Abstract:
The present invention is directed to a balloon catheter having an irrigation sheath. The balloon catheter has a first expandable membrane forming an occluding balloon. A second membrane forms a sheath about the occluding balloon for providing irrigation to a body lumen. Fluid is provided to the occluding balloon to position the catheter and/or occlude the flow of blood. Fluid is then passed through the sheath to irrigate the target site. In one embodiment of the present invention, the sheath has a plurality of fluid releasing pores.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to catheters for diagnosis of, or delivery of localized therapy to, a target region of a body lumen, and, in particular, to balloon structures for positioning a catheter or similar device within the heart. 
     Catheterization is a type of procedure performed for a variety of purposes, including diagnostic, interventional, and other therapeutic procedures. In catheterization techniques, a long tubular catheter is introduced into the body through a puncture site. It is then passed to a target site, usually through the circulatory system. The therapeutic procedures are usually accomplished at the distal end of the catheter by manipulation of the proximal portion of the catheter remaining outside the body, or by introducing instruments or therapeutic agents into the catheter body at the proximal end for passage through the catheter to the target site. 
     During many of these procedures, it is necessary to keep the distal end of the catheter in a relatively stable position to perform the desired procedure. In order to ensure that a catheter is maintained in the proper position, it is common to use an expandable balloon disposed near the distal end of the catheter shaft. These catheters typically include a lumen that extends from the proximal end to the balloon end and provide fluid to the balloon for its inflation. Inflation of the balloon causes the balloon to engage the wall of a lumen. The procedure is then performed. Once completed, the fluid is removed from the balloon, thereby deflating the balloon and allowing the catheter to be removed. 
     Balloon catheters are commonly used to facilitate a number of percutaneous medical treatments such as pressure monitoring, cardiac output and flow monitoring, angioplasty, artificial vaso-occlusion, cardiac support, and cardiac ablation. Such catheters can also deliver therapeutic agents or energy once a target region is identified. Cardiac ablation catheters, for example, delivery energy, which may be in the form of heat, electric current or radiation, in order to eliminate (i.e. “ablate”) the source of a cardiac arrhythmia. Such catheters typically include an optical apparatus contained within the catheter. The catheter can also include other structures, such as a lumen through which pharmaceutics, biologics, or photoactivatable agents are delivered, as well as mapping electrodes, and/or a sampling system for sampling a tissue or fluid specimen. 
     Although various types of balloon anchored catheters have been proposed, they often suffer from one or more limitations. A serious drawback to using balloon catheters is that the balloon can cause a total block to the flow of blood through the lumen, depriving tissue of needed blood. This can cause tissue damage, even when the procedure is performed expediently. In addition, blood that is trapped in the occluded area can clot and cause thrombosis. 
     Consequently, there is a need for better balloon catheter devices that can provide irrigation to reduce the chance of clotting, and/or locally clear blood from a target site without necessarily causing a total blockage of blood flow. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a balloon catheter having an irrigation sheath. The structure can include two expandable membranes disposed about a catheter. The first inner membrane is generally or substantially sealed and serves as a balloon to position the device within 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. 
     In one embodiment, the outer membrane is an irrigation 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 catheter can be easily removed from the body lumen. 
     In another embodiment of the present invention, the distal end of the sheath, which provides fluid to the treatment site, is position to direct fluid toward the tissue being ablated. In yet another embodiment, the sheath contains fluid releasing pores. 
     One advantage of the present invention is that irrigation provided by the second membrane reduces hematocrit and the chance of clotting. 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. Moreover, the use of two membranes permits the delivery of two separate fluids, a physiologically compatible fluid and an inflation fluid. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a schematic, cross-sectional view of a balloon catheter apparatus having an irrigation sheath according to the invention. 
     FIG. 2 is a more detailed schematic side view of the balloon catheter apparatus of FIG.  1 . 
     FIG. 3 shows another balloon catheter apparatus according to the invention having conduits for providing inflation fluid, and irrigation fluid to the apparatus. 
     FIG. 4 shows another embodiment of the balloon catheter apparatus according to the invention having pores for providing irrigation fluid to a treatment site. 
     FIG. 5 shows another embodiment of the balloon catheter apparatus according to the invention having a sheath positioned to deliver fluid to a target ablation site. 
    
    
     DETAILED DESCRIPTION 
     The features and other details of the invention will now be more particularly described and pointed out in the claims. It will be understood that the particular embodiments of the invention are shown by way of illustration and not as limitations of the invention. The principle features of this invention can be employed in various embodiments without departing from the scope of the invention. 
     In FIG. 1, a balloon catheter  50  for cardiac ablation is shown including 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 projecting radiation  13  to the ablation site  12 . The primary balloon member  56  is generally or substantially sealed and can be inflated to position the catheter  14  within a lumen. The catheter  14  is typically an elongated hollow instrument having at least one lumen  23 . The primary balloon  56  is shown engaged in direct contact with a body lumen  52  (e.g. a pulmonary vein). A sheath  16  is partially disposed about the primary balloon member  56  for providing irrigation (via conduit  20 ) to the body lumen. Primary balloon member  56  and sheath  16  form the inner and outer membranes of the present invention. 
     In FIG. 2, the balloon catheter of FIG. 1 is shown in use. Fluid  17 , introduced between the inner membrane formed by the primary balloon member  56  and the outer membrane formed by sheath  16 , provides irrigation to an inner body lumen region  26 . The fluid  17  can be any physiologically compatible fluid, such as saline. Once the fluid  17  is introduced into the lumen region  26 , any blood or other substance remaining in the region is flushed out. 
     Another embodiment of balloon catheter  50  is shown in FIG. 3 having two conduits  20  and  24  within the catheter  14 . Conduit  20  provides irrigation fluid, such as saline, to the sheath  16 . Conduit  24  provides inflation fluid, such as deuterium oxide (D 2 O), to the primary balloon member  56 . 
     FIG. 4 illustrates another embodiment of the balloon catheter of the present invention. The opening  22  of the sheath  16  is positioned to deliver fluid  17  to the target ablation site  12 . This approach allows the fluid to contact the ablation site, thereby cooling the tissue to prevent over-heating or coagulation. 
     FIG. 5 illustrates another embodiment of the balloon catheter of the present invention. The sheath  16  contains pores  19  for releasing fluid near or at the target ablation site  12 . One having ordinary skill in the art will readily appreciate that the pores can be any shape or size. In addition, the sheath  16  can be sealed on both ends. 
     A person having ordinary skill in the art will readily appreciate that the size, quantity, and placement of the pores  19 , and the position of the sheath opening  22  can be used in conjunction with one another to provide a desired amount of fluid to the treatment site. 
     In another embodiment, the primary balloon  56  is preshaped to form a parabolic like shape. This is accomplished by shaping and melting a TEFLON® film in a preshaped mold to effect the desired form. The primary balloon  56  and sheath  16  of the present invention are preferably made of thin wall polyethylene teraphthalate (PET). The thickness of the membranes is preferably 5-50 micrometers, and more preferable, 10-20 micrometers. When inflated, the diameter of the membranes is preferably in the range of 20-30 millimeters. 
     The balloon catheters of the present invention can be used for a variety of procedures, including laparoscopic, endoluminal, perivisceral, endoscopic, thoracoscopic, intra-articular and hybrid approaches. For example, atrial therapies can be performed by inserting an apparatus of the invention into the femoral vein. The catheter  14  having inner and outer membranes, e.g. primary balloon  56  and sheath  16 , fixedly attached thereto is guided through the inferior vena cava, and into the right atrium, and if required, it is guided into the left atrium via atrial septal puncture. Left ventricular treatment can be performed by inserting flexible elongate member  32  into the femoral artery. The catheter  14  is guided through the iliac artery, the aorta, through the aortic valve and into adjacent to the left ventricle. Once the primary balloon  56  is proximate to the tissue ablation site, a solution can be injected through lumen  20  into the sheath  16  to force blood and/or body fluids away from the treatment site. An optical apparatus is then guided through catheter  14  to a position proximate to the tissue ablation site  12  and energy, e.g., laser energy, is emitted through primary balloon  56 . Preferably, the composition of the primary balloon member  56  is transparent to the energy emitted through optical apparatus. 
     The primary balloon and sheath can be deflated by applying a vacuum that removes the fluid from the balloon. A syringe or other known methods can be used to remove the fluid. Once the primary balloon and sheath are fully deflated, the catheter can be easily removed from the body lumen. 
     The term lumen, including derivatives thereof, is herein intended to mean any cavity or lumen within the body which is defined at least in part by a tissue wall. For example, cardiac chambers, the uterus, the regions of the gastrointestinal tract, the urinary tract, and the arterial or venous vessels are all considered illustrative examples of body spaces within the intended meaning. 
     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. 
     It should be understood that the term “balloon” encompasses deformable hollow shapes which can be inflated into various configurations including balloon, circular, tear drop, etc., shapes dependent upon the requirements of the body cavity. 
     The term “transparent” is well recognized in the art and is intended to include those materials which allow transmission of energy through, for example, the primary balloon member. 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). 
     Those having ordinary skill in the art will know, or be able to ascertain, using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. These and all other equivalents are intended to be encompassed by the following claims. All publications and references cited herein including those in the background section are expressly incorporated herein by reference in their entirety.