Patent Application
20050288654
The present invention relates to ablation devices for medical therapies. In particular, the present invention relates to ablation instrument systems that use energy to ablate internal bodily tissues, and methods for using such systems for the treatment of diseases. Even more particularly, the systems and methods of the present invention can be used, for example, in the treatment of cardiac conditions such as cardiac arrhythmias.
Cardiac arrhythmias, e.g., fibrillation, are irregularities in the normal beating pattern of the heart and can originate in either the atria or the ventricles. For example, atrial fibrillation is a form of arrhythmia characterized by rapid randomized contractions of the atrial myocardium, causing an irregular, often rapid ventricular rate. The regular pumping function of the atria is replaced by a disorganized, ineffective quivering as a result of chaotic conduction of electrical signals through the upper chambers of the heart. Atrial fibrillation is often associated with other forms of cardiovascular disease, including congestive heart failure, rheumatic heart disease, coronary artery disease, left ventricular hypertrophy, cardiomyopathy or hypertension.
Atrial arrhythmia may be treated using several methods. Pharmacological treatment of atrial fibrillation, for example, is initially the preferred approach, first to maintain normal sinus rhythm, or secondly to decrease the ventricular response rate. Other forms of treatment include drug therapies, electrical cardioversion, and RF catheter ablation of selected areas determined by mapping. In the more recent past, other surgical procedures have been developed for atrial fibrillation, including left atrial isolation, transvenous catheter or cryosurgical ablation of His bundle, and the Corridor procedure, which have effectively eliminated irregular ventricular rhythm. However, these procedures have for the most part failed to restore normal cardiac hemodynamics, or alleviate the patient's vulnerability to thromboembolism because the atria are allowed to continue to fibrillate. More effective surgical treatment was thus required to cure medically refractory atrial fibrillation of the heart.
Accordingly, more effective surgical techniques have been proposed to treat medically refractory atrial fibrillation of the heart. Although these procedures were originally performed with a scalpel, these techniques may also use ablation (also referred to as coagulation). One such technique is strategic ablation of the atrial tissues through ablation catheters that treat the tissue, generally with heat or cold, to cause tissue necrosis (i.e., cell destruction). The destroyed muscle cells are replaced with scar tissue which cannot conduct normal electrical activity within the heart.
For example, the pulmonary vein has been identified as one of the origins of errant electrical signals responsible for triggering atrial fibrillation. In one known approach, circumferential ablation of tissue within the pulmonary veins or at the ostia of such veins has been practiced to treat atrial fibrillation. Similarly, ablation of the region surrounding the pulmonary veins as a group has also been proposed. By ablating the heart tissue (typically in the form linear or curved lesions) at selected locations, electrical conductivity from one segment to another can be blocked and the resulting segments become too small to sustain the fibrillatory process on their own. Ablation procedures are often performed during coronary artery bypass and mitral valve replacement operations because of a heightened risk of arrhythmias in such patients and the opportunity that such surgery presents for direct access to the heart.
Several types of ablation devices have recently been proposed for creating lesions to treat cardiac arrhythmias, including devices which employ electrical current (e.g., radio-frequency “RF”) heating or cryogenic cooling. Such ablation devices have been proposed to create elongated lesions that extend through a sufficient thickness of the myocardium to block electrical conduction.
These devices, however, are not without their drawbacks. When cardiac surgery is performed “on pump,” the amount of time necessary to form a lesion becomes a critical factor. Because these devices rely upon resistive and conductive heating (or cooling), they must be placed in direct contact with the heart and such contact must be maintained for a considerable period of time to form a lesion that extends through the entire thickness of the heart muscle. The total length of time to form the necessary lesions can be excessive. This is particularly problematic for procedures that are performed upon a “beating heart” patient. In such cases the heart itself continues to beat and, hence, is filled with blood, thus providing a heat sink (or reservoir) that works against conductive and/or resistive ablation devices. As “beating heart” procedures become more commonplace (in order to avoid the problems associated with arresting a patient's heart and placing the patient on a pump), the need for better ablation devices will continue to grow.
Moreover, devices that rely upon resistive or conductive heat transfer can be prone to serious post-operative complications. In order to quickly perform an ablation with such “contact” devices, a significant amount of energy must be applied directly to the target tissue site. In order to achieve transmural penetration, the surface that is contacted will experience a greater degree of heating (or freezing). For example, in RF heating of the heart wall, a transmural lesion requires that the tissue temperature be raised to about 50° C. throughout the thickness of the wall. To achieve this, the contact surface will typically be raised to at least 80° C. Charring of the surface of the heart tissue can lead to the creation of blood clots on the surface which can lead to post-operative complications, including stroke. Even if structural damage is avoided, the extent of the lesion (i.e., the width of the ablated zone) on the surface that has been contacted will typically be greater than necessary.
Ablation devices that do not require direct contact have also been proposed, including acoustic and radiant energy. Acoustic energy (e.g., ultrasound) is poorly transmitted into tissue (unless a coupling fluid is interposed). Laser energy has also been proposed but only in the context of devices that focus light into spots or other patterns. When the light energy is delivered in the form of a focused spot, the process is inherently time consuming because of the need to expose numerous spots to form a continuous linear or curved lesion.
In addition, existing instruments for cardiac ablation also suffer from a variety of design limitations. The shape of the heart muscle adds to the difficulty in accessing cardiac structures, such as the pulmonary veins which are located on the posterior surface of the heart. Further, the presence of epicardial fat limits the depth of ablative penetration for many ablative energy sources.
Accordingly, there exists a need for better surgical ablation instruments that can form lesions with minimal overheating and/or damage to collateral tissue. Moreover, instruments that are capable of creating lesions uniformly, rapidly and efficiently would satisfy a significant need in the art.
The present invention provides surgical ablation instrument systems for creating lesions in tissue, especially cardiac tissue for treatment of arrhythmias and other cardiac conditions. The hand held instruments are especially useful in open chest or port access cardiac surgery for rapid and efficient creation of curvilinear lesions to serve as conduction blocks. The instruments can be applied to form either endocardial or epicardial ablations, and are designed to create lesions in the atrial tissue in order to electrically decouple tissue segments on opposite sides of the lesion.
In one aspect of the invention, surgical ablation instruments are disclosed that are well adapted for use in or around the intricate structures of the heart. In one embodiment, the distal end of the instrument can have a malleable shape so as to conform to the surgical space in which the instrument is used. The instruments can include at least one malleable strip element disposed within the distal end of the instrument body or housing so that the distal end can be conformed into a desired shape. In addition, the instruments can also include a clasp to form a closed loop after encircling a target site, such as the pulmonary veins. Such instruments can be used not only with penetrating energy devices but also with other ablation means, such as RF heating, cryogenic cooling, ultrasound, microwave, ablative fluid injection and the like. In still another embodiment, the distal end of the instrument can include a translatory mechanism for disposing the tip of the instrument in a variety of configurations.
In one embodiment, the surgical ablation instrument includes a housing or flexible elongate member having a proximal end, a distal end and a longitudinal lumen extending therebetween. An energy emitting element having a proximal end and a distal end can be slidably disposed within the lumen for transmitting energy to the distal end of the elongate member. The housing can comprise a plurality of interconnected links, or can include cutout portions such as grooves on its outer surface to facilitate flexion. The housing can also be formed from a flexible strip or flexible bellows.
In another aspect of the invention, the housing can include a profile that provides for longitudinal flexibility as well as torsional strength. In one embodiment, the housing includes a shaped inner lumen for containing a complementarily shaped light delivering element. The specific geometries of the lumen and element are such that twisting or rotation of the light delivering element within the inner lumen is prevented, and the orientation of the light delivering element with respect to the housing is ensured. In another embodiment, the housing can include reinforcement such as shape memory wire or polymeric supports to prevent the housing from twisting when positioned on tortuous anatomical surfaces.
In one aspect of the invention, hand-held and percutaneous instruments are disclosed that can achieve rapid and effective photoablation through the use of penetrating radiation, especially distributed radiant energy. It has been discovered that radiant energy, e.g., diffuse infrared radiation, can create lesions in less time and with less risk of the adverse types of tissue destruction commonly associated with prior art approaches. Unlike instruments that rely on thermal conduction or resistive heating, controlled penetrating radiant energy can be used to simultaneously deposit energy throughout the full thickness of a target tissue, such as a heart wall, even when the heart is filled with blood. Distributed radiant energy can also produce better defined and more uniform lesions.
It has also been discovered that infrared radiation is particularly useful in forming photoablative lesions. In one preferred embodiment the instruments emit radiation at a wavelength in a range from about 800 nm to about 1000 nm, and preferably emit at a wavelength in a range of about 915 nm to about 980 nm. Radiation at a wavelength of 915 nm or 980 nm is commonly preferred, in some applications, because of the optimal absorption of infrared radiation by cardiac tissue at these wavelengths. In the case of ablative radiation that is directed towards the epicardial surface, light at a wavelength about 915 nm can be particularly preferably.
In another aspect of the invention, surgical ablation instruments are disclosed that are well adapted for use in or around the intricate structures of the heart. In one embodiment, the distal end of the instrument can have a malleable shape so as to conform to the surgical space in which the instrument is used. Optionally, the distal end of the instrument can be shaped into a curve having a radius between about 5 millimeters and about 25 millimeters. The instruments can include at least one malleable strip element disposed within the distal end of the instrument body or housing so that the distal end can be conformed into a desired shape. In addition, the instruments can also include a clasp to form a closed loop after encircling a target site, such as the pulmonary veins.
In yet another aspect of the invention, surgical ablation instruments are disclosed having a housing with at least one lumen therein and having a distal portion that is at least partially transmissive to photoablative radiation. The instruments further include a light delivery element within the lumen of the housing that is adapted to receive radiation from a source and deliver radiant energy through a transmissive region of the housing to a target tissue site. The radiant energy is delivered without the need for contact between the light emitting element and the target tissue because the instruments of the present invention do not rely upon conductive or resistive heating.
In other aspects of the invention, ablation instruments are provided having a sufficient length to create a full encircling path around the pulmonary veins. The instruments can be configured to emit varying amounts of ablative energy along its length. In one embodiment, the ablation device includes an energy emitting element that comprises a plurality of segments, each segment having a different diameter than an adjacent segment to collectively form an elongate energy emitting element having variable diameters along its length. The energy emitting element can also be provided with a tapered profile along its length, in order to vary the amount of ablative energy emitted. The instrument can be used to provide an ablative path around both pairs of pulmonary veins, or an individual pair of pulmonary veins.
In another embodiment, the instrument can include an inflatable elongate balloon that resides within the housing along with the light delivering element. An inflation controller in communication with the balloon and an inflation source, e.g., an air, gas or fluid pump, can be provided to enable the selective inflation of the balloon. Upon inflation, the balloon urges against the light delivering element and effects the angular orientation of the element with respect to the longitudinal axis of the housing. This allows the surgeon to change the angle of the light delivering element by controlling the inflation of the balloon, and consequently the energy emitting pathway along the length of the light delivering element.
In yet another embodiment, the instrument can include a plurality of light delivering elements of varying lengths, each element being configured to emit a dose of ablative energy at a specific position with respect to the length of the housing. Each of the light delivering elements can have a different length than the other elements. A selection mechanism can be provided with the ablation instrument so that the surgeon can select any one of the plurality of light delivering elements for activation. Preferably, each of the light delivering elements includes a diffuser tip at a distal end. The instrument can include a housing that has a portion transparent to emitted energy.
The light delivering element can be a light transmitting optical fiber adapted to receive ablative radiation from a radiation source and a light emitting tip at a distal end of the fiber for emitting diffuse or defocused radiation. The light delivering element can be slidably disposed within the inner lumen of the housing and the instrument can further include a translatory mechanism for disposing the tip of the light delivering element at one or more of a plurality of locations with the housing. Optionally, a lubricating fluid can be disposable between the light delivery element and the housing. This fluid can be a physiologically compatible fluid, such as saline, and the fluid can also be used for cooling the light emitting element or for irrigation via one or more exit ports in the housing.
In one embodiment of the invention, the ablation device comprises a housing having a proximal end, a distal end and a longitudinal lumen extending therebetween. An ablation element is disposed within the lumen of the housing to ablate tissue at a target site. Also included is an irrigation cap at the distal end of the ablation element. A fluid source connected to the housing provides fluid to the ablation element during delivery of the ablation energy. The fluid can be introduced via a fluid inlet on the irrigation cap to be delivered between the ablation element and the irrigation cap. A cutout portion formed within the irrigation cap forms a fluid carrying cavity for delivering the fluid to the ablation element. In one particular aspect, the irrigation cap is formed as a pair of jaws, with the free ends of the jaws having surface features such as teeth, grooves, etc. for enhanced gripping. The fluid can comprise a material which cools the ablation element during delivery of ablative energy, and can include lubricating fluids, and/or physiologically compatible fluids such as saline.
The light emitting tip can include a hollow tube having a proximal end joined to the light transmitting optical fiber, a closed distal end, and an inner space defining a chamber therebetween. The light scattering medium disposed within the chamber can be a polymeric or liquid material having light scattering particles, such as alumina, silica, or titania compounds or mixtures thereof, incorporated therein. The distal end of the tube can include a reflective end and, optionally, the scattering medium and the reflective end can interact to provide a substantially uniform axial distribution of radiation over the length of the housing.
Alternatively, the light emitting tip can include at least one reflector for directing the radiation through the transmissive region of the housing toward a target site and, optionally can further include a plurality of reflectors and/or at least one defocusing lens for distributing the radiation in an elongated pattern.
The light emitting tip can further include at least one longitudinal reflector or similar optical element such that the radiation distributed by the tip is confined to a desired angular distribution. In one embodiment, the reflector is configured to selectively block a portion of the energy emitting element from emitting ablative energy. The reflector can be configured to seat around the energy emitting element, and can include a window or cutout portion for emitting energy. The window can be adjustably positioned along the length of the reflector. Alternatively, or in addition, the size of the window can also be adjustable.
The hand held instruments can include a handle incorporated into the housing. An inner lumen can extend through the handle to received the light delivering element. The distal end of the instrument can be resiliently deformable or malleable to allow the shape of the ablation element to be adjusted based on the intended use.
In one embodiment, a hand held cardiac ablation instrument is provided having a housing with a curved shape and at least one lumen therein. A light delivering element is disposable within the lumen of the housing for delivering ablative radiation to form a curved lesion at a target tissue site adjacent to the housing.
In another aspect of the invention, the light delivering element can be slidably disposed within the inner lumen of the housing, and can include a light transmitting optical fiber adapted to receive ablative radiation from a radiation source and a light diffusing tip at a distal end of the fiber for emitting radiation. The instrument can optionally include a handle joined to the housing and having an inner lumen though which the light delivering element can pass from the radiation source to the housing.
In yet another aspect of the present invention, the light diffusing tip can include a tube having a proximal end mated to the light transmitting optical fiber, a closed distal end, and an inner chamber defined therebetween. A light scattering medium is disposed within the inner chamber of the tube. The distal end of the tube can include a reflective end surface, such as a mirror or gold coated surface. The tube can also include a curved, longitudinally-extending, reflector that directs the radiant energy towards the target ablation site. The reflective surfaces and the light scattering medium interact to provide a substantially uniform axial distribution of radiation of the length of the housing.
In other aspects of the present invention, a hand held cardiac ablation instrument is provided having a slidably disposed light transmitting optical fiber, a housing in the shape of an open loop and having a first end adapted to receive the slidably disposed light transmitting optical fiber, and at least one diffuser chamber coupled to the fiber and disposed within the housing. The diffuser chamber can include a light scattering medium disposed within the housing and coupled to the slidably disposed light transmitting optical fiber.
In yet another aspect, a percutaneous cardiac ablation instrument in the form of a balloon catheter with an ablative light projecting assembly is provided. The balloon catheter instrument can include at least one expandable membrane disposed about a housing. This membrane is generally or substantially sealed and serves as a balloon to position the device within a lumen. The balloon structure, when filled with fluid, expands and is engaged in contact with the tissue. The expanded balloon thus defines a staging from which to project ablative radiation in accordance with the invention. The instrument can also include an irrigation mechanism for delivery of fluid at the treatment site. In one embodiment, irrigation is provided by a sheath, partially disposed about the occluding inner balloon, and provides irrigation at a treatment site (e.g. so that blood can be cleared from an ablation site). The entire structure can be deflated by applying a vacuum which removes the fluid from the inner balloon. Once fully deflated, the housing can be easily removed from the body lumen.
The present invention also provides methods for ablating tissue. One method of ablating tissue comprises positioning a distal end of a penetrating energy instrument in proximity to a target region of tissue, the instrument including a source of penetrating energy disposed within the distal end. The distal end of the instrument can be curved to permit the distribution of penetrating energy in elongated and/or arcuate patterns. The method further including activating the energy element to transmit penetrating energy to expose the target region and induce a lesion; and, optionally, repeating the steps of positioning and exposing until a composite lesion of a desired shape is formed.
In another method, a device is provided having a light delivering element coupled to a source of photoablative radiation and configured in a curved shape to emit an arcuate pattern of radiation. The device is positioned in proximity to a target region of cardiac tissue, and applied to induce a curvilinear lesion. The device is then moved to the second position and reapplied to induce a second curvilinear lesion. The steps of positioning and reapplying can be repeated until the lesions are joined together to create a composite lesion (e.g., a closed loop encircling one or more cardiac structures).
In another embodiment, methods of ablating cardiac tissue are provided. A device is provided having a housing in the shape of a hollow ring or partial ring having at least one lumen therein and at least one open end, and a light delivering element slidably disposed within the lumen of the housing for delivering ablative radiation to form a circular lesion at a target region adjacent the housing. The methods includes the steps of positioning the device in proximity to the target region of cardiac tissue, applying the device to the target region to induce a curvilinear lesion, advancing the light delivering element to a second position, reapplying the device to the target region to induce a second curvilinear lesion, and repeating the steps of advancing and applying until the lesions are joined together to create a composite circumferential lesion.
The invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which like reference numerals designate like parts throughout the figures, and wherein:
The present invention provides hand held surgical ablation instruments that are useful for treating patients with cardiac conditions such as, for example, atrial arrhythmia. Turning now to the drawings and particularly to
The handle 12 of the ablation instrument 10 is effective for manually placing the ablation element 20 proximate to a target tissue site. While the handle 12 can have a variety of shapes and sizes, preferably the handle 12 is generally elongate with at least one inner lumen extending therethrough. The proximal end 14 of the handle 12 can be adapted for coupling with a source of radiant energy 50, and the distal end of the handle 16 is mated to or formed integrally with the ablation element 20. In a preferred embodiment, the handle 12 is positioned substantially coaxial with the center of the ablation element 20. The handle 14 can optionally include an on-off switch 18 for activating the laser energy source 50.
As shown in more detail in
The light delivering element 32 can be slidably disposed within the outer housing 22 to allow the light diffusing tip 36 to be positioned with respect to the target ablation site. A lever 52 or similar translatory mechanism can be provided for slidably moving the light delivering element 32 with respect to the handle 12. As shown in
The outer housing 22 can optionally include a connecting element for forming a closed-loop circumferential ablation element 20. By non-limiting example,
Another embodiment of the surgical ablation instrument 10A is shown in
The outer housing 22A can be preshaped to function as a guide device to guide the light delivering element 32A along the ablation path. The cooperation between the light delivering element 32A and the inner lumen, as the element 32A is advanced through the inner lumen, positions the ablative element in a proper orientation to facilitate ablation of the targeted tissue during the advancement. Thus, once the outer housing 22A is stationed relative to the targeted tissue site, the light delivering element 32A can be easily advanced along the ablation path to generate the desired tissue ablations.
As shown in
The inner lumen of the outer housing 22, 22A in
As shown in
In
With reference again to
The light diffusing tip 36 extends distally from the optical fiber 34 and is formed from a transmissive tube 38 having a light scattering medium 40 disposed therein. For additional details on construction of light diffusing elements, see, for example, U.S. Pat. No. 5,908,415 issued Jun. 1, 1999.
The scattering medium 40 disposed within the light diffusing tip 36 can be formed from a variety of materials, and preferably includes light scattering particles. The refractive index of the scattering medium 40 is preferably greater than the refractive index of the housing 22. In use, light propagating through the optical fiber 34 is transmitted through the light diffusing tip 36 into the scattering medium 40. The light is scattered in a cylindrical pattern along the length of the light diffusing tip 36 and, each time the light encounters a scattering particle, it is deflected. At some point, the net deflection exceeds the critical angle for internal reflection at the interface between the housing 22 and the scattering medium 40, and the light exits the housing 22 to ablate the tissue.
Preferred scattering medium 40 includes polymeric material, such as silicone, epoxy, or other suitable liquids. The light scattering particles can be formed from, for example, alumina, silica, or titania compounds, or mixtures thereof. Preferably, the light diffusing tip 36 is completely filled with the scattering medium 40 to avoid entrapment of air bubbles.
As shown in more detail in
In one use, the hand held ablation instrument 10 is coupled to a source of penetrating energy 50 and can be positioned within a patient's body either endocardially or epicardially to ablate cardiac tissue. When the penetrating energy is light, the source is activated to transmit light through the optical fiber 34 to the light diffusing tip 36, wherein the light is scattered in a circular pattern along the length of the tip 36. The tube 38 and the reflective end 42 interact to provide a substantially uniform distribution of light throughout the tip 36. When a mirrored end cap 42 is employed, light propagating through the light diffusing tip 36 will be at least partially scattered before it reaches the mirror 42. When the light reaches the mirror 42, it is then reflected by the mirror 42 and returned through the tip 36. During the second pass, the remaining radiation encounters the scattering medium 40 which provides further diffusion of the light.
When a reflective coating or longitudinally disposed reflector 44 is used, as illustrated in
In another embodiment as illustrated in
In another aspect of the present invention, an irrigation cap 100 can be placed over the diffusing tip 36, as illustrated in
In yet another embodiment of the invention, illustrated in
In still yet another embodiment of the invention, the outer housing 122A can comprise a plurality of linked units 120, as shown in
In another aspect of the invention, the ablation element, including the housing and inner lumen, can be configured with a special geometry to align the light delivering element and the outer housing. As illustrated in
The housing can be made from a variety of materials including polymeric, electrically nonconductive material, like polyethylene (PET), polytetrafluoroethylene (PTFE), FEP, PFA, urethane, polyurethane, or PVC, which can withstand tissue coagulation temperatures without melting and provides a high degree of laser light transmission. Preferably, the housing is made of Teflon® tubes and/or coatings. The use of Teflon® improves the procedures by avoiding the problem of fusion or contact-adhesion between the ablation element and the cardiac tissue during usage. While the use of Teflon® avoids the problem of fusion or contact-adhesion, the hand held cardiac ablation instrument does not require direct contact with the tissue to effect a therapeutic or prophylactic treatment. Preferably, the housing incorporates opaque or semi-opaque materials such as ePTFE, and/or includes optically transparent windows that provide for light transmission.
The housing is designed with longitudinal flexibility to ensure adequate conformance to various tissue topographies. For example, as shown in
To provide the housing with longitudinal flexibility as well as anti-twist or torsionally stiff properties, materials such as PTFE, PFA, FEP, urethane, or PVC can be used. Other similar materials can also be used which have flexural modulus properties, profile, reinforcement, or filler materials that resist twisting along the longitudinal axis. By combining various structural elements and material properties, the housing can resist twist and remain straight in two planes. In addition, by providing an element that is shaped in three dimensions inside the housing, it is possible to provide adequate positioning and flexure within difficult anatomical locations. For instance, the shaped element could include stainless steel, Nitinol (NiTi) or polymer round or flat wire pre-shaped to a desired shape or geometry. This shaped element could also include a malleable stainless steel or polymer structure that is manipulated by the surgeon to provide the desired positioning, as previously described in the embodiment of
In still a further embodiment, the housing can include a channel or lumen that, once positioned proximate to the target tissue, can be filled with a setting agent such as epoxy, UV cured adhesive, thermosetting polymer, or other material that can be inserted in liquid or gel form into the channel or lumen that, when cured, provides a rigid structure to the housing. This rigid structure then provides proper shape and position to the housing during the procedure. Alternatively, a thermoplastic metal, polymer or liquid that hardens and softens at specific temperatures can be applied to provide for a rigid structure. Following the ablation process, the filling material can be dissolved, melted, broken down, or otherwise removed to return the housing to its original flexible form for removal.
Further, the housing of the present invention can include a profile that provides for longitudinal flexibility and proper orientation with respect to the target tissue to be ablated. As illustrated,
In another embodiment of the present invention, rather than rely on the profile geometry for alignment of the light delivering element with the housing, reflective elements can be implemented which would eliminate the need for such specific geometries. As shown in
Although illustrated in the context of light delivering surgical instruments, the malleable structures disclosed herein are equally adaptable for use with other sources of ablative energy, such as such as RF heating, cryogenic cooling, ultrasound, microwave, ablative fluid injection and the like. RF Heating devices, for example, are described in U.S. Pat. No. 5,690,611 issued to Swartz et al. and herein incorporated by reference. Cryogenic devices are similarly described, for example, in U.S. Pat. No. 6,161,543 issued to Cox et al. and herein incorporated by reference.
Epicardial ablation is typically performed during a by-pass procedure, which involves opening the patient's chest cavity to access the heart. The heart can be arrested and placed on a by-pass machine, or the procedure can be performed on a beating heart. The hand held ablation instrument 10 is placed around one or more pulmonary veins, and is preferably placed around all four pulmonary veins. The connecting element 30 can then be attached to the distal end 16 of the handle 12 or the proximal, trailing end 24 of the outer housing 22 to close the open loop. The handle 12 can optionally be pulled to tighten the ablation element 20 around the pulmonary veins. The energy delivering element 32 is then moved to a first position, as shown in
In another aspect of the invention, the instruments of the present invention are particularly useful in forming lesions around the pulmonary veins by directing radiant energy towards the epicardial surface of the heart and the loop configuration of distal end portion of the instruments facilitates such use. It has been known for some time that pulmonary veins can be the source of errant electrical signals and various clinicians have proposed forming conduction blocks by encircling one or more of the pulmonary veins with lesions. As shown in
Endocardial applications, on the other hand, are typically performed during a valve replacement procedure which involves opening the chest to expose the heart muscle. The valve is first removed, and then the hand held cardiac ablation instrument 10 according to the present invention is positioned inside the heart as shown in
In another aspect of the invention, the ablation element 20 can be configured to have a sufficient length to create the full encircling path without advancing the light delivering element 32 through the outer housing 22. For instance, the ablation instrument 10 can include a long (20 cm) active length that can emit at the same energy level (W/length) as that delivered by the shorter (5 cm) instrument, or can emit at a lower level. To provide effective ablative therapy, an adequate quantity of Joules per volume of tissue should be delivered. The rate of delivery, however, can be adjusted depending upon the capabilities of the materials and components of the ablation instrument 10. Thus, the length of the ablative element 20 and consequently, the time required to complete the ablative therapy, can be varied without affecting the integrity of the overall ablation process.
Accordingly, it is possible to provide a light delivering element 32 that can emit varying amounts of ablative energy along its length.
In another embodiment of the ablation element 220′ shown in
In yet another embodiment shown in
Another way to change the level of ablative energy being delivered by the ablation element is to selectively block or cover areas along the length of the light delivering element. For example, as illustrated in
Whether the ablation instrument 10 requires advancement or is completely encircling, there is a potential need to provide overlap of the ablation at either end of the outer housing 22. A clamp or clip mechanism 154, as shown in
As discussed above, correct positioning of the housing 22 with respect to the patient's anatomy is critical to the efficacy of the lesion created. Specifically, the position of the housing 22 with respect to the left atrial appendage (LAA) is important to ensure that the lesion correctly isolates the pulmonary veins. The correct position of the housing 22 in such a procedure should be posterior to the LAA or between the LAA and the pulmonary vein. Through specific surgical approaches such as thoracotomy, thorascopy, sternotomy, sub xyphoid, or other undetermined surgical or scoped approaches, delivery and positioning of the housing 22 may require additional verification of position with respect to the LAA. Accordingly, the ablation instruments 10 of the present invention can incorporate radiopaque or echogenic ultrasound visible coatings or components. In addition, the application of radiopaque markers/dyes to the blood volume with techniques such as transesophageal echocardiograms (TEE) or fluoroscopy can provide further confirmation of the position of the housing 22. In more invasive procedures, a thorascope can be used to obtain visual confirmation from the left chest. Other less invasive methods include the use of impedance measurements between electrodes and the housing, or shaped introducing guides 156 that provide for preferential positioning of the housing, as shown in
In still yet another embodiment, the present invention provides an ablation instrument 300 that can incorporate many of the advantages and features of the previous embodiments described above. As illustrated in
As shown, a cable 302 extends from the ablation element 350 and handle portion 310 to an attachment device such as a cable connector 304 which is adapted to be received by an energy source such as a laser source. Also extending from the cable 302 is an irrigation line 306 which allows the instrument 300 to receive irrigation fluid. The irrigation line 306 can include an attachment device, such as a male luer lock 306, for attachment to an irrigation fluid source.
The sheath 330 of the ablation element 350 can have a variety of configurations, and the sheath 330 may be preshaped or flaccid. In an exemplary embodiment, the sheath 330 is adapted to function as a guide device to direct the ablation element 350 along the treatment path, and more preferably it can be adapted to cooperate with the ablation element to position the ablation element in a proper orientation to facilitate ablation of the targeted tissue during the advancement. Thus, once the ablation sheath 330 is stationed relative to the targeted contact surface, the ablation element 350 can be easily advanced along the ablation path to generate the desired tissue treatment. The sheath 330 can also serve as an energy shield to protect tissues not targeted for treatment.
The sheath 330 may be made of a variety of materials, but one exemplary material is ePTFE. The porosity, density, pore size and other physical characteristics of the material should be selected so as to improve the performance of the sheath. These characteristics should be carefully chosen to give the best combination of longitudinal flexibility, tissue conformability, torsional resistance, lubricity, atrauma and shielding. Preferably, the sheath 330 is made from a polymeric material, like polyethylene, PTFE, PTFA, FEP or polyurethane, which can withstand tissue coagulation temperatures without melting and to provide a high degree of laser light transmission. Alternative designs of the sheath may incorporate opaque or semi-opaque materials such as ePTFE that incorporate optically transparent “windows,” such as window 336, providing for light transmission. The spine element 334 is preferably formed by extrusion in PEBAX polymer.
The sheath is preferably designed with longitudinal flexibility to insure adequate contact with cardiac tissue, but it can also have torsional stiffness characteristics to resist twisting. Resistance to twisting insures that the ablative energy is directed only toward the desired tissues so to maximize ablative effectiveness and to minimize collateral damage. Alternative designs may rely upon uniquely shaped profiles and torsional flexibility to allow conformance to the variant tissue topographies. Much of the sheath is not visible to the surgeon during use because the left atrium is located on the posterior surface of the heart and there is additionally other anatomy such as the pericardium and great vessels in close proximity. Without preferred visualization of the sheath it is therefore important that the sheath ensure both adequate contact and rotational alignment with the target tissue.
Another feature of the sheath 330 is its anti-twisting properties, which relate to the ability to correctly orientate a device that is required to be rotationally directed towards a target while traveling through a flexible linear path with a window capable of being translucent to the specific energy. The mechanism of the invention is to create loosely interlocking geometries that interact to prevent rotational displacement. These components are then utilized to fix a therapeutic device within one or both of these components such that directional orientation is assured. As shown in
Preferred embodiments of the disclosed invention including anti-twist or torsionally stiff properties include profiles of PTFE, PFA, FEP, Urethane, PVC or other similar materials that by properties such as flexural modulus, profile, reinforcement, or filler materials result in a sheath that resists twist along the longitudinal axis. By combining various structural elements and material properties it is further possible to provide for a device that resist twist and remains straight in two planes or is preferentially shaped in three dimensions. By providing a three dimensionally shaped element within the sheath it is possible to provide adequate positioning within even the most variant anatomy.
Yet a further embodiment of the current disclosure would include a channel or lumen within the sheath that once in position would be filled with a material such as epoxy, UV cured adhesive, thermosetting polymer or other material that can be inserted in liquid or gel form into such lumen or channel and when cured provides a rigid structure to the sheath. This rigid structure then provides proper shape and position to the sheath during the procedure. Alternately the material could be a thermoplastic metal, polymer, or liquid that hardens and softens at appropriate temperature and provides for similar structure. Following the therapy process the filling material would be dissolved, melted, broken, or otherwise affected to destroy the previous rigid structure and return the sheath to a flexible form for removal.
In another exemplary embodiment, the sheath 330 can be extruded with a shielding material, such as a dye or particulate to focus the energy toward the window 336. For example, by utilizing metallic particulates as a loading agent in the material it would be possible to adequately shield an RF or ultrasound antennae to create a directional emission of energy.
Anti-twist designs may further include preferable profiles of the sheath that rely upon the shape of the profile rather than torsional rigidity to provide correct alignment with the target tissue. Such preferred profiles would include “D” shapes, half moons, open “C” channels, triangular channels, or other similar and varied designs that interact to align the light delivering element with the tissue. The preferred embodiment of the current disclosure is a “D” shape whereby the flat segment of the “D” provides such accurate alignment with the tissue when coupled with a sheath material that is torsionally flaccid. The crown of the “D” further provides for visual or tactile verification of alignment.
The previously described embodiments providing for anti-twist or alignment of the sheath could incorporate reflective elements that would eliminate need for the above described “special geometry” that operates to align the light emission device. By providing reflective elements on the guide sheath it would therefore be possible to eliminate the directional orientation device on the ablative device. The reflective element(s) could also be provided on the spine 334′, as shown in
Such reflective elements could include but are not limited to metallic foils, polymers with highly reflective surfaces, vapor or chemically deposited surfaces or other technologies that result in a reflective or mirror like surface. The advantage of this system over the prior art is that the energy emissive element is not required to be shaped to match the channel. Rather, the positioning component can be shaped appropriately and the energy emission element can then be fixed to this component, or it can be slide and/or rotate freely within this component. By attaching the reflector 352 to the positioning component, e.g., the spine 334 or the sheath 330, rotation of the energy transmitter is irrelevant to the energy emission direction. This is beneficial in that the emitter does not require a shaped output, rather the alignment feature directs this output.
The second advantage of this invention is the novel use of FEP and ePTFE to create an insulating and transmissive guide channel. This is advantageous over prior art in that the addition of FEP creates an optically clear window 336. In an exemplary embodiment, the sheath 330 includes a hemi-cylindrical portion formed from ePTFE, and a planar bottom surface formed from FEP that are bonded together using heat and pressure to form the D-shaped sheath 330. Further, it is notable that this same technology could be utilized for endoscopic evaluation of anatomical structures whereby a endoscopic evaluation device may be passed down the length of the channel and visually inspect the tissues in contact with the guide channel. This may be of great advantage when tissues in opaque or visually impeding fluids typically surround the structure to be treated. The ability to particular or pigment load (using multicolored extrusion lines) the alignment spine 334 in order to create either electromagnetic shielding and/or optical shielding for controlling the emissive aperture is also an additional feature of the present invention. Also, the present invention provides the ability to create an optical lens on the spine 334 to create a focused energy emission. Specifically, by bulking up or shaping the segments of the tubing, it would be possible to create a focusing or diverging lens to create the appropriate emission.
Thirdly, the creation of a T-shaped shrink tube provides the ability to appropriately pass coolant throughout the length of the channel as well as providing proper orientation. In addition, the sheath 330 bears graphical markings and numberings to aid the surgeon in orienting and positioning the device on cardiac tissue. The markings and their blue color were specifically designed to enhance visibility and recognition under operating room lighting conditions. Further, a transmurality sensor or other lesion effectiveness/assessment sensor may also be integrated into or attached to the sheath.
Turning now to another component of the ablation instrument 300,
The guide component design is optimized to provide minimal trauma and resistance during surgical placement while providing maximum visibility under OR lighting and maximal grip by forceps and other surgical instruments. Its dimensions, geometry and material are specifically chosen for this purpose. Its design includes both an external flat for easy visual and tactile orientation during use, and an internal channel designed to provide an optimal feel to the surgeon. The guide is an injection molded component, made of a TPE. It includes an integral connector which allows it to be bonded to the distal end of the sheath with a UV adhesive. Its surgical “feel” is enhanced by its closed end, hollow cylindrical design. This internal feature is created through use of a wire placed in the mold prior to injection and removed after part molding is complete. The tip of the cylinder is closed by an RF heat forming process. Although the external cross section of the guide is essentially round, it does include a flat on its bottom side. This flat serves to improve the feel that the surgeon perceives when grasping the guide with surgical instruments. The exterior surface of the guide bears a no slip matt finish, rather than a polished finish, to improve the surgeons ability to easily grip the part with his instruments.
The integral connector is designed to also function as an atraumatic means of transition from the small cross section guide to the larger cross section sheath. This feature is important since the device also dilates and separates the sometimes fragile cardiac tissues during surgical placement.
The device's extension 340 is specifically designed as a flexible, rather than rigid component. This approach makes the instrument 300 both more ergonomic for the surgeon and less obtrusive in the crowded surgical field. It is formed of an extrudable polymer and contains helically wound stainless steel wire to prevent kinking when flexed. This component serves two functions. It provides room for the 7 cm movement of the therapeutic fiber 350 as it is indexed forward and backward. It also provides physical separation between the light delivering sheath 330 and the handle 310. This separation makes the instrument 300 more easily and conveniently used in the always crowded sterile field. It allows a more ergonomic positioning of the handle relative to the surgical access site, including angular orientations.
In one preferable embodiment, the extension 340 is bonded to the sheath 330 with UV cured adhesive using a molded thermoplastic connector. The extension 340 can be attached to the sheath with a sheath connector 342, as shown in
The instrument 300 includes a handle 310 attached to the sheath 330. An inner lumen can extend through the handle to receive the light delivering element 350. The passing of the light delivering element is performed by incrementally advancing the ablative element 350 along a plurality of positions of the ablation path to produce a substantially continuous lesion.
Ablation with a continuous encircling lesion in the current disclosure is intended to occur by advancing a short, perhaps 1-5 cm long, ablation device that is repetitively positioned, activated, and advanced to create successive therapies along the path of the guide sheath. Advancement includes a certain amount of overlap between the initial position and the advanced position. For example a 5 cm long device might be advanced 4 cm at a time thereby creating a series of local 1 cm lengths that experience double therapies. In this manner a continuous lesion set can be insured.
The handle 310 is designed to allow comfortable, one handed indexing. The indexing button 312 and mechanism provide very positive tactile and audible feedback to the user when each index location is reached. Among other benefits, this design allows the surgeon to effectively index the device without looking at the handle. The surgeon is able to track the location of the ablative diffuser by the feel and sound of the handle's feedback mechanism. The surgeon is also able to visually locate and track the position of the ablative element within the sheath by observing the red glow of device's red aiming beam, which is visible through the shield side of the sheath 330.
The handle 310 has an overall triangular cross section designed to ergonomically fit the surgeons hand. It also includes multiple finger grips which aid single handed actuation of the indexing button 312. The audible and tactile responses are created through use of a spring loaded ball detent assembly 314 contained in the indexing button 312 and corresponding slots formed in the handle at each indexing position.
The handle 310 is sequentially marked by numbers 1-7, one number at each index position. These numbers correspond to the ablating element indexing positions also marked on the sheath. The handle 310 also includes a dynamic o-ring seal which functions to contain the irrigation fluid inside the device while allowing easy indexing.
Alternative embodiments of the device may include long (20 cm+) active lengths that are placed and left in position to create the full encircling path without advancing the device through the guide sheath. This may be enacted at the same dose level (perhaps W unit length) as that delivered by the shorter (4 cm) device or may alternatively be a significantly lower dose. It is believed that a quantity of Joules per volume of tissue must be delivered in order to provide an effective therapy. Therefore the rate of delivery of this energy can be accelerated or slowed depending upon the capabilities of the materials and components therefore allowing the use of various configurations to provide different active lengths. The variable that would be changed to control the amount of energy delivered would then be therapy time.
As shown in
Irrigation serves to increase the efficiency and effectiveness of the device by acting as an optical couple between the diffuser and the tissue. This in turn reduces surface temperatures and subsequent tissue charring, and reduces the chances of collateral injury. The device's irrigation design provides constant low flow when the therapy is not being applied and a higher flow rate during ablation. The continuous low flow rate irrigation is included to prevent blood, biological fluids or other fluids entering the device's irrigation holes, yet prevents the waste and inconvenience of continuous high flow irrigation. When an ablation is begun the system automatically switches to a flow rate of sufficient magnitude for irrigation. The irrigation system design includes a “loop” in the supply line to provide low flow irrigation.
The device is designed so that it may be labeled as class 1 even though it is driven by 60 W of laser power. This is a great advantage for the surgical and OR staff since it relieves them of the complications of class 4 devices such as protective eyewear, warning lights on the OR door, and entry door interlocks. The class 1 labeling is achievable in part because of the diffused light delivery of the device, and also because of the product's TSS. To make the TSS workable, the E360 includes special coverings on the glass fiber. These coverings act to ensure that the laser system shuts down quickly in the case of a fiber break. The fiber is covered from the laser connector to the handle with a woven stainless steel mesh and two layers of polymer tubing. From within the handle to a point near the diffuser, the fiber is covered by two layers of polymer tubing.
Preferred energy sources for use with the hand held cardiac ablation instrument 10 and the balloon catheter 150 of the present invention include laser light in the range between about 200 nanometers and 2.5 micrometers. In particular, wavelengths that correspond to, or are near, water absorption peaks are often preferred. Such wavelengths include those between about 805 nm and about 1060 nm, preferably between about 900 nm and 1000 nm, most preferably, between about 915 nm and 980 nm. In a preferred embodiment, wavelengths around 915 nm are used during epicardial procedures, and wavelengths around 980 nm are used during endocardial procedures. Suitable lasers include excimer lasers, gas lasers, solid state lasers and laser diodes. One preferred AlGaAs diode array, manufactured by Optopower, Tucson, Ariz., produces a wavelength of 980 nm. Typically the light diffusing element emits between about 2 to about 10 watts/cm of length, preferably between about 3 to about 6 watts/cm, most preferably about 4 watts/cm.
The term “penetrating energy” as used herein is intended to encompass energy sources that do not rely primarily on conductive or convective heat transfer. Such sources include, but are not limited to, acoustic and electromagnetic radiation sources and, more specifically, include microwave, x-ray, gamma-ray, and radiant light sources.
The term “curvilinear,” including derivatives thereof, is herein intended to mean a path or line which forms an outer border or perimeter that either partially or completely surrounds a region of tissue, or separate one region of tissue from another. Further, a “circumferential” path or element may include one or more of several shapes, and may be for example, circular, annular, oblong, ovular, elliptical, or toroidal. The term “clasp” is intended to encompass various types of fastening mechanisms including sutures and magnetic connectors as well as mechanical devices. The term “light” is intended to encompass radiant energy, whether or not visible, including ultraviolet, visible and infrared radiation.
The term “lumen,” including derivatives thereof, is herein intended to mean any elongate cavity or passageway.
The term “transparent” is well recognized in the art and is intended to include those materials which allow transmission of energy. Preferred transparent materials do not significantly impede (e.g., result in losses of over 20 percent of energy transmitted) the energy being transferred from an energy emitter to the tissue or cell site. Suitable transparent materials include fluoropolymers, for example, fluorinated ethylene propylene (FEP), perfluoroalkoxy resin (PFA), polytetrafluoroethylene (PTFE), and ethylene-tetrafluoroethylene (ETFE).
The term “catheter” as used herein is intended to encompass any hollow instrument capable of penetrating body tissue or interstitial cavities and providing a conduit for selectively injecting a solution or gas, including without limitation, venous and arterial conduits of various sizes and shapes, bronchioscopes, endoscopes, cystoscopes, culpascopes, colonscopes, trocars, laparoscopes and the like. Catheters of the present invention can be constructed with biocompatible materials known to those skilled in the art such as those listed supra, e.g., silastic, polyethylene, Teflon, polyurethanes, etc.
One skilled in the art will appreciate further features and advantages of the invention based on the above-described embodiments. Accordingly, the invention is not to be limited by what has been particularly shown and described, except as indicated by the appended claims. All publications and references cited herein are expressly incorporated herein by reference in their entirety.
The pending application claims priority to U.S. Provisional Application No. 60/578,021 filed on Jun. 7, 2004 and to U.S. Provisional Application No. 60/672,919 filed on Apr. 18, 2005, which are hereby incorporated by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60578021 | Jun 2004 | US | |
| 60672919 | Apr 2005 | US |
