Triple balloon catheter

The present invention advantageously provides a method and system for cryogenically ablating large areas of tissue within the left atrium. In an exemplary embodiment a cryotherapy device includes a catheter body, a proximal end and a distal end; a first lumen; a second lumen; and an ablation element expandable from a first diameter to a second diameter, the ablation element having a surface portion that conforms to the uneven surface topography of the cardiac tissue. The ablation element can include one or more deformable balloon and/or flexible elements. The surface of the balloon can further be shaped by regulation of pressure within the one or more balloons. In an exemplary method, a tissue ablation device is provided and tissue in the left atrium is ablated with the device, whereby the ablation is created by freezing tissue.

CROSS-REFERENCE TO RELATED APPLICATION

FIELD OF THE INVENTION

The present invention relates to a method and system for interventional electrophysiology and minimally invasive cardiovascular treatment.

BACKGROUND OF THE INVENTION

Minimally invasive surgical techniques are known for performing medical procedures within all parts of the cardio-vascular system. Exemplary known procedures include the steps of passing a small diameter, highly-flexible catheter through one or more blood vessels and into the heart. When positioned as desired, additional features of the catheter are used, in conjunction with associated equipment, to perform all or a portion of a medical treatment, such as vessel occlusion, tissue biopsy, or tissue ablation, among others. Almost always, these procedures are performed while the heart is beating and blood is flowing. Not surprisingly, even though visualization and positioning aids are adequate for general placement of the device, maintaining the device in a selected position and orientation can be difficult as the tissue moves and blood flows, especially during a procedure that must be done quickly. As diagnostic and visualization equipment and techniques have continued to evolve, it has become possible to identify tissue areas to be treated with greater precision than the ability to quickly situate the device and effectuate treatment.

In addition to the challenges presented by moving tissue and flowing blood, the actual topography of the tissue being treated presents challenges. For example, unlike stylized drawings that depict the interior of the chambers of the heart as having smooth, evenly curved walls leading neatly to tubular blood vessels, the interior surfaces of the heart's chambers are irregular, uneven, and fibrous, as are the openings to blood vessels. Thus, for procedures that call for uniform tissue contact or tissue contact along an extended line, the structure and techniques for use of known devices can be deficient in some regards.

Even if a device is capable of being properly placed and held in position at the proper orientation; and even if the device is suitable for the tissue topography at the treatment site, the device can be nevertheless not fully suitable to achieve the desired outcome. By way of example, catheter-based devices are known for placement in the left atrium for ablating tissue within the atrium for the purpose of electrically isolating one or more pulmonary veins from the atrium in an attempt to increase the success rate of atrial fibrillation ablation.

In one type of prior art device disclosed in U.S. Patent Publication 2002/012836 A1, and as shown inFIG. 1(prior art), a sheath or guide catheter10is inserted into a blood vessel12that leads to the right atrium14of the heart16and passed through an opening created in the septum18that separates the right and left atria into the left atrium20. As shown inFIG. 2(prior art), a treatment element22is passed through the guide catheter10, deployed from an opening in the distal end thereof, and caused to form a substantially circular loop that is traverse or perpendicular to the longitudinal axis of the guide catheter10. A distal tip element24that extends distally beyond the circular loop is inserted into a pulmonary vein26as a guide and placement aid for the loop. As shown inFIG. 3(prior art), the treatment element22in the form of a loop is placed so that it encircles the opening or entry of the pulmonary vein26, known as the ostium, and tissue is ablated by microwave heating of the contacted tissue. The intended result is a substantially uniform circle of ablated tissue28as shown inFIG. 4(prior art). Also as shown inFIG. 4(prior art), such a device can be used in an attempt to create linear lesions30and32as well.

In practice, uniform, unbroken lesion lines are hard to create with such loop shaped ablation elements. Also, with respect to both the circular and the linear lesions formed by microwave ablation, it should be noted that the lesion formed is relatively narrow and has a width that corresponds to about the width of the catheter. Devices that use a laser to ablate tissue provide a similar result; namely, a very narrow lesion. Further, because a laser ablates a very narrow line of tissue, precise alignment of the device is very important. However, for the reasons set forth above, such precision is very difficult to achieve.

Catheter-based devices have been introduced that cryogenically ablate tissue. These devices are structurally very different from RF catheter based devices, and they are not similar or comparable variations on the same theme. Not only are the structures that encompass the respective ablation technologies different, but so are the devices for controlling the ablation process, evaluating the progress and extent of ablation, and ensuring patient safety.

For example, to create a large “ring” with an RF catheter it is typically necessary to make a series of adjoining spot lesions of relatively small size using small electrodes if one wishes to minimize RF output. This is significant because use of a large electrode and/or high power output can seriously injure tissue at other than the intended treatment site. This is especially important with respect to creating lesions in the pulmonary veins because the veins are juxtaposed with bronchial tubes and other sensitive pulmonary tissue within which it is highly undesirable to create ancillary lesions. By contrast, cryogenic ablation of tissues does not need to be accomplished “bit by bit” for fear of energy transmission into the affected tissue as the transfer of heat occurs at the medical device.

Nevertheless, given the uneven topography of the tissue, anatomical differences between patients, and the tortuous environment of the blood flowing through the vasculature mentioned above, secure placement of a cryogenic device against a pulmonary vein remains challenging. Moreover, if too much force is applied to the device and thus the tissue, risk of damaging the pulmonary vein increases—e.g., the vein could be deformed, ruptured, stenosed, or otherwise injured. In view of the above, it would be desirable to provide a medical device and treatment methods of use thereof that allow for secure placement against uneven, topographical surfaces such as those found in the left atrium of the heart while reducing or otherwise minimizing the risk of unwanted injury to the tissue region being treated.

SUMMARY OF THE INVENTION

The present invention advantageously provides a method and system for cryogenically ablating large areas of tissue within the left atrium. In particular, the present invention advantageously provides a medical device and treatment methods of use thereof that allow for secure placement against uneven, topographical surfaces such as those found in the left atrium of the heart while reducing or otherwise minimizing the risk of unwanted injury to the tissue region being treated.

In an exemplary embodiment a cryotherapy device is provided for modifying the electrophysiological properties of cardiac tissue having an uneven surface topography, wherein the device includes a catheter body having a substantially fixed diameter, a proximal end and a distal end; a first lumen for permitting passage of a cooling fluid from the proximal end to the distal end; a second lumen permitting return of the cooling fluid from the distal end to the proximal end; and an ablation element expandable from a first diameter that is substantially the same as the diameter of the catheter body to a second diameter that is at least twice the diameter of the catheter body, the ablation element having a surface portion that conforms to the uneven surface topography of the cardiac tissue. The ablation element can include one or more balloons and/or a flexible element that is deformed by moving the distal end of the catheter toward the proximal end of the catheter. The surface of the balloon can further be shaped by regulation of pressure within the one or more balloons.

The invention also includes a method for modifying the electrophysiological properties of cardiac tissue wherein a tissue ablation device is provided and tissue in the antrum of the left atrium is ablated with the device. In an exemplary method, only tissue in the antrum is ablated, and the ablation is created by freezing tissue. In addition, an exemplary method of a cryomaze procedure is provided which can be performed without the need to arrest the heart of the patient.

A cryogenic device is also provided, including a first substantially non-compliant balloon; a second substantially compliant balloon positioned distal to the first balloon; and a third substantially compliant balloon surrounding the first and second balloons. The first balloon may be constructed from PET, nylon or similar polymeric materials or composites, and the second balloon may be constructed from polyurethane, latex, or similar polymeric materials or composites. The first balloon may have an elastic modulus between approximately 2700 MPa and approximately 4250 MPa, while the second balloon may have an elastic modulus between approximately 50 MPa and approximately 600 MPa. The first and second balloons may be expandable independently of one another, and may not be in fluid communication with each other. The device may also include a cryogenic fluid supply in fluid communication with the first balloon, and a non-cryogenic fluid in fluid communication with the second balloon. Further, an interstitial region may be defined between the third balloon and at least one of the first and second balloons; and a vacuum source can be placed in fluid communication with the interstitial region.

A medical system is also provided, having a flexible catheter body; a first balloon disposed on the catheter body; a second balloon disposed distally of the first balloon, wherein the second balloon is more readily deformable than the first balloon; and a third balloon substantially enclosing the first and second balloons to the define an interstitial region therebetween.

A method for treating cardiac tissue is also provided, including positioning a medical device proximate an ostium such that a first balloon of the medical device abuts cardiac tissue proximate to the ostium and at least a portion of a second balloon located distal to the first balloon is positioned within the ostium, where the first and second balloons are substantially enveloped within a third balloon; expanding the second balloon to substantially occlude the ostium; and ablating cardiac tissue with at least one of the first and second balloons. Expanding the second balloon may include partially inflating the second balloon to substantially less than its maximum volume or diameter. The first balloon may define an elastic modulus at least five times greater than an elastic modulus defined by the second balloon.

DETAILED DESCRIPTION OF THE INVENTION

With respect to the treatment of atrial fibrillation, it is believed that the creation of a conduction block or an interruption of the electrical signal flow path from the region of the atrium and the pulmonary vein is an effective treatment for atrial fibrillation. Further, while it is believed that the creation of a narrow annular lesion at or very near the ostium of the pulmonary vein is an effective way to create a conduction block, notwithstanding the difficulty of making such a lesion, it is believed that creating one or more non-annular lesions in different locations is not only more readily accomplished with reliability, but it is more clinically effective.

In view of the preceding, the present invention provides apparatus and methods for modifying the electrophysiological properties of large areas of tissue rather than narrow, annular lesions at locations that are not confined solely to the ostium, although ablation of tissue near the ostium and/or in the atrial wall may be included. More particularly, the present invention provides devices that are suitable to cryogenically ablate regions of tissue in the antrum region of the left atrium in addition to other atrial tissue that may be deemed to be arrhythmogenic. The antrum is the area between the mouth or ostium of a pulmonary vein and the atrium. The antrum of each pulmonary vein is not identical in size or shape and the tissue topography renders it very difficult or almost impossible to create a ring of tissue. Accordingly, the present method calls for ablating large regions of tissue in the antrum to render the tissue electrically dysfunctional.

Referring now toFIG. 5, an exemplary system is depicted that is suitable for performing cryogenic antral ablation. The system generally includes a medical device, which may include an elongate, highly flexible ablation catheter34that is suitable for passage through the vasculature. The ablation catheter34includes a catheter body36having a distal end37with an ablation element38at or proximal to the distal end. The distal end37and the ablation element38are shown magnified and are described in greater detail below. The ablation catheter34has a proximal end40that is mated to a handle42that can include an element such as a lever44or knob for manipulating the catheter body36and the ablation element38. In the exemplary embodiment, a pull wire46having a proximal end and a distal end has its distal end is anchored to the catheter at or near the distal end37. The proximal end of the pull wire is anchored to an element such as a cam48in communication with and responsive to the lever44. The handle42can further include circuitry50for identification and/or use in controlling of the ablation catheter or another component of the system.

Continuing to refer toFIG. 5, the handle42can also include connectors that are matable directly to a cryogenic fluid supply/exhaust and control unit or indirectly by way of one or more umbilicals. In the system illustrated, the handle42is provided with a first connector54that is matable with a co-axial fluid umbilical (not shown) and a second connector56that is matable with an electrical umbilical (not shown) that can further include an accessory box (not shown). In the exemplary system the fluid supply and exhaust, as well as various control mechanisms for the system are housed in a single console52. In addition to providing an exhaust function for the ablation catheter fluid supply, the console can also recover and/or recirculate the cooling fluid. The handle42is provided with a fitting58for receiving a guide wire (not shown) that is passed into a guide wire lumen60.

Still referring toFIG. 5, the ablation element38is shown as a double balloon, wherein an inner balloon62is contained by an outer balloon64. A coolant supply tube66in fluid communication with the coolant supply in the console52is provided to release coolant from one or more openings in the tube within the inner balloon62in response to console commands and other control input. A vacuum pump in the console52creates a low pressure environment in one or more lumens within the catheter body36so that coolant is drawn into the lumen(s), away from the inner balloon, and toward the proximal end of the catheter body. The vacuum pump is also in fluid communication with the interface of the inner and the outer balloons so that any fluid that leaks from the inner balloon is contained and aspirated. Still referring toFIG. 5, the handle includes one or more pressure sensors68to monitor the fluid pressure within one or both of the balloons, blood detection devices70and pressure relief valves72. When coolant is released into the inner balloon62, the inner and the outer balloon64expand to a predetermined shape to present an ablation surface, wherein the temperature of the ablation surface is determined by the material properties of the specific coolant selected for use, such as nitrous oxide, along with the pressure within the inner balloon and the coolant flow rate.

Although the double balloon type ablation element38illustrated inFIG. 5can be an effective ablation tool,FIGS. 6-20illustrate other configurations for the ablation element that are capable of creating wide-area ablation patterns. For example, as shown inFIG. 6, a distal catheter portion74includes longitudinal elements76secured to a main catheter body78proximally, and to a tip element80, distally. A pull wire82or pushrod connected to a manipulation element44at the proximal end of the catheter and to the tip element80is movable longitudinally to move the tip element longitudinally. Electrodes84can be associated with one or more of the longitudinal elements for use in monitoring or evaluating electrical activity in tissue.

As shown inFIG. 7, the pull wire82has been pulled proximally to draw the tip element80toward the catheter body78. This causes the longitudinal elements76to deform and bend or bow radially outward. In one embodiment, each of the longitudinal elements76are provided with coolant injection tubes83disposed within a lumen defined by each longitudinal element, wherein coolant is recovered in the lumen which is in fluid communication with a low pressure source. Thus, each of the longitudinal elements76are cooled. Although the injection tubes83can all be supplied with coolant simultaneously, if desired, less than all of the injection tubes can be supplied with coolant to provide selectively radial cooling.

As shown inFIG. 8, the longitudinal elements can support a single or a double layer flexible member85that envelops them. Instead of, or in addition to coolant being circulated through the longitudinal members as discussed with respect toFIG. 7, coolant can be circulated through the chamber defined by the elements and the flexible member as described with respect toFIG. 5and the pull wire82can be used to deform the balloon by moving the distal end of the device proximally and distally.

FIG. 9is a front view of the device ofFIGS. 7 and 8and it illustrates the general shape of the periphery86of a lesion formed by cryoablation using the exemplary device in the expanded state. By contrast, spot or linear lesions can be created when the distal catheter portion74is in the non-expanded state illustrated inFIG. 6.

Referring now toFIG. 10, a catheter is provided with an ablation element88similar to the double balloon structure ofFIG. 5so that a distal tip region90is radially expandable to at least double the diameter of a catheter body92over a 2 cm to 3 cm length. The ablation element88is provided with a cryogenic fluid injection tube94having one or more fluid outlets96along its length in the distal tip region. Coolant is withdrawn though an outer lumen98at reduced pressure. A pull wire100or pushrod is used to deflect the distal catheter portion as shown inFIG. 11so that a large, distal facing surface102can be placed into contact with tissue. Although the balloon when inflated as shown inFIG. 10has a substantially greater radius than the catheter body92, when the pull wire100is used to draw the distal tip toward the catheter body as shown inFIG. 11, the balloon expands even further and presents a flattened tip that is suitable to blot large areas of tissue.

Referring now toFIG. 12, an ablation element104is provided with a distal portion106that is inflatable, one or more coolant injection orifices108and an exhaust lumen110. Referring toFIG. 13, the ablation element104is shown with a pull wire111or pushrod connected to a manipulation element at the proximal end of the catheter and the tip element12so as to be movable longitudinally to deflect the tip element off axis. In addition to providing a relatively long and wide ablation surface, the ablation element can be provided with a notch114to accommodate or fit over a ridge of tissue.

FIGS. 14a-16illustrate an embodiment for an ablation element, wherein first and second balloons,116and118, respectively, are enveloped by a third balloon120. The first and the second balloons116and118are in fluid communication with inflation and exhaust lumens as described above, wherein the third balloon120is only in communication with a vacuum or low pressure source. Each of the first and second balloons may be provided with a predetermined or substantially preformed shape or dimension and/or may be pressurized or otherwise inflated to provide an overall surface topography for the ablation element. Additional shaping may be provided by manipulation of a pull wire119as described above or by regulation of the pressure in the exhaust flow path.

FIG. 17aprovides an additional illustration of a triple-balloon configuration of the catheter34for the medical system. In particular, a first balloon150may be disposed on the elongate body of the catheter34. The first balloon150may be substantially non-compliant when in an inflated state. For example, the first balloon150may be constructed from polyethylene terephthalate (“PET”), nylon or similar polymeric materials or composites. Located distally of the first balloon150on the catheter34may be a substantially compliant, second balloon152. The second balloon152may be constructed from polyurethane, latex, or similar polymeric materials or composites. The substantially increased elasticity or compliance of the second balloon152as compared to the first balloon150may result in the second balloon152being more readily deformable than the first balloon150when inflated and/or in contact with a targeted tissue area. To facilitate the desired conformity or lack thereof, the first balloon may have an elastic modulus approximately five to fifty times that of the second balloon. For example, the first balloon may define an elastic modulus between approximately 2700 MPa and approximately 4250 MPa, while the second balloon may have an elastic modulus between approximately 50 MPa and approximately 600 MPa

The first and second balloons150,152may be inflatable and/or otherwise operable independently from one another. For example, the interior of the first balloon150may be in fluid communication with a first inflation lumen154and a first exhaust lumen156. These inflation and exhaust lumens may be in fluid communication with a fluid source and/or vacuum source, respectively, contained within the console52. The interior of the second balloon152may be in fluid communication with a second inflation lumen158and a second exhaust lumen160. The separate fluid flow paths of the first and second balloons enable them to be sealed or otherwise not in fluid communication with each other. These inflation and exhaust lumens may also be in fluid communication with a fluid source and/or vacuum source, respectively, contained within the console52. Of note, the first and second balloons may be in fluid communication with independent, separated first and second fluid sources162a,162brespectively, (shown inFIG. 5). The first fluid source162amay contain a cryogenic coolant or refrigerant, while the second fluid source162bmay contain a non-cryogenic fluid, such as saline, non-cooled gas, or the like.

The catheter34shown inFIG. 17amay further include a third balloon164surrounding, substantially enclosing or otherwise enveloping the first and second balloons. The third balloon164may be substantially compliant and be constructed from polyurethane, latex, or similar polymeric materials or composites, having a modulus of elasticity or flexibility substantially larger than that of the first balloon. The third balloon164may be disposed about the first and second balloons to define an interstitial region166therebetween, which may be in fluid communication with an interstitial lumen168. The interstitial lumen168may be in fluid communication with a vacuum source in the console52, and which may be the same or additional to the vacuum source(s) in fluid communication with either of the first and second exhaust lumens156,160.

Now referring toFIG. 17b, an exemplary method of use of the device shown inFIG. 17ais illustrated. In particular, the catheter34may be positioned and subsequently operated to thermally treat a targeted tissue area, such as an ostium170of a pulmonary vein in the atrium of the heart. For example, the catheter34may be delivered to or otherwise positioned within an atrium of a heart intravascularly or otherwise as described herein. The catheter34may be positioned such that at least a portion of the second balloon152is disposed within a pulmonary vein or other vascular conduit. The second balloon152may then be expanded or otherwise inflated to substantially occlude the pulmonary vein or other vessel in which it resides. The expansion of the second balloon152may be achieved by delivering a fluid, such as a non-cryogenic fluid, saline, or the like, from the second fluid source162bthrough the second inflation lumen154and into the interior of the balloon152. Further, as there may be variations in the size, shape or other dimensions of the vessel being occluded, the second balloon152may be selectively, controllably expanded to a fraction of its overall inflation/size capacity to obtain the resulting, desired occlusion. This partial inflation may be facilitated by monitoring the pressure within the second balloon and terminating inflation upon reaching a desired or predetermined pressure threshold value or range. Another example of providing a controlled, fractional inflation of the second balloon may include delivering a predetermined volume of inflation medium to the second balloon152to reach a predetermined or preselected inflation size (whether volume, outer circumference, diameter, or the like). In addition to the selective inflation dimensions of the second balloon152, occlusion may further be facilitated by the complaint nature of the second balloon152, described above. Having a sufficiently-compliant interface with the contacting tissue allows the second balloon152to conform to the uneven surface topography of the occluded vessel, resulting in an enhanced, more effective occlusion.

Anchoring and/or sufficiently occluding the targeted vessel with the second balloon152further allows positioning the first balloon150to abut against a tissue wall or region (such as the atrial wall) surrounding or otherwise extending from the ostium. The first balloon150may then be operated to exchange thermal, ablative energy between the balloon150and the proximate tissue. In particular, a cryogenic coolant or medium may be circulated through the first balloon150via the first inflation and exhaust lumens,154,165.

Of course, during the positioning and operation of the first and second balloons, the third balloon164surrounds the first and second balloons, thereby providing both a safety barrier in the event of a structural failure of either the first and second balloons, as well as a conformable interface pliably extending between the first and second balloons. The third balloon164thus further facilitate occlusion of the ostium, as well as contact with the surrounding tissue wall proximate the first balloon150. During operation, the interstitial region may be kept under vacuum to minimize any space between the third balloon164and the first and second balloons to reduce thermal isolation and thereby increase heat transfer, as well as providing for the removal of any fluid leaking into the interstitial region166.

Referring now toFIGS. 18 and 19, yet another configuration for an ablation element is shown wherein an ablation element includes an elastically deformable, thermally-transmissive tip element122secured to the distal portion of a catheter body124. When a load is applied to the tip element122it deforms. For example,FIG. 19illustrates the tip element subject to an axial load, such as is encountered when the tip is pressed against tissue. As shown, the distal portion of the tip element122presents a wider ablation surface when deflected as compared to the non deflected state. When the load is removed from the tip, it returns to the shape illustrated inFIG. 18. Fluid supply and exhaust lumens are provided as disclosed above. Also as described above, a pull wire125can be secured to the tip element122to help deform the element so that it doesn't need to be pressed hard against tissue. In an exemplary embodiment the tip element122is configured so that it is biased into the shape illustrated inFIG. 18. Proximal tension is applied to the pull wire125to deform or aid in deforming the tip element to an expanded configuration as shown inFIG. 19. When proximally directed tension is reduced on the pull wire125, the biasing force of the tip element causes it to return to the configuration shown inFIG. 18.

FIG. 20illustrates yet another configuration of an ablation element wherein a catheter body126has a distal end128covered with a mass of thermally conductive, highly elastic material, such as a cohesive gel130. When the distal end128and the gel130are pressed against tissue, the gel deforms to provide an enlarged distal end portion as shown by the dashed line132. Coolant exiting a coolant supply tube134cools the distal end128and the gel130.

Turning now toFIG. 21, an exemplary procedure is illustrated wherein an ablation element136in accordance with the invention has been delivered transeptally into the left atrium. In the illustration, the ablation element136is a balloon that is partially inflated with a nitrous oxide coolant so that it has a “squishy” or highly compliant character and dimensioned so that it can “blot” or contact an area of tissue approximately 28 to 30 mm in diameter. In the exemplary procedure, the balloon is inflated to the desired degree of firmness, or lack thereof, before being advanced toward tissue and the balloon's surface is chilled to a temperature in the range of minus 30 degrees Centigrade to minus 80 degrees Centigrade. The balloon is then placed into contact with tissue in the antrum138and the tissue is ablated. The balloon is moved to one or more additional areas of the antrum138until the desired tissue modification has been achieved. The balloon can be placed so as to create individual distinct lesions or overlapping lesions. In this fashion, large contiguous lesions can be created. The pattern139shown inFIG. 21illustrates an exemplary lesion periphery created with the ablation element136.

Because the doctor is not attempting to create a “ring,” the balloon does not have to be centered on the ostium140and no anchoring is needed. In general, for any of the disclosed cryoablation devices, precise alignment is not as important as with respect to other devices. This is significant, because the precise positioning within the antrum is difficult to achieve. The balloon does not enter the pulmonary vein142. However, depending upon placement of the balloon, the temperature achieved, and the duration that the balloon is left in place, is possible to ablate tissue in the ostium140in addition to tissue within the pulmonary vein142, as well as the antrum138.

In another exemplary method, the ablation catheter34as described above may be used to create a series of lesions in the heart, whereby the ablation catheter is maneuvered into the left atrium of the heart for treatment of an arrhythmia or other cardiac abnormality. Primarily, the ablation catheter may be positioned in proximity to the heart using one of either a subxyphoid approach, a thoracotomy approach, or a sternotomy method. Each of these methods provides surgical access to the heart for subsequent positioning and insertion into the left atrium of a medical device for ablation of the desired tissue.

Now referring toFIG. 22, employing a subxyphoid technique, the heart200may initially be accessed through a puncture technique using the same 17-Gauge Tuohy needle that is used to enter the epidural space when administering epidural anesthesia (typically .about. 100 mm overall length, and 1.5 mm O.D.). A subxyphoid incision202, which is typically less than 10 centimeters in length, is created. As the needle approaches the heart200under fluoroscopic guidance, small amounts of contrast media are injected to document penetration of the needle tip as it progresses towards the heart. Once properly positioned as indicated by the assistance of medical imaging, a guide wire may be passed through the needle. As a result, a standard introducer sheath, and subsequently an ablation catheter34, may be passed into a position in proximity to the heart200.

Now referring toFIGS. 23 and 24, a thoracotomy technique may also be performed for providing initial access the heart200, whereby one or more small thoracotomy incisions204are made in the chest wall between the ribs to permit access for thoracoscopic instruments and cameras, which provide dissection and visualization capabilities in the pericardial space for insertion and manipulation of medical instruments, including the ablation catheter. The small thoracotomy incisions are typically less than 10 centimeters in length. In this approach, the decompression of the pleural space may be necessary in order to achieve pericardial access.

As shown inFIG. 25, a third approach employs a sternotomy, which is commonly performed for open heart surgery, and is the least minimally-invasive of the approaches described above. A full sternotomy may include multiple incisions and the eventual division of the sternum, thereby providing direct access to the heart200.

Upon generally accessing the heart through any of the above-mentioned approaches, the ablation catheter must further enter the internal chambers of the heart for the eventual ablation of the desired tissue. Such internal access may be achieved by directing the ablation catheter through one of the pulmonary veins or the aorta, through the heart tissue or left atrial appendage, or through the superior vena cava and the septum wall.

To access the internal chambers of the heart through either of the pulmonary veins or the aorta, a pursestring suture may be placed in any of the pulmonary veins or the aorta. Using a seldinger technique, an introducer may be inserted through the pulmonary veins or aorta, and into the left atrium. Once the introducer is appropriately positioned, the ablation catheter may be guided through the introducer and into the left atrium for subsequent ablation of the desired tissue.

Access to the internal chambers of the heart may further be accomplished directly through an exterior surface of the heart, or through the left atrial appendage. For example, a pursestring suture may be placed in the left atrial appendage, through which an introducer and/or guidewire is positioned. As such, the ablation catheter may be guided directly into the left atrium through the left atrial appendage or other exterior heart surface for subsequent ablation of the desired tissue within the heart.

The internal chambers of the heart may additionally be accessed by a transseptal approach. A transseptal approach may include placing a pursestring suture in the lateral wall of the right atrium, providing access for a needle to further be inserted into the heart. The needle, as well as a guidewire and introducer, may be initially guided into the right atrium through the superior vena cava. Further, the needle may be maneuvered through the atrial septum and into the left atrium, at which point the guide wire may be inserted to dilate the opening in the atrial septum. Upon sufficient dilation of the septum, the introducer may be directed through the septum and into the left atrium. Subsequently, the ablation catheter may be guided through the introducer and into the left atrium for ablation of the desired tissue.

Upon accessing the internal chambers of the heart, and more particularly, the left atrium, the ablation catheter can be positioned in the orifice of the right inferior pulmonary vein, possibly employing the aid of fluoroscopy or other medical imaging to facilitate accurate placement of the device. Positioning and occlusion of the vein orifice may further be confirmed through the administration of a contrast dye. Once in the desired location, the ablation catheter can be used to create a lesion around the orifice of the right inferior pulmonary vein. The ablation catheter may then be repositioned in the right superior vein, the left superior vein, and the left inferior pulmonary vein for the creation of additional ablative lesions about the orifices of the respective vessels. An additional lesion may be created to connect the lesions of the left-sided pulmonary veins with the lesions of the right-sided pulmonary veins, to form somewhat of an “eyeglass” pattern.

Upon completion of the creation of the pulmonary vein lesions, one or more lesions, either spot lesions or linear in nature, extending from the left inferior pulmonary vein to the mitral valve annulus can be created using the ablation catheter. In order to confirm that the ablative lesions have in fact been successfully created, a pacing catheter or other electrical-sensing device can be used to monitor electrical pulses in the affected tissue, and ablation may be reinstituted in the desired locations, if necessary. Once the desired portions of the heart have been ablated, the introducer sheath and the ablation catheter can be removed, and the surgical openings may be appropriately closed.

While ablation procedures are typically performed on an arrested heart, the procedure described above may be performed with the ablation catheter on a beating heart employing a thoracoscopic or small thoracotomy approach, which reduces the recovery time for a patient as well as reducing the complexity of the surgical procedure. As such, the higher-risk portions of a typical maze procedure, namely a sternotomy, cardiopulmonary bypass, and/or aortic cross-clamping or cardiac arrest, are no longer necessary.

The ablation catheter used to create the lesions described above may include any of the features previously discussed. Moreover, in order to ease the use of the catheter in the transseptal approach, the length of a portion of the catheter may be reduced from that of a standard catheter inserted into the femoral artery or other insertion point distant from the heart. Furthermore, the flexibility of the portions of the catheter may be altered in order to provide increased malleability in order to facilitate the accurate positioning of the ablation element within the heart. Alternatively, pull-wires or other deflection mechanisms can be integrated with or otherwise coupled with the catheter for steering and/or positioning, as is known in the art.