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 delivery system including a delivery catheter may be used to deliver an intracardiac device transvenously to an implant site within a heart of a patient and release the device after the device has been fixed at the implant site. The medical device delivery system then may be withdrawn from the patient. Document <CIT> discloses a tethering assembly for deploying a medical device.

In general, this disclosure is directed to examples of tether assemblies of medical device delivery systems and to techniques using such tether assemblies. Example tether assemblies may include a distal tether head assembly configured to releasably retain an attachment member of a medical device, e.g., an intracardiac device. Additionally, or alternatively, a tether assembly of a medical device delivery system may include a tether handle assembly configured to retain a proximal end of a pull wire of the tether assembly. The tether handle assembly includes one or more components (e.g., an actuator) configured to transmit force to a tether head assembly via the pull wire. The techniques may include applying a force to the actuator of the tether handle assembly move the pull wire, thereby enabling removal of the attachment member from the tether head assembly at a treatment site.

The tether head assembly may include an inner retainer and an outer retainer. The outer retainer may define an aperture including a receptacle configured to receive an attachment member of a medical device and a passageway extending from a distal end of the outer retainer proximally to the receptacle. The aperture further may include a groove extending from the distal end of the outer retainer proximally at least to the receptacle.

The inner retainer may be movable between a first position and a second position. When the inner retainer is in the first position, the distal portion of the inner retainer may be partially received in the groove and extend into the passageway, thereby narrowing the passageway. The passageway thus may be dimensioned to prevent passage of the attachment member therethrough when the inner retainer is in the first position, such as to prevent passage of the attachment member from the receptacle when the attachment member is loaded onto the tether assembly during a medical procedure to deliver the medical device. When the inner retainer is in the second position, the inner retainer does not narrow the passageway and the passageway thus may be dimensioned to receive the attachment member of the medical device, such as when the medical device is being loaded onto the tether assembly or released from the tether assembly.

The inner retainer may be biased to the first position. When the proximal movement of the pull wire is discontinued and/or when the attachment member has been passed through the passageway and is received within the receptacle defined by the outer member, an elastically-compressible member of the tether head assembly may expand and apply distally-directed force to the inner retainer, thereby moving the inner retainer from the second position to the first position.

In other examples, a tether head assembly configured to retain an attachment member of a medical device may include a retainer or other such component that is not biased to return to such a first position. The act of loading a medical device onto such other tether assemblies prior to delivery to a heart of a patient may require two people (e.g., clinicians). A first person may be required to hold the medical device in position while a second person opens the tether head assembly, such as by proximally moving a pull wire of the tether assembly to move the inner retainer from a first position in which the tether assembly is "closed" to a second position in which the tether assembly is "open. " The first person then may load the attachment member of the medical device onto the tether head assembly (e.g., by placing the attachment member in a receptacle defined by the tether head assembly) and the second person may distally move the pull wire to return the tether head assembly to the first position and retain the attachment member within the receptacle. Loading a medical device onto a tether assembly using two people may add time and complexity to a medical procedure to deliver the medical device and/or may increase a possibility of contamination of the medical device or other objects within the surgical field.

Example tether head assemblies described herein may enable loading of a medical device onto a tether assembly by one person instead of two. For example, bias of the inner retainer to the first position may enable a clinician to hold the tether head assembly in one hand and simply press the attachment member into a passageway defined by an outer retainer, thereby moving the inner retainer to the second position as the attachment member moves through the passageway to the receptacle as an elastically-compressible member of the tether head assembly is compressed. The biasing of an inner retainer to a first position provided by the elastically-compressible member may enable the clinician to simply release his or her hold on the medical device once the attachment member is received within the receptacle allowing the inner retainer to return to the first position.

In this manner, the tether assemblies described herein may reduce the time and complexity associated with a procedure to deliver the medical device. In some examples, the tether assemblies described herein may reduce a possibility of contamination of the medical device or other objects within the surgical field by reducing the number of people that touch the medical device and the tether assembly. 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 some examples, a tether handle assembly as described herein may be used in conjunction with a tether head assembly as described herein and a share pull wire. As an example, a tether assembly may include a tether head assembly, a pull wire, and a tether handle assembly attached to a proximal end of the pull wire. The tether handle assembly may include an actuator configured to cause a proximal movement of the pull wire that enables removal of the attachment member from the tether head assembly. Application of a force to the actuator may cause proximal movement of the pull wire, which may enable release of the medical device from the tether head assembly at a treatment site within a patient (e.g., within a heart of the patient). The force applied to the actuator may be a distally-directed force, e.g., a button push. In such examples, one or more components of the tether handle assembly may be configured to translate the distally-directed force applied to the actuator to a proximally-directed force applied to the pull wire.

Examples in which a tether handle assembly of a tether assembly of a medical device delivery system is configured to enable release of the medical device from the tether assembly by translating a distally-directed force into a proximally-directed force may provide one or more advantages. In some examples, a clinician may find applying a distally-directed force (i.e., a pushing force) to a button or slidable member to release the medical device to be intuitive and/or otherwise easier to use than some other tether handle assembly configurations. In some examples, a clinician may be less likely to accidentally release the medical device when using a tether handle assembly configured to enable release of the medical device from the tether assembly via distally-directed force relative to other actuator configurations.

Any such tether handle assemblies may include one or more components configured to reduce a possibility of accidental release of the medical device from the tether assembly, such as a lock member or a cover. Additionally, or alternatively, any of the handle assemblies described herein may enable sensing of electrical signals via an electrical path including the medical device and one or more components of a tether assembly including the tether handle assembly, which may help enable a clinician to determine positioning of the delivery and medical device relative to target tissue, attachment of the medical device to target tissue, and how much force to apply to an actuator of a tether handle assembly to enable release the medical device from the tether assembly.

In some other examples, a tether assembly of a medical device delivery system may not be re-usable, such as in other examples in which a tether assembly includes a string or other such component that is looped through the medical device and then cut after the medical device is fixed at a treatment site. In such other examples, a new tether assembly and/or medical device delivery system thus may be packaged with each medical device. Packaging a medical device delivery system and/or tether assembly with a medical device may be associated with shelf-life considerations, such as in examples in which the medical device includes a drug-eluting component that may have an expiration date.

The example tether assemblies described herein may be sterilizable and re-usable, at least in part because the tether assembly can be released from the medical device without being cut. In some examples, the tether assembly may be packaged separately from the medical device, such as examples in which the medical device may include a drug eluting component that has a finite shelf life. In such instances, packaging the tether assembly separately from medical device may mitigate shelf life considerations with respect to the tether assembly.

Thus, the example tether assemblies described herein may enable one-person loading of a medical device onto a tether assembly, may be more intuitive for a clinician to operate than some other example tether assemblies, may reduce a possibility of accidental deployment of a medical device, may enable a clinician to determine placement of the medical device at a treatment site within a patient (e.g., within a heart of the patient), and/or may enable a clinician to monitor electrical signals from the medical device and/or distal portion of the delivery system during an implantation procedure.

In one example, a tether assembly of a medical device delivery system comprises a pull wire defining a proximal end and a distal end, and a tether head assembly. The tether head assembly comprises an inner retainer comprising a proximal portion and a distal portion, wherein the inner retainer is coupled to and extends distally from the distal end of the pull wire, and an outer retainer comprising a proximal portion defining a channel configured to receive the inner retainer and a distal portion defining an aperture. The aperture comprises a receptacle configured to receive an attachment member of a medical device, a passageway extending from a distal end defined by the outer retainer proximally to the receptacle, wherein the passageway is narrower than the receptacle, and a groove extending from the distal end of the outer retainer proximally at least to the receptacle, wherein the groove has a depth that is less than a thickness of the distal portion of the inner retainer. The inner retainer is movable between a first position wherein the distal portion of the inner retainer is partially received in the groove and extends into the passageway, thereby narrowing the passageway, and a second position wherein the distal portion of the inner retainer is positioned proximal to the passageway.

In another example, a tether assembly of a medical device delivery system comprises a tether handle assembly comprising a housing defining a curved channel that defines a first end and a second end, a force transmitter received within the curved channel, a slidable member received within the housing such that a portion of the slidable member is received within the channel at the first end of the channel, and a button defining a proximal surface and comprising a distal portion received within the channel at the second end of the channel, wherein the button surrounds at least a proximal portion of the slidable member. The tether assembly further comprises a pull wire defining a proximal end and a distal end, wherein the proximal end of the pull wire is received within the housing and retained by the slidable member. The button is configured to move from a first position to a second position in response to application of a distally-directed force to the button, thereby moving the force transmitter toward the first end of the curved channel such that the force transmitter applies a proximally-directed force to the portion of the slidable member received within the channel that causes the slidable member and the pull wire to move proximally.

In another example, a method for using tether assembly of a medical device delivery system comprises positioning a tether head assembly of the tether assembly at a treatment site of a patient with an attachment member of a medical device received within a receptacle of the tether head assembly, the tether head assembly configured to releasably retain the attachment member of the medical device. The tether head assembly comprises an inner retainer comprising a proximal portion and a distal portion, wherein the inner retainer is coupled to and extends distally from the distal end of a pull wire of the medical device delivery system, an outer retainer comprising a proximal portion defining a channel configured to receive the inner retainer and a distal portion defining an aperture. The aperture comprises the receptacle configured to receive the tether member of the medical device, a passageway extending from a distal end of the outer retainer proximally to the receptacle, wherein the passageway is narrower than the receptacle, and a groove extending from the distal end of the outer retainer proximally at least to the receptacle, wherein the groove has a depth that is less than a thickness of the distal portion of the inner retainer. Positioning the tether head assembly comprises positioning the tether head assembly with the inner retainer in a first position wherein the distal portion of the inner retainer is partially received in the groove and extends into the passageway, thereby narrowing the passageway, wherein the passageway is dimensioned to prevent passage of the attachment member when the inner retainer is in the first position. The method further comprises applying a force to an actuator of the tether assembly to cause a proximal movement of the pull wire, the proximal movement of the pull wire moving the inner retainer from the first position to a second position wherein the distal portion of the inner retainer is positioned proximal to the passageway, wherein the passageway is dimensioned to receive the attachment member of the medical device when the inner retainer is in the second position, allowing the attachment member of the medical device to pass from the receptacle through the passageway. The method further comprises proximally moving the tether assembly with the inner retainer in the second position to remove the attachment member of the medical device from the tether head assembly, thereby delivering the medical device to the treatment site.

In another example, a tether assembly of a medical device delivery system comprises a tether handle assembly comprising a housing, a first slidable member defining a first aperture and received within the housing, a second slidable member received within the first aperture and defining a second aperture, and at least one gear received within the aperture defined by the first slidable member and configured to mechanically engage the first slidable member and the second slidable member. The tether assembly further comprises a pull wire defining a proximal end and a distal end, wherein the proximal end of the pull wire is received within the housing and is retained by the second slidable member. The first slidable member is configured to move distally in response to application of a distally-directed force to the first slidable member and, when the first slidable member moves distally, and the at least one gear moves the second slidable member and the pull wire proximally.

In another example, a tether assembly of a medical device delivery system comprises a tether handle assembly comprising a housing, a slidable member received within the housing, a plunger coupled to and extending distally from the slidable member. The tether assembly further comprises a pull wire defining a proximal end and a distal end, wherein the proximal end of the pull wire is received within the housing and is retained by the slidable member. The plunger is configured to move from a first position to a second position in response to application of a proximally-directed force to the plunger that causes the slidable member and the pull wire to move proximally.

In another example, a method for using a tether assembly of a medical device delivery system comprises positioning a tether head assembly of the tether assembly at a treatment site of a patient with an attachment member of a medical device received within a receptacle of the tether head assembly, the tether head assembly configured to releasably retain the attachment member of the medical device. The method further comprises applying a force in a distal direction to an actuator of a tether handle assembly of the tether assembly to cause a proximal movement of the pull wire, the proximal movement of the pull wire opening the tether head assembly, and proximally moving the tether assembly with the tether head assembly open to remove the attachment member of the medical device from the tether head assembly, thereby delivering the medical device to the treatment site.

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 delivery systems. Such medical device delivery systems may include a tether assembly comprising a tether head assembly, and tether handle assembly, and a pull wire. The tether head assembly is attached to the pull wire and configured to releasably retain an attachment member of a medical device (e.g., an intracardiac device). In some examples, a tether handle assembly is configured to retain the pull wire attached to the tether head assembly. The tether handle assembly may include an actuator configured to transmit force to the tether head assembly via the pull wire and enable removal of the attachment member of a medical device from the tether head assembly at a treatment site within a patient. Although the example tether assemblies are generally described herein as being configured for delivering an implantable medical device (IMD), it should be understood that any of the example tether assemblies described herein alternatively may be configured for delivering other types of medical devices.

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

System <NUM> includes an introducer <NUM>, a delivery 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 insert a medical instrument, a device, or other therapy.

Delivery catheter <NUM> is configured to be inserted through the lumen of introducer <NUM> to deliver an IMD within the vasculature. Delivery catheter <NUM> includes an elongated shaft <NUM>, a handle <NUM>, and a device cup <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 of the distal end of shaft <NUM> and release of the IMD from device cup <NUM>, as examples.

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 implanted within a vasculature of a patient. For example, a physician may insert the distal end of delivery 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 release the IMD from a distal opening <NUM> of device cup <NUM> and withdraw delivery catheter <NUM> proximally through introducer <NUM>.

Tether assembly <NUM> extends through a lumen defined delivery catheter, e.g., including handle <NUM> and shaft <NUM>. Tether assembly <NUM> 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>. 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>.

Tether assembly <NUM> may be of sufficient length that a clinician may manipulate tether handle assembly <NUM> to advance tether head assembly <NUM> out of distal opening <NUM> of cup <NUM>. In some examples, with tether head assembly <NUM> outside of cup <NUM>, a clinician may attach an IMD to tether head assembly <NUM> as described herein. The clinician may then load the IMD into cup <NUM> via distal opening <NUM>, and advance delivery catheter <NUM>, with tether assembly <NUM> and the IMD therein, through introducer <NUM> and into the vasculature.

<FIG> is a conceptual drawing illustrating, in conjunction with tissue <NUM> of heart <NUM>, a distal portion of medical device delivery system <NUM> carrying 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 delivery 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.

<FIG> illustrates the distal end cup <NUM> of delivery 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> pressed sufficiently against/into tissue <NUM> such that fixation members <NUM> of IMD <NUM> will deploy into the tissue, the clinician may advance IMD <NUM> towards distal opening using tether assembly <NUM>, e.g., by using tether assembly handle <NUM> to advance tether assembly <NUM> distally relative to delivery catheter <NUM>. Fixation members <NUM> may be configured to embed into tissue <NUM>, and in some cases pull IMD <NUM> through distal opening <NUM> of cup, when advanced through the distal opening. While IMD <NUM> is shown having fixation members <NUM> that includes a plurality of tine structures, it should be understood that IMD <NUM> may include any other suitable fixation structure or structures, such as a screw-shaped fixation structure (helix) that may be rotated into tissue at an implant site.

IMD <NUM> may, for a time, remain attached to tether assembly <NUM> by attachment member <NUM> and tether head assembly <NUM> while fixed to tissue <NUM> by fixation members <NUM>. Thus, the clinician may be able to test the fixation of IMD <NUM> at the implant site and/or remove IMD <NUM> from the implant site and back into cup <NUM> for repositioning at a more suitable site, if necessary. Once satisfied with the implantation of IMD <NUM>, the clinician can separate tether head assembly <NUM> from attachment mechanism <NUM> and move tether assembly <NUM> proximally, as described in greater detail below, and then withdraw delivery catheter <NUM> and tether assembly <NUM> from the patient through introducer <NUM>.

For example, tether assembly <NUM> may include a pull wire (not shown) as discussed in further detail with respect to <FIG>. Such a pull wire 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>, examples of which are discussed below with respect to <FIG>. The clinician may apply force to an actuator of tether handle assembly to cause tether head assembly <NUM> to move from a closed position, in which attachment member <NUM> is retained within tether head assembly <NUM>, to an open position in which attachment member <NUM> may be released from tether head assembly <NUM>. With tether head assembly <NUM> in the open position, the clinician may proximally move tether assembly <NUM> to remove attachment member <NUM> from tether head assembly <NUM>, leaving IMD <NUM> fixed at the treatment site.

A 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 tether member <NUM> is received within a receptacle defined by tether head assembly <NUM>, as further discussed below with respect to <FIG>. 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 delivery systems. Thus, tether assembly <NUM> may reduce the time and complexity associated with a procedure to deliver 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 deliver 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>, delivery 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 delivery system <NUM> may not necessarily be associated with a finite shelf life when packaged separately from IMD <NUM>.

During delivery of IMD <NUM> to the treatment site via delivery system <NUM>, a clinician may advance cup <NUM> into contact with tissue <NUM> of heart <NUM> prior to engaging fixation members <NUM> with tissue <NUM> of heart <NUM>. The clinician then may determine whether cup <NUM> and IMD <NUM> are properly positioned at the implant site prior to engaging fixation members <NUM> with the tissue <NUM> of heart <NUM>. In some examples, the clinician may determine whether cup <NUM> and IMD <NUM> is properly positioned relative to heart <NUM> based on an impedance or other electrical signal sensed via an electrical path including IMD <NUM> (e.g., housing <NUM> or an electrode <NUM>), attachment member <NUM>, and one or more components of tether assembly <NUM> (e.g., one or more components of tether head assembly <NUM>). In addition to the IMD, another electrode of the electrical path may be a reference electrode attached to the patient, or inside the patient but located outside of cup <NUM>. In some examples, relatively higher impedance may be indicative of cup <NUM> being positioned flush against, and with adequate depth in, tissue <NUM> of heart <NUM>, which may be desirable for proper fixation. After deployment of fixation members <NUM> and IMD <NUM> from cup <NUM>, with IMD <NUM> fixed to tissue <NUM>, an impedance or electrical signal may also indicate the quality of the fixation of IMD <NUM> to tissue, e.g., based on variations of the impedance during a "tug test" in which a clinician pulls on tether assembly <NUM> while attached to IMD <NUM> and while IMD <NUM> is fixed to tissue <NUM>. Some examples may employ any of the techniques for testing the spatial relationship of a cup and/or IMD to tissue, and for testing fixation of an IMD to tissue, described in <CIT>, and titled "Impedance-Based Verification for Delivery of Implantable Medical Devices".

<FIG> illustrate examples of distal portions of tether assemblies including example tether head assemblies. It should be noted that although <FIG> may be described with respect to IMD <NUM>, delivery systems may be used to deliver other suitably configured medical devices.

<FIG> is a plan view of a distal portion of a tether assembly <NUM> with the components of tether assembly <NUM> in an assembled configuration, where a distal portion of a tether head assembly <NUM> is outlined. <FIG> is an exploded plan view of the distal portion tether assembly <NUM>, where a distal portion of an inner retainer <NUM> of tether head assembly <NUM> is outlined. <FIG> is a plan view of the distal portion of the inner retainer <NUM> outlined in <FIG> is a plan view of the distal portion of the tether head assembly <NUM> outlined in <FIG>.

As illustrated in <FIG>, elongate body <NUM> may include a shaft defining a lumen (not shown) in which 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>, 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 of from a distal end (not shown) of pull wire <NUM>. A distal portion <NUM> of outer retainer <NUM> defines an aperture <NUM> that, as illustrated in <FIG> includes a receptacle <NUM> dimensioned to receive attachment member <NUM> of IMD <NUM> and a passageway <NUM>. Passageway <NUM> may extend from a distal end <NUM> defined by outer retainer <NUM> proximally to receptacle <NUM> and may be narrower than receptacle <NUM>.

A proximal portion <NUM> of outer retainer <NUM> may define a channel (not shown) configured to receive inner retainer <NUM>. Inner retainer <NUM> may be received within outer retainer <NUM> in a first position in which a distal portion <NUM> of inner retainer <NUM> extends into passageway <NUM>, as shown in <FIG>. When inner retainer <NUM> is in the 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>).

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., 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 tether member <NUM>. Inner retainer <NUM> and outer retainer <NUM> may be received within sheath <NUM>, and more particularly a cavity <NUM> defined by sheath <NUM>, which may help retain inner retainer <NUM> within outer retainer <NUM> and couple outer retainer <NUM> to elongate body <NUM>.

In some examples, the configuration of inner retainer <NUM> and outer retainer <NUM> may substantially isolate the function of retaining attachment member <NUM> of IMD <NUM> to tether head assembly <NUM>, rather than pull wire <NUM> or another element that extends to a handle assembly of tether assembly <NUM>. For example, as tether assembly <NUM> is navigated through curved portions of patient vasculature, the path lengths of pull wire <NUM> and/or shaft <NUM> may change. In some other example medical device delivery systems in which the tether assembly relies on a pull wire to retain an attachment member within a tether head assembly, such changes in path lengths of a pull wire and/or shaft may cause a loss of contact between the pull wire and the attachment member, thereby adversely affecting retention of the attachment member during delivery.

In the example of tether assembly <NUM> and other tether assemblies described herein, changes in path length of pull wire <NUM> and/or shaft <NUM> of tether assembly <NUM> may not cause substantial proximal or distal movement of inner retainer <NUM>. For example, sheath <NUM> and/or an elastically-compressible member <NUM> may help reduce or prevent proximal movement of inner retainer <NUM> as path lengths of pull wire <NUM> and/or shaft <NUM> change during navigation of curved vasculature. In this manner, the substantial isolation of the IMD retention function within tether head assembly <NUM> may help maintain retention of attachment member <NUM> as tether assembly <NUM> is navigated through curved vasculature.

In <FIG> a distal portion of inner retainer <NUM> is outlined, and that portion of inner retainer <NUM> is illustrated in greater detail in <FIG>. As shown in <FIG>, inner retainer <NUM> may include a proximal portion <NUM> and a distal portion <NUM>. Outer retainer <NUM> may include a proximal portion <NUM> and a distal portion <NUM>. Proximal portion <NUM> of outer retainer <NUM> may define a channel (not shown) dimensioned to receive proximal portion <NUM> of inner retainer <NUM>. Distal portion <NUM> of outer retainer <NUM> may define aperture <NUM>. In some examples, aperture <NUM> may further include a groove <NUM> extending from distal end <NUM> of outer retainer <NUM> proximally at least to receptacle <NUM>. Groove <NUM> may be partially defined by distal portion <NUM> of outer retainer <NUM> and may have a depth that is less than a thickness of distal portion <NUM> of inner retainer <NUM>. A value by which the thickness of distal portion <NUM> of inner retainer <NUM> exceeds the depth of groove <NUM> may correspond to a distance that inner retainer <NUM> extends, e.g., transverse to a longitudinal axis defined by inner retainer <NUM>, into passageway <NUM>.

<FIG> further illustrates elastically-compressible member <NUM>, which is receivable within cavity <NUM> defined by sheath <NUM> proximal of, e.g., in an abutting relationship with, inner retainer <NUM>. Elastically-compressible member <NUM> may be formed of a suitably elastically-compressible material, such as a polymer. Elastically-compressible member <NUM> may define a lumen <NUM> through which a distal portion of pull wire <NUM> may extend and be attached to more distally located inner retainer <NUM>. In some examples, elastically-compressible member <NUM> may be configured to bias inner retainer <NUM> to the first position. For example, elastically-compressible member <NUM> may define a longitudinal axis, which may correspond to a longitudinal axis of tether assembly <NUM>. Axial expansion of elastically-compressible member <NUM> relative to the longitudinal axis causes elastically-compressible member <NUM> to apply a distally-directed force to inner retainer <NUM>, thereby causing inner retainer <NUM> to move from the second position to the first position.

In this manner, elastically-compressible member <NUM> may function as a spring that biases inner retainer <NUM> to the first position. Biasing of inner retainer <NUM> to the first position may provide one or more advantages, such as enabling a clinician to load IMD <NUM> onto tether head assembly <NUM> without necessarily requiring the assistance of another clinician. Elastically-compressible member <NUM> may be received within sheath <NUM> when tether assembly <NUM> is in an assembled configuration, e.g., shown in <FIG>. In this manner, sheath <NUM> may provide a backstop against which elastically-compressible member <NUM> may be compressed during movement of inner retainer <NUM> from the first position to the second position.

The form of elastically-compressible member <NUM> illustrated in <FIG> is an example. In other examples, other forms of elastically-compressible member may be used to provide the functionality described with respect to elastically-compressible member <NUM> herein. For example, an elastically-compressible member may take the form of a coil or spring. Additionally, elastically-compressible members may be formed from a variety of materials, such as polymers or metals.

<FIG> is a plan view of distal portion <NUM> of inner retainer <NUM> outlined in <FIG>. As illustrated in <FIG>, distal portion <NUM> of inner retainer <NUM> may define a first portion <NUM>, a second portion <NUM>, and a third portion <NUM>. First portion <NUM> may include the distal end of inner retainer <NUM> and may have a first thickness. Second portion <NUM> may be proximal to first portion <NUM> and may have a second thickness that is greater than the first thickness of first portion <NUM>. Third portion <NUM> may extend between first portion <NUM> and second portion <NUM> and may taper in thickness from the first thickness of first portion <NUM> to the second thickness of second portion <NUM>. In this manner, the tapered thickness of third portion <NUM> may define a "ramp" surface from proximal portion <NUM> toward second portion <NUM> and receptacle <NUM>.

When attachment member <NUM> of IMD <NUM> is received in receptacle <NUM> (e.g., when inner retainer <NUM> is in the first position), the ramp surface defined by third portion <NUM> may help ensure substantially constant physical contact between attachment member <NUM> and at least third portion <NUM> of inner retainer <NUM>. The physical contact between attachment member <NUM> and inner retainer <NUM> enabled by third portion <NUM> is illustrated in <FIG> and further discussed with respect thereto.

In some examples, inner retainer <NUM> and attachment member <NUM> may be electrically conductive. In such examples, ensuring substantially constant physical contact between attachment member <NUM> and inner retainer <NUM> during a method of delivering IMD <NUM> may enable use as an electrical connection and/or may help reduce electrical noise that otherwise may be caused by intermittent contact between attachment member <NUM> and inner retainer <NUM>. A reduction in such electrical noise may help enable determination of whether IMD <NUM> is properly positioned and/or affixed relative to tissue of heart <NUM> during electrical testing of IMD <NUM> prior to release of IMD <NUM> from tether head assembly <NUM> at the implant site.

<FIG> illustrates a manner in which distal portion <NUM> of inner retainer <NUM> may be received within groove <NUM> defined by distal portion <NUM> of outer retainer <NUM> when inner retainer <NUM> is in the first position. In some examples, groove <NUM> may extend proximally from distal end <NUM> of outer retainer <NUM> toward receptacle <NUM>. In some examples, groove <NUM> may extend proximally past receptacle <NUM> toward proximal portion <NUM> of outer retainer <NUM>. In any such examples, groove <NUM> may help provide support to distal portion <NUM> of inner retainer <NUM>, such as by reducing a possibility of distal portion <NUM> being bent sideways during loading of attachment member <NUM> of IMD <NUM> into receptable <NUM>, or other use of tether assembly <NUM>. In this manner, groove <NUM> may help maintain the mechanical integrity and functionality of tether assembly <NUM> during one or more uses, thereby contributing to the durability of tether assembly <NUM>.

<FIG> is a side view of the distal portion of tether assembly <NUM>, including tether head assembly <NUM>, in conjunction with a side view of IMD <NUM>, where tether head assembly <NUM> and IMD <NUM> are not connected. <FIG> is a cross-sectional view of the portion of tether head assembly <NUM> and of the proximal portion of IMD <NUM> highlighted in <FIG>, where the cross-section is taken along line A-A of <FIG> in a plane parallel to a longitudinal axis of tether head assembly <NUM> and a longitudinal axis of the IMD <NUM>. <FIG> is a cross-sectional view of the highlighted portion of <FIG> including the distal portion of tether head assembly <NUM> and the proximal portion of IMD <NUM>, but with inner retainer <NUM> in the second position and attachment member <NUM> within receptacle <NUM> defined by the outer retainer <NUM>. <FIG> is a cross-sectional view of the highlighted portion of <FIG> including the distal portion of tether head assembly <NUM> and the proximal portion of IMD <NUM>, but with attachment member <NUM> held within receptacle <NUM> defined by outer retainer <NUM> by inner retainer <NUM> being in the first position.

<FIG> and <FIG> illustrate IMD <NUM> detached from tether assembly <NUM>, as may be the case prior to loading IMD <NUM> onto tether assembly <NUM> or after IMD <NUM> has been implanted at a desired tissue site. In particular, in <FIG> and <FIG>, attachment member <NUM> of IMD <NUM> is not received within tether head assembly <NUM> of tether assembly <NUM>.

<FIG> illustrates sheath <NUM> of tether head assembly <NUM> attached to the distal end of elongate member <NUM> of tether assembly <NUM>. Pull wire <NUM> extends through a lumen defined by elongate member <NUM> and into cavity <NUM> (<FIG>) defined by sheath <NUM>. Elastically-compressible member <NUM>, proximal portion <NUM> of inner retainer <NUM>, and proximal portion <NUM> of outer retainer <NUM> are disposed within cavity <NUM>, with a distal portion <NUM> of elastically-compressible member <NUM> and proximal portion <NUM> of inner retainer <NUM> received within a channel <NUM> (<FIG>) defined by proximal portion <NUM> of outer retainer <NUM>. Pull wire <NUM> extends through lumen <NUM> defined by elastically-compressible member <NUM>, and is connected to inner retainer <NUM>, e.g., fixedly received within proximal portion <NUM> of inner retainer <NUM>. Various components of delivery 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.

Distal portion <NUM> of inner retainer <NUM> extends into distal portion <NUM> of outer retainer <NUM> to contribute to the definition of receptacle <NUM>. In the illustrated first position of inner retainer <NUM>, distal portion <NUM> of inner retainer <NUM> also extends into passageway <NUM> to reduce the size of the passageway such that a thickness or depth of the passageway is smaller than a thickness of attachment member <NUM> of IMD <NUM>. In the illustrated first position of inner retainer <NUM>, distal portion <NUM> of inner retainer <NUM> may be disposed within groove <NUM> defined by distal portion <NUM> of outer retainer <NUM>, as described herein. In the illustrated first position of inner retainer <NUM>, elastically-compressible member <NUM> may be in a relaxed, or lower kinetic energy state.

As illustrated in <FIG>, 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 (also referred to as a 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>. Distal portion <NUM> of outer retainer <NUM> may be configured to enter or otherwise interact with shroud structure <NUM> when attachment member <NUM> is received within passageway <NUM> and receptacle <NUM>. The configuration of shroud structure <NUM> and distal portion <NUM> 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 as described herein.

<FIG> illustrates inner retainer <NUM> in the second position and attachment member <NUM> within receptacle <NUM> defined by the outer retainer <NUM>. Inner retainer <NUM> may be moved to the second position by a proximally directed force. The proximally directed force may be provided by a pulling force from pull wire <NUM> or a pushing force on distal end <NUM> of inner retainer <NUM> as attachment member <NUM> is pushed through passageway <NUM> and into receptacle <NUM>. As illustrated in <FIG>, movement of inner retainer <NUM> to the second position has compressed elastically-compressible member <NUM>, e.g., such that distal portion <NUM> is no longer located within channel <NUM> defined by proximal portion <NUM> of external retainer <NUM>.

When in this compressed state, elastically-compressible member <NUM> may have higher kinetic energy to be released by expanding in the direction of its longitudinal axis to the expanded or relaxed state illustrated in <FIG> and <FIG>, thereby moving inner retainer <NUM> from the second position to the first position illustrated in <FIG> and <FIG> illustrates attachment member <NUM> held within receptacle <NUM> defined by outer retainer <NUM> by inner retainer <NUM> being in the first position. Receptacle <NUM> is configured, e.g., sized and shaped, to retain attachment member <NUM> while allowing distal portion <NUM> of inner retainer <NUM> to move past the attachment member, e.g., through passageway <NUM>. As illustrated in <FIG>, at least third portion <NUM> of distal portion <NUM> of inner retainer <NUM> may contact attachment member <NUM> of IMD <NUM> when the attachment member is positioned within receptable <NUM>, e.g., when inner retainer <NUM> is in the first position. As described herein, third portion <NUM> may secure attachment member <NUM> within receptacle <NUM> and help ensure substantially constant physical contact between attachment member <NUM> and at least third portion <NUM> of inner retainer <NUM>. The physical contact between attachment member <NUM> and inner retainer <NUM> enabled by third portion <NUM> may provide substantially constant electrical contact for conduction of electrical signals, e.g., for impedance monitoring, from IMD <NUM> to a proximal portion of tether assembly <NUM>.

<FIG> is an exploded view of a distal portion of another example tether assembly <NUM> including another example tether assembly <NUM> and a pull wire <NUM>, where a distal portion <NUM> of an inner retainer <NUM> of tether head assembly <NUM> is outlined. <FIG> is a plan view of the outlined portion of <FIG>, including distal portion <NUM> of inner retainer <NUM> in conjunction with a distal portion <NUM> of pull wire <NUM>. <FIG> is a plan view of distal portion <NUM> of inner retainer <NUM> received within an outer retainer <NUM> of tether head assembly <NUM>. <FIG> is a cross-sectional view of tether head assembly <NUM> and a proximal portion of IMD <NUM>, where the cross-section is taken along a plane parallel to a longitudinal axis of the tether head assembly and a longitudinal axis of the IMD. Except as noted herein, tether assembly <NUM> and tether head assembly <NUM> may be substantially similar to tether assembly <NUM> and tether head assembly <NUM> described above with respect to <FIG>. For example, components of tether assembly <NUM> and tether head assembly <NUM> having the same reference numbers as components in tether assembly <NUM> and tether head assembly <NUM> may be configured and function as described with respect to <FIG>.

In the example of <FIG>, inner retainer <NUM> differs from inner retainer <NUM> described above with respect to <FIG>. Like inner retainer <NUM>, inner retainer <NUM> includes a proximal portion <NUM> received in a channel defined by a proximal portion <NUM> of outer retainer <NUM>. Inner retainer <NUM> also includes a distal portion <NUM> that is supported by groove <NUM> defined by However, distal portion <NUM> of inner retainer <NUM> does not include portions having different thickness, e.g., like portions <NUM>, <NUM>, and <NUM> of distal portion <NUM> of inner retainer <NUM>. In some examples, distal portion <NUM> defines a substantially constant thickness along its length. Attachment member <NUM> may apply force to distal end <NUM> of inner retainer <NUM> and move inner retainer <NUM> to the second position as elastically-compressible member <NUM> is compressed, thereby allowing attachment member <NUM> to pass through passageway <NUM> and into receptacle <NUM>. Inner retainer <NUM> may return to the first position, e.g., in response to longitudinal expansion of elastically-compressible member <NUM>, to retain attachment member <NUM> in receptacle <NUM>, as shown in <FIG>. However, distal portion <NUM> may not include a ramped or elevated surface to contact attachment member <NUM>, e.g., as provided by portion <NUM> of distal portion <NUM> of inner retainer <NUM>. distal portion <NUM> of outer retainer <NUM>. Like inner retainer <NUM>, distal portion <NUM> of inner retainer <NUM> extends into aperture <NUM> to reduce a size of passageway <NUM> when inner retainer <NUM> is in the first position and elastically-compressible member <NUM> is in its relaxed stat.

<FIG> also illustrate a different coupling of pull wire <NUM> and inner retainer <NUM> then the coupling of pull wire <NUM> to inner retainer <NUM>. In particular, pull wire <NUM> includes a bent distal portion <NUM>. Proximal portion <NUM> of inner retainer <NUM> defines a notch or other corresponding feature (<FIG>) configured to receive bent distal portion <NUM>. When pull wire <NUM> is actuated, distal portion <NUM> may bear against proximal portion <NUM> to move inner retainer <NUM> from the first position to the second position. In some examples, the coupling of pull wire <NUM> and inner retainer <NUM> illustrated in <FIG> may allow some relative movement between these structures, e.g., in response to bending and changes in length of pull wire <NUM> during an implant procedure.

<FIG> is a functional block diagram illustrating an example configuration of IMD <NUM>. As shown in <FIG>, IMD <NUM> includes processing circuitry <NUM>, sensing circuitry <NUM>, therapy delivery circuitry <NUM>, sensors <NUM>, communication circuitry <NUM>, and memory <NUM>. In some examples, memory <NUM> includes computer-readable instructions that, when executed by processing circuitry <NUM>, cause IMD <NUM> and processing circuitry <NUM> to perform various functions attributed to IMD <NUM> and processing circuitry <NUM> herein. Memory <NUM> may include any volatile, non-volatile, magnetic, optical, or electrical media, such as a random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically-erasable programmable ROM (EEPROM), flash memory, or any other digital media.

Processing circuitry <NUM> may include fixed function circuitry and/or programmable processing circuitry. Processing circuitry <NUM> may include any one or more of a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or equivalent discrete or analog logic circuitry. In some examples, processing circuitry <NUM> may include multiple components, such as any combination of one or more microprocessors, one or more controllers, one or more DSPs, one or more ASICs, or one or more FPGAs, as well as other discrete or integrated logic circuitry. The functions attributed to processing circuitry <NUM> herein may be embodied as software, firmware, hardware or any combination thereof.

In some examples, processing circuitry <NUM> may receive (e.g., from an external device), via communication circuitry <NUM>, a respective value for each of a plurality of cardiac sensing parameters, cardiac therapy parameters (e.g., cardiac pacing parameters), and/or electrode vectors. Processing circuitry <NUM> may store such parameters and/or electrode vectors in memory <NUM>.

Therapy delivery circuitry <NUM> and sensing circuitry <NUM> are electrically coupled to electrodes <NUM>, which may correspond to electrodes <NUM> and <NUM> (<FIG> and <FIG>). Processing circuitry <NUM> is configured to control therapy delivery circuitry <NUM> to generate and deliver electrical therapy to heart <NUM> via electrodes <NUM>. Electrical therapy may include, for example, pacing pulses, or any other suitable electrical stimulation. Processing circuitry <NUM> may control therapy delivery circuitry <NUM> to deliver electrical stimulation therapy via electrodes <NUM> according to one or more therapy parameter values, which may be stored in memory <NUM>. Therapy delivery circuitry <NUM> may include capacitors, current sources, and/or regulators, in some examples.

In addition, processing circuitry <NUM> is configured to control sensing circuitry <NUM> to monitor signals from electrodes <NUM> in order to monitor electrical activity of heart <NUM>. Sensing circuitry <NUM> may include circuits that acquire electrical signals, such as filters, amplifiers, and analog-to-digital circuitry. Electrical signals acquired by sensing circuitry <NUM> may include intrinsic and/or paced cardiac electrical activity, such as atrial depolarizations and/or ventricular depolarizations. Sensing circuitry <NUM> may filter, amplify, and digitize the acquired electrical signals to generate raw digital data. Processing circuitry <NUM> may receive the digitized data generated by sensing circuitry <NUM>. In some examples, processing circuitry <NUM> may perform various digital signal processing operations on the raw data, such as digital filtering. In some examples, in addition to sensing circuitry <NUM>, IMD <NUM> optionally may include sensors <NUM>, which may one or more pressure sensors and/or one or more accelerometers, as examples. Communication circuitry <NUM> may include any suitable hardware (e.g., an antenna), firmware, software, or any combination thereof for communicating with another device, e.g., external to the patient.

<FIG> is a flow diagram illustrating an example technique for using tether assembly <NUM> of <FIG> and tether assembly <NUM> of <FIG>. Although the example technique of <FIG> is described in the context of tether assembly <NUM> and tether head assembly <NUM> of <FIG>, the example technique should not be understood to be so limited, but instead may be applied to a method of using tether assembly <NUM> and tether head assembly <NUM> of <FIG> or any other tether assembly configured according to the techniques of this disclosure.

The example technique of <FIG> includes coupling tether head assembly <NUM> of tether assembly <NUM> to attachment member <NUM> of IMD <NUM> (<NUM>). For example, a clinician may hold tether head assembly <NUM> in one hand and press attachment member <NUM> into passageway <NUM> defined by outer member <NUM>, e.g., against distal end <NUM> of inner retainer <NUM>, thereby moving inner retainer <NUM> to the second position as attachment member <NUM> moves through passageway <NUM> to receptacle <NUM> and as elastically-compressible member <NUM> is compressed. The clinician then may release his or her hold on IMD <NUM> once attachment member <NUM> is received within receptacle <NUM> to allow inner retainer <NUM> to return to the first position via the biasing of inner retainer <NUM> to the first position provided by elastically-compressible member <NUM>.

The clinician then may position IMD <NUM> attached to tether head assembly <NUM> at a treatment site of a patient (e.g., a treatment site within heart <NUM>) with attachment member <NUM> received within receptacle <NUM> (<NUM>). In some examples, IMD <NUM> and tether assembly <NUM> may be carried within a delivery catheter <NUM> as it is advanced to the treatment site, e.g., as described above with respect to <FIG> and <FIG>. In some examples, the clinician may determine whether IMD <NUM> is properly positioned relative to heart <NUM> based on an impedance signal sensed via an electrical path including IMD <NUM>, attachment member <NUM>, and one or more components of tether member <NUM> (e.g., inner retainer <NUM> and/or or one or more other components of tether head assembly <NUM>). The clinician then may advance fixation members <NUM> into the tissue of heart <NUM> to fix IMD <NUM> at the implant site (<NUM>).

Once satisfied with the positioning and fixation of IMD <NUM> to tissue of heart <NUM>, the clinician may separate attachment member <NUM> of IMD <NUM> from tether head assembly <NUM>. For example, the clinician may proximally move pull wire <NUM>, such as by applying force to an actuator of a tether handle assembly attached at a proximal end of pull wire <NUM>, to move inner retainer <NUM> from the first position to the second position (<NUM>). With inner retainer <NUM> in the second position, the clinician may proximally move tether assembly <NUM> to remove attachment member <NUM> from tether head assembly <NUM> (<NUM>). For example, proximal movement of tether assembly <NUM> when inner retainer <NUM> is in the second position may enable attachment member <NUM> to pass from receptacle <NUM>, through passageway <NUM>, and out from distal end <NUM> of outer retainer <NUM>.

<FIG> illustrate a proximal portion of another example tether assembly <NUM> including a tether handle assembly <NUM>. <FIG> is a plan view of tether handle assembly <NUM>, and <FIG> is an exploded plan view of tether handle assembly <NUM>. As illustrated in <FIG>, tether handle assembly <NUM> may be coupled to a proximal end of an elongate member <NUM> of tether assembly <NUM>, which may correspond with and be substantially similar to elongate member <NUM> illustrated in <FIG>. In some examples, tether handle assembly <NUM> may be a handle assembly of a tether assembly including either of tether head assemblies <NUM> or <NUM>. In some such examples, tether head assembly <NUM> or <NUM> may be coupled to elongate body <NUM> in a manner similar to a manner in which tether head assembly <NUM> or <NUM> may be coupled to elongate body <NUM> as described above. The tether head assemblies and tether handle assemblies described herein may be used in any suitable combination with one another as part of a tether assembly. Thus, example combinations of the tether head assemblies and tether handle assemblies described are exemplary and should not be understood to be limiting.

Tether handle assembly <NUM> includes a housing <NUM>. A pull wire (not shown) may extend through elongate member <NUM>, and may include a proximal end received within housing <NUM> of tether handle assembly <NUM>. Tether handle assembly <NUM> further may include a button <NUM> defining a proximal surface <NUM>. Button <NUM> may be configured to cause a proximal movement of the pull wire when a distally-directed force is applied to proximal surface <NUM> of button <NUM>. Proximal movement of the pull wire may enable movement of an inner retainer <NUM> or <NUM> from a first position to a second position, e.g., for removal of attachment member <NUM> of IMD <NUM> from a tether head assembly <NUM> or <NUM>, as described herein.

Housing <NUM> of tether handle assembly <NUM> may include a shroud <NUM> that extends proximally of proximal surface <NUM> of button <NUM> such that proximal surface <NUM> is recessed within housing <NUM>. Shroud <NUM> thus may help reduce a possibility of accidental application of a distally-directed force to proximal surface <NUM>, which may help reduce a possibility of accidental deployment of IMD <NUM> during a procedure for delivering IMD <NUM>.

Tether handle assembly <NUM> further may include a strain relief member <NUM> attached to housing <NUM> at a distal end <NUM> defined by housing <NUM>. The pull wire of tether assembly <NUM> may extend through elongate member <NUM> and be received within strain relief member <NUM>. In addition to providing strain relief for elongate member <NUM> and a pull wire where the pull wire enters distal end <NUM> of housing <NUM>, strain relief member <NUM> may help enable sensing of an impedance signal or enable electrical testing of IMD <NUM> during a procedure to deliver IMD <NUM> at a treatment site.

In some examples, strain relief member <NUM> may be electrically conductive, and electrically coupled to a conductive element of elongate body <NUM>. In such examples, strain relief member <NUM> may enable sensing of an impedance signal or other electrical signal via an electrical path including IMD <NUM>, attachment member <NUM>, inner retainer <NUM> or <NUM>, other conductive components of tether head assembly <NUM> or <NUM>, elongate member <NUM>, and strain relief member <NUM>. For example, a clinician may couple an electrically conductive clip or similar connector from a device external to the patient during an implant procedure to strain relief member <NUM> to effectively electrically couple the external device to housing <NUM> of IMD <NUM>. A return electrode may be attached to patient and coupled to the external device to provide the return path.

As discussed above with respect to <FIG>, a clinician may determine whether cup <NUM> and/or IMD <NUM> is properly positioned relative to tissue <NUM> of heart <NUM>, and/or whether IMD <NUM> is properly fixed to tissue by fixation members <NUM>, based on an impedance signal sensed via such an electrical path. In this manner, strain relief member <NUM> may help enable a clinician to determine whether IMD <NUM> is properly placed at a treatment site.

As illustrated in <FIG>, the interior of housing <NUM> may define at least a portion of a curved channel <NUM> that defines a first end <NUM> and a second end <NUM>. In the illustrated example, an intermediate portion <NUM> of curved channel <NUM> between first end <NUM> and second end <NUM> may be separately formed and positioned within housing <NUM> during assembly of handle assembly <NUM>, e.g., for each of manufacturing of curved channel <NUM>. Tether handle assembly <NUM> further may include a force transmitter <NUM> received within curved channel <NUM>. In the illustrated example, force transmitter <NUM> includes a plurality of balls (e.g., ball-bearings) or other similar objects that are movable through channel <NUM>. However, other suitable objects configured to be received within channel <NUM> and movable therethrough may be used instead of or in addition to the plurality of balls.

Tether handle assembly <NUM> further may include a slidable member <NUM> received within housing <NUM> such that a channel portion <NUM> of slidable member <NUM> is received within channel <NUM> at first end <NUM> of channel <NUM>. As illustrated in <FIG>, a proximal end <NUM> of pull wire <NUM> may extend from elongate member <NUM>, through strain relief member <NUM>, and be received within housing <NUM>. Proximal end <NUM> of pull wire <NUM> is attached to slidable member <NUM>. In the illustrated example, proximal end <NUM> of pull wire <NUM> is received within an anchor member <NUM>, which may enable slidable member <NUM> to retain proximal end <NUM> of pull wire <NUM>, thereby attaching proximal end <NUM> of pull wire <NUM> to slidable member <NUM>.

Button <NUM> may include an elongate distal portion <NUM> received within channel <NUM> at second end <NUM>. Distal portion <NUM> of button <NUM> may be configured to move force transmitter <NUM> within channel <NUM> toward first end <NUM> and into contact with channel portion <NUM> of slidable member <NUM>. For example, when button <NUM> is moved from a first position to a second position in response to application of a distally-directed force to proximal surface <NUM> of button (e.g., by a clinician pressing the button), distal portion <NUM> of button <NUM> may contact force transmitter <NUM> and move the force transmitter through channel <NUM> towards first end <NUM>. Since force transmitter <NUM> is in contact with portion <NUM> of slidable member <NUM> received within channel <NUM>, force transmitter <NUM> applies a proximally-directed force to channel portion <NUM>, and thus to slidable member <NUM>. This proximally-directed force causes slidable member <NUM> and pull wire <NUM> to move proximally. In this manner, channel <NUM> and force transmitter <NUM> may be configured to translate a distally-directed force applied to proximal surface <NUM> of button <NUM> to a proximally-directed force applied to slidable member <NUM> and pull wire <NUM>. In some examples, a clinician may find applying a distally-directed force (i.e., a pushing force) to button <NUM> to release IMD <NUM> to be intuitive and/or otherwise easier to use than some other handle assembly configurations.

In some examples, tether handle assembly <NUM> may further include an elastically-compressible member <NUM>, e.g., spring, positioned within housing <NUM> proximal to slidable member <NUM>, which in some examples may help control movement of slidable member <NUM>. When handle assembly <NUM> is in an assembled configuration, button <NUM> may surround at least a proximal portion of elastically-compressible member <NUM>. Proximal movement of slidable member <NUM> may axially compresses elastically-compressible member <NUM> relative to its longitudinal axis. In some examples, elastically-compressible member <NUM> may help control proximal movement of slidable member <NUM> as slidable member <NUM> is moved proximally within housing <NUM>. Additionally, or alternatively, elastically-compressible member <NUM> may be configured to bias slidable member <NUM> and/or button <NUM> to respective first positions thereof, e.g., their positions when button <NUM> is not pushed distally inward relative to housing <NUM>, as illustrated and described with respect to <FIG>. Thus, when a physician releases button <NUM>, pull wire <NUM> may be moved distally by elastically-compressible member <NUM> to aid in returning a tether head assembly <NUM> or <NUM> to a closed configuration, e.g., returning an inner retainer <NUM> or <NUM> to the first position, in some examples. Some example tether assemblies may include both an elastically-compressible member in the handle assembly, e.g., elastically compressible member <NUM>, and an elastically-compressible member in the head assembly, e.g., elastically compressible member <NUM>, while other tether assemblies may include only one of the elastically-compressible members to, for example, provide the functionality of returning a tether head assembly to a closed configuration, e.g., returning an inner retainer to the first position.

In some examples, as illustrated in <FIG>, housing <NUM> may comprise a removable cover portion <NUM>, which may facilitate manufacture of tether handle assembly <NUM>. Tether handle assembly <NUM> further may include an elastically-stretchable band <NUM>, which may be configured to be placed over a distal portions of housing <NUM> and cover <NUM> to help retain components of handle assembly <NUM> in the assembled configuration illustrated in <FIG>.

<FIG> are side views of tether handle assembly <NUM> of <FIG> and <FIG> with a portion of housing <NUM> removed, illustrating movement of force transmitter <NUM>, slidable member <NUM>, and a pull wire <NUM> in response to movement of button <NUM> from a first position <NUM> (<FIG>) to a second position <NUM> (<FIG>). First position <NUM> may be a "home" or uncompressed position of button <NUM>. Second position <NUM> may be a compressed or depressed position of button <NUM>. Elastically-compressible member <NUM> may bias button <NUM> to first position <NUM>.

As shown in <FIG>, as button <NUM> is pushed inward into shroud <NUM> with distal force in the direction of arrow <NUM>, distal portion <NUM> of button <NUM> moves distally in the direction of arrow <NUM> within channel <NUM>. As distal portion <NUM> moves distally within channel <NUM>, distal portion <NUM> pushes force transmitter <NUM> within channel toward first end <NUM> (<FIG>). In this manner, force transmitter <NUM> transmits the distally-directed force from button <NUM> to a proximally-directed force, in the direction of arrow <NUM>, against channel portion <NUM> of slidable member <NUM>. In response to the proximally-directed force, slidable member <NUM> and attached pull wire <NUM> may move proximally, in the direction of arrow <NUM>, which may result in opening of a tether head member <NUM> or <NUM> at a distal end of a tether assembly, as described herein.

As illustrated in <FIG>, housing <NUM> and button <NUM> may include features configured to interact, e.g., abut, when button <NUM> is in second position <NUM>. Such features may prevent further distal movement of button <NUM> beyond second position <NUM>. In the illustrated example, housing <NUM> defines an internal ledge <NUM> and button <NUM> includes a distal overhang <NUM>.

As button <NUM> moves from first position <NUM> to second position <NUM> in distal direction <NUM>, and slidable member <NUM> correspondingly moves in proximal direction <NUM>, elastically-compressible member <NUM> is compressed between button <NUM> and slidable member <NUM>, storing potential energy. When a physician releases button <NUM>, elastically-compressible member <NUM> may expand longitudinally, releasing the stored energy, and moving button <NUM> and slidable member <NUM> in directions <NUM> and <NUM>, respectively, until button <NUM> is once again in first position <NUM>. As slidable member <NUM> moves distally in direction <NUM>, pull wire <NUM> may also move distally to aid in returning a tether head assembly <NUM> or <NUM> in a closed configuration, e.g., returning an inner retainer <NUM> or <NUM> to first position, in some examples.

<FIG> are plan views of components of tether handle assembly <NUM> of tether assembly <NUM> of <FIG> and <FIG>, illustrating an example technique for assembling tether handle assembly <NUM>. As illustrated in <FIG> pull wire <NUM> extends out of a proximal end of elongate member <NUM>, and through a strain relief member <NUM> at the proximal end of elongate member <NUM>. An anchor member <NUM> may be formed on or attached to proximal end <NUM> of pull wire <NUM>.

As illustrated in <FIG>, housing <NUM> may define a receptacle <NUM> configured to receive strain relief member <NUM>, and a channel <NUM> configured to receive pull wire <NUM>. Anchor member <NUM> may be positioned on an opposite end of channel <NUM> from strain relief member <NUM>. This configuration, including the fixation of strain relief member <NUM> in receptacle <NUM> of housing <NUM>, may provide strain relief for the connection of elongate member <NUM> to handle assembly <NUM>.

<FIG> illustrates the insertion of intermediate portion <NUM> to complete curved channel <NUM>, which also closes channel <NUM>. <FIG> illustrates slidable member <NUM> inserted into housing <NUM>. Slidable member <NUM> may define a feature (not shown) configured to receive anchor member <NUM>, thereby coupling pull wire <NUM> to slidable member <NUM>.

<FIG> illustrates elastically-compressible member <NUM> inserted into housing <NUM>, and <FIG> illustrates button <NUM> inserted into housing <NUM>. Slidable member <NUM> and button <NUM> may include features to hold elastically-compressible member <NUM> between them. <FIG> also illustrates distal portion <NUM> of button <NUM> inserted at second end <NUM> of channel <NUM>.

<FIG> illustrates force transmitter <NUM> inserted into channel <NUM> between distal portion <NUM> of button <NUM> and channel portion <NUM> of slidable member <NUM>. <FIG> illustrates removable cover <NUM> attached to housing <NUM>, and <FIG> illustrates elastically-stretchable band <NUM> placed over a distal portions of housing <NUM> and cover <NUM> to help retain components of tether handle assembly <NUM> in the assembled configuration. <FIG> also illustrate that housing <NUM> may define features to aid the usability of handle assembly <NUM>, such as depression <NUM> and ridge <NUM>, which may aid a physician in orienting and gripping tether handle assembly <NUM>.

<FIG> are plan views of another example tether handle assembly <NUM>. Tether handle assembly <NUM> may be substantially similar to tether handle assembly <NUM> described with reference to <FIG>. For example, components of tether handle assembly <NUM> having the same reference numbers as components tether handle assembly <NUM> may be configured and function as described with respect to <FIG>.

Unlike tether handle assembly <NUM>, tether handle assembly <NUM> includes a cover <NUM> for button <NUM> (<FIG>). Housing <NUM> of tether handle assembly <NUM>, e.g., shroud portion <NUM> of the housing, may define a depression <NUM> configured to allow a user's finger to access a tab <NUM> formed on cover <NUM> to move cover <NUM> away from button <NUM>. Cover <NUM> may be included on tether handle assembly <NUM> to reduce the likelihood that button <NUM> is inadvertently pressed, and IMD <NUM> deployed, during an implantation procedure for IMD <NUM> using tether handle assembly <NUM>.

A band <NUM> may connect cover <NUM> to a collar <NUM>. Collar <NUM> and band <NUM> may be configured to keep cover <NUM> attached to tether handle assembly <NUM> when cover <NUM> is moved away from button <NUM>, e.g., as shown in <FIG>. Band <NUM> may be configured to space cover <NUM> from away from a proximal opening of shroud portion <NUM> to facilitate ease of user access to proximal surface <NUM> of button <NUM> when cover <NUM> is moved, e.g., as shown in <FIG> and <FIG>. Cover <NUM>, collar <NUM>, and band <NUM> may be formed of any material, such as a polymer, and may be formed from, e.g., molded as, a single piece of the material. Shroud portion <NUM> and/or other portions of housing <NUM> may be configured with corresponding features to receive collar <NUM> and band <NUM>, e.g., to secure them to tether handle assembly <NUM> and provide a substantially even outer surface for tether handle assembly <NUM>.

As illustrated in <FIG> and <FIG>, cover <NUM> may include a reduced diameter plug portion <NUM>. As illustrated in <FIG>, the proximal opening of shroud portion <NUM> may define an expanded diameter shelf <NUM> configured to receive plug portion <NUM>. Plug portion <NUM> and shelf <NUM> may be configured to interact secure cover <NUM> within the proximal opening of shroud portion <NUM>, e.g., via friction fit, threading, or other attachment mechanisms.

<FIG> are plan views of a proximal end of another example tether assembly <NUM> including another example tether handle assembly <NUM> coupled to a proximal end of an elongate member <NUM>. <FIG> is an exploded plan view of tether handle assembly <NUM>. <FIG> are plan views of tether handle assembly <NUM>, with a portion of a housing <NUM> of tether handle assembly <NUM> removed to illustrate an example, arrangement, interaction, and movement of components of tether handle assembly <NUM> during use.

Elongate member <NUM> of tether assembly <NUM> may correspond with and be substantially similar to elongate member <NUM> illustrated in <FIG>. In some examples, tether handle assembly <NUM> may be a handle assembly of tether assembly including either of tether head assemblies <NUM> or <NUM>. In some such examples, tether head assembly <NUM> or <NUM> may be coupled to elongate body <NUM> in a manner similar to a manner in which tether head assembly <NUM> or <NUM> may be coupled to elongate body <NUM> as described above. The tether head assemblies and tether handle assemblies described herein may be used in any suitable combination with one another as part of a tether assembly. Thus, example combinations of the tether head assemblies and tether handle assemblies described are exemplary and should not be understood to be limiting.

In the example illustrated by <FIG>, housing <NUM> includes two housing portions 458A and 458B. Housing portions 458A and 458B may be press fit together or otherwise connected during assembly of tether handle assembly <NUM> to form housing <NUM>, e.g., after the components of tether handle assembly <NUM> described herein are suitably arranged. Housing portions 458A and 458B may be molded components of plastic or another polymer in some examples.

A pull wire <NUM> (<FIG>) may extend through elongate member <NUM>, and may include a proximal end <NUM> received within housing <NUM> of tether handle assembly <NUM>. Tether handle assembly <NUM> further may include a button <NUM> defining a proximal surface <NUM>, and configured to cause a proximal movement of pull wire <NUM> when a distally-directed force is applied to the proximal surface <NUM> of button <NUM>. Proximal movement of the pull wire <NUM> may enable movement of an inner retainer <NUM> or <NUM> from a first position to a second position, e.g., for removal of attachment member <NUM> of IMD <NUM> from a tether head assembly <NUM> or <NUM>, as described herein with respect to <FIG>.

Tether handle assembly <NUM> further may include a strain relief member <NUM> attached to housing <NUM> at a distal end of housing <NUM>. Elongate member <NUM> may be attached to strain relief member <NUM> and pull wire <NUM> may be received within strain relief member <NUM>. In addition to providing strain relief for elongate member <NUM> and pull wire <NUM> where the elongate member attaches to and the pull wire enters housing <NUM>, strain relief member <NUM> may be electrically conductive and help enable sensing of an impedance signal or enable electrical testing of IMD <NUM> during a procedure to deliver IMD <NUM> at a treatment site, as described above with respect to strain relief member <NUM>.

As illustrated in <FIG>, button <NUM> includes a carriage <NUM> within housing defining interior teeth <NUM> configured to interact with corresponding teeth of gears 474A and 474B (collectively, "gears <NUM>"). Button <NUM> may be a machined and/or molded. Tether handle assembly <NUM> further includes a slidable member <NUM> comprising teeth <NUM> on opposing sides of the slidable member. Teeth <NUM> of slidable member <NUM> are configured to interact with the teeth of gears <NUM>. Slidable member <NUM> defines a longitudinal lumen through which distal end <NUM> of pull wire <NUM> extends, and into which a distal portion of a sleeve <NUM> may be inserted. Sleeve <NUM> may serve to attach pull wire <NUM> to slidable member <NUM> by defining a lumen to receive proximal end <NUM> of pull wire <NUM>. Proximal end <NUM> of pull wire <NUM> may be fixed to sleeve <NUM> by welding, crimping, capping, adhesive, and/or using an anchor member (e.g., anchor member <NUM> of FIG. 7B) as examples.

Tether handle assembly <NUM> further includes elastically-compressible members 492A, 492B, and 492C (collectively, "elastically-compressible members <NUM>"), e.g., springs, within housing <NUM>. The longitudinal lumen defined by slidable member <NUM> receives elastically-compressible member 492C, which dampens the proximal motion of pull wired <NUM> as button <NUM> is pushed distally.

<FIG> are side views of tether handle assembly <NUM> with housing portion 458A removed, illustrating movement of carriage <NUM>, gears <NUM>, slidable member <NUM>, and pull wire <NUM> in response to movement of button <NUM> from a first position (<FIG>) to a second position (<FIG>). The first position illustrated in <FIG> may be a "home" or uncompressed position of button <NUM>. The second position illustrated in <FIG> may be a compressed or depressed position of button <NUM>. Elastically-compressible members 492A and 492B may bias button <NUM> to the first position.

As shown in <FIG>, as button <NUM> is pushed inward with distal force in the direction of arrow <NUM>, carriage <NUM> moves distally in the direction of arrow <NUM> within housing <NUM>. As carriage <NUM> moves distally, teeth <NUM> rotate gears <NUM>. As gears <NUM> rotate against teeth <NUM> of slidable member <NUM>, slidable member <NUM> is moved proximally in the direction of arrow <NUM>, and pull wire <NUM> connected to slidable member <NUM> is pulled proximally in the direction of arrow <NUM>. In this manner, gears <NUM> transfer the distally-directed force from button <NUM> to a proximally-directed force, in the direction of arrow <NUM>, in response to which pull wire <NUM> may move proximally, in the direction of arrow <NUM>, which may result in opening of a tether head member <NUM> or <NUM> at a distal end of tether assembly <NUM>, in the manner described herein.

As button <NUM> moves from the first position (<FIG>) to the second position (<FIG>) in distal direction <NUM>, elastically-compressible members 492A and 492B are compressed between button <NUM> and features of housing <NUM>, storing potential energy. When a physician releases button <NUM>, elastically-compressible members 492A and 492B may expand longitudinally, releasing the stored energy, and moving button <NUM> and slidable member <NUM> in directions <NUM> and <NUM>, respectively, until button <NUM> is once again in the first position. As slidable member <NUM> moves distally in direction <NUM>, pull wire <NUM> may also move distally to aid in returning a tether head assembly <NUM> or <NUM> in a closed configuration, e.g., returning an inner retainer <NUM> or <NUM> to first position, in some examples.

<FIG> is a flow diagram illustrating an example technique for using a tether assembly including a tether handle assembly as described with respect to <FIG> and a tether head assembly as described with respect to <FIG>. Although the example technique of <FIG> is described in the context tether head assembly <NUM> of <FIG> and tether handle assembly <NUM> of <FIG>, the example technique should not be understood to be so limited, but instead may be applied to a method of using tether head assembly <NUM> of <FIG>, handle assemblies <NUM> and <NUM> of <FIG>, or any other tether head assemblies or tether handle assemblies configured according to the techniques of this disclosure.

Like the example technique of <FIG>, the example technique of <FIG> includes positioning IMD <NUM> attached to tether head assembly <NUM> at a treatment site of a patient (e.g., a treatment site within heart <NUM>) with attachment member <NUM> received within receptacle <NUM> (<NUM>). In some examples, the clinician may determine whether IMD <NUM> is properly positioned relative to heart <NUM> based on an impedance signal sensed via an electrical path including IMD <NUM>, attachment member <NUM>, one or more components of tether head assembly <NUM>, an elongate member, and strain relief member <NUM>. The clinician then may advance fixation members <NUM> into the tissue of heart <NUM> to fix IMD <NUM> at the implant site (<NUM>).

Once satisfied with the positioning and fixation of IMD <NUM> to tissue of heart <NUM>, the clinician may separate attachment member <NUM> of IMD <NUM> from tether head assembly <NUM>. In the example of <FIG>, the clinician pushes distally on proximal surface <NUM> of button <NUM> of tether handle assembly <NUM> (<NUM>). Tether handle assembly <NUM> translates the distal force to a proximal force, to proximally move pull wire <NUM> and open tether head assembly <NUM> (<NUM>). For example, distal portion <NUM> of handle <NUM> may move distally in channel <NUM> and push force transmitter <NUM> through channel <NUM> against channel portion <NUM> of slidable member <NUM>, which may move slidable member <NUM> in a proximal direction. Pull wire <NUM>, connected to slidable member <NUM>, is thus moved in the proximal direction.

In other examples, distal movement of carriage <NUM> of button <NUM> rotates gears <NUM>. The rotation of gears <NUM> moves slidable member <NUM>, to which pull wire <NUM> is connected, proximally. In either case, with tether head assembly <NUM> open, the clinician may proximally move tether assembly <NUM> to remove attachment member <NUM> from tether head assembly <NUM> (<NUM>).

<FIG> is a side view of another example tether assembly <NUM> including another example tether handle assembly <NUM>. <FIG> is an exploded plan view of tether assembly <NUM> and tether handle assembly <NUM>. <FIG> are perspective views of tether handle assembly <NUM> with a portion <NUM> of the housing <NUM> removed, illustrating different positions of a lock member <NUM> and a plunger <NUM> of tether handle assembly <NUM> during use.

As illustrated in <FIG>, tether handle assembly <NUM> may be coupled to a proximal end of an elongate member <NUM> of tether assembly <NUM>, which may correspond with and be substantially similar to elongate member <NUM> illustrated in <FIG>. In some examples, tether handle assembly <NUM> may be a tether handle assembly of a tether assembly including either of tether head assemblies <NUM> or <NUM>. In some such examples, tether head assembly <NUM> or <NUM> may be coupled to elongate body <NUM> in a manner similar to a manner in which tether head assembly <NUM> or <NUM> may be coupled to elongate body <NUM> as described above. The tether head assemblies and tether handle assemblies described herein may be used in any suitable combination with one another as part of a tether assembly. Thus, example combinations of the tether head assemblies and tether handle assemblies described are exemplary and should not be understood to be limiting.

Tether handle assembly <NUM> includes a housing <NUM>. A pull wire <NUM> may extend through elongate member <NUM>, and may include a proximal end received within housing <NUM> of tether handle assembly <NUM>. Tether handle assembly <NUM> further may include a plunger <NUM> configured to cause a proximal movement of the pull wire when pulled by a user. Proximal movement of the pull wire may enable movement of an inner retainer <NUM> or <NUM> from a first position to a second position, e.g., for removal of attachment member <NUM> of IMD <NUM> from a tether head assembly <NUM> or <NUM>, as described with respect to <FIG>.

Tether handle assembly <NUM> further may include a strain relief member <NUM> attached to housing <NUM> at a distal end of housing <NUM>. Elongate member <NUM> may be attached to strain relief member <NUM>, and pull wire <NUM> may be received within strain relief member <NUM>. In addition to providing strain relief for elongate member <NUM> and pull wire <NUM> where the elongate member attaches to and the pull wire enters housing <NUM>, strain relief member <NUM> be electrically conductive and may help enable sensing of an impedance signal or enable electrical testing of IMD <NUM> during a procedure to deliver IMD <NUM> at a treatment site, as described herein with respect to strain relief member <NUM>.

In the illustrated example, housing <NUM> includes removable cover portion <NUM>, which may facilitate manufacture of handle assembly <NUM>. Handle assembly <NUM> further may include an elastically-stretchable band <NUM>, which may be configured to be placed over a distal portions of housing <NUM> and cover <NUM> to help retain components of tether handle assembly <NUM> in the assembled configuration illustrated in <FIG>.

As illustrated in <FIG>, tether handle assembly <NUM> includes a lock member <NUM>. Lock member <NUM> include opposing buttons 572A and 572B (collectively, "buttons <NUM>"). Lock member <NUM> also defines a keyhole <NUM>. Tether handle assembly <NUM> further comprises a slidable member <NUM> comprising a protrusion <NUM>. Slidable member <NUM> is slidable through an inner channel defined by lock member <NUM> so long as protrusion <NUM> is aligned with keyhole <NUM> defined by lock member <NUM>. As illustrated in <FIG>, a proximal end <NUM> of pull wire <NUM> may extend from elongate member <NUM>, through strain relief member <NUM>, and be received within housing <NUM>. Proximal end <NUM> of pull wire <NUM> is attached to slidable member <NUM>. In the illustrated example, proximal end <NUM> of pull wire <NUM> is received within an anchor member <NUM>, which may enable slidable member <NUM> to retain proximal end <NUM>, thereby attaching pull wire <NUM> to slidable member <NUM>.

Plunger <NUM> may include a plug <NUM> received within a collar <NUM>. Collar <NUM> defines an interior passageway configured to receive a proximal portion of slidable member <NUM>, including bayonet locks <NUM>. Plug <NUM> is insertable into the interior passageway of collar <NUM> between bayonet locks <NUM>, to urge the bayonet locks outward and attach plunger <NUM> to slidable member <NUM>.

In some examples, tether handle assembly <NUM> may further include an elastically-compressible member <NUM>, e.g., spring, positioned between an interior surface of housing <NUM> on one end, and an enlarged diameter portion <NUM> of slidable member <NUM> on the opposite end. Proximal movement of slidable member <NUM> may axially compresses elastically-compressible member <NUM> relative to its longitudinal axis. In some examples, elastically-compressible member <NUM> may help control proximal movement of slidable member <NUM> as slidable member <NUM> is moved proximally in response to a user pulling plunger <NUM>. Additionally, or alternatively, elastically-compressible member <NUM> may be configured to bias slidable member <NUM> and/or plunger <NUM> to respective first positions thereof, e.g., their positions when plunger <NUM> has not been pulled. Thus, when a physician releases plunger <NUM>, pull wire <NUM> may be moved distally by elastically-compressible member <NUM> to aid in returning a tether head assembly <NUM> or <NUM> in a closed configuration, e.g., returning an inner retainer <NUM> or <NUM> to first position, in some examples.

<FIG> are perspective views of tether handle assembly <NUM> with a portion <NUM> of the housing <NUM> removed, illustrating different positions of a lock member <NUM> and a plunger <NUM> of tether handle assembly <NUM> during use. <FIG> illustrates both lock member <NUM> and plunger <NUM> in their first or "home" positions. In the first position, protrusion <NUM> of slidable member <NUM> is not aligned with keyhole <NUM> of lock member <NUM>. Consequently, plunger <NUM> is prevented from being pulled distally to its second position.

<FIG> illustrates lock member <NUM> in its second position, such that protrusion <NUM> of slidable member <NUM> is not aligned with keyhole <NUM> of lock member <NUM>. A user may move lock member <NUM> to the second position by pressing on button 572A of lock member <NUM> to move lock member <NUM> transverse to a longitudinal axis of tether handle assembly <NUM>. A user may move lock member <NUM> back to the first position by pressing on button 572B, e.g., after deploying IMD <NUM>. Notably, it is easier for a user to access button 572B than button 572A in both the first and second positions of lock member <NUM>, e.g., to discourage accidental unlocking and IMD deployment.

<FIG> illustrates lock member <NUM> in its second position and plunger <NUM> having been pulled to its second position. Pulling plunger <NUM> to its second position moves pull wire <NUM> proximally and compresses elastically-compressible member <NUM>, storing potential energy. When a physician releases plunger <NUM>, elastically-compressible member <NUM> may expand longitudinally, releasing the stored energy, and moving plunger <NUM> and slidable member <NUM> distally. As slidable member <NUM> moves distally, pull wire <NUM> may also move distally to aid in returning a tether head assembly <NUM> or <NUM> in a closed configuration, e.g., returning an inner retainer <NUM> or <NUM> to first position, in some examples.

<FIG> is an exploded plan view of another example tether handle assembly <NUM>. 14B is a cross-section view of tether handle assembly <NUM>. Except as noted herein, tether handle assembly <NUM> may be substantially similar to tether handle assembly <NUM> described above with respect to <FIG>. For example, components of tether handle assembly <NUM> having the same reference numbers as components in tether handle assembly <NUM> may be configured and function as described with respect to <FIG>.

Plunger <NUM> differs from plunger <NUM> in that collar <NUM> defines an aperture <NUM>. Removable housing portion <NUM> and slidable member <NUM> also define apertures <NUM> and <NUM>, respectively. Apertures <NUM>, <NUM>, and <NUM> align to define a passageway to receive a lower portion of a lock member <NUM> of tether handle assembly <NUM> within housing <NUM>. Lock member <NUM> includes a lower post <NUM> receivable within a longitudinal lumen defined by elastically-compressible member <NUM>, which biases lock member <NUM> to a locked position. Lock member <NUM> further defines an inlet <NUM> that acts as a keyhole for lock member <NUM>. When lock member <NUM> is pressed down and into the unlocked position, compressing elastically-compressible member <NUM>, inlet <NUM> aligns with a distal edge <NUM> of aperture <NUM> defined by collar <NUM>. The alignment of inlet <NUM> and distal edge <NUM> allows plunger <NUM> to be pulled proximally. <FIG> illustrates lock member <NUM> in the unlocked position, with inlet <NUM> and distal edge <NUM> not aligned, and plunger <NUM> prevented from being pulled proximally, e.g., to open a tether head member and release an IMD.

<FIG> is an exploded plan view of another example tether handle assembly <NUM>. <FIG> is a cross-section view of tether handle assembly <NUM>. <FIG> is a plan view of a collar portion <NUM> of a plunger <NUM> of tether handle assembly <NUM>. Except as noted herein, tether handle assembly <NUM> may be substantially similar to tether handle assembly <NUM> described above with respect to <FIG>. For example, components of tether handle assembly <NUM> having the same reference numbers as components in tether handle assembly <NUM> may be configured and function as described with respect to <FIG>.

Claim 1:
A tether assembly (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) of a medical device delivery system, the tether assembly comprising:
a pull wire (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) defining a proximal end (<NUM>, <NUM>, <NUM>) and a distal end; and
a tether head assembly (<NUM>, <NUM>) comprising:
an inner retainer (<NUM>, <NUM>) comprising a proximal portion (<NUM>, <NUM>) and a distal portion (<NUM>, <NUM>), wherein the inner retainer (<NUM>, <NUM>) is coupled to and extends distally from the distal end of the pull wire (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>);
an outer retainer (<NUM>) comprising a proximal portion defining a channel (<NUM>) configured to receive the inner retainer (<NUM>, <NUM>) and a distal portion (<NUM>) defining an aperture (<NUM>), the aperture (<NUM>) comprising:
a receptacle (<NUM>) configured to receive an attachment member (<NUM>) of a medical device (<NUM>);
a passageway (<NUM>) extending from a distal end defined by the outer retainer (<NUM>) proximally to the receptacle (<NUM>), wherein the passageway (<NUM>) is narrower than the receptacle (<NUM>); and
a groove (<NUM>) extending from the distal end of the outer retainer (<NUM>) proximally at least to the receptacle (<NUM>), wherein the groove (<NUM>) has a depth that is less than a thickness of the distal portion (<NUM>, <NUM>) of the inner retainer (<NUM>, <NUM>),
wherein the inner retainer (<NUM>, <NUM>) is movable between a first position wherein the distal portion (<NUM>, <NUM>) of the inner retainer (<NUM>, <NUM>) is partially received in the groove (<NUM>) and extends into the passageway (<NUM>), thereby narrowing the passageway (<NUM>), and a second position wherein the distal portion (<NUM>, <NUM>) of the inner retainer (<NUM>, <NUM>) is positioned proximal to the passageway (<NUM>).