Abstract:
Imaging catheters having irrigation capabilities are described herein. Generally, the device may include a first inner membrane which is sealed and serves to position the device within or relative to a lumen. This balloon structure, when filled with fluid, expands and is engaged in direct contact with the tissue. A second (outer) membrane is not completely sealed and instead provides a pathway for delivery of fluid at the treatment site for effecting various treatments. Imaging systems, optionally articulatable, may be positioned within the balloon as well as electrodes positionable upon the balloon may be utilized to facilitate tissue treatments.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional App. 61/151,764 filed Feb. 11, 2009, which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to balloon catheter devices used for imaging and treating tissue regions of interest. More particularly, the present invention relates generally to methods and devices for balloon catheters which can be used to image and treat tissue regions of interest, such as a vessel ostium, for various conditions, such as atrial fibrillation, etc. 
       SUMMARY OF THE INVENTION 
       [0003]    An inflatable balloon catheter having an irrigation sheath may generally comprise two expandable membranes disposed about a catheter. The first inner membrane may be generally or substantially sealed to a catheter and may serve as a balloon to facilitate positioning of the device, e.g., within a lumen. This balloon structure when filled with fluid may expand and become engaged in direct contact with the tissue. A second (outer) membrane may be at least partially positioned over the balloon and may provide a pathway for delivery of fluid at the treatment site. In treating a tissue region with ablation energy, particularly within a body lumen such as a heart chamber, one device in particular may be used as shown and described in detail in U.S. Pat. No. 6,605,055, which is incorporated herein by reference in its entirety. As disclosed, an inflatable balloon which is sealed to a catheter may be advanced within a body lumen, such as within a chamber of a subject&#39;s heart, and inflated for contact against a tissue region to be treated. 
         [0004]    A balloon catheter having a primary balloon member disposed about a catheter for inflation within the body, e.g., with the heart, may provide a transmission waveguide for radiation (such as laser radiation) projecting from an optical fiber to the ablation site, e.g., an ostium of a vessel. The catheter is typically an elongated hollow instrument having at least one lumen in communication with the port. 
         [0005]    The outer membrane or sheath may define a distal opening to partially cover the primary balloon such that an irrigating fluid such as saline may be introduced through the annular conduit between the inner and outer membranes and exit through this opening to clear the region of blood between the balloon and the underlying tissue. In phototherapy applications, the removal of blood from the treatment site allows for the unobstructed and uniform delivery of ablative energy. In addition, the irrigating fluid cools the surface of the target site, thereby preventing overheating or burning of the tissue or coagulation. Also, it is noted that removal of blood allows direct visualization of the tissue surface with an appropriate imaging system. 
         [0006]    An imager, e.g., CMOS or CCD electronic image sensor, may be affixed to an inside wall of the primary balloon with an electrical connection leading out of the distal end of the balloon to an image processing system for displaying the image, e.g., on a monitor. Direct visualization of the tissue surface is made possible when blood is flushed out and/or squeezed from the field of view. At least one light source, such as an LED, may also be affixed to an inside wall of the primary balloon coupled to an electrical connection as well. Both the light source and imager may be angled or positioned such that their field of view is directed towards the distal end of the balloon to capture and/or illuminate the underlying tissue region through the transparent balloon. 
         [0007]    Another variation may include a fiberscope, which may be articulatable to control a direction of its distal end, positioned within the interior of the balloon. The distal end of the fiberscope may be articulated from outside the patient&#39;s body by the operator to direct an angle of the fiberscope within the balloon to view any region of contacted tissue through the balloon. The fiberscope may be optionally coupled to an imaging system, e.g., CMOS or CCD electronic image sensor, positioned external to the patient&#39;s body. 
         [0008]    In yet another variation, an imager, such as an electronic imager, may be positioned upon the distal end of an articulatable member. The articulatable member may be manipulated from outside the patient&#39;s body to direct a viewing angle of the imager within the balloon. An imaging system may be located outside the patient&#39;s body for communicating with the imager for processing and/or displaying the images of the contacted tissue regions captured within the patient. 
         [0009]    In yet another variation, fluid such as saline may be introduced through the conduit formed between the sheath and balloon. The introduced fluid, particularly an electrolytic fluid such as saline, may also be used to conduct ablative energy into the underlying tissue from the one or more electrodes which may be positioned along an outer surface of the balloon or sheath. The one or more electrodes may be positioned at locations where the fluid exits the conduit and contacts the underlying tissue such that the fluid flowing into contact with the electrodes may conduct any discharged energy, e.g., radio frequency (RF) energy, to ablate the tissue in combination with or exclusive of the ablative radiation energy projected from the optical fiber. The energy delivered via electrodes is not limited to RF energy may but also include any number of other ablative forms of energy such as cryo-ablation, microwave, ultrasonic, etc. Moreover, utilization of ablation energy in contact or in direct proximity to the tissue may provide additional ablative effects should blood obscure the radiation energy. Also, these electrodes may be also used independently from the laser ablation system or may be used to map electric potentials at the tissue surface. 
         [0010]    Another variation of the balloon catheter may include one or more pores defined circumferentially about the distal end of the sheath such that the introduced fluid passing through the conduit may be diffused through the one or more pores into contact against the underlying tissue. The diffusion of the fluid through the pores may facilitate distribution of the ablation energy over the tissue. 
         [0011]    In yet another variation, one or more ultrasound transducers may be positioned near or at a distal end of the balloon and/or sheath for placement in proximity to or in contact against the tissue region of interest. The one or more ultrasound transducers may be actuated to deliver ultrasonic signals into the underlying tissue to detect a thickness of the tissue, e.g., at the locations at which the radiative energy is to be applied. Knowledge of the thickness of the tissue to be ablated may help determine how much energy to provide or to determine, e.g., an appropriate amount of fluid flow needed to cool the tissue surface, etc., amongst other parameters. Tissue thickness detection utilizing ultrasound transducers is described in further detail in U.S. patent application Ser. No. 12/118,439 filed May 9, 2008 (U.S. Pat. Pub. 2009/0030412 A1), which is incorporated herein by reference in its entirety. Various methods may be utilized, e.g., by a controller such as a microprocessor in communication with the ultrasound transducers, for controlling and/or adjusting various parameters of an ablation procedure, e.g., power, laser intensity, flow rate, temperature, etc. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  shows a cross-sectional view of a variation of a balloon catheter apparatus having an imaging system attached to an inside wall of the balloon. 
           [0013]      FIG. 2  shows a cross-sectional view of another variation of a balloon catheter apparatus having an articulatable fiberscope within the balloon and coupled at a proximal end to an imaging system, such as a CMOS or CCD imaging system. 
           [0014]      FIG. 3  shows a cross-sectional view of another variation of a balloon catheter apparatus having imaging sensor, such as an electronic imager, affixed at the distal end of an articulatable member within the balloon. 
           [0015]      FIG. 4  shows a cross-sectional side view of yet another variation illustrating one or more electrodes positioned upon the balloon surface for transmitting energy through a fluid into the underlying tissue. 
           [0016]      FIG. 5  shows a cross-sectional side view of a balloon catheter apparatus which defines a plurality of openings or pores through which energy may be transmitted into the underlying tissue surface. 
           [0017]      FIG. 6  shows a cross-sectional side view of a balloon catheter apparatus having one or more ultrasound transducers positioned along the balloon for detecting a thickness of the underlying tissue. 
           [0018]      FIG. 7  shows an example of a flow chart illustrating one method for controlling parameters of an ablation system in response to detected tissue thickness. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    In treating a tissue region with ablation energy, particularly within a body lumen such as a heart chamber, various devices and methods may be utilized for visualizing and treating the tissue. One device is shown and described in detail in U.S. Pat. No. 6,605,055, which is incorporated herein by reference in its entirety. As disclosed, an inflatable balloon which is sealed to a catheter may be advanced within a body lumen, such as within a chamber of a subject&#39;s heart, and inflated for contact against a tissue region to be treated. 
         [0020]      FIG. 1  illustrates a cross-sectional side view of a balloon catheter  50  having a primary balloon member  56  disposed about a catheter  14  for inflation (via port  23 ) within the body (e.g., with the heart) to provide a transmission waveguide for radiation  13  (such as laser radiation) projecting from an optical fiber to the ablation site  12 , e.g., an ostium of a vessel. A laser generator  28  may be in optical communication with the optical fiber for delivering the radiation  13 . The primary balloon member  56  may be generally or substantially sealed and can be inflated to position the catheter  14  within the lumen. The catheter  14  is typically an elongated hollow instrument having at least one lumen in communication with the port  23 . The primary balloon  56  is shown engaged in direct contact with a body lumen  52  (e.g., a pulmonary vein) and an outer membrane or sheath  16  may be at least partially disposed about the primary balloon member  56  for providing an irrigation path via the annular conduit  20  formed between the two membranes to the body lumen. Primary balloon member  56  and sheath  16  may accordingly form a respective inner and outer membrane of the balloon assembly. 
         [0021]    The outer membrane or sheath  16  may define a distal opening to partially cover the primary balloon  56 , as shown, such that an irrigating fluid such as saline may be introduced through the annular conduit  20  between the inner and outer membranes and exit through this opening to clear the region of blood between the balloon and the underlying tissue. In phototherapy applications, the removal of blood from the treatment site allows for the unobstructed and uniform delivery of ablative energy  13 . In addition, the irrigating fluid cools the surface of the target site, thereby preventing overheating or burning of the tissue or coagulation. Also, it is noted that removal of blood allows direct visualization of the tissue surface with an appropriate imaging system. 
         [0022]    In this variation, an imager  32 , e.g., CMOS or CCD electronic image sensor, may be affixed to an inside wall of the primary balloon  56  with an electrical connection  34  leading out of the distal end of the balloon to an image processing system for displaying the image, e.g., on a monitor. Direct visualization of the tissue surface is made possible when blood is flushed out and/or squeezed from the field of view. At least one light source  30 , such as an LED, may also be affixed to an inside wall of primary balloon  56  coupled to an electrical connection  36  as well. Both light source  30  and imager  32  may be angled or positioned such that their field of view is directed towards the distal end of the balloon  56  to capture and/or illuminate the underlying tissue region  52  through the balloon  56  which may be optically transparent. 
         [0023]    Another variation is illustrated in the cross-sectional side view of  FIG. 2 , which shows a fiberscope  38 , which may be articulatable to control a direction of its distal end, positioned within the interior of balloon  56 . The distal end of fiberscope  38  may be articulated from outside the patient&#39;s body by the operator to direct an angle of fiberscope  38  within the balloon  56  to view any region of contacted tissue through the balloon  56 . The fiberscope  38  may be optionally coupled to an imaging system  40 , e.g., CMOS or CCD electronic image sensor, positioned external to the patient&#39;s body. 
         [0024]    In yet another variation,  FIG. 3  shows an example where an imager, such as an electronic imager  32 , may be positioned upon the distal end of an articulatable member  42 . As previously described, articulatable member  42  may be manipulated from outside the patient&#39;s body to direct a viewing angle of imager  32  within the balloon  56 . Imaging system  40  may be located outside the patient&#39;s body for communicating with the imager  32  for processing and/or displaying the images of the contacted tissue regions captured within the patient. 
         [0025]    In yet another variation,  FIG. 4  shows a cross-sectional side view of a tissue region in proximity to body lumen  52  ablated by projecting radiation  13  from optical fiber  60  positioned within balloon  56 . As previously described, fluid  17  such as saline may be introduced through conduit  20  formed between sheath  16  and balloon  56 . The introduced fluid  17 , particularly an electrolytic fluid such as saline, may also be used to conduct ablative energy into the underlying tissue from one or more electrodes  62  which may be positioned along an outer surface of balloon  56  and/or sheath  16 , e.g., near or at a distal end of the balloon  56  and/or sheath  16 . The one or more electrodes  62  may be positioned at locations where fluid  17  exits conduit  20  and contacts the underlying tissue  52  such that the fluid  17  flowing into contact with electrodes  62  may conduct any discharged energy, e.g., radio frequency (RF) energy, to ablate the tissue  52  in combination with or exclusive of the ablative radiation energy  13  projected from optical fiber  60 . The energy delivered via electrodes  62  is not limited to RF energy may but also include any number of other ablative forms of energy such as cryo-ablation, microwave, ultrasonic, etc. Moreover, utilization of ablation energy in contact or in direct proximity to the tissue may provide additional ablative effects should blood obscure the radiation energy  13 . Also, these electrodes  62  may be also used independently from the laser ablation system or may be used to map electric potentials at the tissue surface. 
         [0026]    Another variation of balloon catheter  50  is shown in the cross-sectional side view of  FIG. 5 . This example illustrates a balloon catheter assembly similarly configured to the variation shown in  FIG. 4  with one or more electrodes  62  for delivering ablation energy conducted via the discharged fluid  17 . In this variation, however, one or more pores  64  may be defined circumferentially about the distal end of the sheath  16  such that the introduced fluid  17  passing through conduit  20  may be diffused through the one or more pores  64  into contact against the underlying tissue. The diffusion of the fluid  17  through the pores  64  may facilitate distribution of the ablation energy over the tissue. 
         [0027]    In yet another variation,  FIG. 6  shows a cross-sectional side view of a balloon assembly having one or more ultrasound transducers  66  positioned near or at a distal end of the balloon  56  and/or sheath  16  for placement in proximity to or in contact against the tissue region of interest. The one or more ultrasound transducers  66  may be actuated to deliver ultrasonic signals into the underlying tissue to detect a thickness of the tissue, e.g., at the locations  12  at which the radiative energy  13  is to be applied. Knowledge of the thickness of the tissue to be ablated may help determine how much energy to provide or to determine, e.g., an appropriate amount of fluid flow needed to cool the tissue surface, etc., amongst other parameters. Tissue thickness detection utilizing ultrasound transducers is described in further detail in U.S. patent application Ser. No. 12/118,439 filed May 9, 2008 (U.S. Pat. Pub. 2009/0030412 A1), which is incorporated herein by reference in its entirety. 
         [0028]      FIG. 7  shows a flowchart  70  with one example of a method for an algorithm that may be utilized, e.g., by a controller such as a microprocessor in communication with the ultrasound transducers  66 , for controlling and/or adjusting various parameters of an ablation procedure, e.g., power, laser intensity, flow rate, temperature, etc. In this example, once the target tissue region has been identified  72  for treatment, such as visually or otherwise, the targeted tissue thickness may be detected  74 , e.g., via the one or more ultrasound transducers  66 . A tissue thickness threshold, e.g., a minimum tissue thickness, may be predetermined and programmed into the device for comparison against the detected thickness  76  to ensure patient safety. 
         [0029]    In the event that the detected thickness fails to meet the threshold level, the operator may be alerted (visual or auditory) of this anomaly  82  prompting the operator to re-measure  84  the tissue thickness. If the re-measured tissue thickness meets the threshold level, the ablation procedure may continue. Otherwise, the operator may manually determine the ablation parameters  86 , e.g., lowering power levels, etc., and begin the ablation procedure  80 . In the event that the re-measured tissue thickness meets the threshold level  76 , the controller may automatically determine the appropriate ablation parameters  78 , e.g., based upon a table of ablation parameters for a given thickness value, and the ablation procedure may begin  80 . 
         [0030]    The applications of the disclosed invention discussed above are not limited to certain treatments or regions of the body, but may include any number of other treatments and areas of the body. Modification of the above-described methods and devices for carrying out the invention, and variations of aspects of the invention that are obvious to those of skill in the arts are intended to be within the scope of this disclosure. Moreover, various combinations of aspects between examples are also contemplated and are considered to be within the scope of this disclosure as well.