Patent Description:
Some types of implantable medical devices (IMDs), such as cardiac pacemakers or implantable cardioverter defibrillators systems, may be used to provide cardiac sensing and therapy for a patient via one or more electrodes. Some IMDs include an implantable pulse generator that includes a housing that encloses electronic components, which may be configured to be implanted subcutaneously in the chest of the patient or within a chamber of a heart of the patient, as examples. IMDs having a pulse generator that is configured to be implanted within a chamber of the heart may be referred to as an intracardiac device or a leadless implantable medical device. A medical device retrieval system including a retrieval catheter may be used to retrieve an intracardiac device transvenously from an implant site within a heart of a patient. The intracardiac device and medical device retrieval system then may be withdrawn from the patient.

<CIT> relates to tether assemblies for medical device delivery systems.

<CIT> relates to a biostimulator retrieval system having a cincher tube.

<CIT> relates to delivery devices and methods for leadless cardiac devices.

<CIT> relates to a medical device delivery system with internal ribs and vents.

In general, this disclosure is directed to examples of tether assemblies of medical device retrieval systems and to techniques using such tether assemblies. Example tether assemblies may include a distal tether head assembly with an attachment mechanism configured to releasably attach to an attachment member of a medical device, e.g., an intracardiac device. Additionally, a tether assembly of a medical device retrieval system may include an elongate body between the distal tether head assembly and a proximal tether handle assembly. Additionally, a tether assembly of a medical device retrieval system may include a positioning element attached to the elongate body and/or the tether head assembly and configured to align the attachment mechanism of the tether head assembly with the attachment member of the medical device. The positioning element may include one or more components configured to maintain the alignment of the attachment mechanism with the attachment member while the tether head assembly extends towards attachment member. The techniques may include positioning a cup of a medical device retrieval system around a medical device and attaching the tether head assembly to the medical device within the cup, enabling removal of the medical device from the treatment site.

The retrieval system may include a catheter and a tether assembly. The catheter may comprise an elongated shaft defining a lumen. The tether assembly may comprise an elongate body, a tether head assembly attached to a distal end of the elongate body, and a positioning element fixedly positioned over the elongate body. The tether head assembly may comprise an attachment mechanism configured to releasably attach to an attachment member of a medical device. The positioning element may be configured to align the attachment mechanism with the attachment member when the tether head assembly is extended distally out of the lumen. The positioning element may comprise a distal end, a proximal end, and a length therebetween. The tether head assembly, elongate body, and positioning element may be movable within the lumen of the elongated shaft.

In some examples, the positioning element may be configured to position the tether head assembly concentrically within the elongated shaft, or to position the tether head assembly concentrically with a cup on a distal end of the catheter shaft when the tether head assembly and positioning element are at least partially extended distally out of the lumen. In some examples, the positioning element comprises a number of coils surrounding the elongate body, as well as the tether head assembly, where an inner diameter of the coils is approximately equal to an outer diameter of the tether head assembly or elongate body and an outer diameter of the coils is approximately equal to an inner diameter of the elongated shaft. As the tether head assembly extends outwards from the distal end of the elongated shaft and into the cup, a distal portion of the coils extends with the tether head assembly, while a proximal portion of the coils remains within a portion of the distal end of the elongated shaft. The body of the coils may hold the tether head assembly in alignment with an attachment member of a medical device within the cup.

In this manner, the tether assemblies described herein may reduce the time and complexity associated with a procedure to retrieve the medical device. In some examples, the tether assemblies described herein may reduce patient discomfort and a possibility of contamination of the medical device or other objects within the surgical field by reducing the amount of time that a catheter is within the body of the patient. In some examples, the tether assemblies described herein may provide one or more advantages to the functionality, reliability, robustness, manufacturability, and cost associated with such tether assemblies.

In another example, a method for using a tether assembly of a medical device retrieval system comprises positioning a distal end of a shaft of a catheter in close proximity with at least a portion of a medical device, including an attachment member; advancing a tether head assembly of a tether assembly out of a lumen defined by the shaft, wherein the tether head assembly comprises an attachment mechanism, and wherein the tether assembly comprises an elongate body, the tether head assembly at the distal end of the elongate body, and a positioning element fixedly positioned over the elongate body and configured to align the attachment mechanism with the attachment member when the tether head assembly is extended distally out of the lumen; releasably attaching an attachment mechanism of the tether head assembly to the attachment member of the medical device; and disengaging the medical device from tissue of a patient using the attachment member.

This summary is intended to provide an overview of the subject matter described in this disclosure. It is not intended to provide an exclusive or exhaustive explanation of the apparatus and methods described in detail within the accompanying drawings and description below. Further details of one or more examples are set forth in the accompanying drawings and the description below.

In general, this disclosure describes example medical device retrieval systems. Such medical device retrieval systems may include a tether assembly comprising a tether head assembly, tether handle assembly, a positioning element, and an elongate body. The tether head assembly is attached to the elongate body and configured to releasably retain an attachment member of a medical device (e.g., an intracardiac device) via an attachment mechanism connected to a pull wire. In some examples, a tether handle assembly is configured to retain the pull wire attached to the tether head assembly. In some examples a positioning element is configured to align the attachment mechanism of the tether head assembly with the attachment member of the medical device. The tether handle assembly may include an actuator configured to transmit force to the tether head assembly via the pull wire and enable attachment of the attachment member of a medical device to the attachment mechanism of the tether head assembly at a treatment site within a patient. Once attached, the tether head assembly may be used to extract the medical device from patient tissue.

Although the example tether assemblies are generally described herein as being configured for retrieving an implantable medical device (IMD) from within the heart, e.g., an intracardiac pacemaker, it should be understood that any of the example tether assemblies described herein alternatively may be configured for retrieving medical devices implanted in other locations, other types of medical devices, or other types of devices that may or may not be implanted within a patient.

<FIG> is a conceptual drawing illustrating portions of patient anatomy including potential implant sites for an IMD. For example, an IMD may be implanted on or within heart <NUM> of a patient, such as within an appendage <NUM> of a right atrium (RA), within a coronary vein (CV) via a coronary sinus ostium (CSOS), or in proximity to an apex <NUM> of a right ventricle (RV). In other examples, an IMD may be implanted on other portions of heart <NUM> or implanted in locations other than heart <NUM>, such as any suitable implant site in a body of the patient. <FIG> also illustrates an inferior vena cava (IVC) and superior vena cava (SVC).

<FIG> is a plan drawing illustrating an example medical device retrieval system <NUM> for retrieving an IMD (not shown in <FIG>) from a location within heart <NUM>. Although described herein in the context of retrieving an IMD from the vasculature, e.g., heart <NUM>, the devices, systems, and techniques of this disclosure may be used to retrieve an IMD from any anatomical location.

System <NUM> includes an introducer <NUM>, a retrieval catheter <NUM>, and a tether assembly <NUM>. Introducer <NUM> is an elongated member defining an interior lumen. Introducer <NUM> is configured to be inserted, such as by a physician, into a vasculature of a patient to provide a rigid channel, via the interior lumen, through which to retrieve a medical instrument, device, or deliver a therapy.

Retrieval catheter <NUM> is configured to be inserted through the lumen of introducer <NUM> to retrieve an IMD within the vasculature. Retrieval catheter <NUM> includes an elongated shaft <NUM>, a handle <NUM>, and a device cup or chamber <NUM>. Handle <NUM> is disposed at a proximal end of shaft <NUM>, and may include one or more elements (such as buttons, switches, etc.) configured to control the motion or function of the distal end of shaft <NUM>.

Device cup <NUM> is disposed at a distal end of shaft <NUM>. Device cup <NUM> includes a hollow cylindrical body configured to house and support an IMD (e.g., IMD <NUM> described with respect to <FIG>) while the IMD is being retrieved from a vasculature of a patient. For example, a physician may insert the distal end of retrieval catheter <NUM>, including device cup <NUM>, through the lumen of introducer <NUM>, which is disposed within a vasculature of a patient. Once device cup <NUM> has extended through the distal end of introducer <NUM> and reached an implant site within the patient, the physician may position device cup <NUM>, through distal opening <NUM>, around an IMD implanted within the patient. In some examples, a physician may position cup <NUM> around an IMD through use of a snare as described below. A tether head assembly and positioning element (not shown in <FIG>) may assist a physician to disengage the IMD from the patient's tissue at the implant site, after which the IMD and retrieval catheter <NUM> may be withdrawn proximally through introducer <NUM>. In some examples, the IMD is repositioned and implanted at a new implant site within the patient rather than fully withdrawn, after which retrieval catheter <NUM> may be withdrawn.

Tether assembly <NUM> extends through a lumen defined by retrieval catheter <NUM>, e.g., including handle <NUM> and shaft <NUM>. Tether assembly <NUM> defines an elongate body <NUM>, a tether handle assembly <NUM> at a proximal end of elongate body <NUM>, and a tether head assembly <NUM> (<FIG>) at a distal end of elongate body <NUM>. Elongate body <NUM> may have sufficient length that a clinician may advance tether assembly <NUM> through the lumen defined by retrieval catheter <NUM> and to an implant site of an IMD. A pull wire (not shown in <FIG>) may extend from tether handle assembly <NUM> to tether head assembly <NUM> through a lumen defined by elongate body <NUM>.

A clinician may advance retrieval catheter <NUM> through introducer <NUM> and into the vasculature to the implant site. The clinician may also advance a snare through the catheter, where the snare may be of sufficient length that the clinician may advance a distal end of the snare out of distal opening <NUM> of cup <NUM> and attach it to a portion of an IMD implanted in the patient, e.g., by placing a distal loop of the snare around an attachment member of the IMD and drawing the distal loop tight around the attachment member. In some examples, the snare may be used to pull the IMD from the implant site and into cup <NUM> where it can be safely removed from the body, along with the snare and retrieval catheter. In some examples, the snare may be used to guide cup <NUM> around the IMD without removing the IMD from the patient's tissue. Once the IMD is within cup <NUM>, the snare may be detached from the IMD and proximally withdrawn from the catheter. Thereafter, the clinician may advance tether head assembly <NUM> of tether assembly <NUM> distally through the catheter to cup <NUM>, whereupon the clinician manipulates tether handle assembly <NUM> to attach an attachment mechanism of tether head assembly <NUM> to an attachment member of the IMD. In order to align the attachment mechanism of tether head assembly <NUM> with an attachment member of the IMD, a positioning element may be fixedly positioned over elongate body <NUM> proximal to tether head assembly <NUM>. Positioning element <NUM> may be fixedly positioned over elongate body <NUM> by connecting to tether head assembly <NUM> or elongate body <NUM> any of a variety of techniques, such as welding, crimping, threading, reflowing, overmolding, bonding, adhesives, or friction fits. The clinician may use tether head assembly <NUM> to disengage the IMD from the tissue of the patient and withdraw it along with retrieval catheter <NUM>. In some examples, after the IMD is disengaged from the patient's tissue, the IMD is repositioned and implanted at a new implant site within the patient using retrieval catheter <NUM>, rather than fully withdrawn.

<FIG> is a conceptual drawing illustrating, in conjunction with tissue <NUM> of heart <NUM>, a distal portion of the example medical device retrieval system of <FIG> retrieving an example IMD <NUM>. IMD <NUM> may be a pacemaker device having a housing <NUM> that contains electronic components suitable for performing a variety of pacing functions. However, IMDs configured to deliver other types of electrical therapy to a patient may be adapted for use with retrieval system <NUM>. IMD <NUM> may include an attachment member <NUM> at a proximal end thereof and fixation members <NUM> at a distal end thereof. Tether head assembly <NUM> may be configured to receive and retain attachment member <NUM>, as further discussed below with respect to <FIG>.

In some examples, IMD <NUM> may include a hermetically sealed housing <NUM> defining a proximal end <NUM> and a distal end <NUM>. Housing <NUM> may contain a pulse generator and an associated power supply (not shown) and an electrode <NUM>, which may be positioned at distal end <NUM> of housing <NUM> and which may be electrically coupled to the pulse generator of IMD <NUM> via a hermetically sealed feedthrough assembly (not shown). Housing <NUM> may be formed from any suitable biocompatible and biostable metal. For example, housing <NUM> may be formed from titanium and may be overlaid with an insulative layer (e.g., a medical grade polyurethane, parylene, or silicone). In some examples, IMD <NUM> may include a housing electrode <NUM>, which may be formed by removing a portion of the insulative layer to expose a metallic surface defined by housing <NUM>. In such examples, housing electrode <NUM> of IMD <NUM> may function in conjunction with electrode <NUM>, such as for bipolar pacing and sensing. In some examples, fixation member <NUM> may be an extension of electrode <NUM> and may pierce the tissue of the patient to hold IMD <NUM> in place at the implant site.

Fixation member <NUM> of IMD <NUM> may be configured to embed into tissue <NUM> but be removable through application of a specific force. For example, fixation member <NUM> may comprise a screw-shaped fixation structure that may be rotated out of tissue at an implant site. While IMD <NUM> is shown having fixation member <NUM> that includes a screw-shaped fixation structure (helix), it should be understood that IMD <NUM> may include any other suitable fixation structure or structures, such as a plurality of tine structures.

A clinician may position the distal portion of a medical device retrieval system in close proximity with an IMD <NUM> using a snare or similar retrieval mechanism. For example, a clinician may advance retrieval catheter <NUM> towards the implant site in tissue <NUM> until a distal end of catheter <NUM> is in close proximity to IMD <NUM>. In some examples, retrieval catheter <NUM> may comprise a cup <NUM> on a distal end of shaft <NUM>, where the interior of cup <NUM> is in fluid communication with a lumen defined by shaft <NUM>, as shown in <FIG>. A clinician may advance retrieval catheter <NUM> distally towards the implant site until the distal opening <NUM> of cup <NUM> is in close proximity to IMD <NUM>. The distal end of a shaft of retrieval catheter <NUM>, or distal opening <NUM> may be in close proximity with IMD <NUM>, when an attachment mechanism of tether head assembly <NUM> may reach and attach to IMD <NUM> when extended distally out of the lumen defined by shaft <NUM>. Then the clinician may advance a snare through the catheter shaft. The clinician may attach the distal end of the snare to one or more members or portions of IMD <NUM> (e.g., the attachment member <NUM>, shroud <NUM>), apply tension to the snare, and advance cup <NUM> over at least a portion of IMD <NUM>, through distal opening <NUM>, using the snare as a guide.

<FIG> illustrates the distal end of cup <NUM> of retrieval catheter <NUM> pressed against tissue <NUM> at the implant site of heart <NUM>. When a clinician is satisfied with the positioning of cup <NUM> with respect to tissue <NUM>, e.g., that a longitudinal axis of cup <NUM> is generally orthogonal to a plane defined by tissue <NUM>, and that cup <NUM> is pressed sufficiently against/into tissue <NUM> such that fixation member <NUM> of IMD <NUM> can be disengaged from the tissue, the clinician may detach the snare from IMD <NUM> and remove the snare from retrieval catheter <NUM>. In some examples, cup <NUM> may not need to be pressed against tissue <NUM>, and it may be sufficient for removal of IMD <NUM> that only a portion of IMD <NUM> is within cup <NUM>. The clinician may replace the snare with tether assembly <NUM>, including positioning element <NUM>, and advance tether head assembly <NUM> towards distal cup <NUM> using tether assembly <NUM>, e.g., by using tether assembly handle <NUM> to advance tether assembly <NUM> distally relative to retrieval catheter <NUM>. In some examples, the physician may use a snare in conjunction with tether assembly <NUM>, including positioning element <NUM>, and need not remove and replace the snare before advancing tether assembly <NUM>.

Once tether head assembly <NUM> reaches the distal end of elongated shaft <NUM>, a clinician may advance tether head assembly <NUM> distally out of elongated shaft <NUM> and into cup <NUM>. Positioning element <NUM> aligns an attachment mechanism of tether head assembly <NUM> to attachment member <NUM> while clinician attaches the attachment mechanism of tether head assembly <NUM> to attachment member <NUM> of IMD <NUM>. Thereafter, the clinician may be able to disengage IMD <NUM> from the implant site and move tether assembly <NUM> proximally, as described in greater detail below, withdrawing retrieval catheter <NUM>, tether assembly <NUM>, and IMD <NUM> from the patient through introducer <NUM>. In some examples, after IMD <NUM> is disengaged from the implant site, IMD <NUM> is repositioned and implanted at a new implant site within the patient using retrieval catheter <NUM>, rather than fully withdrawn.

In some examples, the attachment mechanism of tether head assembly <NUM> may be configured to automatically latch on to attachment member <NUM>, e.g., via distal advancement of tether head assembly <NUM> against attachment member <NUM>. In other examples, the clinician may need to operate attachment mechanism of tether head assembly <NUM> by manipulation of an actuator of tether handle assembly <NUM>. For example, tether assembly <NUM> may include a pull wire <NUM> (not shown in <FIG>) as discussed in further detail with respect to <FIG>. Pull wire <NUM> may be attached at a distal end thereof to tether head assembly <NUM> and attached at a proximal end thereof to tether handle assembly <NUM>.

The clinician may apply force to an actuator of tether handle assembly <NUM> to cause tether head assembly <NUM> to move from a closed position to an open position. In a closed position, attachment member <NUM> may either be retained within tether head assembly <NUM> or prevented from entering or attaching to tether head assembly <NUM>. In an open position, attachment member <NUM> may be attached to or released from tether head assembly <NUM>. With tether head assembly <NUM> in the open position, the clinician may distally move tether assembly <NUM> to releasably attach tether head assembly <NUM> to attachment member <NUM>. In some examples, the attachment mechanism of tether head assembly <NUM> may be able to open when force is applied to the attachment mechanism in one direction, but not another. For example, the clinician may secure attachment member <NUM> of IMD <NUM> to tether head assembly <NUM> by pressing attachment member <NUM> into a passageway defined by tether head assembly <NUM>, thereby opening tether head assembly <NUM> from a first (e.g., closed) position to a second (e.g., open) position and advancing attachment member <NUM> through the passageway until attachment member <NUM> is received within a receptacle defined by tether head assembly <NUM>, as further discussed below with respect to <FIG>. Once attachment member <NUM> is fully within the receptacle, the attachment mechanism of tether head assembly <NUM> may automatically return to the closed position. This may be accomplished by one clinician instead of the two clinicians that may be required to secure an attachment member of an IMD to a tether assembly in some other example medical device retrieval systems. Thus, tether assembly <NUM> may reduce the time and complexity associated with a procedure to deliver and/or retrieve IMD <NUM>. In some examples, tether head assembly <NUM> may reduce a possibility of contamination of the medical device or other objects within the surgical field, relative to such other tether assemblies, by reducing the number of people that touch IMD <NUM> and tether head assembly <NUM>.

As described herein, a clinician may secure attachment member <NUM> of IMD <NUM> to tether head assembly <NUM> at the time of a medical procedure to retrieve IMD <NUM>. In addition, the clinician may release IMD <NUM> from tether head assembly <NUM> without cutting a portion of tether assembly <NUM>. In some examples, tether head assembly <NUM> thus may reduce or eliminate drawbacks that may be associated with other types of tether mechanisms, such as tension associated with pulling on such other tether mechanisms (e.g., a loop of string or similar material), potential twisting or binding of such other tether mechanisms, or the like. The re-usability of tether assembly <NUM> may mitigate shelf-life considerations with respect to tether assembly <NUM>, retrieval system <NUM>, and IMD <NUM>, such as in examples in which IMD <NUM> includes a drug eluting component with a finite shelf life. For example, tether assembly <NUM> and/or retrieval system <NUM> may not necessarily be associated with a finite shelf life when packaged separately from IMD <NUM>.

<FIG> are conceptual drawings of a distal portion of tether assembly <NUM> including tether head assembly <NUM> and elongate member <NUM>. <FIG> respectively illustrate the distal portion of tether assembly <NUM> without and with positioning element <NUM>.

As illustrated in <FIG>, elongate body <NUM> may include a shaft defining a lumen (not shown) in which at least a portion of a pull wire <NUM> is received. Tether head assembly <NUM> may include inner retainer <NUM>, an outer retainer <NUM>, and a sheath <NUM>. Components of tether assembly <NUM> may be separately formed of any suitable material. In some examples, one or more of pull wire <NUM>, inner retainer <NUM>, outer retainer <NUM>, sheath <NUM>, and/or one or more layers of elongate body <NUM> may be formed of an electrically conductive material, which may help enable testing of placement of IMD <NUM> during a procedure to deliver IMD <NUM> (and/or retrieve IMD <NUM>, e.g., based on the result of such placement testing or other testing), as discussed above with respect to <FIG>. One or more components of tether assembly <NUM> may be manufactured via a technique such as metal injection molding or any other suitable technique.

Inner retainer <NUM> may be coupled to pull wire <NUM> and extends distally from a distal end (not shown) of pull wire <NUM>. Outer retainer <NUM> defines an aperture that includes a receptacle <NUM> dimensioned to receive attachment member <NUM> of IMD <NUM> through passageway <NUM>. When inner retainer <NUM> is in a first position, passageway <NUM> may be dimensioned to prevent passage of attachment member <NUM> of IMD <NUM> (e.g., is too narrow to allow passage of attachment member <NUM>, either into or out of receptacle <NUM>, or both).

Proximal movement of pull wire <NUM> may cause movement of inner retainer <NUM> from the first position to a second position in which inner retainer <NUM> does not extend into passageway <NUM>. Additionally, or alternatively, an application of force to inner retainer <NUM>, e.g., to a distal end of inner retainer <NUM>, by attachment member <NUM> of IMD <NUM> may cause inner retainer <NUM> to move from the first position to the second position. With inner retainer <NUM> in the second position, passageway <NUM> may be dimensioned to receive attachment member <NUM> and allow attachment member <NUM> to pass therethrough. Inner retainer <NUM> and outer retainer <NUM> may be received within sheath <NUM>, which may help retain inner retainer <NUM> within outer retainer <NUM> and couple outer retainer <NUM> to elongate body <NUM>.

Tether head assembly <NUM> may be rotatable around a centerline of the elongate body <NUM>, or of retrieval catheter <NUM>. In this way, tether head assembly <NUM> may be rotated into the correct orientation in order to attach to attachment member <NUM> of IMD <NUM>. In some examples, once tether head assembly <NUM> is attached to attachment member <NUM>, a clinician may rotate tether head assembly, thereby rotating IMD <NUM> and unscrewing helical fixation member <NUM> from tissue <NUM>. Accordingly, in such examples tether head assembly <NUM> is configured to make a torque-transmitting connection to attachment member <NUM> and IMD <NUM>, and thereby act as a driver to facilitate removal of IMD <NUM> via unscrewing.

In some examples, tether head assembly <NUM> and attachment member <NUM> may depart from the configuration depicted in <FIG>. Attachment member <NUM> may comprise a handle, nut, or other member with a profile which can be gripped on its external perimeter in a manner that facilitates torque transmission between tether head assembly <NUM> and attachment member <NUM>, and the distal end of tether head assembly <NUM> can comprise an attachment mechanism in the form of a matching socket which receives attachment member <NUM> in a closely fitting manner that facilitates torque transmission. In some examples, a physician may attach a snare to attachment member <NUM> and use the snare to guide the closely fitting socket of the attachment mechanism of tether head assembly <NUM> around the external perimeter of attachment member <NUM> to facilitate torque transmission between tether head assembly <NUM> and IMD <NUM>. In some implementations, attachment member <NUM> may have an oval profile in a plane orthogonal to its longitudinal axis, and the distal end of tether head assembly <NUM> can comprise a matching oval socket, or attachment member <NUM> may have a triangular, square, rectangular, pentagonal, hexagonal, or other polygonal profile, or a notched circular or notched oval profile, or an oblong profile, and tether head assembly <NUM> can comprise a socket having a matching shape. Optionally, in any of these implementations, attachment member <NUM> may have a narrowed portion or neck located distal of the aforementioned profile (see, e.g., <FIG>) to facilitate gripping attachment member <NUM> via a snare, and/or tether head assembly <NUM> can incorporate features for receiving and retaining a pin or crossbar of attachment member <NUM>, as discussed elsewhere herein.

In some examples, attachment member <NUM> may comprise a recess or hole through which the attachment mechanism of tether head assembly <NUM> may be inserted. The attachment mechanism may comprise a profile which can be gripped on its external perimeter in a manner that facilitates torque transmission between tether head assembly <NUM> and attachment member <NUM>. Accordingly, in such examples the clinician can make a torque-transmitting connection of tether head assembly <NUM> to attachment member <NUM> and IMD <NUM>, and thereby use tether head assembly <NUM> as a driver to facilitate removal of IMD <NUM> via unscrewing.

As illustrated by <FIG>, positioning element <NUM> may have a length that defines a distal end <NUM> and a proximal end <NUM>. The length of positioning element <NUM> is less than a length of elongate body <NUM>.

Tether head assembly <NUM> may have an outer diameter sufficiently similar to an inner diameter of elongated shaft <NUM> that tether head assembly <NUM> may advance normally through elongated shaft <NUM> without catching or bending. However, cup <NUM> may have an inner diameter significantly larger than the outer diameter of tether head assembly <NUM>, such that when tether head assembly <NUM> is advanced distally out of elongated shaft <NUM> and into cup <NUM>, elongate body <NUM> may bend or tilt such that an attachment mechanism of tether head assembly <NUM> no longer aligns with attachment member <NUM> of IMD <NUM>. For example, attachment member <NUM> may be a bar configured to fit into receptacle <NUM>, but when tether head assembly <NUM> enters cup <NUM>, elongate body <NUM> may tilt or deflect relative to the centerline of cup <NUM>, pointing passageway <NUM> away from the bar of attachment member <NUM>.

Positioning element <NUM> is configured to align the attachment mechanism of tether head assembly <NUM> with attachment member <NUM> when tether head assembly <NUM> extends into cup <NUM>. For example, positioning element <NUM> may be positioned over sheath <NUM> and/or elongate body <NUM>, with an outer diameter approximately equal to an inner diameter of elongated shaft <NUM>. As tether head assembly <NUM> is advanced into cup <NUM>, distal end <NUM> of positioning element <NUM> may also advance into cup <NUM>, while proximal end <NUM> may remain within elongated shaft <NUM>. Positioning element <NUM> may be firm such that as distal end <NUM> advances out of elongated shaft <NUM> and into cup <NUM>, positioning element <NUM> does not bend, or bends minimally. Although positioning element <NUM> is described as "firm," it may be flexible enough to bend as it passes through elongated shaft <NUM> to allow a physician to manipulate tether head assembly <NUM> with positioning element <NUM> through elongated shaft <NUM> to an implant site. Because proximal end <NUM> remains within elongated shaft <NUM>, the inner walls of elongated shaft <NUM> may prevent distal end <NUM> of the positioning element <NUM> from leaving a centerline of the elongated shaft, extending radially from the distal end of elongated shaft and into cup <NUM>.

Although the example positioning element <NUM> in <FIG> is depicted as a coil, positioning element <NUM> may take on many forms capable of aligning tether head assembly <NUM> with attachment member <NUM>. For example, positioning element <NUM> may comprise a hollow cylinder attached to elongate body <NUM>, where the hollow cylinder has an internal diameter approximately equal to an outer diameter of elongate body <NUM> and the hollow cylinder has an outer diameter approximately equal to an inner diameter of elongated shaft <NUM>. In another example, as described further in <FIG> below, positioning element <NUM> may comprise a series of fins extending radially away from elongate body <NUM> until they reach the inner walls of elongated shaft <NUM>. In some examples, positioning element <NUM> circumferentially encompasses elongate body <NUM> and/or sheath <NUM>. In some examples, positioning element <NUM> only surrounds a portion of the circumference of elongate body <NUM> and/or sheath <NUM> as shown in <FIG>. In another embodiment, positioning element <NUM> can comprise a proximal extension of tether head assembly <NUM>, e.g., a proximal extension of sheath <NUM> of tether head assembly <NUM>.

In some examples, as depicted in <FIG>, positioning element <NUM> may be configured to align tether head assembly <NUM> concentrically within elongated shaft <NUM>. In examples wherein the interior of cup <NUM> is in fluid communication with a lumen defined by shaft <NUM>, the inner diameter of cup <NUM> is approximately equal to the outer diameter of IMD <NUM>, and the inner diameter of cup <NUM> is configured to be concentric with the outer diameter of IMD <NUM> when cup <NUM> is positioned around IMD <NUM>, wherein attachment member <NUM> of IMD <NUM> lies at least partially along the centerline defined by the concentricity. Cup <NUM> may also be concentric with elongated shaft <NUM> of retrieval catheter <NUM>, which in turn is concentric with tether head assembly <NUM>, where an attachment mechanism of tether head assembly <NUM> lies at least partially along the centerline of elongated shaft <NUM>. In this way, when tether head assembly <NUM> is advanced outward from the distal end of elongated shaft <NUM> along the centerline of elongated shaft <NUM> and into cup <NUM> with the aid of positioning element <NUM>, the attachment mechanism of tether head assembly <NUM> will align with attachment member <NUM>.

In other examples, cup <NUM>, IMD <NUM>, elongated shaft <NUM>, tether head assembly <NUM>, and positioning element <NUM> may not share a concentric centerline. In these examples, positioning element <NUM> may be configured to align the attachment mechanism of tether head assembly <NUM> with attachment member <NUM> by compensating for any lack of concentricity between the elements. For example, a lack of concentricity between the aforementioned elements may result in the attachment member <NUM> of IMD <NUM> lying one millimeter away from the centerline of elongated shaft <NUM> as extended into cup <NUM>. However, positioning element <NUM> may have a shaft spanning its length defining a lumen, where the shaft and lumen are not concentric with an outer diameter of positioning element <NUM>, but where the outer diameter is concentric with elongated shaft <NUM>. A centerline of the lumen may be one millimeter removed from a centerline of the outer diameter, such that positioning element <NUM> holds a centerline of tether head assembly <NUM> one millimeter removed from the centerline of elongated shaft <NUM>. In this way, positioning element <NUM> may align an attachment mechanism of tether head assembly <NUM> with attachment member <NUM>, both being one millimeter away from the described centerline.

Positioning element <NUM> may be configured to allow fluid to flow through elongated shaft <NUM> for treatment of patient through retrieval catheter <NUM> when positioning element <NUM> is within the lumen of elongated shaft <NUM>. For example, positioning element <NUM> may comprise a coil, where each turn of the coil is spaced slightly apart from one another to allow fluid to flow between the turns of the coil. In another example, positioning element <NUM> may comprise a plurality of channels defining lumens along the length of positioning element <NUM> from proximal end <NUM> to distal end <NUM>. These channels may allow fluid to pass from proximal end <NUM> to distal end <NUM> and into the body of the patient. In another example, as described below, positioning element <NUM> may comprise a plurality of fins along the length of positioning element <NUM> extending radially from an outer diameter of elongate body <NUM> to an inner diameter of elongated shaft <NUM>, where fluid may flow along the length of positioning element <NUM> through the gaps in between the fins.

<FIG> is a conceptual drawing of the distal portion of the example tether assembly of <FIG> in conjunction with a side view of the IMD of <FIG>, where the tether head assembly and the IMD are not connected.

<FIG> illustrates IMD <NUM> detached from tether assembly <NUM>, as may be the case prior to removal of IMD <NUM> from the treatment site. In particular, in <FIG>, attachment member <NUM> of IMD <NUM> is not received within the attachment mechanism of tether head assembly <NUM> of tether assembly <NUM>.

<FIG> illustrates positioning element <NUM> attached to, or otherwise positioned proximal of, tether head assembly <NUM> of tether assembly <NUM> and at least partly covering an elongate body <NUM> (not pictured in <FIG>) of tether head assembly <NUM>, wherein elongate body <NUM> may include a shaft defining a lumen. Pull wire <NUM> (see, e.g., <FIG>) extends through the lumen defined by elongate body <NUM> and may be connected to inner retainer <NUM>. Various components of retrieval system <NUM> and tether assembly <NUM> may be connected by any of a variety of techniques, such as welding, crimping, threading, reflowing, bonding, adhesives, or friction fits. In addition, although positioning element <NUM> is depicted as connected to tether head assembly, in some examples positioning element <NUM> may be connected to elongate body <NUM>.

Attachment member <NUM> of IMD <NUM> may be included as part of a structure that provides a variety of features supporting a variety of functions related to delivery and retrieval of IMD <NUM>. In the illustrated example, attachment member <NUM> is formed within, and joined to housing <NUM> of IMD <NUM>, by a shroud structure <NUM>. In the illustrated example, attachment member <NUM> comprises a pin, bar, crossbar, or strut that is welded or otherwise fixedly attached to shroud structure <NUM>. Attachment member <NUM> provides an elongate holding surface that is spaced apart from housing proximal end <NUM> of housing <NUM> and that extends along a length substantially orthogonal to a longitudinal axis of IMD <NUM>.

Shroud structure <NUM> may define a cavity with an opening and attachment member <NUM> may span and be exposed at the opening. Attachment member <NUM> may be welded at either end to opposing sides of shroud structure <NUM>. A distal portion of outer retainer <NUM> of tether head assembly <NUM> may be configured to enter or otherwise interact with shroud structure <NUM> (e.g., the cavity thereof) when attachment member <NUM> is received within passageway <NUM> and receptacle <NUM>. The configuration of shroud structure <NUM> and distal portion of outer retainer <NUM> may selectively inhibit or allow relative motion of IMD <NUM> and tether assembly in a variety of directions. It should be understood that shroud structure <NUM> and attachment member <NUM> are provided for example only, and that a variety of other attachment members may be configured to be attached to tether assemblies.

<FIG> is a side view of an example tether assembly including a tether head assembly and a positioning element according to one embodiment, which can in some examples be generally similar to the tether head assembly and a positioning element shown in <FIG>, except as further described herein.

Positioning element <NUM> may comprise a coil that extends a length between distal end <NUM> and proximal end <NUM>, having an inner diameter and an outer diameter. The coil may surround elongate body <NUM> at a location proximal of and/or adjacent to tether head assembly <NUM>. The inner diameter and/or distal end of positioning element <NUM> may be connected to tether head assembly <NUM> and the outer diameter of positioning element <NUM> may be approximately equal to an outer diameter of at least a portion of tether head assembly <NUM>. The inner diameter of positioning element <NUM> may define a lumen along the length of positioning element <NUM>, through which a portion of elongate body <NUM> lies.

The outer diameter of positioning element <NUM> may be approximately equal to an inner diameter of elongated shaft <NUM>. As tether head assembly <NUM> and distal end <NUM> of positioning element <NUM> extend outwards from the distal end of elongated shaft <NUM> and into cup <NUM>, proximal end <NUM> of positioning element <NUM> may remain within a portion of the distal end of elongated shaft <NUM>. The body of the coil and the close fit of proximal end <NUM> within elongated shaft <NUM> may hold distal end <NUM> of positioning element <NUM> approximately concentric with elongated shaft <NUM> while distal end <NUM> extends into cup <NUM>. In turn, distal end <NUM> may hold tether head assembly <NUM> concentric with elongated shaft <NUM> while tether head assembly <NUM> extends into cup <NUM>. In this way, positioning element <NUM> may align tether head assembly <NUM> with attachment member <NUM> of IMD <NUM> within cup <NUM>, where cup <NUM> and IMD <NUM> are concentric with elongated shaft <NUM>.

In another example, attachment member <NUM> does not lie on a centerline of cup <NUM> or IMD <NUM>. Instead, attachment member <NUM> may lie a certain distance radially away from the centerline of cup <NUM>, IMD <NUM>. When elongated shaft <NUM> is concentric with cup <NUM> or IMD <NUM>, positioning element <NUM> may hold tether head assembly <NUM> off the centerline of elongated shaft <NUM> the same distance and in the same direction as attachment member <NUM> lies off the centerline of cup <NUM> or IMD <NUM>. In other examples, IMD <NUM> may be concentric with cup <NUM>, but elongated shaft <NUM> may not be concentric with cup <NUM>. In this case, positioning element <NUM> may hold tether head assembly <NUM> off the centerline of elongated shaft <NUM> in a distance and direction to compensate for the lack of concentricity.

In some examples, each turn of the coil of positioning element <NUM> may be spaced slightly apart from one another to allow fluid to flow between the turns of the coil. In this way, fluid may travel from proximal end <NUM> to distal end <NUM> for potential treatment of a patient. In other examples, positioning element <NUM> may comprise a plurality of channels defining lumens along the length of positioning element <NUM> from proximal end <NUM> to distal end <NUM>. These channels may pass through each turn of the coil, allowing fluid to flow through the plurality of channels. Where implemented, this property of allowing fluid flow along the length of positioning element <NUM> allows positioning element <NUM> to fit closely within elongated shaft <NUM> in the radial direction without causing a "piston effect" as positioning element <NUM> is advanced or retracted along elongated shaft <NUM>. Such a piston effect would entail a buildup of positive fluid pressure on the leading side of positioning element <NUM> and/or negative fluid pressure on the trailing side.

<FIG> are conceptual drawings illustrating example tether assemblies, including a tether head assembly and a positioning element, according to different embodiments.

As illustrated in <FIG>, in some examples positioning element <NUM> may comprise a series of fins <NUM> (one of which is labeled in <FIG>) extending along at least a portion of the length of positioning element <NUM> from proximal end <NUM> to distal end <NUM> and extending radially outward from a centerline that travels the length of positioning element <NUM>. Fins <NUM> may extend radially outward until they reach the inner walls of elongated shaft <NUM>.

In some examples, the edges of fins <NUM> may join near the center of positioning element <NUM> such that they define an inner diameter of positioning element <NUM> that may be connected to tether head assembly <NUM>. The inner diameter of positioning element <NUM> may be approximately equal to an outer diameter of at least a portion of tether head assembly <NUM>. The inner diameter of positioning element <NUM> may define a lumen along the length of positioning element <NUM>, through which elongate body <NUM> extends. The inner diameter of positioning element <NUM> may surround elongate body <NUM> at a location proximal of and/or adjacent to tether head assembly <NUM>.

In other examples, fins <NUM> are individually attached to elongate body <NUM> at a location proximal of and/or adjacent to tether head assembly <NUM>, and the edges of fins <NUM> do not join such that they define an inner diameter of positioning element <NUM>. In this case, fins <NUM> may be attached to tether head assembly or elongate body <NUM> along a length from proximal end <NUM> to distal end <NUM>.

Fins <NUM> of example positioning element <NUM> may extend radially outward from a centerline of positioning element <NUM> such that their edges create a profile defining an outer diameter. The outer diameter of positioning element <NUM> may be approximately equal to an inner diameter of elongated shaft <NUM>. As tether head assembly <NUM> and distal end <NUM> of positioning element <NUM> extend distally from the distal end of elongated shaft <NUM> and into cup <NUM>, proximal end <NUM> of positioning element <NUM> may remain within a portion of the distal end of elongated shaft <NUM>. The close fit of proximal end <NUM> of fins <NUM> within elongated shaft <NUM> may hold distal end <NUM> of positioning element <NUM> approximately concentric with elongated shaft <NUM> while distal end <NUM> extends into cup <NUM>. In turn, distal end <NUM> may hold tether head assembly <NUM> concentric with elongated shaft <NUM> while tether head assembly <NUM> extends into cup <NUM>. In this way, positioning element <NUM> may align tether head assembly <NUM> with attachment member <NUM> of IMD <NUM> within cup <NUM>, where cup <NUM> and IMD <NUM> are concentric with elongated shaft <NUM>.

In another example, attachment member <NUM> does not lie on a centerline of cup <NUM> or IMD <NUM>. Instead, attachment member <NUM> may lie a certain distance radially away from the centerline of cup <NUM>, IMD <NUM>. When elongated shaft <NUM> is concentric with cup <NUM> or IMD <NUM>, positioning element <NUM> may hold tether head assembly <NUM> off the centerline of elongated shaft <NUM> the same distance and in the same direction as attachment member <NUM> lies off the centerline of cup <NUM> or IMD <NUM>. For example, fins <NUM> on one side of positioning element <NUM> may be a different length than fins <NUM> on another side, or each fin of the plurality of fins <NUM> of positioning element <NUM> may be a different length such that a centerline of the inner diameter of positioning element <NUM> lies parallel to, but offset from, a centerline of elongated shaft <NUM>. Positioning element <NUM> may hold tether head assembly <NUM> along the offset centerline as well to align tether head assembly <NUM> with attachment member <NUM>. In other examples, IMD <NUM> may be concentric with cup <NUM>, but elongated shaft <NUM> may not be concentric with cup <NUM>. In this case, positioning element <NUM> may hold tether head assembly <NUM> off the centerline of elongated shaft <NUM> in a distance and direction to compensate for the lack of concentricity.

Each fin <NUM> of the plurality of fins <NUM> of positioning element <NUM> may be spaced apart such that the fins <NUM> define gaps between one another along the length of positioning element <NUM>. In this way, fluid may travel from proximal end <NUM> to distal end <NUM> for potential treatment of a patient. Additionally, where implemented, this property of allowing fluid flow along the length of positioning element <NUM> allows positioning element <NUM> to fit closely within elongated shaft <NUM> in the radial direction without causing a "piston effect" as positioning element <NUM> is advanced or retracted along elongated shaft <NUM>. Such a piston effect would entail a buildup of positive fluid pressure on the leading side of positioning element <NUM> and/or negative fluid pressure on the trailing side.

As illustrated in <FIG>, in some examples positioning element <NUM> only surrounds a portion of the circumference of elongate body <NUM> and/or sheath <NUM> such that an open channel <NUM> is defined along positioning element <NUM>, e.g., from distal end <NUM> to proximal end <NUM>, between surfaces <NUM>. Positioning element <NUM> may comprise an inner diameter approximately equal to an outer diameter of elongate body <NUM> and an outer diameter approximately equal to an inner diameter of elongated shaft <NUM>.

The material of positioning element <NUM> may be slightly elastic such that when a force is applied to surfaces <NUM>, open channel <NUM> grows, and when the force is released, positioning element <NUM> and open channel <NUM> return to their original shape and size. In this way, positioning element <NUM> may act as a clip that a physician may attach to elongate body <NUM> and/or sheath <NUM> before inserting tether head assembly into a patient's body.

Fluid may travel from proximal end <NUM> to distal end <NUM> through open channel <NUM> for potential treatment of a patient. Positioning element <NUM> may comprise a plurality of other channels defining lumens along the length of positioning element <NUM> from proximal end <NUM> to distal end <NUM> as well, allowing fluid flow. Additionally, where implemented, this property of allowing fluid flow along the length of positioning element <NUM> allows positioning element <NUM> to fit closely within elongated shaft <NUM> in the radial direction without causing a "piston effect" as positioning element <NUM> is advanced or retracted along elongated shaft <NUM>. Such a piston effect would entail a buildup of positive fluid pressure on the leading side of positioning element <NUM> and/or negative fluid pressure on the trailing side.

<FIG> is a flow diagram illustrating an example process for retrieving an IMD from a location within the heart using the example tether assemblies of <FIG>.

A medical device retrieval system <NUM>, including a distal end of a shaft of retrieval catheter <NUM>, is positioned in close proximity with IMD <NUM> (<NUM>). A clinician may advance retrieval catheter <NUM> through introducer <NUM> and into the vasculature to the implant site. The clinician may advance retrieval catheter <NUM> towards the implant site in tissue <NUM> until the distal end of a shaft of retrieval catheter <NUM> is sufficiently close to IMD <NUM>. In some examples, cup <NUM> is connected at the distal end of the shaft of retrieval catheter <NUM>, and the clinician may position distal opening <NUM> of cup <NUM> sufficiently close to IMD <NUM>. The distal end of a shaft of retrieval catheter <NUM>, or distal opening <NUM> may be sufficiently close to IMD <NUM> when a snare advanced through catheter <NUM> may reach and attach to IMD <NUM>. The clinician may advance the snare through catheter <NUM> to the implant site. The snare may be of sufficient length that a clinician may advance a distal end of the snare out of distal opening <NUM> of cup <NUM> and attach the distal end of the snare to one or more members of IMD <NUM> (e.g., attachment member <NUM>, shroud <NUM>). The clinician may apply tension to the snare and advance cup <NUM> over at least a portion of IMD <NUM>, through distal opening <NUM>, using the snare as a guide.

When the clinician is satisfied with the positioning of cup <NUM> with respect to tissue <NUM>, the clinician may detach the snare from IMD <NUM> and remove the snare from retrieval catheter <NUM>. The clinician may replace the snare with tether assembly <NUM>, including positioning element <NUM>, advancing tether head assembly <NUM> towards distal cup <NUM> using tether assembly <NUM>, e.g., by using tether assembly handle <NUM> to advance tether assembly <NUM> distally relative to retrieval catheter <NUM>.

Once tether head assembly <NUM> reaches the distal end of elongated shaft <NUM>, a clinician may advance tether head assembly <NUM>, including an attachment mechanism of tether head assembly <NUM>, distally out of a lumen defined by elongated shaft <NUM> (<NUM>). Positioning element <NUM> may be fixedly positioned over tether head assembly <NUM> and aligns an attachment mechanism of tether head assembly <NUM> to attachment member <NUM> while tether head assembly <NUM> is extended distally out of the lumen. In some examples, tether head assembly may extend distally out of the lumen and into cup <NUM>. In some examples, positioning element <NUM> may position tether head assembly <NUM> concentrically within cup <NUM> while tether head assembly <NUM> is extended distally out of the lumen and into cup <NUM>. In some examples, proximal end <NUM> of positioning element <NUM> may remain inside the lumen defined by elongated shaft <NUM> while a distal end of tether head assembly <NUM> is extended distally out of the lumen.

When the attachment mechanism of tether head assembly <NUM> and attachment member <NUM> are aligned, clinician attaches the attachment mechanism of tether head assembly <NUM> to attachment member <NUM> of IMD <NUM> (<NUM>). In some examples, the attachment mechanism of tether head assembly <NUM> may be configured to automatically latch on to attachment member <NUM>. In other examples, the clinician may need to operate attachment mechanism of tether head assembly <NUM> by manipulation of an actuator of tether handle assembly.

The clinician may disengage IMD <NUM> from the patient's tissue at the implant site (<NUM>). In some examples, tether head assembly <NUM>, positioning element <NUM>, and pull wire <NUM> may be rotatable around a centerline of elongated shaft <NUM>, and fixation member <NUM> may be helical. The clinician may rotate tether head assembly <NUM> to unscrew fixation member <NUM> and IMD <NUM> from the tissue at the implant site. Accordingly, in such examples the clinician can make a torque-transmitting connection of tether head assembly <NUM> to attachment member <NUM> and IMD <NUM>, and thereby use tether head assembly <NUM> as a driver to facilitate removal of IMD <NUM> via unscrewing. Once IMD <NUM> has been disengaged from the patient's tissue, it may be withdrawn from the patient proximally through introducer <NUM> along with retrieval catheter <NUM>. In some examples, after IMD <NUM> is disengaged from the patient's tissue, IMD <NUM> may be repositioned and implanted at a new implant site within the patient using retrieval catheter <NUM>, rather than fully withdrawn, after which retrieval catheter <NUM> may be withdrawn including tether assembly <NUM>.

<FIG> is a conceptual diagram of a map of a patient's heart in a standard <NUM> segment view of the left ventricle showing various electrode implantation locations for use with, e.g., the exemplary system and devices of <FIG>.

<FIG> is a two-dimensional (2D) ventricular map <NUM> of a patient's heart (e.g., a top-down view) showing the left ventricle <NUM> in a standard <NUM> segment view and the right ventricle <NUM>. The map <NUM> includes a plurality of areas <NUM> corresponding to different regions of a human heart. As illustrated, the areas <NUM> are numerically labeled <NUM>-<NUM> (which, e.g., correspond to a standard <NUM> segment model of a human heart, correspond to <NUM> segments of the left ventricle of a human heart, etc.). Areas <NUM> of the map <NUM> may include basal anterior area <NUM>, basal anteroseptal area <NUM>, basal inferoseptal area <NUM>, basal inferior area <NUM>, basal inferolateral area <NUM>, basal anterolateral area <NUM>, mid-anterior area <NUM>, mid-anteroseptal area <NUM>, mid-inferoseptal area <NUM>, mid-inferior area <NUM>, mid-inferolateral area <NUM>, mid-anterolateral area <NUM>, apical anterior area <NUM>, apical septal area <NUM>, apical inferior area <NUM>, apical lateral area <NUM>, and apex area <NUM>. The inferoseptal and anteroseptal areas of the right ventricle <NUM> are also illustrated, as well as the right bunch branch (RBB) and left bundle branch (LBB).

In some embodiments, any tissue-piercing electrode of the present disclosure may be implanted in the basal and/or septal region of the left ventricular myocardium of the patient's heart. In particular, the tissue-piercing electrode may be implanted from the triangle of Koch region of the right atrium through the right atrial endocardium and central fibrous body.

Once implanted, the tissue-piercing electrode may be positioned in the target implant region, such as the basal and/or septal region of the left ventricular myocardium. With reference to map <NUM>, the basal region includes one or more of the basal anterior area <NUM>, basal anteroseptal area <NUM>, basal inferoseptal area <NUM>, basal inferior area <NUM>, mid-anterior area <NUM>, mid-anteroseptal area <NUM>, mid-inferoseptal area <NUM>, and mid-inferior area <NUM>. With reference to map <NUM>, the septal region includes one or more of the basal anteroseptal area <NUM>, basal anteroseptal area <NUM>, mid-anteroseptal area <NUM>, mid-inferoseptal area <NUM>, and apical septal area <NUM>.

In some embodiments, the tissue-piercing electrode may be positioned in the basal septal region of the left ventricular myocardium when implanted. The basal septal region may include one or more of the basal anteroseptal area <NUM>, basal inferoseptal area <NUM>, mid-anteroseptal area <NUM>, and mid-inferoseptal area <NUM>.

In some embodiments, the tissue-piercing electrode may be positioned in the high inferior/posterior basal septal region of the left ventricular myocardium when implanted. The high inferior/posterior basal septal region of the left ventricular myocardium may include a portion of at least one of the basal inferoseptal area <NUM> and mid-inferoseptal area <NUM>. For example, the high inferior/posterior basal septal region may include region <NUM> illustrated generally as a dashed-line boundary. As shown, the dashed line boundary represents an approximation of about where the high inferior/posterior basal septal region and may take somewhat different shape or size depending on the particular application. Without being bound by any particular theory, intraventricular synchronous pacing and/or activation may result from stimulating the high septal ventricular myocardium due to functional electrical coupling between the subendocardial Purkinje fibers and the ventricular myocardium.

Claim 1:
A system comprising:
a catheter (<NUM>) comprising an elongated shaft (<NUM>) defining a lumen; and
a tether assembly (<NUM>) comprising:
an elongate body (<NUM>);
a tether head assembly (<NUM>) attached to a distal end of the elongate body, the tether head assembly comprising an attachment mechanism configured to releasably attach to an attachment member (<NUM>) of a medical device (<NUM>); and
a positioning element (<NUM>) fixedly positioned over the elongate body and configured to align the attachment mechanism with the attachment member when the tether head assembly is extended distally out of the lumen, wherein the positioning element comprises:
a distal end (<NUM>);
a proximal end (<NUM>);
a length between the distal end and proximal end that is less than a length of the elongate body; and
wherein the tether head assembly, elongate body, and positioning element are movable within the lumen of the elongated shaft.