Patent Publication Number: US-2021177505-A1

Title: Pulmonary vein isolation balloon catheter

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional application No. 62/578,178, filed 27 Oct. 2018, which is hereby incorporated by reference as though fully set forth herein. 
    
    
     BACKGROUND 
     a. Field 
     The instant disclosure relates to catheters, in particular catheters for conducting diagnostics or ablation therapy within a heart. In one embodiment, the instant disclosure relates to a catheter for treating cardiac arrhythmias by ablating in the vicinity of pulmonary venous tissue. 
     b. Background Art 
     The human heart routinely experiences electrical currents traversing its many surfaces and ventricles, including the endocardial chamber. Just prior to each heart contraction, the heart depolarizes and repolarizes, as electrical currents spread across the heart and throughout the body. In healthy hearts, the surfaces and ventricles of the heart will experience an orderly progression of depolarization waves. In unhealthy hearts, such as those experiencing atrial arrhythmia, including for example, ectopic atrial tachycardia, atrial fibrillation, and atrial flutter, the progression of the depolarization wave becomes chaotic. Arrhythmias may persist as a result of scar tissue or other obstacles to rapid and uniform depolarization. These obstacles may cause depolarization waves to electrically circulate through some parts of the heart more than once. Atrial arrhythmia can create a variety of dangerous conditions, including irregular heart rates, loss of synchronous atrioventricular contractions, and blood flow stasis. All of these conditions have been associated with a variety of ailments, including death. 
     Catheters are used in a variety of diagnostic and/or therapeutic medical procedures to correct conditions such as atrial arrhythmia, including for example, ectopic atrial tachycardia, atrial fibrillation, and atrial flutter. 
     Typically in a procedure, a catheter is manipulated through a patient&#39;s vasculature to, for example, a patient&#39;s heart, and carries one or more electrodes which may be used for mapping, ablation, diagnosis, or other treatments. Where an ablation therapy is desired to alleviate symptoms including atrial arrhythmia, an ablation catheter imparts ablative energy to cardiac tissue to create a lesion in the cardiac tissue. The lesioned tissue is less capable of conducting electrical signals, thereby disrupting undesirable electrical pathways and limiting or preventing stray electrical signals that lead to arrhythmias. The ablation catheter may utilize ablative energy including, for example, radio frequency (RF), cryoablation, laser, chemical, and high-intensity focused ultrasound. 
     The foregoing discussion is intended only to illustrate the present field and should not be taken as a disavowal of claim scope. 
     BRIEF SUMMARY 
     The instant disclosure relates to electrophysiology catheters for conducting diagnostics or tissue ablation within a heart. In particular, the instant disclosure relates to an electrophysiology catheter that either conforms to a shape of a pulmonary vein or deforms the tissue to the balloon shape for therapy of cardiac arrhythmias and produces a consistent tissue ablation line along a length and circumference of the pulmonary venous tissue. 
     Aspects of the present disclosure are directed to an elongate medical device having a device longitudinal axis and a device distal region, the medical device comprising a balloon at the device distal region and having a balloon longitudinal axis, the balloon comprising a balloon inflatable portion with a first length that is configured to transition from a deflated state to an inflated state and includes a portion of the balloon proximal portion and a portion of the balloon distal portion, a balloon proximal portion with a second length, a balloon distal portion with a third length, wherein, in the inflated state, the balloon is symmetrical about the balloon longitudinal axis and a plan view of the balloon comprises a first profile shape with a second length and a second profile shape with a third length, and wherein the balloon distal portion comprising the second profile shape comprises a tissue contacting surface where a substantial portion of the tissue contacting surface is concave. 
     In one exemplary embodiment of the present disclosure, a system for treating atrial fibrillation is taught. The system comprises a balloon delivery catheter including proximal and distal ends; and an ablation balloon comprising a first section, a second section, a third section, and an inflatable section that comprises the second section and a portion of the first section and a portion of the third section, where the ablation balloon is coupled to the distal end of the balloon delivery catheter, wherein the first section has a first profile shape, the third section with a second profile shape is a portion of the third section is configured to engage with an ostium of a pulmonary vein for aligning a longitudinal axis of the ablation balloon with a longitudinal axis of the pulmonary vein, and the second section couples the first and third sections of the ablation balloon, with a varying circumference, and wherein at least a portion of one of the second section and third section of the ablation balloon is configured, when the inflatable section is inflated, to engage with an antrum of the pulmonary vein along an uninterrupted length and circumference, and deliver a uniform ablation therapy to the pulmonary vein antrum. 
     In another embodiment of the present disclosure, a balloon catheter is disclosed for pulmonary vein isolation. The balloon catheter including a catheter shaft configured to deploy an ablation balloon into a pulmonary vein, the ablation balloon coupled to a distal end of the catheter shaft, and configured to deploy from an undeployed configuration to a deployed configuration having a concave tissue contacting surface, engage, by a portion the concave tissue contacting surface, a tissue wall of the pulmonary vein along an uninterrupted length and circumference of an antrum and ostia of the pulmonary vein, and wherein the ablation balloon is configured to deliver a uniform ablation therapy to the antrum of the pulmonary vein engaged by the portion of the concave tissue contacting surface of the ablation balloon. 
     In yet another embodiment of the present disclosure, an expandable medical device is disclosed for pulmonary vein isolation. The expandable medical device comprising a balloon that is configured to transition from a deflated state to an inflated state, wherein when the balloon is in the inflated state, the balloon comprises a first profile shape on a proximal portion and a second profile shape on a distal portion, where the balloon is configured to be coupled with an elongated medical device and the second profile shape is a concave shape. 
     The foregoing and other aspects, features, details, utilities, and advantages of the present disclosure will be apparent from reading the following description and claims, and from reviewing the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various example embodiments may be more completely understood in consideration of the following detailed description in connection with the accompanying drawings. 
         FIG. 1  is a schematic and diagrammatic view of a catheter system for performing a therapeutic medical procedure, consistent with various aspects of the present disclosure. 
         FIG. 2  is a cross-sectional front-view of a portion of a heart with an ablation balloon catheter locating a pulmonary vein from within the left atrium, consistent with various aspects of the present disclosure. 
         FIG. 3  is a cross-sectional front-view of a left atrium with an ablation balloon catheter where the ablation balloon is inflated prior to contact with tissue proximate a pulmonary vein, consistent with various aspects of the present disclosure. 
         FIG. 4  is a cross-sectional front-view of portions of a left atrium and a pulmonary vein with an ablation balloon catheter positioned therein, prior to deployment of the ablation balloon, consistent with various aspects of the present disclosure. 
         FIG. 5  is a cross-sectional front-view of a pulmonary vein with an ablation balloon catheter deployed therein, consistent with various aspects of the present disclosure. 
         FIG. 6  is a plan view of an ablation balloon, consistent with various aspects of the present disclosure. 
         FIG. 7  is a plan view of an ablation balloon, consistent with various aspects of the present disclosure. 
         FIG. 8  is a plan view of an ablation balloon, consistent with various aspects of the present disclosure. 
         FIG. 9A  is a plan view of an ablation balloon, consistent with various aspects of the present disclosure. 
         FIG. 9B  is a plan view of the ablation balloon of  FIG. 9A , consistent with various aspects of the present disclosure. 
     
    
    
     While various embodiments discussed herein are amenable to modifications and alternative forms, aspects thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the scope to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure including aspects defined in the claims. In addition, the term “example” as used throughout this application is only by way of illustration, and not limitation. 
     DETAILED DESCRIPTION OF EMBODIMENTS 
     The instant disclosure relates to electrophysiology catheters for conducting diagnostics or tissue ablation within a heart. In particular, the instant disclosure relates to an electrophysiology catheter that either conforms to a shape of a pulmonary vein or deforms the tissue to the balloon shape for therapy of cardiac arrhythmias and produces a consistent tissue ablation line along a length and circumference of the pulmonary venous tissue. Details of the various embodiments of the present disclosure are described below with specific reference to the figures. 
     Typically, ablation therapies have been delivered by making a number of individual ablations in a controlled fashion in order to form a lesion line. Such lesion lines are often desirably formed around/between the pulmonary veins in the left atrium of the heart which have been associated with an introduction point of erratic electric signals into the heart. This type of ablation therapy requires precise positioning of the ablation catheter for optimal results. There are devices in development or being commercialized that attempt to achieve a sufficient block of ablations with minimal applications of energy. Existing designs range from diagnostic catheters with hoop and balloon mounted designs with energy applying features. Existing designs suffer from a lack of continuous contact around a circumference and length of the pulmonary vein during therapy deliver, resulting in inconsistent lesion lines and incomplete electrical signal blockage. 
     Referring now to the drawings wherein like reference numerals are used to identify similar components in the various views,  FIG. 1  is a schematic and diagrammatic view of a catheter ablation system  100  for performing a tissue ablation procedure. In an exemplary embodiment, tissue  120  (e.g., cardiac tissue, and heart) comprises cardiac tissue within a human body  140 . It should be understood, however, that the system may find application in connection with a variety of other tissues within human and non-human bodies, and therefore, the present disclosure is not meant to be limited to the use of the system in connection with only cardiac tissue and/or human bodies. 
     Catheter ablation system  100  may include a catheter  160  and an ablation subsystem  180  for controlling an ablation therapy conducted by an ablation balloon  130  at a distal end of the catheter  160 . The ablation subsystem  180  can control the application of and/or generation of ablative energy including, for example, radio frequency (RF), direct current (DC), irreversible electroporation, cryoablation, laser, chemical, and high-intensity focused ultrasound. Example embodiments of such ablation subsystems are described in U.S. Pat. Nos. 8,449,538, 9,289,606, 8,382,689, and 8,790,341, which are hereby incorporated by reference as though fully set forth herein. 
     In the exemplary embodiment of  FIG. 1 , catheter  160  is provided for examination, diagnosis, and/or treatment of internal body tissue such as cardiac tissue  120 . The catheter may include a cable connector or interface  121 , a handle  122 , a shaft  124  having a proximal end  126  and a distal end  128  (as used herein, “proximal” refers to a direction toward the end of the catheter  160  near the handle  122 , and “distal” refers to a direction away from the handle  122 ), and an ablation balloon  130  coupled to the distal end of the catheter shaft  124 . 
     In an exemplary embodiment, ablation balloon  130  is manipulated through vasculature of a patient  140  using handle  122  to steer one or more portions of shaft  124  and position the ablation balloon at a desired location within heart  120 . In various embodiments, the ablation balloon includes ablation elements (e.g., ablation electrodes, high intensity focused ultrasound ablation elements, etc.) that when operated by ablation subsystem  180  ablates the tissue  120  in contact with the ablation balloon  130  (and in some cases tissue  120  in proximity to the ablation balloon  130  may be ablated by conductive energy transfer through the blood pool and to the proximal tissue). 
     In various specific embodiments of the present disclosure, catheter  160  may include electrodes and one or more positioning sensors at a distal end  128  of catheter shaft  124  (e.g., electrodes or magnetic sensors). In such an embodiment, the electrodes acquire EP data relating to cardiac tissue  120 , while the positioning sensor(s) generate positioning data indicative of the 3-D position of the ablation balloon  130 . In further embodiments, the catheter  160  may further include other conventional catheter components such as, for example and without limitation, steering wires and actuators, irrigation lumens and ports, pressure sensors, contact sensors, temperature sensors, additional electrodes, and corresponding conductors or leads. 
     Connector  121  provides mechanical and electrical connection(s) for one or more cables  132  extending, for example, from ablation subsystem  180  to ablation balloon  130  mounted on, along, within, or through the distal end  128  of catheter shaft  124 . In other embodiments, the connector may also provide mechanical, electrical, and/or fluid connections for cables extending from other components in catheter system  100 , such as, for example, a fluid source (when the catheter  160  comprises an irrigated catheter) and contact/pressure sensing circuitry. The connector  121  is conventional in the art and is disposed at a proximal end  126  of the catheter  160 . 
     Handle  122  provides a location for a user to hold catheter  160  and may further provide steering or guidance for the shaft  124  within the body  140 . For example, the handle  122  may include means to manipulate one or more steering wires extending through the catheter  160  to a distal end  128  of the shaft  124  to steer the shaft. The handle  122  is conventional in the art and it will be understood that the construction of the handle may vary. In other embodiments, control of the catheter  160  may be automated by robotically driving or controlling the catheter shaft  124 , or driving and controlling the catheter shaft  124  using a magnetic-based guidance system. 
     Catheter shaft  124  is an elongated, tubular, and flexible member configured for movement within a patient&#39;s body  140 . The shaft supports an ablation balloon  130  at a distal end  128  of catheter  160 . The shaft  124  may also permit transport, delivery and/or removal of fluids (including irrigation fluids, cryogenic ablation fluids, and body fluids), medicines, and/or surgical tools or instruments. The shaft  124 , which may be made from conventional materials used for catheters, such as PEBAX or polyurethane, defines one or more lumens configured to house and/or transport electrical conductors, fluids, and/or surgical tools. The catheter may be introduced into a blood vessel or other structure within the body  140  through a conventional introducer sheath. 
     In an exemplary cardiac ablation therapy, to correct for atrial arrhythmia, the introducer sheath is introduced through a peripheral vein (typically a femoral vein) and advanced into the right atrium, in what is referred to as a transeptal approach. The introducer sheath is then used to make an incision in the fossa ovalis (the tissue wall between the left and right atriums), and extends through the incision in the fossa ovalis to anchor the introducer sheath in the fossa ovalis. The ablation catheter  160  may then be extended through a lumen of the introducer sheath into the left atrium. Catheter shaft  124  of ablation catheter  160  may then be steered or guided through the left atrium to position an ablation balloon  130  into a desired location within the left atrium such as a pulmonary vein. 
     During cardiac ablation therapy, it is desirable to align the centerline of ablation balloon  130  with a centerline of a pulmonary vein in which the ablation therapy is to take place. Alignment of the ablation balloon is particularly difficult in many embodiments due to the transeptal approach through the fossa ovalis which causes the shaft  124  to be naturally biased toward a left side of a patient&#39;s body  140 . This bias places an additional torque on ablation catheter system  100 , which may result in the ablation balloon, after placement within the pulmonary vein, to bias away from the centerline of the pulmonary vein. Where the ablation balloon  130  is deployed away from the centerline of the pulmonary vein, the deployment may result in uneven contact pressure and corresponding uneven pulmonary vein tissue wall stress. It has been discovered that contact area and tissue strain are associated with decreased ablation therapy efficacy. Aspects of the present disclosure improve the efficacy of ablation therapy by more effectively positioning the ablation balloon  130  circumferential with a centerline of the pulmonary vein. In more specific embodiments, the deployed ablation balloon  130  further improves ablation therapy efficacy by having improved contour mapping to the pulmonary vein, thereby deploying and engaging the pulmonary vein along an extended and uninterrupted length and circumference of the ablation balloon  130 . 
       FIG. 2  is a cross-sectional front-view of a portion of a heart  210  with an ablation balloon catheter  231  in a deflated state locating a pulmonary vein (e.g.,  214 ,  216 ,  218 , and  220 ) from within left atrium  212 L, consistent with various aspects of the present disclosure. Such an approach may be used for performing atrial fibrillation therapy. As shown in  FIG. 2 , the cardiac muscle  210  includes two upper chambers called the left atrium  212 L and right atrium  212 R, and two lower chambers called the left ventricle and right ventricle (not shown). 
     Aspects of the present disclosure are directed to ablation therapies in which tissue in pulmonary veins  214 ,  216 ,  218 , and  220 , which form conductive pathways for electrical signals traveling through the tissue, is destroyed in order to electrically isolate sources of unwanted electrical impulses (arrhythmiatic foci) located in or near the pulmonary veins. By either destroying the arrhythmiatic foci, or electrically isolating them from the left atrium  212 L, the cause of atrial fibrillation can be reduced or eliminated. 
     As shown in  FIG. 2 , an ablation balloon catheter  231  may be introduced into the left atrium  212 L by an introducer sheath  230 . A guidewire and a steerable portion of the catheter shaft,  232  and  234 , respectively, may guide the ablation balloon  236  once introduced into the left atrium  212 L by the introducer sheath  230 . Optionally, the ablation balloon catheter  231  may include mapping electrodes at proximal and distal ends of ablation balloon,  240  and  238 , respectively. In operation, introducer sheath  230  has its distal end positioned within left atrium  212 L. As shown in  FIG. 2 , a transeptal approach may be utilized in which introducer sheath  230  is introduced through a peripheral vein (typically a femoral vein) and advanced to right atrium  212 R. The introducer sheath  230  is used to make a small incision into the fossa ovalis  226  which allows the distal end of the introducer sheath  230  to enter the left atrium  212 L (through the transeptal wall  224 ) and to anchor itself to the wall of the fossa ovalis  226 . 
     Ablation balloon catheter  234  may also be introduced into left atrium  212 L through the arterial system. In that case, introducer sheath  230  is introduced into an artery (such as a femoral artery) and advanced retrograde through the artery to the aorta, the aortic arch, and into the left ventricle. The ablation balloon catheter  234  is then extended from within a lumen of the introducer sheath  230  to enter the left atrium  212 L through mitral valve  222 . 
     Once introducer sheath  230  is in position within left atrium  212 L, steerable ablation balloon catheter  231  is advanced out a distal end of the introducer sheath and toward one of the pulmonary veins (e.g.,  214 ,  216 ,  218 , and  220 ). In  FIG. 2 , the target pulmonary vein is right superior pulmonary vein  214 . A guidewire  232  and a steerable portion  234  of the ablation balloon catheter are manipulated until the distal tip of the ablation balloon catheter is directed toward the ostium of the target pulmonary vein, after which the ablation balloon is extended toward the pulmonary vein (e.g., superior pulmonary vein  214 ). 
     Carried near a distal end of ablation balloon catheter  231 , ablation balloon  236  remains in a collapsed condition so that it may pass through introducer sheath  230 , and approach the target pulmonary vein  214 . Once in proximity, the ablation balloon  236  is deployed, so that it may be advanced to engage and secure the ablation balloon catheter  231  in a position axial to the target pulmonary vein  214 . 
     As optionally shown, the embodiment of  FIG. 2  may include mapping electrodes  238  and  240 . The mapping electrodes  238  and  240  may be ring electrodes that allow the clinician to perform a pre-deployment electrical mapping of the conduction potentials of the pulmonary vein  214 . Although shown as being carried on ablation balloon catheter  231 , mapping electrodes may alternatively be carried on-board a separate electrophysiology catheter. 
     To ablate the tissue, once deployed, ablation balloon  236  may electrically conduct a DC energy current into the targeted tissue of the pulmonary vein  214 . In other embodiments, the ablation balloon  236  may transmit radio-frequency energy to ablate the target tissue. In yet other embodiments, the ablation balloon  236  may deliver one or more of the following energies to the targeted tissue: cryoablation, laser, chemical, and high-intensity focused ultrasound, among others. 
       FIG. 3  shows an ablation balloon catheter  331  including an ablation balloon  336  in an inflated state prior to contact with tissue proximate a pulmonary vein  314 . After inflation, the distal end of the ablation balloon catheter  331  enters the pulmonary vein  314 , mapping may be conducted using electrodes  338  and/or  340  in order to verify proper location prior to deployment of the ablation balloon  336 . 
     It has been discovered that proper positioning of the ablation balloon within the pulmonary vein is critical to the efficacy of an ablation therapy. For example, if the ablation balloon is not centered axially within the pulmonary vein when inflated, a portion of the ablation balloon may not contact a portion of the pulmonary vein circumference. This portion of non-lesioned tissue will allow for the continued conduction of electrical signals through the pulmonary vein and into the left atrium  312 L of the heart  310 . Such non-lesioned tissue greatly impedes the efficacy of the lesioned tissue to limit the flow of stray electrical signals that cause arrhythmias. Moreover, the ill-centered position and uneven pressure of the ablation balloon within the pulmonary vein  314  may overly-stress pulmonary vein tissue that is in contact with the ablation balloon  336  when inflated, and may also reposition the pulmonary vein closer to structures (e.g., phrenic and esophageal nerves) that can be damaged by a nominal lesion depth of the ablation therapy. The Applicant has discovered that overly-straining the pulmonary vein tissue results in thin tissue and a deeper lesion than desired; similarly, under-straining the pulmonary vein tissue results in thicker tissue a shallower lesion than desired—all of which decreases ablation therapy efficacy. Specifically, stressed tissue is less likely to evenly ablate and may even exhibit increased thermal capacity capability, therefore being capable of absorbing increased ablation energy before necrosis. Accordingly, aspects of the present disclosure improve the fit of the ablation balloon  336  at the ostium of the pulmonary vein  314  with an ablation balloon profile that better conforms to the contours of the pulmonary vein  314 . This improved conformance between the inflated ablation balloon  336  and pulmonary vein  314  results in improved ablation therapy efficacy, and the reduced need for duplicative therapies. 
       FIG. 4  is a cross-sectional front-view of portions of a left atrium  412 L and a pulmonary vein  414  with an ablation balloon catheter  431  positioned therein, after deployment of the ablation balloon  436  (e.g., in an inflated state), consistent with various aspects of the present disclosure. As shown in  FIG. 4 , the ablation balloon  436  is proximate the pulmonary vein  414  prior to balloon deployment and proximate an antral portion  416  of the target pulmonary vein  414 . In one embodiment of the present disclosure, the proper location of the ablation balloon may be determined/verified by mapping, prior to deployment of the ablation balloon. 
       FIG. 5  shows expanded ablation balloon  536  (e.g., an inflated state) engaged proximate the antral portion  516  of target pulmonary vein  514 . The ablation balloon  536  can have various shapes when expanded/inflated, as further discussed in relation to  FIGS. 6-10 . The various shapes can be designed to, for example, more precisely match the contours of the pulmonary vein, reduce the chance of perforation of tissue before, during, and after a procedure with the ablation balloon. 
     This ablation balloon shape shown in  FIG. 5  can increase the surface area contact between tissue proximate the pulmonary vein and the expanded/inflated ablation balloon, which consequently improves the efficacy of the ablation therapy that relies on surface contact between the ablation balloon and tissue proximate the pulmonary vein tissue. Without continuous contact along a circumference of tissue proximate of the pulmonary vein, a continuous lesion along the circumference may not be formed. As a result, stray electrical signals (though likely decreased in strength) may still be able to travel between the pulmonary vein and left atrium  512 L. Accordingly, the patient may still experience cardiac arrhythmias. As such, continuous contact along a diameter of the tissue proximate the pulmonary vein is necessary to completely ablate the tissue proximate the pulmonary vein tissue and to mitigate all electrical signal communication between the pulmonary vein and the left atrium. To achieve such continuous contact, the present disclosure teaches a multi-contour ablation balloon with at least three distinct portions for more effective ablation therapies. 
     In its expanded/inflated state shown in  FIG. 5 , ablation balloon  536  engages tissue proximate pulmonary vein  514 . Through one or more ablation processes mentioned above, the ablation balloon  536  produces a circumferential zone of ablation  550  along the tissue proximate the pulmonary vein proximate the antral  516  portion. The ablation zone electrically isolates the target pulmonary vein from left atrium  512 L. To the extent that arrhythmiatic foci were located within the ablation zone, the arrhythmiatic foci are destroyed. To the extent the arrhythmiatic foci are located in the target pulmonary vein on the opposite side of the ablation zone from the left atrium, the electrical impulses produced by those foci are blocked or inhibited by the ablation zone. 
     In a typical ablation therapy, pulmonary veins are treated in accordance to their likelihood of having an arrhythmiatic foci. Often, all pulmonary veins are treated. The processes as described for right superior pulmonary vein  214  are similar for each of the three other pulmonary veins  216 ,  218 , and  220  (see  FIG. 2 ). 
     Once ablation therapy is complete, ablation balloon  536  may be deflated and ablation balloon catheter  534  may be retracted back into introducer sheath  230  (as shown in  FIG. 2 ). An electrophysiology catheter, or sub-electrodes (e.g.,  238  and  240  in  FIG. 2 ) proximal and distal to the ablation balloon, may be used to verify the efficacy of the therapy prior to removal of the ablation balloon catheter  534 . In various embodiments of the present disclosure, additional subelectrodes may also be positioned on a surface of the ablation balloon  536 , either alone, or in conjunction with the subelectrodes  238  and  240 . 
     Ablation balloons have been developed for a variety of different applications and take a number of different forms. Aspects of the present disclosure may utilize ablation balloons of various types and different mechanical construction. The ablation balloons may be either of a conductive or a nonconductive material and can be either self-erecting or mechanically erected, such as through the use of an internal balloon. In one example embodiment, a lumen extending through a length of a shaft of the ablation balloon catheter  534  may inject a fluid into the ablation balloon which exerts a radial force on the ablation balloon and thereby expands/inflates the balloon into an erect configuration (as shown in  FIG. 5 ). The ablation balloons can be made from various polymers including, for example, PET, nylon, PEBAX, Pellethane® or Tecothane™. In some embodiments with multiple balloons, a lubricant can be included to facilitate expansion of the ablation balloons (e.g., less friction for the ablation balloons during deployment/retraction from an introducer (e.g., introducer  330  of  FIG. 3 )). 
     In certain specific embodiments, an ablation balloon may consist of non-compliant material (e.g., inflates to one specific size or size range, even as internal pressure increases). In such embodiments, over-expansion of a distal portion of the balloon near a portion of the pulmonary vein tissue wall may be prevented where the proximal portion of the balloon has come into contact with an antral portion (e.g. antral portion  516 ) of the pulmonary vein tissue wall. In other embodiments, the ablation balloon may consist of compliant material (expands as internal pressure increases) or a combination of compliant and non-compliant (e.g., one or more non-compliant portions of a balloon). 
       FIG. 6  is a plan view of an ablation balloon, consistent with various aspects of the present disclosure. An ablation balloon  600  can have a proximal end  601  with an electrode  640  and a distal end  602  with an electrode  638 . The ablation balloon  600  can have a balloon longitudinal axis defined by the line A-A. The ablation balloon can be coupled with a distal region of a shaft (e.g., the shaft  124  of  FIG. 1 ) that has a shaft longitudinal axis. The shaft can couple with the ablation balloon at, for example, an internal balloon distal surface and an internal balloon proximal surface (e.g., the balloon  600  can be coupled with the shaft at two locations such as the internal balloon distal surface and the internal balloon proximal surface) or a proximal end  601  of the ablation balloon  600 . The ablation balloon  600  can have an inflatable portion with a length L 1A , where the length L 1A  is from a first location proximate a proximal end  601  to a second location proximate a distal end  602  of the ablation balloon  600 . The length L 1A  can range from approximately 10 to 60 mm. 
     The ablation balloon  600  can include a first portion  605  (i.e., a proximal portion; a balloon proximal portion), a second portion  610 , and a third portion  615  (i.e., a distal portion; a balloon distal portion). The proximal portion  605  can include a first profile radius  618  and can include, for example, a portion of the balloon  600  defined by a length L 1B . The second portion  610  can include a balloon waist  619  (e.g., a widest diameter of the balloon) that separates the proximal portion  605  and the distal portion  615  and can be designed to occlude an opening in a body (e.g., a pulmonary vein) and mate with an antral portion of the pulmonary vein. The distal portion  615  can be defined by a length L 1C  and can be designed to occlude an opening in a body (e.g., a pulmonary vein) and to mate with an ostial portion of the pulmonary vein. The distal portion  615  can be considered a tissue contacting surface as a portion can be in contact with tissue when inserted into/proximate the pulmonary vein. The distal portion  615  can include a radius  620  (e.g., a second profile radius) for the ablation balloon  600 . The second profile radius  620  can, for example, range from 1 to 5 mm. By including the second portion  610  and/or the distal portion  615  with the second profile radius  620 , the ablation balloon  600  is suited to conform to/with the contours of the pulmonary vein. In the embodiment shown in  FIG. 6 , the second profile radius  620  of the distal portion  615  of the ablation balloon  600  can allow for a better fit for some pulmonary vein profiles and can improve therapy delivery and long-term efficacy. 
     As shown in  FIG. 6 , the ablation balloon  600  can have a symmetrical shape. For example, the inflatable portion of the ablation balloon  600  can be symmetrical about the balloon longitudinal axis (defined by the line A-A) and/or the second profile radius  620  can be the same as the first profile radius  618  for the proximal portion  605  and the distal portion  615  and the length L 1B  can be one half of the length L 1A ). The ablation balloon can be, at times, considered asymmetrical with respect to the proximal portion and distal portions (e.g., the second profile radius  620  can be different from the first profile radius  618  and the length L 1B  can be less than one half of the length L 1A  and the length L 1C  can be more than one half of the length L 1A ; see  FIGS. 7-9B  and related discussion). 
     A size of the proximal portion  605  that includes a certain profile radius (e.g., the first profile radius  618 ) and can also be indicated by an angular measurement shown by an angle θ 1  in  FIG. 6 . A size of the distal portion  615  can be the same angular measurement, θ 1 , for the second profile radius  620 . In some embodiments, the balloon can include multiple different profile radii in the same portion (e.g., in the proximal portion  605  and/or the distal portion  615 ) and angular measurements can be used to describe the amount of the portion allocated to a particular profile radius and/or the location of that profile radius on the ablation balloon  600 .s 
     In one exemplary application of ablation balloon  600  of  FIG. 6 , the shape of the ablation balloon  600  may be tailor fit for a specific patient based on measurements (e.g., ultrasonic images, magnetic resonance images, etc.) of the patient&#39;s pulmonary vein and entrance thereto. Specifically, based on the measurements of the patient, a shape along the longitudinal axis of the ablation balloon  600  may be selected that mimics the shape of a portion of the pulmonary vein (and in some embodiments may vary along a length of the longitudinal axis). 
     In various embodiments of the present disclosure, an ablation balloon  600  is capable of conducting ablation therapy at more than one location of the ablation balloon. For example, energy can be delivered to the proximal portion  605 , the second portion  610 , and the distal portion  615  of the ablation balloon  600 . In some embodiments, the second portion  610 , the distal portion  615 , or a combination thereof may simultaneously conduct ablation therapy. For example, ablation energy can be applied in series (or in parallel) to the second portion  610  and the distal portion  615 . In more specific embodiments, the amount of ablation therapy (e.g., energy transmitted to the tissue, and the length of therapy) conducted at a tissue location may be controlled individually. 
     In cryoablation specific applications of an ablation balloon catheter, a distal portion of the expanded ablation balloon centers the ablation balloon within and/or proximate a pulmonary vein and anchors it thereto. A second portion and a distal portion are then cooled to deliver a cryoablation therapy to an antral portion of the pulmonary vein. Once the ablation therapy is complete, the ablation balloon is deflated and the ablation balloon is removed from the pulmonary vein. 
       FIG. 7  is a plan view of an ablation balloon, consistent with various aspects of the present disclosure. The ablation balloon  700  can include a first portion  705  (i.e., a proximal portion; a balloon proximal portion), a second portion  710 , and a third portion  715  (i.e., a distal portion; a balloon distal portion). The second portion  710  can include a balloon waist  719  (e.g., a widest diameter of the balloon) that separates the proximal portion  705  and the third portion  715 . The ablation balloon  700  can have a balloon longitudinal axis defined by the line B-B. The ablation balloon  700  can have a proximal end  701  with an electrode  740  and a distal end  702  with an electrode  738  and can be coupled with a shaft (e.g., the shaft  124  of  FIG. 1 ) at, for example, an internal balloon distal surface and an internal balloon proximal surface (e.g., the balloon  700  can be coupled with the shaft at two locations such as the internal balloon distal surface and the internal balloon proximal surface) or a proximal end  701  of the ablation balloon  700 . The proximal portion  705  can include a first profile radius  718  and can include, for example, include a portion of the balloon  700  defined by a length L 2B . The second portion  710  can couple the proximal portion  705  and the distal portion  715  defined by a length L 2C  and can be designed to occlude an opening in a body (e.g., a pulmonary vein) and mate with an antral portion of the pulmonary vein. The distal portion  715  can be considered a tissue contacting surface as a portion can be in contact with tissue when inserted into/proximate the pulmonary vein. The distal portion  715  can include a radius  720  (e.g., a second profile radius) for a profile of a surface of the ablation balloon  700  (compared to the ablation balloon of  FIG. 6 ). The second profile radius  720  can, for example, range from 10 mm to 30 mm. 
     The second profile radius  720 , larger than the second profile radius  620  in  FIG. 6 , can, for example, allow for better axial alignment of the ablation balloon  700  within the pulmonary vein and can also provide for a better fit (e.g., increased contact area) between the ablation balloon  700  and adjacent tissue for some pulmonary vein profiles. The improved fit of the ablation balloon  700  with the pulmonary vein can allow for a better seal between the ablation balloon  700  and the pulmonary vein, which can allow for improved therapy (e.g., minimizing blood flow bypassing the ablation balloon during therapy and better contact between the ablation balloon  700  and the pulmonary vein). The ablation balloon  700  can have an inflatable portion with a length L 2A , where the length L 2A  is from a first location proximate a proximal end  701  to a second location proximate a distal end  702  of the ablation balloon  700 . The inflatable portion can comprise a portion of the proximal portion  705  and a portion of the distal portion  715 . The length L 2A  can range from 10 to 60 mm. The length L 2B  can be, in some embodiments, one half of the length L 2A . Other embodiments can have the length L 2B  as more or less than one half of the length L 2A . 
     As shown in  FIG. 7 , the ablation balloon  700  can have a symmetrical shape. For example, the inflatable portion of the ablation balloon  700  can be symmetrical about the balloon longitudinal axis defined by the line B-B. The ablation balloon  700  can be asymmetrical in shape with respect to the proximal portion  705  and the distal portion  715 . For example, the ablation balloon  700  can have a concave profile in the proximal portion  705  and/or the distal portion  715 , The concave profiles at the proximal portion  705  and the distal portion  715  can be the same or they can be different (as shown in  FIG. 7 ). Other profiles for the proximal portion  705  and the distal portion  715  are also possible (e.g., linear, curved, convex, combinations of linear/curved/convex/concave, etc.) including combinations of profiles in a single portion (e.g., the proximal portion  705  can include a linear portion, a first concave portion, and a second concave portion, etc.). The shapes of the proximal portion  705  and the distal portion  715  can be described as polynomial expressions, where the polynomial expressions can be at least a second degree polynomial. In some embodiments, the second profile radius  720  can be different from the first profile radius  718  for the proximal portion  705  and the length L 2B  can be more or less than one half of the length L 2A . 
     A size of the proximal portion  705  that includes a certain profile radius (e.g., the first profile radius  718 ) can be indicated by an angular measurement shown by an angle θ 2  in  FIG. 7 . A size of the distal portion  715  can be a different angular measurement, θ 3 , for the second profile radius  720 . In some embodiments, the balloon can include multiple different profile radii in the same portion (e.g., in the proximal portion  705  and/or the distal portion  715 ) and angular measurements can be used to describe the amount of the portion allocated to a particular profile radius and/or the location of that profile radius on the ablation balloon  700 . 
       FIG. 8  is a plan view of an ablation balloon, consistent with various aspects of the present disclosure. The ablation balloon  800  can have a proximal end  801  with an electrode  840  and a distal end  802  with an electrode  838  and can be coupled with a shaft (e.g., the shaft  124  of  FIG. 1 ) at, for example, an internal balloon distal surface and an internal balloon proximal surface (e.g., the balloon  800  can be coupled with the shaft at two locations such as the internal balloon distal surface and the internal balloon proximal surface) or a proximal end  801  of the ablation balloon  800 . The ablation balloon  800  can include a first portion  805  (i.e., a proximal portion; a balloon proximal portion), a second portion  810 , and a third portion  815  (i.e., a. The second portion  810  can include a balloon waist  819  (e.g., a widest diameter of the balloon) that separates the first portion  805  and the third portion  815  (i.e., a distal portion; a balloon distal portion). The first portion  805  can include a portion of the balloon  800  defined by a length L 3B . The second portion  810  can couple to the first portion  805  and the third portion  815  and can be designed to occlude an opening in a body (e.g., a pulmonary vein) and mate with an antral portion of the pulmonary vein. The distal portion  815  can be considered a tissue contacting surface as a portion can be in contact with tissue when inserted into/proximate the pulmonary vein. The third portion  815  can include a radius  820  (e.g., a second profile radius) for a different profile of a surface of the ablation balloon  800  (compared to the ablation balloon of  FIGS. 6-7 ) for fitting with various pulmonary vein shapes. The second profile radius  820  can range from 10 to 30 mm. 
     The ablation balloon  800  can have an inflatable portion with a length L 3A , where the length L 3A  is from a first location proximate a proximal end  801  to a second location proximate a distal end  802  of the ablation balloon  800 . The inflatable portion can comprise a portion of the proximal portion  805  and a portion of the distal portion  815 . The length L 3A  can range from 10 to 60 mm. Length L 3A  can be shorter than L 2A  or L 1A  of  FIGS. 6-7  respectively, which allows the ablation balloon  800  shown in  FIG. 8  to be more maneuverable (compared to the ablation balloons  600  and  700  of  FIGS. 6-7 ). The increased maneuverability can, for example, allow for easier/more effective placement of the ablation balloon  800  and can also reduce the risk of damage (e.g., perforation) to tissue during placement and/or movement of the ablation balloon  800 . The length L 3B  can be minimized (e.g., using selected profile shapes) to help minimize the overall length L 3A  to maximize the maneuverability of the ablation balloon  800 . The length L 3B  can be, in some embodiments, less than half the length L 3A . For example, L 3B  can be 10%, 20%, 25%, 30%, 33%, 40%, 45%, or any other suitable portion of L 3A  that is less than 50%. 
     As shown in  FIG. 8 , the ablation balloon  800  can have a symmetrical shape. For example, the inflatable portion of the ablation balloon  800  can be symmetrical about the balloon longitudinal axis (defined by the line C-C). The ablation balloon  800  can be asymmetrical in shape with respect to the proximal portion and the distal portion. For example, the ablation balloon  800  can have a concave profile in the first portion  805  and/or the third portion  815 . Other profiles for the first portion  805  and the third portion  815  are also possible (e.g., linear, curved, convex, combinations of linear/curved/convex/concave, etc.) including combinations of profiles in a single portion (e.g., the first portion  805  can include a linear portion, a first concave portion, and a second concave portion, etc.). The shapes of the proximal portion  805  and the distal portion  815  can be described as polynomial expressions, where the polynomial expressions can be at least a second degree polynomial. The concave profiles at the first portion  805  and the third portion  815  can be the same or they can be different (as shown in  FIG. 8 ). 
     A size of the first portion  805  that includes a certain profile radius (e.g., the first profile radius  818 ) can be indicated by an angular measurement shown by an angle θ 4  in  FIG. 8 . A size of the second portion  815  can be a different angular measurement, θ 3 , for the second profile radius  820 . In some embodiments, the balloon can include multiple different profile radii in the same portion (e.g., in the first portion  805  and/or the second portion  815 ) and angular measurements can be used to describe the amount of the portion allocated to a particular profile radius and/or the location of that profile radius on the ablation balloon  800 . 
       FIG. 9A  is a plan view of an ablation balloon, consistent with various aspects of the present disclosure. The ablation balloon  900  can have a proximal end  901  with and electrode  940  and a distal end portion  925  and can include a first portion  905  (i.e., a proximal portion; a balloon proximal portion), a second portion  910 , and a third portion  915  (i.e., a distal portion; a balloon distal portion). The second portion  910  can include a balloon waist  919  (e.g., a widest diameter of the balloon) that separates the first portion  905  and the third portion  915 . The first portion  905  can include a portion of the balloon  900  proximate the proximal end  901 . The third portion  915  can have a linear profile (e.g., no radius) or a large radius that results in a nearly linear profile (e.g., a radius larger than second radii profiles  620 ,  720 , and  820  of  FIGS. 6-8 ). The ablation balloon  900  can have a length L 4 , where the length L 4  is from a first location proximate a proximal end  901  to a distal end portion  925  of the ablation balloon  900 . The length L 4  can range from 10 to 60 mm. 
     A distal end portion  925  of the ablation balloon  900  can be formed by, for example, inverting a distal end  902  having an electrode  938  as shown in  FIG. 9B , where the distal end  902  of the ablation balloon  900  is moved proximally and faces the opposite direction compared to the distal end portion  925  ablation balloons  600 ,  700 , and  800  shown in  FIG. 6-8  (see  FIG. 9B  for additional information). This configuration can be achieved by, for example, pulling proximally on a shaft (e.g., the shaft  124  of  FIG. 1 ) or other feature that is connected to a distal portion of the ablation balloon  900  and/or pushing distally on a portion of the third portion  915  of the ablation balloon  900 , (e.g., with a pull/activation wire connected to a portion of the ablation balloon  900  (not shown) to cause the distal end  902  of the ablation balloon  900  to move towards the proximal end  901  of the ablation balloon  900  (e.g., see  FIG. 9B ). The configuration in  FIG. 9A  can, for example, help reduce the risk of undesired perforation of tissue during placement/movement of the ablation balloon  900  compared to the shapes of the ablation balloons  600 ,  700 , and  800  in  FIGS. 6-8  due to the blunter profile (e.g., more rounded with fewer protrusions) of the distal end portion  925  of the ablation balloon  900 . 
     The distal end portion  925  of the ablation balloon  900  can also be generated by a pre-formed balloon shape. In this configuration, the balloon  900  is configured to achieve an inflated/expanded shape as shown in  FIG. 9A  after being deployed. 
     The ablation balloon  900  can be asymmetrical in shape (e.g., along a longitudinal axis). For example, the ablation balloon  900  can have a first profile radius  918  in the first portion  905  and/or the third portion  915  that is concave and/or linear, The profiles at the first portion  905  and the third portion  915  can be the same or they can be different (as shown in  FIGS. 9A and 9B  where the profile of the first portion is concave and the profile of the third portion generally linear). Other profiles for the first portion  905  and the third portion  915  are also possible (e.g., linear, convex, combinations of linear/convex/concave, etc.) including combinations of profiles in a single portion (e.g., the first portion  905  can include a linear portion, a first concave portion, and a second concave portion where each concave portion has a different radius, etc.). The shapes of the proximal portion  905  and the distal portion  915  can be described as polynomial expressions, where the polynomial expressions can be at least a second degree polynomial. 
     A size of the first portion  905  that includes a certain profile radius (e.g., the first profile radius  918 ) can be indicated by an angular measurement shown by an angle θ 5  in  FIG. 9 . A size of the second portion  915  can be a different angular measurement, θ 6 , for the second profile radius  920 . In some embodiments, the balloon can include multiple different profile radii in the same portion (e.g., in the first portion  905  and/or the second portion  915 ) and angular measurements can be used to describe the amount of the portion allocated to a particular profile radius and/or the location of that profile radius on the ablation balloon  900 . 
       FIG. 9B  is a plan view of the ablation balloon of  FIG. 9A , consistent with various aspects of the present disclosure. As shown in  FIG. 9B , the distal end  902  of the ablation balloon  900  can be inverted (e.g., the distal end  902  of the ablation balloon  900  is facing the proximal end  901 ) where the distal end  902  of the ablation balloon  900  is pointed towards the proximal end  901 , causing the ablation balloon  900  to have a the configuration shown in  FIGS. 9A-9B . As described above, the configuration shown in  FIG. 9B  can be achieved by, for example, pulling proximally on a shaft (e.g., the shaft  124  of  FIG. 1 ) that is connected to a distal portion of the ablation balloon  900  and/or pushing distally on a distal portion of the third portion  915  of the ablation balloon  900 , (e.g., with a pull/activation wire connected to a portion of the ablation balloon  900  (not shown) to cause the distal end  902  to move towards the proximal end  901 . As described above, the configuration of balloon  900  can also be achieved by the inflated/expanded shape of the balloon. 
     In various embodiments of the present disclosure, an ablation balloon may include one or more (internal) balloons that may be independently inflated. In one exemplary embodiment, a first (internal) balloon positioned at a proximal end of the ablation balloon may be expanded to deliver ablation therapy circumferentially to the pulmonary vein antrum, and a second (internal) balloon positioned at a distal end of the ablation balloon may be expanded to deliver ablation therapy circumferentially to the pulmonary vein ostia. Such (internal) balloons can relate to portions of the ablation balloons in  FIGS. 6 and 7  (e.g., first portions  605  and  705 , second portions  610  and  710 , and third portions  615  and  715 ). In one specific embodiment, the one or more internal balloons may be encompassed by an external balloon. 
     One important benefit of the present disclosure is that ablation balloons, consistent herewith, are associated with decreased esophageal and phrenic nerve interaction with the pulmonary vein. Often times, such interaction is caused by wall distortion due to expansion of the balloon and advancement toward the pulmonary vein. Preventing interaction between the pulmonary veins and the esophageal and phrenic nerves greatly decreases complications related to nerve damage from the ablation therapy. 
     Various embodiments of the present disclosure are directed to pulmonary vein isolation balloon designs for optimum therapy delivery. Specifically, the balloon designs disclosed herein may be configured to facilitate improved energy delivery or extraction by better alignment between the balloon and the antral and/or proximal ostia portions of the pulmonary vein. The various embodiments disclosed herein may be applied to any of the various balloon-based energy delivery means (such as those discussed in more detail above). 
     Many cardiac catheter applications utilize the fossa ovalis to enter the heart. Due to the geometry between the fossa ovalis and an entrance to the pulmonary veins in the left atrium, the catheter shaft will naturally be biased towards a left side of the patient, putting pull/torque on the cardiac catheter as it locates (and is positioned in contact with) the pulmonary vein (e.g., for pulmonary vein isolation ablation therapy procedures). This biasing force pulls the catheter shaft off the natural centerline of the pulmonary vein being targeted, causing a variation in the forces and contact surface area experienced between the balloon and the pulmonary vein walls. As an example, when the biasing force pulls an ablation balloon off the natural centerline of a target pulmonary vein, the contact surface area and force exerted by the balloon on the side of the pulmonary vein which receives the additional biasing force will be greater than the other side(s) of the balloon. As a result, the energy delivery or extraction of the catheter is tied to catheter position, and may be one contributor to therapy variation. 
     Various embodiments of the present disclosure may be directed to multi-shape balloons for ostial and antral coverage of pulmonary vein geometry (e.g., two or more geometries). Such multi-shape balloons may facilitate centering of the balloon within a pulmonary vein for uniform ablation therapy applications, for example. Also, such multi-shape balloons may enable energy delivery to both antral and ostial portions of the pulmonary vein simultaneously (due to the increased contact area)—thereby targeting linear and circumferential conduction paths. In yet further embodiments, the multi-shape balloons may target energy delivery to distal, mid, or proximal balloon surfaces. The multi-shape balloon may also utilize a distal length of the balloon to contact an ostial portion of the pulmonary vein, facilitating proper centering of the balloon in the pulmonary vein while a proximal length of the balloon in contact with an antrum of the pulmonary vein conducts the ablation therapy. 
     Additional information about ablation balloons can be found in U.S. application No. 62/432,045, filed on 9 Dec. 2016 (attorney docket no. 065513-001367) and U.S. application No. 62/432,065 (attorney docket no. 065513-001414), filed on 9 Dec. 2016, and are hereby incorporated by reference as if set forth fully herein. 
     Additional information and examples can be found in U.S. application Ser. No. ______. (attorney docket number 065513-001658, filed concurrently), U.S. application Ser. No. ______. (attorney docket number 065513-001660, filed concurrently), U.S. application Ser. No. ______. (attorney docket number 065513-001661, filed concurrently), and U.S. application Ser. No. ______. (attorney docket number 065513-001662, filed concurrently), each of which is hereby incorporated by reference as if set forth fully herein. 
     Aspects of the present disclosure are directed to a medical device balloon apparatus. The apparatus including a distal portion with a first circumference, a proximal portion, and an intermediary portion. The proximal portion has a second circumference which is greater than the first circumference, and the intermediary portion has a varying circumference coupled between the proximal and distal portions of the ablation balloon. The distal portion includes a first circumferentially extending surface and the proximal portion includes a second circumferentially extending surface. Both of the first and second circumferentially extending surfaces extending tangential from a radial line extending off a longitudinal axis of the medical device balloon apparatus. 
     In one exemplary embodiment of the present disclosure, a system for treating atrial fibrillation is taught. The system including a balloon delivery catheter including proximal and distal ends, and an ablation balloon coupled to the distal end of the balloon delivery catheter. The ablation balloon including distal, proximal, and intermediary portions. The distal portion having a first circumference, and engages with an ostium of a pulmonary vein for aligning a longitudinal axis of the ablation balloon with a second longitudinal axis of the pulmonary vein. The proximal portion has a second circumference which is greater than the first circumference. The intermediary portion is coupled between the proximal and distal portions of the ablation balloon, and has a varying circumference. At least one of the proximal and intermediary portions of the ablation balloon engage with an antrum of the pulmonary vein along an uninterrupted length and circumference, and deliver a uniform ablation therapy to the pulmonary vein antrum. 
     In another embodiment of the present disclosure, a balloon catheter is disclosed for pulmonary vein isolation. The balloon catheter including a catheter shaft, an ablation balloon, and tissue ablation means. The catheter shaft deploys an ablation balloon into a pulmonary vein, which is coupled to a distal end of the balloon delivery catheter. The ablation balloon deploys from an un-deployed configuration and engages with a tissue wall of the pulmonary vein along an uninterrupted length and circumference of an antrum and ostia of the pulmonary vein. The tissue ablation means, in association with the ablation balloon, delivers a uniform ablation therapy around a circumference of the pulmonary vein antrum engaged by the ablation balloon. The ablation balloon also overcomes a biasing force exerted upon the ablation balloon by the catheter shaft by engaging with the ostia of the pulmonary vein to overcome the biasing force. 
     Based upon the above discussion and illustrations, those skilled in the art will readily recognize that various modifications and changes may be made to the various embodiments without strictly following the exemplary embodiments and applications illustrated and described herein. For example, a deployed ablation balloon, consistent with aspects of the present disclosure, may consist of a number of varying geometries based on imaging data indicative of the internal dimensions of a patient&#39;s targeted pulmonary vein. In such an embodiment, the deployed ablation balloon engages the targeted pulmonary vein along an uninterrupted length and circumference of the ablation balloon to maximize the efficacy of the ablation therapy. Such modifications do not depart from the true spirit and scope of various aspects of the disclosure, including aspects set forth in the claims. 
     Although several embodiments have been described above with a certain degree of particularity to facilitate an understanding of at least some ways in which the disclosure may be practiced, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the scope of the present disclosure and the appended claims. It is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative only and not limiting. Accordingly, the examples and embodiments herein should not be construed as limiting the scope of the disclosure. Changes in detail or structure may be made without departing from the present teachings. The foregoing description and following claims are intended to cover all such modifications and variations. 
     Various embodiments are described herein of various apparatuses, systems, and methods. Numerous specific details are set forth to provide a thorough understanding of the overall structure, function, manufacture, and use of the embodiments as described in the specification and illustrated in the accompanying drawings. It will be understood by those skilled in the art, however, that the embodiments may be practiced without such specific details. In other instances, well-known operations, components, and elements may not have been described in detail so as not to obscure the embodiments described in the specification. Those of ordinary skill in the art will understand that the embodiments described and illustrated herein are non-limiting examples, and thus it can be appreciated that the specific structural and functional details disclosed herein may be representative and do not necessarily limit the scope of the embodiments, the scope of which is defined solely by the appended claims. 
     The terms “including,” “comprising” and variations thereof, as used in this disclosure, mean “including, but not limited to,” unless expressly specified otherwise. The terms “a,” “an,” and “the,” as used in this disclosure, means “one or more,” unless expressly specified otherwise. 
     Reference throughout the specification to “various embodiments,” “some embodiments,” “one embodiment,” “an embodiment,” or the like, means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases “in various embodiments,” “in some embodiments,” “in one embodiment,” “in an embodiment,” or the like, in places throughout the specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. Thus, the particular features, structures, or characteristics illustrated or described in connection with one embodiment may be combined, in whole or in part, with the features, structures, or characteristics of one or more other embodiments without limitation. 
     Although process steps, method steps, algorithms, or the like, may be described in a sequential order, such processes, methods, and algorithms may be configured to work in alternative orders. In other words, any sequence or order of steps that may be described does not necessarily indicate a requirement that the steps be performed in that order. The steps of the processes, methods, and algorithms described herein may be performed in any order practical. Further, some steps may be performed simultaneously. 
     When a single device or article is described herein, it will be readily apparent that more than one device or article may be used in place of a single device or article. Similarly, where more than one device or article is described herein, it will be readily apparent that a single device or article may be used in place of the more than one device or article. The functionality or the features of a device may be alternatively embodied by one or more other devices which are not explicitly described as having such functionality or features. 
     It will be appreciated that the terms “proximal” and “distal” may be used throughout the specification with reference to a clinician manipulating one end of an instrument used to treat a patient. The term “proximal” refers to the portion of the instrument closest to the clinician and the term “distal” refers to the portion located furthest from the clinician. However, surgical instruments may be used in many orientations and positions, and these terms are not intended to be limiting and absolute. All other directional or spatial references (e.g., upper, lower, upward, downward, left, right, leftward, rightward, top, bottom, above, below, vertical, horizontal, clockwise, and counterclockwise) are only used for identification purposes to aid the reader&#39;s understanding of the present disclosure, and do not create limitations, particularly as to the position, orientation, or use of the disclosure. Joinder references (e.g., attached, coupled, connected, and the like) are to be construed broadly and may include intermediate members between a connection of elements and relative movement between elements. As such, joinder references do not necessarily infer that two elements are directly connected and in fixed relation to each other. 
     Any patent, publication, or other disclosure material, in whole or in part, that is said to be incorporated by reference herein is incorporated herein only to the extent that the incorporated materials do not conflict with existing definitions, statements, or other disclosure material set forth in this disclosure. As such, and to the extent necessary, the disclosure as explicitly set forth herein supersedes any conflicting material incorporated herein by reference. Any material, or portion thereof, that is said to be incorporated by reference herein, but which conflicts with existing definitions, statements, or other disclosure material set forth herein will only be incorporated to the extent that no conflict arises between that incorporated material and the existing disclosure material.