US 20060271030 A1
Methods for treating anatomic tissue defects such as a patent foramen ovate generally involve positioning a distal end of a catheter device at the site of the defect, exposing a housing and energy transmission member from the distal end of the catheter, engaging the housing with tissues at the site of the defect, applying suction or other approximating tool to the tissue via the housing to bring the tissue together, and applying energy to the tissue with the energy transmission member or to deliver a clip or fixation device to substantially close the defect. Apparatus generally include a catheter body, a housing extending from a distal end of the catheter body for engaging tissue at the site of the defect, and further adapted to house a fusing or fixation device such as an energy transmission member adjacent a distal end of the housing, or a clip or fixation delivery element.
1. An apparatus for fusing a layered tissue structure, the apparatus comprising:
a catheter body having a proximal end and a distal end;
a housing on a distal portion of the catheter body, the housing adapted to appose tissue and having an inside volume;
an energy transmission member positioned within the housing; and
means on the housing to facilitate the housing to expand and/or collapse thereby changing the inside volume of the housing.
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24. An apparatus for fusing a layered tissue structure, the apparatus comprising:
a catheter body having a proximal end and a distal end;
a housing on a distal portion of the catheter body;
an energy transmission member positioned within the housing; and
means associated with the housing for apposing the layered tissue structure to engage the housing against the layered tissue structure.
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46. An apparatus for fusing a layered tissue structure, the apparatus comprising:
a catheter body having a proximal end and a distal end;
a housing on a distal portion of the catheter body; and
an energy transmission member positioned within the housing, wherein the energy transmission is adapted to engage and appose tissue.
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58. A system for fusing layered tissue structures, the system comprising:
a catheter body having a proximal end and a distal end;
a housing on a distal portion of the catheter body;
an introducer sheath slidably disposed over at least a portion of the catheter body and having a main body, a proximal end and a distal end; and
an energy transmission member positioned within the housing.
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72. A method for fusing apposed layered tissue structures, the method comprising:
positioning a closure device at a first treatment site having a first layer of tissue and a second layer of tissue;
approximating the layers of tissue; and
applying energy from the closure device to the apposed layers of tissue thereby fusing the apposed layers of tissue.
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76. A method for closing a layered tissue structure, the method comprising:
implanting a first magnetic material on one side of the structure; and
implanting a second magnetic material on an opposed side of the structure;
wherein the magnetic materials create a magnetic force which compresses the layered tissue structure.
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The present application is a non-provisional of U.S. patent application Ser. No. 60/670,535 (Attorney Docket No. 022128-000700US), filed Apr. 11, 2005, the full disclosure of which is incorporated herein by reference.
The invention generally relates to medical devices and methods. More specifically, the invention relates to positioning closure devices, including energy based devices and methods for treatment of anatomic defects in human tissue, such as a patent foramen ovale (PFO), atrial septal defect (ASD), ventricular septal defect (VSD), patent ductus arteriosis (PDA), left atrial appendages (LAA), blood vessel wall defects and other defects having layered and apposed tissue structures.
The following is an example of how one particular type of anatomical defect, a PFO, is formed. Fetal blood circulation is very different from adult circulation. Because fetal blood is oxygenated by the placenta, rather than the fetal lungs, blood is generally shunted past the lungs to the peripheral tissues through a number of vessels and foramens that remain patent (i.e., open) during fetal life and typically close shortly after birth. For example, fetal blood passes directly from the right atrium through the foramen ovale into the left atrium, and a portion of blood circulating through the pulmonary artery trunk passes through the ductus arteriosus to the aorta. This fetal circulation is shown in
At birth, as a newborn begins breathing, blood pressure in the left atrium rises above the pressure in the right atrium. In most newborns, a flap of tissue closes the foramen ovale and heals together. In approximately 20,000 babies born each year in the U.S., the flap of tissue is missing, and the hole remains open as an atrial septal defect (ASD). In a more significant percentage of the population (estimates range from 5% to 20% of the entire population), the flap is present but does not heal together. This condition is known as a patent foramen ovale (PFO). Whenever the pressure in the right atrium rises above that in the left atrium, blood pressure can push this patent channel open, allowing blood to flow from the right atrium to the left atrium. Blood shunting also occurs in a patent ductus arteriosis (PDA), where a tubular communication exists between the pulmonary artery and the aorta. The PDA typically closes shortly after birth.
Patent foramen ovale has long been considered a relatively benign condition, since it typically has little effect on the body's circulation. More recently, however, it has been found that a significant number of strokes may be caused at least in part by PFOs. In some cases, a stroke may occur because a PFO allows blood containing small thrombi to flow directly from the venous circulation to the arterial circulation and into the brain, rather than flowing to the lungs where the thrombi can become trapped and gradually dissolved. In other cases, a thrombus might form in the patent channel of the PFO itself and become dislodged when the pressures cause blood to flow from the right atrium to the left atrium. It has been estimated that patients with PFOs who have already had cryptogenic strokes may have a risk of having another stroke.
Further research is currently being conducted into the link between PFO and stroke. At the present time, if someone with a PFO has two or more strokes, the healthcare system in the United States may reimburse a surgical or other interventional procedure to definitively close the PFO. It is likely, however, that a more prophylactic approach would be warranted to close PFOs to prevent the prospective occurrence of a stroke. The cost and potential side-effects and complications of such a procedure must be low, however, since the event rate due to PFOs is relatively low. In younger patients, for example, PFOs sometimes close by themselves over time without any adverse health effects.
Another highly prevalent and debilitating condition, chronic migraine headache, has also been linked with PFO. Although the exact link has not yet been explained, PFO closure has been shown to eliminate or significantly reduce migraine headaches in many patients. Again, prophylactic PFO closure to treat chronic migraine headaches might be warranted if a relatively non-invasive procedure were available.
Currently available interventional therapies for defect closure are generally fairly invasive and/or have potential drawbacks. One strategy is simply to close a defect during open heart surgery for another purpose, such as heart valve surgery. This can typically be achieved via a simple procedure such as placing a stitch or two across the defect with vascular suture. Performing open heart surgery purely to close an asymptomatic PFO or even a very small ASD, however, would be very hard to justify.
A number of interventional devices for closing defects percutaneously have also been proposed and developed. Most of these devices are the same as or similar to ASD closure devices. They are typically “clamshell” or “double umbrella” shaped devices which deploy an area of biocompatible metal mesh or fabric (ePTFE or Dacron, for example) on each side of the atrial septum, held together with a central axial element, to cover the defect. This umbrella then heals into the atrial septum, with the healing response forming a uniform layer of tissue or “pannus” over the device. Such devices have been developed, for example, by companies such as Nitinol Medical Technologies, Inc. (Boston, Mass.) and AGA Medical, Inc. (White Bear Lake, Minn.). U.S. Pat. No. 6,401,720 describes a method and apparatus for thoracoscopic intracardiac procedures which may be used for treatment of PFO.
Although available devices may work well in some cases, they also face a number of challenges. Relatively frequent causes of complications include, for example, improper deployment, device embolization into the circulation and device breakage. In some instances, a deployed device does not heal into the septal wall completely, leaving an exposed tissue which may itself be a nidus for thrombus formation. Furthermore, currently available devices are generally complex and expensive to manufacture, making their use for prophylactic treatment of PFO and other defects impractical. Additionally, currently available devices typically close a PFO by placing material on either side of the tunnel of the PFO, compressing and opening the tunnel acutely, until blood clots on the devices and causes flow to stop.
Research into methods and compositions for tissue welding has been underway for many years. Of particular interest are technologies developed by McNally et. al., (as shown in U.S. Pat. No. 6,391,049) and Fusion Medical (as shown in U.S. Pat. Nos. 5,156,613; 5,669,934; 5,824,015 and 5,931,165). These technologies all disclose energy delivery to tissue solders and patches to join tissue and form anastomoses between arteries, bowel, nerves, etc. Also of interest are a number of patents by inventor Sinofsky, relating to laser suturing of biological materials (e.g., U.S. Pat. Nos. 5,725,522; 5,569,239; 5,540,677 and 5,071,417). None of these disclosures, however, show methods or apparatus suitable for positioning the tissues of an anatomic defect for welding or for delivering the energy to an anatomic defect to be welded. These disclosures do not teach methods that would be particularly useful for welding layered tissue structures such as PFOs, nor do they teach bringing together tissues of a defect such that a tissue overlap is created that can then be welded together.
Causing thermal trauma to close a patent foramen ovale has been described in two patent applications by Stambaugh et al. (PCT Publication Nos. WO 99/18870 and WO 99/18871). The intent is to eventually cause scar tissue formation which will close the PFO. Blaeser et al. (U.S. Patent Publication US2003/0208232), describes causing trauma, or abrading, and holding the abraded tissue in apposition to allow the tissue to heal together. Using such devices and methods, the PFO typically remains patent immediately after the procedure, or abrasion, and only closes sometime later, or is treated and then held together to heal over time. Frequently, scar tissue may fail to form or may form incompletely, resulting in a still patent PFO.
In addition to PFO, a number of other anatomic tissue defects, such as other ASDs, ventricular septal defects (VSDs), patent ductus arteriosis (PDA), aneurysms and other blood vessel wall defects, atrial appendages and other naturally occurring cavities within which blood clots can form, and the like cause a number of different health problems (note that the term “defect” may include a naturally occurring structure that results a potential health risk such as the clot forming in the atrial appendage). U.S. patent application Ser. No. 2004/0098031 (Van der Burg), and U.S. Pat. Nos. 6,375,668 (Gifford) and 6,730,108 (Van Tassel et al.), the full disclosures of which are incorporated herein by reference, disclose a variety of techniques and devices for treating anatomic defects. In addition, the inventors of the present invention have described a number of improved devices, methods and systems for treating a PFO, many of which may be adapted for treating other anatomic tissue defects as well. For example, related patent applications assigned to the assignee of the present invention include U.S. patent application Ser. Nos.: 10/665974 (Attorney Docket No. 022128-000300US), filed on Sep. 16, 2003; 10/679245 (Attorney Docket No. 022128-000200US), filed Oct. 2, 2003; 10/952,492 (Attorney Docket No. 022128-000220US), filed Sept. 27, 2004; 10/873,348 (Attorney Docket No. 022128-000210US), filed on Jun. 21, 2004; 11/049,791 (Attorney Docket No. 022128-000211US), filed on Feb. 2, 2005; 10/787532 (Attorney Docket No. 022128-000130US), filed Feb. 25, 2004; 10/764,148 (Attorney Docket No. 022128-000510US), filed Jan. 23, 2004; 10/811,228 (Attorney Docket No. 022128-000400US), filed Mar. 26, 2004; and U.S. Provisional Application No. 60/670/535 (Attorney Docket No. 022128-000700US), filed Apr. 11, 2005, the full disclosures of which are incorporated herein by reference.
Despite improvements made thus far, it would be advantageous to have even further improved methods, systems, and apparatus for treating anatomic tissue defects such as PFOs and the other anatomic structures mentioned above. Ideally, such methods and apparatus would help position a closure device so that a complete seal of a PFO or other anatomic tissue defect can be achieved reliably and in a predictable fashion. Also, such devices and methods would leave no foreign material (or very little material) in a patient's heart. Furthermore, such methods and apparatus would preferably be relatively simple to manufacture and use, thus rendering prophylactic treatment of PFO and other tissue defects a viable option. Ideally, such methods and apparatus could also be used in a minimally invasive manner, with low profile for ease of introduction into the body, while effectively closing the PFO quickly, effectively and without causing damage to other portions of the body. When success of the closure procedure can be well predicted, physicians are more likely to recommend such a procedure prophylacticly. At least some of these objectives will be met by the present invention.
The present invention provides apparatus, systems and methods for treating anatomic defects in human tissues, particularly defects involving tissue layers where it is desired to weld or fuse the layers together, such as a patent foramen ovale (PFO). The methods will also find use with closing a variety of other defects which may or may not display layered tissue structures, such as atrial septal defects, ventricular septal defects, patent ductus arteriosis, left atrial appendages, blood vessel wall defects, and the like. For the treatment of PFOs, the apparatus will usually comprise endovascular/intravascular catheters having an elongate catheter body with a proximal end and a distal end. A housing may be positioned at or near a distal end of the catheter body, where the housing has an opening for engaging a tissue surface where the tissue defect may be present. Usually, the housing will be connectable to a vacuum source to enhance engagement of the housing against the tissue, and an energy transmission member, such as an electrode, may be positioned at or near the opening in the housing to apply energy to the tissue to effect welding and closure. For purposes of this disclosure, the terms sealing, closing, welding, fusing are used interchangeably to describe bringing tissues of a defect together so as to result in a substantial seal e.g. no physiologic leak of biological fluid or operator infused fluid across the sealed area. Although a variety of mechanisms may work to achieve this, the sealing or closing of the defect can occur via the presence or absence of a variety of biologic processes, some of which may be fusion or lamination of the tissue cells, layers or collagen, expression/combination of factors from the tissue that are expressed upon application of energy, denaturation and re-naturation of tissue elements, crosslinking, necrosis or partial necrosis or other cellular phenomena present at the treatment site upon application of the energies described herein, or combinations thereof.
Alternatively, instead of an electrode, the suction housing may be adapted for passage of a closure device such as a clip or fixation element that may be placed through the tissue of the defect while it is stabilized by the suction housing. The following description will often focus on PFO treatment, but at least many of the inventive embodiments may be employed for treating other tissue defects and in other contexts.
In a first aspect of the present invention, an apparatus for fusing a layered tissue structure comprises a catheter body with a proximal and distal end as well as a housing on a distal portion of the catheter body. The housing is adapted to appose tissue and has an inside volume. An energy transmission member is positioned within the housing and means on the housing facilitate expansion and/or contraction of the housing which results in a change in the housing inside volume.
The housing shape is adapted to effectively cover and appose a layered tissue structure. It is also is resilient and can be shaped to include a protruding nose. In some embodiments, the housing comprises hinged joints, and is adapted to maintain its shape sufficiently to maintain a flow of suction within the housing. The housing is collapsible into a small diameter introducer sheath, preferably 16 French or smaller. Additionally, the housing may include an electrode sized to treat a patent foramen ovale up to 30 mm in diameter and the electrode also can be collapsed in the same introducer sheath.
The means on the housing may be a structure over an exterior lip of the housing surrounding an opening in the housing, or the means may be a reinforcement in the roof of the housing which inhibits the housing from substantially collapsing while also facilitating the housing to maintain its shape sufficiently to maintain a flow of suction within, while the housing is apposed to the tissue structure and a vacuum is applied to the inside volume. The reinforcement may be a thickened region, a hardened region or a stiffening element. Alternatively, the reinforcement may comprise a metal structure spanning at least a portion of the roof. In other embodiments, the means comprises a ring that circumscribes a portion of the housing including a midpoint of the housing. The ring can also define a lower flange in the housing or the ring can circumscribe the lower portion of the inside volume.
The housing is expandable and fluid flow is a means to assist in the expansion. An electrode may also be a means to facilitate expansion. Other embodiments include a collapsing introducer which is able to collapse the housing prior to slidably disposing the housing into an introducer sheath. Typically, the collapsing introducer is shorter than the catheter body and the introducer sheath. In some embodiments, the length of the collapsing introducer ranges from about 0.5 to 10 inches long.
In another aspect of the present invention, an apparatus for fusing a layered tissue structure comprises a catheter body having a proximal end and a distal end, a housing on a distal portion of the catheter body, an energy transmission member within the housing and means associated with the housing for apposing the layered tissue structure to engage the housing against the layered tissue structure.
The means may comprise a clamp within the housing, deployed in response to the application of a vacuum to the housing. The clamp can include structure of the housing which collapses the housing walls to grasp tissue when vacuum is applied. The means may also comprise a movable element in the housing adapted to capture the layered tissue between the movable element and a portion of the housing. The means can also be a vacuum applied circumferentially to the housing, or in other patterns.
The means can also comprise a movable element having a plurality of apertures adapted to capture the layered tissue upon application of a vacuum. The movable element may include a second element disposed in the housing with a plurality of apertures, and the layered tissue is captured between the first movable element and the second element.
In the apparatus, the means may comprise a clamp adapted to penetrate the tissue structure and engage a rear side of the structure while the housing engages a front side of the tissue structure. The clamp can also include a penetrating tube and a deployable anchor which in some cases is a coil. The clamp could also be a magnetic element such as a permanent magnet or electromagnet, that provides a clamping force.
In other embodiments, the apposing means comprises at least one gripper on the housing which can engage the tissue when a vacuum is applied through the housing. The means may comprise a movable vacuum tube contained within the housing adapted to pull layered tissue toward the housing and against an element disposed on the housing having a plurality of apertures. The means can also be an elongate member having a deployable anchor which can be a pivotable puncture tube.
Often, the apparatus includes a collapsing introducer which is adapted to collapse the housing prior to sliding the housing into an introducer sheath. Typically, this collapsing introducer is shorter than the catheter body and the introducer sheath and can range in length from 0.5 inches to 10 inches.
In yet another aspect of the present invention, an apparatus for fusing a layered tissue structure comprises a catheter body with a proximal and distal end, a housing on a distal portion of the catheter body and an energy transmission member positioned within the housing, and adapted to engage and appose tissue. The member can be jaws which act as bipolar electrodes or the member can be a ring which snares tissue. In some instances, the ring serves as a return electrode. The member also can comprise a tissue penetrating electrode which may include a distal anchor to allow the electrode to be pulled back to appose the layered tissue structure. In other embodiments, the housing serves as a return electrode.
Often, the apparatus includes a collapsing introducer which is adapted to collapse the housing prior to slidably disposing the housing into an introducer sheath. Typically, the collapsing introducer is shorter than the catheter body and the introducer sheath, and typically has a length in the range from about 0.5 inches to about 10 inches.
In another aspect of the present invention, a system for fusing layered tissue structures comprises a catheter body having a proximal and distal end, a housing on a distal portion of the catheter body, an introducer sheath having a main body as well as proximal and distal ends, that is slidably disposed over a portion of the catheter body and an energy transmission member positioned within the housing. The energy transmission member and the housing are collapsible and slidably movable relative to the introducer sheath from a collapsed position within the introducer sheath to an expanded position beyond the distal end of the introducer sheath. Preferably, the introducer sheath has a softer durometer distal tip than the main body of the introducer sheath and this tip facilitates movement of the housing and the energy transmission member from the expanded position to the collapsed position within the introducer sheath. The softer durometer tip may be integral with the main body or it may be fixedly connected to the main body.
In the system, the introducer sheath may comprise a valve adapted to accommodate the housing and this valve also minimizes blood loss from the introducer sheath. Typically the valve is a hemostasis valve which may include one or more valve membranes such as disks which have a top surface and a bottom surface, both of which are scored. They may be scored orthogonally or at other angles.
The system often also includes a collapsing introducer which is adapted to collapse the housing prior to slidably disposing the housing into the introducer sheath. Often, the collapsing introducer is shorter than the catheter body and the introducer sheath, and typically is in the range of from about 0.5 inches to about 10 inches long.
In still another aspect of the present invention, a method for fusing apposed layered tissue structures comprises positioning a closure device at a first treatment site having a first layer of tissue as well as a second layer to tissue. The layers of tissue are approximated and energy is applied from the closure device to the tissue thereby fusing the layers of tissue. The method can also include electrophysiological monitoring of the layered tissue as well as adjacent tissue so that creation of aberrant conductive pathways is minimized. This can be accomplished by minimizing delivery of energy as well as minimizing the surface area of the active electrode and/or distance of the treatment zone to the AV node of a patient's heart.
In still another aspect of the present invention, a method for closing layered tissue structures comprises implanting a first magnetic material on one side of the structure and implanting a second magnetic material on an opposed side of the structure. The magnetic material create a magnetic force which compresses the layered tissue structure. Often, the layered tissue structure is a patent foramen ovale.
Devices, systems, and methods of the present invention generally provide for treatment of anatomic defects in human tissue, such as a patent foramen ovale (PFO), atrial septal defect (ASD), ventricular septal defect (VSD), left atrial appendage (LAA), patent ductus arteriosis (PDA), vessel wall defects and/or the like through application of energy. The present invention is particularly useful for treating and fusing layered tissue structures where one layer of tissue at least partly overlaps a second layer of tissue as found in a PFO. Therefore, although the following descriptions and the referenced drawing figures focus primarily on treatment of PFO, any other suitable tissue defects, such as but not limited to those just listed, may be treated in various embodiments.
I. PFO Anatomy
As mentioned in the background section above,
In addition to tunnel variations, the opening or frown F of the PFO and height of the PFO limbus can also vary.
Given the anatomical variations of a PFO, using a traditional guidewire to guide a closure device to the defect for treatment may not result in optimal placement all of the time. For example, in
Similarly, as illustrated in
Proper positioning is achieved when the closure device is placed optimally in relation to the defect to deliver the desired closure device. Closure of the defect following accurate placement of the device in a variety of PFO anatomies is illustrated in
In any of these procedures, a key aspect to performing closure of an anatomic defect is positioning the catheter or treatment device at the optimal location over the defect to be treated. Failure to place the device in the optimal location can result in incomplete closure of the defect, and require either a repeat application of the closure mechanism, or an additional intervention (e.g. second procedure). For example if a traditional single strand guidewire is placed through a PFO defect with a long tunnel, or a wide tunnel, it is difficult to predict, where in that tunnel the guidewire is going to reside and therefore even if a closure catheter is tracked over the wire that is through the PFO, it may not be directed to the center of the tunnel (in the case of a wide PFO), or to the mouth of the tunnel (in the case of a longer PFO tunnel). Various other misalignments can also occur depending on the size, width, angle, and/or depth of the targeted defect.
Various steps may be undertaken prior to performing a procedure to close a PFO, including sizing the defect, determining the orientation of the defect, assessing the depth of the defect, and determining any related or adjacent anatomic features such as a septal aneurysm. PFOs can range in size from about 1 mm to 30 mm although they are typically in the range from about 3 mm to 26 mm. Sizing of the defect could be accomplished by placing gradations or markers on a sizing device or a series of calibrated sizers could be utilized. Any of these can be adapted to be radiopaque or echogenic and therefore fluoroscopy, intravascular ultrasound, TEE, ICE and other visualization techniques may be employed to visualize and determine the foregoing so that the physician can better determine how best to size and place the closure device to achieve closure of the defect. For example, radiopaque markers mounted on a balloon inflated in the PFO would permit the PFO tunnel diameter to be observed and estimated under a fluoroscope. Other apparatus and methods for characterizing the tissue defect are described herein.
In addition, these visualization techniques may be employed in combination with the intravascular devices of the present invention to not only provide sizing information to the user, but in some cases provide a mechanical guide or rail, over which to accurately place a closure catheter. These features may be combined into one device, or a series of devices to assess the geometry of the PFO, place and position a closure device and ultimately deliver the closure therapy (clip, energy, sutures, etc.)
Another embodiment of a positioning device is shown in
With reference now to
Another embodiment of a mechanical expansion device used for positioning is shown in
Another mechanical expansion embodiment is shown in
With reference now to
In another embodiment shown in
Additional catheter features may also be employed in order to aid in placement and sizing. For example, in
In an alternative embodiment, a wire sizing, positioning and treatment device may also include an electrode or multiple electrodes for applying energy to the defect while it is in position or near the position to close the defect. The electrode may be formed or treated to be radiopaque to assist in sizing of the defect. Wire forms the bipolar electrode configurations, and sizes, orients and applies energy to close the defect. In
IV. Cathter Device
Referring now to
Fluid drip port 288 allows fluid to be passed into a suction lumen to clear the lumen, while the suction is turned off. A flush port with stopcock valve 298 is coupled with sheath 256. Flush port and stopcock valve 298 allows fluid to be introduced between sheath 256 and catheter body 260, to flush that area. Additionally, sheath 256 has a hemostasis valve 296 for preventing backflow of blood or other fluids. The distal tip of the sheath also has a soft tip 258 for facilitating entry and release of the catheter housing 262 during delivery. The catheter device 250 also includes a collapsing introducer 300 partially disposed in handle 268.
The collapsing introducer facilitates expansion and compression of the catheter housing 262 into the introducer sheath 256. By temporarily introducing the collapsing introducer sheath 300 into introducer sheath 256 the catheter housing 262 may be inserted into introducer sheath 256 and then removed, thereby allowing the introducer sheath 256 to accommodate a larger housing 262 without having to simultaneously accommodate the collapsing introducer 300 as well. The collapsing introducer 300 also has a side port for fluid flushing 302 and a valve (not shown) prevents fluid backflow. Locking screw 292 disposed in the handle 268 may be tightened to control the amount of catheter shaft 260 movement. Finally, an energy supply 254 is connected to the catheter via the electrical coupling arm 282 and a controller 252 such as a computer is used to control energy delivery. In operation, it may also be possible to de-couple the handle from the device if desired, or to remove the handle altogether.
The collapsing introduce 420 is illustrated next in
In alternative embodiments as described in detail below, additional features or fewer features may be included on catheter device 250. For example, a number of modifications may be made to catheter body distal end 266 in accordance with different aspects of the invention. Some of these may include lubricious liners or coatings on the device as well as heparin coatings for reducing thrombus. Different configurations for fluid delivery and vacuum are also possible. Additionally, a controller built into the power generator can alleviate the need for a computer controller, except for displaying treatment parameters. Therefore, the following description of embodiments is intended to be primarily exemplary in nature and should not be interpreted to limit the scope of the invention as it is described in the claims.
V. Optimizing Tissue Apposition
A. Housing Design and Other Tools
One aspect of a successful tissue weld of a defect to be treated, is the interface of the tissue at the therapeutic element (electrode, heating element, or mechanical closing mechanism). This interface may be impacted by the following variables, including any leaks in the housing, leaks or shunts in the anatomy (e.g. through the PFO), physical placement of the housing over the defect, deformation of housing against tissue interface and resulting housing volume, forces exerted by the housing, and the pressure used to appose the treatment site with the housing. Various embodiments are presented that may assist in tissue apposition within or against the treatment element for closing a PFO or other layered tissue defect. These designs may be used in conjunction with any of the defect closure devices described in the co-pending cases which have been previously incorporated by reference. Particularly, closure catheter devices such as those detailed in the co-pending applications Ser. Nos. 10/873,348; 10/952,492; and 11/049,791 may be enhanced by the following features.
Housing designs that maintain a sufficient chamber and features to grip and appose the tissue of the defect, and maintain the seal of the therapeutic element at the tissue interface may be desirable. A representative embodiment of a catheter housing 475 is shown in
Some features that provide a more resilient housing, and in turn allow greater tissue invagination upon vacuum activation, include: reinforcing the roof of housing, taller housing, and reinforcements in flange or skirt of housing. As depicted below, areas of the housing may be selectively reinforced to aid in sealing the treatment area within the device housing. In particular the “roof” of the housing may be formed of a thicker material (preferred material is silicone and it would be molded, the mold cavity would be constructed to allow more material to flow into the reinforced region). The reinforced roof allows the housing to remain somewhat tented during vacuum apposition. For the roof reinforcement, a stiffening element, such as spring steel or nitinol may be used in thicknesses ranging from, for example between 0.002″-0.005.″ Reinforcement in the roof region may also be achieved by molding a thicker region using the material of the housing, or adding material to the roof of the housing to make the reinforced area in the range of 0.005″ to 0.025″ thick, for example 0.01041 thick while still accommodating vacuum channels as described in copending application Ser. No. 10/952,492, the full disclosure of which has previously been incorporated by reference, and allowing the housing to collapse. Some of these features are incorporated into the embodiment of
At the midpoint of the housing between the main housing and the flange, stiffening elements 492 or extensions 496 may be employed in a similar manner (e.g. additional molded material or separate resilient extensions). For example, such extensions or reinforcement may have a thickness of between 0.005″ to 0.050″ and between 1-3 mm in height.
In addition, a semi-rigid ring 494 may be incorporated into the bottom of the flange to give hoop strength to the flange, especially when vacuum is applied via a lumen 487 in the catheter shaft 486 connected with the housing 485. In certain embodiments, a 1 mm×1 mm square in cross-section of material was molded at the bottom of the flange. In another embodiment, a nitinol ring was used, allowing the thickness of the region to be about 0.010″ or slightly smaller and not square in cross-section which allows for better collapsibility. In certain other embodiments, a polymer O-ring may be employed. Such additional housing material and reinforcement elements may be used alone or in combination with each other for the desired rigidity, while still allowing the housing to be collapsed within a guide catheter for deployment to and retrieval from the treatment site. The housing element 485 may be adapted to appose the tissue and keep it in place while a fusing or fixation element is brought into contact to secure the tissue. For example, the housing element 485 may be activated (suction applied) and then a catheter device containing a clip or fixation element may be advanced to the treatment site, and applied to the apposed tissue. Examples of fixation elements may be clips such as those described in pending applications Ser. Nos. 10/787532 (Attorney Docket No. 022128-000130US), filed Feb. 25, 2004; and 10/811,228 (Attorney Docket No. 022128-000400US), and further U.S. application Ser. No. 10/948,445 (Publication 2005/0070923) to McIntosh, U.S. application Ser. No. 10/856,493 (U.S. Publication 2004/0249398) to Ginn, and PCT publication WO/04/069055 to Frazier, the full disclosures of which are incorporated herein by reference.
Other housing configurations adapted to appose a layered tissue defect such as a PFO are illustrated in
A cone shaped or domed housing can provide greater tissue apposition, (optionally in combination with a “stepped” electrode as set forth in application Ser. No. 10/952,492, the full disclosure of which has previously been incorporated herein by reference). An example of the stepped electrode 504 may be seen in housing 500 of
A hinged housing may also provide better tissue apposition and defect closure by allowing the housing to better adapt to anatomical variations in the tissue defect. In one embodiment shown in
In another embodiment shown in
In alternative embodiments, a screen or slotted member may receive target tissue and oppose or “grip” the tissue during treatment. The screen may also be an electrode (monopolar/bipolar).
A recess in housing (or around skirt) 604 may assist in opposing or gripping tissue once the tissue is brought into the housing 600 using a vacuum. The screen 606 may be fixed to position tissue, or may be moveable as shown by the arrows in
In another embodiment shown in
As shown in
In a further embodiment depicted in
Further, the ring electrode in either configuration (cinched/snare ring or ring on outer housing) may be the return electrode in a bipolar system as shown in
With reference now to
In a further embodiment, an apposition device may be deployed separately from the treatment device into the left atrium, remote from the treatment site, to “bookend” the defect against treatment catheter and thereby create enhanced tissue apposition. Such a separately deployed apposition device would preferably be low profile to allow the remote puncture site to heal naturally, without requiring a therapeutic intervention to close the puncture.
Using a similar technique, another approach to applying the required tissue compression prior to defect closure utilizes magnetic attraction as shown in
The magnet and/or ferromagnetic components used for such an application can be in singular elements, or an array of smaller elements that may be more easily delivered to a remote location through a patients vasculature. For example, magnetic components 856 may be coated or formed for implant in a human body, loaded into a catheter 852 as shown in
Alternatively, as shown in
It is also within the scope of the present invention, as shown in
B. Isolating Treatment Site
The ability to appose tissue and create a treatment area conducive to welding tissue may be enhanced by the application of negative pressure, i.e. vacuum, at the treatment site. In addition, it may be desirable to infuse fluid into the treatment site for a variety of reasons.
Certain features of the housing may be constructed to assist in creating a robust seal at the tissue interface, and maintaining that seal for the duration of the treatment. To balance the housing features that allow for greater tissue apposition (e.g. a more resilient housing), the following features may be incorporated into the housing flange.
Additional “grippers” or protrusions 894 in the rim of housing 892 increase tissue apposition to the device 890. An additional vacuum lumen 896 in the housing rim 892 may also be useful to distribute the vacuum force toward the outer edge of the housing at the housing/tissue interface. This is illustrated in
Alternatively, as illustrated in
Another embodiment of the housing is illustrated in
Successful welds of heart defects may be achieved in the presence of infusate or drip fluids into the treatment region, as described in application Ser. No. 10/952,492, the full disclosure of which has previously been incorporated herein by reference, to mediate the moisture content of the treatment area and maintain patency of the catheter lumens. Infusate is used primarily to prevent blood from stagnating within a treatment device distal housing and thereby clotting. By providing constant infusate flow, stagnation is avoided. Heparin can also be added to the infusate to further minimize clotting. Alternatively, welds of heart defects have also been achieved with relatively “dry” tissue (low or little infusate).
For example, in the event that the use of an infusate is desired, the following variables may affect the efficacy of the tissue weld, namely, type of infusate (saline, D5W (Dextrose 5% and water) or G5W (Glucose 5% and water), rate of infusion, flow distribution at tissue interface (pattern, consistency), temperature of infusate and the like. In an exemplary range, infusion may be used in the following range 0-30 ml/min, and more particularly in the range of 1-10 ml/min. The infusate is then aspirated from the treatment site via the vacuum lumen. The vacuum suction creates a continuous draw of flush through the infusion lumen, passing through the distal housing, and back out the vacuum lumen, for example a passive or “closed loop” infusion. The infusate is then collected in a vacuum canister. Operation and further detail on the infusion of fluid can be found in related application Ser. No. 10/952,492 (Attorney Docket No. 022128-000220US), incorporated herein by reference. Adequate vacuum seal can be determined by observation of the distal housing under fluoroscopy (lack of movement, “flattening” as determined by imaging of fluoroscopic markers or echogenicity of housing), and observation of the color of the fluid suctioned to the vacuum canister (e.g. by a change from blood to clear fluid as the dominant fluid suctioned to the vacuum canister (fluid changed from red to clear). Although a complete seal is desirable, an example of a substantial seal that may still include an “acceptable leak rate” is in the range of 0-150 ml/min, for example, in the range of 1-30 ml/min. This leak may be attributable to physiologic phenomena, as well as mechanical issues with the housing seal against the tissue.
C. Energy Application for Defect Closure: Electrode Design and Energy Algorithm
Various parameters can be controlled to achieve the most advantageous result in closing a PFO or other defect in the heart with energy. As discussed above, greater tissue apposition can function to increase the likelihood of consistently welding the PFO tissues (primum and secundum), in a clinically acceptable procedure time. In addition to greater tissue apposition, various parameters related to the power algorithm can be controlled and optimized. Certain parameters include developing a feedback loop to ensure enough power is delivered to achieve the desired closure (plane of welding), that the power delivery does not lead to unwanted “pops,” that the power delivery does not lead to impedance spikes of the kind that prohibit additional power delivery to tissue within the specified procedure time, and the like. Others include design of the electrode, including the size, thickness and other physical features that effect energy delivery. The treatment device and the power system of the present invention are depicted in
The configuration of the electrode may play a role in optimum energy delivery. Certain features of an electrode or heating element that may affect closure (welding) include, element density, geometry, size, current density, surface features (gold plating for radiopacity, coatings, electropolishing of conductive surfaces), location of the power connection, and points of insulation on the element.
For example, a larger electrode, although able to treat a greater area of tissue, requires more power and therefore is less efficient, and may lead to additional conduction in the tissue to areas of the heart that the procedure is not intended to effect. An electrode design that is matched (size, capacity) to provide “localized energy density” to the intended treatment region can function to limit the power required to achieve the intended result, and therefore a more efficient, safer lesion is created.
For example, in
Masking may be applied by spraying or dip coating and typically employs a silicone layer, although other methods and materials are well known in the art. Alternatively, it may be desirable to design the masking element on the distal catheter housing such that it can be variable wherein the mask opening only exposes the desired amount of septal tissue to the chosen form of energy. The opening may be round, oval or other shapes, such as a crescent, to mimic the defect to be treated. Illustrative embodiments of this are shown in
In operation and illustrated in
In a further embodiment, a mesh electrode 1097 is shown in
In a further example and with reference to
The use of RF energy to generate a weld of a defect in conjunction with the use of a magnetic coupler to create opposing force could allow the RF system to be either monopolar or bipolar depending on the configuration. For example as depicted in
A preferred electrode embodiment is shown in
A floating electrode embodiment is illustrated in
In addition to applying energy for closure of a layered tissue defect, the electrodes of such a device can be designed to allow electrophysiology monitoring of the heart. Such mapping would permit a physician to determine if the treatment device is too close to sensitive areas of the heart, such as the AV node. Additionally, monitoring could be used to ensure that during treatment, aberrant conductive pathways were not being created. Mapping also allows power delivery to be controlled so that minimal required power is delivered and also permits the active surface of the electrode to be controlled and minimized so that treatment energy is not applied to an area greater than necessary.
As shown in
In the treatment of a PFO in a human heart, the following welding algorithms may be successfully employed to achieve closure or sealing of the PFO tissues using a range of parameters that utilize feedback to vary the time and power applied to achieve a tissue weld. The following are merely examples and not intended to limit the scope of the present invention. In a preferred embodiment, the algorithm would start at a low power (e.g. 1-10 Watts to 20-50 Watts) and gradually increase over time. This allows the controller to evaluate how the defect is responding to the application of energy. The objective of the algorithm is to deliver the maximum amount of power during a desired duration, while not over-treating the tissue. A software controller system may be employed to ramp the power over the designated time and to respond to the impedance readings or other user or manufacturer designated feedback or settings.
A schematic depiction of the power supply is depicted in
In one example of a tissue welding algorithm for PFO treatment, energy may be applied with an initial power setting of 20 Watts, and the power increased every 30 seconds by 5 Watts until 40 Watts is reached (“power ramp”). Following this initial ramp, energy may be applied until either 1) a total run time of 10 minutes is reached, or 2) an impedance spike occurs. If the total run time reaches 10 minutes the application of power is considered complete for purposes of this example. If an impedance spike is reached, an additional power ramp is reapplied until a total of five spikes have occurred or until a subsequent spike occurs after a cumulative run time of 7 minutes. The power ramp of this or other embodiments may also be incremental, e.g. ramp increased over 30 seconds, up to 5 Watts, until 40 Watts is achieved. Alternatively, the power ramp may begin at 20 Watts, increased to 25 Watts and maintained at 25 Watts until the application is complete (7-10 minutes), as shown in
In another example of ramping, the system operates to apply 15 Watts, ramped by 5 Watts every 30 seconds after initial 45 seconds, for 10 minutes or first impedance spike after 7 minutes. The overall number of impedance spikes is limited to 5. The system in this example includes passive fluid infusion. A solution of D5W, or other fluids such as normal saline may be employed for the infusion. An example of this treatment using a banded electrode (see description of banded electrode above), is shown in
In addition, it may be advantageous to alter the starting power, and time between ramps, for example allowing additional time between step ups in power, for example 60 seconds. In the example below, the initial power is 20 Watts, with a step up in power of 5 Watts every 60 seconds, to a maximum power of 40 Watts for a duration of 10 minutes. If an impedance spike is encountered, then applied power is reduced to 25 Watts for the remaining time up to 10 minutes, as shown in
Alternatively, an algorithm where energy delivery is initiated at a higher power (for example 50 Watts) and ramped down in response to impedance spikes or “pops” may be employed as shown in
The power may then be reduced by 7 Watts each time the impedance spikes after fewer than 2 minutes of power application (an impedance “spike” in this example, is characterized by a rise in tissue impedance to about 100 Ω). For example, if the power is set to 50 Watts and runs for 1 minute 30 seconds before spiking, energy application is stopped, power is reduced to 43 Watts and energy application is resumed. If the system then runs at 43 Watts for 3 minutes before spiking, the energy application is stopped only briefly before being reapplied at 43 Watts again. If there are spikes during the application of power, this process is repeated until a maximum cumulative run time of between 6 and 12 minutes is reached. If there is a spike after a cumulative run time of 6 minutes, the application of power is considered complete. If there is no spike, the energy application is continued at a power setting of 50 Watts for a maximum of 12 minutes.
An example of application of pulsed power is depicted in
In a preferred embodiment of the algorithm, power is delivered in multiple power runs or frames. In the first frame, RF power is set to 20 Watts and power is increased by 5 Watts every 60 seconds until a maximum of 40 Watts is obtained. If during this frame, impedance inflects and then returns to at least its initial value or appears to be reaching a spike then power is turned off. If power has been delivered for more than 7 minutes, application of power is terminated and a cool down step is initiated. If power has been delivered for less than 7 minutes, then additional power is applied after a 30 to 120 second pause.
In the second power run or frame, if RF energy was delivered for 180 seconds or less during the first run, the second frame may be started at 15 Watts. If the impedance has not exceeded its minimum from the second frame by 2Ω after 90 seconds, power is increased to 25 Watts. If after another 90 seconds, the impedance has not exceeded its minimum from the second frame, power is again increased to 35 Watts. If the impedance inflects and then returns to at least its initial value (of the current frame) or if impedance appears to be reaching a spike, power is turned off. Similar to the first frame, if power was on for more than a total of 7 minutes, power is turned off and the cool down step is initiated. If power has been run for a total of fewer than 7 minutes, then additional power should be applied in the third power run after waiting 30 to 120 seconds.
If more than 180 seconds of RF was delivered during the first frame then RF power is applied at 25 Watts. If the impedance has not exceeded its minimum from the second frame by 2Ω after 90 seconds, power is increased to 35 Watts. If the impedance inflects and then returns to at least its initial value (of the current frame) or appears to be reaching a spike, power is turned off. If power has been delivered for more than a total of 7 minutes, the power is turned off and the cool down step is initiated. Otherwise, if power has been delivered for fewer than 7 minutes, then additional power should be applied in a third power run, after waiting 30 to 120 seconds.
In the third power frame, RF power is applied at the last setting used in the second frame, e.g. either 15, 25 or 35 Watts. If impedance inflects and then returns to at least its initial value (of the current frame) or appears to be reaching a spike, power delivery is terminated and the cool down step is initiated.
In all power frames, when total power delivery time reaches 10 minutes, power is turned off and cool down is initiated. During cool down, RF power delivery is stopped and tissue temperature is monitored. Tissue is allowed to cool down for at least 30 seconds or until tissue temperature is 40° C. or lower before moving the treatment device.
In all cases, power is applied at least once, but may be applied additional times, in this example at most, three times, although power may be delivered to help “burn off” and remove the electrode from the tissue. Power may range from 100 Watts down to 10 Watts, for example from 50 Watts down to 25 Watts. The total energy delivered to achieve a weld employing any of the algorithm examples above, or any variations thereof may be in the range of 1,000 joules to 50,000 joules, in the case of a PFO weld, a possible range of 6,000-15,000 joules.
Algorithm—Other Approaches, Adjustments
It is within the scope of the present invention to modify the parameters of the algorithm to achieve the desired tissue weld, to account for a number of variables, such as those described earlier in this disclosure. For example, treating a PFO with a thin primum may require longer application of power, higher power, or a higher ramp of power, given the potential for energy dissipation through the thinner tissue. Treating a different defect such as a ASD or LAA may require bringing tissues together that result in a thicker sample to weld, and therefore the treatment may utilize less total energy or lower applied powers, for example 5-35 Watts, or may include additional applications of power at multiple regions along the defect to be sealed.
In addition, an algorithm utilizing a bipolar treatment device such as those described earlier, may use a ramping algorithm such as that set forth above, but may utilize less power somewhere in the range of 1-25 Watts, for example 5-10 Watts and more particularly 2-3 Watts in some cases. Treatment times for bipolar application can range from 1-20 minutes.
Although the foregoing description is complete and accurate, it has described only exemplary embodiments of the invention. Various changes, additions, deletions and the like may be made to one or more embodiments of the invention without departing from the scope of the invention. Additionally, different elements of the invention could be combined to achieve any of the effects described above. Thus, the description above is provided for exemplary purposes only and should not be interpreted to limit the scope of the invention as set forth in the following claims.