For deployment of the filter 10, a delivery tube is percutaneously inserted through the patient's vessel such that the distal end of the delivery tube is at the location of deployment. In this embodiment, a wire guide is preferably used to guide the delivery tube to the location of deployment. In FIG. 6a, the filter 10 is inserted through the proximal end of the delivery tube 48 with the removal hook 46 leading and anchoring hooks 26 of the primary struts 12 held by a filter retainer member for delivery via the femoral vein of a patient.


In FIG. 6b, the filter 10 is inserted through the proximal end of the delivery tube 50 with the anchoring hooks 26 of the primary struts 12 leading and the removal hook 46 trailing for delivery via the jugular vein of a patient. In this embodiment, a pusher wire having a pusher member at its distal end may be fed through the proximal end of the delivery tube 50 thereby pushing the filter 10 until the filter 10 reaches the distal end of the delivery tube 50 to a desired location.


During deployment, the secondary struts 30 expand first to centralize or balance the filter within the vessel. When the free ends of the secondary struts emerge from the distal end of either of the delivery tubes 48 or 50, the secondary struts 30 expand to an expanded position as shown in both FIGS. 6a and 6b. The second arcs 42 engage the inner wall of the vessel. The second arcs 42 of the secondary struts 30 function to stabilize the attitude of filter 10 about the center of the blood vessel. When delivering through the jugular vein (FIG. 6b), the filter 10 is then pushed further by the pusher wire (not shown) until it is fully deployed.


When the filter 10 is fully expanded in the vena cava, the anchoring hooks 26 of the primary struts 12 and the second arcs 42 of the secondary struts 30 are in engagement with the vessel wall. The anchoring hooks 26 of the primary struts 12 have anchored the filter 10 at the location of deployment in the vessel, preventing the filter 10 from moving with the blood flow through the vessel. As a result, the filter 10 is supported by two sets of struts that are spaced axially along the length of the filter.



FIG. 7 illustrates the filter 10 fully expanded after being deployed in inferior vena cava 52. As shown, the inferior vena cava 52 has been broken away so that the filter 10 can be seen. The direction of the blood flow BF is indicated in FIG. 7 by the arrow that is labeled BF. The anchoring hooks 26 at the ends of the primary struts 12 are shown as being anchored in the inner lining of the inferior vena cava 52. The anchoring hooks 26 include barbs 29 that, in one embodiment, project toward the hub 11 of the filter. The barbs 29 function to retain the filter 10 in the location of deployment.


The spring biased configuration of the primary struts 12 further causes the anchoring hooks 26 to engage the vessel wall and anchor the filter at the location of deployment. After initial deployment, the pressure of the blood flow on the filter 10 contributes in maintaining the barbs 29 anchored in the inner lining of the inferior vena cava 52. As seen in FIG. 7, the second arcs 42 of secondary struts 30 also have a spring biased configuration to engage with the vessel wall.


As seen in FIG. 7, the hub 11 and removal hook 46 are positioned downstream from the location at which the anchoring hooks 26 are anchored in the vessel. When captured by the struts 12 and 30, thrombi remains lodged in the filter. The filter 10 along with the thrombi may then be percutaneously removed from the vena cava. When the filter 10 is to be removed, the removal hook 46 is preferably grasped by a retrieval instrument that is percutaneously introduced in the vena cava in the direction of removal hook 16 first.



FIG. 8
a depicts a netting configuration or pattern formed by the primary struts 12, secondary struts 30, and the hub 11 relative to radial axis R. The netting pattern shown in FIG. 8a functions to catch thrombi carried in the blood stream prior to reaching the heart and lungs to prevent the possibility of a pulmonary embolism. The netting pattern is sized to catch and stop thrombi that are of a size that are undesirable to be carried in the vasculature of the patient. Due to its compacted size, the hub minimally resists blood flow.



FIG. 8
a depicts the netting pattern including primary struts and secondary struts at substantially equal angular space relative to each other. The netting pattern provides an even distribution between the primary and secondary struts to the blood flow, increasing the likelihood of capturing thrombi. However, as shown in FIG. 8b, it is to be understood that each of the sets of primary struts 312 and secondary struts 330 may be independently spaced substantially equally at their respective portions relative to radial axis R′. For example, the secondary struts 330 may be spaced equally relative to the other secondary struts 330 and the primary struts 312 may be spaced equally relative to the other primary struts 312. As a result, the netting pattern in this embodiment shown by the cross-sectional view of the vena cava (taken along line 8-8) will have uneven or unequal spacing between the primary struts 312 and secondary struts 330.



FIG. 9
a illustrates part of a retrieval device 65 being used in a procedure for removing the filter 10 from the inferior vena cava 52. In this example, the retrieval device 65 is percutaneously introduced into the superior vena cava via the jugular vein. In this procedure, a removal catheter or sheath 68 of the retrieval device 65 is inserted into the superior vena cava. A wire 70 having a loop snare 72 at its distal end is threaded through the removal sheath 68 and is exited through the distal end of the sheath 68. The wire 70 is then manipulated by any suitable means from the proximal end of the retrieval device such that the loop snare 72 captures the removal hook 46 of the filter 10. Using counter traction by pulling the wire 70 while pushing the sheath 68, the sheath 68 is passed over the filter 10. As the sheath 68 passes over the filter 10, the primary struts 12 and then the secondary struts 30 engage the edge of the sheath 68 and are caused to pivot or undergo bend deflection at the hub 11 toward the longitudinal axis of the filter. The pivoting toward the longitudinal axis causes the ends of the struts 12 and 30 to be retracted from the vessel wall. In this way, only surface lesions 74 and small point lesions 76 on the vessel wall are created in the removal procedure. As shown, the surface lesions 74 are created by the ends of the secondary struts 30 and the small point legions 76 are created by the anchoring hooks 26 of the primary struts 12. However, it is to be noted that any other suitable procedure may be implemented to remove the filter from the patient.


Although the embodiments of this device have been disclosed as preferably being constructed from wire having a round cross section, it could also be cut from a tube of suitable material by laser cutting, electrical discharge machining or any other suitable process.


The primary and secondary struts can be formed from any suitable material that will result in a self-opening or self-expanding filter, such as shape memory alloys. Shape memory alloys have the desirable property of becoming rigid, that is, returning to a remembered state, when heated above a transition temperature. A shape memory alloy suitable for the present invention is Ni—Ti available under the more commonly known name Nitinol. When this material is heated above the transition temperature, the material undergoes a phase transformation from martensite to austenite, such that material returns to its remembered state. The transition temperature is dependent on the relative proportions of the alloying elements Ni and Ti and the optional inclusion of alloying additives.


In other embodiments, both the primary struts and the secondary struts are made from Nitinol with a transition temperature that is slightly below normal body temperature of humans, which is about 98.6° F. Thus, when the filter is deployed in the vena cave and exposed to normal body temperature, the alloy of the struts will transform to austenite, that is, the remembered state, which for the present invention is an expanded configuration when the filter is deployed in the blood vessel. To remove the filter, the filter is cooled to transform the material to martensite which is more ductile than austenite, making the struts more malleable. As such, the filter can be more easily collapsed and pulled into the sheath for removal.


In certain embodiments, both the primary struts and the secondary struts are made from Nitinol with a transition temperature that is above normal body temperature of humans, which is about 98.6° F. Thus, when the filter is deployed in the vena cave and exposed to normal body temperature, the struts are in the martensitic state so that the struts are sufficiently ductile to bend or form into a desired shape, which for the present invention is an expanded configuration. To remove the filter, the filter is heated to transform the alloy to austenite so that the filter becomes rigid and returns to a remembered state, which for the filter is a collapsed configuration.


In another embodiment shown in FIGS. 10 and 11, a filter 420 includes four primary struts 438 and eight secondary struts 440 that extend from a hub 442. Each primary strut 438 terminates in an anchoring hook 452 with a barb 454. The primary struts 438 have sufficient spring strength such that when the filter is deployed in a vena cava 436, the anchoring hooks 452, in particular, the barbs 444, anchor into the vessel wall of the vena cava 436 to prevent the filter 420 from migrating from the delivery location. The pressure of the blood flow on the filter 420 contributes in maintaining the barbs 454 anchored in the inner lining of the vena cava 436.


A pair of secondary struts 440 are positioned between adjacent primary struts 438. Each secondary strut 440 extends from the hub 442 and terminates in a tip 462 pointing toward the central axis 444. The tips 462 are located longitudinally between the hub 442 and the anchoring hooks 454 of the primary struts 438. The connected ends of each pair of secondary struts 440 positioned between adjacent primary struts are twisted together, defining a twisted section 464.


Since the twisted sections 464 effectively stiffens each pair of secondary struts 440, thinner secondary struts may be used to provide the appropriate balancing forces to center the filter in the blood vessel. Moreover, an additional benefit of the twisted section is that they prevent the secondary struts from entangling with the primary struts.


The secondary struts 440 can be made from the same type of material as the primary struts 438 and can be formed by the same process used to form the primary struts. However, the secondary struts may have a smaller diameter than the primary struts. To form the twisted sections 464, each pair of secondary struts 440 positioned between adjacent primary struts 438 can be twisted about each other after the struts have been attached to the hub 442. Each twisted section 464 includes one or more twists. For example, each twisted section 464 may include up to about ten twists. In certain implementations, the number of twists in each section 464 may be between about three to five twists. Increasing the number of twists increases the stiffness of the pair of secondary struts twisted about each other. The hub 442 is preferably made of the same material as the primary struts and secondary struts to minimize the possibility of galvanic corrosion.



FIG. 11 illustrates a netting pattern (“net”) formed by the primary struts 438, the secondary struts 440, and the hub 442. This net functions to catch thrombi carried in the blood stream to prevent the thrombi from reaching the heart and lungs, where the thrombi could cause pulmonary embolism. The net is sized to catch and stop thrombi that are of a size that are undesirable in the vasculature of the patient. As illustrated, the struts 438 have substantially equal angular spacing between the struts.


The hub 442 and a removal hook 466 attached to the hub are located downstream of the location at which the anchoring hooks 452 are anchored in the vessel 436. When captured by the struts, thrombi remain lodged in the filter 420. The filter 420 along with the thrombi may then be removed percutaneously from the vena cava. When the filter 420 is to be removed, the removal hook 466 is typically grasped by the retrieval hook that is introduced in the vena cava percutaneously.


While the present invention has been described in terms of preferred embodiments, it will be understood, of course, that the invention is not limited thereto since modifications may be made to those skilled in the art, particularly in light of the foregoing teachings.

Claims
  • 1. A removable filter for capturing thrombi in a blood vessel, the filter comprising: a plurality of primary struts each having a first length, the primary struts having first ends attached together along a longitudinal axis and housed within a hub, wherein the primary struts emanate from a first end of the hub, each primary strut having an arcuate segment including a first curved portion extending from the first end and a second curved portion extending from the first curved portion and terminating at an anchoring hook, the first and second curved portions defining a soft-S shape, each primary strut extending arcuately along the longitudinal axis and linearly radially, the primary struts being configured to move between an expanded state for engaging the anchoring hooks with the blood vessel and a collapsed state for filter retrieval or delivery, each primary strut being configured to cross another primary strut along the longitudinal axis in the collapsed state such that the arcuate segments occupy a first diameter, the first diameter being the distance between opposite arcuate segments of the primary struts in the collapsed state, the first diameter being greater than a second diameter occupied by the anchoring hooks in the collapsed state for filter retrieval or delivery, the second diameter being the largest diameter occupied by the anchoring hooks in the collapsed state, each primary strut of the plurality of primary struts having a spring biased configuration that is self-expanding; anda plurality of secondary struts separate from the primary struts, the secondary struts having a second length and connected ends attached together along the longitudinal axis and housed within the hub, wherein the secondary struts emanate from the first end of the hub and extend arcuately therefrom to free ends to centralize the filter in the expanded state in the blood vessel, each secondary strut extending arcuately along the longitudinal axis and linearly radially, each secondary strut having a first arc extending from the connected end away from the longitudinal axis and a second arc extending from the first arc towards the longitudinal axis, the second arc extending to the free end without a hook, the secondary struts having a smaller diameter than the primary struts, wherein the length of the filter is defined by the first length of the primary struts.
  • 2. The removable filter of claim 1 further comprising: a retrieval hook extending from the hub opposite the plurality of primary and secondary struts for removal of the filter from the blood vessel.
  • 3. The removable filter of claim 1 wherein the first curved portion of each primary strut is configured to extend radially from the longitudinal axis of the filter and the second curved portion of each primary struts is configured to extend radially toward the longitudinal axis of the filter.
  • 4. The removable filter of claim 1 wherein each primary strut is formed of a superelastic material, stainless steel wire, Nitinol, cobalt-chromium-nickel-molybdenum-iron alloy, or cobalt-chrome alloy.
  • 5. The removable filter of claim 1 wherein each secondary strut is formed of a superelastic material, stainless steel wire, Nitinol, cobalt-chromium-nickel-molybdenum-iron alloy, or cobalt-chrome alloy.
  • 6. The removable filter of claim 1 wherein the first diameter ranges between about 6 French and 14 French, and the second diameter ranges between about 3 French and 9 French.
  • 7. The removable filter of claim 1 wherein the struts are formed of shape memory alloy with a transition temperature.
  • 8. The removable filter of claim 7 wherein the struts collapse to the collapsed state when the temperature of the struts is about equal to or greater than the transition temperature.
  • 9. The removable filter of claim 7 wherein the struts expand to the expanded state when the temperature of the struts is about equal to or greater than the transition temperature.
  • 10. The filter of claim 1 wherein pairs of secondary struts are positioned between pairs of primary struts, each pair of secondary struts being twisted about each other near the connected ends of the respective secondary struts to form a twisted section.
  • 11. The filter of claim 10 wherein each twisted section includes between about one and ten twists.
  • 12. A removable filter assembly for capturing thrombi in a blood vessel, the assembly comprising: a removable filter comprising: a plurality of primary struts each having a first length, the primary struts having first ends attached together along a longitudinal axis and housed within a hub, wherein the primary struts emanate from a first end of the hub, each primary strut having an arcuate segment including a first curved portion extending from the first end and a second curved portion extending from the first curved portion and terminating at an anchoring hook, the first and second curved portions defining a soft S-shape, each primary strut extending arcuately along the longitudinal axis and linearly radially, the primary struts being configured to move between an expanded state for engaging the anchoring hooks with the blood vessel and a collapsed state for filter retrieval or delivery, each primary strut being configured to cross another primary strut along the longitudinal axis in the collapsed state such that the arcuate segments occupy a first diameter, the first diameter being the distance between opposite arcuate segments of the primary struts in the collapsed state, and the anchoring hooks occupy a second diameter, the second diameter being the largest diameter occupied by the anchoring hooks in the collapsed state for filter retrieval or delivery, the first diameter being larger than the second diameter, each primary strut of the plurality of primary struts having a spring biased configuration that is self-expanding;a plurality of secondary struts separate from the primary struts, the secondary struts having a second length and connected ends attached together along the longitudinal axis and housed within the hub, wherein the secondary struts emanate from the first end of the hub and extend therefrom to free ends to centralize the filter in the expanded state in the blood vessel, each secondary strut extending arcuately along the longitudinal axis and linearly radially, each secondary strut having a first arc extending from the connected end away from the longitudinal axis and a second arc extending from the first arc towards the longitudinal axis, the second arc extending to the free end without a hook, the secondary struts having a smaller diameter than the primary struts, wherein the length of the filter is defined by the first length of the primary struts;a retrieval hook extending from the hub opposite the plurality of primary and secondary struts for removal of the filter from the blood vessel; andan introducer tube in which the removable filter in the collapsed state is disposed for retrieval or delivery of the filter.
  • 13. The removable filter of claim 12 wherein the first curved portion of each primary strut is configured to extend radially from the longitudinal axis of the filter and the second curved portion of each primary strut is configured to extend radially toward the longitudinal axis of the filter.
  • 14. The removable filter of claim 12 wherein the primary and secondary struts are formed of shape memory alloy with a transition temperature.
  • 15. The removable filter of claim 14 wherein the primary and secondary struts collapse to the collapsed state when the temperature of the primary and secondary struts is about equal to or greater than the transition temperature.
  • 16. The removable filter of claim 14 wherein the primary and secondary struts expand to the expanded state when the temperature of the primary and secondary struts is about equal to or greater than the transition temperature.
  • 17. The removable filter of claim 12 wherein the first diameter ranges between about 6 French and 14 French, and the second diameter ranges between about 3 French and 9 French.
  • 18. A removable filter assembly for capturing thrombi in a blood vessel, the assembly comprising: a removable filter comprising: a plurality of primary struts each having a first length, the primary struts having first ends attached together along a longitudinal axis and housed within a hub, wherein the primary struts emanate from a first end of the hub, each primary strut having an arcuate segment including a first curved portion extending from the first end and a second curved portion extending from the first curved portion and terminating at an anchoring hook, the first and second curved portions defining a soft S-shape, each primary strut extending arcuately along the longitudinal axis and linearly radially, the primary struts being configured to move between an expanded state for engaging the anchoring hooks with the blood vessel and a collapsed state for filter retrieval or delivery, each primary strut being configured to cross another primary strut along the longitudinal axis in the collapsed state such that the arcuate segments occupy a first diameter, the first diameter being the distance between opposite arcuate segments of the primary struts in the collapsed state, and the anchoring hooks occupy a second diameter, the second diameter being the largest diameter occupied by the anchoring hooks in the collapsed state for filter retrieval or delivery, the first diameter being larger than the second diameter, each primary strut of the plurality of primary struts having a spring biased configuration that is self-expanding;a plurality of secondary struts separate from the primary struts, the secondary struts having a second length and connected ends attached together along the longitudinal axis and housed within the hub, wherein the secondary struts emanate from the first end of the hub and extend therefrom to free ends to centralize the filter in the expanded state in the blood vessel, each secondary strut extending arcuately along the longitudinal axis and linearly radially, each secondary strut having a first arc extending from the connected end away from the longitudinal axis and a second arc extending from the first arc towards the longitudinal axis, the second arc extending to the free end without a hook, the secondary struts having a smaller diameter than the primary struts, each primary strut having two secondary struts in side-by-side relationship with the primary strut, wherein the length of the filter is defined by the first length of the primary struts;a retrieval hook extending from the hub opposite the plurality of primary and secondary struts for removal of the filter from the blood vessel; andan introducer tube in which the removable filter in the collapsed state is disposed for retrieval or delivery of the filter, the first diameter ranging between about 6 French and 14 French, the second diameter ranging between about 3 French and 9 French.
CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 60/562,943, filed on Apr. 16, 2004, entitled “REMOVABLE VENA CAVA FILTER FOR REDUCED TRAUMA IN COLLAPSED CONFIGURATION,” the entire contents of which are incorporated herein by reference. This application also claims the benefit of U.S. Provisional Application No. 60/562,813, filed on Apr. 16, 2004, entitled “REMOVABLE FILTER FOR CAPTURING BLOOD CLOTS,” the entire contents of which are incorporated herein by reference. This application also claims the benefit of U.S. Provisional Application No. 60/562,909, filed on Apr. 16, 2004, entitled “BLOOD CLOT FILTER WITH STRUTS HAVING AN EXPANDED REMEMBERED STATE,” the entire contents of which are incorporated herein by reference. This application also claims the benefit of U.S. Provisional Application No. 60/563,176, filed on Apr. 16, 2004, entitled “BLOOD CLOT FILTER HAVING A COLLAPSED REMEMBERED STATE,” the entire contents of which are incorporated herein by reference.

US Referenced Citations (228)
Number Name Date Kind
2281448 Mathey Apr 1942 A
3137298 Glassman Jun 1964 A
3174851 Buehler Mar 1965 A
3334629 Cohn Aug 1967 A
3540431 Mobin-Uddin Nov 1970 A
3868956 Alfidi et al. Mar 1975 A
3952747 Kimmell, Jr. Apr 1976 A
4425908 Simon Jan 1984 A
4494531 Gianturco Jan 1985 A
4619246 Molgaard-Nielsen et al. Oct 1986 A
4643184 Mobin-Uddin Feb 1987 A
4655771 Wallsten Apr 1987 A
4665906 Jervis May 1987 A
4688553 Metals Aug 1987 A
4727873 Mobin-Uddin Mar 1988 A
4759757 Pinchuk Jul 1988 A
4781177 Lebigot Nov 1988 A
4793348 Palmaz Dec 1988 A
4817600 Herms et al. Apr 1989 A
4830003 Wolff et al. May 1989 A
4832055 Palestrant May 1989 A
4856516 Hillstead Aug 1989 A
4873978 Ginsburg Oct 1989 A
4943297 Saveliev et al. Jul 1990 A
4950227 Savin et al. Aug 1990 A
4954126 Wallsten Sep 1990 A
4957501 Lahille et al. Sep 1990 A
4969891 Gewertz Nov 1990 A
4990156 Lefebvre Feb 1991 A
5037377 Alonso Aug 1991 A
5059205 El-Nounou et al. Oct 1991 A
5061275 Wallsten et al. Oct 1991 A
5067957 Jervis Nov 1991 A
5071407 Termin et al. Dec 1991 A
5108418 Lefebvre Apr 1992 A
5108419 Reger et al. Apr 1992 A
5133733 Rasmussen et al. Jul 1992 A
5135516 Sahatjian et al. Aug 1992 A
5147379 Sabbaghian et al. Sep 1992 A
5152777 Goldberg et al. Oct 1992 A
5160342 Reger et al. Nov 1992 A
5190546 Jervis Mar 1993 A
5217484 Marks Jun 1993 A
5221261 Termin et al. Jun 1993 A
5224953 Morgentaler Jul 1993 A
5234458 Metais Aug 1993 A
5242462 El-Nounou et al. Sep 1993 A
5300086 Gory et al. Apr 1994 A
5304121 Sahatjian Apr 1994 A
5304200 Spaulding Apr 1994 A
5324304 Rasmussen Jun 1994 A
5329942 Gunther et al. Jul 1994 A
5344427 Cottenceau et al. Sep 1994 A
5350398 Pavcnik et al. Sep 1994 A
5370657 Irie Dec 1994 A
5375612 Cottenceau et al. Dec 1994 A
5382261 Palmaz Jan 1995 A
5383887 Nadal Jan 1995 A
5405377 Cragg Apr 1995 A
5413586 Dibie et al. May 1995 A
5421832 Lefebvre Jun 1995 A
5476508 Amstrup Dec 1995 A
5527338 Purdy Jun 1996 A
5540712 Kleshinski et al. Jul 1996 A
5549626 Miller et al. Aug 1996 A
5549629 Thomas et al. Aug 1996 A
5601595 Smith Feb 1997 A
5626605 Irie et al. May 1997 A
5630801 Roussigne et al. May 1997 A
5634942 Chevillon et al. Jun 1997 A
5649906 Gory et al. Jul 1997 A
5649953 Lefebvre Jul 1997 A
5669933 Simon et al. Sep 1997 A
5681347 Cathcart et al. Oct 1997 A
5683411 Kavteladze et al. Nov 1997 A
5695519 Summers et al. Dec 1997 A
5709704 Nott et al. Jan 1998 A
5720764 Naderlinger Feb 1998 A
5725550 Nadal Mar 1998 A
5746767 Smith May 1998 A
5755778 Kleshinski May 1998 A
5755790 Chevillon et al. May 1998 A
5776162 Kleshinski Jul 1998 A
5800457 Gelbfish Sep 1998 A
5800525 Bachinski et al. Sep 1998 A
5807398 Shaknovich Sep 1998 A
5810874 Lefebvre Sep 1998 A
5836968 Simon et al. Nov 1998 A
5836969 Kim et al. Nov 1998 A
5843244 Pelton et al. Dec 1998 A
5853420 Chevillon et al. Dec 1998 A
5895399 Barbut et al. Apr 1999 A
5902317 Kleshinski et al. May 1999 A
5916235 Guglielmi Jun 1999 A
5928260 Chin et al. Jul 1999 A
5928261 Ruiz Jul 1999 A
5932035 Koger et al. Aug 1999 A
5938683 Lefebvre Aug 1999 A
5951585 Cathcart et al. Sep 1999 A
5961546 Robinson et al. Oct 1999 A
5976172 Homsma et al. Nov 1999 A
5984947 Smith Nov 1999 A
6007557 Ambrisco et al. Dec 1999 A
6007558 Ravenscroft et al. Dec 1999 A
6013093 Nott et al. Jan 2000 A
6077274 Ouchi et al. Jun 2000 A
6080178 Meglin Jun 2000 A
6086610 Duerig et al. Jul 2000 A
6126673 Kim et al. Oct 2000 A
6129755 Mathis et al. Oct 2000 A
6146404 Kim et al. Nov 2000 A
6152144 Lesh et al. Nov 2000 A
6156055 Ravenscroft Dec 2000 A
6156061 Wallace et al. Dec 2000 A
6179851 Barbut et al. Jan 2001 B1
6179859 Bates et al. Jan 2001 B1
6179861 Khosravi et al. Jan 2001 B1
6193739 Chevillon et al. Feb 2001 B1
6221102 Baker et al. Apr 2001 B1
6231589 Wessman et al. May 2001 B1
6241738 Dereume Jun 2001 B1
6241746 Bosma et al. Jun 2001 B1
6245012 Kleshinski Jun 2001 B1
6245088 Lowery Jun 2001 B1
6251122 Tsukernik Jun 2001 B1
6258026 Ravenscroft et al. Jul 2001 B1
6267776 O'Connell Jul 2001 B1
6273900 Nott et al. Aug 2001 B1
6273901 Whitcher et al. Aug 2001 B1
6277139 Levinson et al. Aug 2001 B1
6287315 Wijeratne et al. Sep 2001 B1
6287329 Duerig et al. Sep 2001 B1
6306163 Fitz Oct 2001 B1
6312454 Stockel et al. Nov 2001 B1
6312455 Duerig et al. Nov 2001 B2
6325815 Kusleika et al. Dec 2001 B1
6331183 Suon Dec 2001 B1
6342062 Suon et al. Jan 2002 B1
6342063 DeVries et al. Jan 2002 B1
6342067 Mathis et al. Jan 2002 B1
6346116 Brooks et al. Feb 2002 B1
6364895 Greenhalgh Apr 2002 B1
6391044 Yadav et al. May 2002 B1
6391045 Kim et al. May 2002 B1
6436120 Meglin Aug 2002 B1
6436121 Blom Aug 2002 B1
6447530 Ostrovsky et al. Sep 2002 B1
6461370 Gray et al. Oct 2002 B1
6468290 Weldon et al. Oct 2002 B1
6482222 Bruckheimer et al. Nov 2002 B1
6485502 DonMichael et al. Nov 2002 B2
6506205 Goldberg et al. Jan 2003 B2
6511503 Burkett et al. Jan 2003 B1
6517559 O'Connell Feb 2003 B1
6527962 Nadal Mar 2003 B1
6540767 Walak et al. Apr 2003 B1
6551342 Shen et al. Apr 2003 B1
6558404 Tsukernik May 2003 B2
6569183 Kim et al. May 2003 B1
6579303 Amplatz Jun 2003 B2
6582447 Patel et al. Jun 2003 B1
6589266 Whitcher et al. Jul 2003 B2
6602226 Smith et al. Aug 2003 B1
6616680 Thielen Sep 2003 B1
6638294 Palmer Oct 2003 B1
6652558 Patel et al. Nov 2003 B2
6685722 Rosenbluth et al. Feb 2004 B1
6726621 Suon et al. Apr 2004 B2
7297000 Bernard Nov 2007 B1
20010000799 Wessman et al. May 2001 A1
20010011181 DiMatteo Aug 2001 A1
20010023358 Tsukernik Sep 2001 A1
20010034547 Hall et al. Oct 2001 A1
20010034548 Vrba et al. Oct 2001 A1
20010037126 Stack et al. Nov 2001 A1
20010039432 Whitcher et al. Nov 2001 A1
20020002401 McGuckin, Jr. et al. Jan 2002 A1
20020016624 Patterson et al. Feb 2002 A1
20020032460 Kusleika et al. Mar 2002 A1
20020039445 Abe et al. Apr 2002 A1
20020055767 Forde et al. May 2002 A1
20020087187 Mazzocchi et al. Jul 2002 A1
20020099431 Armstrong et al. Jul 2002 A1
20020116024 Goldberg et al. Aug 2002 A1
20020133217 Sirhan et al. Sep 2002 A1
20020138097 Ostrovsky et al. Sep 2002 A1
20020156520 Boylan et al. Oct 2002 A1
20020161393 Demond et al. Oct 2002 A1
20020169474 Kusleika et al. Nov 2002 A1
20020169495 Gifford et al. Nov 2002 A1
20020183782 Tsugita et al. Dec 2002 A1
20020193827 McGuckin, Jr. et al. Dec 2002 A1
20020193828 Griffin et al. Dec 2002 A1
20020193874 Crowley Dec 2002 A1
20030018343 Mathis Jan 2003 A1
20030028238 Burkett et al. Feb 2003 A1
20030040772 Hyodoh et al. Feb 2003 A1
20030055481 McMorrow Mar 2003 A1
20030069596 Eskuri Apr 2003 A1
20030074019 Gray et al. Apr 2003 A1
20030078614 Salahieh et al. Apr 2003 A1
20030083692 Vrba et al. May 2003 A1
20030097145 Goldberg et al. May 2003 A1
20030105484 Boyle et al. Jun 2003 A1
20030109897 Walak et al. Jun 2003 A1
20030114880 Hansen et al. Jun 2003 A1
20030125790 Fastovsky et al. Jul 2003 A1
20030125793 Vesely Jul 2003 A1
20030130681 Ungs Jul 2003 A1
20030144686 Martinez et al. Jul 2003 A1
20030153943 Michael et al. Aug 2003 A1
20030153945 Patel et al. Aug 2003 A1
20030163159 Patel et al. Aug 2003 A1
20030176888 O'Connell Sep 2003 A1
20030181922 Alferness Sep 2003 A1
20040010282 Kusleika Jan 2004 A1
20040158273 Weaver et al. Aug 2004 A1
20040186510 Weaver Sep 2004 A1
20040193209 Pavcnik et al. Sep 2004 A1
20040230220 Osborne et al. Nov 2004 A1
20050165441 McGuckin, Jr. et al. Jul 2005 A1
20050165442 Thinnes, Jr. et al. Jul 2005 A1
20050251199 Osborne et al. Nov 2005 A1
20050267513 Osborne et al. Dec 2005 A1
20050267514 Osborne et al. Dec 2005 A1
20060069406 Hendriksen et al. Mar 2006 A1
20060100660 Osborne et al. May 2006 A1
20070005095 Osborne et al. Jan 2007 A1
Foreign Referenced Citations (33)
Number Date Country
003417738 Nov 1985 DE
3429850 Feb 1986 DE
0270432 Jun 1988 EP
0348295 Dec 1989 EP
0350043 Oct 1990 EP
0430848 Jun 1991 EP
0437121 Jul 1991 EP
0462008 Dec 1991 EP
0472334 Feb 1992 EP
0701800 Mar 1996 EP
2587901 Apr 1987 FR
2649884 Jan 1991 FR
2672487 Aug 1992 FR
2200848 Aug 1988 GB
2200848 Aug 1988 GB
835447 Jun 1981 SU
1103868 Jul 1984 SU
955912 Feb 1988 SU
WO 9104716 Apr 1991 WO
WO 9111972 Aug 1991 WO
WO 9508567 Mar 1995 WO
WO 9527448 Oct 1995 WO
WO 9617634 Jun 1996 WO
WO 0106952 Feb 2001 WO
WO 03011188 Feb 2003 WO
WO 2004049973 Jun 2004 WO
WO 2005072645 Aug 2005 WO
WO2005102210 Nov 2005 WO
WO 2005102211 Nov 2005 WO
WO 2005102212 Nov 2005 WO
WO 2005102213 Nov 2005 WO
WO 2005102214 Nov 2005 WO
WO 2006036867 Apr 2006 WO
Related Publications (1)
Number Date Country
20050267512 A1 Dec 2005 US
Provisional Applications (4)
Number Date Country
60562943 Apr 2004 US
60562813 Apr 2004 US
60562909 Apr 2004 US
60563176 Apr 2004 US