FIELD OF THE INVENTION

[0001] The present invention relates generally to invasive probes, and specifically to an invasive probe configured to perform cryoablation .

BACKGROUND OF THE INVENTION

[0002] Cryoablation is a medical procedure that uses extreme cold to destroy tissue. Cryoablation can be performed on cardiac tissue in order to restore normal heart rhythm by disabling heart cells that create an irregular heartbeat. During this minimally invasive procedure, a thin flexible tube called a balloon catheter is used to locate and freeze the heart tissue that triggers an irregular heartbeat .

[0003] U.S. Patent Application 2012/0165803 to Bencini et al., describes a method for electrical mapping and cryoablation with a balloon catheter. The method includes delivering a coolant into a balloon at the distal end of the catheter. In one embodiment, a coolant delivery lumen is coupled to a coil that wraps around a shaft contained within the balloon, and the coolant is delivered via multiple apertures in the coil. In another embodiment, the coolant may be delivered into the balloon via apertures at the end of the coolant delivery lumen.

[0004] U.S. Patent 5,147,355 to Friedman et al., describes a cryoablation catheter and a method of performing cryoablation. The cryoablation catheter is configured to throttle cryogenic fluid in order to provide reversible cooling. Additionally, the catheter can sense electrical activity while performing the cryoablation . [0005] U.S. Patent Application 2010/0179526 to Lawrence, describes a medical system that comprises a cryoablation balloon catheter. The catheter includes a guide tube inside the balloon, and a coolant transfer tube that extends along the guide tube and has a coiled distal end that wraps around the guide tube. The coiled distal end comprises multiple spray apertures that are configured to deliver coolant into the balloon.

[0006] U.S. Patent Application 2014/ 0142666to Phelan et al., describes a cryo-therapeutic device (e.g., a catheter) . The device includes a shaft surrounded by an inflatable body (e.g., a balloon) that has multiple lumens. Each of the lumens can be fluidly independent of one another and configured to receive different types of fluids and/or fluids having different temperatures.

[0007] The description above is presented as a general overview of related art in this field and should not be construed as an admission that any of the information it contains constitutes prior art against the present patent application.

[0008] Documents incorporated by reference in the present patent application are to be considered an integral part of the application except that to the extent any terms are defined in these incorporated documents in a manner that conflicts with the definitions made explicitly or implicitly in the present specification, only the definitions in the present specification should be considered.

SUMMARY OF THE INVENTION

[0009] There is provided, in accordance with an embodiment of the present invention, a medical probe including an insertion tube having a distal end configured for insertion into a body cavity and containing a lumen that opens through the distal end, and an inflatable balloon deployable through the lumen into the body cavity. The medical probe includes an injection tube that extends from the lumen into the balloon and includes a plurality of apertures, which are distributed radially around the injection tube and open into the balloon, and which are configured for delivery of a refrigerant from the injection tube into the balloon. The medical probe additionally includes a directional control tube that surrounds and is rotatable around the injection tube and includes a semi-tubular section that is configured to cover one or more of the apertures, thereby blocking exit of the refrigerant through the one or more of the apertures.

[0010] In some embodiments, the medical probe also includes a processor and a handle coupled to the insertion tube and having a control, wherein the processor is configured to regulate delivery of the refrigerant to the injection tube in response to signals received from the control. In additional embodiments, the medical probe also includes a processor and a handle coupled to the insertion tube and having a control, wherein the processor is configured to regulate extension of the directional control tube over the apertures in response to signals received from the control. In one embodiment, the handle includes a visual indicator, and wherein the processor is configured to present, on the visual indicator, a level of the extension of the directional control tube over the apertures.

[0011] In further embodiments, the medical probe also includes a processor and a handle coupled to the insertion tube and having a control, wherein the processor is configured to regulate rotation of the directional control tube relative to the anatomy in response to signals received from the control. In supplemental embodiments, the medical probe also includes a handle that has a control that regulates rotation of the directional control tube around the injection tube. In one embodiment, the handle includes a visual indicator, and wherein the processor is configured to present, on the visual indicator, an angle of rotation of the directional control around the injection tube.

[0012] In some embodiments, the semi-tubular section includes multiple sections having different blocking angles, each of the sections configured to cover different respective numbers of apertures. In additional embodiments, the semi-tubular section includes a marker that is visible under fluoroscopy. In further embodiments, the directional control tube includes a location sensor that transmits signals indicating a location of the semi tubular section relative to the injection tube.

[0013] In supplemental embodiments, the semi-tubular section has an arcuate cross-section. In one embodiment, the directional control tube includes a location sensor that transmits signals indicating an orientation of the semi-tubular section relative to an anatomy of the body cavity. In another embodiment, the directional control tube blocks the exit of the refrigerant by redirecting the refrigerant .

[0014] There is also provided, in embodiments of the present invention, a method for fabricating a medical probe, including providing an insertion tube having a distal end configured for insertion into a body cavity and containing a lumen that opens through the distal end, providing an inflatable balloon deployable through the lumen into the body cavity, providing an injection tube that extends from the lumen into the balloon and includes a plurality of apertures, which are distributed radially around the injection tube and open into the balloon, and which are configured for delivery of a refrigerant from the injection tube into the balloon, and providing a directional control tube that surrounds and is rotatable around the injection tube and includes a semi tubular section that is configured to cover one or more of the apertures, thereby blocking exit of the refrigerant through the one or more of the apertures.

[0015] There is additionally provided, in embodiments of the present invention, a method, including inserting a distal end of a medical probe into a body cavity of a patient, the medical probe including an insertion tube having a distal end configured for insertion into a body cavity and containing a lumen that opens through the distal end, an inflatable balloon deployable through the lumen into the body cavity, an injection tube that extends from the lumen into the balloon and includes a plurality of apertures, which are distributed radially around the injection tube and open into the balloon, and which are configured for delivery of a refrigerant from the injection tube into the balloon, and a directional control tube that surrounds and is rotatable around and advanceable over the injection tube and includes a semi-tubular section that is configured to cover one or more of the apertures, thereby blocking exit of the refrigerant through the one or more of the apertures. The method also includes selecting, in the body cavity, an area of tissue to ablate in a region distal to the medical probe, pressing the distal side of the balloon against the selected area of the tissue, rotating the directional control tube so that the semi tubular section covers one or more of the apertures facing away from the selected area of the tissue, and delivering the refrigerant to the injection tube in order to cryoablate the selected area of the tissue.

[0016] There is further provided, in embodiments of the present invention, a medical probe including a tubular member extending along a longitudinal axis from a proximal end to a distal end, at least one expandable membrane coupled to the tubular member between the proximal and distal ends, an injection tube disposed inside the at least one expandable membrane, the injection tube having a plurality of apertures disposed angularly about the injection tube to allow a fluid to flow out of the plurality of apertures into the at least one expandable membrane, and a control tube disposed between the injection tube and the tubular member, the control tube having a plurality of arcuate sections disposed along a length of the control tube with each arcuate section defining less than a complete circumference of the control tube so that some of the apertures of the injection tube are exposed to the expandable membrane as a function of a position of the control tube with respect to the injection tube.

[0017] In some embodiments, the injection tube includes a stationary member with respect to the rotatable and translatable control tube. In additional embodiments, the injection tube is rotatable and translatable with respect to the stationary control tube. In further embodiments, at least one radiopaque marker is disposed on at least one of the injection tube and the control tube to permit identification of a position of the injection tube relative to the control tube.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The disclosure is herein described, by way of example only, with reference to the accompanying drawings, wherein:

[0019] Figure 1 is a schematic pictorial illustration of a medical system configured to perform cryoablation using a balloon catheter, in accordance with an embodiment of the present invention;

[0020] Figure 2 is a schematic cross-sectional longitudinal view of a distal end of the balloon catheter that comprises a blocking element, in accordance with an embodiment of the present invention;

[0021] Figure 3 is a schematic longitudinal view of the blocking element, in accordance with a first embodiment of the present invention;

[0022] Figure 4 is a schematic longitudinal view of the blocking element, in accordance with a second embodiment of the present invention;

[0023] Figure 5 shows schematic cross-sectional latitudinal views of sections of the blocking element, in accordance with a second embodiment of the present invention;

[0024] Figure 6 is a flow diagram that schematically illustrates a method of using the balloon catheter to cryoablate intracardiac tissue in a heart; and

[0025] Figure 7 is a schematic detail view of the distal end of the balloon in a chamber of the heart, in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

OVERVIEW

[0026] Embodiments of the present invention describe a system and a method for performing cryoablation of cardiac tissue. As described hereinbelow, the system comprises a medical probe that includes an insertion tube, an inflatable balloon, an injection tube and a directional control tube. The insertion tube has a distal end configured for insertion into a body cavity and contains a lumen that opens through the distal end, and the inflatable balloon is deployable through the lumen into the body cavity. The insertion tube extends from the lumen into the balloon and comprises a plurality of apertures, which are distributed radially around the insertion tube and open into the balloon, and which are configured for delivery of a refrigerant from the injection tube into the balloon. The directional control tube surrounds and is rotatable around the second tube and comprises a semi-tubular section that is configured to cover one or more of the apertures, thereby blocking or redirecting the refrigerant from the one or more of the apertures.

[0027] By rotating the directional control tube, a medical professional using a system implementing embodiments of the present invention can direct the refrigerant to a section of the balloon, thereby preferentially performing cryoablation on cardiac tissue in contact with the section of the balloon. For example, when performing cryoablation on an ostium into a pulmonary vein, it may be preferable to direct more refrigerant toward the anterior wall of the vein which is significantly thicker than the posterior wall of the vein, thereby protecting esophageal tissue (i.e., from being damaged by the refrigerant) which lies just beyond the anterior wall. SYSTEM DESCRIPTION

[0028] Figure 1 is a schematic pictorial illustration of a medical system 20 comprising a medical probe 22 (e.g., an intracardiac catheter) and a control console 24, in accordance with an embodiment of the present invention. System 20 may be based, for example, on the CARTO ^® system, produced by Biosense Webster Inc.

(33 Technology Drive, Irvine, CA 92618 USA) . In embodiments described hereinbelow, it is assumed that probe 22 is used for diagnostic or therapeutic treatment, such as performing ablation of heart tissue in a heart 28. Alternatively, probe 22 may be used, mutatis mutandis, for other therapeutic and/or diagnostic purposes in the heart or in other body organs.

[0029] Probe 22 comprises an insertion tube 30 and a handle 32 coupled to a proximal end of the insertion tube. By manipulating handle 32, a medical professional 34 can insert probe 22 into a body cavity in a patient 36. For example, medical professional 34 can insert probe 22 through the vascular system of patient 36 so that a distal end 26 of probe 22 enters a chamber of heart 28 and engages endocardial tissue at a desired location or locations.

[0030] In some embodiments, medical professional 34 can use a fluoroscopy unit 38 to visualize distal end 26 inside heart 28. Fluoroscopy unit 38 comprises an X-ray source 40, positioned above patient 36, which transmits X-rays through the patient. A flat panel detector 42, positioned below patient 36, comprises a scintillator layer 44 which converts the X-rays which pass through patient 36 into light, and a sensor layer 46 which converts the light into electrical signals. Sensor layer 46 typically comprises a two dimensional array of photodiodes, where each photodiode generates an electrical signal in proportion to the light detected by the photodiode. [0031] Control console 24 comprises a processor 48 that converts electrical signals from fluoroscopy unit 38 into an image 50, which the processor presents as information regarding the procedure on a display 52. Display 52 is assumed, by way of example, to comprise a cathode ray tube (CRT) display or a flat panel display such as a liquid crystal display (LCD) , light emitting diode (LED) display or a plasma display. However other display devices can also be employed to implement embodiments of the present invention. In some embodiments, display 52 may comprise a touchscreen configured to accept inputs from medical professional 34, in addition to presenting image 50.

[0032] Additionally or alternatively, medical system 20 can use magnetic position sensing to determine position coordinates that indicate a location and an orientation of distal end 26 in a coordinate system 54 comprising an X-axis 56, a Y-axis 58 and a Z- axis 60. To implement magnetic based position sensing, control console 24 comprises a driver circuit 62 which drives field generators 64 to generate magnetic fields within the body of patient 36. Typically, field generators 64 comprise three orthogonally oriented coils, which are placed below the volume at known positions external to patient 36. Distal end 26 comprises a magnetic field sensor 66 (also referred to herein as a location sensor or a position sensor) that generates signals in response to the magnetic fields.

[0033] Although the medical system shown in Figure 1 uses magnetic- based sensing to measure a location of distal end 26, other position tracking techniques may be used (e.g., impedance-based sensors) . Magnetic position tracking techniques are described, for example, in U.S. Patents 5,391,199, 5,443,489, 6,788,967,

6,690,963, 5,558,091, 6,172,499 6,177,792, which is hereby incorporated by reference as if set forth herein this application and attached to the Appendix. Impedance-based position tracking techniques are described, for example, in U.S. Patents 5,983,126, 6,456,864 and 5,944,022, which is hereby incorporated by reference as if set forth herein this application and attached to the Appendix. The method of position sensing described hereinabove is implemented in the above-mentioned CARTO™ system and is described in detail in the patents cited above.

[0034] Control console 24 may also comprise an input/output (I/O) communications interface 68 that enables the control console to transfer signals from, and/or transfer signals to magnetic field sensor 66 and fluoroscopy unit 38. Based on signals received from magnetic field sensor 66 and/or fluoroscopy unit 38, processor 48 can generate image 50 that can comprise a map that shows the position of distal ends 26 in the patient's body. During the procedure, processor 48 can present the map to medical professional 34 on display 52, and store data representing the map in a memory 70. Memory 70 may comprise any suitable volatile and/or non volatile memory, such as random access memory or a hard disk drive.

[0035] Control console 24 may further comprise an inflation module 72 and a cryoablation module 74. As described in the description referencing Figure 2 hereinbelow, distal end 26 comprises an inflatable balloon that is configured to deliver cryoablation energy to tissue in heart 28. In some embodiments, inflation module 72 can deliver a refrigerant (described in more detail below) via apertures 106 into balloon 90 in order to inflate the balloon .

[0036] Cryoablation module 74 is configured to monitor and control ablation parameters by regulating delivery of a refrigerant to the balloon at distal end 26. Examples of refrigerants include, but are not limited to, liquid N ₂ O, Freon, Argon gas, CO ₂ gas, and near-critical N ₂ . In some embodiments, medical professional 34 can use one or more input devices 80 to manipulate image 50 and to control parameters for inflation module 72 and cryoablation module 74.

[0037] Processor 48 may comprise real-time noise reduction circuitry 76 typically configured as a field programmable gate array (FPGA) , followed by an analog-to-digital (A/D) electrocardiograph (ECG) signal conversion integrated circuit 78. The processor can pass the signal from A/D ECG circuit 78 to another processor and/or can be programmed to perform one or more algorithms disclosed herein, each of the one or more algorithms comprising steps described hereinbelow. The processor uses circuitry 76 and circuit 78 as well as features of modules which are described in more detail below, in order to perform the one or more algorithms.

[0038] Figure 2 is a schematic cross-sectional longitudinal view of distal end 26, in accordance with an embodiment of the present invention. Distal end 26 comprises a balloon 90 (also referred to herein as an expandable membrane) that is deployable through a lumen 122 at a distal end 124 of insertion tube 30. Balloon 90 comprises a proximal end 92 that is affixed to an outer tubular shaft 94. A distal end 96 is affixed to an inner tubular shaft 98, which is contained within the outer tubular shaft. Shafts 94 and 94 may also be referred to herein as tubular members 94 and 98.

[0039] Shafts 94 and 98 are both configured to extend from lumen 122 at the distal end of insertion tube 30. In the example shown in Figure 2, balloon 90 is shown in an inflated state, and is typically formed from bio-compatible material such as polyethylene terephthalate (PET), polyurethane, nylon, or silicone. For safety, distal end 26 may comprise a second balloon (not shown) that surrounds balloon 90 and is typically used to ensure a balloon rupture does not result in gas leakage into the patient. Balloon 90 is typically non-compliant, and medical professional 34 can control the diameter of the balloon (i.e., when inflated) by either extending or retracting inner tubular shaft 98.

[0040] Distal end 26 also comprises an injection tube 100 whose proximal end is coupled to cryoablation module 74 and whose distal end is coupled to an injection coil 102. Injection tube 100 is disposed along inner shaft 98, and injection coil 102 is wrapped around the inner shaft at distal end 96. Injection coil 102 comprises a plurality of outwardly facing apertures 106 so that the apertures are distributed radially (i.e., angularly) around inner shaft 98 and open into balloon 90. Apertures 106 are configured to deliver a refrigerant from injection tube 100 to the inside of balloon 90. In some embodiments, the refrigerant may comprise those refrigerants referred to above and/or a pressurized liquid coolant that changes state to a gas upon being expelled from apertures 106. In embodiments described herein, injection tube 100 and injection coil 102 may be referred to collectively as injection tube 100.

[0041] Distal end 26 further comprises a directional control tube

104 that is contained within outer shaft 94 and surrounds and is rotatable around inner shaft 98. In one embodiment, injection tube 100 is stationary with respect to the rotatable and translatable control tube 104. In an alternative embodiment, injection tube 100 is rotatable and translatable with respect to control tube 104, which is stationary. In yet a further embodiment, injection tube 100 and control tube 104 are both movable relative to each other.

[0042] In embodiments of the present invention, directional control tube 104 comprises a portion 108 along the length of the tube that is missing a predetermined arcuate wall portion of the control tube to allow the inside surface of the control tube 104 to be exposed. For brevity, this portion 108 will be referenced as semi- tubular section 108 (also referred to herein as a blocking element 108) that is configured to cover one or more apertures 106, thereby blocking or diverting exit of the refrigerant through the one or more of the apertures.

[0043] In addition to rotating around inner shaft 98, directional control tube 104 is configured to move longitudinally (i.e., back and forth) along the inner shaft, as indicated by a bidirectional arrow 110. In other words, directional control tube 104 can be advanced over injection tube 100 and injection coil 102. Medical professional 34 can use a rocker switch control 114 on handle 32 to control the longitudinal movement of directional control tube 104, and can use a rotatable knob control 116 on the handle to control the rotation of the directional control tube.

[0044] In some embodiments, processor 48 can determine a position (i.e., location and orientation) of blocking element 108 in coordinate system 54, and in response to the determined position, the processor can control, via an integrated motor (not shown) in handle 32, the rotation of directional control tube 104 around injection tube 100. In additional embodiments, processor 48 can control, using the integrated motor, the rotation of directional control tube 104 around injection tube 100 in response to signals received from control 116. In further embodiments, processor 48 can control the extension and retraction of directional control tube 104 in response to signals from control 114.

[0045] In some embodiments handle 32 may also comprise a visual indicator 118 (e.g., one or more LEDs or a small LED display) that processor 48 can manage to indicate an angle of rotation and/or the extension of blocking element 108 within balloon 90. Additionally or alternatively, processor 48 can present the rotation and extension information on display 52. In the configuration shown in Figure 2, handle 32 also comprises an ablation control button 112 that medical professional can press to control delivery of the refrigerant from cryoablation module 74 into injection tube 100.

[0046] In some embodiments, processor 48 can use signals from magnetic field sensor 66 to determine a location and/or an orientation of blocking element 108 (i.e., relative to injection tube 100 and/or injection coil 102) . Magnetic field sensor 66 can be in the form of a single-axis sensor as utilized in commonly owned US Patent No. 6,484,118, which is hereby incorporated by reference as if set forth herein this application and attached to the Appendix. In embodiments where medical system 20 uses impedance-based position tracking where location sensor 66 comprises an electrode, directional control tube 104 may comprise an additional electrode, and processor 48 can use signals from the electrodes to determine an orientation of blocking element 108. In yet another embodiment, a hybrid magnetic and impedance position sensing system can be utilized to sense the location of the balloon 90, injection tube 100, control tube 104 or any components of the distal portion of the catheter 26 relative to the patient anatomy. Such hybrid magnetic-impedance position sensing is shown and described in commonly-owned US Patent No. 7,536,218, which is hereby incorporated by reference as if set forth herein this application and attached to the Appendix.

[0047] Additionally or alternatively, blocking element 108 may comprise one or more markers 120 (e.g., a square) that is fluoroscopically opaque so as to be detected by fluoroscopy unit 38, so that processor 48 can indicate its position on display 52. In operation, medical professional 34 can use the location of marker 120 to determine the location of directional control tube 104 relative to injection coils 102 as well as the orientation of blocking element with respect to the anatomy of patient 36. [0048] In embodiments having a single marker 120 on blocking element 108, the marker may comprise any shape that is not bilaterally symmetric. In the example shown in Figure 2, marker 120 is in the shape of the letter "L", and medical professional 34 can determine the orientation (i.e., relative position) of blocking element 108 based on the presentation of the blocking element on display 52. In this example, if display 52 presents marker 120 as an "L" shape, then blocking element is anterior to injection coil 102. Likewise, if display 52 presents marker 120 as a backwards "L" shape, then blocking element is posterior to injection coil 102.

[0049] In embodiments having more than one markers 120, a first marker 120 can be disposed on blocking element 108 and a second marker 120 can be disposed on injection tube 100, thereby enabling medical professional 34 to determine an orientation of the blocking element based on the presentation of the markers on display 52. In some embodiments, the radiopaque marker on blocking element 108 may have a different shape from the marker 120 on injection tube 100 in order to allow for identification of the relative position of the injection tube 100 and the control tube 104 via both of the markers .

[0050] Figure 3 is a schematic longitudinal view of blocking element 108, in accordance with a first embodiment of the present invention. In the configuration shown in Figure 3, blocking element 108 comprises a single section having a common angle 130.

[0051] Figure 4 is a schematic longitudinal view of blocking element 108, in accordance with a second embodiment of the present invention. In the configuration shown in Figure 4, blocking element 108 comprises a first section 140 having a first blocking angle 146, a second section 142 having a second blocking angle 148 greater than the first angle, and a third section 144 having a third blocking angle 150 greater than the second angle. In this second embodiment, medical professional 34 can control the angle of spray of the refrigerant into balloon 90 by extending and retracting blocking element 108. Angle 150 in section 144 may block between 20 and 60 degrees, angle 148 in section 142 may block between 60 and 120 degrees, and angle 146 may block between 90 and 180 degrees.

[0052] When section 140 is extended over injection coil 102, the first section covers a first number of apertures 106, and the apertures can deliver the refrigerant into the balloon at a first spray angle. When section 142 is extended over injection coil 102, the second section covers a second number (less than the first number) of apertures 106, and the apertures can deliver the refrigerant into the balloon at a second spray angle greater than the first spray angle. When section 144 is extended over injection coil 102, the third section covers a third number (less than the second number) of apertures 106, and the apertures can deliver the refrigerant into the balloon at a third spray angle greater than the second spray angle.

[0053] While the configuration of blocking element 108 show in Figure 4 has three sections 140, 144 and 148, the blocking element comprising any plurality of sections is considered to be within the spirit and scope of the present invention. For example, greater numbers of sections may be used to allow for more choices in selection of a blocking angle by one skilled in the art. Additionally or alternatively, while the control tube 104 is described as translatable and rotatable with respect to injection tube 100 as a referential datum, it is within the scope of the invention to configure the injection tube 100 to be rotatable and translatable with respect to the control tube 104 as a referential datum. [0054] Figure 5 shows schematic cross-sectional latitudinal views of sections 140, 142 and 144 extended over a portion of injection coil 102, in accordance with an embodiment of the present invention. As shown in the figure, first section 140 covers three apertures 106 when extended over the portion of injection coil 102, second section 142 covers two apertures 106 when extended over the portion of injection coil 102, and third section 144 covers a single aperture 106 when extended over the portion of injection coil 102.

[0055] As illustrated in Figure 5, each section 140, 142, and 144 of semi-tubular element 108 has a respective, different, arcuate cross-section. Similarly, the single section of semi-tubular element 108 illustrated in Figure 3 has an arcuate cross-section.

[0056] Figure 6 is a flow diagram that schematically illustrates a method of performing a cryoablation procedure on tissue in heart 28, and Figure 7 is a schematic detail view of distal end 26 in a chamber 180 of the heart, in accordance with an embodiment of the present invention. As shown in Figure 7, chamber 180 is connected to pulmonary veins 184 by respective ostia 182.

[0057] In an identification step 160, medical professional 34 identifies a section of intracardiac tissue for cryoablation. In the example shown in Figure 7, the identified intracardiac tissue comprises a given ostium 182 connected to a given pulmonary vein 184.

[0058] In a selection step 162, medical professional 34 selects an area 190 of the identified tissue to deliver greater levels of cryoablation energy. In the example shown in Figure 7, the selected area may comprise the anterior wall of the given pulmonary vein. The posterior wall of the given pulmonary vein is thinner than the anterior wall and is proximal to esophagus 188. Therefore, delivering lower amounts of cryoablation energy to the posterior wall of the given pulmonary vein can protect tissue in the esophagus, which can be damaged by the cryoablation effect of refrigerant in the expandable membrane on tissues. In an alternative embodiment, processor 48 can perform selection step 162.

[0059] In an insertion step 164, medical professional 34 manipulates handle 32 in order to insert distal end 26 of probe 22 into cardiac chamber 180, and in an inflation step 166, the medical professional can inflate balloon 90. To inflate balloon 90, medical professional can use inflation module 72 to control the inflation pressure of balloon 90 in response to the size of the selected tissue .

[0060] While manipulating handle 32 to maneuver medical probe, processor 48 presents, on display 52, image 50 comprising a current location of balloon 90 in a presentation step 168. In some embodiments, processor 48 can generate and present image 50 based on signals received from fluoroscopy unit 38. Additionally or alternatively, processor 48 can generate and present image 50 based on signals received from magnetic field sensor 66.

[0061] In a positioning step 170, medical professional 34 manipulates handle 32 to position balloon 90 so that it presses against the identified ostium, and in a first cryoablation step 172, in response to medical professional pressing ablation button 112, processor 48 can instruct cryoablation module 74 to deliver the refrigerant to injection coil 102, which in turn delivers the refrigerant to cryoablate the identified ostial tissue. During step 172 (i.e., at the beginning of the cryoablation procedure), blocking element 108 may be retracted and is therefore proximal to injection coil 102, thereby enabling all the apertures in the injection coil to deliver the refrigerant to the balloon in an angularly symmetric manner, thereby delivering cryoablation energy to any ostial tissue in contact with the balloon.

[0062] In a deployment step 174, the medical professional manipulates controls 114 and 116 so that blocking element 108 extends over injection coil 102 and the apertures facing the selected region are exposed (i.e., not covered by the blocking element) . Finally, in a second cryoablation step 176, in response to medical professional pressing ablation button 112, cryoablation module 74 delivers the refrigerant to injection coil 102. Coil 102 delivers the refrigerant to deliver additional cryoablation energy the selected area 190, and the method ends.

[0063] As shown in Figure 7, when blocking element 108 is extended over injection coil 102, the blocking element covers one or more apertures 106 that are facing away from selected area 190. Therefore, blocking element 108 blocks or diverts any coolant being delivered to apertures 106 covered by the blocking element, and the apertures can direct delivery of the refrigerant toward selected area 190, as indicated by arrows 186. In Figure 7, callout 192 comprises a superior view of heart 28, and the orientation of blocking element 108 directs the refrigerant away from esophagus 188, as indicated by arrows 186.

[0064] It will be appreciated that the embodiments described above are cited by way of example, and that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not disclosed in the prior art. APPENDIX

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