Catch members for occluder devices
Devices and techniques for modifying and maintaining a configuration of an occlusion device for the closure of physical anomalies, such as an atrial septal defect, a patent foramen ovale (PFO), and other septal and vascular defects are described. The devices and techniques relate particularly to, but are not limited to, modifying and maintaining a configuration of a PFO occluder made from a polymer tube. The proximal portion of a catch member may be provided with one or more protrusions, or arms, or bump or other raised element for securing the occluder in a partial or fully deployed configuration, either temporarily or permanently.
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This Application claims the benefit of priority to U.S. Provisional Application Ser. No. 60/753,681, filed Dec. 22, 2005, the disclosure of which is incorporated by reference herein.
FIELD OF THE INVENTIONThis invention relates generally to occlusion devices for the closure of physical anomalies, such as an atrial septal defect, a patent foramen ovale, and other septal and vascular defects. The invention also relates to mechanisms for deploying such devices and securing them in the deployed position.
BACKGROUND OF THE INVENTION A patent foramen ovale (PFO), illustrated in
The foramen ovale serves a desired purpose when a fetus is gestating. Because blood is oxygenated through the umbilical cord, and not through the developing lungs, the circulatory system of the fetal heart allows the blood to flow through the foramen ovale as a physiologic conduit for right-to-left shunting. After birth, with the establishment of pulmonary circulation, the increased left atrial blood flow and pressure results in functional closure of the foramen ovale. This functional closure is subsequently followed by anatomical closure of the two over-lapping layers of tissue: septum primum 14 and septum secundum 16. However, a PFO has been shown to persist in a number of adults.
The presence of a PFO is generally considered to have no therapeutic consequence in otherwise healthy adults. Paradoxical embolism via a PFO is considered in the diagnosis for patients who have suffered a stroke or transient ischemic attack (TIA) in the presence of a PFO and without another identified cause of ischemic stroke. While there is currently no definitive proof of a cause-effect relationship, many studies have confirmed a strong association between the presence of a PFO and the risk for paradoxical embolism or stroke. In addition, there is significant evidence that patients with a PFO who have had a cerebral vascular event are at increased risk for future, recurrent cerebrovascular events.
Accordingly, patients at such an increased risk are considered for prophylactic medical therapy to reduce the risk of a recurrent embolic event. These patients are commonly treated with oral anticoagulants, which potentially have adverse side effects, such as hemorrhaging, hematoma, and interactions with a variety of other drugs. The use of these drugs can alter a person's recovery and necessitate adjustments in a person's daily living pattern.
In certain cases, such as when anticoagulation is contraindicated, surgery may be necessary or desirable to close a PFO. The surgery would typically include suturing a PFO closed by attaching septum secundum to septum primum. This sutured attachment can be accomplished using either an interrupted or a continuous stitch and is a common way a surgeon shuts a PFO under direct visualization.
Umbrella devices and a variety of other similar mechanical closure devices, developed initially for percutaneous closure of atrial septal defects (ASDs), have been used in some instances to close PFOs. These devices potentially allow patients to avoid the side effects often associated with anticoagulation therapies and the risks of invasive surgery. However, umbrella devices and the like that are designed for ASDs are not optimally suited for use as PFO closure devices.
Currently available septal closure devices present drawbacks, including technically complex implantation procedures. Additionally, there are significant complications due to thrombus, fractures of the components, conduction system disturbances, perforations of heart tissue, and residual leaks. Many devices have high septal profile and include large masses of foreign material, which may lead to unfavorable body adaptation of a device. Given that ASD devices are designed to occlude holes, many lack anatomic conformability to the flap-like anatomy of PFOs. Thus, when inserting an ASD device to close a PFO, the narrow opening and the thin flap may form impediments to proper deployment. Even if an occlusive seal is formed, the device may be deployed in the heart on an angle, leaving some components insecurely seated against the septum and, thereby, risking thrombus formation due to hemodynamic disturbances. Finally, some septal closure devices are complex to manufacture, which may result in inconsistent product performance.
Various designs have disclosed septal closure devices made from a tube. These devices generally have a low septal profile in a delivery configuration, and a high septal profile in a deployed configuration. Upon deployment, these devices seal a septal defect. The unique design of these tube-made devices, however, requires an additional catch mechanism to catch the devices in their deployed configurations.
Various catch member designs have been proposed to catch the tube-made septal closure devices in the deployed configuration, temporary and permanently. Making such catch members capable of forming a temporary lock during partial deployment and a more secure permanent lock after full deployment has proved challenging. Some designs are not sufficiently reliable and other designs cannot be manufactured effectively. Finally, some designs, while workable on paper, do not perform satisfactorily in the human body.
The septal closure devices and techniques disclosed herein are designed to address these and other deficiencies of prior art design and techniques for delivering and retrieving such devices.
BRIEF SUMMARY OF THE INVENTIONIn some aspects, the present invention includes several delivery devices and techniques for delivering an implant into a desired location within the body. This delivery technique relates particularly to, but is not limited to, a septal occluder made from a polymer tube. These delivery techniques, in addition to use with septal occluders, can be applied to other medical devices, such as other expandable devices constructed to be delivered in a reduced profile configuration to an expanded profile or delivered configuration.
Catch members may be used to deploy and keep the device in place. According to some embodiments, the catch member maintains a reduced axial length of the device when the device is in the deployed configuration. Also, varied constructions could be used to maintain the axial dimension of the device, such as different locking mechanisms. Preferably, the catch member secures both sides of the device in the reduced profile configuration with a single element. Generally, during the delivery stage, the catch member has a smaller diameter at its proximal end compared to the diameter of the proximal end of the occluder. This configuration allows the proximal end of the occluder to slide over the proximal end of the catch member during deployment sequence. This may be achieved by compression of the proximal end of the catch member, by expansion of the proximal end of the occluder, or a combination of both. In a catching configuration, the catch member generally has a greater diameter at its proximal end compared to the diameter of the proximal end of the occluder, which keeps the occluder in its deployed configuration.
In various embodiments, the catching configuration can be temporary or permanent. A temporary catch configuration generally allows for the catch member to release, while a permanent catch configuration generally is not designed for release. Some embodiments have a temporary catch configuration, which allows for confirmation of proper deployment, and a permanent catch configuration, that is engaged when proper deployment is confirmed.
In certain embodiments, a permanent catch configuration can, for example, have a greater diameter at the proximal end of the catch member than a temporary catch configuration. A temporary catch configuration is generally preferred during evaluation and repositioning of a device, such as an occluder, while a permanent catch configuration is generally preferred once the device is deployed.
According to at least some embodiments, the catch member is formed from a tube. According to some embodiments, the tube includes a material selected from the group consisting of metals, shape memory materials, alloys, polymers, bioabsorbable polymers, and combinations thereof. In particular embodiments, the tube includes a shape memory polymer. In particular embodiments, the tube includes nitinol. In some embodiments, the tube is formed by rolling a flat piece of material into a tubular form. According to some embodiments, the catch member is formed by cutting the tube. The catch member is placed in its deployment configuration by fixing the axial length of the device, for example by preventing the proximal end of the device from sliding over the proximal catch element.
In some embodiments, the catch member uses a partially cut tube, with an axis of the proximal portion of the tube at an angle with respect to the axis of the distal side of the tube. A portion of the proximal side of the tube catches the proximal end of the device and keeps it in a deployed position.
In some embodiments, the catch member uses a series of protrusions at its proximal end. Once the protrusions are released, for example by removing the delivery wire, the protrusions project radially outward from the proximal side of the tube and keep the device in its locked position by preventing the proximal end of the device from sliding over the protrusions. In various embodiments, the protrusions are biased towards the proximal or the distal end of the catch member. In some embodiments, they may be twisted relative to the axis of the catch member.
In certain embodiments, the catch member may include a bump and pre-curved tabs at its proximal side. The bump is interrupted by a largely planar lumen slicing through the proximal side of the catch member. The lumen allows compression of the catch member with the delivery wire attached to provide a temporary catch configuration. In some embodiments, after the delivery wire is removed, the tabs automatically slide into the lumen to prevent or reduce compressibility of the catch member, thus providing a permanent catch configuration.
In a further aspect, the catch member may include a delivery wire and a catch tube that is threadedly secured to the delivery wire at two different locations. Each threaded connection has different pitches. Twisting of the delivery wire with respect to the catch tube creates a temporary or permanent catch depending on the selected design criteria. This system is especially adapted to construction with malleable materials. In another aspect, the protrusions can be threaded with different pitches to allow for modulation of the protrusion configuration by twisting the delivery wire.
These and other aspects and embodiments of the disclosure are illustrated and described below.
BRIEF DESCRIPTION OF THE DRAWINGSIn the Drawings:
Aspects of the present invention provide devices, delivery/retrieval systems and techniques for delivering such devices intended to occlude an aperture within body tissue. In particular, and as described in detail below, the described occluder may be used for closing an ASD, VSD or PFO in the atrial septum of a heart. Although the embodiments are described with reference to an ASD, VSD or PFO, one skilled in the art will recognize that the device and methods of the present invention may be used to treat other anatomical conditions. As such, the invention should not be considered limited in applicability to any particular anatomical condition. In addition, the systems and methods for delivery and retrieval, and for catching a device in a deployed state, that are aspects of the present invention may also be used in connection with other types of devices besides an occluder, in particular, devices having tubular profiles.
this application, “distal” refers to the direction away from a catheter insertion location and “proximal” refers to the direction nearer the insertion location. Additionally, the term “delivery configuration” refers to the configuration of a device, such as an occluder, when it has a reduced profile in a delivery sheath or catheter. The term “deployed configuration” refers to the configuration of the device, such as an occluder, when it has deployed from the catheter, such as at the desired implantation location.
The tube(s) 25 forming occluder 70 may be formed from a biocompatible metal or polymer. In at least some embodiments, occluder 70 is formed of a bioabsorbable polymer, or a shape memory polymer. Shape memory polymers can be advantageous so that the structure of the device assists in pressing the PFO tunnel closed. In other embodiments, occluder 70 is formed of a biocompatible metal, such as a shape memory alloy (e.g., nitinol). The thermal shape memory and/or superelastic properties of shape memory polymers and alloys permit occluder 70 to resume and maintain its intended shape in vivo despite being distorted during the delivery process. Alternatively, or additionally, occluder 70 may be formed of a bioabsorbable metal, such as iron, magnesium, or combinations of these and similar materials. Exemplary bioabsorbable polymers include polyhydroxyalkanoate compositions, for example poly-4-hydroxybutyrate (P4HB) compositions, disclosed in U.S. Pat. No. 6,610,764, entitled Polyhydroxyalkanoate Compositions Having Controlled Degradation Rate and U.S. Pat. No. 6,548,569, entitled Medical Devices and Applications of polyhydroxyalkanoate Polymers, both of which are incorporated by reference in their entirety.
The cross-sectional shape of tube 25 may be circular or polygonal, for example square, pr hexagonal. The slits 31 and 41 may be disposed on the face of the polygon (i.e., the flat part) or on the intersection of the faces.
The tube can be injection molded, extruded, or constructed of a sheet of material and rolled into a tube. The sheet of material could be a single ply sheet or multiple ply. The slits that form the struts could be cut or stamped into the sheet prior to rolling the sheet into a tube to connect the ends to form an enclosed cross section. Various geometrical cross sections are possible including circular, square, hexagonal and octagonal and the joint could be at the vertex or along the flat of a wall if the cross section is of a particular geometry. Various attachment techniques could be used to join the ends of the sheet to form a tube, including welding, heat adhesives, non-heat adhesives and other joining techniques suitable for in-vivo application.
The petal configuration is the deployed configuration. Occluder 70 can be secured in the petal configuration by a catch member that holds the ends of the tube 25 together, certain embodiments of which are described below. Use of the terms distal and proximal sides or portions 30 and 40, respectively, include the petals that are formed on the distal and proximal sides.
The embodiment described in conjunction with
In one alternate embodiment of an occluder, one end of each of distal petals originates from a central tube, while the other end originates from the distal end. Upon application of a force to the distal end to reduce the axial length, extended segments defined by slits in the tube bow and twist outward to form the distal petals in the distal side of the occluder. The movement of the segments during deployment is such that the segments rotate in an orthogonal plane relative to the axis of the device. The central tube may be constrained during the application of force, or any combination of forces sufficient to reduce the axial length of the tube may be applied. This embodiment is illustrated, for example, in
The transformable design of occluder 70 enables occluder 70 to be delivered in a low profile, tubular form and to be converted readily, i.e., by reducing the axial length, in place to the high-profile deployed configuration. Moreover, the conversion can readily be effected by forcing distal tip 39 and proximal tip 44 together. For example, distal side 30 and proximal side 40 of occluder 70 may be deployed in separate steps, or both distal side 30 and proximal side 40 of occluder 70 may be exposed (e.g., out of the delivery catheter) prior to engaging the catch member and deployed together as the catch member is engaged.
Occluder 70 may be prepared for delivery to an aperture 18a or 18b in any one of several ways. Slits 31 and 41 may be cut such that tube 25 bends into its intended configuration following deployment in vivo. Specifically, slits 31 and 41 may be cut to produce struts 32 and 42 of a thickness that facilitates the bending and formation of loops 32 and 42 upon the application of forces Fd and/or Fp during deployment. See
An embodiment of the catch member according to one aspect of the invention is illustrated in
Referring to
Referring now to
Referring now to
Occluder 224 can now be evaluated for proper deployment at the desired location, for example by fluoroscopy or any other suitable technique with the delivery system 220, including delivery sheath 154, delivery catheter 152, and delivery wire 156 attached or partially detached. The delivery system 220 can be partially detached by releasing the securement system provided by the threaded connection to the proximal tip of the occluder. As shown in
If the delivery or deployment is not satisfactory, while the delivery wire 156 continues to secure occluder 224, then the occluder can be retrieved or repositioned in the sequence shown in
As illustrated in
Referring now to
Referring now to
Another embodiment of the catch member according to the disclosure is illustrated in
By conditioning the axis of the proximal side 306 to be at an angle, for example at a right angle, with respect to the axis of the distal side 308, the proximal side 306 can be conditioned into a bent configuration, for example by annealing. An example of a step in this process is illustrated on
Referring to
Another embodiment of a catch member according to the disclosure is illustrated in
Referring to
The components of alternate embodiments of the catch member 400 described supra are described in connection with
Still referring to
During the occluder delivery process, the delivery wire 605 is advanced distally by threadably connecting threaded portion 613 of the delivery wire 605 and the threaded portion 616 of the catch member 600, and threaded portion 614 of the delivery wire 605 and the threaded portion 612 of the catch member 600. Because threaded portions 613 and 616 have a smaller pitch than threaded portions 612 and 614, this results in the proximal end 602 advancing in the direction, indicated by arrow A relative to the delivery wire 605, faster than the distal end 603. Bump 601 of the catch member 600 is therefore elongated, and the catch member 600 is reduced to its delivery profile. The resultant configuration is illustrated in
Materials suitable for use with this embodiment include materials that are able to be easily deformed, for example metals, alloys, polymers, or combinations of these and similar materials. Examples include, but are not limited to, bioabsorbable polymers such as polyhydroxyalkanoate compositions such as poly-4-hydroxybutyrate, bioabsorbable metals such as iron and magnesium.
A temporary catch configuration may be desired during deployment, retrieval, repositioning or evaluation of deployment of a device, such as an occluder. As illustrated in
In embodiments of the invention, including the embodiments specifically illustrated and described herein, the catching configuration can be temporary or permanent. A temporary catch configuration generally allows for the catch member to release, while a permanent catch configuration generally is not designed for release. Certain embodiments have both a temporary catch configuration, which allows for confirmation of proper deployment, and a permanent catch configuration, that is engaged when proper deployment is confirmed. A permanent catch configuration can, for example, have a greater diameter at the proximal end of the catch member than a temporary catch configuration and may be engaged only after the device has been properly positioned. A temporary catch configuration is generally preferred during evaluation and repositioning of a device, such as an occluder, while a permanent catch configuration is generally preferred once the device is deployed.
The embodiments and techniques described here are described preferably for use with a device made of a polymer and formed from a single tube, such that the tube is a single monolithic material. The catch mechanism can be all or partly monolithic or integral with the tubular structure, or there can be an absence of any type of bonding or rigid connection to the rest of the tubular structure, in which case there may be some spring force or other force that holds the locking mechanism in place. While the device is thus shown as being substantially formed from a single tubular body, the catch mechanism as described in the embodiments above could be used with other types of devices, including those formed from many pieces, and including devices formed from other materials, including metals, polymers, stainless steel or nitinol.
The term “bioabsorbable,” as used in the description above, is also understood to mean “bioresorbable.”
While the description above refers to wires, and while the term “wire” might convey a more rigid piece than a string, a suture or a filament, all these terms are essentially interchangeable, and further include embodiments in which the wire, string, suture or filament is a hollow tube or conduit to allow another wire, as needed, to pass through its longitudinal axis. Each wire, string, suture and filament can be composed of one or more wires, strings, sutures and filaments.
In cases in which the device is made of a polymer, it can be desirable to add an additive or coating to the material to make it radiopaque to make it more visible in a wider variety of imaging techniques.
It will be appreciated that while a particular sequence of steps has been shown and described for purposes of explanation, the sequence may be varied in certain respects, or the steps may be combined, while still obtaining the desired deployment or in some cases to effect deployment in a particular way. For example, the delivery sheath may be advanced or retracted at varying times and in varying degrees, the proximal and distal portions of the occluder may be deployed into the petal configuration in a different sequence, etc. In addition, the steps could be automated.
Claims
1. A collapsible medical device for occluding an aperture in a body, the medical device having a first configuration with a reduced profile and a second configuration with an expanded profile, the medical device being adapted to be delivered through a delivery system into a desired delivery location, the medical device comprising:
- a proximal side and a distal side;
- an occluder portion movable between the first and second configurations; and,
- a catch system for holding the medical device in the second configuration including a catch member with at least one arm disposed near the proximal end of the catch member, such that during deployment, the proximal end of the catch member is adapted to pass through an inner passageway of the occluder while the arm is depressed and to secure the device in the second configuration when the arm protrudes outside an outer diameter of the catch member.
2. The device of claim 1, wherein the arm is formed by cutting two parallel axial slits and one transverse slit into the catch member.
3. The device of claim 2, wherein the arm includes a bend and the bend causes the device to be secured in the second configuration.
4. The device of claim 3, wherein the arm is pre-conditioned in a bent position.
5. The device of claim 4, wherein the arm is pre-conditioned by annealing.
6. The device of claim 2, wherein the tip of the arm secures the device in the second configuration.
7. The device of claim 6, wherein the arm is straight.
8. The device of claim 6, wherein the arm is bent.
9. The device of claim 6, wherein the arm is bent into a V-shape.
10. The device of claim 2, wherein the catch system provides a permanent catch.
11. The device of claim 10, wherein the catch system further provides a temporary catch for use during deployment of the device.
12. A collapsible medical device for occluding an aperture in a body, the medical device having a first configuration with a reduced profile and a second configuration with an expanded profile, the medical device being adapted to be delivered through a delivery system into a desired delivery location, the medical device comprising:
- a proximal side and a distal side;
- an occluder portion movable between the first and second configurations; and, a catch system for holding the medical device in the second configuration including a catch member formed from a tube having a transverse, angled slit in the proximal side, such that during deployment, the proximal end of the catch member is adapted to pass through an inner passageway of the occluder while the tube is straight and to secure the device in the second configuration when the tube is bent at the cut.
13. The device of claim 12, wherein the slit is angled about 45 degrees from a longitudinal axis of the catch member.
14. The device of claim 12, wherein the catch member has a first axis and the proximal portion of the catch member when bent at the cut has a second axis at an angle to the first axis, and wherein the second axis is at an angle of approximately 90 degrees from the first axis.
15. A collapsible medical device for occluding an aperture in a body, the medical device having a first configuration with a reduced profile and a second configuration with an expanded profile, the medical device being adapted to be delivered through a delivery system into a desired delivery location, the medical device comprising:
- a proximal side and a distal side;
- an occluder portion movable between the first and second configurations; and,
- a catch system for holding the medical device in the second configuration including a catch member with two matched transverse slits in the proximal side such that during deployment, the proximal end of the catch member is adapted to pass through an inner passageway of the occluder and to secure the device in the second configuration when the portion defined by the two slits forms a protrusion.
16. The device of claim 15, wherein the protrusion is defined by reducing the axial length of the catch member and annealing.
17. The device of claim 15, further comprising an inner threaded portion for receiving a delivery wire and a stopper element disposed inside the tube for stopping the delivery wire when being screwed into the inner threaded portion.
18. The device of claim 15, wherein the protrusion is biased in the proximal direction.
19. The device of claim 15, wherein the protrusion is biased in the distal direction.
20. The device of claim 15, wherein the slits are angled relative to a longitudinal axis of the catch member.
21. The device of claim 15, wherein the protrusion is twisted relative to the longitudinal axis of the catch member.
22. A collapsible medical device for occluding an aperture in a body, the medical device having a first configuration with a reduced profile and a second configuration with an expanded profile, the medical device being adapted to be delivered through a delivery system into a desired delivery location, the medical device comprising:
- a proximal side and a distal side;
- an occluder portion movable between the first and second configurations; and,
- a catch system for holding the medical device in the second configuration including a catch member having a first outer diameter closer to the proximal end and having a second outer diameter further from the proximal end that is smaller than the first outer diameter, such that during deployment, the proximal end of the catch member is adapted to pass through an inner passageway of the occluder and to secure the device in the second configuration when a proximal end of the device catches on the first outer diameter.
23. The device of claim 22, wherein the catch member includes threads with two different pitches and the second outer diameter corresponds to threads with a first pitch.
24. The device of claim 22, further comprising a bump around the circumference of the catch member, wherein the first outer diameter corresponds to a diameter of the bump.
25. A collapsible medical device for occluding an aperture in a body, the medical device having a first configuration with a reduced profile and a second configuration with an expanded profile, the medical device being adapted to be delivered through a delivery system into a desired delivery location, the medical device comprising:
- a proximal side and a distal side;
- an occluder portion movable between the first and second configurations; and,
- a catch system for holding the medical device in the second configuration including a generally tubular catch member with a proximal portion and a proximal end, having a raised portion around its outer circumference on the proximal portion, tabs axially extending toward the raised portion, and a planar lumen intersecting the proximal end of the catch member, such that during deployment, the proximal end of the catch member is adapted to pass through an inner passageway of the occluder and to temporarily secure the device in an intermediate configuration by compression of the lumen and to secure the device in the second configuration when a proximal end of the device engages the raised portion, the engagement with the raised portion being secured by the tabs.
Type: Application
Filed: Dec 21, 2006
Publication Date: Jul 19, 2007
Applicant: NMT Medical, Inc. (Boston, MA)
Inventors: Steven Opolski (Carlisle, MA), Sean Forde (Watertown, MA), Stephanie Kladakis (Watertown, MA), David Callaghan (Boston, MA)
Application Number: 11/644,373
International Classification: A61B 17/08 (20060101);