Atrial septal channel device

Abstract

Embodiments disclosed herein include an atrial septal channel device that facilitates the creation and / or enlargement of a channel through an atrial septum, as well as methods and systems for using the same in the treatment of a patient. In an embodiment, an atrial septal channel device includes a cylindrical body section having a radiofrequency (RF) energy source, a first flanged section extending from a first end of the cylindrical body section and having a first diameter, and a second flanged section extending from a second end of the cylindrical body section and having a second diameter. In addition, the device is configured to expand within an atrial septal channel to increase the first diameter of the first flanged section, increase the second diameter of the second flanged section, and position the RF energy source in contact with an inner surface of the atrial septal channel.

Description

Atrial Septal Channel DeviceCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims benefit of U.S. provisional patent application no. 63 / 631 ,339 filed April 8, 2024, and entitled “Atrial Septal Channel Creation Device,” which is hereby incorporated herein by reference in its entirety for all purposes.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] This invention was made with government support under Contract Nos. P50FD006428 and P50FD007962 awarded by the Food and Drug Administration (DHHS). The government has certain rights in the invention.TECHNICAL FIELD

[0003] The present disclosure relates generally to a device for the creation and / or enlargement of an atrial septal channel, for example, an atrial septal channel enlargement device and / or an atrial septal channel creation device, and to methods and systems for using the same in the treatment of a patient.BACKGROUND

[0004] Numerous cardiac conditions require the creation of a suitable opening or channel across the wall of tissue (that is, the septum) that separates the two upper chambers (that is, the atria) of the heart. One such condition is Hypoplastic Left Heart Syndrome (HLHS). HLHS is a congenital birth defect occurring in about 1 in 5000 infants and accounts for 3% of all births with congenital birth defects. While this condition would have necessarily resulted in the death of the neonate in the past, modem surgical techniques involving staged surgical palliation have resulted in a survival rate as high as 76%. The Norwood, Glenn, and Fontan series of surgeries (and associated variants) reconfigures the cardiac circulation to support both systemic and pulmonary blood flow with a single ventricle where systemic blood flow passively flows to the pulmonary vascular bed before returning to the heart for pumping to the systemic bed.

[0005] While the etiology of HLHS is variable, the result is that the left heart structures are underdeveloped and unable to support normal cardiac function. Moreparticularly, with HLHS, the left side of the fetal heart is underdeveloped and incapable of proper function. The normally-developed fetal heart has an atrial septal opening, the foramen ovale, that supports cross-atrial blood flow to supply oxygenated blood to the body. Infants with HLHS normally rely upon the interconnection of the systemic and pulmonary blood flows through the foramen ovale and ductus arteriosus for survival. However, about 5% of infants with HLHS lack this opening, instead having an intact or restrictive atrial septum (l / RAS) preventing cross-atrial blood flow. This flow prevention or reduction leads to pulmonary venous hypertension and malformations in the development of the pulmonary vasculature in utero.

[0006] While outcomes for children with HLHS have improved over the years, children with l / RAS continue to have extremely poor outcomes post birth with mortality rates in one center reported as high as 74%. Fetal cardiac interventions (FCI) have been developed that attempt to improve the survival of babies with l / RAS by creating or widening a septal channel with the goal of relieving the left atrial hypertension earlier in fetal development to reduce the degree of pulmonary damage. These procedures commonly involve achieving percutaneous access across the fetal atrial septum via an 18-20-gauge introducer cannula with a fine needle / laser fiber under ultrasound guidance. For example, Fig. 1A illustrates a cannula disposed across the septum. Following this step, a balloon septostomy may be performed in attempts to expand or enlarge a septal opening. However, these procedures are limited in the size of the balloon that may be used because of the small introducer. The limited size of the balloon, together with tissue recoil or rebound, result in an undesirably restricted atrial septal channel. This issue is further expounded in cases with a thick atrial septum that contributes to larger tissue recoil. An example of a channel having a reduced size compared to the balloon is illustrated in Fig. 1 B.

[0007] To combat this insufficient channel size, stents have been placed across the atrial septum. However, in the absence of stents designed specifically for this application, surgeons must rely on off-label use of coronary stents deployed through the introducer cannula. Stenting has been shown to result in a less restrictive foramen ovale compared to septoplasty despite a slightly lower procedural success rate. While FCIs as a whole have been shown to significantly reduce the incidence of restrictive atrial septa at birth, the mortality rate of these children remains high. Additionally, the use of straight coronary stents poses significant challenges in precise stent placement acrossthe septum. For example, these devices are delivered under ultrasound guidance through the maternal abdominal wall, uterine wall, fetal chest, and into the fetal heart, and as such, the precision available to the surgeon is quite limited. In the fetal surgery for placing the stent, both the mother and the fetus can move relative to each other and the surgical devices. Such movements, when coupled with the hard-to-place conventional cylindrical-shaped stents, make the surgical operations especially challenging. These stents are also not designed for use across a thin-walled motile structure and present a grave risk of stent migration out of the septum and into either atrium.

[0008] Other possible solutions such as puncturing a hole in the atrial septum with a catheter needle have proven unsatisfactory, as the holes introduced in this manner are often not sufficiently large and can close up prematurely by natural healing processes. The cutting of a circular hole in the atrial septum using a circle cutter is also impractical for establishing a suitable channel in the atrial septum. Forexample, this cutting process produces loose circular atrial septum tissue that is imperative but challenging to remove from the fetal heart.

[0009] Additionally, various conditions in adults, such as situations in which left atrial decompression is desired, would benefit from creation and / or enlargement of a channel in the atrial septum. Heart failure affects over 5 million patients in the United States and the cost of this disease is expected to exceed $70 billion by 2030. As a result of the increased left atrial pressure caused by heart failure, 90% of hospitalizations for heart failure show symptoms of pulmonary congestion to varying degrees depending on the types of heart failure, such as (a) heart failure with preserved ejection (HFpEF), (b) heart failure with mid-range ejection fraction (HFmrEF), or (c) heart failure with reduced ejection (HFrEF). Creating an atrial septal channel can help decompress the left atrium, thereby reducing pulmonary pressures and alleviating symptoms. Patients with pulmonary atrial hypertension who have a patent foramen ovale are known to live longer than those without, making the creation of an atrial septal channel a promising treatment for patients with this condition. Additionally, patients with severe mitral valve disease, such as mitral stenosis or regurgitation, may also benefit from an atrial septal channel to relieve left atrial hypertension and improve hemodynamic stability. The procedure may also be used on patients under extracorporeal membrane oxygenation (ECMO) support who experience pulmonary edema. The use of atrial septal channels in theseadult conditions can improve quality of life and reduce hospitalizations by managing the underlying hemodynamic abnormalities more effectively.

[0010] Currently, in adults, these channels are generally created through unspecialized implanted devices such as stents which pose risks such as embolization. Another device creates an atrial septal channel by cutting a ring of tissue. While this device leaves no foreign material behind, the size of the created opening is limited to approximately the dimensions of the catheter that is used to deliver it, with current versions of the device preventing the use of smaller catheters.

[0011] As such, there is a need for an improved atrial septal channel device that will enable delivery via smaller catheters, while achieving opening sizes that are much larger than the outer diameter of the catheter.BRIEF SUMMARY OF THE DISCLOSURE

[0012] These and other needs in the art are addressed in one embodiment by an atrial septal channel device. In some embodiments, the device comprises a cylindrical body section comprising a radiofrequency (RF) energy source, a first flanged section extending from a first end of the cylindrical body section and having a first diameter, and a second flanged section extending from a second end of the cylindrical body section and having a second diameter. In addition, the device is configured to expand within an atrial septal channel to increase the first diameter of the first flanged section, increase the second diameter of the second flanged section, and position the RF energy source in contact with an inner surface of the atrial septal channel.

[0013] In certain embodiments, the first diameter, the second diameter, and a body diameter of the cylindrical body section are approximately equal when the device is in an unexpanded state, and the first diameter and the second diameter are each larger than the body diameter when the device is in an expanded state. In certain embodiments, the device is configured to radially expand the first flanged section to engage with a first side of an atrial septum and configured to radially expand the second flanged section to engage with a second side of the atrial septum.

[0014] In certain embodiments, the RF energy source comprises at least one electrode configured for delivery of RF energy to the inner surface of the atrial septal channel. In certain embodiments, the RF energy source is configured to deliver the RF energy for a predetermined time period or until a sensed parameter reaches apredetermined threshold. In certain embodiments, the RF energy source is configured to deliver the RF energy via a monopolar delivery modality or a bipolar energy delivery modality.

[0015] In certain embodiments, the RF energy source comprises a plurality of electrodes configured to deliver the RF energy. In certain embodiments, the plurality of electrodes comprises a first electrode having a first longitudinal length and a second electrode having a second longitudinal length, and the first electrode is interleaved with the second electrode to overlap the first longitudinal length with the second longitudinal length around a circumference of the cylindrical body section.

[0016] In certain embodiments, the device comprises an expandable balloon, the expandable balloon forms the first flanged section and the second flanged section, and the cylindrical body section comprises a sleeve member having a curved inner surface coupled to a curved outer surface of the expandable balloon. In certain embodiments, the device comprises a self-expanding stent having the cylindrical body section, the first flanged section, and the second flanged section. In certain embodiments, the device comprises a slotted tube expansion mechanism having the cylindrical body section, the first flanged section, and the second flanged section.

[0017] In some embodiments disclosed herein, a method for expansion of an atrial septal channel comprises disposing a device comprising a radiofrequency (RF) energy source in the atrial septal channel. The method further includes expanding the device to position the RF energy source in contact with an inner surface of the atrial septal channel expanded by the device, position a first flanged section of the device on a first side of the atrial septal channel, and position a second flanged section of the device on a second side of the atrial septal channel. Additionally, the method includes applying RF energy from the RF energy source to the inner surface to denature tissue of the atrial septal channel, erase tissue memory, and reduce tissue recoil.

[0018] In certain embodiments, applying the RF energy comprises activating the RF energy source for a predetermined time period. In certain embodiments, applying the RF energy comprises activating the RF energy source for one or more respective predetermined time periods during a predetermined number of activation cycles. In certain embodiments, applying the RF energy comprises activating the RF energy source until a sensed parameter reaches a predetermined threshold, and the sensed parameter comprises a temperature, an electrical impedance, a radial tissue force, or aradial tissue pressure.

[0019] In certain embodiments, the device comprises a cylindrical body portion having a body diameter positioned longitudinally between the first flanged section and the second flanged section, and expanding the device comprises increasing a first diameter of the first flanged section and increasing a second diameter of the second flanged section relative to the body diameter.

[0020] In certain embodiments, the device comprises an expandable balloon and a sleeve disposed around the expandable balloon to enable selective expansion of the first flanged section and the second flanged section. In certain embodiments, the sleeve comprises the RF energy source.

[0021] In certain embodiments, the device comprises a self-expanding stent or a slotted tube expansion mechanism. In certain embodiments, the self-expanding stent or the slotted tube expansion mechanism comprises a metallic material configured to direct the RF energy to the tissue of the atrial septal channel, and the metallic material comprises the RF energy source.

[0022] In certain embodiments, the RF energy source comprises a plurality of electrodes having a linear configuration, a nonlinear interleaved configuration, or a curvilinear interleaved configuration to deliver the RF energy via a bipolar energy delivery modality. In certain embodiments, disposing the device in the atrial septal channel comprises delivering the device via a cannula, a catheter, or a delivery tube. In certain embodiments, the method further comprising puncturing an atrial septum with a needle before disposing the device in the atrial septal channel.

[0023] In some embodiments disclosed herein, a self-expanding stent for expansion of an atrial septal channel includes a cylindrical body section having a body diameter, a first flanged section extending from a first end of the cylindrical body section and having a first diameter, and a second flanged section extending from a second end of the cylindrical body section and having a second diameter. In addition, the first diameter, the second diameter, and the body diameter are approximately equal when the stent is in an unexpanded state. Further, the first diameter and the second diameter are each larger than the body diameter when the stent is in an expanded state and positioned within the atrial septal channel.

[0024] In certain embodiments, the stent in the expanded state is configured to engage the first flanged section with a first side of an atrial septum and configured toengage the second flanged section with a second side of the atrial septum.

[0025] In certain embodiments, the self-expanding stent comprises an RF energy source comprising one or more electrodes configured to apply RF energy to an inner surface of the atrial septal channel to denature tissue thereof. In certain embodiments, the RF energy source is configured to deliver the RF energy for a predetermined time period or until a sensed parameter reaches a predetermined threshold. In certain embodiments, the RF energy source is configured to deliver the RF energy via a monopolar delivery modality or a bipolar energy delivery modality. In certain embodiments, the RF energy source comprises a plurality of electrodes configured to deliver the RF energy.

[0026] Embodiments described herein comprise a combination of features and characteristics intended to address various shortcomings associated with certain prior devices, systems, and methods. The foregoing has outlined rather broadly the features and technical characteristics of the disclosed embodiments in order that the detailed description that follows may be better understood. The various characteristics and features described above, as well as others, will be readily apparent to those skilled in the art upon reading the following detailed description, and by referring to the accompanying drawings. It should be appreciated that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes as the disclosed embodiments. It should also be realized that such equivalent constructions do not depart from the spirit and scope of the principles disclosed herein.BRIEF DESCRIPTION OF THE DRAWINGS

[0027] For a detailed description of exemplary embodiments of the disclosure, reference will now be made to the accompanying drawings in which:

[0028] Fig. 1A is a schematic view of an embodiment of a device delivery tube disposed across the atrial septum.

[0029] Fig. 1 B is a schematic view of an embodiment of balloon septoplasty, illustrating how deployment and removal of a balloon across the atrial septum leads to tissue of the septum recoiling to a reduced size.

[0030] Fig. 1C is a schematic view of an embodiment of a self-expanding stent according to one or more embodiments disclosed herein, illustrated as being partiallydeployed at the distal flange and also illustrated as fully deployed within an atrial septal channel.

[0031] Fig. 1 D is a schematic view of an embodiment of a radiofrequency (RF) energy balloon device according to one or more embodiments disclosed herein, illustrated as disposed across the atrial septum and also illustrated as disposed with respect to a denatured tissue (e.g., septum) so as to mitigate tissue recoil in the resulting channel.

[0032] Fig. 2 is a schematic view of an embodiment of a method of preparing a selfexpanding stent according to one or more embodiments disclosed herein.

[0033] Fig. 3A is an axial micrograph of a self-expanding flanged stent according to one or more embodiments disclosed herein.

[0034] Fig. 3B is a transverse micrograph of a flanged stent according to one or more embodiments disclosed herein.

[0035] Fig. 3C is a representation of a flanged stent deployed across an atrial septum analogue.

[0036] Fig. 3D is an axial representation of a deployed flanged stent illustrating the maintenance of an enlarged opening or channel in the atrial septum analogue.

[0037] Fig. 4A is a slotted tube expansion mechanism according to one or more embodiments disclosed herein, shown in an initial configuration suited for positioning through an opening in the atrial septum. The patterned segments indicate a possible bipolar electrode configuration with striped and filled portions representing electrically separate electrodes.

[0038] Fig. 4B is the slotted tube expansion mechanism of Fig. 4A illustrated in a shortened and expanded configuration.

[0039] Fig. 5A is a representation of a RF energy balloon device according to one or more embodiments disclosed herein, particularly, utilizing an unwrapped interleaved electrode array.

[0040] Fig. 5B is a schematic view of an electrode configuration for the RF energy balloon device.

[0041] Fig. 5C is a representation of a channel created and enlarged in the atrial septum analogue via an RF energy balloon device according to one or more embodiments disclosed herein.

[0042] Fig. 5D is an axial representation of a channel created in the atrial septumanalogue without the application of RF energy from an RF energy balloon device as disclosed herein, illustrating a high degree of tissue recoil.

[0043] Figs. 6A, 6B, and 6C represent various embodiments of electrode configurations according to one or more embodiments disclosed herein, with different shades representing electrically separate electrodes.

[0044] Figs. 7 A, 7B, and 7C illustrate a hinged balloon device having a balloon body integrated with constricting electrodes according to one or more embodiments disclosed herein.

[0045] Figs. 8A, 8B, 8C, 8D, 8E, and 8F represent embodiments of interleaved electrode configurations according to one or more embodiments disclosed herein, with four examples of pediatric-sized configurations followed by two examples of adult-sized configurations.

[0046] Figs. 9A and 9B are schematic views of an embodiment of an expandable stent according to one or more embodiments disclosed herein, illustrated in an unexpanded configuration and in an expanded configuration.

[0047] Fig. 10 is a representation of an embodiment of a method of preparing an expandable stent having a pattern laser cut onto a tubular member according to one or more embodiments disclosed herein.

[0048] Fig. 11 is a representation of the expandable stent of Fig. 10 that is fitted with a meshed sleeve between two flanged sections according to one or more embodiments disclosed herein.

[0049] Fig. 12 is a representation of another embodiment of a method of preparing an expandable stent by rolling and shortening a patterned sheet according to one or more embodiments disclosed herein.

[0050] Fig. 13 is a representation of another embodiment of a method of preparing an expandable stent by rolling and shortening a patterned sheet according to one or more embodiments disclosed herein.

[0051] Figs. 14A, 14B, 14C, 14D, 14E, 14F, and 14G illustrate certain aspects of a method of an atrial septum enlargement surgery, such as a fetal surgery for treating hypoplastic left heart syndrome (HLHS) with restrictive atrial septum (RS) according to one or more embodiments disclosed herein.

[0052] Figs. 15A, 15B, 15C, and 15D illustrate some non-limiting variations of a surgical method for using an atrial septal channel device according to one or moreembodiments disclosed herein.

[0053] Fig. 16 is a comparative bar chart illustrating an equivalent circular diameter of channels formed by six tested atrial septal channel devices, indicating the increased channel size produced in response to application of RF energy according to one or more embodiments disclosed herein.

[0054] Figs. 17A, 17B, and 17C illustrate a representative pediatric-sized atrial septal channel device and the open area of a channel produced without and subsequently with the application of RF energy from the atrial septal channel device according to one or more embodiments disclosed herein.

[0055] Figs. 18A, 18B, and 180 illustrate a representative adult-sized atrial septal channel device and the open area of a channel produced without and subsequently with the application of RF energy from the atrial septal channel device according to one or more embodiments disclosed herein.

[0056] Figs. 19A and 19B show images of an opening formed through atrial septal tissue before and after application of RF energy from a pediatric-sized atrial septal channel device according to one or more embodiments disclosed herein.

[0057] Figs. 20A and 20B show images of an opening formed through atrial septal tissue before and after application of RF energy from an adult-sized atrial septal channel device according to one or more embodiments disclosed herein.DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS

[0058] The following discussion is directed to various exemplary embodiments. However, one skilled in the art will understand that the examples and embodiments disclosed herein have broad application, and that the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to suggest that the scope of the disclosure, including the claims, is limited to that embodiment.

[0059] Certain terms are used throughout the following description and claims to refer to particular features or components. As one skilled in the art will appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name but not function. The drawing figures are not necessarily to scale. Certain features and components herein may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in interest of clarityand conciseness.

[0060] In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to....” Also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection, or through an indirect connection via other devices, components, and connections. In addition, as used herein, the terms “axial” and “axially” generally mean along or parallel to a central axis (e.g., the central axis of a body or a port), while the terms “radial” and “radially” generally mean perpendicular to the central axis. For instance, an axial distance refers to a distance measured along or parallel to the central axis, and a radial distance means a distance measured perpendicular to the central axis.

[0061] Disclosed herein are various embodiments of an atrial septal channel devices, for example, an atrial septal channel creation device and / or and atrial septal channel enlargement device, utilized interchangeably herein unless otherwise specified or dictated by context. In certain embodiments herein, the atrial septal channel device facilitates the specialized enlargement of a small opening defined through the atrial septum, such as an insufficiently sized existing opening or an opening created prior to use of the atrial septal channel device. Some embodiments of the atrial septal channel device may also provide for the creation of a relatively small opening or channel that is immediately expanded via the techniques disclosed herein, such as during a shared surgical procedure. The atrial septal channel device may employ one or more of multiple expansion mechanisms generally configured to transform the atrial septal channel device from an unexpanded configuration to an expanded configuration within the opening, which causes the opening to enlarge into a suitably sized atrial septal channel.

[0062] Generally, the atrial septal channel device may be configured to be deployed within the heart of a patient or subject via a minimally invasive procedure (through endovascular routes, or alternatively through a chest port for access) such as through a small-bore catheter or a hollow needle. In some embodiments, the catheter or needle has a diameter of from about 0.5 millimeters (mm) to about 6 mm and is positioned using ultrasound guidance. The atrial septal channel device may be expanded to mechanically create, define, and / or enlarge an opening in the atrialseptum, for example, so as to establish a stable opening of at least 3 mm, or from about 3 mm to about 15 mm, in the atrial septum. For example, at least a portion of the atrial septal channel device positioned within the atrial septum may have an expanded diameter of from about 3 mm to about 19 mm, or from about 4 mm to about 10 mm, or from about 5 mm to about 9 mm, or from about 6 mm to about 8 mm.

[0063] Additionally, in some embodiments, the atrial septal channel device may be configured to deliver radiofrequency (RF) energy, via a suitable waveform algorithm configured to direct energy to one electrode or a plurality of electrodes incorporated into the atrial septal channel device, to denature (e.g., ablate or degrade), for example, thermally, the tissue around (e.g., substantially proximate to a periphery of) the opening so as to reset a zero stress state of the tissue (e.g., erase the tissue memory), thus preventing closure of the opening and / or to further expand the opening. As disclosed herein, in some embodiments, the atrial septal channel device may comprise one or more electrodes disposed on or integrated within the atrial septal channel device and configured to provide targeted RF energy application directly to the tissue around the opening. The application of RF energy to septal tissue disclosed herein provides significant benefits, including reduced or negligible tissue recoil relative to a comparative procedure that lacks RF energy usage. As disclosed herein, the atrial septal channel devices that utilize RF energy may efficiently erase or reduce the tissue memory or elasticity that causes tissue recoil, enabling an established channel to remain open at a size that generally corresponds to the size of a septum-contacting portion of the atrial septal channel device. In some embodiments, this correlation enables practitioners to accurately and reliably produce enduring channels of a desired target diameter within an atrial septum based on the simple selection of the diameter of the utilized device.

[0064] In certain embodiments, the application of RF energy may be omitted, such as in certain embodiments in which the atrial septal channel device comprises an expandable stent that is installed within the atrial septal channel. In such embodiments, the self-expanding stent may be removed during a subsequent procedure, such as a particular growth milestone for a pediatric subject.

[0065] In some embodiments, the atrial septal channel device may be suitably employed for treating conditions in pediatric subjects, adult subjects, or both. For example, the atrial septal channel device may have applications in fetal surgery inconditions such as HLHS with l / RAS, as well in adult heart failure where left atrial decompression is desired. For fetal applications, the atrial septal channel device may be delivered through a small-bore catheter or hollow needle around 0.5-2 mm in diameter and the atrial septal channel device may create an opening around 3-7 mm in diameter. Adult applications may tolerate larger atrial septal channel devices that may be delivered through a larger catheter (up to 8 mm in diameter) and may create a larger opening (up to 15 mm in diameter). In either case, use of this small-sized catheter or needle for device deployment avoids issues with bleeding and / or loose tissue associated with potential alternative procedures such as a circle cutter, while simultaneously enhancing the creation of suitably sized atrial septal channels.

[0066] In some embodiments, the atrial septal channel device may be configured to apply the RF energy at a preselected frequency or range of frequencies. The atrial septal channel device may apply RF energy to the tissue surrounding the opening for a predetermined time period, such as an amount of time determined based on the age, weight, or other parameters (e.g., septum thickness) associated with the subject. In certain embodiments, the atrial septal channel device applies the RF energy in a closed control loop. For example, application of the RF energy may be halted in response to the septal tissue reaching an upper temperature threshold. The upper temperature threshold may be a critical transition temperature that causes the tissue to scar or immobilize and thus reduce recoil. In some embodiments, a temperature of the tissue is maintained below the boiling point of water. In some embodiments, the temperature of the tissue is closely monitored during device use to prevent or reduce any searing, charring, or overheating of the septal tissue. An operator of the atrial septal channel device may additionally or alternatively observe or detect a color change in the tissue and halt the RF energy application in response to the change.

[0067] Generally, in some embodiments, the RF energy may be delivered via one or more suitably-configured electrodes. For example, the atrial septal channel device may include a specifically-tailored arrangement of electrodes, as disclosed herein. For example, in some embodiments, the atrial septal channel device may utilize a monopolar electrode arrangement that directs energy through the subject and to a grounding component, such as an external grounding component positioned on the chest of a subject. Certain monopolar electrodes may be particularly suitable for adult subjects, for example, based on their body mass. Also for example, in someembodiments, the atrial septal channel device includes a bipolar or dipolar electrode modality or arrangement, in which a first electrode is separated from an oppositely charged second electrode by a specific spacing or gap, which may be correlated to a target rate of tissue heating. In some embodiments having a dipolar electrode modality or arrangement, the electrodes may enable the simultaneous or concurrent performance of tissue treatment and monitoring of the treatment. For example, the electrodes may provide real-time feedback regarding the electrical impedance or temperature of tissue in contact with the atrial septal channel device. In some embodiments, the atrial septal channel device monitors any suitable sensed parameter or variable from which a state or status of the tissue can be determined. In certain embodiments, the sensed parameter includes a temperature, an electrical impedance, a radial tissue force, and / or a radial tissue pressure.

[0068] In some embodiments, the atrial septal channel device may comprise and / or be associated with a suitably-configured controller. Generally, the controller may be configured to deliver to the one or more electrodes a signal configured to yield the RF energy. Additionally or alternatively, the controller may be configured to receive one or more signals from the one or more electrodes indicative of a parameter associated with the tissue being treated, as disclosed herein.

[0069] Generally, in various embodiments, the controller may comprise a microcontroller or microprocessors, suitable memory, and wireless communications modules (e.g., microchips or circuits), for example, suitable for communication via a desired communication interface. Additionally or alternatively, in some embodiments, the controller may comprise one or more integrated circuits comprising a suitable arrangement of transistors, LEDs, copper wires, tin-lead solder, ethylene tetrafluoroethylene (EFTE) coatings, or combinations thereof.

[0070] In some embodiments, the controller may be configured to carry out a desired functionality. For example, the controller may execute instructions stored in memory. The memory can include computer system readable media in the form of volatile memory, such as random-access memory (RAM) and / or cache memory. The memory may further include other removable / non-removable, volatile / non-volatile computer system storage media. As will be further depicted and described below, the memory may include at least one application configured to carry out the disclosed functionalities, for example, evaluation of a signal and / or communication with anexternal device. For example, an application may be stored in the memory and may include a set of application program modules (e.g. software). In some cases, the application may also include an operating system and program data. According to various embodiments, the application program modules may be assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state-setting data, or either source code or object code written in any combination of one or more programming languages, including an object oriented programming language such as Smalltalk, C++ or the like, and conventional procedural programming languages, such as the “C” programming language or similar programming languages.

[0071] Additionally, in some embodiments, the controller, or a processing unit thereof, may be configured for communication with an external device such as a mobile device (e.g., a smart-phone), a tablet, or a computer. For example, in various embodiments, the controller may comprise one or more communication modules configured to provide communication via wireless connection such as RF signals (Bluetooth, Wi-Fi, for example), inductive coupling, optical signaling, acoustic signaling, conducted communication signals, and / or any other signals suitable for communication.

[0072] In some embodiments, the external device or controller may comprise a user interface that allows a user to control and monitor the operation of the atrial septal channel device via the communication over the wireless connection. For example, the user interface may comprise a graphical user interface (GUI) that is displayed on a mobile device, a tablet, a computer, or the controller. In some embodiments, the user interface may be modifiable to meet the needs of different users or medical professionals. For example, the user interface may include different languages or font sizes to accommodate users with different backgrounds or visual impairments. The user interface may also include different modes or profiles for different types of functions or different users. The user interface may also include security features, such as passwords or biometric authentication, to ensure that only authorized users can access the atrial septal channel device. Additionally, the user interface may allow a user to monitor the atrial septal channel device, to adjust settings, and to view realtime data from the atrial septal channel device. The user interface may also provide alerts or notifications when the atrial septal channel device requires attention, such asa low battery alarm, or when certain conditions are met, such as when a treatment has concluded.

[0073] In some embodiments, the controller may be configured to cause an electrical signal be generated and delivered to one or more electrodes so as to cause the RF energy to be applied to the cardiac tissue. In various embodiments, a plurality of electrical leads may be connected between the controller and the atrial septal channel device, for example, to provide a route of electrical communication between the controller and each of the one or more electrodes. In various embodiments, the electrical leads may comprise or be made from a suitable signal-conducting material, for example, gold, platinum, copper, or any suitable alloys thereof. In some embodiments, the material of the electrical leads includes MP-35N and / or MP-35N with titanium, platinum, or platinum-iridium alloys.

[0074] In various embodiments, the atrial septal channel device may be characterized as self-positioning. For example, the atrial septal channel device may be configured such that, when positioned in the atrial septum, the atrial septal channel device exhibits a tendency to remain disposed in a desired position, for example, as originally deployed. As will be understood with reference to the following example embodiments, the atrial septal channel device may include at least one hinged or flanged end coupled to a middle body portion, such that the flanged end facilitates the targeted positioning of the atrial septal channel device within an opening defined through the atrial septum. For example, the atrial septal channel device may include one or two flanged sections or ends that radially expand when deployed to engage with respective sides of the atrial septum. In such embodiments, a surgeon may easily position the atrial septal channel device and activate an RF energy source thereof to selectively denature tissue and establish an enlarged atrial septal channel, which facilitates the proper, individualized blood circulation for any pediatric or adult subject.

[0075] Additionally, in some embodiments, the atrial septal channel device is configured as stent, for example, a self-expanding stent which may have flanged ends. Generally, the self-expanding stent may be configured such that, when deployed, the self-expanding stent exhibits a tendency to expand in diameter, for example, in a direction perpendicularto its longitudinal axis (e.g., perpendicular to a lumen generally defined by the self-expanding stent). The self-expanding stent may be formed from a metallic material or polymeric material. For example, the self-expanding stent may beformed from a shape-memory, superelastic alloy (e.g., Nitinol or an alloy such as 316 stainless steel) and / or a shape-memory polymer (including but not limited to polyorthoesters-lactide glycolides, caprolactones, and polyurethanes). Additionally or alternatively, in some embodiments, the flanged, self-expanding stent may comprise or be formed from polymers including, but not limited to, polypropylene, polytetrahydroxybutyrate, polytetrafluoroethylene, polyethylene, and combinations thereof.

[0076] In some embodiments, the self-expanding stent may also include one or two flanges that serve to locate the tissue over the electrodes described above. When deployed and upon delivery, the flanges may aid in device positioning and may be effective to minimize device migration.

[0077] In some embodiments, and as similarly disclosed herein, the self-expanding stent may be configured to deliver RF energy. For example, the self-expanding stent may comprise electrodes bonded to the stent or may use the stent itself as the electrode in the case of a metallic stent. The stent may be comprised of multiple rings which may each serve as separate electrodes. In various embodiments, the selfexpanding stent may be configured having a monopolar or a bipolar energy delivery modality and may employ similar energy control mechanisms as described herein with respect to various other embodiments.

[0078] Referring to Fig. 1 C, following placement of the delivery cannula in the left atrium, the self-expanding stent may be partially ejected to deploy the distal flange. The cannula may then be withdrawn until the flange is observed to contact the atrial septum via ultrasound visualization. With the distal flange in position, the selfexpanding stent is fully ejected while withdrawing the cannula. The self-expanding stent, now unconstrained, opens to its full diameter and creates or expands the atrial septal opening into a suitably sized channel. The atrial septal channel device has several advantages over the currently used coronary stents. First, the distal flange allows for a degree of self-location during stent placement, ameliorating otherwise challenging conditions for device visualization and positioning. Next, the atrial septal channel device is much shorter than a coronary stent which minimizes the chances of contact with the walls of the atria. Additionally, the flanges prevent stent migration while the atrial septum moves with each heartbeat. In some embodiments, the stent is designed to remain in position within a pediatric subject and later removed, forexample, until performance of a Norwood procedure, where the self-expanding stent is removed during the atrial septectomy. Lastly, for a given cannula size, a selfexpanding stent may be made larger than a balloon expanded one, which may aid in the creation of a larger septal defect and thus lead to better decompression of the left atrium.

[0079] Additionally or alternatively, in some embodiments, the atrial septal channel device comprises a mechanically expandable slotted tube, as illustrated in Fig. 4A, that may be shortened to cause the slotted section to expand, as illustrated in Fig. 4B. When shortened, the expanded configuration forms flanges that locate the tissue over the electrodes. The expander may be fabricated from a metallic or polymeric tube, for example, as otherwise disclosed herein, and shape-set to bias the expanded configuration in the desired flanged shape. The shortening may be achieved via application of a linear or helical motion. A similar expansion mechanism may also be achieved using a helical braided tube instead of a slotted one, in certain embodiments.

[0080] In some embodiments, to deliver RF energy to the septal tissue, electrodes may be bonded to the tines of the expander. This embodiment may also use monopolar or bipolar energy delivery modalities and employ similar energy control mechanisms as described herein with respect to various other embodiments.

[0081] Additionally or alternatively, in some embodiments, the atrial septal channel device comprises a single or double flanged balloon, which may share certain similarities to the currently used septostomy balloons, to expand and / or create the atrial septal defect. In some embodiments, the balloon may comprise one or two flanges. The flanged balloon, similar to the stent, self-locates, which eases the burden of skill for a surgeon. In various embodiments, the balloon may be made of a non- compliant, semi-compliant, or elastic material. For example, the balloon may be formed from a polyurethane, nylon, silicone, and / or polyethylene material.

[0082] In some embodiments, the balloon may include an electrode array bonded to its surface that may be used to deliver RF energy (e.g., electrical energy, which heats tissue in its proximity). Following placement of the delivery cannula in the left atrium, the balloon may be partially deployed and partially inflated. The cannula is then withdrawn until the balloon flange is observed to contact the atrial septum on ultrasound visualization. The balloon may then be fully deployed and inflated to open the atrial septal defect. With the flange in contact with the atrial septum, the electrodearray is configured to be in contact with the septal tissue in this position. RF energy may then be applied to the electrode array via an electrosurgery generator to cause heating and denaturation of the septal tissue, after which the balloon is deflated and withdrawn. With the tissue denatured in the expanded state, tissue recoil after balloon removal is minimized, thereby creating a larger channel in the atrial septum compared to traditional balloon septostomy, for example, as shown in Fig. 1 D.

[0083] Additionally, in contrast with stenting, the disclosed balloon-based approach leaves no foreign material in the heart. In some embodiments, the atrial septal channel device is configured to deliver the RF energy using a bipolar modality, for example, such that a substantial portion of the electrical current path is contained within the atrial septal channel device, minimizing potential risk to the patient.

[0084] As disclosed herein, the electrode array may be configured to use one of the two energy delivery modalities seen in electrosurgery: bipolar or monopolar. In some embodiments where bipolar is used, electric current flows from one set of electrodes, through tissue and returns to another set of electrodes. In some embodiments where monopolar is used, electric current flows from one set of electrodes, through tissue, and returns to an external grounding pad attached to the patient.

[0085] Not intending to be bound by theory, the bipolar modality may provide greater control over the complete current path, reducing risks to the patient. In this modality, a possible electrode array configuration is comprised of two interleaved electrode sets, as shown in Fig. 5A. The number, spacing, and dimensions of the electrodes may be varied to optimize RF energy delivery and manage the spread of thermal energy. For example, the electrodes may be configured with a linear configuration, a nonlinear interleaved configuration, or a curvilinear interleaved configuration. The electrode array may also be comprised of individually selectable electrodes, in which pairs of electrodes may be energized to deliver electrical energy to only the tissue between the selected electrodes. This customizability allows control over the localization of the thermal energy around the atrial septal channel device perimeter to reduce risks to cardiac structures and / or ensure even energy delivery. Electrodes may be selected in a predetermined sequence, randomly, or in response to measured tissue conditions (e.g., impedance, temperature, and / or a radial tissue force or pressure applied by the septal tissue).

[0086] In some alternative embodiments, instead of individual electrodes, the atrial septal channel device may employ single large electrodes that run along the circumference of at least a portion of the atrial septal channel device, as illustrated in Fig. 6A. The electrodes may be arranged on the balloon such that they contact opposite sides of the atrial septum. The width and spacing of the electrodes may be varied to optimize RF energy delivery.

[0087] In various embodiments, the electrode pair may also be comprised of two waveforms such as a sinusoid / zigzag that run along the circumference of at least a portion of the atrial septal channel device, as illustrated in Fig. 6B. The width, pitch, and amplitude of the waveforms may be varied to achieve a desired RF energy delivery. The waveforms may be sinusoid, triangle, square, sawtooth or a superimposition of multiple waveforms with varying pitch, amplitude, and width. The waveforms may also be generated by a mapping function.

[0088] In various embodiments, the electrodes may also be comprised of polygonal or ellipsoid shapes along the circumference of at least a portion of the atrial septal channel device in linear or tiled arrangements, as shown in Fig. 6C. In some embodiments, electrodes may also be enclosed within other electrodes. The array may be comprised of one or more rows of electrodes. The size, shape, number, and spacing of the shapes may be varied to achieve a desired RF energy delivery.

[0089] The electrode array may also be comprised of a combination of any of the previously described electrode configurations. For versions of the atrial septal channel device that use monopolar energy delivery modes, the two electrode sets seen in the bipolar version may be replaced by a singular electrode or electrode array.

[0090] In various embodiments, the electrode array may cover a percentage of the circumference of the atrial septal channel device, for example, from 10% to 99.9%, or from about 20% to about 80%. The width of the electrode array may be varied depending on the target atrial septum thickness and may range from 0.5 mm to 10 mm. The thickness of the electrodes in the radial direction may be varied to optimize the resistance of the electrical traces and may range from 0.01 mm to 1 mm. The array may also be asymmetric where a certain portion of the circumference may have variations in electrode dimensions / spacing or be devoid of electrodes to avoid damage to critical heart structures. In such cases, the atrial septal channel device would include radio-opaque or echogenic features on the expander or shaft that indicate deviceorientation.

[0091] Multiple features of the RF energy may be varied to achieve tissue denaturation and control thermal spread. Features under control may include voltage (100 V to 5000 V), power (0.1 W to 100 W), and frequency (50 kHz to 10 MHz). These features may also be temporally varied over the course of a single operation of the atrial septal channel device. Features may be varied in response to measured tissue conditions (e.g., impedance or temperature), a predetermined sequence, or a combination thereof. RF energy may be delivered for durations ranging from 0.05 seconds (s) to 120 s, additionally or alternatively, from 0.5 s to 20 s, additionally or alternatively, from 0.75 s to 10 s or, additionally or alternatively from 1 s to 5 s. The duration may be predetermined or varied in response to measured tissue conditions, for example, on the basis of changes in impedance and / or temperature exhibited by the tissue. In certain embodiments, the atrial septal channel device is activated in a sequence, such as for one or more respective predetermined time periods during a predetermined number of activation cycles. As an example, the atrial septal channel device may apply RF energy for a first predetermined time period, halt the RF energy application, and apply RF energy again for a second predetermined time period. Any suitable number of activation cycles, each having a respective time duration suited for precise tissue denaturation, may be performed by embodiments herein.

[0092] Additionally, in some embodiments of the balloon embodiment, the electrodes may be configured to hinge during the inflation of the balloon, for example, such that upon hinging the electrodes are brought into close contact with the atrial septum, as shown in Fig. 7A. In some embodiments, the hinging may also be achieved by using a balloon made of a compliant elastomeric material (e.g., silicone, polyurethane) with a sleeve or collar made of a non-compliant thermoplastic material (e.g., polyethylene terephthalate, nylon). In some embodiments, the sleeve is made of any suitable material having a greater rigidity and / or lower compliance than the remaining balloon material. The sleeve of certain embodiments may be integrated with the balloon material, such as within a three-piece construction having a first balloon portion, which is connected to a middle sleeve portion, which is connected to a second balloon portion. As shown in Fig. 7B, as the balloon is expanded the sleeve reaches its maximum size, thereby restricting further expansion of the balloon in that section, thus creating the hinging action, as shown in Fig. 7C. The electrodes may be bondedto either the balloon or sleeve. In certain embodiments, the balloon of the atrial septal channel device includes a curved outer surface that is coupled to a curved inner surface of a sleeve or sleeve member.

[0093] Additional embodiments of interleaved, dipolar electrode arrangements suitable for use with an atrial septal channel device are shown in Figs. 8A-8F. In particular, Figs. 8A-8D illustrate embodiments of interleaved electrode configurations sized for use within pediatric subjects. Figs. 8E and 8F illustrate embodiments of interleaved electrode configurations sized for use within adult subjects. These electrode configurations may be positioned to circumferentially surround the middle portion of an expandable balloon that is positioned in contact with an atrial septum, thereby blocking overexpansion in this area and providing for the localized delivery of RF energy for tissue denaturation.

[0094] Additional features regarding embodiments of a stent for use as an atrial septum channel enlargement device are disclosed herein. As described above, the stent of certain embodiments may be coupled with, or operates as, one or more electrodes that deliver RF energy to denature septal tissue and reduce recoil or shrinkage of the channel. Any component, feature, or combination thereof disclosed with reference to the following stent may be employed with corresponding components and / or features of the self-expanding stent, slotted tube mechanism, and / or expandable balloon described above.

[0095] Embodiments disclosed herein include additional, non-limiting examples of devices suitable for use in creating an atrial septal channel. In certain embodiments, these devices may be used with examples of RF energy delivering electrodes for denaturing tissue and reducing recoil. In other embodiments, the application of RF energy may be omitted, and the atrial septal channel devices may be retained within the atrial septal channel to physically maintain the channel at a desired diameter.

[0096] Referring to Fig. 9A, in some embodiments, the atrial septal channel device is configured as a stent 100 that comprises a first expansion segment 101 (e.g., flanged section) at a first end of the stent 100; a second expansion segment 105 (e.g., flanged section) at a second end of the stent 100; and a middle expansion segment 103 (e.g., cylindrical body section) between the first expansion segment 101 and the second expansion segment 105.

[0097] Referring to Figs. 9A-9B, in some embodiments, the stent herein has an nunexpanded state 100 and an expanded state 100’. Referring to Fig. 9A, in some embodiments, an unexpanded diameter of the first expansion segment 101 , an unexpanded diameter of the second expansion segment 105, and an unexpanded diameter of the middle expansion segment 103 are substantially the same or approximately equal to one another.

[0098] In some embodiments, the diameters as recited in this document are those of the average diameter. In some embodiments, the diameter of an expansion segment is measured at a cross-sectional plane perpendicular to the longitudinal direction of the expansion segment where the expansion segment is the widest, and measured from the center to the outer surface of the expansion segment.

[0099] Referring to Fig. 9B, in the expanded state of the stent 100’, each of the first expansion segment 101’, the second expansion segment 105’, and the middle expansion segment 103’ expands in dimensions in the vertical and horizontal directions, but not in the longitudinal direction.

[0100] In some embodiments, in the expanded state of the stent 100’, the expanded diameter of the first expansion segment 101’, and / or an expanded diameter of the second expansion segment 105’ are larger than an expanded diameter of the middle expansion segment 103’.

[0101] In some embodiments, in the expanded state of the stent 100’, the expanded diameter of the first expansion segment 101’, and the expanded diameter of the second expansion segment 105’ are substantially the same. In some embodiments, in the expanded state of the stent 100’, the expanded diameter of the first expansion segment 101’ is larger or smaller than the expanded diameter of the second expansion segment 105’ for less than about 30%, less than about 25%, less than about 20%, less than about 15%, less than about 10%, less than about 5%, or less than about 2%.

[0102] In some embodiments, a ratio of the expanded diameter of the first expansion segment 101’, or the expanded diameter of the second expansion segment 105’ to the expanded diameter of the middle expansion segment 103’ is about 1.5:1 or more, about 2:1 or more, about 2.5 or more, about 3:1 or more, or about 4:1 or more. In some embodiments, a ratio of the expanded diameter of the first expansion segment 101’, or the expanded diameter of the second expansion segment 105’ to the expanded diameter of the middle expansion segment 103’ is about 10:1 or less, about9:1 or less, about 8:1 or less, about 7:1 or less, about 6:1 or less, or about 5:1 or less. In some embodiments, a ratio of the expanded diameter of the first expansion segment 101’, or the expanded diameter of the second expansion segment 105’ to the expanded diameter of the middle expansion segment 103’ is about 1.5:1 , about 2:1 , about 2.5:1 , about 3:1 , about 4:1 , about 5:1 , about 6:1 , about 7:1 , about 8:1 , about 9: 1 , about 10: 1 , or any ranges therebetween.

[0103] In some embodiments, the stent may be characterized as having one or more of the following configurations: (A) the unexpanded diameter of first expansion segment, the second expansion segment, and the middle expansion segment ranges from about 0.7 mm to about 2 mm; (B) the ratio of the expanded diameter of the first expansion segment 101’, or the expanded diameter of the second expansion segment 105’ to the expanded diameter of the middle expansion segment 103’ ranges from about 1 .5:1 to about 5:1 ; (C) the expanded diameter the first expansion segment 101’, and / or the expanded diameter the second expansion segment 105’ ranges from about 6 mm to about 10 mm; and (D) the expanded diameter of the middle expansion segment 103’ ranges from about 2 mm to about 5 mm.

[0104] Referring to Figs. 9A-9B, in some embodiments, the stent 100 or 100’ further comprises a connector 107, 107’, 109, and / or 109’ at the first end or the second end thereof for attaching to a tip of a guide wire or a catheter. The surgical operations using the stents herein sometimes require the removal or repositioning of the stent. The connector simplifies the removal or repositioning of the stent from the patient. In some embodiments, the connector 107, 107’, 109, and / or 109’ comprises screw threads, such as male orfemale screw threads.

[0105] In some embodiments, the stent is hollow along a longitudinal direction. In some embodiments, first expansion segment, the second expansion segment, and / or the middle expansion segment are self-expanding. In some embodiments, the first expansion segment, the second expansion segment, and / or the middle expansion segment are expanded by an inflatable balloon. In some embodiments, the stent is prepared by carving, laser cutting, or otherwise forming a predetermined pattern on a tubular member formed of stent material. (See e.g., Figs. 10, 12, and 13).

[0106] In some embodiments, the stent is made from two or more pieces. In some embodiments, the stent further comprises a reinforcing element, such as a sleeve or a reinforcement mesh, that provides additional strength to the middle expansionsegment, such that the middle expansion segment can hold the opening introduced to a tissue at a desirable diameter without being compressed by the tissues surrounding the opening. (See e.g., Fig. 11 ). In some embodiments, the stent is made from at least one material selected from the group consisting of stainless steel, a cobalt chromium alloy, a nickel-titanium alloy, platinum, a tantalum alloy.

[0107] In some aspects, the present disclosure is directed to a method of introducing and maintaining an opening in a tissue. In some embodiments, the method comprises puncturing the tissue to form the opening; sending a stent across the tissue and expanding the stent; and keeping the opening open with the stent.

[0108] In some embodiments, when the opening is being held by the stent: the first expansion segment of the stent is on a first side of the tissue, the second expansion segment of the stent is on a second side of the tissue, and the middle expansion segment of the stent holds the opening at a predetermined size. In some embodiments, sending the stent across the tissue and expanding the stent comprises: sliding the unexpanded first expansion segment across the opening; expanding the first expansion segment on the first side of the tissue; expanding the middle expansion segment inside the opening; and expanding the second expansion segment on the second side of the tissue.

[0109] Additionally, in some embodiments, when the stent (e.g., the atrial septal channel device) is positioned within the opening, RF energy may be delivered to the tissue surrounding the atrial septal channel device, for example, via one or more electrodes disposed on the electrodes.

[0110] In some aspects, the present disclosure is directed to a method of treating, ameliorating, and / or preventing hypoplastic left heart syndrome (HLHS) in a subject in need thereof. In some embodiments, the subject is a fetal subject in mother’s womb. In some embodiments, the HLHS is characterized in intact or restrictive atrial septum (RS).[oom] In some embodiments, the method comprises: puncturing the atrial septum in the fetal subject to form an opening; sending the stent across the atrial septum and expanding the stent; and keeping the opening open with the stent. In some embodiments, when the opening is being held by the stent: the first expansion segment of the stent is in the left atrium of the heart, the second expansion segment of the stent is in the right atrium of the heart, and the middle expansion segment of thestent holds the opening at a predetermined size.

[0112] In some embodiments, sending the stent across the atrial septum and expanding the stent comprises: sliding the unexpanded first expansion segment across the opening; expanding the first expansion segment in the left atrium; expanding the middle expansion segment inside the opening; and expanding the second expansion segment in the right atrium. In some embodiments, the unexpanded first expansion is delivered across the atrial septum using a catheter system. In some embodiments, the method further comprises removing the stent from the heart.

[0113] Figs. 14A-14G describe a method of treating fetal HLHS patient with l / RAS in accordance with some embodiments. Referring to Fig. 14A, in the fetal patient, the atrial septum between the left and right atria are restricted or intact. Referring to Fig. 14B, to treat the condition, a catheter shaft 200 is moved across the maternal abdominal wall, the uterine wall, the fetal chest wall, and the fetal heart wall until the tip of the catheter is in proximity to the fetal atrial septum. A catheter needle 300 is moved forward along an interior of the catheter shaft, protruding out of the tip of the catheter shaft, and punctures the atrial septum. Referring to Fig. 14C, a stent 400 is moved along the interior of the catheter shaft until the first expansion segment of the stent protrudes out of the tip of the catheter shaft, passes through the opening, and enters the left atrium. Referring to Fig. 14D, the first expansion segment is expanded in the left atrium, such as by self-expansion. Referring to Figs. 14E-14F, the tip of the catheter shaft 200 is moved away from the opening, which gradually expose the middle expansion segment 405 and the second expansion segment 403 of the stent 400. The middle expansion segment 405 and the second expansion segment 403 expands via self-expansion. Thus, the middle expansion segment 405 holds the opening at a predetermined size, and the first and second expansion segments are expanded in the left and right atria, respectively, and restricts the movement of the stent 400. Referring to Fig. 14G, the fully expanded stent 400 opens the fluid communication between the left atrium and the right atrium. Figs. 15A, 15B, 15C, and 15D illustrate a non-limiting example of this surgical procedure implemented with the atrial septal channel devices described above.

[0114] In a later development stage, such as when the stent is no longer needed, a second surgical operation can be performed to remove the stent, which may allow the opening to close, as the heart development requires. For use with fetal subjects,the second surgical operation may be performed after the baby is born, removing the stent along with the atrial septum as part of the Norwood procedure, for example.EXAMPLES

[0115] To evaluate the feasibility of the atrial septal channel devices disclosed herein, analogues were created that would demonstrate the core functionality of the atrial septal channel devices in an atrial septum analogue.

[0116] An atrial septum analogue is formed from the fusion or adhesion of the septum primum and septum secundum and is primarily comprised of myocardium. While limited data exists on the thickness of the atrial septum in HLHS with IAS, a 1 mm septal thickness was chosen to represent a “thick” atrial septum for this study. Porcine heart (Animal Technologies Inc., Tyler, TX) was selected as a source of cardiac tissue on account of its ready availability. A Leica VT1000 S vibrating blade microtome (Leica Biosystems, Deer Park, IL) was used to create 1 mm thick slices of cardiac tissue from the ventricular walls of the porcine heart. The tissue slices were equilibrated in phosphate buffered saline (PBS) at 37°C for at least 15 minutes prior to device testing.EXAMPLE 1 - RF ENERGY BALLOON

[0117] An embodiment of a balloon device is envisioned to first dilate an opening in the atrial septum and then apply RF energy to mitigate tissue recoil. An electrode array bonded to a dilating mandrel, as shown in Fig. 5A, was used to simulate the operating principles of the atrial septal channel device for early feasibility evaluation. A 3.5 mm diameter mandrel with a 10° dilating tip was stereolithography 3D printed on the Formlabs Form 3B, commercially available from Formlabs in Somerville, Massachusetts using the Formlabs clear resin. An electrode array comprised of two interleaved electrode sets with three electrodes each, as shown in Fig. 5B, was cut from 25 micrometer (pm) thick stainless steel foil. Leads made from 38 gauge copper wire were soldered to each electrode set. The electrodes were bonded to adhesive tape at the upper and lower ends which was used to attach the array to the 3D printed mandrel. The wire leads were connected to the bipolar output of a Bovie 1250S electrosurgery generator, commercially available from Symmetry Surgical Inc. in Nashville, Tennessee.

[0118] The dilating tip of the test device was used to penetrate the atrial septal analogue, simulating the expansion of the balloon. The electrode array was then positioned across the atrial septum and the electrosurgery generator was activated at 20W for 3 seconds, denaturing the tissue. The electrode was then removed, and the tissue was photographed with a ruler in the plane of the tissue to measure the size of the created and enlarged opening, as shown Fig. 5C. The experiment was repeated on a second septal analogue without activation of the electrode array to evaluate the level of recoil that was prevented, as shown in Fig. 5D. The area of the opening created in each case was measured and the equivalent circle diameter was calculated.Results and Discussion - RF Energy Balloon

[0119] The balloon device simulator successfully enlarged a channel in the atrial septum analogue. The 3.5 mm device enlarged an opening to an effective circle diameter of 3.1 mm, which compares favorably to other stented channels. Without RF energy application, the resultant channel had an effective diameter of only 1.2 mm indicating significant tissue recoil akin to that seen in balloon atrial septostomy and validating the value of ablation or denaturation of the tissue adjacent to the surface electrodes.

[0120] While this early study shows promise for this device concept, certain challenges remain that may be improved or addressed in the engineering of this device. The heat affected zone created by the atrial septal channel device needs to be tightly controlled in consideration of the potential risk to the conductive apparatus of the heart from the proximity of the target zone to the atrioventricular (AV) node. Given the small size of the working channel available to the atrial septal channel device, the atrial septal channel device aims to use an electrode array without multiplexed control of the energy delivery to the electrodes. Generally, tissue impedance rises as the denaturation process progresses which will likely lead to a natural balancing of the energy delivery away from regions where the denaturation has advanced further. This study used a fixed RF energy delivery time, but the delivery time may be adjusted in actual use, such as based on the treated individual and / or within a closed control loop, given the large variability in atrial septal thickness and hence the volume of tissue that needs to be denatured. This may be achieved through monitoring of the net impedance through the atrial septal channel device to determinethe procedure endpoint. Additionally or alternatively, temperature sensors may be incorporated to directly measure tissue temperatures.

[0121] The adjustable energy delivery would also likely allow for greater consistency in the size of the atrial septal channel across a range of septum thicknesses compared to a purely mechanical stenting approach. A limitation of this approach stems from the proximity of the atrioventricular node to the procedure site. There is a risk of damage to the conductive apparatus of the heart when using this device and as such, the energy delivery and thermal spread will need to be carefully controlled to minimize this risk. While this feasibility test was conducted with air as the surrounding medium, given the influence of heat transfer on the performance of this device, a temperature controlled, flowing fluid test bed will be required to more accurately evaluate device function.EXAMPLE 2 - FLANGED, SELF-EXPANDING STENT

[0122] An embodiment of a flanged, self-expanding stent as disclosed herein, formed from nitinol, was fabricated using a commercially available self-expanding carotid stent, the 5 x 20 mm Cordis PRECISE® PRO Rx Nitinol Stent System (Cordis, Miami Lakes, FL). Three stent ring segments were cut from the atrial septal channel device by ablating the connecting links between stent segments using a laser welder (Laserstar iWeld 100 Joule, LaserStar Technologies Corporation, Orlando, FL). The three-ring stent was then mounted on a stainless steel mandrel and compressed between two polished stainless steel plates to splay the proximal and distal ends (e.g., rings) outwards. Stainless steel wire was used to tie down or circumferentially restrict the central ring to ensure that the bending occurred at the inter-segment links. This assembly was then placed in a 550°C furnace for 5 minutes to shape-set the stent in the new flanged design configuration before water quenching, as shown in Fig. 2. The stent was imaged in the axial and transverse direction, as illustrated in Figs. 3A and 3B, respectively. The stent was then radially crimped and transferred into a 16-gauge stainless steel delivery tube. The 16-gauge tube was used to avoid excessive plastic deformation during the loading process given that this particular embodiment of the stent was not designed for delivery through an 18-gauge cannula.

[0123] A 16-gauge pointed obturator was used to place the loaded delivery tube across the atrial septum analogue. An 18-gauge stainless steel tube was used as apusher to partially eject the atrial septal channel device until the distal flange was fully deployed, as illustrated in Fig. 3C. Next, the delivery tube was retracted until the flange was in contact with the tissue. The stent was then fully ejected while withdrawing the delivery tube across the tissue, completing the atrial septal channel device deployment. The stent was photographed axially with a ruler in-plane with the stent to measure the diameter of the opening established in the atrial septum analogue, as shown in Fig. 3D.Results and Discussion - Flanged Stent

[0124] The flanged, self-expanding stent was able to be deployed successfully and it was observed that the flange was effective to cause the stent to maintain contact with the tissue, reducing the degree of precision required in the positioning of the delivery tube. The stent created a 1 .7 mm diameter opening in the atrial septum. After removing the stent from the tissue, the free-expanded inner diameter of the stent was measured at 2.4 mm which is lower than the initial 4.2 mm inner diameter indicating deformation beyond the yield point of the material during crimping and loading. The results indicate that a flanged, self-expanding stent as disclosed herein may be used to create and enlarge or maintain an opening in the atrial septum. While the resultant channel was significantly smaller than the 2.5-3.5 mm diameter channels created in other atrial stenting efforts, the off-the-shelf stent used here had a free expanded diameter of only 2.4 mm. A stent engineered specifically for this application may be able to achieve significantly greater expanded diameters. One of the limitations of this approach is the need to accommodate the large variability in the thickness of the atrial septum across patients. This could impact the size of the channel produced by the atrial septal channel device on account of greater mechanical resistance to the selfexpansion with thicker septa. Additionally, the design will need to carefully control the maximum strain to avoid plastic deformation when crimped to the small diameters needed. For example, in some embodiments where the stent material is nitinol, which exhibits superelastic characteristics, tooling and manufacturing process controls may be optimized during the cold working and heat treatment / shape setting steps to ensure minimal excursions in the Af (Austenite finish temperature). Compared to a traditional straight stent, the flanged stent has secondary bend points between the flanged and straight sections which may be further optimized. The stent may also be optimizedwith respect to the stent geometric features to achieve the desired superelastic response, such as via finite element analysis during the detailed design of the stent to quantify the strains in these regions.

[0125] These results establish the feasibility of a flanged design and its associated benefits.EXAMPLE 3 - REBOUND TESTING FOR RF ENERGY BALLOON

[0126] Embodiments of atrial septal channel devices were constructed and tested to assess the effectiveness of the atrial septal channel device for selectively denaturing atrial septal tissue with RF energy to establish channels or through-holes of increased sizes. The tests aimed to demonstrate the performance of the atrial septal channel device based on measuring the difference in the size of an enlarged channel created with use of RF energy to minimize tissue recoil, as compared to channels created without the use of RF energy. The atrial septal channel devices were tested on the prepared atrial septum analogue derived from porcine cardiac tissue slices.

[0127] Six different atrial septal channel devices were prepared, each including a respective bipolar electrode configuration or array. The electrode configurations were prepared, fabricated as flexible printed circuit boards, and bonded to non-compliant dilation balloon catheters. The balloon dilation catheters were Hurricane RX Biliary Balloon Dilation Catheters, commercially available from Boston Scientific in Marlborough, Massachusetts. Four of the configurations were designed for a 4 mm balloon dilation catheter, corresponding to a pediatric balloon size, and the two of the configurations were designed for a 10 mm balloon dilation catheter, corresponding to an adult balloon size. These electrode configurations are shown in Figs. 8A-8F referenced above, illustrating a flat electrode length of 12.6 mm for the pediatric-sized configurations and a flat electrode length of 31 .4 mm for the adult-sized configurations. After the electrodes were bonded to a respective dilation balloon catheter, wire leads of the electrodes were connected to the bipolar output of a Bovie 1250S electrosurgery generator, commercially available from Symmetry Surgical Inc. in Nashville, Tennessee.

[0128] The experiments employed an 18-gauge chiba needle to create an initial puncture in the tissue and guide the atrial septal channel device across the puncture formed through the tissue. The balloon of the atrial septal channel device was theninflated with water to a target pressure of 6 atmospheres, held at this pressure for 10 seconds, and then deflated. The tissue was then imaged under a microscope to measure the area of the opening created in the tissue, without the application of RF delivery. Following this measurement, the balloon was reinserted through the channel, aligning the tissue with the electrodes of the atrial septal channel device. The electrodes were then energized to denature the tissue around the channel. For pediatric sizes, the generator output was set to 5 W, and the energy was applied for 5 seconds. For adult sizes, the output was set to 10 W and applied for 10 seconds. After applying RF energy, the balloon was deflated and the atrial septal channel device was withdrawn. The area of the resultant channel was then measured under a microscope. The areas of the channel, measured before and after application of RF energy, were converted to an equivalent circular diameter (ECD), representing the diameter of a circle that has the same area as the channel.

[0129] The experiment was repeated three times for each of the six electrode and balloon-based atrial septal channel devices, following this procedure on separate tissue slices. The ECD results for each atrial septal channel device were averaged across the three tests to provide clear visualization of the size difference visible before and after RF energy was applied. These results are illustrated in Fig. 16.Results and Discussion - Rebound Testing for RF Energy Balloon

[0130] As shown in the bar graph of results of Fig. 16, without application of RF energy, tissue rebound of the septal analogues resulted in a channel with an average ECD of less than half the diameter of the balloon that was used to create it. The average ECD of the channel for the two adult-sized experiments, labeled Adult 1 and Adult 2, was 4.08 mm when using the 10 mm balloon. The average ECD of the channel for the four pediatric-sized experiments, labeled Pediatric 1 , 2, 3, and 4, was 1 .99 mm when using the 4 mm balloon.

[0131] Fig. 17A is a photograph of a representative, pediatric-sized atrial septal channel device used during these experiments. Fig. 17B illustrates the channel formed by the device of Fig. 17A and its corresponding axes, DL0 and DL1 , used in determining the ECD when RF energy is not applied. Fig. 17C illustrates the subsequent increase in the channel size when RF energy is applied, such as based on the RF energy denaturing the tissue and reducing recoil. Additionally, Fig. 18A is aphotograph of a representative, adult-sized atrial septal channel device used during these experiments, and Figs. 18B and 18C illustrate the size of the channels produced by the device of Fig. 18A without RF energy applied and with RF energy applied, respectively.

[0132] With the application of RF energy, the ECD of the channels more than doubled for the same sized balloons of the atrial septal channel devices. In particular, the average ECD for the channel was 8.80 mm for the adult-sized experiments and was 4.33 mm for the pediatric-sized experiments. Application of RF energy therefore resulted in a five-fold increase in the area of the channel available for blood flow across the atrial septum in both the adult and the pediatric sizes. There was no statistically significant difference in the area of the channels produced for the electrode configurations in both adult and pediatric sizes, such that any of the electrode configurations of Figs. 8A-8F may be suitable for desired channel enlargement.

[0133] Accordingly, these experiments verify the effectiveness of the atrial septal channel devices in greatly reducing tissue recoil within an atrial septum, which increases the available area for blood flow across the atrial septum by a factor 5. The effectiveness of this technology is also robust against changes in the electrode configuration, with each of the tested designs performing similarly to others of the same size.

[0134] Further validation was provided by testing each of a pediatric-sized and adult-sized atrial septal channel device as fabricated herein on excised atrial septa from porcine hearts. Each device was placed through the fossa ovalis, activated to an enlarged diameter without RF energy application, and then imaged. These images are shown in Figs. 19A and 20A for the pediatric and adult devices, respectively. Subsequently, the devices were replaced within the fossa ovalis, activated to the enlarged diameter, and the electrodes were energized to deliver RF energy to the tissue. The images taken after RF energy application are shown in Figs. 19B and 20B for the pediatric and adult devices, respectively. This testing illustrates the success of the atrial septal channel devices in creating an opening in the atrial septal tissue, and the application of RF energy was once again seen to greatly increase the size of the created channel.

[0135] While embodiments of the disclosure have been shown and described, modifications thereof can be made by one skilled in the art without departing from thescope or teachings herein. The embodiments described herein are exemplary only and are not limiting. Many variations and modifications of the systems, apparatus, and processes described herein are possible and are within the scope of the disclosure. For example, the relative dimensions of various parts, the materials from which the various parts are made, and other parameters can be varied. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims. Unless expressly stated otherwise, the steps in a method claim may be performed in any order. The recitation of identifiers such as (a), (b), (c) or (1 ), (2), (3) before steps in a method claim are not intended to and do not specify a particular order to the steps, but rather are used to simplify subsequent reference to such steps.

Claims

CLAIMSWhat is claimed is:1 . A device for expansion of an atrial septal channel, wherein the device comprises: a cylindrical body section comprising a radiofrequency (RF) energy source; a first flanged section extending from a first end of the cylindrical body section and having a first diameter; and a second flanged section extending from a second end of the cylindrical body section and having a second diameter, wherein the device is configured to expand within the atrial septal channel to increase the first diameter of the first flanged section, increase the second diameter of the second flanged section, and position the RF energy source in contact with an inner surface of the atrial septal channel.

2. The device of claim 1 , wherein the first diameter, the second diameter, and a body diameter of the cylindrical body section are approximately equal when the device is in an unexpanded state, and wherein the first diameter and the second diameter are each larger than the body diameter when the device is in an expanded state.

3. The device of one of claims 1-2, wherein the device is configured to radially expand the first flanged section to engage with a first side of an atrial septum and configured to radially expand the second flanged section to engage with a second side of the atrial septum.

4. The device of one of claims 1-3, wherein the RF energy source comprises at least one electrode configured for delivery of RF energy to the inner surface of the atrial septal channel.

5. The device of one of claims 1-3, wherein the RF energy source is configured to deliver the RF energy for a predetermined time period or until a sensed parameter reaches a predetermined threshold.

6. The device of one of claims 1-5, wherein the RF energy source is configured to deliver the RF energy via a monopolar delivery modality or a bipolar energy deliverymodality.

7. The device of one of claims 1-6, wherein the RF energy source comprises a plurality of electrodes configured to deliver the RF energy.

8. The device of claim 7, wherein the plurality of electrodes comprises a first electrode having a first longitudinal length and a second electrode having a second longitudinal length, and wherein the first electrode is interleaved with the second electrode to overlap the first longitudinal length with the second longitudinal length around a circumference of the cylindrical body section.

9. The device of one of claims 1-8, wherein the device comprises an expandable balloon, wherein the expandable balloon forms the first flanged section and the second flanged section, and wherein the cylindrical body section comprises a sleeve member having a curved inner surface coupled to a curved outer surface of the expandable balloon.

10. The device of one of claims 1-8, wherein the device comprises a self-expanding stent having the cylindrical body section, the first flanged section, and the second flanged section.

11. The device of one of claims 1 -8, wherein the device comprises a slotted tube expansion mechanism having the cylindrical body section, the first flanged section, and the second flanged section.

12. A method for expansion of an atrial septal channel, the method comprising: disposing a device comprising a radiofrequency (RF) energy source in the atrial septal channel; expanding the device to position the RF energy source in contact with an inner surface of the atrial septal channel expanded by the device, position a first flanged section of the device on a first side of the atrial septal channel, and position a second flanged section of the device on a second side of the atrial septal channel; andapplying RF energy from the RF energy source to the inner surface to denature tissue of the atrial septal channel, erase tissue memory, and reduce tissue recoil.

13. The method of claim 12, wherein applying the RF energy comprises activating the RF energy source for a predetermined time period.

14. The method of claim 12, wherein applying the RF energy comprises activating the RF energy source for one or more respective predetermined time periods during a predetermined number of activation cycles.

15. The method of claim 12, wherein applying the RF energy comprises activating the RF energy source until a sensed parameter reaches a predetermined threshold, and wherein the sensed parameter comprises a temperature, an electrical impedance, a radial tissue force, or a radial tissue pressure.

16. The method of one of claims 12-15, wherein the device comprises a cylindrical body portion having a body diameter positioned longitudinally between the first flanged section and the second flanged section, and wherein expanding the device comprises increasing a first diameter of the first flanged section and increasing a second diameter of the second flanged section relative to the body diameter.

17. The method of one of claims 12-16, wherein the device comprises an expandable balloon and a sleeve disposed around the expandable balloon to enable selective expansion of the first flanged section and the second flanged section.

18. The method of claim 17, wherein the sleeve comprises the RF energy source.

19. The method of one of claims 12-16, wherein the device comprises a selfexpanding stent or a slotted tube expansion mechanism.

20. The method of claim 19, wherein the self-expanding stent or the slotted tube expansion mechanism comprises a metallic material configured to direct the RFenergy to the tissue of the atrial septal channel, and wherein the metallic material comprises the RF energy source.

21. The method of one of claims 12-20, wherein the RF energy source comprises a plurality of electrodes having a linear configuration, a nonlinear interleaved configuration, or a curvilinear interleaved configuration to deliver the RF energy via a bipolar energy delivery modality.

22. The method of one of claims 12-21 , wherein disposing the device in the atrial septal channel comprises delivering the device via a cannula, a catheter, or a delivery tube.

23. The method of one of claims 12-22, further comprising puncturing an atrial septum with a needle before disposing the device in the atrial septal channel.

24. A self-expanding stent for expansion of an atrial septal channel, wherein the stent comprises: a cylindrical body section having a body diameter; a first flanged section extending from a first end of the cylindrical body section and having a first diameter; and a second flanged section extending from a second end of the cylindrical body section and having a second diameter, wherein the first diameter, the second diameter, and the body diameter are approximately equal when the stent is in an unexpanded state, and wherein the first diameter and the second diameter are each larger than the body diameter when the stent is in an expanded state and positioned within the atrial septal channel.

25. The stent of claim 24, wherein the stent in the expanded state is configured to engage the first flanged section with a first side of an atrial septum and configured to engage the second flanged section with a second side of the atrial septum.

26. The stent of one of claims 24-25, wherein the self-expanding stent comprises anRF energy source comprising one or more electrodes configured to apply RF energy to an inner surface of the atrial septal channel to denature tissue thereof.

27. The stent of claim 26, wherein the RF energy source is configured to deliver the RF energy for a predetermined time period or until a sensed parameter reaches a predetermined threshold.

28. The stent of one of claims 26-27, wherein the RF energy source is configured to deliver the RF energy via a monopolar delivery modality or a bipolar energy delivery modality.

29. The stent of one of claims 26-28, wherein the RF energy source comprises a plurality of electrodes configured to deliver the RF energy.

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