Methods and devices described herein facilitate ablation patterns on the heart within a pericardial sac and without opening or deflating the lungs.

RELATED APPLICATIONS

This is a non-provisional of U.S. Provisional Applications 61/334,499 filed May 13, 2010 and 61/334,519 filed May 13, 2010, the entirety of each of which is incorporated by reference herein.

BACKGROUND OF THE INVENTION

Methods and devices for access devices to allow improved manipulation of organs and/or instruments within the body by creating working spaces within the body and adjacent to a target site. The methods and devices can be used in various parts of the body. One particular application includes the use of the access devices and methods to advanced devices to a surface of the heart to create atrial lesion patterns one or more atrial surfaces of the heart.

Scope based surgical tools (e.g., elongated cannula/tubular devices that allow viewing of internal body tissues) provide surgeons with an ability to view a surgical site through a lens/fiber optic/camera of the scope and also provide an ability to access the surgical site through a working channel of the tool. In some cases, a scope permits the surgeon to access internal body tissue by passing the scope through a small diameter opening, port, or trocar placed in a surface of the body.

In many surgical procedures, the surgeon must also dissect tissue to gain access to the intended target site. For example, U.S. Pat. No. 5,205,816 (the entirety of which is incorporated by reference) teaches a simple blunt dissector having a cannulated single lumen device with a mandrel inserted into the device for carrying a simple textured cloth that provides a textured surface. However, such basic devices are used in addition to the scopes that are used for such minimally invasive procedures. The additional blunt dissector requires an additional entry port or must be exchanged with other tools that are advanced through the entry site. In addition, a physician must manipulate a scope as well as the blunt dissection device.

Increasingly, scopes are being adapted to assist in the dissection of tissue to eliminate the need for an additional dissection device. Clearly, doing so reduces the number of devices that a physician must manipulate in the surgical area as well as the number of devices that are advanced through the body opening/port/incision. Many conventional devices rely upon balloon-type structures for dissection of tissue via expansion of the balloon or close-ended obturator-type structures that dissect via dilation via insertion of the closed end.

For example, U.S. Pat. No. 6,989,018 to Fogarty et al. (the entirety of which is incorporated by reference herein) discloses a balloon dissection apparatus having an elongate balloon that performs the tissue dissection. However, because this dissection relies upon somewhat uncontrollable expansion of the balloon (as the internal balloon pressure increases), the physician typically has less control over the amount of tissue dissection as compared to using a non-expanding structure to physically dissect tissue.

While obturator type devices avoid the problems with somewhat unpredictable dissection via balloon expansion, such devices are still not optimal. For example, U.S. Pat. Nos. 6,592,604; 6,752,756; and 7,001,404 (the entirety of each patent incorporated by reference herein) describe tissue dissection devices having with closed ends (where such ends act as obturators). The closed ends are generally translucent to allow for visualization therethrough. Yet, dissection of tissue occurs via dilation of the tissue using the closed end. U.S. Pat. No. 7,300,448 (the entirety of which is incorporated by reference herein) discloses a combination balloon dissector having an obturator associated with the balloon dissector assembly.

In any event, the balloon dissection or dissection via obturator dilation as described above do not provide the physician with the ability to tease or loosen adjoining tissue for a more controlled dissection of tissue.

Another drawback with conventional devices is their failure to accommodate removal of debris that is generated by the tissue dissection process. Such debris interferes with visualization through the scope. For example, during tissue dissection the resultant blood often smears the visualization scope. Alternatively, tissue debris (e.g., fatty deposits, etc.) present at the surgical site adheres to the visualization element. Even bodily fluids and the inherent body temperature can combine to produce condensation over the visualization scope. Often, a separate irrigation source must flush the distal end of the scope to maintain proper visualization. For example, U.S. Pat. No. 6,176,825 (incorporated by reference herein) discloses a cannula based irrigation system having a separate moveable irrigation member within the device.

Without the ability to irrigate the scope, a physician will be forced to repeatedly remove the scope from the surgical site and body for cleaning. Removal and cleaning of the scope increases the length and therefore the risk associated with the surgical procedure. Moreover, apart from the debris, in the obturator-type devices described above, the closed transparent end of the device often causes a distorted view of the working area.

Atrial fibrillation surgery is one example of a surgical procedure that relies upon dissection of tissue to access the target tissue site. To access the fibrillation surgery site, a physician typically dissects through tissue under direct visualization using an endoscope. Preferably, once the physician reaches the target site, the physician will establish a working channel or access path to the target site for the advancement of various surgical devices.

Accordingly, there remains a need for improved access devices that are configured to aid a physician during dissection of various tissues to access a target tissue site by providing the ability to gently dissect as well as establish space required to perform the intended procedure. The improved methods and devices described herein offer improved access to tissue regions within the body, especially those organs in the thoracic cavity. However, the devices and methods have applicability to any region in the body apart from the thoracic cavity.

For convenience, the following disclosure makes reference an endoscope as the scope based device. However, the inventive devices and methods described herein specifically include the use of any number of scope based devices generally similar to an endoscope; for example, any type of rigid or flexible tube with a light delivery system and a visualization source that transmits an image to the viewer, and (optionally) a working channel or lumen that permits delivery of an additional device through the scope.

SUMMARY OF THE INVENTION

Aspects of the invention are directed to devices and methods for less invasive treatment of atrial fibrillation. The subject coagulation probes for ablation and/or coagulation integrate suction to the coagulation mechanism so as to ensure consistent and intimate tissue contact directly between the coagulation mechanism and soft tissue. The subject coagulation probes may also have features allowing for advancement or positioning of the probes using a track-member as described below.

Increased tissue contact relative to that which can be achieved with known devices is capable of reversing convective cooling effects effect noted above by evoking a compression of the tissue that shortens the wall thickness (e.g., of the atria), ensuring consistent contact throughout the length of the electrode(s), and increasing the efficiency of thermal conduction from the epicardium to the endocardium. As such a more consistent and reliable lesion is created.

The method includes creating a lesion on a surface of a heart in a body of a patient during a minimally procedure. In one variation, the method comprises creating a minimally invasive incision to access a chest cavity of the patient; creating an opening in a pericardium of the patient and positioning a dilation device into the pericardial space; creating a path within the pericardial space by expanding the dilation device, deflating the dilation device, and then repositioning and re-expanding the dilation device; advancing a treatment device through the path to position the treatment device against a surface of the heart; and creating the lesion on the surface of the heart using the treatment device.

Variations of the method include advancing a guide wire into the pericardial space and where positioning the dilation device into the pericardial space comprises advancing the dilation device over the guidewire. The term guidewire, unless specifically stated otherwise, can mean any wire, catheter, or guide type device.

The method can further include withdrawing the dilation device from the guidewire, and where advancing the treatment device comprises advancing the treatment device over the guidewire.

Expanding the balloon can occur during creating of the lesion to separate an anatomical structure from the heart surface. For example, the phrenic nerve or esophagus can be separated or spaced from target tissue to minimize unintentional damage to such structures. Alternatively, or in combination, the method can include cooling tissue using the dilation device before, during or after creating of the lesion.

Furthermore, fluid can be delivered to the pericardial space to provide drugs or other substances to the treated area, or to maintain a fluid layer between the heart surface and the pericardium. Alternatively, the fluid layer can maintain be maintained to cool the surface of the heart or to provide visualization of the heart tissue by advancing a visualization device into the fluid layer.

In an additional variation, the method can further include drawing a vacuum in the vacuum source to cause a drop in pressure in both the vacuum lumen and the opening, whereupon placing the opening against the soft tissue creates a seal against the soft tissue to cause the fluid perfusion lumen to drop in pressure resulting in fluid flow from the fluid source through the fluid perfusion lumen across the opening and through the vacuum lumen, where when uncovered the opening prevents the perfusion lumen from reducing in pressure and preventing fluid flow.

The present disclosure also includes a surgical device for creating a linear and/or curvilinear coagulation lesion in a soft tissue of an organ. One variation of the device includes a body having a housing at a distal end and an expandable member; an energy transfer element located within the housing and having an elongate exposed portion at an opening in the housing such that the exposed portion of the energy transfer element is capable of creating the linear and/or curvilinear coagulation lesion in the soft tissue; a first diagnostic element assembly positioned adjacent to a distal section of the energy transfer element and opposite to the expandable member such that expansion of the expandable member against a body structure directs the energy transfer element against the soft tissue. A variation of the surgical device includes at least one diagnostic electrode located on a flexible base member.

The present disclosure also includes methods of perfusing a pericardial space. In one example, the method includes advancing a perfusion device through an incision in a pericardium, where the perfusion device comprises a first lumen terminating at a first opening and at least a second lumen terminating at a second opening, where the first and second lumen are fluidly isolated from each other within the perfusion device, and where the first opening is located proximally along the perfusion device relative to the second opening; positioning the first opening within the pericardial space and adjacent to the incision in the pericardium; delivering fluid through the second opening such that the fluid enters the pericardial space; and evacuating fluid from the pericardial space through the first lumen.

The method can also include securing the perfusion device to the pericardium. For example one or more balloons or expandable members can be used to secure the device within the pericardial space or about the pericardium.

The method can also include inserting a visualization device into the pericardium, where delivering fluid through the second opening permits direct visualization within the pericardial space. Placement of the perfusion device can occur using one or more radiopaque markers to allow for positioning of the first or second openings under non-invasive imaging. Moreover, the perfusion device can also be placed using direct visual imaging via insertion of a scope type device within or near the pericardial space.

The present disclosure also includes a perfusion device for delivering fluid to a pericardial space. In one example, the perfusion device includes a flexible shaft comprising at a first lumen terminating at a first opening and a second lumen terminating at a second opening, where the first opening is proximally located along the shaft relative to the second opening; a radiopaque marker adjacent to the first opening to allow for placement of the first opening within a pericardium; at least one expandable member located proximally along the shaft relative to the first opening, when expanded causes the perfusion device to be temporarily secured within the pericardial space. Variations of the perfusion device include with a second balloon or expandable member. Alternatively, an expandable member is not required in which case the device can be secured to the pericardial space via temporary suturing, clamping or through a resistance fit between the shaft of the device and local anatomy.

The perfusion device can optionally be coupled to a vacuum source and to a fluid source.

The subject matter of this application may be incorporated with the subject matter in the following commonly assigned patents, publications, and/or applications: the entirety of each of which is hereby incorporated by reference.

Variations of the access device and procedures described herein include combinations of features of the various embodiments or combination of the embodiments themselves wherever possible.

DETAILED DESCRIPTION

Methods and devices described herein provide for improved manipulation of organs and/or instruments within the body by creating working spaces within the body and adjacent to a target site. While the following disclosure discusses devices and methods for use in the thoracic cavity, such methods and devices can be applied to various body portions outside of the thoracic cavity. The methods and devices may allow for direct visualization along regions of anatomic structures not attainable with conventional approaches.

Furthermore, the methods and devices described herein may be used in conjunction with, or as an alternative to the conventional approaches described herein. For example, while some surgical approaches and procedures described herein rely on entry through the diaphragm of a patient to access a regions of the thoracic cavity, the surgical approaches and procedures can be combined with various other access methods.

FIG. 1shows one example of a tissue dissection access device10configured to dissect tissue using a number of different tissue dissection modalities. As described above, devices according to the present invention that provide a number of dissection modalities, e.g., frictional dissection, wedge-type dissection, and dilation type dissection, provides a physician with a number of options to access a target site during a minimally invasive procedure.

FIG. 1shows a device with several tissue section modalities. However, certain variations of devices within the scope of this invention can have any sub-combination of tissue dissection modalities.

Turning now to the illustrated variation, the first dissection modality comprises a dilation wedge tip22or beveled tip located at the distal end of the cannula12. The wedge shaped tip provides a mechanical wedge dissection modality as the tip22can be inserted into small openings in tissue and where advancement of the tip22mechanically dilates the opening.

The second dissection mode comprises a dissection surface24located on a side of the dilation wedge22. The dissection surface24provides a frictional or abrasion dissection modality as the physician is able to apply the tip to a tissue surface and gently dissect the tissue apart by relying upon the increased friction between the dissection surface24and the tissue. The dissection surface24can dissect tissue via axial movement relative to the tissue, by rotational movement, or a combination thereof. In certain variations, the dissection surface24can be configured to dissect tissue when moved in a single direction (as discussed below). For example, the dissection surface24can be configured to catch tissue as it is pulled in a proximal direction. This allows distal advancement without resistance. In any case, as the surface24moves against tissue, the increased friction of the surface24catches on tissue to gently separate fibers of soft tissue. Although the variations shown herein depict the dissection surface on an end of the dilation wedge22, the dissection surface24can be located on the cannula surface or even on a balloon dilation surface.

The third dissection mode comprises an expandable dilation balloon member26located on a surface of the cannula12. The dilation balloon member can be a distensible or non-distensible balloon. Generally, the dilation balloon member26can be used to create a temporary cavity or to separate tissue to a greater degree than a diameter of the cannula12. Any number of expandable members can be used in place of a balloon (e.g., a mechanical basket, axially aligned flexible strands, an expandable helical wrapped ribbon or wire, etc.)

FIG. 1also shows another feature of certain devices that provides a physician with unobstructed access to tissue sites that are exposed by tissue dissection. As shown inFIG. 1, the device10includes a cannula12having a working channel14extending therethrough and terminating at a distal opening16. In certain devices the distal opening16is in-line with an axis of the working channel14. This feature provides an ability to extend a medical device through the working channel14and directly into or adjacent the tissue being dissected. Such a feature is very beneficial when using the working channel to visualize tissue being or using the working channel to advance a device therethrough to treat a tissue site that is exposed by dissected tissue.

Accordingly, a physician can advance any such medical device from a proximal end18of the device10(as shown the device has an optional handle portion20on a proximal end) through the distal opening16and move the medical device relative to the distal opening10in alignment with an axis of the working channel14of the access device10. The handle can be configured to provide a textured surface to allow a physician to grip and manipulate the device.

The cannula shaft (or the portion of the cannula12between the wedge tip22and the proximal portion18or handle portion20) can be constructed to have a number of different configurations. For example, the cannula shaft can be flexible such that it can be deflected from an axis of the distal opening16. However, the cannula shaft shall have a column strength that allows a physician to push or advance the device into tissue or between organs. In some cases, the flexibility of the shaft allows flexion when medical devices are placed therethrough. This can reduce forces placed on the target tissue. Alternatively, use of rigid medical devices placed within the working channel14can change the flexibility of the shaft to increase the ease by which the device10is remotely manipulated within the body. The cannula12can be fabricated from any variety of medical grade materials. In one variation, the cannula is constructed from either silicone or C-Flex.

The device10also includes any number of fittings to couple the device to a fluid or vacuum source. As shown, the device10includes a first fluid connector28. In this variation, the fluid connector28can be connected to a vacuum or fluid source to remove fluids from the working channel14of the device or deliver fluids to the working channel14. The fluid connector28can also be connected to a vacuum source and fluid source simultaneously via the use of a two way valve or similar type of flow diverters (e.g., a two way stop cock). In those variations of the device10including an expandable dilation member26, a separate connector30can be provided to couple the dilation member26to a source of pressure (either air or fluid).

FIG. 2Adepicts a magnified view of a working end of the device10ofFIG. 1. As shown, the working channel14also includes a plurality of fluid ports32located therein. As noted above, the fluid ports32are coupled to a fluid source for delivering a fluid to irrigate the target tissue or a medical device located within the working channel14. The fluid ports32also allow a physician to remove debris or fluid from the working channel14.

In the variation of the device10shown, there are a number of fluid ports32. Additional variations of the device include a single fluid port32. However, multiple fluid ports32provide an advantage to generate a larger area of fluid flow within the working channel14. Such a feature improves the ability of the device10to clean a medical device located therein by providing a greater area to deliver or remove fluid. In the variation shown, the fluid ports32are located within the bevel of the dilation wedge22and are placed in alignment along an axis of the working channel14. However, the fluid ports32can also be arranged in a non-aligned manner or a random pattern. In addition, variations of the device10include fluid ports arranged on an exterior of the cannula12or proximal to the dilation wedge tip12within the working channel14.

FIG. 2Aalso depicts additional aspects of the device10. As shown, the dilation wedge22comprises a transition surface34along the distal opening16that provides a smooth transition to the outer surface of the cannula12. This feature aids in dilating tissue from a small opening to a larger opening that is the size of the outer diameter of the cannula12.FIG. 2Ashows another optional feature of a visualization element36located on a front face of the device10. Such elements can include a fiber optic scope or line as well as a CCD camera or any such visualization component as commonly known and used with various medical scopes.

In addition, although the working channel14and distal opening16are frequently depicted as having a circular cross section, variations of the device contemplate the working channel14and distal opening16to have non-cylindrical openings. For example, the cross-sectional profile can include oval or rectangular shapes where a height and width of the channel are not equal. The benefit of such configurations is that multiple devices can be advanced parallel within the working channel.

FIG. 2Bshows a partial cross sectional view of a variation of a working end of a device10according to the present invention. As shown, the device10includes a plurality of fluid lumens38,42coupled to respective fluid ports32,40. As noted above, fluid ports32can be placed in fluid communication with the working channel14to irrigate and remove fluids to or from the channel14for the clearing of debris from medical devices advanced within the working channel14. One or more fluid ports40also can be placed within the expandable dilation member26for pressurization of the member26to dissect or separate tissue. In certain variations; the fluid ports32located within the working channel14are angled or directed towards a proximal end of the device10(e.g., such that an axis of the port32forms an angle A that is less than 90 degrees. Directing the ports32in such a manner permits fluid to be delivered to the face of any device advanced within the working channel.

FIG. 2Balso shows an optional support member44located within a wall of the cannula12. The support member can be rigid or shapeable. A malleable or shapeable support44may be incorporated into a portion or an entirety of the cannula12to allow shaping the member into a desired configuration. The shape is selected to improve the ability of the device to direct the scope and instruments towards the desired site within the body (e.g., a region of the surface of the heart, or other anatomic structure). The support44can be placed in a support lumen such that the support44is slidable within the support lumen of the cannula12. The support44can be removable from the cannula12. In certain variations, it may be desirable to minimize a wall thickness of the cannula12to maximize the working channel14diameter and minimize the outer diameter of the cannula12. In such a case, the device will not be constructed to have a support member44or will not have the visualization element36shown inFIG. 2A.

FIGS. 3A to 3Dshow variations of different dissecting surfaces24for use with devices as described herein. In some variations a device can be equipped with more than one type of dissecting surface24. Moreover, a dissecting surface24can be placed on any portion of the device (including the expandable dilation member26). Although the figures illustrate the dissecting surfaces24on the bottom edge of the cannula12, the dissecting surfaces can extend over a full or partial perimeter of the cannula surface12.

FIG. 3Ashows a variation of a dissecting surface24that comprises a layer of material, such as a polymeric layer, a layer of cloth, or other surgical material that is textured and can be used to abraid tissue for dissection. In an additional variation, the material can comprise an absorbable surgical sponge material, such as gauze or other woven cotton. Alternatively, the material can be comprised of a polymeric material that is inserted into or onto the cannula12where the polymeric material comprises a sufficiently high coefficient of friction that the nature of rubbing the material against tissue results in abrasion and dissection of the tissue. The texture of the material abrades the tissue being dissected so that the dissection can be performed in either a distal or proximal motion of the cannula12.

The cannula12can have a relief section removed for insertion of the material24. In alternate variations, the material can be affixed to an exterior of the device. In certain variations, the material is non-absorbent and retains texture and stiffness as it encounters body tissue and fluids. The material can be glued onto the cannula12or the cannula12can have a textured or sharp surface to retain the material.

FIG. 3Bshows another variation of a dissection surface24. In this example, the dissection surface24is formed directly into the surface of the cannula12via a mechanical or chemical process. For example, the cannula12can be grounded, etched, swaged, bead-blasted, heat formed, etc. Alternatively, the textured dissection surface24could be formed in a mold such that the dissection surface24is directly molded onto the cannula12.

FIG. 3Cshows another variation of a dissection surface24formed from a plurality of surfaces that extend from a surface of the cannula12. For example, the surface24can be formed from granules deposited on the cannula12to form a sand-paper like coating. Alternatively, the surface24can comprise flexible extensions that engage and grip tissue when moved across the tissue.

FIG. 3Dshows yet another variation of a dissecting surface24. In this variation, the dissecting surface24comprises a directional dissecting surface24as shown by the saw-tooth configuration. The dissecting surface24generally does not engage the tissue when moved in a first direction (in this case a distal direction) but engages tissue when moved in a second direction (in this case a proximal direction).

FIG. 4Aillustrates a variation of a tissue dissecting device10coupled to a syringe46via a connector28. Optionally, the device10can be simultaneously coupled to a vacuum source48via a two way valve.

As described herein, the device10can accommodate a scope or medical device50such as an ablation device. Regardless of the medical device, as the tissue dissecting device10dissects tissue, various bodily debris and fluid often attach to the medical device advanced therethrough. In the case of a scope, the debris and fluid can prevent the scope from providing a clear image to the physician. In the case of energy delivery devices, debris attached to an energy transfer element can affect the energy transfer that should otherwise occur. As shown inFIG. 4B, injection of fluid through the fluid lumen38and fluid ports32into the working channel14bathes the end (or other area as appropriate) of the medical device50removing the debris and cleaning the device50.FIG. 4Cshows a state of the device10where suction is applied through the fluid lumen38to draw fluid and other debris into the fluid ports32. Placement of the fluid ports32within the working channel14.

FIGS. 5A and 5Billustrate placement of a pair of devices10within a body100of a patient in an exemplary procedure. It is noted that the device10can be used in any part of the body and through any incision or port in a minimally invasive manner. However, the device10can also be used in open surgical procedures.

FIG. 5Aillustrates creation of two incisions102104in the body100. In the illustrated example, the incisions are made in the abdomen of the patient so that the dissecting access devices10,11can then pass through a diaphragm of the patient to a posterior side of the thoracic cavity (as shown inFIG. 5B).

FIGS. 6A to 6Qshow one example where the device accesses a posterior surface of the heart106and where the multi-mode dissection attributes of the device enable a bi-atrial lesion pattern on a posterior region of the heart. Since the view is from a posterior surface, the notations of right and left are reversed.

As shown inFIG. 6A, the devices10are advanced through an epicardium using a left incision120and a right incision122. This allows a distal opening16of the devices10,11to be placed into the pericardal space around the left atrium124.

Next, as shown inFIG. 6B, a catheter60(such as a Foley catheter) passes from the right access device11to allow a guidewire62to be advanced over the left atrium124. The guidewire62is then retrieved into the left cannula10using a set of graspers or other similar device. Next, as shown inFIG. 6C, the guidewire62passes between the left11and right10access devices and ultimately extends out of the proximal ends of the access devices1011.

Turning now toFIG. 6D, with the guidewire62in place, a medical device64(such as an ablation device) is advanced over the guidewire62and through the right access device11. The end of the medical device64can be optionally viewed with a flexible scope, such as an endoscope or bronchoscope66which is also placed over the guidewire62from the left access device10. The medical device64can be any energy delivery, ablation, or coagulation device that may be advanced through the access device. Examples of coagulation devices that adhere to irregular contoured surfaces are disclosed below.

The access device64can be advanced over the wire62, to form coagulation lines150and151on the left atrium (as shown byFIG. 6E). Coagulation line152can be created by manipulating the right access device11and pulling the device back towards the right access device11.

FIG. 6Fshows repositioning of the right access device11with a rigid scope68placed therethrough. The combination as well as the features of the device described herein permit dissection through the first pericardial reflection126in front of Watterson's groove128. The scope allows the surgeon to visually navigate through the space as the access device11dissects the pericardial reflection126. This may be accomplished by rotation of the access device11, which allows a dissection surface to gently dissect the pericardial reflection126. As shown inFIG. 6G, once through the first pericardial reflection126, the cannula can advance into Watterson's groove128and used to dissect additional tissue to create space for the medical device (coagulation or ablation device). The physician can then advance the access device11to further dissect a second pericardial reflection130leading into the transverse sinus132.

FIG. 6Hshows a catheter60advanced into transverse sinus132. Once positioned, a larger sized access device13or regular cannula can be placed through the left incision120for securing a guidewire62placed in the Foley catheter (as shown inFIG. 6I). The larger cannula allows both a rigid scope as well as a grasping instrument to be placed within the cannula13for viewing and securing the guidewire62.

FIG. 6Jshows the site once the guidewire62extends around the pulmonary veins108and extends out of the body. The physician can then advance a treatment device64over the guidewire62from the right incision122and a flexible scope66advances over the guidewire62from the left incision122. This permits the physician to view the end of the treatment device64. The physician can then advance treatment device64and scope66around the guidewire62to create coagulation lesions153,154, and155(in that order, where lesions153and155cross lesions151and152. This set of lesions, along with lesions150,151, and152isolates the pulmonary veins from the remainder of the atrium124(as shown inFIG. 6K).

Turning now toFIG. 6L, to create lesions on the right atrium134, the flexible scope66can remain within the transverse sinus132and the guidewire62can be pulled back into the flexible scope—leaving the tip of the guidewire62visible to the scope66. The physician can then advance the scope66and guidewire62through the pericardial reflection130that was previously dissected and over to the right atrium134.

Next, as shown inFIG. 6M, an access device11can be inserted to view and accept the end of the guidewire over the right atrium134. The access device11can be placed either through the previously made right incision122or through another higher incision136in the pericardium that is over the right atrium134. The physician then advances the guidewire62until an end advances out of a proximal end of the access device11.

Once the guidewire62is accessible from the proximal end of the access device11, the treatment device64can be positioned using the guidewire62to create the first coagulation lesion156on the right atrium134(as shown inFIGS. 6N and 6O)

Next, the physician removes the guidewire62from the patient and two access devices10and11are inserted into either incision in the pericardium122or136. The physician situates the tips of the access devices10and11over the right atrium134as shown inFIG. 6P. The physician may need to further dissect the pericardial reflection126on the right atrium with access device10. Once the physician positions the access devices10and11, the physician passes a guidewire62between access devices. A Foley catheter, grasper or any such device (not shown) can be used to assist in passing the guidewire. Once the guidewire62forms a loop over the right atrium134, the physician places the treatment device64and the scope66through a separate access device10and11. The treatment device64and scope66can be placed through either access device10and11depending on the desired location of the coagulation lesion. The physician can then create the final coagulation lesion157as shown inFIG. 6R. The final coagulation lesions156and157each cross the previously made lesions on the left atrium124creating the pattern as shown.

FIGS. 7A-7Gillustrates another variation of a process to create a lesion (e.g., a bi-atrial lesion) pattern on a heart106. As show inFIG. 7A, this procedure uses minimal incisions10and11to access the chest cavity. Such a procedure avoids the need for invasive surgery to open an access the chest cavity or deflating the lungs.

The surgical incisions can be relatively small (e.g., 10 mm or less) to provide access creating atrial lesion patterns. The incisions can be paramedian subzyphoid incisions10,11. Additional variations of the procedure contemplate one or more incisions.

As shown inFIG. 7B, the physician makes two incisions120and122through the pericardium (not shown) and advances a balloon catheter70through one of the incisions. In variations with a single subzyphoid incision a single incision will be made through the pericardium. The balloon catheter70can include any commercially available balloon catheter (e.g., an angioplasty catheter) or it can include a catheter specifically designed for this procedure. In most cases, the balloon catheter will have a predetermined shape or will be non-distensible. However, alternate variations are within the scope of this disclosure.

Next, the physician inflates the balloon on the catheter70to create space or a path (via repositioning and multiple inflating and deflating of the balloon) to accommodate for insertion of a coagulation device and/or a flexible endoscope.FIG. 7Balso illustrates pericardial reflections110on the surface of the heart.

The physician then advances a guidewire62through one incision120and navigates it to the desired treatment area. In one variation of the procedure, the guidewire62can be steerable to allow for manipulation and improved positioning.

FIG. 7Dshows a coagulation device64advanced over the guidewire62. As noted above, the physician can manipulate the guidewire62via steering or other means to position the coagulation device64at the desired treatment location. Alternately, the physician can steer the coagulation device64itself in those variations where the coagulation device64incorporates or is coupled to a steering mechanism. A steerable coagulation device64permits a physician to use a standard guidewire to position the coagulation device64in the approximate treatment area, then the coagulation device64can be manipulated or steered to the desired location.FIG. 7Eillustrates positioning of the coagulation device64at a desired target location.

FIGS. 7F and 7Gillustrate use of the second incision122to advance a second device66to assist in the procedure. In some variations, the second device66comprises a flexible endoscope that enables the physician to have direct visualization of the working area or of the coagulation64device. As shown byFIG. 7G, steering of the guidewire62and/or coagulation device64allows for positioning of the device64and scope66to any desired location.

FIGS. 8A to 8Cillustrate using a guide wire62having steering capabilities. As shown inFIG. 8B, the guidewire can be directed around structures in the body and articulated63so that a coagulation device64can be advanced over the guidewire to position the coagulation device64at the desired location. Variations of the steerable guidewire can have radio-opaque markers to allow of visualization of location while using fluoroscopy or can employ other positioning/location means. The Coagulation device can also have radio-opaque markers to allow visualization under fluoroscopy. Additionally, the coagulation device64can have tracking elements built into the distal end to allow for 3 dimensional tracking of the device location. An example of a type of tracking system is described in U.S. Pat. No. 7,096,148 the entirety of which is incorporated by reference herein.

FIGS. 8D and 8Eillustrate another variation of a procedure where a coagulation device64is capable or is coupled to a steering mechanism. As shown, the coagulation device can be positioned around structures in the body to reach a desired treatment location.

FIGS. 9A to 9Eillustrate another variation of a procedure according to the present disclosure in which an expandable member is used to augment or assist in the creation of coagulation lesions. Those skilled in the art readily understand that the heart is enclosed in aconical sac of serous membrane, called the pericardium137, which encloses the heart and the roots of the great blood vessels. For sake of clarity, the pericardium is not shown as covering the heart in the illustrated figures. The pericardium137consists of an outer fibrous coat that loosely surrounds the heart and is prolonged on the outer surface of the great vessels except the inferior vena cava and a double inner serous coat of which one layer is closely adherent to the heart while the other lines the inner surface of the outer coat with the intervening space being filled with pericardial fluid. As shown, one or more pericardium incisions120,122are made in the pericardium137to allow advancement of a guide wire62over which a physician advances a dilation device. Alternatively, a physician can advance a steerable or otherwise maneuverable dilation device without a separate guidewire or with a guide member directly incorporated therein. The term guidewire is intend to include any wire, catheter, or guide type device whether steerable or non-steerable. Moreover, a coagulation device with a dilation member (as discussed below) can be advanced without a separate dilation device

As shown inFIG. 9A, the guide wire62or other dilation member advances within the pericardium. The physician expands the dilation member230, then reduces the dilation member so that it may be repositioned as illustrated inFIG. 9B. Doing so, begins to form a path or channel138within the pericardium. The physician then subsequently re-expands the dilation member230to extend the channel. This process is repeated as shown inFIGS. 9C and 9Dso that the physician forms the desired channel. In alternate variations, the dilation member230remains expanded and is withdrawn or advanced to form a channel. Moreover, support devices232can be introduced into the pericardium or thoracic cavity to deliver fluid or visualization to the device during channel creation or during actual treatment.

Once the channel is created, as the channel is created (in the event the dilation member is included on the treatment device), the physician can create the desired treatment lesions as described herein.

FIG. 9Eillustrates another use for a dilation member230. In this example, the dilation member230is used to dissect or separate anatomic structures140(e.g., the esophagus, a phrenic nerve, etc.) from the area to be treated in an effort to minimize collateral damage to the structure140. Alternatively, the expandable member230can be expanded or deploy a cooling fluid to preserve the anatomic structures140. In most cases the structures140are exterior to the pericardium. However, expansion of the dilation member230within the pericardium is sufficient to dissect or protect the structures.

Any of the devices described herein can be non-invasively imaged or tracked. For example, U.S. Pat. No. 7,096,148 to Anderson et al., the entirety of which is incorporated by references, discloses a magnetic tracking system that can be employed for tracking during the procedure.

Exemplary Treatment Devices

FIG. 10Aillustrates another variation of a coagulation device consisting of a probe200and a handle220. In this variation, the probe200again includes a shaft304having a housing309at a distal section of the shaft304. However, the variation ofFIG. 10Ashows a variation of a coagulation probe200having the capability of pacing and/or sensing as well as an element coupled to a single probe. As described above, variations of the coagulation device can employ any variety of shapes and sizes for the handles and/or housing. In the example shown, the handle220includes a plurality of connectors for connecting the probe to a power supply360, a fluid source355and a vacuum source350. The device can also include a strain relief324as well as any other features to accommodate flexibility of the shaft.

FIG. 10Billustrates a magnified view of the distal end of the probe200ofFIG. 10A. In this variation, the probe200includes a housing303having both an energy transfer element308and a plurality of diagnostic element assemblies202and206exposed at the opening310of the housing303. The illustrated variation shows a probe200having a coiled energy transfer element308with two diagnostic element assemblies202and206. However, additional variations of probes can include a non-helical energy transfer element308with any number of diagnostic element assemblies or even a single assembly. As shown, electrodes204on the diagnostic element assemblies202,206are positioned between the electrode or element surface (in this case the turns of the coil.) As described herein, the areas between the turns of the coil permit a vacuum force within the housing to secure the opening against tissue and draw the tissue into opening so that tissue contacts the energy transfer element308as well as the diagnostic electrodes204. The housing303can also include a flexible lip309or extension that assists in securing tissue against the opening310to form a vacuum. In some variations of the device it important that the electrodes204on the diagnostic assemblies remain electrically isolated from the energy transfer element308. This can be accomplished by positioning the diagnostic electrodes204within the spacing of the element308as well as electrically insulating the interior of the element308. As shown below, the probe303can include one or more liners319that can support the helical element308and/or provide additional insulation to electrically isolate the diagnostic electrodes204.

FIG. 10Cshows a perspective view of the energy transfer element308located within an opening310of the probe200. As shown, the energy transfer element308and diagnostic element assemblies202and206are recessed within the opening310so that when the lip309forms a seal against tissue the tissue is drawn into the opening310and engages the element308and electrodes204of the diagnostic assemblies202and206.

FIG. 10Dillustrates a perspective view of a steerable catheter234with a rapid exchange tip236that accommodates a guide wire62. The guide wire can advance through the treatment device200allowing the physician to use conventional techniques to advance the device200through the channel or into the epicardial sac.FIG. 10Eillustrate a bottom view of the steerable catheter234and treatment device200ofFIG. 10D.

FIG. 10Fillustrates a side-cross sectional view or a probe200. As illustrated, an elongate shaft4contains an elongate housing303. The housing303includes an element308within the housing303, where the element308is exposed at the bottom of the housing303via an opening. In this variation, the element8is located within the main lumen6which is in fluid communication with the vacuum source350ofFIG. 10Asuch that it functions as a vacuum lumen. Fluid flows from a fluid source355and is drawn through the fluid perfusion lumen8across the opening and back into the vacuum lumen6. If seal is not formed against the soft tissue, then fluid does not flow. Accordingly, the confirmation of fluid flow (or the audible noise confirming a closed fluid circuit) allows the medical practitioner to confirm adequate tissue engagement between the device and tissue. Once adequate engagement is confirmed, the practitioner can energize the electrode during the fluid flow to create the lesion. Breaking of the seal between the opening and the tissue will stop the fluid flow. Accordingly, the presence of fluid flow can serve as confirmation of sufficient engagement with tissue.

The integrated vacuum coagulation probes provided by nContact Surgical, Inc., North Carolina are examples of devices that allow intimate contact specifically between a soft tissue surface and the energy portion of the device. In those examples, the electrode(s) used to transmit energy (radiofrequency or ultrasonic) is capable of heating the soft tissue until achieving irreversible injury making the soft tissue non-viable and unable to propagate electrical impulses, mutate, or reproduce. These integrated vacuum coagulation probe embodiments may be in conjunction with the access devices described herein to treat atrial fibrillation, ventricular tachycardia or other arrhythmia substrate, or eliminating cancer in lung, or other soft thoracic tissue by destroying target cells.

Examples of such probes are disclosed in commonly assigned U.S. applications, publications and patent cited above

Exemplary Dilation Devices

FIGS. 11A to 11Cprovide basic examples of dilation devices having dilation members230for use as described herein.FIG. 11Aillustrates a sample balloon catheter240with an expandable member230shown in an inflated state. The balloon can be configured to deliver fluids through the expandable member230. Variations of the balloon catheter240include distensible and non-distensible balloons.FIG. 11Billustrates a mechanically expandable basket device242having a dilation member230that comprises an expandable basket as shown inFIG. 11C. The basket device242can also be configured to deliver fluids through the dilation member230or through another port. Typically, the shafts of the devices is flexible to allow for navigation to the desired target site. Furthermore, any of the devices can accommodate a flush lumen to deliver or remove fluid from or near the target area.

FIG. 12Aillustrates another variation of a treatment device200as described herein that can advance over a guidewire62.FIG. 12Billustrates a front view of the device200ofFIG. 12A. As illustrated, the guidewire can enter and an exit at a working end of the treatment device200. Furthermore, variations of the device include a guide wire62having dilation members230placed thereon and as shown inFIG. 12C. This feature permits direct channel creation using the guidewire alone or as the treatment device200advances through the epicardium.

FIG. 12Dillustrates another variation of a treatment device200that includes an expandable member230that is incorporated at the working end of the treatment device200. As shown, the guidewire advances through the working portion as well to allow use of the guidewire and treatment device for creating the path or channel though the pericardium as described above.FIGS. 12E and 12Fshow side and front views respectively of the device200and dilation member230ofFIG. 12D.

Traversing the Epicardial Space

The ability to traverse the pericardial space under direct visualization and create linear lesions throughout the right and left atria has been confirmed clinically using the Numeris® Guided Coagulation Device manufactured by nContact Surgical. The vacuum-integrated device ensures energy is directed only against tissue engaged by the opening in the device that exposes the electrode. This orientation is confirmed under endoscopic guidance during the convergent procedure.

In those cases where there is a need for a pericardial window, a surgeon creates the paracardioscopic access and manipulates the devices using endoscopic visualization. To migrate epicardial ablation to the electrophysiology, the need for a pericardial window and endoscopic visualization can be eliminated.

As such a subxyphoid access as described herein and diagnostic features incorporated on the device allows access through the pericardium using a traditional pericardiocentesis approach, manipulation over a guidewire throughout the pericardial space, and assurance of device and electrode orientation using diagnostic electrodes capable of coupling to 3-D Navigation Systems and EP Recording System.

After percutaneously inserting a needle subxyphoid through the pericardium a guidewire is inserted into the pericardial space. Contrast is injected to confirm position of the guidewire in the pericardial space.

As shown inFIG. 13A, a balloon catheter70is advanced over the guidewire and into the pericardial access site. In one example, a 10 mm balloon is inflated to open the puncture through the pericardium to allow the coagulation device to pass without the need for a sheath or trocar. The balloon is repositioned (retracted or advanced) and inflated in sequential movements to create a channel through which the ablation device can be advanced over the guidewire62.

FIG. 13Bshows a radiological image of a coagulation device64(where only the coil is visible in the image) advanced over a guidewire62when positioned against a left atrial appendage. After obtaining access, the coagulation device can be advanced percutaneously over the guidewire and through the pericardial opening. The device can be manipulated along the guidewire into the desired ablation locations (atrial or ventricular). The device has excellent torque response and column strength to traverse throughout the pericardial space over the guidewire that directs the device along the pericardium.

Diagnostic electrodes incorporated along the ablation coil electrode of the device ensure the ablation electrode engages the desired cardiac tissue. The diagnostic electrode bipolar pairs are coupled to a 3-D Navigation system using impedance to provide location information. Electrograms can be obtained to determine tissue (atrial and ventricular) that the ablation electrode contacts and evaluate lesion creation by observing the reduction in electrogram amplitude throughout the ablation process.

The vacuum ensures the device contacts tissue, the electrograms reduce the need for endoscopic guidance and provide information on location and effect of lesion creation. The combination of both enables performing atrial and ventricular ablation through percutaneous, subxyphoid puncture which EPs are comfortable.

The following outline details an example of an access procedure in accordance with a subxyphoid approach:

1) Insert needle percutaneously through pericardium and into pericardial space

2) Inject contrast through needle to insure the end of the needle is in the pericardial space not in the heart or outside of the pericardial space.

3) Insert guide wire though needle, remove needle

4) Insert dilator over guidewire (any conventional dilator can be used, see below for examples of different types of dilators) to create opening or the catheter or a sheath

a. Dilatorsi. Dilators with balloons1. Additional features of balloons or other expandable mechanisma. Enable creating a channel by sequential inflation/deflation of the balloon along the access path.b. Separate anatomical structures from the hearti. Phrenic nerveii. Esophagusc. Cool the balloon during RF or other heating mechanism (or warm when using cryo) to protect collateral anatomy during endocardial ablationd. Insert endoscope into balloon to provide visualizatione. Inject contrast to show location of balloonf. Incorporate electrodes axially along balloon catheter to couple to 3-D navigation system to localize positiong. Dissect anatomic structures such as the transverse sinus to create a channelii. Dilator with splines

b. Create a channel (without a sheath) to introduce the catheter into the pericardial space

c. Use sheath to get access to the pericardial space this sheath stays in place

5) Creating multi-pole ports into the pericardium

a. Same access procedure

b. Reasons for multiple ports (sec multi port folder)i. Add a scope to visualize the deviceii. Add a “drain” to remove pericardial fluidiii. Add a circulating flush to create a layer of fluid between the heart and the pericardium1. Possible benefitsa. Separate anatomical structures from the hearti. Phrenic nerveii. Esophagus

b. Cool the ablation catheter for RF or other heating mechanism

c. Cool the epicardial surface during endocardial ablation involving RF or other heating mechanism (or warm when using cryo)

d. Add steroids or other pharmaceutical to help with the healing after ablation

e. Maintain visualization (aka arthroscopic procedures involving continuous irrigation with saline) within pericardial space

f. Create space to provide visualization within pericardial space

6) Positioning catheter onto the heart

7) Once the channel is created position Guidewire into desired location

a. Use steerable Guidewire to navigate to location

b. Use steerable sheaths to navigate Guidewire to locationi. Maintaining the Guidewire in placeii. Remove sheath and introduce catheteriii. Advance to desired location

c. Steerable catheter with a guidewire lumen to position the guidewirei. Remove steering catheter and introduce ablation device

d. Positioning catheter with the guidewire attached to the distal end.i. Positioning catheter stays in place and the ablation catheter is advanced over the wire. Fixed Guidewire (GW)

e. Rapid exchange steerable catheter with GW

f. Steerable Catheter can also have a distal balloon

8) Catheter can have steering to aid in positioning

9) Ablation catheter can have a “rapid exchange” lumen for the guide wire so a catheter can be placed proximal to the ablation location

10) Diagnostic electrodes aid in positioning

a. Ensuring we are in contact with the heart not pericardium

b. Pace to stimulate the phrenic nerve (if this happens do not ablate there)

c. Signal decrease as the tissue is ablated

11) Radio-opaque marker on the ablation side of the ablation catheter

12) Balloon on the ablation catheter opposite the ablation coils

a. The balloon can be filled fluidi. Radio-opaqueii. Circulation saline

Examples

FIGS. 14A to 14Fillustrate radiological images of exemplary procedures for subxyphoid introduction of coagulation devices.FIG. 14Aillustrates the insertion of a guided device into the pericardium over a guidewire62. The physician performs a pericardiocentesis and inserts a into the pericardial space. Then the physician advances a guidewire through the needle into the pericardial space. A balloon catheter70that is advanced over the guidewire is inflated to open the pericardial access site. The physician then retracts the balloon70to create a channel allowing for advancement of a coagulation or other treatment device over the guidewire and into the pericardial space.

FIG. 14Cshows an example of creation of right atrial lesions. The physician manipulates the treatment device200within the pericardium against the right atrium. The physician then positioned the device200is over the guidewire and along the right atrium. The devices200guidewire lumen (located 180° opposite the exposed electrode) is positioned away from the atrium and the vacuum applied from the device200pulls the exposed electrode against the atrium. Diagnostic electrodes along the Coil Electrode permit 3-D Navigation and ensure the ablation electrode engages the desired target atrial tissue.

FIG. 14Dillustrates creation of the left atrial appendage lesion. The physician manipulates the device200within the pericardium and against the left atrial appendage. This may be performed using the guidewire62. Next, the physician orients the guidewire lumen of the device200away from the left atrium so that the ablation or treatment element contacts the left atrium. The physician can use impedance based 3-D navigation to show the location of device200.

FIG. 14Eshows an image from a procedure that created a left ventricular lesion. The physician manipulates the device200within the pericardium and against the left ventricle. The physician then orients the guidewire lumen of the device200away from the left ventricle so that the ablation electrode is adjacent to the left ventricular surface. The physician can then use impedance based 3-D Navigation to shows the location of the device200.FIG. 14Fshows a device200that is used to create a left ventricular lesion in the manner described above and against a base of the left ventricle.

In each of the above cases, electrograms provide location information to ensure that the electrode engages the desired tissue. In addition, after creation of the lesion, the physician can use electrogram amplitude reduction to confirm lesion creation

In addition, these integrated vacuum coagulation devices may be used to heat soft tissue along the posterior heart surface resulting in heat-induced contraction of collagen in such tissue thereby resulting shrinking of said soft tissue. For example, heating the mitral valve annulus along the posterior atrio-ventricular groove may induce shrinking of the annulus thereby correcting mitral valve regurgitation. However, it is understood that the invention is not limited to the above described vacuum coagulation probes. Instead, any number of coagulation, ablation, or surgical devices may be used as required.

FIG. 15AtoFIG. 15Cillustrate a perfusion device useful in the procedures described above requiring perfusion of the pericardial space. However, the perfusion device described below is not limited to cardiac applications. Instead, the perfusion device can be used in any application requiring perfusion of a space, cavity or other body structure.

FIG. 15Aillustrates a working end of perfusion device. As shown, the working end terminates in a number of fluid delivery lumens252. The fluid delivery lumens252can be coupled to a fluid source at a proximal end of the perfusion device250. In use, the perfusion device250supplies normal or cooled saline or other fluid to the pericardial space. The perfusion device250can optionally include a guide wire lumen252.

The perfusion device250removes fluid via lumen256. Accordingly, the proximal end of evacuation lumen256can be coupled to a vacuum source or fluid collecting chamber at the proximal end of the device250. As shown, the fluid delivery lumens252extend further beyond the evacuation lumen256to allow for delivery of fluid and perfusion of the fluid at the target site. The fluid is removed only once the fluid reaches the evacuation lumen256. In some cases, the pericardium can fill with fluid before fluid leaves through the evacuation lumen256. The flow of fluid out of the fluid delivery lumens252and into the pericardial space can be controlled to maintain hemodynamic stability.

FIG. 15Aalso illustrates the perfusion device250as optionally including one or more balloons258and260or expandable anchors. As shown below, the balloons258and260can be inflated to secure about the pericardium to secure the device to the pericardium while creating a seal at the pericardial incision.FIGS. 16B and 15Cillustrate side and top views respectively of the fluid perfusion device250. The figures also illustrate the perfusion device250as having radiopaque markers266and268. While the drawings show two markers, any number of markers can be used.

FIGS. 16A and 16Billustrate another variation of a perfusion device250. In this variation, the evacuation lumen256does not extend to the end of the device250. In addition, the device250ofFIG. 16Adoes not include any balloons or anchors.

FIG. 17shows an example of a perfusion device250inserted into an opening120in the pericardium137. Clearly, the shaft262of the perfusion device250can remain flexible to navigate through the body to the pericardial space146. Once the physician obtains percutaneous access to the pericardial space, the device250can deliver room temperature or cooled saline (or any other fluid) to the epicardial space146. The fluid can be perfused into and through the pericardial space from the fluid delivery lumens252as denoted by arrows142. The fluid is then evacuated at the evacuation lumen256as denoted by arrows144. The evacuation lumen256can be driven by a vacuum or by the increased pressure within the pericardial space146that results from the delivery of fluid. As shown, the proximal end of the device250can be coupled to a vacuum source (or fluid collection unit) as well as a source of fluid.

Perfusing the pericardial space146allows the physician to maintain hemodynamic stability. Moreover, the addition of saline or any fluid provides the ability to directly visualize within the pericardial space using scope or similar type device. In addition, the use of fluid can also help increase space between the epicardial surface and the pericardium through fluid distension. Yet another benefit of filling the pericardium is that the fluid can provide cooling to the tissue to prevent collateral damage to adjacent structures from heating due to the use of an ablation device.

FIG. 17also illustrates the use of an optional guide wire62for positioning of the perfusion device250. The guidewire62can be removed prior to delivery of fluid or can remain within the pericardial space146.

FIG. 18Aillustrates a magnified view of the device250secured to the pericardium137using the two balloons258and260as anchors. As shown, fluid delivery142occurs through the fluid delivery lumens252and the fluid is removed144via the evacuation lumen256. Clearly, the flow of fluid can be reversed (e.g., fluid is provided via lumen256and removed via lumen252).FIG. 18Billustrates a partial cross sectional view of the shaft262of the perfusion device250. As illustrated, this variation includes at least 5 lumens: one lumen252for each balloon; the evacuation lumen256, the fluid delivery lumen252and the guide wire lumen254.

Although the present methods and devices have been described in terms of the embodiments above, numerous modifications and/or additions to the above-described preferred embodiments would be readily apparent to one skilled in the art. It is intended that the scope of the present inventions extend to all such modifications and/or additions and that the scope of the present inventions is limited solely by the claims of the invention.