Conical vena cava filter with jugular or femoral retrieval

An intravascular filter configured for upstream or downstream retrieval and a method for retrieving an intravascular filter from a patient's vena cava through the patient's femoral vein. The filter includes a downstream hub, an upstream hub, a plurality of primary struts extending from the downstream hub to the upstream hub, a plurality of secondary struts extending upstream from fixed ends housed in the downstream hub to free ends, secondary strut eyelets disposed at the free ends of the secondary struts, a loop member disposed through the secondary strut eyelets, an upstream coupling element disposed with the upstream hub, and a tether extending from the loop member to the upstream coupling element.

BACKGROUND

The present invention relates to medical devices. More particularly, the invention relates to a removable intravascular filter that can be removed from the vena cava of a patient through the patient's jugular or femoral vein.

Filtering devices that are percutaneously placed in the vena cava have been available for a number of years. A need for such filtering devices arises in trauma patients, orthopedic surgery patients, neurosurgery patients, or in patients having medical conditions requiring bed rest or non-movement. Patients having such medical conditions face an increased risk of thrombosis in the peripheral vasculature, 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.

Historically, vena cava filters were considered to be permanent implants and remained implanted in the patient for life. More recently, removable vena cava filters have been developed. These filters may be removed from the patient's vena cava after the condition or medical problem that required the device has passed.

The benefits of vena cava filters, and particularly removable vena cava filters, have been well established, but improvements may be made. For example, the vast majority of the removable vena cava filters currently on the market must be removed through the patient's jugular vein. In some instances, however, removal through the patient's femoral vein is preferable to removal through the jugular vein. For example, filters sometimes shift or become stuck in a patient's vena cava. The ability to retrieve such troublesome filters from a different access point can increase the likelihood that they will be removed successfully. In addition, jugular retrieval requires that a retrieval sheath be advanced through the patient's heart, which is contraindicated in some cases. Finally, scarring at the access point is less noticeable when retrieval is initiated through the femoral vein.

It has been a challenge to design a vena cava filter suitable for removal through a patient's femoral vein.

SUMMARY OF INVENTION

The present invention generally provides an intravascular filter suitable for upstream or downstream retrieval. The invention also provides a method for retrieving an intravascular filter from a patient's vena cava through the patient's femoral vein.

In one embodiment, an intravascular filter configured for upstream retrieval is provided. The filter comprises a downstream hub and an upstream hub disposed along a longitudinal axis of the filter. The filter further comprises a plurality of primary struts having downstream and upstream ends. The downstream hub houses the downstream ends of the primary struts; the upstream hub houses the upstream ends of the primary struts. The filter further comprises a plurality of secondary struts having fixed and free ends. The downstream hub houses the fixed ends of the secondary struts. The secondary struts extend upstream from the downstream hub to the free ends. The free ends are disposed longitudinally between the downstream hub and the upstream hub. Each secondary strut has a secondary strut eyelet disposed at its free end. The filter further comprises a loop member disposed through the secondary strut eyelets. The filter further comprises a coupling element disposed with the upstream hub for upstream retrieval of the filter. A tether extends from the loop member to the upstream coupling element.

In another embodiment, a method for retrieving an intravascular filter from a patient's vena cava through the patient's femoral vein is provided. The method comprises percutaneously inserting a retrieval assembly comprising a retrieval sheath and a control member into the patient's vasculature through the patient's femoral vein. The method further comprises advancing the retrieval assembly through the patient's vasculature to a retrieval position proximal to the intravascular filter in the patient's vena cava. The filter comprises a downstream hub and an upstream hub disposed along a longitudinal axis of the filter. The filter further comprises a plurality of primary struts having downstream and upstream ends. The downstream hub houses the downstream ends of the primary struts; the upstream hub houses the upstream ends of the primary struts. The filter further comprises a plurality of secondary struts having fixed and free ends. The downstream hub houses the fixed ends of the secondary struts. The secondary struts extend upstream from the downstream hub to the free ends. The free ends are disposed longitudinally between the downstream hub and the upstream hub. Each secondary strut has a secondary strut eyelet disposed at its free end. The filter further comprises a loop member disposed through the secondary strut eyelets. The filter further comprises a coupling element disposed with the upstream hub for upstream retrieval of the filter. A tether extends from the loop member to the upstream coupling element. The method further comprises attaching the control member to the upstream coupling element of the intravascular filter and retracting the control member proximally through the retrieval sheath to apply tension to the upstream coupling element. The upstream coupling element relays the tension through the tether to the loop member to urge the secondary struts toward the longitudinal axis of the filter. The method further comprises advancing the retrieval sheath distally relative to the control member to place the retrieval sheath over the intravascular filter and removing the retrieval assembly and the intravascular filter from the patient's vasculature.

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

DETAILED DESCRIPTION

An intravascular filter configured for upstream or downstream retrieval is provided. The filter may be implanted in a patient's vena cava and may be removed from the vena cava through the patient's jugular or femoral vein. A method of removing an intravascular filter from a patient's vena cava through the patient's femoral vein is also provided.

As used herein, the terms “upstream” and “downstream” refer to the direction of blood flow in a patient's vasculature. When these terms are used to describe the elements of an intravascular filter, they suggest a preferred orientation of the filter in the patient's vasculature. However, these terms are not intended to be limiting in this regard. In other words, a filter otherwise including the structural elements recited herein will not be deemed to fall outside the scope of the present invention merely because it is implanted in a different orientation.

FIGS. 1aand1billustrate an intravascular filter10in accordance with the principles of the present invention. The filter10has an expanded configuration (FIG. 1a) suitable for capturing thrombi in a patient's blood vessel (e.g., in the patient's vena cava) and a collapsed configuration (FIG. 1b) suitable for removal from the patient's vasculature. InFIGS. 1aand1b, the upstream direction is indicated by the arrow U, and the downstream direction is indicated by the arrow D.

The filter10comprises a downstream hub12and an upstream hub14disposed along a longitudinal axis L of the filter10, a plurality of primary struts20extending from the downstream hub12to the upstream hub14, a plurality of secondary struts30extending upstream from the downstream hub12, a downstream coupling element70disposed with the downstream hub12for downstream removal of the filter10, and an upstream coupling element80disposed with the upstream hub14for upstream removal of the filter10.

The filter10may have any suitable number and configuration of primary and secondary struts20and30without falling beyond the scope of the present invention. In one embodiment, shown inFIG. 1a, the filter10has a plurality of primary struts20and a plurality of secondary struts30freely spaced between the primary struts30. For example, the filter10preferably has between two and eight primary struts20, more preferably between three and six primary struts20, and most preferably four primary struts20. The filter10preferably has between two and sixteen secondary struts30, more preferably between four and eight secondary struts30, and most preferably either four or eight secondary struts30.

In the embodiment shown inFIG. 1a, the filter10has four primary struts20and four secondary struts30. Each primary strut20has a downstream end22, a downstream portion23, a middle portion25, and upstream portion27, and an upstream end24. The downstream hub12houses the downstream ends22of the primary struts20. Each primary strut20extends arcuately in a longitudinal plane including the longitudinal axis L. When the filter10is in the expanded state, as shown inFIG. 1a, the downstream portion23extends upstream from the downstream end22and bends away from the longitudinal axis L, the middle portion25extends upstream from the downstream portion23and bends toward the longitudinal axis L, and the upstream portion27extends upstream from the middle portion25and bends away from the longitudinal axis L to the upstream end24. The upstream hub14houses the upstream ends24of the primary struts20.

In the embodiment shown inFIG. 1a, each secondary strut30has a fixed end32, a first portion33, a second portion35, and a free end34. The downstream hub12houses the fixed ends32of the secondary struts30. Each secondary strut30extends arcuately in a longitudinal plane including the longitudinal axis L. When the filter10is in the expanded state, as shown inFIG. 1a, the first portion33extends upstream from the fixed end32and bends away from the longitudinal axis L, and the second portion35extends upstream from the first portion33and bends toward the longitudinal axis L to the free end34.

Preferably, the primary and secondary struts20and30are formed from a superelastic material, stainless steel wire, nickel-titanium alloy (e.g., Nitinol), cobalt-chromium-nickel-molybdenum-iron alloy, cobalt-chrome alloy, or any other suitable material that will result in a self-opening or self-expanding filter.

The free ends34of the secondary struts30are disposed longitudinally between the downstream hub12and the upstream hub14. In the filter10shown inFIG. 1a, the free ends34of the secondary struts30define a plane (not shown) approximately bisecting the longitudinal axis L between the downstream hub12and the upstream hub14. The plane defined by the free ends34of the secondary struts30is approximately perpendicular to the longitudinal axis L. In other embodiments, the free ends34of the secondary struts30may define a plane intersecting the longitudinal axis L at a point closer to the downstream hub12or at a point closer to the upstream hub14. The plane defined by the free ends34of the secondary struts30may be approximately perpendicular to the longitudinal axis L, or such plane may intersect the longitudinal axis L at a non-right angle. In still other embodiments, the free ends34of the secondary struts30may not define a single plane.

Each secondary strut30has a secondary strut eyelet42disposed at its free end34. In the filter10shown inFIGS. 1aand1b, the secondary strut eyelets42are unitarily formed with the secondary struts30. In other embodiments, the secondary strut eyelets42may be fixedly attached to the free ends34of the secondary struts30, e.g. by welding or by adhesive bonding.

In the filter10shown inFIG. 1a, each primary strut20has a primary strut eyelet44disposed in its middle portion25. Like the secondary strut eyelets42, the primary strut eyelets44may be unitarily formed with the primary struts20(as shown inFIGS. 1aand1b) or may be fixedly attached to the primary struts20. In other embodiments, the primary struts20do not have primary strut eyelets44.

The primary strut eyelets44may be disposed about evenly with the secondary strut eyelets42along the longitudinal axis L of the filter10. Since the secondary strut eyelets44are disposed at the free ends34of the secondary struts30, the primary strut eyelets44may be disposed about evenly with the free ends34of the secondary struts30. For example, if the free ends34of the secondary struts30define a plane approximately bisecting the longitudinal axis L between the downstream hub12and the upstream hub14, the primary strut eyelets44may lie in the same plane. In other embodiments, the primary strut eyelets44may lie in a plane defined by the free ends34of the secondary struts that intersects the longitudinal axis L at a point closer to the downstream hub12or at a point closer to the upstream hub14. In other embodiments, the primary strut eyelets44may not lie in the same plane as the secondary strut eyelets42.

In some embodiments, at least one of the primary or secondary struts20or30further comprises an anchoring hook90extending away from the longitudinal axis L and downstream to engage a blood vessel wall and prevent downstream migration of the filter10. As shown inFIGS. 1aand1b, the anchoring hooks90may be disposed in the middle portions25of one or more of the primary struts20. Where the primary struts20include primary strut eyelets44, the anchoring hooks90may be disposed upstream or downstream of the primary strut eyelets44. In other embodiments, the anchoring hooks90may extend from the primary strut eyelets44.

The filter10further comprises a loop member50disposed through the primary and secondary strut eyelets44and42. In other embodiments, including embodiments in which the primary struts20do not include primary strut eyelets44, the loop member50is only disposed through the secondary strut eyelets42.

The loop member may be formed from one or more strands of any material that is suitably flexible to slide through the primary and secondary strut eyelets44and42. For example, the loop member may be formed from a fine metal wire, such as stainless steel wire. Alternatively, the loop member may be formed from a synthetic material, such as nylon, polyethylene, polypropylene, a polyester (e.g., polyethylene terephthalate), polyetherurethane urea, or a fluorinated polymer (e.g., polytetrafluoroethylene). As used herein, the term “loop member” includes both a “closed loop” and an “open loop.”

In the filter10shown inFIGS. 1aand1b, the loop member50is a closed loop. As used herein, the term “closed loop” includes an elongate member initially formed as a closed loop as well as a member formed into a closed loop by fixedly attaching the opposing ends of the member. The loop member50passes sequentially through adjacent primary and secondary strut eyelets44and42, such that the loop member50extends around the circumference of the filter10when the filter10is in the expanded configuration (FIG. 1a).

As shown inFIGS. 1aand1b, the loop member50is slidably disposed through all of the primary and secondary strut eyelets44and42. In other embodiments, however, the loop member50may be fixedly attached to one or more of the primary and secondary strut eyelets44and42. For example, the loop member50may be tied to one or more of the primary and secondary strut eyelets44and42, or it may be adhesively bonded to such eyelets. The primary and/or secondary strut eyelets44and/or42to which the loop member50is fixedly attached may be known as first eyelets, and the primary and/or secondary strut eyelets44and/or42through which the loop member50is slidably disposed may be known as second eyelets.

In other embodiments, shown inFIGS. 3aand3b, the loop members150and250are open loops having attached ends155aand255aand unattached ends155band255b. The attached end155aor255ais fixedly attached to a first eyelet146or246, which may be a primary strut eyelet144(FIG. 3a) or a secondary strut eyelet242(FIG. 3b). The loop member150or250passes sequentially through adjacent second eyelets148or248, including primary and secondary strut eyelets144or244and142or242around the circumference of the filter, and through the first eyelet146or246, to define the loop.

Referring again toFIGS. 1aand1b, the upstream coupling element80preferably is free to move longitudinally relative to the upstream hub14.FIG. 2depicts a cross-sectional view of the upstream hub14. As shown inFIG. 2, the upstream hub14has an annular portion16defining an opening18. The opening18is disposed along the longitudinal axis of the filter. The annular portion16houses the upstream ends24of the primary struts.

Referring again toFIGS. 1aand1b, the upstream coupling element80comprises a longitudinal guide member82, an attachment member86, and a tether attachment88. The longitudinal guide member82is slidably disposed through the opening18of the upstream hub14. The longitudinal guide member82has a first end83adisposed downstream of the upstream hub14and a second end83bdisposed upstream of the upstream hub14. The attachment member86is disposed at the second end83bof the longitudinal guide member82. The tether attachment88is disposed at the first end83aof the longitudinal guide member82.

As shown inFIGS. 1aand1b, the upstream coupling element80further comprises a first end stop84aand a second end stop84bdisposed at the first and second ends83aand83bof the longitudinal guide member82. The widths of the first and second end stops84aand84bare preferably greater than the diameter of the opening18, such that the upstream coupling element80does not slide completely through the upstream hub14.

As shown inFIGS. 1aand1b, the filter10further comprises one or more tethers60extending from the loop member50to the upstream coupling element80. More specifically, the tether(s)60attach to tether attachment88at the first end83aof the longitudinal guide member82of the upstream coupling element80. The filter10may include one tether60or a plurality of tethers60. The tether(s)60may be formed from the same material as the loop member50or from any other suitable material.

When the loop member50is a closed loop, as shown inFIGS. 1aand1b, the tether(s)60extend from one or more locations along the loop member50to the tether attachment88. In this embodiment, the filter10preferably includes a plurality of tethers60. For example the filter10may include two to ten tethers60, preferably three to eight tethers60, more preferably four to six tethers60, and most preferably four tethers60. The tethers60may be evenly or unevenly spaced along the loop member50.

The embodiments shown inFIGS. 3aand3b, where the loop members150and250are open loops, preferably include single tethers160and260. The tethers160and260extend from the unattached ends155band255bof the loop members150and250to the tether attachments188and288. The unattached ends155band255bof the loop members150and250are integrally connected with the tethers160and260. The unattached ends155band255bare understood to be “integrally connected” with the tethers160and260if the loop members150and250are unitarily formed with the tethers160and260or if the unattached ends155band255bof the loop members150and250are fixedly attached to the downstream ends of the tethers160and260(e.g., by tying or by adhesive bonding).

In the following discussion of the deployment and retrieval of the filter10, the terms “proximal” and “distal,” and derivatives thereof, will be understood in the frame of reference of the medial practitioner deploying or retrieving the filter10. Thus, “proximal” refers to locations closer to the practitioner, and “distal” refers to locations further from the practitioner (i.e., deeper in the patient's vasculature).

The filter10shown inFIG. 1amay be delivered to a patient's blood vessel, such as the patient's vena cava, using standard techniques familiar to those having ordinary skill in the relevant art. For example, a delivery system may be percutaneously inserted into the patient's vasculature via any suitable access site, such as the jugular vein, femoral vein, or any other suitable access site. The delivery system may be advanced through the patient's vasculature until the distal end of the delivery system is disposed in the patient's blood vessel at the desired site of deployment, e.g., in the patient's vena cava.

If the filter10is to be deployed in the vena cava, and the delivery system is inserted into the patient's vasculature through the patient's jugular vein, the filter10is inserted into the body with the upstream hub14leading and the downstream hub12trailing. By contrast, if the delivery system is inserted into the patient's vasculature through the patient's femoral vein, the filter10is inserted into the body with the downstream hub12leading and the upstream hub14trailing.

Upon deployment from the distal end of the delivery system, the struts of the filter preferably self-expand away from the longitudinal axis until the struts engage the blood vessel walls. While the foregoing method is provided by way of example, a person having ordinary skill in the relevant art will understand that a filter constructed in accordance with the principles of the present invention may be deployed using any other suitable technique without falling outside the scope of the present invention.

The operation and retrieval of the filter10will now be described with reference toFIGS. 4-6. When the filter10is deployed in a patient's blood vessel V, the primary and secondary struts20and30engage the walls W of the blood vessel V, anchoring and centering the filter10in the blood vessel V.

Thrombi T carried by the blood stream are captured in the filter10. More specifically, the thrombi T are captured along the longitudinal axis of the filter10near the downstream hub12of the filter10. As the thrombi T enter the filter10, the thrombi T are funneled toward the longitudinal axis L of the filter10by the primary and secondary struts20and30. Several structural features of the filter10facilitate this funneling action. First, because the secondary struts30do not extend all the way to the upstream hub14of the filter10, the thrombi T are able to pass between the upstream portions27of the primary struts20into the inside of the filter10. In addition, the upstream portion27(and any part of the middle portion25upstream of the primary strut eyelet44) of each primary strut20preferably has a smaller diameter than the downstream portion23(and any part of the middle portion25downstream of the primary strut eyelet44) of the primary strut20, further facilitating the passage of thrombi T into the inside of the filter10. Second, the angle of the downstream and middle portions23and25of the primary struts20, and the angle of the secondary struts30, relative to the longitudinal axis L causes the thrombi T to slide toward the longitudinal axis as the flow of blood pushes the thrombi T downstream.

The capture of thrombi T along the longitudinal axis L of the filter10is advantageous for several reasons. First, because blood flow is greatest near the center of the blood vessel V, thrombi T captured near the center of the vessel are more likely to dissolve after capture. Second, thrombi T captured along the wall of the blood vessel V tend to grow by accumulating additional clot material, and can eventually occlude the vessel.

After the risk of embolism has subsided, the filter10may be removed from the blood vessel V through either the patient's jugular vein or femoral vein. The filter10may be removed through the patient's jugular vein using procedures that are well known to those having ordinary skill in the relevant art. For example, the filter10may be removed through the patient's jugular vein using the method described in U.S. Pat. No. 7,625,390, the entire contents of which are incorporated herein by reference.

Alternatively, the filter10may be removed through the patient's femoral vein. Referring now toFIG. 5, removal of the filter10is initiated by inserting a retrieval assembly310into the patient's vasculature through the patient's femoral vein. The retrieval assembly includes a retrieval sheath320and a first control member330. The first control member330has a snare332disposed at its distal end.

Referring again toFIG. 5, the retrieval assembly310is advanced through the patient's vasculature to a position immediately upstream of the filter10in the patient's blood vessel V. The first control member330is advanced from the lumen of the retrieval sheath320, and the snare332is attached to the attachment member86of the upstream coupling element80. The first control member330is then retracted in the direction of the arrow R, applying tension to the attachment member86.

As tension is applied to the attachment member86by the retraction of the first control member330, the longitudinal guide member82slides in an upstream direction through the upstream hub14, applying tension to the tethers60. The tethers60, in turn, apply tension to the loop member50, causing the loop member50to slide through the primary and secondary strut eyelets44and42.

As the loop member50slides through the primary and secondary strut eyelets44and42, the circumference of the loop member50decreases. The loop member50functions like a “drawstring,” pulling the primary and secondary struts20and30toward the longitudinal axis of the filter10and the blood vessel V such that the filter collapses as indicated by the arrows C.

FIG. 6depicts the filter10in a partially collapsed configuration. Upon further retraction of the first control member330, additional tension is applied to the tethers60and the loop member50, resulting in further collapse of the filter10until the filter10assumes the collapsed configuration as shown inFIG. 1b. In the collapsed configuration, the filter10can be accommodated in the lumen of the retrieval sheath320.

As the struts20and30disengage the wall W of the blood vessel V, the filter10tends to move proximally due to the tension applied to the attachment member86. To hold the filter10in position, the medical practitioner may brace the distal end322of the retrieval sheath320against the primary struts20as shown inFIGS. 5 and 6. The medical practitioner may also employ a second control member (not shown) to hold the filter10in position. The second control member may be introduced into the patient's vasculature through the retrieval sheath320and may brace against the upstream side of the downstream hub12. Alternatively, the second control member may be introduced into the patient's vasculature through the patient's jugular vein and attach to the downstream coupling element70.

As will be apparent from the foregoing discussion, the loop member50, tethers60, and upstream coupling element80are important to the femoral vein retrieval of the filter10. Using this mechanism, the secondary struts30are collapsed to a diameter smaller than the diameter of the retrieval sheath320, such that the filter10can be pulled into the lumen of the sheath320. Once the filter10is stowed in the lumen of the retrieval sheath320, the retrieval assembly310and the filter10may be removed from the patient's vasculature. A similar procedure may be employed for retrieving the filters110and210depicted inFIGS. 3aand3b.

Referring now toFIG. 7, a method for retrieving an intravascular filter, such as the filter10, from a patient's vena cava through the patient's femoral vein is provided. As indicated in box502, the method500involves percutaneously inserting a retrieval assembly, such as the retrieval assembly310, into the patient's vasculature through the patient's femoral vein. The retrieval assembly comprises a retrieval sheath and a first control member.

As indicated in box504, the method500further comprises advancing the retrieval assembly through the patient's vasculature to a retrieval position proximal to the intravascular filter in the patient's vena cava. The first control member is then attached to the upstream coupling element of the intravascular filter, as indicated in box506.

As indicated in box508, the method500further comprises retracting the first control member proximally through the retrieval sheath to apply tension to the upstream coupling element. The distal end of the retrieval sheath may be braced against the primary struts of the filter to hold the filter in position during the retraction of the first control member. The upstream coupling element relays the tension through the tether to the loop member to urge the secondary struts toward the longitudinal axis of the filter. The retraction of the control member may cause a portion of the loop member to slide through at least one of the secondary strut eyelets.

Once the filter is in a collapsed configuration, the retrieval sheath is advanced distally relative to the first control member to place the retrieval sheath over the intravascular filter (box510). With the filter stowed in the lumen of the retrieval sheath, the retrieval assembly and the intravascular filter are removed from the patient's vasculature (box512).

While the present invention has been described in terms of certain preferred embodiments, it will be understood that the invention is not limited to the disclosed embodiments, as those having skill in the art may make various modifications without departing from the scope of the following claims.