Patent Publication Number: US-2021178130-A1

Title: Asymmetrical balloon catheter

Description:
FIELD OF THE INVENTION 
     Embodiments are related in general to medical catheters and more specifically to catheters with an inflatable balloon. 
     BACKGROUND 
     A balloon catheter for medical procedures may include an inflatable balloon attached to a catheter body. Fluid may be forced into the balloon through a lumen in the catheter to inflate the balloon. Fluid may be removed from the balloon through the lumen to deflate the balloon. While the balloon is being inflated or deflated, the lumen in the catheter may not be available for other uses. Using the same lumen for adjusting balloon inflation, transporting therapeutic or diagnostic devices or materials, and delivering or removing fluids may substantially increase the amount of time needed to complete a medical procedure. The increase in time may be associated with undesirable medical complications. For example, imaging contrast media may be delivered through the lumen of the catheter. Imaging contrast media be toxic to kidneys and other body organs. A delay in removing the imaging contrast media following a medical procedure, or failure to remove all of the contrast media, may allow some of the contrast media to migrate away from the imaging site. 
     Balloon catheters previously known in the art may have a balloon which extends outward in all directions from an approximately cylindrical catheter body. Such balloons entirely surround the outer circumference of the catheter body. A balloon extending outward in all directions from the outer surface of the catheter body may be difficult to position in some body lumens or may apply pressure to the walls of a body lumen where pressure may be unneeded or ineffective for treatment or diagnostic purposes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  a side view of an example catheter embodiment having an inflated balloon extending asymmetrically outward from an outer surface of the catheter. 
         FIG. 2  is a partial enlarged view of the distal end of the example balloon catheter of  FIG. 1 . 
         FIG. 3  is a view toward the distal end of the example balloon catheter of  FIGS. 1-2 . 
         FIG. 4  is a side view of the example balloon catheter of the previous figures, showing the balloon in an example of a deflated and stowed position. 
         FIG. 5  is a cross-sectional view A-A showing examples of some internal features of the balloon catheter, including an example of a balloon inflation fluid in the interior volume of the example of an inflated balloon and an example of a fluid to be transported through a fluid transport lumen. A location and viewing direction for the cross-section is marked by a section line A-A in  FIG. 2 . 
         FIG. 6  is a cross-sectional view B-B showing an example of a balloon in a deflated and/or stowed position against the outer surface of the catheter body. The balloon fill lumen, balloon fill port, fluid transport lumen, and external fluid ports are shown empty in the example of  FIG. 6 , without the examples of fluids shown in  FIG. 5 . A location and viewing direction for the cross-sectional view is marked by a section line B-B in  FIG. 4 . 
         FIG. 7  is an alternative cross-sectional view B-B showing another example of the balloon in a deflated and/or stowed position against the outer surface of the catheter body. 
         FIG. 8  is another alternative cross-sectional view B-B showing another example of a deflated and/or stowed position of the balloon against the outer surface of the catheter body. 
         FIG. 9  is an alternative cross-sectional view A-A showing another example of an inflated balloon extending asymmetrically outward from the catheter body. 
         FIG. 10  is a partial enlarged view of the distal end of the example balloon catheter of  FIG. 1 , showing an example of perfusion and/or aspiration ports having different sizes. 
         FIG. 11  is a partial enlarged view of the distal end of the example balloon catheter of  FIG. 1 , showing an example of perfusion and/or aspiration ports having an arcuate perimeter shape. 
         FIG. 12  is a partial enlarged view of the distal end of the example balloon catheter of  FIG. 1 , showing an example of perfusion and/or aspiration ports having an arcuate perimeter shape that differs from the arcuate shape example in  FIG. 11 . 
         FIG. 13  is a partial enlarged view of the distal end of the example balloon catheter of  FIG. 1 , showing an example of perfusion and/or aspiration ports arranged in port groups. 
         FIG. 14  is a partial enlarged view of the distal end of the example balloon catheter of  FIG. 1 , showing an example of perfusion and/or aspiration ports configured as narrow slots or slits. 
         FIG. 15  is a partial enlarged view of the distal end of an example balloon catheter having a tapered distal end, and further illustrating an example of the balloon in a deflated and/or stowed position. 
         FIG. 16  is a cross-sectional view C-C showing examples of some internal features of the example catheter of  FIG. 1 . A location and viewing direction for cross-sectional view C-C is marked by a section line C-C in  FIG. 3 . 
     
    
    
     SUMMARY 
     An example apparatus embodiment of a balloon catheter includes a catheter body and an inflatable balloon having longitudinal edges sealed to the catheter body. The balloon is configured to extend laterally outward from an outer surface of the catheter body farther in a first direction when inflated than a second direction. In some example embodiments of the balloon catheter, the first direction may be radially outward from the outer surface of the catheter body and the second direction may be radially opposite the first direction. 
     An example balloon catheter embodiment may include a catheter body formed with a balloon fill lumen in fluid communication with an interior volume of the balloon and a working lumen extending through a proximal end of the catheter body to a distal end of the catheter body. The catheter body may be formed with a balloon fill port in fluid communication with the balloon fill lumen and the interior volume of the balloon. In some example embodiments of the balloon catheter, the balloon fill lumen is not in fluid communication with the working lumen. 
     An example catheter body may further be formed with a fluid transport lumen and a plurality of external fluid ports passing through the outer surface of the catheter body into the fluid transport lumen. In some example embodiments, the catheter body may be formed with some or all of the external fluid ports adjacent a first longitudinal edge of the balloon. An example balloon catheter embodiment may optionally be formed with some or all of the external fluid ports positioned on the outer surface of the catheter body opposite the balloon. In some example embodiments of the balloon catheter, the fluid transport lumen is not in fluid communication with the working lumen. In some example embodiments of the balloon catheter, the balloon fill lumen is not in fluid communication with the fluid transport lumen. 
     An example balloon catheter embodiment may optionally include a luer assembly attached to the catheter body. The luer assembly may include a first hub in fluid communication with the balloon fill lumen; a second hub in fluid communication with the working lumen; and a third hub in fluid communication with the fluid transport lumen. Any one or more of the first, second, and third hubs may be attached to the catheter body separately from the luer assembly. 
     The balloon included in an example balloon catheter embodiment may be formed with a tapered distal end and a tapered proximal end. In a preferred example embodiment of a balloon catheter, the balloon when inflated does not cover the external fluid ports. Some example embodiments of the balloon have a balloon wall shaped as a hollow longitudinal cylindrical segment when the balloon is inflated, with the longitudinal edges of the balloon wall sealed to the outer surface of the catheter. A balloon may alternatively be formed with an outer surface that is a segment of a hollow sphere, or with other surface shapes. 
     An example balloon catheter embodiment may optionally include a radiopaque marker positioned on the catheter body between the balloon and the distal end of the catheter body. An example balloon catheter embodiment may optionally include a radiopaque marker positioned on catheter body adjacent a proximal end of the balloon. A radiopaque marker may optionally be integrally formed with the catheter body or may be attached to a surface of the catheter body. 
     For some example balloon catheter embodiments, the balloon when inflated covers less than about eighty percent of a circumference of the catheter body. When inflated, the balloon may cover at least twenty percent of said circumference of the catheter body. For an example embodiment of a balloon catheter, the catheter body may be formed with a balloon fill lumen in fluid communication with an interior volume of the balloon, a fluid transport lumen, and more than one of an external fluid port passing through the outer surface along the at least twenty percent of the circumference into the fluid transport lumen. 
     In some example embodiments of a balloon catheter, the catheter body may be formed with a first external fluid port having a first diameter and a second external fluid port having a second diameter less than the first diameter. Some example embodiments of a catheter body may alternatively have an external fluid port shaped as a narrow slit. The slit may be sufficiently narrow to remain closed unless forced open by sufficient pressure of a fluid in the catheter, for example pressure of a fluid in the fluid transport lumen of the catheter. 
     Some example embodiments of a balloon catheter are formed with a balloon fill lumen, a fluid transport lumen, a working lumen, and a plurality of external fluid ports passing through a portion of an outer surface of the catheter not covered by the balloon when inflated. The example balloon catheter may be configured for simultaneous transport of a first fluid through the balloon fill lumen, a medical instrument through the working lumen, and a second fluid through the fluid transport lumen. 
     DESCRIPTION 
     Example embodiments of an apparatus include a balloon catheter configured for insertion into body lumens such as arteries, vessels, or lumens in other organs. The disclosed examples of a balloon catheter may further be configured for fluid injection and optionally for fluid evacuation distal to the balloon, proximal to the balloon, and/or at the balloon dilatation region in a body lumen. Balloon catheter embodiments may further be configured to deliver prostheses, pharmaceutical compounds, diagnostic instruments, and surgical instruments through a lumen in the catheter to a site in a body lumen where a therapeutic and/or diagnostic procedure is being performed. A balloon catheter embodiment may optionally carry a pharmaceutical compound, a diagnostic agent or instrument, a therapeutic agent, or a prosthesis on an outer surface of the balloon. 
     The disclosed examples of a balloon catheter include an inflatable balloon made from an elastic material sealed to an outer surface of a catheter body. In some example embodiments a segment of the inflated balloon forms a hollow elongate cylinder. The balloon may optionally be formed with tapered proximal and distal ends attached to, or alternatively formed as an integral part of, the hollow cylindrical segment. The balloon may be stowed in an uninflated state and folded against the outer surface of the catheter body. The balloon may be held securely against the catheter body by evacuating fluid and gas from the interior volume of the balloon, permitting the catheter and balloon to be advanced smoothly through a body lumen to a selected location, where the balloon may be inflated to perform a medical procedure. After the medical procedure is complete, the balloon may be deflated and held against the catheter body by evacuating the interior of the balloon. The balloon or other parts of the catheter may optionally include features such as micro probes to enhance penetration into a wall of a body lumen. 
     When inflated, the balloon extends asymmetrically away from the outer surface of the catheter. The asymmetry of the inflated balloon is established by attaching the balloon to the catheter in such a way that the balloon does not entirely surround the outer circumference of the cylindrical catheter body, i.e., a substantial portion of the outer surface of the catheter body in a gap between the attached longitudinal edges of the balloon remains exposed after inflation. The asymmetric balloon and catheter are not concentric with one another, that is, the cylindrical segment of the balloon and the cylindrical catheter do not share a common longitudinal center. The offset attachment position of the asymmetric balloon to the catheter causes the inflated balloon to extend a greater distance outward from the catheter in one direction than in an opposite direction. The shape and asymmetric position of the inflated balloon on the catheter body prevent the inflated balloon from covering the external fluid ports formed along the longitudinal edges of the balloon and reducing fluid flow through the external fluid ports. 
     A balloon catheter embodiment is preferably formed with separate lumens for inflating the balloon, transporting fluid to a site in the body where a medical procedure is being performed, and optionally for delivering instruments to the site in the body. Changing the balloon inflation, inserting and removing instruments through the catheter, and injecting or evacuating fluid through the catheter may be performed simultaneously or in any preferred order or sequence without removing the catheter from a body lumen. Fluid may flow into and out of the balloon inflation lumen and the fluid transport lumen, and payloads such as instruments, guidewires, and solid, liquid, and/or gaseous materials may be moved in and out of the working lumen. 
     An example balloon catheter embodiment  100  is shown in  FIG. 1 . A balloon catheter  100  in accord with an apparatus embodiment may be referred to herein as an asymmetrical balloon catheter  100 . An example balloon  104  extends asymmetrically outward from a catheter body  102  near a distal end  108 . The balloon  104  in  FIG. 1  is an example of an inflated balloon  110 . At least one and in many embodiments more than one perfusion and/or aspiration ports  136  pass through the longitudinal outer surface  166  of the catheter body  102  adjacent the longitudinal edge  168  of the balloon  104 . The perfusion and/or aspiration ports  136  may also be referred to herein as external fluid ports  136 . The external fluid ports  136  are separated from one another in a longitudinal direction  184 . The external fluid ports  136  may be used, for example, to distribute imaging contrast fluid to a location in a body lumen where a procedure is to be performed and to remove the contrast fluid after imaging is complete. Fluids other than imaging contrast fluid may optionally be delivered and/or removed through the external fluid ports  136 . 
     Unlike catheters having a balloon projecting outward in all directions from the catheter surface and catheters having a balloon surrounding essentially all of the circumference of the catheter when the balloon is inflated, the example catheter embodiments  100  disclosed herein have external fluid ports  136  adjacent the longitudinal edges of the inflated balloon. The external fluid ports  136  in a balloon catheter embodiment  100  may be used to deliver and recover fluids such as imaging contrast fluid while the balloon is fully inflated and while the balloon is being inflated or deflated. Balloon catheter embodiments  100  preferably include at least one longitudinal row  186  of external fluid ports  136  passing through the exposed fraction  174  of the circumference of the outer surface  166  of the catheter body  102  between laterally separated longitudinal edges  168  of the wall  130  of the balloon  104 . Balloon catheter embodiments  100  enable fluids to be placed more precisely, in smaller quantities, and recovered more completely and quickly compared to balloon catheters previously known in the art because of the positioning of the external fluid ports  136  along the edges  182  of the balloon wall  130  and the separate lumens for transporting fluid and inflating the balloon. 
     The asymmetrical extension of the inflated balloon  110  in a first direction  170  more than other directions  172  from the catheter body  102  enables a net contact force per unit area between the outer surface  180  of the balloon and a treatment area in a body lumen to be maximized in the direction of extension  170 , possibly with lower magnitudes of contact force in other directions. The net force is the vector sum of contact forces in all directions between the balloon and a surface in a body lumen or tissue or other objects in a body lumen. Furthermore, compared to previously known balloon catheters having a balloon that surrounds the circumference of the catheter body, the example asymmetric balloon catheter embodiments  100  may be easier to maneuver into small body lumens and into a preferred branch of a branching body lumen, for example by selectively inflating and deflating the balloon to deflect the distal end of the catheter in a preferred direction or by pushing the inflated balloon against a surface to deflect the catheter away from the surface. 
     An example of a luer assembly  148  may be attached to the catheter body  102  near a proximal end  106 . The luer assembly includes one or more hubs in fluid communication with corresponding lumens in the catheter body. A first hub  118  is in fluid communication with the interior of the balloon  104  through an intervening balloon fill lumen in the catheter body  102 . The first hub  118  may be used to deliver balloon inflation fluid to the interior volume of the balloon to inflate the balloon  104 , remove balloon inflation fluid to deflate the balloon, and hold the deflated balloon  104  firmly against the catheter body by evacuating the interior of the balloon. A second hub  120  in fluid communication with the working lumen  124  in the catheter body  102  may be used to deliver and recover prostheses, diagnostic instruments, fluids, and/or surgical instruments to and from a body lumen. A third hub  122  is in fluid communication with the external fluid ports  136  through an intervening fluid transport lumen in the catheter body  102 . Each of the examples of the first hub  118 , second hub  120 , and third hub  122  may further include a luer fitting  142 . One or more of the hubs ( 118 ,  120 ,  122 ) may alternatively be attached to the catheter body separately from the luer assembly  148 . 
       FIG. 2  shows some additional features of the example balloon catheter embodiment of  FIG. 1 . The example of an inflated balloon  110  may be configured to form a cylindrical outer surface  180  extending away from the outer surface  166  of the catheter body  102  in a first radial direction  170  relative to the longitudinal center axis  178  of the catheter body. The inflated balloon  110  preferably does not extend outward in a second radial direction  172  opposite the first radial direction  170 , i.e., the direction of extension of the inflated balloon is asymmetric with respect to the longitudinal center axis  178  of the catheter body  102 . The balloon wall  130  forming the outer surface  180  of the inflated balloon  110  attaches to the outer surface  166  of the catheter body  102  at laterally opposing longitudinal edges  168  of the balloon wall  130 , with sufficient space provided between the sealed joint  132  along the opposing longitudinal edges  168  for at least one longitudinal row  186  of external fluid ports  136  to penetrate the exposed fraction  174  of the outer surface of the catheter. A balloon catheter embodiment  100  may include one or more of a first longitudinal row  186  of external fluid ports  136  adjacent a first longitudinal edge  168  of the balloon wall  130 , an optional second longitudinal row  186  of external fluid ports  136  along a second longitudinal edge  168  laterally opposite the first longitudinal edge  182 , and an optional third longitudinal row  186  through the catheter outer surface  166  opposite the inflated balloon  110 . 
     Continuing with the example of  FIG. 2 , a distal radiopaque marker  144  may be positioned between the tapered distal end  114  of the balloon  104  and the distal end  108  of the catheter body  102 . A proximal radiopaque marker  146  may be positioned proximally to the tapered proximal end  116  of the balloon  104  and proximally to the external fluid ports. The radiopaque markers may be formed as separate parts and attached to the catheter by welding or adhesive, may be electroplated or deposited from a liquid solution onto the catheter body, or may be integrally molded into the body of the catheter. A tungsten band and a tungsten-filled polymer material are examples of radiopaque markers, although other radiopaque materials may be used. All of the external fluid ports  136  may optionally be positioned between the distal radiopaque marker  144  and the proximal radiopaque marker  146 . 
     The balloon  104  is strongly secured to the outer surface  166  of the catheter body  102  at a sealed joint  132  formed by attaching the material of the balloon wall to the material of the catheter body. The attachment between the balloon wall  130  and the outer surface  166  of the catheter preferably forms an uninterrupted liquid-tight and gas-tight bond all the way around the contact perimeter between the balloon and catheter. The sealed joint  132  may be formed by thermal welding, solvent welding, ultrasonic welding, laser welding, and/or adhesive bonding. 
     As suggested in  FIG. 2 , the balloon  104  may optionally be formed with a fold line or crease  134  to encourage the balloon to fold smoothly against the surface of the catheter when the balloon is deflated to its stowed position. The example crease  134  may be formed by subjecting the folded balloon to heat and pressure against the surface of a mandrel or by molding a ridge or groove into the balloon wall. 
       FIG. 3  shows a view toward the distal end of an example asymmetric balloon catheter embodiment  100 . The inflated balloon  110  extends asymmetrically away from the outer surface  166  and longitudinal center axis  178  of the catheter body  102 . An instrument lumen  124 , also referred to herein as a working lumen  124 , passes through the distal end  108  of the catheter. 
       FIG. 3  further illustrates the asymmetry of the balloon  104 , which extends further from the surface of the catheter in a first radial direction  170  than in a second radial direction  172  opposite the first radial direction. The circumference  173  of the outer surface  166  of the catheter body may be represented as the sum of an exposed fraction  174  that is not covered by the inflated balloon  110  and a covered fraction  176  that projects into the interior volume  140  of the balloon  104 . The covered fraction may further include the area occupied by the sealed joint  132  attaching the balloon wall to the outer surface of the catheter. The interior volume  140  of the balloon  104  is bordered by the balloon wall  130  and the covered fraction  176  of the longitudinal outer surface  166  of the catheter body  102 . 
       FIG. 4  shows the balloon  104  in an example of a deflated state  112 , folded and stowed against the outer surface  166  of the catheter body  102 .  FIG. 4  further illustrates an example of a position of the crease  134  along a fold line of the folded balloon  112 . 
       FIG. 5  shows examples of some internal details of the asymmetric balloon catheter  100 . The balloon wall  130  of the example of an inflated balloon  110  is sealed against the outer surface  166  of the catheter body  102  by the sealed joint  132 . The inflated balloon encloses an interior volume  140  in fluid communication with the first hub  118  through the intervening balloon fill lumen  128  and one or more balloon fill ports  138 . Fluid and/or gas may be introduced into the first hub  118  and forced through the balloon fill lumen  128  and balloon fill ports  138  to inflate the balloon. Fluid and/or gas may be withdrawn from the interior volume  140  through the first hub  118  to deflate the balloon. Fluid, for example imaging contrast fluid, may be transported from the third hub  122  to the external fluid ports  136  through the fluid transport lumen  126 . Fluid in a body lumen may be drawn into and transported through the external fluid ports  136  and fluid transport lumen  126  by suction applied to the third hub  122 , for example by retracting the plunger of a syringe attached to the luer fitting  142  of the hub. 
     As suggested in the example of  FIG. 5 , the edges  182  of the balloon wall  130  are attached with a gas-tight and liquid-tight seal to the outer surface  166  of the catheter body  102  on opposite lateral sides of the balloon fill lumen  128 . The balloon wall  130  and sealed joint  132  of the inflated balloon  110  preferably do not block the external fluid ports  136 , i.e., fluid may flow into and out of the external fluid ports while the balloon is inflated. The external fluid ports  136  are preferably not in fluid communication with the interior volume  140  of the balloon  104  by any lumen formed in the catheter. 
     The fraction  176  of the circumference  173  of the catheter outer surface  166  covered by the inflated balloon  110 , corresponding approximately to the fraction of the circumference projecting into the interior volume  140  of the inflated balloon  110 , is about 20% of the total circumference  173  in the example balloon catheter embodiment  100  of  FIG. 5 . In the example of  FIG. 5 , about 80% of the total circumference  173  remains exposed outside the illustrated example of a fully inflated balloon  110  and the sealed joint  132 . For the example balloon catheter embodiments  100  disclosed herein, the covered fraction is preferably greater than or equal to about 5% of the total circumference of the catheter body to provide sufficient space for the balloon fill ports  138  without the edges  182  of the balloon wall and the sealed joint  132  between the balloon wall  120  and the outer surface of the catheter body blocking the balloon fill ports. The maximum value of the exposed fraction  174  is therefore less than or equal to about 95% of the total circumference for the embodiments  100  disclosed herein. 
       FIG. 5  further shows an example of a balloon inflation fluid  200  filling the interior volume  140  of the inflated balloon  110 , the balloon fill port  138 , and the balloon fill lumen  128 . Pumping balloon inflation fluid  200  into the balloon inflates the balloon and removing inflation fluid from the balloon deflates the balloon. In  FIG. 5 , an example of a fluid  204  to be transported to or from a body lumen, for example imaging contrast media, a buffer solution, a body fluid, or a therapeutic compound, is represented by stippling filling the fluid transport lumen  126  and the external fluid ports  136 . A schematic representation of an example of a therapeutic or diagnostic instrument  202  is shown in the working lumen  124 . Examples of a therapeutic or diagnostic instrument include, but are not limited to, a camera, an optical fiber, a guide wire, a cutting instrument, forceps, and a self-expanding prosthesis. A therapeutic compound, lubricant, or surgical tool may optionally be carried aboard a balloon catheter embodiment by being placed against the outer surface of the catheter body. 
     Some balloon catheter embodiments  100  have an inflated balloon  110  with a partial cylindrical outer surface  180  blending into a tapered distal end  114  and a tapered proximal end  116  as suggested in the examples of  FIG. 1 ,  FIG. 5 , and other figures. An inflated balloon  110  may alternately be formed with a partial spherical outer surface  188  as suggested in the example of  FIG. 5 . A balloon  104  having a spherical outer surface  188  may optionally be formed with tapered distal  114  and/or proximal  116  end caps transitioning the spherical surface to the surface of the catheter. 
     Examples of a balloon  104  in deflated and/or stowed positions  112  are shown in  FIGS. 6-8 . In the example of  FIG. 6 , the interior volume of the balloon  104  has been evacuated sufficiently to collapse the balloon onto the outside surface  166  of the catheter body  102 . The balloon wall  130  folds along the crease  134  to lie smoothly against the outside of the catheter body with the folded balloon conforming to the shape of the catheter body&#39;s surface. The deflated balloon  112  is shown with a single fold line  134  in the examples of  FIGS. 5-7  and with two fold lines  134  in the example of  FIG. 8 . 
     In the examples of an asymmetric balloon catheter  100  in  FIGS. 1-8 , the exposed fraction  174  of the total circumference  173  of the catheter body  102  may be greater than the fraction  176  covered by the inflated balloon  110 .  FIG. 9  shows an example of an asymmetric balloon catheter  100  having the exposed fraction  174  substantially smaller than the covered fraction  176 . In the example of  FIG. 9 , the inflated balloon  110  covers about 80 percent of the catheter&#39;s total circumference  173 , positioning most of the catheter body  102  inside the interior volume  140  of the inflated balloon  110 . As with the other example embodiments  100 , the inflated balloon  110  and catheter body  102  are not concentric, i.e. do not share a common longitudinal center axis. A covered fraction  176  greater than about 95 percent may interfere with the placement and function of the external fluid ports  136 . For some of the example embodiments  100  disclosed herein, the covered fraction  176  is preferably less than about 80% of the total circumference  173  to provide sufficient space for the external fluid ports  136 , as suggested in the example of  FIG. 9 . The minimum size of the exposed fraction  174  is therefore greater than or equal to about 20% of the total circumference  173  for the example of  FIG. 9  and greater than or equal to about 5% of the total circumference in general for all balloon catheters in accord with an embodiment  100 . 
       FIGS. 10-14  illustrate examples of alternative shapes, sizes, and separation distances for the external fluid ports  136 . The size and shape of external fluid ports  136  and the separation distances between adjacent external fluid ports may be selected to determine the locations where fluids are emitted and recovered from a balloon catheter embodiment, and possibly to establish relative flow rates of fluids through some external fluid ports compared to other ports. For example, the external fluid ports  136  may be formed as cylindrical apertures  154  arranged in a longitudinal row  186  through the outer surface  166  of the catheter body  102 . In  FIG. 10 , the diameter of each example of an external fluid port  136  has been selected to establish approximately equal volumetric flow rates of fluid through each of the external fluid ports  136  in one longitudinal row  186  of external fluid ports  136 . For example, some external fluid ports formed as cylindrical apertures  154  with a diameter D 1   160 , other external fluid ports with a diameter D 2   162 , possibly with D 2 &lt;D 1 , and yet other external fluid ports with a diameter D 3   164 , possibly with D 3 &lt;D 2 . Other balloon catheter embodiments may use a different arrangement of diameters D 1 , D 2 , and/or D 3 . 
     An example balloon catheter embodiment  100  with different separation distances between adjacent external fluid ports  136  is shown in  FIG. 4 , where separation distances S 1   206 , S 2   208 , and S 3   210  may be selected to determine a location of fluid flows into and/or out of the catheter relative to the distal end  108  or the position of the balloon  104 . Separation distances S 1 , S 2 , and S 3  may be equal to one another in some balloon catheter embodiments and different from one another in other balloon catheter embodiments. 
     In the examples of  FIGS. 11 and 12 , the external fluid ports  136  are formed with an arcuate shape  156  or a different arcuate shape  157 . In the example of  FIG. 13 , port groups  150  are spaced in a longitudinal direction  184  along the longitudinal edges  168  of the balloon  104 , each port group  150  including at least two external fluid ports  136 . The external fluid ports in a port group may have different perimeter shapes from one another as suggested in  FIG. 13 , where one of the external fluid ports in a port group may have an arcuate perimeter shape  156  and another of the external fluid ports in the same port group may have a different arcuate perimeter shape  157 . A balloon catheter embodiment  100  may optionally have more than one size and/or shape of external fluid ports  136 . 
     Examples of external fluid ports  136  formed as slots  158  are shown in  FIG. 14 . The slots  158  may optionally be formed as narrow cuts or slits. The slots  158  may be sufficiently narrow to remain closed unless forced open by the pressure of fluid in the fluid transport lumen  126 . After being opened to allow fluid to flow out the external fluid ports  136 , reducing pressure in the fluid transport lumen may allow the slots to close, preventing fluid from flowing through the external fluid ports. 
     The catheter body  102  may optionally be formed with a tapered distal end  152  as suggested in the example of  FIG. 15 . A tapered distal end  152  may be configured to carry a self-expanding prosthesis or other surgical device on the outer surface of the catheter body.  FIG. 15  further shows an example of the balloon  104  in a deflated and/or stowed position  112 . In some example balloon catheter embodiments  100 , the deflated and folded balloon may cover some of the external fluid ports  136  as suggested in  FIG. 4  and  FIG. 15 . 
       FIG. 16  shows an example asymmetric balloon catheter  100  in a longitudinal cross section C-C. In the illustrated example, the inflated balloon  110  extends outward from the outer surface  166  of the catheter body farther in a first direction  170  than a second direction  172 . For some embodiments, the first direction  170  is radially outward from the longitudinal center axis  178  of the catheter body  102  and the second direction  172  is an outward direction opposite the first direction  170 . As suggested in the example embodiment  100 , the balloon fill lumen  128 , the working lumen  124 , and the fluid transport lumen  126  are formed in a longitudinal direction  184  through the catheter body  102  and are not in fluid communication with each other within the catheter body. External fluid ports  136  pass through the outer surface  166  of the catheter body to the fluid transport lumen  126 . Balloon fill ports  138  pass through the outer surface of the catheter body to the balloon fill lumen  128 , establishing fluid communication between the interior volume  140  of the balloon and the balloon fill lumen. The working lumen  124  passes from the second hub at the proximal end  106  through the distal end  108 . 
     Unless expressly stated otherwise herein, ordinary terms have their corresponding ordinary meanings within the respective contexts of their presentations, and ordinary terms of art have their corresponding regular meanings.