Patent Application
20050267495
The present invention relates generally to systems and methods for closing internal tissue defects, and more particularly to systems and methods for closing a patent foramen ovale or other defect with a deformable elastic clip.
By nature of their location, the treatment of internal tissue defects is inherently difficult. Access to a defect through invasive surgery introduces a high level of risk that can result in serious complications for the patient. Access to the defect remotely with a catheter or equivalent device is less risky, but treatment of the defect itself is made more difficult given the limited physical abilities of the catheter. The difficulty in accessing and treating tissue defects is compounded when the defect is found in or near a vital organ. For instance, a patent foramen ovale (“PFO”) or patent ductus arteriosus (“PDA”), is a serious septal defect that can occur between the left and right atria of the heart.
During development of a fetus in utero, blood is oxygenated by the mother's placenta, not the fetus' developing lungs. Most of the fetus' circulation is shunted away from the lungs through specialized vessels or foramens that are open during fetal life, but close shortly after birth. Occasionally, however, these foramen fail to close and create hemodynamic problems, which can ultimately prove fatal. During fetal life, an opening called the foramen ovale allows blood to pass directly from the right atrium to the left atrium (bypassing the lungs). Thus, oxygenated blood from the placenta may travel through the vena cava into the right atrium, through the foramen ovale into the left atrium, and from there into the left ventricle for delivery to the fetus' body. After birth, with pulmonary circulation established, the increased left atrial blood flow and pressure causes the functional closure of the foramen ovale and, as the heart continues to develop, this closure allows the foramen ovale to grow completely sealed.
In some cases, however, the foramen ovale fails to close entirely. This condition, known as a patent foramen ovale, can pose serious health risks for the individual, particularly if the individual has other heart abnormalities. For example, recent studies suggest an association between the presence of a patent foramen ovale and the risk of paradoxical embolism or stroke. See P. Lechat J et al., “Prevalence of Patent Foramen ovale in Patients with Stroke,” N. Engl. J. Med. 1988; 318: 1148-1152.
Still other septal defects can occur between the various chambers of the heart, such as atrial-septal defects (ASD's), ventricular-septal defects (VSD's), and the like. To treat such defects, open heart surgery can be performed to ligate and close the defect. Alternatively, catheter-based procedures have been developed that require introducing umbrella or disc-like devices into the heart. These devices include opposing expandable structures connected by a hub or waist. Generally, in an attempt to close the defect, the device is inserted through the defect and the expandable structures are deployed on either side of the septum to secure the tissue surrounding the defect between the umbrella or disc-like structure. Such devices, however, involve frame structures that often support membranes, either of which may fail during the life of the patient. Thus, the treatment of septal defects with these devices introduces the risk that the defect may reopen or that portions of the device could be released within the patient's heart.
Accordingly, improved systems and methods for closing internal tissue defects such as patent foramen ovale, patent ductus arteriosus and other septal and tissue defects are needed.
Improved systems and methods for closing internal tissue defects, such as septal defects and the like, are provided herein. Preferably, a delivery device is used to place an elastic clip over the defect, such that the elastic clip can at least partially close and preferably seal the defect with minimum risk to the patient. In one exemplary embodiment, the elastic clip has a first end, a second end and a body therebetween, where the body has a longitudinal axis extending along its lenght. The clip is preferably biased towards a relaxed state where the ends are adjacent to each other, for instance, in a ring-like shape, wherein upon application of a mechanical stress the clip is deformable from the relaxed state to a stressed state. In the stressed state the body can be straightened such that each end extends in a direction at least partially away from the other placing the body in torsion about the longitudinal axis. In another embodiment, the clip can have multiple coiled segments located adjacent to each other, where preferably at least one of which forms a 360 degree loop around at least one axis of the clip while in the relaxed state.
Also provided is a steerable delivery device for delivering the elastic clip to the tissue defect. In one exemplary embodiment, the steerable delivery device includes a flexible elongate tubular body having a distal end with an opening therein, a proximal end and an inner lumen, a flexible elongate tubular needle having a sharp, open distal end, a proximal end and an inner lumen, with the needle being slidable within the inner lumen of the body. The device also includes a flexible elongate pusher member having a distal end and a proximal end, with the pusher member being slidable within the inner lumen of the needle, wherein the opening in the distal end of the body is adapted or sized to allow the needle to pass therethrough. To provide steerability, the device can include a wire coupled with the distal end of the body and extending proximally along the body, in addition to a bias member housed within the body. The bias member can be configured to apply a bias to the body along a longitudinal axis of the body. Preferably, the wire is configured to bend the device upon application of a force to the wire in a proximal direction, allowing the distal end of the device to be steered into proximity with the tissue defect, as well as allowing the device to be steered through the patient's vasculature or other body cavities, if desired. An actuator can be provided on the proximal end of the device for controlling the movement of the needle, pusher member and/or wire.
Also provided is a method for closing a tissue defect, such as a septal defect, with a delivery device and elastic clip. In one preferred embodiment of the method, the delivery device is advanced into proximity with the septal defect, the device having a flexible elongate tubular body with an inner lumen and a distal end with an opening therein. A flexible elongate tubular needle having an inner lumen and a sharp, open distal end, is then slidably advanced from within the inner lumen of the body such that the needle pierces and penetrates a first and a second tissue flap of the septal defect. Preferably, a flexible elongate pusher member is housed within the inner lumen of the needle, the pusher member having a distal end in contact with an elastic clip also housed within the inner lumen of the needle. The pusher member is slidably advanced to deploy a first end of the elastic clip from the open distal end of the needle. The needle is then retracted from the tissue flaps such that the clip is deployed over the tissue flaps where it can at least partially close an opening therebetween.
Other systems, methods, features and advantages of the invention will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims. It is also intended that the invention is not limited to the require the details of the example embodiments.
The details of the invention, both as to its structure and operation, may be gleaned in part by study of the accompanying figures, in which like reference numerals refer to like parts. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, all illustrations are intended to convey concepts, where relative sizes, shapes and other detailed attributes may be illustrated schematically rather than literally or precisely.
FIGS. 2A-C are exterior views of exemplary embodiments of elongate flexible tubular needles for use in the delivery system.
FIGS. 5A-E are axial cross-sectional views depicting the delivery of an exemplary embodiment of an elastic clip to a septal defect with an exemplary embodiment of the delivery system.
FIGS. 6B-D are perspective views of an exemplary embodiment of the elastic clip, where:
The systems and methods described herein provide a deformable elastic clip and a steerable delivery device for use in the treatment of internal tissue defects. Preferably, these systems and methods are used to treat a septal defect where an undesired opening allows blood to shunt within the heart. Examples of such defects include PFO's, PFA's, ASD's, VSD's and the like. Frequently, the opening in the septum is surrounded by overlapping flaps of tissue that have failed to close properly. The steerable delivery device can be used to steer the distal end of the delivery device into proximity with the tissue defect and position the clip in close proximity to these tissue flaps. Once in position, the steerable delivery device can deposit the elastic clip over the flaps such that the clip can draw the flaps together and at least partially close or seal the opening. The clip can then remain engaged to the tissue for an indefinite period of time, holding the defect closed and giving the tissue the opportunity to form together and properly seal itself.
In this embodiment, catheter 102 includes a flexible elongate tubular body 106 having inner lumen 108 therein. Body 106 is preferably formed from a high-durometer, e.g., 55 D, material, but is not limited to such and can vary with the needs of the application. Catheter 102 also includes flexible elongate tubular needle 114, which is configured to slide within inner lumen 108. Needle 114 has sharpened, open distal end 118, as well as inner lumen 119, which can be sized to house clip 104. The distal end 110 of body 106 preferably has a tapered or rounded tip for facilitating atraumatic advancement of catheter 102 through the patient's body. Here, distal end 110 has a rounded, rigid distal tip 122 with opening 112 therein. Opening 112 is preferably sized to allow needle 114 to slide therethrough, while tip 122 is rigid in order to prevent needle 114 from piercing body 106.
Additionally, catheter 102 includes flexible pusher member 116, which also has an elongate shape and is configured to slide within inner lumen 119 of needle 114. Pusher member 116 can be optionally configured as a second catheter, with imaging or diagnostic capabilities and the like. Needle 114 and pusher member 116 are preferably formed from nitinol, but are not limited to such and can be formed from any material in accordance with the needs of the application.
Here, delivery system 100 includes three sections: distal section 142; intermediate section 144; and proximal section 146. Intermediate section 144 is located proximal to distal section 142, while proximal section 146 is located proximal to intermediate section 144. These sections are included in
In order to provide steerability to delivery system 100, catheter 102 includes deflection wire 130 and bias member 132 extending longitudinally within catheter body 106. Deflection wire 130 is coupled with guide member 120 at the distal end 110 of catheter 102 and extends proximally along the length of catheter body 106. Wire 130 can be coupled with guide member 120 in any manner and is shown here having a widened distal tip, which catches guide member 120 and prevents wire 130 from passing proximally through lumen 126 (shown in more detail in
Bias member 132 is housed within catheter 102 and located along intermediate section 144, preferably between guide members 120. In this embodiment, each end of bias member 132 abuts a guide member 120 and applies a bias force between them, although any abutment within catheter body 106 can be used. In one embodiment, a notch or receiving hole is placed in guide members 120 to abut bias member 132 and maintain bias member 132 in place. In a preferred embodiment, bias member 132 is a stacked teflon-coated coil spring having a round cross-section and placed over deflection wire 130. However, any type, shape or configuration of bias member 132 can be used according to the needs of the application.
As shown in
Deflection wire 130 is preferably located along a longitudinal axis of catheter 102 that is offset from central axis 134. When a force is applied to wire 130 in a proximal direction, i.e., by “pulling” wire 130, the distal end 110 of catheter 102 deflects in radial direction 136, which is depicted in
Catheter 102 can be steered in any direction within a patient's body in order to properly position distal end 110 in proximity with the tissue defect, or in order to navigate through the patient's vasculature. Because pulling deflection wire 130 will deflect distal end 110 in direction 136, catheter 102 may first require axial rotation in direction 137 to properly orient catheter 102. For example, while steering catheter 102 into proximity with the tissue defect, it may be desirable to deflected distal end 110 first to the left and then to the right in order to properly position catheter 102. In this case, after deflecting distal end 110 of catheter 102 to the left, the user would rotate catheter 102 by 180 degrees to properly orient catheter 102 before pulling wire 130 to deflect distal end 110 to the right. The distance the user pulls deflection wire 130 back determines the amount of deflection in the distal end 110. For instance, a deflection of 90 degrees would require more pull back than a deflection of 45 degrees. In this manner, distal end 110 can be properly positioned in proximity with the defect.
FIGS. 2A-C depict exemplary embodiments of needle 114 for use with steerable embodiments of delivery catheter 102 such as that depicted in
Flexible region 402 can be formed in needle 114 using various differing methods including electrical discharge machining (EDM), laser cutting, photolithography any type of patterning and the like. In addition, any desired pattern can be formed in flexible region 402.
Although not shown, delivery system 100 can be used with pre-shaped members, such as a pre-shaped body, needle, pusher member, deflection wire and the like. For instance, in one exemplary embodiment, needle 114 has a 90 degree pre-shaped curve near the distal end. Needle 114 can then be used in much the same way as a stylet, where insertion of needle 114 into inner lumen 108 of body 106 deflects catheter 102. Also, additional pre-shaped members can be used to counter other pre-shaped members. For instance, a pre-shaped pusher member 116 can have a 90 degree bend near the distal end, and can be inserted into lumen 119 of needle 114 such that the bend is oriented in the opposite direction. Thus, when pusher member 116 is fully advanced within needle 114 the opposing bends counteract each other and straighten catheter 102.
As discussed above, the systems and methods described herein can be used to treat numerous types of tissue defects including septal defects and the like. For ease of illustration, the following embodiments are described in the context of treating one particular type of defect, namely a PFO. However, it should be noted that although the following discussion takes place in this exemplary context, the systems and methods described herein are not limited solely to the treatment of a PFO and can in fact be extended to a wide variety of tissue defects.
To treat a PFO, catheter 102, with clip 104 housed therein, can be introduced into the patient's vasculature, e.g., from a percutaneous entry site in a peripheral vessel, such as the femoral vein, jugular vein and the like. Distal end 110 of catheter 102, including clip 104, can be advanced endoluminally within the patient's vasculature, e.g., through the vena cava (inferior or superior) and into the heart until distal end 110 is disposed within the a heart chamber, such as the right atrium. Alternatively, clip 104 can be introduced using an arterial approach as is commonly known in the art.
Catheter 102 is then navigated into proximity with PFO region 502, as depicted in
In one preferred embodiment, a guiding catheter (not shown) is first navigated into proximity with PFO region 502 and catheter 102 is then advanced within the guiding catheter. The guiding catheter can include an imaging device or it can be guided into place using other external imaging methods. Once catheter 102 is in position, needle 114 can be advanced distally from opening 112 into contact with PFO region 502, as depicted in
Once open distal end 118 of needle 114 has penetrated both tissue flaps 503 and 504, pusher 116 can be advanced distally within inner lumen 119 of needle 114 until one end of clip 104 protrudes from open distal end 118 and engages side 509 of tissue flap 504 as depicted in
In order to deploy clip 104, the user preferably holds pusher 116 in a static position relative to PFO region 502 while retracting needle 114 proximally over pusher 116. This maintains clip 104 in the proper position relative to tissue flaps 503 and 504, so that upon removal of needle 114, clip 104 properly closes opening 505. Alternatively, clip 104 can be delivered by allowing one end of clip 104 to engage tissue flap 504 on side 509 after being advanced from distal end 118, i.e., “catching” tissue flap 504 so that clip 104 remains in place as needle 118 is retracted from aperture 506. In this manner, clip 104 is deployed over PFO region 502 regardless of whether pusher 116 is held in a static position.
In order to facilitate the deployment of clip 104 by the user, an actuator, e.g., a handle device (not shown), can be provided on the proximal end of catheter 102. The actuator preferably permits controlled advancement of both needle 114 and pusher member 116 as well as relative movement between them. For example, the actuator can allow the distal end of the pusher member 116 to be disposed at a location within or external to sharpened distal end 118 of needle 114. The actuator can also provide controls to the amount of movement of needle 114, for instance, to prevent needle 114 from advancing too far past the tissue flaps prior to deploying clip 104.
Although not shown, the inner surface of needle 114 can optionally include one or more axially disposed grooves to guide the movement of clip 104. The groove(s) can maintain clip 104 in a relatively fixed radial orientation during advancement of catheter 102 through the patient's body and also during delivery, so that clip 104 does not rotate into a different orientation. Optionally, the distal end of pusher member 116 can have a notch or indentation (not shown), which engages with one end of clip 104 for assisting in the orientation of clip 104. The notch or indentation can prevent the rotation of clip 104, or alternatively, aid in rotating clip 104 through rotation of pusher member 116. The notch or indentation can be present without or in addition to any axial groove(s).
FIGS. 6B-D depict perspective views of one exemplary embodiment of deformable elastic clip 104. Shaded regions 603 and 605 denote the surface portion of clip 104, which engages each tissue flap. In order to more adequately engage the tissue flaps, shaded regions 603 and 605 can have a roughened surface texture that increases the frictional resistance when in contact with the tissue flaps. In should be noted that the position of shaded regions 603 and 605 can vary depending on the layout and shape of clip 104, as well as the type of tissue defect being treated.
In a preferred embodiment, clip 104 is biased towards a relaxed state as shown in
While in the relaxed state, clip 104 can rest substantially within the X-Y plane. However, the layout of clip 104 while in the relaxed state can vary with the needs of the application. For instance, in some applications it can be desirable for ends 602 and 604 to be partially deflected away from each other in the Z direction, in a direction opposite directions 607 and 608. This increases the amount of deformation needed to place clip 104 in the stressed state and, depending on the materials employed in forming clip 104, can result in a stronger return force generated by clip 104 when returning from the stressed state to the relaxed state.
Depending on the type and nature of the tissue defect, clip 104 can have many variations in design. Notably, clip 104 can have any shape as desired for use in the application. For instance, clip 104 can have a curved shape such as circular, ring-like, arcuate, elliptical, oval or eccentric, or clip 104 can have a multi-sided shape such as square, rectangular, hexagonal or pentagonal, or clip 104 can have any combination of shapes. Clip 104 can also be shaped symmetrically or asymmetrically. The length, width and cross-sectional shape of clip 104 can be chosen depending on the thickness of the tissue flaps. Also, the relative position of ends 602 and 604 in the relaxed state and stressed state can vary according to the amount of closing strength needed to close the tissue flaps. As mentioned above, the material characteristics of clip 104 can also be varied. In one embodiment, clip 104 can be formed from a bio-degradable material degrading over a length of time sufficient to allow the tissue flaps to seal themselves.
Clip 104 can also be composed of nitinol and configured to have an Austenite finish (Af) temperature close to that of the human body temperature. Thus, while in the Martensitic phase outside of the body, clip 104 can be deformed to the stressed state and readily loaded into needle 114. After clip 104 is placed within the body, it is heated past the Af temperature and changes to the Austensitic phase where clip 104 becomes biased towards the relaxed state. The ability of clip 104 to be configured such that it does not experience the biasing force when below the Af temperature, makes it easier, from a practical standpoint, for clip 104 to be placed in a wide variety of different stressed states. For instance, clip 104 can be straightened entirely with no curves or bends. This would then allow clip 104 to be used in a relatively smaller catheter 102 in relatively smaller anatomies.
In FIGS. 6A-D, clip 104 is shown curved around one central axis 611 with ends 602 and 604 adjacent to each other. Clip 104 can be shaped or curved around one or more different axes.
In the embodiments depicted in FIGS. 6A-D, body 606 is generally circular in a radial cross-section, i.e., a cross-section taken along a plane having longitudinal axis 610 as a normal. However, clip 104 is not limited to a circular cross-section and can have any desired cross-sectional shape. In one exemplary embodiment, clip 104 can have an elliptical cross-section, while in another exemplary embodiment, clip 104 can have an rectangular cross-section with at least one side longer then the others, which can be roughened to more adequately engage the tissue flaps.
The layout and shape of clip 800 provides certain advantages over the use of clip 104. For instance, coiled clip 800 can potentially close a PFO more easily than a clip 104 formed from the same material, due to the increased size and corresponding increased closing strength. This can be advantageous if the tissue flaps are relatively large and/or spaced farther apart. Because coiled segments 820 and 822 contact a greater surface area on the tissue flaps, the closing force is distributed over a wider area of tissue than with a similarly sized embodiment of clip 104. This can reduce the mechanical pressure placed on the tissue flaps per unit of surface area, allowing blood to be more easily circulated within the tissue flaps. However, the coiled configuration also exposes more surface area of clip 800 to the body, increasing the risk of bleeding. In environments where bleeding is a significant concern, the use of clip 104 can then be preferred.
It should be noted that each coiled segment can loop less than or greater than 360 degrees about one or more axes, the actual length of each coiled segment being chosen based on the needs of the application. In addition, clip 800 can include numerous coiled segments.
While the invention is susceptible to various modifications and alternative forms, a specific example thereof has been shown in the drawings and is herein described in detail. It should be understood, however, that the invention is not to be limited to the particular form disclosed, but to the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit of the disclosure. Furthermore, it should also be understood that the features or characteristics of any embodiment described or depicted herein can be combined, mixed or exchanged with any other embodiment.
