DETAILED DESCRIPTION

[0031] Referring to FIG. 1A, a catheter 100 is shown according to a first embodiment of the invention. The catheter 100 has a proximal end 130 and a distal end 114. Of course, this figure is not necessarily to scale and in general use the proximal end 130 is far upstream of the features shown in FIG. 1A.

[0032] The catheter 100 may be used within a guide catheter 102, and generally includes an outer tube 103, a dual balloon 134, and an inner tube 122. These parts will be discussed in turn.

[0033] The guide catheter 102 provides a tool to dispose the catheter 100 adjacent the desired location for, e.g., angioplasty or reduction of atrial fibrillation. Typical guide catheter diameters may be about 6 french to 9 french, and the same may be made of polyether blockamide, polyamides, polyurethanes, and other similar materials. The distal end of the guide catheter is generally adjacent the proximal end of the dual balloon 134, and further is generally adjacent the distal end of the outer tube 103.

[0034] The ability to place the guide catheter is a significant factor in the size of the device. For example, to perform angioplasty in the carotid arteries, which have an inner diameter of about 4 to 6 mm, a suitably sized guide catheter must be used. This restricts the size of the catheter 100 that may be disposed within the guide catheter. A typical diameter of the catheter 100 may then be about 7 french or less or about 65 to 91 mils. In a second embodiment described below, a catheter for use in the coronary arteries is described. Of course, which catheter is used in which artery is a matter to be determined by the physician, taking into account such factors as the size of the individual patient's affected arteries, etc.

[0035] The outer tube 103 houses the catheter 100 while the latter traverses the length of the guide catheter 102. The outer tube 103 may have a diameter of about 4 french to 7 french, and the same may be made of polyether blockamide, poly-butylene terephtalate, polyurethane, polyamide, polyacetal polysulfone, polyethylene, ethylene tetrafluoroethylene, and other similar materials.

[0036] The distal end of the outer tube 103 adjoins the proximal end of the dual balloon 134. The outer tube 103 provides a convenient location for mounting a proximal end of an outer balloon 104 within the dual balloon 134, and further may provide an inlet 128 for providing a fluid such as a liquid to a first interior volume 106 between the dual balloons. In some cases, an inlet 128 per se may not be necessary: the fluid, which may also be a sub-atmospheric level of gas or air, may be provided during manufacture in the first interior volume 106. In this case, the proximal and distal ends of the first interior volume may be sealed during manufacture. The inlet 128 may be at least partially defined by the annular volume between the interior of the outer tube 103 and the exterior of the inner tube 122.

[0037] The dual balloon 134 includes an outer balloon 104 and an inner balloon 108. Between the two is the first interior volume 106. The outer balloon 104 may be inflated by inflating the interior volume 106. The inner balloon 108 has a second interior volume 110 associated with the same. The inner balloon 108 may be inflated by inflating the second interior volume 110.

[0038] To avoid the occurrence of bubbles in the bloodstream, both the inner balloon 108 and the outer balloon 104 may be inflated using biocompatible liquids, such as Galden® fluid, perfluorocarbon-based liquids, or various contrast agents. There is no need that the fluid inflating one of the interior volumes be the same fluid as that inflating the other. Additional details on these fluids are described below.

[0039] In the case of the first interior volume 106, this fluid may be, e.g., stationary or static: in other words, it need not be circulated. In the case of the second interior volume 110, this fluid would in general be circulated by an external chiller (not shown). The chiller may be, e.g., a gear pump, peristaltic pump, etc. It may be preferable to use a gear pump over a peristaltic pump as the attainable pressure of the former is generally greater than that of the latter. Moreover, gear pumps have the advantageous property of being linear, i.e., their output varies in direction proportion with their revolutions per minute. Two types of gear pumps which may be employed include radial spur gear pumps and helical tooth gear pumps. Of these, the helical tooth gear pump may be more preferable as the same has been associated with higher pressures and a more constant output. The ability to achieve high pressures may be important as the cooling fluid is required to pass through a fairly narrow, e.g., five to seven french, catheter at a certain rate. For the same reason, the viscosity of the fluid, at the low temperatures, should be appropriately low. In this way, e.g., the flow may be increased. For example, an appropriate type of fluid may be Galden® fluid, and in particular Galden® fluid item number “HT-55”, available from Ausimont Inc. of Thorofare, N.J. At −55° C., this fluid has a viscosity of 2.1 centiStokes. At −70° C., this fluid has a viscosity of 3.8 centiStokes. It is believed that fluids with such viscosities at these temperatures would be appropriate for use.

[0040] The so-called “cones” of the balloons 108 and 104, indicated generally by reference numeral 132, may be made somewhat thicker than the remainder of the balloon sections. In this way, the heat transfer efficiency in these sections is significantly less than over the remainder of the balloon sections, this “remainder” effectively defining a “working region” of the balloon. In this way, the cooling or “cryoplasty” may be efficiently localized to the affected area rather than spread over the length of the balloon.

[0041] The inner tube 122 is disposed within the interior of the dual balloon 134 and within the interior of the guide catheter 102. The inner tube 122 includes a supply lumen 120, a return lumen 118, and a guidewire lumen 116. The guidewire lumen 116 may have sizes of, e.g., 17 or 21 mils inner diameter, in order to accommodate current standard sized guidewires, such as those having an outer diameter of 14 mils. This structure may be preferable, as the pressure drop encountered may be substantially less. In use, the supply lumen 120 may be used to supply a circulating liquid to the second interior volume 110. The return lumen 118 may be used to exhaust the circulating liquid from the second interior volume to the external chiller. As may be seen from FIG. 1A, both lumens 118 and 120 may terminate prior to the distal end 114 of the catheter 100. The lumen arrangement may be seen more clearly in FIG. 1B. FIG. 1C shows an alternate such arrangement, and one that may provide an even better design for minimal pressure drop. In this design, lumens 118′ and 120′ are asymmetric about guidewire lumen 116′.

[0042] A set of radio opaque marker bands 112 may be disposed on the inner tube 122 at locations substantially adjacent the cones 132 to define a central portion of the “working region” of the balloons 104 and 108. This working region is where the “cryoplasty” procedures described below may substantially occur.

[0043] As noted above, the proximal portion of the outer balloon 104 is mounted on the outer tube 103 at its distal end. The distal end of the outer balloon 104 is secured to the distal end of the catheter 100 and along the inner tube 122. In contrast, both the proximal and distal ends of the inner balloon 108 may be secured to the inner tube 122 to create a sealed second interior volume 110.

[0044] At least two skives 124 and 126 may be defined by the inner tube 122 and employed to allow the working fluid to exit into the second interior volume 110 and to exhaust the same from the second interior volume 10. As shown in the figure, the skive 124 is in fluid communication with the lumen 120 and the skive 126 is in fluid communication with the lumen 118. Here, “fluid communication” refers to a relationship between two vessels where a fluid pressure may cause a net amount of fluid to flow from one vessel to the other.

[0045] The skives may be formed by known techniques. A suitable size for the skives may be from about 50 mils to 125 mils.

[0046] A plurality of tabs 119 may be employed to roughly or substantially center the inner tube 122 within the catheter 100. These tabs may have the shape shown, the shape of rectangular or triangular solids, or other such shapes so long as the flow of working fluid is not unduly impeded. In this specification, the phrase “the flow of working fluid is not unduly impeded” is essentially equated to the phrase “substantially center”. The tabs 119 may be made of polyether blockamide, poly-butylene terephtalate, polyurethane, polyamide, polyacetal polysulfone, polyethylene, ethylene tetrafluoroethylene, and other similar materials, and may have general dimensions of from about 3 mils to 10 mils in height, and by about 10 mils to 20 mils in width.

[0047] In a method of use, the guide catheter 102 may be inserted into an affected artery or vein such that the distal tip of the guide catheter is just proximal to an affected area such as a calcified area or lesion. Of course, it is noted that typical lesions do not occur in the venous system, but only in the arterial.

[0048] This step provides a coarse estimate of proper positioning, and may include the use of fluoroscopy. The guide catheter may be placed using a guide wire (not shown). Both the guide catheter and guide wire may already be in place as it may be presumed a balloon angioplasty or stent placement has previously been performed.

[0049] The catheter 100 may then be inserted over the guide wire via the lumen 116 and through the guide catheter 102. In general, both a guide wire and a guide catheter are not strictly necessary—one or the other may often suffice. During insertion, the dual balloon 134 may be uninflated to maintain a minimum profile. In fact, a slight vacuum may be drawn to further decrease the size of the dual balloon 134 so long as the structural integrity of the dual balloon 134 is not thereby compromised.

[0050] When the catheter 100 is distal of the distal tip of the guide catheter 102, a fine positioning step may occur by way of the radio opaque marker bands 112. Using fluoroscopy, the location of the radio opaque marker bands 112 can be identified in relation to the location of the lesion. In particular, the catheter may be advantageously placed at the location of the lesion and further such that the lesion is between the two marker bands. In this way, the working region of the balloon 134 will substantially overlap the affected area, i.e., the area of the lesion.

[0051] Once placed, a biocompatible heat transfer fluid, which may also contain contrast media, may be infused into the first interior volume 106 through the inlet 128. While the use of contrast media is not required, its use may allow early detection of a break in the balloon 104 because the contrast media may be seen via fluoroscopy to flow throughout the patient's vasculature. Subsequently a biocompatible cooling fluid may be circulated through the supply lumen 120 and the return lumen 118. Before or during the procedure, the temperature of the biocompatible cooling fluid may be lowered to a therapeutic temperature, e.g., between −40° C. and −60° C., although the exact temperature required depends on the nature of the affected area. The fluid exits the supply lumen 120 through the skive 124 and returns to the chiller through the skive 126 and via the return lumen 118. It is understood that the respective skive functions may also be reversed without departing from the scope of the invention.

[0052] The biocompatible cooling fluid in the second interior volume 110 chills the biocompatible heat transfer fluid within the first interior volume 106 to a therapeutic temperature of, e.g., between about −25° C. and −50° C. The chilled heat transfer fluid transfers thermal energy through the wall of the balloon 104 and into the adjacent intimal vascular tissue for an appropriate therapeutic length of time. This time may be, e.g., about ½ to 4 minutes.

[0053] Upon completion of the therapy, the circulation of the biocompatible cooling fluid may cease. The heat transfer fluid within the first interior volume 106 may be withdrawn though the inlet 128. The balloons 104 and 108 may be collapsed by pulling a soft vacuum through any or all of the lumens 124, 126, and 128. Following collapse, the catheter 100 may be withdrawn from the treatment site and from the patient through the guide catheter 102.

[0054] To inhibit restenosis, the following therapeutic guidelines may be suggested: 1

[0055] Substantially the same catheter may be used to treat atrial fibrillation. In this method, the catheter is inflated as above once it is in location. The location chosen for treatment of atrial fibrillation is such that the working region spans a portion of the left atrium and a portion of the affected pulmonary vein. Thus, in this embodiment, the working region of the catheter may have a length of about 5 mm to 30 mm. The affected pulmonary vein, of the four possible pulmonary veins, which enter the left atrium, may be determined by electrophysiology studies.

[0056] To maneuver the catheter into this location, a catheter with a needle point may first be inserted at the femoral vein and routed up to the right atrium. The needle of the catheter may then be poked through the interatrial septum and into the left atrium. The catheter may then be removed if desired and a guide catheter disposed in the same location. A guide wire may be used through the guide catheter and may be maneuvered at least partially into the pulmonary vein. Finally, a catheter such as the catheter 100 may be placed in the volume defining the intersection of the pulmonary vein and the left atrium.

[0057] A method of use similar to that disclosed above is then employed to cool at least a portion of, and preferably all of, the circumferential tissue. The coldness of the balloon assists in the adherence of the circumferential tissue to the balloon, this feature serving to increase the overall heat transfer rate.

[0058] The catheter 100 above may be particularly useful for procedures in the carotid arteries by virtue of its size. For use in the coronary arteries, which are typically much smaller than the carotid artery, an even smaller catheter may be desired. For example, one with an outer diameter less than 5 french may be desired.

[0059] Referring to FIG. 2A, a catheter 200 is shown according to a second embodiment of the invention. This embodiment may be particularly useful for use in the coronary arteries because the dimensions of the catheter 200 may be considerably smaller than the dimensions of the catheter 100. However, in several ways the catheter 200 is similar to the above-described catheter 100. In particular, the catheter 200 has a proximal end 230 and a distal end 214 and may be used within a guide catheter 202. The catheter 200 includes an outer tube 203, a dual balloon 234, and an inner tube 222.

[0060] The ability to place the guide catheter is a significant factor in the size of the device. For example, to perform angioplasty in the coronary arteries, which have an inner diameter of about 1½ to 4½ mm, a suitably sized guide catheter may be used. This then restricts the size of the catheter 200 which may be disposed within the guide catheter. A typical diameter of the catheter 200 may then be about 3 french or less or about 35-39 mils. The same may be placed in the femoral artery in order to be able to track to the coronary arteries in a known manner.

[0061] Analogous to these features in the catheter 100, the outer tube 203 houses the catheter 200 and may have an outside diameter of about 5 french to 7 french, and the same may be made of similar materials. The distal end of the outer tube 203 adjoins the proximal end of the dual balloon 234. The outer tube 203 provides a mounting location for an outer balloon 204, and further provides an inlet 228 for providing a fluid such as a liquid to a first interior volume 206 between the dual balloons. As noted in connection with catheter 100, an inlet 228 per se may not be necessary: the fluid, which may also be a sub-atmospheric level of air, may be provided in the first interior volume 206. Also as above, the proximal and distal ends of the volume may be sealed during manufacture. The inlet 228 may be at least partially defined by the annular volume between the interior of the outer tube 203 and the exterior of the inner tube 222.

[0062] The dual balloon 234 includes an outer balloon 204 and an inner balloon 208. These balloons are basically similar to balloons 104 and 108 described above, but may be made even smaller for use in the smaller coronary arteries.

[0063] The same types of fluids may be used as in the catheter 100.

[0064] The inner tube 222 is disposed within the interior of the dual balloon 234 and within the interior of the guide catheter 202. The inner tube 222 includes a supply lumen 220 and a return lumen 218.

[0065] A set of radio opaque marker bands 212 may be disposed on the inner tube 222 for the same reasons disclosed above in connection with the marker bands 112.

[0066] As noted above, the proximal portion of the outer balloon 204 is mounted on the outer tube 203 at its distal end. The distal end of the outer balloon 204 is secured to the distal end of the catheter 200 and along the inner tube 222. In contrast, both the proximal and distal ends of the inner balloon 208 may be secured to the inner tube 222 to create a sealed second interior volume 210.

[0067] At least two skives 224 and 226 may be defined by the inner tube 222 and employed to allow the working fluid to exit into the second interior volume 210 and to exhaust the same from the second interior volume 210.

[0068] A plurality of tabs 219 may be employed to roughly or substantially center the inner tube 222 within the catheter 200 as in catheter 100. These tabs may have the same general geometry and design as tabs 119. Of course, they may also be appropriately smaller to accommodate the smaller dimensions of this coronary artery design.

[0069] The tabs 119 and 219 are particularly important in the catheters 100 and 200, as contact by the inner tube of the outer tube may also be associated with an undesired conductive heat transfer prior to the working fluid reaching the working region, thereby deleteriously increasing the temperature of the working fluid at the working region.

[0070] The method of use of the catheter 200 is generally the same as for the catheter 100. Known techniques may be employed to place the catheter 200 into an affected coronary artery. For the catheter 200, an external guidewire may be used with appropriate attachments to the catheter.

[0071] Referring to FIG. 3, an alternative embodiment of a catheter 300 which may be employed in PV ablation is detailed. In this figure, a dual balloon system 301 is shown; however, the balloons are not one within the other as in FIG. 1. In this embodiment, a warm balloon 302 is distal of a cold balloon 304. Warm balloon 302 may be used to anchor the system 301 against movements, which may be particularly useful within a beating heart. Cold balloon 304 may then be employed to cryo-ablate a circumferential lesion at the point where a pulmonary vein 306 enters the left atrium 308.

[0072] Within the cold balloon 304, a working fluid may be introduced via an outlet port 308 and may be retrieved via an inlet port 310. Ports 308 and 310 may be skived in known fashion into the catheter shaft lumens whose design is exemplified below.

[0073] As noted above, the warm balloon 302 serves to anchor the system 301 in the pulmonary vein and left atrium. The warm balloon 302 also serves to stop blood, which is traveling in the direction indicated by arrow 312, from freezing upon contact with the cold balloon 304. In this way, the warm balloon 302 acts as an insulator to cold balloon 304.

[0074] As the warm balloon 302 does not require convective heat transfer via a circulating working fluid, it may be served by only one skived port, or by two ports, such as an inlet port 314 and an outlet port 316, as shown in FIG. 3. In some embodiments, a separate lumen or lumens may be used to fill the warm balloon. In an alternative embodiment, a valve mechanism may be used to fill the warm balloon using fluid from the cold balloon. In the case where only one port is used to fill the warm balloon, draining the same requires a slight vacuum or negative pressure to be placed on the lumen servicing the inlet/outlet port. A benefit to the two lumen design is that the warm balloon may be inflated and deflated in a more expeditious manner.

[0075] Typical pressures within the warm balloon may be about 1-2 atm (10-30 psi), and thus maintains a fairly low pressure. An appropriate fluid will be biocompatible, and may be Galden fluid, D5W, and so on. Typical pressures within the cold balloon may be about 5-7 atm, for example about 6 atm (e.g., at about 100 psi), and thus maintains a higher pressure. An appropriate fluid may be Galden fluid, e.g., HT-55, D5W, and so on. The volume of fluid required to fill the cold balloon may vary, but may be about 4-8 cc. The cold balloon may be about 2 to 2½ cm long, and have a diameter of 1 to 2½ cm.

[0076] In some embodiments, the warm balloon may be glued or otherwise attached to the cold balloon. In the case where only one port is used to fill the warm balloon, draining both balloons may simply entail closing either the return lumen or the supply lumen, and drawing a vacuum on the other. In this way, both the cold and warm balloons may be evacuated. In any case, a standard medical “indeflator” may be used to pressurize and de-pressurize the various lumens and balloons.

[0077] FIG. 4 shows an embodiment of the arrangement of lumens within the catheter. In particular, supply and return lumens for the cold balloon 304 are shown by lumens 318 and 320, respectively. Supply and return lumens for the warm balloon 302 are shown by lumens 322 and 324, respectively, although as noted only one may be used as required by the dictates of the user. A guidewire lumen 326 is also shown. An alternative arrangement is shown in FIG. 5, where the corresponding lumens are shown by primes.

[0078] In the above lumen designs, the exterior blood is exposed to the cold supply flow. Referring to FIG. 6, an alternative lumen design is shown in which the cold fluid supply lumen 328 is exposed to only the cold fluid return lumen 330. An insulation space 332 may also be employed. In this way, the heat flux from the exterior flow is minimized and the cold fluid may reach the cold balloon at a lower temperature. One drawback to such a system is that the operational pressure may be higher.

[0079] Referring back to FIG. 4, the overall catheter outer diameter may be about 0.130″, e.g. about 10 french, including an insulation sleeve and guide discussed below. The catheter shaft 303 itself may be about 0.110″ and may be made of, e.g., polyethylene (PE), and preferably a combination of a low density PE and a high density PE.

[0080] The inlet and outlet ports or inlet/outlet port of the warm balloon may be skived from the lumens 322 and 324. Referring to FIG. 7, the warm balloon 302 itself may be made of a sleeve 332 of silicone tubing of, e.g., 35 durometer on the “D” scale, and held in place by two pieces of PET heat shrink tubing 334. Alternative methods of securing the warm balloon during inflation may include metal bands or an adhesive.

[0081] Referring back to FIG. 3, marker bands 336 may be employed within either or both of the cold balloon and warm balloon to assist the physician is disposing the same in an appropriate location. The marker bands typically denote the working areas of the balloons, and may be made of Pt, Iridium, Au, etc.

[0082] In the ablation procedure, the working cold fluid may exit the circulation system or chiller at, e.g., about −85° C. The circulation system or chiller may be, e.g., a two-stage heat exchanger. The fluid may then enter the catheter at about −70° C. to about −75° C., and may strike the balloon at about −55° C. to about −65° C. The overall procedure may take less than a minute to circumferentially ablate the desired tissue up to several minutes. Of course, these numbers are only exemplary and the same depend on the design of the system and fluids used.

[0083] Mapping electrodes 338 may be employed at the distal end of the warm balloon. These mapping electrodes may each have a wire attached, the wires extending down, e.g., the supply and return lumens for the warm fluid or the cold fluid. The mapping electrodes 338 may be used to detect stray electrical fields to determine where ablation may be needed and/or whether the ablation procedure was successful. The mapping electrodes may typically be about 2-3 mm apart from each other.

[0084] Construction of the warm balloon typically involves adhering the same to the shaft 303 and skiving the inlet and outlet ports. In some instances, it may be desired to place a silicone sleeve 340 on the proximal and/or distal ends of the warm and/or cold balloons. The silicone sleeve 340 may then serve to further insulate the non-working sections of the balloons from blood that would otherwise potentially freeze during a procedure. The silicone sleeve would typically be attached only at a portion of its length, such as that indicated by circle 342, so that the same may slide along the balloon as the balloon is inflated. In addition to insulation effects, the silicone sleeve also serves to assist in collapsing the balloon during deflation.

[0085] The entire catheter shaft 303 may be surrounded by an insulation catheter sleeve 344 (see FIG. 4). Sleeve 344 may have a thickness of, e.g., 0.01 inches, and may be made of a foamed extrusion, e.g., that with voids of air disposed within. The voids further assist the insulating effect since their heat transfer is extremely low. A void to polymer ratio of, e.g., 20% to 30% may be particularly appropriate. Such foamed extrusions are available from, e.g., Applied Medical Resources in Laguna Niguel, Calif., or Extrusioneering, Inc., in Temecula, Calif.

[0086] To prevent damage to tissue other than where the ablation is to occur, such as at the insertion site near the femoral vein and around the puncture point through the atrial septum, an insulation sleeve may be used as noted above.

[0087] The invention has been described above with respect to particular embodiments. It will be clear to one of skill in the art that numerous variations may be made from the above embodiments with departing from the spirit and scope of the invention. For example, the invention may be combined with stent therapies or other such procedures. The dual balloon disclosed may be used after angioplasty or may be an angioplasty balloon itself. Furthermore, while the invention has occasionally been termed herein a “cryoplasty catheter”, such a term is for identification purposes only and should not be viewed as limiting of the invention. Fluids that may be used as heat transfer fluids include perfluorocarbon-based liquids, i.e., halogenated hydrocarbons with an ether bond, such as FC 72. Other materials that may be used include CFCs, Freon®, or chemicals that when placed together cause an endothermic reaction. Preferably, low viscosity materials are used as these result generally in a lessened pressure drop. The balloons may be made, e.g., of Pebax, PET/PEN, PE, PA 11/12, PU, or other such materials. Either or both of the dual balloons may be doped to improve their thermal conductivities. The shaft of inner tube 122 may be made of Pebax, PBT, PI/PEI, PU, PA 11/12, SI, or other such materials. The precise shapes and dimensions of the inner and outer lumens, while indicated in, e.g., FIGS. 1B, 1C, and 2B, may vary. The lumen design shown in FIGS. 1B-1C may be employed in the catheter of FIG. 2A and vice-versa. Embodiments of the invention may be employed in the field of cold mapping, where a circle of tissue is cooled to see if the affected part has been reached. If the affected tissue is that which is being cooled, a more vigorous cooling may be instituted. Other variations will be clear to one of skill in the art, thus the invention is limited only by the claims appended hereto.