Patent ID: 12226140

DETAILED DESCRIPTION

The devices, systems, and methods disclosed herein are for treating an area of tissue, such as performing pulmonary vein isolation, spot ablation, and/or linear ablation with a single treatment device. For example, a system is provided that includes a treatment device with a highly conformable balloon that is inflated at a constant pressure and that remains “soft” during use, which enhances balloon-tissue contact, treatment efficacy, and patient safety.

Before describing in detail exemplary embodiments that are in accordance with the disclosure, it is noted that components have been represented where appropriate by conventional symbols in drawings, showing only those specific details that are pertinent to understanding the embodiments of the disclosure so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

As used herein, relational terms, such as “first,” “second,” “top” and “bottom,” and the like, may be used solely to distinguish one entity or element from another entity or element without necessarily requiring or implying any physical or logical relationship or order between such entities or elements. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the concepts described herein. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and/or “including” when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

In embodiments described herein, the joining term, “in communication with” and the like, may be used to indicate electrical or data communication, which may be accomplished by physical contact, induction, electromagnetic radiation, radio signaling, infrared signaling or optical signaling, for example. One having ordinary skill in the art will appreciate that multiple components may interoperate and modifications and variations are possible of achieving the electrical and data communication.

Referring now to the drawing figures in which like reference designations refer to like elements, an embodiment of a medical system is shown inFIG.1, generally designated as “10.” The device and system components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. Moreover, while certain embodiments or figures described herein may illustrate features not expressly indicated on other figures or embodiments, it is understood that the features and components of the system and devices disclosed herein are not necessarily exclusive of each other and may be included in a variety of different combinations or configurations without departing from the scope and spirit of the invention.

One embodiment of the medical system10may generally include a treatment device12in communication with a control unit14. The treatment device12may include one or more diagnostic or treatment elements16for energetic or other therapeutic interaction between the treatment device12and a treatment site (which may also be referred to as an area of targeted tissue). The treatment element(s)16may deliver, for example, cryogenic therapy, and may further be configured to deliver radiofrequency energy, or otherwise for energetic transfer with a tissue area in proximity to the area(s) of targeted tissue, including cardiac tissue. In particular, the one or more treatment elements16may be configured to reduce the temperature of adjacent tissue in order to perform cryotreatment and/or cryoablation. For example, the treatment element(s)16may include one or more balloons18(as shown inFIG.1) within which a cryogenic coolant may be circulated in order to reduce the temperature of the balloon. As is discussed in more detail below, the balloon(s)18are configured to be “soft” (that is, easily deformable and/or conformable to an area of targeted tissue) when fully inflated. Additionally, the treatment element(s)16may include other thermally and/or electrically-conductive components, such as one or more electrodes in communication with the control unit14.

In one embodiment, the treatment device12includes an elongate body20sized and configured to be passable through a patient's vasculature and/or positionable proximate to a tissue region for diagnosis or treatment, such as a catheter, sheath, or intravascular introducer. For example, the elongate body20may have an outer diameter of 11 Fr. The elongate body20defines a longitudinal axis22, a proximal portion24, and a distal portion26, and may further include one or more lumens disposed within the elongate body20that provide mechanical, electrical, and/or fluid communication between the proximal portion24of the elongate body20and the distal portion26of the elongate body20. In currently known devices, the elongate body28may include a central lumen30, an outer wall32with a plurality of smaller lumens34therein that extend into the central lumen30, a fluid delivery conduit36, and a guidewire lumen37(for example, as shown inFIG.2). The area of the central lumen30between the outer wall32(and plurality of smaller lumens34) and the guidewire lumen37defines the fluid return conduit. However, extension of the plurality of smaller lumens34into the central lumen30restricts the fluid return conduit. In contrast, the treatment device12disclosed herein does not include the plurality of smaller lumens34, and therefore provides a larger fluid return conduit that is capable of more rapidly evacuating fluid from the balloon18. For example, as shown inFIG.3, the elongate body20includes a central lumen38, an outer wall40, a fluid delivery conduit42, and, optionally, a guidewire lumen44. The area of the central lumen38between the outer wall40and the guidewire lumen44defines the fluid return conduit46. In one embodiment, the configuration shown inFIG.3can provide an increase of over 30% in the volume of the fluid return conduit as compared to currently known designs. Additionally, the larger volume of the fluid return conduit lowers the pressure drop within the elongate body20.

In one embodiment, the treatment device12further includes a shaft48that is slidably disposed within the elongate body20. For example, the shaft48is a flexible linear shaft that is longitudinally movable within a lumen (for example, the central lumen38or the guidewire lumen44) of the elongate body20. Further, the shaft48includes a proximal portion (not shown) and a distal portion50with a distal tip52. Movement of the shaft48may affect the shape and configuration of the balloon18. For example, the shaft48may be fully advanced when the balloon18is deflated and in a delivery (or first) configuration wherein the balloon18has a minimum diameter suitable, for example, for retraction of the treatment device12within a sheath for delivery to and removal from the treatment site. Conversely, when the balloon18is inflated and in a treatment (or second) configuration, the shaft48may be advanced or retracted over a distance that affects the size and configuration of the inflated balloon18, as is discussed in greater detail herein. Further, the shaft48may include a guidewire lumen through which a sensing device, mapping device, guidewire, or other system component may be located and extended from the distal end of the treatment device12.

As noted above, in one embodiment the one or more treatment elements16includes a single expandable element, such as the balloon18shown in the figures. However, it will be understood that the treatment device12may include more than one treatment element16, including expandable and/or non-expandable treatment elements (for example, an interior balloon surrounded by an exterior balloon), electrodes, or other suitable energy exchange structures or components. In the embodiment shown inFIG.1, the treatment element16includes a balloon18, such as a cryoballoon, that has a proximal neck54that is coupled to the elongate body distal portion26and a distal neck56that is coupled to the shaft distal portion50. In one embodiment, the distal neck56is coupled to the shaft distal tip52. The proximal54and distal56necks of the balloon18may be coupled to the elongate body20and shaft48, respectively, using any suitable means, such as with adhesives, chemical bonding, laser welding, with one or more mechanical coupling elements, or the like. Further, the balloon18is a compliant or highly compliant balloon composed of one or more materials such as polyurethane, polyolefin copolymer (POC), or other material that allows the balloon to be “soft” (that is, easily deformable and/or conformable to an area of targeted tissue) when fully inflated. This compliant or highly compliant balloon18is referred to herein as a “highly conformable balloon.” Additionally, the balloon18may be inflatable to a first outer diameter (for example, of approximately 23 mm) and further inflatable to a second outer diameter (for example, of approximately 36 mm), at an inflation pressure of between 0.2 psig and 3.0 psig, which pressure is also the pressure of the balloon18when the balloon18is used for an ablation procedure. In contrast, currently known balloons are inflated at a pressure of approximately 2 psig, with an ablation pressure of 17.5 psig.

The treatment device12includes one or more nozzles, orifices, or other fluid delivery elements58for delivering fluid to the interior chamber60of the balloon18. During operation, coolant may flow from a coolant supply reservoir62through a fluid delivery conduit42within the elongate body20to the distal portion26, where the coolant may then enter the interior chamber60of the balloon18, such as through the one or more fluid delivery elements58, where the coolant may expand to cool the balloon18. Expanded coolant may then pass from the interior chamber60of the balloon18to a coolant recovery reservoir64and/or scavenging system through the fluid return conduit. Further, as is discussed in greater detail below, the size of the balloon18when fully inflated may be chosen by the user based on various factors such as the patient's anatomy and pulmonary vein ostium diameter, and may also be independent of the flow rate of and fluid pressure generated by delivery of the coolant to the balloon18.

The treatment device12further includes a handle66coupled to the elongate body proximal portion24. The handle66includes one or more steering or deflection components for manipulating the elongate body20, the one or more treatment elements16, and/or additional components of the treatment device12. In one embodiment, the handle66includes an actuator element or push button68that is in direct mechanical communication with the proximal portion of the shaft48. In one embodiment, the push button68is a slide mechanism that is longitudinal movable within or relative to the handle66. In this embodiment, movement or actuation (for example, longitudinal movement) of the push button68exerts a direct force on the shaft48and causes the shaft48to likewise slide, or move longitudinally, within the elongate body20. As the distal neck56of the balloon18is coupled to the distal portion50of the shaft48, this longitudinal movement of the shaft48caused by engagement of the push button68will cause a change in the shape and/or size of the balloon18, as is discussed in greater detail below. Further, the handle66is fixedly coupled to the elongate body proximal portion24and the push button68is mechanically coupled to the shaft48; however, in one embodiment, the push button68and shaft48are freely movable with respect to the handle66and elongate body20(even though the push button68may be at least partially disposed within the handle), thereby allowing the push button68and shaft48to move based on the balloon pressure without actuation or control by the user. That is, when the push button68is not engaged by the user, both the push button68and the shaft48are, in one embodiment, freely longitudinally movable relative to the handle66and the elongate body20, based on the force exerted on the shaft distal portion50by the inflation pressure of the balloon18. The handle66also includes connectors that are matable directly or indirectly to the control unit14to establish communication between the one or more components of the treatment device12with one or more components of the control unit14, as described herein.

In one embodiment, the treatment device12and/or the control unit14includes one or more sensors. In one non-limiting example, the treatment device12includes one or more pressure sensors70on and/or within the balloon18. These pressure sensors70are configured to record pressure waves from or through the balloon18, such as pressure waves generated by the beating of the patient's heart. As is shown inFIG.21, the magnitude or value of the pressure waves recorded by the sensor(s)70may be used to determine whether the balloon18is completely occluding a vessel, such as a pulmonary vein ostium. As the balloon18is used at low pressures (for example, <6 psig), it is possible to accurately monitor the patient's heartbeat with the pressure sensor(s)70. As the vessel is occluded, the pressure signal (that is, the pressure waves generated by the heartbeat) becomes less pronounced, indirectly proportional to the quality of occlusion of the vessel. In one non-limiting example, a relatively flat signal may indicate adequate occlusion.

Additionally or alternatively, one or more sensors may be used to evaluate inflation and/or configuration of the balloon18. For example, in one embodiment, the control unit14includes a pressure sensor72that is in fluid communication with a Pitot tube74in the treatment device12. The Pitot tube74may be composed of polyimide or similar material(s) and may have an outer diameter of approximately 0.030 in. In one embodiment, the Pitot tube74includes a distal end76that is at least partially located within the interior chamber60of the balloon18and a proximal end77, opposite the distal end76, that contains, is coupled to, or otherwise in communication with the pressure sensor72. The Pitot tube distal end76includes an opening that is exposed to fluid circulating within the interior chamber60. The Pitot tube74is used to measure the pressure at the stagnation point (Pstag), which is the pressure within the interior chamber60proximate the opening at the distal end76(for example, as shown inFIG.4), based on the dynamic pressure (Pdynamic) and static pressure (Pstatic) of the fluid within the interior chamber60:
Pstag=Pstatic+Pdynamic(1)
where
Pdynamic=(ρ*v2)/2  (2)
As is discussed in greater detail below, the velocity of fluid (for example, coolant) circulating within the balloon18is relatively low, especially near the opening at the Pitot tube distal end76.
Therefore:
Pdynamic=0  (3)
and
Pstag=Pstatic(4)
Thus, the fluid pressure measured by the Pitot tube74at the stagnation point (Pstag) can be used to directly determine the static pressure (Pstatic) of the fluid within the interior chamber60(that is, the balloon pressure). However, it will be understood that a Pitot-static tube may be used instead of a Pitot tube. Additionally or alternatively, other components may be used to determine pressure, such as a piezo-resistive MEMS, fiber optic system based on the Fabry-Perot principal, capacitive resistors, thermistors, and the like. Determining the pressure within the interior chamber60allows the user and/or the control unit14to set the balloon18diameter based on the determined pressure, monitor the balloon18pressure to prevent over pressurization, and/or monitor a push force on the treatment device12or portion thereof when in use.

In one embodiment, the coolant supply reservoir62, coolant recovery reservoir64, and/or one or more alternative energy sources to supply the selected modality of treatment to the treatment element(s)16(such as, for example, a radiofrequency generator, ultrasound generator, light sources, or the like) as well as various control mechanisms for the medical system10are housed in the control unit14. For example, if a fluid other than a coolant is used to inflate the balloon18, the control unit14may also include an inflation fluid reservoir. The control unit14also includes one or more computers78having one or more displays80and processing circuitry82and/or software modules. The processing circuitry82may be programmed or programmable to execute the automated operation and performance of the features, sequences, or procedures described herein. As a non-limiting example, the processing circuitry82includes a memory and a processor, the memory in communication with the processor and having instructions that, when executed by the processor, configure the processor to perform one or more system functions. For example, the processing circuitry82may be configured to receive electrical signals from the pressure sensor(s)70,72to evaluate vessel occlusion by the balloon18and/or to determine fluid flow rates and/or balloon pressure. It will be understood that one or more system components may be physically located outside of the control unit14; however, any system components that are not part of the treatment device12may be referred to herein as being located within the control unit14for simplicity. In one embodiment, the control unit14(for example, the processing circuitry82) is configured to compare one or more determined pressure values (Pstagand/or Pstatic, for example) to a threshold pressure to determine if the balloon18is being maintained at a pressure of between 0.2 psig and 3.0 psig. Additionally or alternatively, the control unit14is configured to compare determined pressure values (Pstagand/or Pstatic, for example) to each other during the procedure. For example, the control unit14may be configured to compare a determined pressure value recorded during the inflation phase to a determined pressure value recorded during the ablation phase.

Referring now toFIGS.5-20, inflation of the balloon18will now be discussed in greater detail. In one embodiment, the balloon18is a highly conformable balloon that may be inflated to a variety of outer diameters, while maintaining a high degree of flexibility or conformity to the contour of an object (such as a tissue surface) with which the balloon18is in contact. For example, when the balloon18is inflated to have an at least substantially round first configuration, the balloon18may be inflated to a first outer diameter OD1, such as approximately 23 mm (±2 mm) (as shown inFIG.6). If desired, the balloon18may be further inflated to a larger second outer diameter OD2, such as approximately 36 mm (±2 mm) (as shown inFIG.7). Of course, the balloon18may be inflated to any outer diameter between the first and second outer diameters, depending on the procedure, patient's anatomy, user's preference, or the like. Regardless of the outer diameter of the balloon18, however, the balloon18remains highly compliant. The fluid, such as coolant, used to inflate the balloon18may be delivered to the interior chamber60at a pressure of between 0.2 psig and 3.0 psig. The medical system10may further include one or more flow control valves in fluid flow pathways of the medical system10and a vacuum pump or vacuum source84to remove fluid from the balloon interior chamber60. For example, the medical system10(for example, the control unit14) may include a flow control valve86in communication with the fluid delivery conduit42and a pressure control valve88in communication with the fluid return conduit46(for example, as shown inFIG.5).

In one embodiment, the push button68and shaft48is freely movable with respect to the handle66and the elongate body20. As the balloon18inflates, the shaft48is free to move and takes its position based on the differential pressure between both sides of the balloon18. As the outer diameter of the balloon18increases with pressure, the balloon18length also increases, as movement (in this case, movement in a proximal-to-distal direction) of the shaft48is not constrained, as in currently known devices.

A comparison of balloon diameter and inflation pressure between a balloon18of the present disclosure and two currently known balloon devices is shown inFIG.8. The curve90for the balloon18of the present disclosure shows that inflation of the balloon even at low inflation pressures (for example, up to 3.0 psig) results in a rapid increase in the balloon outer diameter. In contrast, the curves92,94for currently known balloon devices show a much slower increase in balloon outer diameter with increase in inflation pressure.FIG.9shows a chart of tissue contact surface area on the balloon18versus inflation pressure. In some embodiments, a lower inflation pressure results in a larger tissue contact surface area.

Referring now toFIGS.10-27, use of the treatment device12is discussed in greater detail.FIGS.10and11show use of the distal face of a currently known balloon96and the balloon18of the present disclosure, respectively, to ablate an area of targeted tissue. As discussed above, the balloon18of the present disclosure, even when inflated, is highly conformable (that is, the balloon18is “soft”). Consequently, pushing the balloon18against an area of targeted tissue, even when pushed gently, causes the balloon18to deform such that a larger surface area of the balloon18is in contact with the area of targeted tissue.FIG.10shows a front view of a currently known balloon96(that is, the distal face98), with an exemplary tissue contact area100illustrated.FIG.11shows a front view of the balloon18(that is, the distal face102) of the present disclosure, with an exemplary tissue contact area104illustrated. The comparison ofFIGS.10and11shows that the high compliance or softness of the balloon18results in a larger, more uniform tissue contact surface, which, in turn, results in more efficient lesion formation. When in the balloon18is in the at least substantially round first configuration, the treatment device12may be used for a variety of procedures, such as pulmonary vein isolation. Although the treatment device12is shown in the figures as having a shaft distal tip52that protrudes beyond the distal face102of the balloon18, it will be understood that the treatment device12may alternatively have an atraumatic, substantially continuous distal face102, without the protruding shaft distal tip52.

This same principal is also applicable when a lateral surface of the balloon18is used to ablate an area of targeted tissue, which is shown inFIGS.12and13. For example,FIG.12shows a side view of an inflated highly conformable balloon18when the lateral surface106of the balloon18is in contact with an area of targeted tissue108, and illustrates that the balloon18, when pushed against the area of targeted tissue108, flattens to create a larger, more uniform tissue contact area104. The lateral surface106of the balloon18is shown inFIG.13, with an exemplary tissue contact area104on the lateral surface106when the balloon18is in contact with an area of targeted tissue illustrated.

FIGS.11-13show use of the balloon18when the balloon is in the at least substantially round first configuration. For example, the balloon18may be inflated to be spherical, ovate, obovate, ellipsoid, or any other shape in which the proximal54and distal56necks of the balloon18are outside of the interior chamber60. In contrast,FIGS.14-17show use of the lateral surface106of the balloon18to ablate an area of targeted tissue108when the balloon18is in an at least substantially toroidal second configuration. In this configuration, the balloon18may be positioned against the area of targeted tissue108such that the tissue contact area104is located around the equator or outer circumference110of the balloon18. When the balloon18is in the at least substantially toroidal second configuration, the treatment device12may be used to, for example, ablate rotors (rotating areas of aberrant electrical currents) and/or to create spot lesions in the area of targeted tissue.

In one embodiment, the balloon18is transitioned from the at least substantially round first configuration to the at least substantially toroidal second configuration by engagement with or actuation of the push button68, which moves the shaft48within the elongate body20in a distal-to-proximal direction, resulting in inversion of the proximal54and distal56necks of the balloon18into the interior chamber60(as shown inFIGS.14-17). In an embodiment in which the fluid delivery element(s)58are coupled to, located within, or otherwise associated with the shaft48, retraction of the shaft48also brings the fluid delivery element(s)58toward the equator110of the balloon18to focus the cooling effect of circulation of coolant within the interior chamber60toward the equator110, thus forming a lateral surface for efficient tissue ablation. In contrast, the distal face98of the balloon18may be less suited for ablating the area of targeted tissue, as the tissue contact area104on the distal face102ofFIG.17shows.

FIGS.18-20show use of the lateral surface106of the balloon18to ablate an area of targeted tissue108when the balloon18is in an at elongated third configuration. In one embodiment, the balloon18is initially in a delivery configuration in which the balloon18is uninflated (as shown inFIG.18). Once proximate the area of targeted tissue, the balloon18is inflated only partially or not inflated at all (that is, inflation pressure is below the arterial pressure) and the shaft48is extended within the elongate body20in a proximal-to-distal direction (for example, by actuation of the push button68by the user) from the initial position to elongate the balloon18and create a relatively large tissue contact area104when the lateral surface106is in contact with the area of targeted tissue108(for example, as shown inFIGS.19and20). In this configuration, the balloon18may be used to create linear, at least substantially linear, or elongated lesions (for example, when creating a mitral isthmus isolation line). As the circulation (flow rate) of coolant within the interior chamber60is controllable independently of the inflation pressure (flow volume through the delivery and return conduits and/or strength of the vacuum source), the balloon18may be used to ablate the area of targeted tissue even when in a most deflated or partially inflated state.

The treatment device12with the highly compliant balloon18disclosed herein may also be used to safely occlude a vessel, such as when performing pulmonary vein isolation, without causing the distal end of the treatment device12(for example, the shaft distal tip52and distal portion of the balloon18) from traveling too far into the vessel. The deeper into the vessel the balloon travels, the higher the risk of tamponade, aneurysm, and/or phrenic nerve injury.FIGS.22-24show a treatment device12having a highly compliant balloon18used to occlude a vessel111andFIG.25shows a treatment device112having a balloon96used to occlude a vessel111.FIG.26shows a chart comparing the depth into the vessel111the balloon18,96distal end may travel as a function of force, with lines114,116,118, and120representing the scenarios ofFIGS.22-25, respectively. Current perception in the art is that a compliant balloon inflated at a low pressure would tend to travel too far into the vessel during occlusion. However, the treatment device12of the present disclosure does not present this problem. As the shaft48is freely movable when the push button68is not engaged by the user, the axial force provided by the user at the handle66during occlusion is not transferred, or is transferred by only a small degree, to the shaft48(and shaft distal tip52). Instead, axial force provided by the user at the handle66will be transmitted through the elongate body20and, consequently, to the rear of the balloon18. This causes the balloon to increase in diameter and, as a result, prevents the balloon18from traveling into the vessel111to an unacceptable or unsafe depth.

This phenomenon may be analogized to moving a rope through a hole: it may be very difficult to push the rope through the hole, but very easy to pull the rope through the hole.FIG.22shows a first method of occluding a vessel111with a highly conformable balloon18in which the axial force provided by the user is transmitted through the shaft48only (similar to pulling the “rope” through the “hole”), as depicted by the arrow. For example, the balloon18is inflated to an outer diameter of 28 mm at 1.0 psig.FIG.23shows a second method of occluding a vessel111with a highly conformable balloon18in which the axial force provided by the user is transmitted through the shaft48(similar to pulling the “rope” through the “hole”) and is transmitted through the elongate body20(similar to pushing the “rope” through the “hole”), as depicted by the arrows. For example, the balloon18is inflated to an outer diameter of 28 mm at 1.0 psig.FIG.24shows a third method of occluding a vessel111with a highly conformable balloon18in which the axial force provided by the user is transmitted through the elongate body20only (similar to pushing the “rope” through the “hole”), as depicted by the arrow. For example, the balloon18is inflated to an outer diameter of 28 mm at 1.0 psig. Finally,FIG.25shows a method of occluding a vessel111with a currently known (that is, not highly conformable) balloon96in which the axial force provided by the user is transmitted through the elongate body28and/or the shaft122. As the balloon96is more rigidly inflated, transmitting axial force through the elongate body28versus the shaft122may have the same, or approximately the same, effect on the balloon96. Consequently, arrows are shown inFIG.25to depict axial force transmitted to the elongate body28and/or the shaft122. For example, the balloon96is inflated to an outer diameter of 28 mm at a pressure of 18 psig.

As can be seen byFIGS.22-25and the accompanying chart inFIG.26, transferring the axial force generated by the user on the handle66to the shaft48effectively “pulls” the highly conformable balloon18into the vessel111by proximal-to-distal movement of the shaft48(which elongates and reduces the outer diameter of the balloon18, making it easier for the balloon18to travel into the vessel). However, transferring the axial force generated by the user on the handle66to the elongate body20, such as by decoupling the shaft48from the push button68(for example, to allow free movement of the shaft48with respect to the handle66and elongate body20) causes the elongate body20to push against the rear of the balloon18and, as a result, increase the outer diameter of the balloon18. This increase in outer diameter prevents the balloon18from traveling into the vessel111to an undesired depth. Further, occlusion of the vessel by the highly conformable balloon18shown inFIG.24provides nearly the same result as occlusion of a vessel by a currently known balloon96that is not highly conformable. Therefore, the user retains the benefits discussed herein of using the highly conformable balloon18to perform the medical procedure without the potential for patient injury currently expected when using balloons inflated to a low pressure.

Referring now toFIG.27, an exemplary method of using a medical system10including a treatment device12with a highly conformable balloon18is shown. In an exemplary first step130, the user navigates the treatment device12to a location proximate an area of targeted tissue108. In one embodiment, the area of targeted tissue108may be a pulmonary vein ostium, a location on the left atrial wall, or any other suitable location within the patient's body. The control unit14(for example, the processing circuitry82) is then used to automatically, semi-automatically, and/or manually control inflation and use of the balloon18to perform an ablation procedure. For example, in an exemplary second step132, the user selects a desired size and/or outer diameter of the balloon18using a touch-screen display80and/or other user input device of the medical system10. Then, commencing the inflation phase, the control unit14manipulates or otherwise controls the flow control valve86in the fluid delivery conduit42, the pressure control valve88in the fluid return conduit46, and/or other valves in the fluid flow pathway(s) of the medical system10to provide a continuous flow of fluid to and from the balloon18to inflate the balloon18to the desired size and/or outer diameter (for example, to an outer diameter selected by the user). In one embodiment, the control unit14manipulates flow control valve86to adjust or control the flow, delivery, and circulation of the coolant to and within the balloon18when the treatment device12is communication with the control unit14and the control unit14manipulates pressure control valve88to control the pressure of expansion in the balloon18as measured by the Pitot tube74(or other pressure sensor) in the balloon18. Optionally, if a currently known treatment device is in communication with the control unit14, the control unit14may be configured to manipulate the flow control valve86to control the vacuum level based on a pressure measured at PT5 (shown inFIG.5) to reproduce the vacuum level of previous control unit generation(s). In an exemplary third step134, the user may also manipulate the push button68in the handle66to move the shaft48and adjust the shape and configuration of the balloon18during the inflation phase. For example, the shaft48may be advanced in a proximal-to-distal direction to elongate the balloon18(such as to create linear lesions) or the shaft48may be retracted in a distal-to-proximal direction to transition the balloon18into an at least substantially toroidal configuration (such as to create spot lesions or ablate rotors). However, it will be understood that the user may instead not engage the push button68and, instead, the shaft48may be allowed free movement within the elongate body20during the inflation phase (for example, when performing a pulmonary vein isolation procedure). In one embodiment, the balloon18is in fluid communication with the vacuum pump or vacuum source84, and is inflated at a constant inflation pressure of between 0.2 psig and 3.0 psig. In one embodiment, the balloon18is inflated using coolant delivered to the interior chamber60at a flow rate of approximately 1500 sccm (±500 sccm). For example, the coolant flow may be adjusted to 1500 sccm (±500 sccm) with the flow control valve86and the balloon18pressure may be set to between 0.2 psig and 3.0 psig by adjusting the pressure control valve88. Alternatively, a fixed amount of coolant may be delivered to the balloon18to increase the pressure within the balloon18to a target or desired pressure, such as by automatic, semi-automatic, or manual manipulation of the flow control valve86, and the pressure control valve88may be manipulated (for example, automatically or semi-automatically by the control unit14, or manually by the user) to help maintain or stabilize the pressure within the balloon at the target pressure. In one embodiment, once the target balloon pressure is achieved, the control valves86,88may be closed (for example, automatically or semi-automatically by the control unit14, or manually by the user) to stop the flow of coolant to and from the balloon18.

Once the balloon18is inflated and in a desired configuration, the control unit14automatically or semi-automatically initiate the ablation phase and regulate the control valves86,88(and/or the user may manually regulate the control valves86,88) in an exemplary fourth step136to maintain the balloon18at a relatively low ablation pressure. In one embodiment, the control unit14determines that the balloon18has reached the desired inflation size based on pressure measurements from the pressure sensor(s)70,72and automatically initiate ablation phase. In another embodiment, the control unit14determines that the balloon18has reached the desired inflation size based on pressure measurements from the pressure sensor(s)70,72and prompts the user to confirm and manually initiate the ablation phase. Once the ablation phase is initiated, no further adjustments to the size, shape, and/or configuration of the balloon18may be permitted. In one embodiment, the control unit14(for example, the processing circuitry82includes software with which the user may interact to lock, or prevent further modifications to, the balloon size, shape, and/or configuration.

In an exemplary fifth step138, the user may position the treatment device12such that the balloon18is in contact with the area of targeted tissue. In one embodiment, the balloon18is used to ablate tissue with a constant pressure of between 0.2 psig and 3.0 psig, the same pressure as the inflation pressure, which is in contrast to a required inflation pressure of approximately 17.5 psig in currently known devices. This relatively low pressure allows the balloon18to be highly conformable and very flexible during use. In one embodiment, the balloon18is used to perform a pulmonary vein isolation and axial force exerted by the user at the handle66to enhance contact tissue contact with, and occlusion by, the balloon18, is transferred through the elongate body20. This, in turn, exerts an axial force on the rear of the balloon18and increases the balloon outer diameter, which prevents the balloon18from traveling too deeply into the pulmonary vein. Although positioning the balloon18to be in contact with the area of targeted tissue is described as being the fifth step138, it will be understood that this step may occur before, during, or after the inflation phase.

Further, in an exemplary sixth step140, the control unit14may continuously monitor pressure measurements from the pressure sensor(s)70,72during the inflation phase and the ablation phase in a feedback loop to ensure the balloon18remains at the predetermined size, shape, and/or configuration, that the balloon18does not become over-pressurized, and/or to monitor a push force exerted on the handle66and/or elongate body20during use. If the control unit14determines adjustment in the coolant flow and/or balloon pressure is required (for example, based on the user's initial balloon size specifications), the control unit14automatically adjusts the control valve(s)86,88, vacuum pump or vacuum source84, and/or other system components10as necessary to bring balloon18pressure back to within the range of 0.2 psig to 3.0 psig. Alternatively, the control unit14and/or the user may discontinue the delivery of coolant to the balloon18if the pressure measurements indicate a system and/or balloon failure. As the balloon is inflated and used to ablate an area of targeted tissue while the balloon18is in communication with the vacuum pump or vacuum source84(that is, while the balloon18is under a vacuum), the flow rate of the coolant used to cool the balloon18and the balloon pressure may be controlled independently by the control unit14. Put another way, the control unit14may maintain the balloon at a pressure of between 0.2 psig and 3.0 psig, regardless of the flow rate of coolant within the balloon18. However, flow rate may be adjusted. For example, when the balloon18is in the elongated third configuration (as shown inFIGS.18-20), a lower coolant flow rate may be needed or desired than when the balloon18is in an expanded configuration (for example, as shown inFIGS.10-17). In one embodiment, the flow rate may be adjusted or determined automatically or semi-automatically by the control unit14based on the selected inflation pressure of the balloon18. Although monitoring pressure measurements is described as being the sixth step140, it will be understood that this step may occur at any time during the procedure, in discrete steps or continuously throughout the procedure (for example, as shown inFIG.27).

In an exemplary seventh step142, the deflation phase is initiated (for example, the flow of coolant is discontinued or reduced) and the balloon18is transitioned to the delivery configuration for safe removal from the patient's body. Optionally, the balloon18may be allowed to thaw prior to removal to prevent injury when removing a balloon that is cryoadhered to the area of target tissue.

It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings without departing from the scope and spirit of the invention, which is limited only by the following claims.