Patent Description:
Implantable medical devices are often placed in a subcutaneous pocket and coupled to one or more transvenous medical electrical leads carrying pacing and sensing electrodes positioned in the heart. Intracardiac pacemakers have recently been introduced that are implantable within a ventricular chamber of a patient's heart for delivering ventricular pacing pulses without the use of electrical leads. Such pacemakers or other implantable medical devices may also be able to detect the occurrence of arrhythmias, such as fibrillation, tachycardia and bradycardia, in the patient's heart. An implantable cardiac defibrillator may deliver electrical shocks to the patient's heart in response to detection of a tachycardia or fibrillation to restore a normal heartbeat in the patient. In some cases, a single implantable medical device functions as both an implantable pacemaker and implantable cardiac defibrillator.

Implantable medical devices may include electrodes and/or other elements for physiological sensing and/or therapy delivery. The electrodes and/or other elements may be implanted at target locations selected to detect a physiological condition of the patient and/or deliver one or more therapies. For example, the electrodes and/or other elements may be delivered to a target location within an atrium or ventricle to sense intrinsic cardiac signals and deliver pacing or antitachyarrhythmia shock therapy from a medical device coupled to a lead.

<CIT>, <CIT>, <CIT> and <CIT> show examples of known implantable intracardiac pacing devices.

This disclosure describes an implantable medical device (IMD) configured to position within a heart of a patient. The IMD includes a leadlet configured to extend over an extension length to cause a leadlet electrode to displace from a device body of the IMD. The device body includes a proximal body portion and a distal body portion. The distal body portion is configured to rotate relative to the proximal body portion to alter the extension length defined by the leadlet.

In an example, an implantable medical device configured to deliver pacing therapy, the implantable medical device including a device body configured to position within a heart, where the device body comprises a proximal body portion and a distal body portion and defines a longitudinal axis extending through the proximal body portion and the distal body portion, the proximal body portion is configured to rotate around the longitudinal axis relative to distal body portion, and a leadlet mechanically coupled to the device body, where the leadlet mechanically supports an electrode configured to deliver pacing therapy, and where in response to the proximal body portion rotating relative to the distal body portion, the device body is configured to alter an extension length of the leadlet.

In another example, an implantable medical device configured to deliver pacing therapy including a device body configured to position within a heart, wherein the device body comprises a proximal body portion and a distal body portion and defines a longitudinal axis extending through the proximal body portion and the distal body portion, and wherein the proximal body portion is configured to rotate around the longitudinal axis relative to distal body portion; a fixation mechanism attached to the distal body portion, wherein the fixation mechanism is configured to attach the implantable medical device to tissues of the heart; and a leadlet mechanically coupled to the device body, where the leadlet mechanically supports an electrode configured to deliver pacing therapy to a portion of a heart, in response to the proximal body portion rotating relative to the distal body portion, the device body is configured to alter an extension length of the leadlet, and the leadlet is configured to define a deployment configuration and a stowage configuration, where in the stowage configuration the leadlet is positioned within an outer boundary defined by the device body, and where the in the deployment configuration the leadlet is configured to extend over the extension length from the device body.

In another example, an exemplary, non claimed method comprises: rotating a proximal body portion of a device body around a longitudinal axis of the implantable device and relative to a distal portion of the device body, wherein the device body is configured to position within a heart and comprises an implantable medical device; and altering an extension length of a leadlet attached to the device body and extending from the device body using the rotation of the proximal body portion relative to the distal body portion, wherein the leadlet mechanically supports an electrode.

This disclosure describes an implantable medical device (IMD) configured to implant a leadlet electrode within tissue of a patient, such as a septal wall of the heart. The IMD is configured to position within a heart of a patient, such as within an atrium, ventricle, coronary sinus, or other portions of the heart. The IMD includes a leadlet supporting the leadlet electrode and configured to deploy from a device body of the IMD. The IMD includes a proximal body portion configured to rotate relative to a distal body portion to cause deployment and/or adjust an extension length of the leadlet.

In some examples, the leadlet is configured to penetrate tissues of the heart. The leadlet may be configured to position the leadlet electrode within the tissues when the leadlet penetrates the tissues of the heart. In some examples, the leadlet electrode is a non-penetrating electrode, and the leadlet is configured to position the leadlet in contact with or in the vicinity of the tissues. The leadlet may be configured to position a physiological sensor configured to sense a physiological parameter of the patient (e.g., a blood pressure, a blood oxygen level, or another physiological parameter). The IMD may include a fixation mechanism configured to engage tissues of the heart to substantially affix the distal body portion to a target site within the heart. The IMD may be configured such that affixing the distal body portion to the target site substantially secures the distal body portion relative to the tissues, such that the proximal body portion may be rotated relative to the distal body portion (e.g., by a clinician) to cause the leadlet to extend from the device body to position the leadlet electrode.

The IMD is configured to alter an extension length of the leadlet when the proximal body portion rotates relative to the distal body portion such that, for example, a clinician may alter the extension length by causing rotation of the proximal body portion. In examples, the IMD is configured such that rotation of the proximal body portion relative to the distal body portion in a first rotational direction causes the leadlet to extend in a direction away from the device body. In examples, the IMD is configured such that rotation of the proximal body portion relative to the distal body portion in a second rotational direction (e.g., opposite the first rotational direction) causes the leadlet to retract in a direction toward the device body. The leadlet may be configured such that extension and/or retraction of the leadlet alters a displacement between the leadlet electrode and the device body. Hence, when the distal body portion is anchored to tissue (e.g., by the fixation mechanism) a clinician may cause a rotation of the proximal body portion to extend and/or retract the leadlet to position the leadlet electrode within tissues at a position from the device body.

The IMD may be configured for delivery and/or retrieval through vasculature of the patient for implantation within an atrium, ventricle, coronary sinus, or other portion of the heart. The IMD may be configured to be implanted and contained entirely within the body or boundary of the heart in contrast to traditional lead-based pacing devices which are implanted within the pectoral region of the patient with leads extending into the heart. The IMD may include a housing defining a volume configured to mechanically support circuitry. The circuitry may be configured to deliver therapy (e.g., pacing) to and/or sense signals from the heart using the leadlet electrode. In examples, the leadlet includes a conductor electrically connecting the leadlet electrode and circuitry. The leadlet may support any number of electrodes arranged in any configuration. In examples, the device body defines a return electrode electrically connected to the circuitry and the circuitry is configured to deliver therapy to and/or sense signals from the heart using the return electrode. In some examples, the distal body portion mechanically supports a second electrode (e.g., an atrial electrode), and the circuitry is configured to deliver therapy to and/or sense signals from the heart using the second electrode.

In examples, the device body defines an outer profile and the leadlet is configured to stow within the bounds of the outer profile until a rotation of the distal body portion causes the leadlet to extend from the device body. In some examples, the IMD is configured such that rotation of the proximal body portion relative to the distal body portion causes the extended leadlet to substantially retract back to within the outer profile defined by the device body from a deployment configuration. Hence, the IMD is configured such that the leadlet may be deployed from and/or returned to a stowage configuration wherein the leadlet is substantially within the outer profile of the device body. Establishing the leadlet in the stowage configuration may ease the delivery and/or retrieval of the IMD (e.g., by a clinician) through vasculature of the patient.

In examples, the device body defines a longitudinal axis and the proximal body portion is configured to rotate relative to the distal body portion around the longitudinal axis. The leadlet may be configured to at least partially coil around the longitudinal axis when the leadlet is in the stowage configuration. Rotation of the distal body portion relative to the proximal body portion (e.g., in a first rotational direction) may cause the leadlet to substantially spool out from the stowage condition to extend away from the device body. Rotation of the distal body portion relative to the proximal body portion (e.g., in a second rotational direction opposite the first rotational direction) may cause the extended leadlet to retract into the device body and substantially wind into the coiled configuration.

The leadlet may define an extension length between a distal end of the leadlet ("leadlet distal end") and the device body. In examples, the device body defines a leadlet access configured to allow the leadlet to pass therethrough, and the extension length is a length of the leadlet between the leadlet access and the leadlet distal end. In some examples, the extension length is a displacement between the leadlet distal end and a fixed point on the device body. The IMD may be configured such that rotation of the proximal body portion relative to the distal body portion alters the extension length. In examples, the IMD is configured to impart a first force in a first direction to the leadlet to increase the extension length. In examples, the IMD is configured to impart a second force in a second direction opposite the first direction to decrease the extension length. In some examples, a proximal end of the leadlet ("leadlet proximal end") is secured to the device body, and the device body is configured to impart the first force and/or the second force on the leadlet proximal end when the proximal body portion rotates relative to the distal body portion.

The IMD may be configured to cause the leadlet to extend from the device body in any direction relative to the longitudinal axis defined by the device body. In some examples, the IMD is configured to cause the leadlet to extend in a particular direction relative to the longitudinal axis. For example, the IMD may be configured to cause the leadlet to extend in a direction substantially perpendicular to the longitudinal axis when the leadlet extends from the device body. The IMD may be configured to cause the leadlet to extend in a direction substantially parallel to the longitudinal axis when the leadlet extends from the device body. In some examples, the IMD (e.g., some portion of the distal body portion) is configured to insert into a coronary sinus of the heart and cause the leadlet to extend substantially perpendicular to the longitudinal axis to implant the leadlet electrode within a ventricular wall when the IMD is inserted in the coronary sinus. In some examples, the IMD is configured to affix to a septum of the heart (e.g., an atrial and/or ventricular septum) and cause the leadlet to extend substantially parallel to the longitudinal axis to implant the leadlet electrode within the septum. The leadlet may include a shape-memory material (e.g., a shape-memory polymer, a shape memory alloy such as Nitinol, or some other shape memory material) which tends to cause the leadlet to extend in the particular direction relative to the longitudinal axis. In some examples, a location of the leadlet access on the device body may tend to cause the leadlet to extend in the particular direction.

The IMD is configured to transit through vasculature of the patient to position the IMD in the vicinity of a target area, such as an area within a chamber of the heart. For example, the IMD may be configured to allow a clinician to navigate the IMD through a vein of the heart (e.g., an innominate vein, an interior vena cava (IVC), a superior vena cava (SVC), or another venous pathway) to a target location within a right ventricle (RV), right atrium (RA), or another area of the heart. In examples, the IMD is configured to position with a lumen of a delivery catheter configured to transit the IMD through vasculature. For example, the delivery catheter may include a cup section at a distal end of the catheter configured to substantially hold the IMD as the delivery catheter transits through vasculature. The IMD may be configured to fit within a lumen defined by the cup section when the leadlet is in the stowage configuration (e.g., when the leadlet is stowed within the bounds of the outer profile defined by the device body).

<FIG> is a conceptual diagram illustrating a portion of an example medical system <NUM> configured to deliver therapy (e.g., pacing) to a heart <NUM> of a patient. Medical system <NUM> includes IMD <NUM> including device body <NUM> and leadlet <NUM> extending from device body <NUM>. Medical system <NUM> includes a delivery catheter <NUM> configured to position IMD <NUM> within the vicinity of a target site <NUM> within heart <NUM>. In examples, as illustrated in <FIG>, target site <NUM> is a region in a ventricular wall of the right ventricle (RV) of heart <NUM>. In other examples, delivery catheter <NUM> and/or IMD <NUM> may be configured to position in the vicinity of a target site at another portion of heart <NUM>. For example, delivery catheter <NUM> and/or IMD <NUM> implantable medical lead may be configured to position in the vicinity of a target site in the right atrium (RA) of heart <NUM>, the left atrium (not shown), the left ventricle (not shown), or within or around the coronary sinus <NUM>. Delivery catheter <NUM> and IMD <NUM> may be configured to extend through vasculature of a patient (e.g., an interior vena cava (IVC)) to position IMD <NUM> within heart <NUM>. In examples, delivery catheter <NUM> includes a cup section (not shown) defining a lumen configured to engage IMD <NUM>.

IMD <NUM> may include a fixation mechanism <NUM> configured to secure IMD <NUM> to tissues of heart <NUM> such that IMD <NUM> is contained within the body or perimeter of the heart. In examples, device body <NUM> mechanically supports fixation mechanism <NUM>. Fixation mechanism <NUM> is configured to penetrate tissue of heart <NUM> at or near a target site, such as target site <NUM>. For example, fixation mechanism <NUM> may be configured to penetrate cardiac tissue of a septal wall in a RV, RA, LV, and/or LA of heart <NUM>, or penetrate cardiac tissue in another area of heart <NUM>. Fixation mechanism <NUM> may be configured to substantially maintain IMD <NUM> at or in the vicinity of the target site when fixation mechanism <NUM> penetrates tissues at or in the vicinity of the target site.

Fixation mechanism <NUM> may be configured to allow a clinician to cause fixation mechanism <NUM> to engage the tissue within heart <NUM>, such that the clinician may affix IMD <NUM> once delivered to the target site. For example, fixation mechanism <NUM> may include one or more tines configured to position within the cup section of delivery catheter <NUM> when IMD <NUM> is positioned within the cup section, with the one or more tines resiliently biased to deploy outward to grasp tissue when delivery catheter <NUM> is proximally withdrawn (e.g., by the clinician). In some examples, fixation mechanism <NUM> may include a helical element, a barbed element, screws, rings, and/or other structures configured to resist a translation (e.g., a proximal translation) of device body <NUM> away from a tissue wall when fixation mechanism <NUM> is engaged with the tissue wall. Hence, medical system <NUM> may be configured such that a clinician may guide IMD <NUM> to the vicinity of a target site such as target site <NUM> using delivery catheter <NUM>, then cause fixation mechanism <NUM> to substantially maintain IMD <NUM> at or in the vicinity of the target site.

IMD <NUM> may be configured such that, when attached to tissues of heart <NUM> by fixation mechanism <NUM>, leadlet <NUM> may be deployed from device body <NUM> to penetrate tissues of heart <NUM>. Leadlet <NUM> may be configured to deploy from device body <NUM> to penetrate tissues in the vicinity of a target site such as target site <NUM>. Leadlet <NUM> mechanically supports a leadlet electrode <NUM>. In examples, leadlet <NUM> may be configured to deploy from device body <NUM> to position leadlet electrode <NUM> within tissues of heart <NUM> and substantially displaced from device body <NUM>. IMD <NUM> is configured to alter a length of leadlet <NUM> which extends from device body <NUM> such that, for example, leadlet <NUM> may establish and/or alter the position of leadlet electrode <NUM> within the tissue of heart <NUM>. In examples, device body <NUM> is configured to mechanically support circuitry <NUM> configured to deliver therapy (e.g., pacing) to and/or sense signals from heart <NUM> using leadlet electrode <NUM>. Leadlet <NUM> may include a conductor (not shown) electrically connecting leadlet electrode <NUM> and circuitry <NUM>.

Device body <NUM> includes a proximal body portion <NUM> and a distal body portion <NUM>. Proximal body portion <NUM> is configured to rotate relative to distal body portion <NUM> around a longitudinal axis L defined by device body <NUM>. IMD <NUM> is configured to alter an extension length of leadlet <NUM> when proximal body portion <NUM> rotates relative to distal body portion <NUM>. For example, IMD <NUM> may be configured to cause an extension of leadlet <NUM> in a direction substantially away from device body <NUM> when proximal body portion <NUM> rotates relative to distal body portion <NUM>. In examples, IMD <NUM> is configured to cause a retraction of leadlet <NUM> in a direction substantially toward device body <NUM> when proximal body portion <NUM> rotates relative to distal body portion <NUM>. Distal body portion <NUM> may mechanically support fixation mechanism <NUM> and be configured to remain rotationally stationary with respect to fixation mechanism <NUM>. Hence, IMD <NUM> may be configured such that, when fixation mechanism <NUM> engages tissues of heart <NUM> and a torque around longitudinal axis L is exerted on proximal body portion <NUM> (e.g., by delivery catheter <NUM> or another device), the torque causes proximal body portion <NUM> to rotate relative to distal body portion <NUM> such that leadlet <NUM> extends or retracts.

Leadlet <NUM> may be configured such that extension and/or retraction of leadlet <NUM> alters a displacement between leadlet electrode <NUM> and device body <NUM>. Hence, when distal body portion <NUM> is anchored to tissue by fixation mechanism <NUM>, a clinician may cause a torque around longitudinal axis L to be exerted on proximal body portion <NUM> extend and/or retract leadlet <NUM> to position leadlet electrode <NUM> within tissues of heart <NUM>. In examples, leadlet electrode <NUM> is configured to substantially implant within tissues of heart <NUM> to conduct electrical signals from circuitry <NUM> to the target tissue of heart <NUM>, such that the electrical signals cause the cardiac muscle, e.g., of the ventricles, to depolarize and, in turn, contract at a regular interval.

IMD <NUM> may be configured to cause leadlet <NUM> to extend from device body <NUM> in any direction relative to longitudinal axis L when proximal body portion <NUM> rotates relative to distal body portion <NUM>. In examples, as illustrated in <FIG>, IMD <NUM> is configured to cause leadlet <NUM> to extend from device body <NUM> in a direction substantially parallel to longitudinal axis L when proximal body portion <NUM> rotates relative to distal body portion <NUM>. In other examples, IMD <NUM> is configured to cause leadlet <NUM> to extend from device body <NUM> in a direction substantially perpendicular to longitudinal axis L when proximal body portion <NUM> rotates relative to distal body portion <NUM>. In some examples, IMD <NUM> is configured such that some portion of device body <NUM> (e.g., fixation mechanism <NUM> and distal body portion <NUM>) inserts within coronary sinus <NUM> and leadlet <NUM> deploys substantially perpendicular to longitudinal axis L to penetrate tissues defining a wall of coronary sinus <NUM>.

Hence, medical system <NUM> may be configured to position IMD <NUM> at or in the vicinity of a target site using delivery catheter <NUM>. Fixation mechanism <NUM> may be caused (e.g., by a clinician) to substantially affix distal body portion <NUM> to the target site, such that distal body portion <NUM> remains substantially stationary with respect to tissues at the target site. Leadlet <NUM> may be deployed from device body <NUM> to position leadlet electrode <NUM> within tissues of heart <NUM>. In examples, leadlet <NUM> is deployed by causing (e.g., by a clinician) a rotation of proximal body portion <NUM> relative to distal body portion <NUM>. In examples, leadlet <NUM> may be deployed by exerting a force on leadlet <NUM> using, for example, a stylet. IMD <NUM> is configured such that rotation of proximal body portion <NUM> relative to distal body portion <NUM> causes leadlet <NUM> to extend and/or retract relative to device body <NUM>.

<FIG> illustrate medical system <NUM> including a perspective view of an example IMD <NUM>. <FIG> illustrates IMD <NUM> with leadlet <NUM> is a stowed configuration, such that leadlet <NUM> is positioned within an outer boundary B defined by device body <NUM>. <FIG> illustrates IMD <NUM> leadlet <NUM> in a deployed configuration, with proximal body portion <NUM> having rotated around longitudinal axis L to cause leadlet <NUM> to extend over an extension length LE away from device body <NUM>. <FIG> illustrates an exploded view of IMD <NUM>, illustrating distal body portion <NUM> separated from proximal body portion <NUM> and leadlet <NUM> positioned to stow within a stowage volume defined by proximal body portion <NUM> and distal body portion <NUM>.

As illustrated in <FIG>, device body <NUM> defines a longitudinal axis L extending through proximal body portion <NUM> and distal body portion <NUM>. Proximal body portion <NUM> is configured to rotate around longitudinal axis L relative to distal body portion <NUM>. In examples, proximal body portion <NUM> is configured to rotate around longitudinal axis L relative to distal body portion <NUM> in a first rotational direction W1 and/or a second rotational direction W2 opposite the first rotational direction W1. It is understood that, when proximal body portion <NUM> rotates relative to distal body portion <NUM> as described herein, this may result from a rotation of proximal body portion <NUM> around longitudinal axis L as distal body portion <NUM> remains substantially stationary, or a rotation of distal body portion <NUM> around longitudinal axis L as proximal body portion <NUM> remains substantially stationary, or a rotation of both proximal body portion <NUM> and distal body portion <NUM> around longitudinal axis L at differing directions and/or speeds of rotation.

IMD <NUM> is configured such that proximal body portion <NUM> may rotate relative to distal body portion <NUM> to alter the extension length LE of leadlet <NUM>. IMD <NUM> may be configured such that a rotation of proximal body portion <NUM> relative to distal body portion causes an increase and/or decrease in the extension length LE. In examples, IMD <NUM> is configured such that when distal body portion <NUM> is anchored to tissue by fixation mechanism <NUM>, a clinician may cause a torque around longitudinal axis L to be exerted on proximal body portion <NUM> extend and/or retract leadlet <NUM>. In examples, IMD <NUM> includes and/or defines a rotary joint <NUM> (<FIG>) configured to operably connect to proximal body portion <NUM> and distal body portion <NUM> to allow proximal body portion <NUM> to rotate relative to distal body portion <NUM>. Rotary joint <NUM> may be configured to limit a linear displacement parallel to longitudinal axis L between proximal body portion <NUM> and distal body portion <NUM> while allowing the rotation. In examples, rotary joint <NUM> is configured such that when one of distal body portion <NUM> or proximal body portion <NUM> exerts a force parallel to longitudinal axis L on the other of distal body portion <NUM> or proximal body portion <NUM>, distal body portion <NUM> and proximal body portion <NUM> generate an action-reaction force pair substantially limiting and/or eliminating the linear displacement.

Leadlet <NUM> includes a leadlet body <NUM> defining a distal end <NUM> of leadlet body <NUM> ("leadlet distal end <NUM>"). Leadlet body <NUM> may be an elongated body defining a proximal end <NUM> of leadlet body <NUM> ("leadlet proximal end <NUM>" (<FIG>)) opposite leadlet distal end <NUM>. In examples, leadlet proximal end <NUM> is secured to device body <NUM> and leadlet distal end <NUM> is a substantially free end. In some examples, leadlet proximal end <NUM> is secured to proximal body portion <NUM>. Leadlet proximal end <NUM> may be configured to rotate around longitudinal axis L when proximal body portion <NUM> rotates around longitudinal axis L.

Leadlet <NUM> mechanically supports one or more electrodes such as leadlet electrode <NUM>. Leadlet <NUM> may support any number of electrodes arranged in any configuration. In examples, leadlet <NUM> mechanically supports leadlet electrode <NUM> substantially at leadlet distal end <NUM>. In some examples, leadlet <NUM> mechanically supports leadlet electrode <NUM> such that leadlet electrode <NUM> substantially defines leadlet distal end <NUM>. In examples, leadlet <NUM> includes a conductor (not shown) electrically connected to leadlet electrode <NUM>. The conductor may be configured to electrically connect leadlet electrode <NUM> with circuitry <NUM> (<FIG>) configured to deliver therapy (e.g., pacing) to and/or sense signals from heart <NUM> using leadlet electrode <NUM>.

In examples, device body <NUM> defines a return electrode <NUM> electrically connected to circuitry <NUM>. Circuitry <NUM> may be configured to deliver therapy to and/or sense signals from heart <NUM> using return electrode <NUM>. In some examples, device body <NUM> (e.g., proximal body portion <NUM> or distal body portion <NUM>) mechanically supports a second electrode <NUM> (e.g., an atrial electrode), and circuitry <NUM> is configured to deliver therapy to and/or sense signals from heart <NUM> using second electrode <NUM>. Second electrode <NUM> may be configured to contact and/or penetrate tissues of heart <NUM> when fixation mechanism <NUM> engages tissues of heart <NUM>. In some examples, IMD <NUM> includes a stem member <NUM> extending from device body <NUM> defining a displacement between second electrode <NUM> and distal body portion <NUM>. In some examples, second electrode <NUM> may be a button electrode configured to contact tissues of heart <NUM> when device body <NUM> (e.g., distal body portion <NUM>) contacts tissues of heart <NUM>. Circuitry <NUM> may be configured to deliver therapy (e.g., pacing) to and/or sense signals from heart <NUM> using any of leadlet electrode <NUM>, second electrode <NUM>, and/or return electrode <NUM>.

Leadlet <NUM> is configured to extend from device body <NUM> to define the extension length LE. In examples, extension length LE is a displacement between leadlet distal end <NUM> and device body <NUM>. In some examples, device body <NUM> defines a leadlet access <NUM> configured to allow leadlet <NUM> to pass therethrough, and extension length LE is a length of leadlet <NUM> between leadlet access <NUM> and leadlet distal end <NUM>. In some examples, extension length LE is a displacement between leadlet distal end <NUM> and a fixed point P on device body <NUM> (e.g., on distal body portion <NUM>). IMD <NUM> is configured to alter (e.g., increase and/or decrease) the extension length LE of leadlet <NUM> when proximal body portion <NUM> rotates relative to distal body portion <NUM>. Hence, IMD <NUM> is configured such that clinician may cause a rotation of proximal body portion <NUM> (e.g., using delivery catheter <NUM> (<FIG>)) relative to distal body portion <NUM> to cause an alteration of the extension length LE such that, for example, leadlet <NUM> alters a position of leadlet electrode <NUM>.

In examples, IMD <NUM> is configured to exert a force on leadlet <NUM> to cause leadlet <NUM> to alter the extension length LE when proximal body portion <NUM> rotates relative to distal body portion <NUM>. For example, leadlet proximal end <NUM> may be secured to proximal body portion <NUM> such that leadlet proximal end <NUM> rotates around longitudinal axis L when proximal body portion <NUM> rotates around longitudinal axis L. Proximal body portion <NUM> may exert a torque on leadlet proximal end <NUM> (e.g., in the first rotational direction W1 and/or the second rotational direction W2) causing leadlet proximal end <NUM> to receive the force from proximal body portion <NUM> and transmit the force along leadlet body <NUM>. The force received by leadlet proximal end <NUM> and transmitted along leadlet body may cause leadlet body <NUM> to translate (e.g., through leadlet access <NUM>) to increase and/or decrease the extension length LE. In examples, IMD <NUM> is configured to impart a force in a first direction D1 on leadlet <NUM> to increase the extension length LE when proximal body portion <NUM> rotates in the first rotational direction W1 relative to distal body portion <NUM>. In examples, IMD <NUM> is configured to impart a force in a second direction D2 on leadlet <NUM> to decrease the extension length LE when proximal body portion <NUM> rotates in the second rotational direction W2 relative to distal body portion <NUM>.

In examples, instead of or in addition to transferring a torque to leadlet proximal end <NUM>, proximal body portion <NUM> may be configured to mechanically engage leadlet body <NUM> to transfer a force to leadlet <NUM> as proximal body portion <NUM> rotates relative to distal body portion <NUM>, such that the force causes leadlet <NUM> to translate to alter the extension length LE. Proximal body portion <NUM> may include an engaging structure <NUM> (<FIG>) configured to rotate when proximal body portion <NUM> rotates. Engaging structure <NUM> may be configured to contact leadlet body <NUM> and generate a frictional force on leadlet body <NUM> when engaging structure <NUM> rotates with proximal body portion <NUM>. Engaging structure <NUM> and/or leadlet body <NUM> may be configured such the frictional force imparts a force on leadlet body <NUM>, causing movement of leadlet <NUM>.

IMD <NUM> may be configured such that the extension length LE of leadlet <NUM> may be increased without a relative rotation between proximal body portion <NUM> and distal body portion <NUM>. For example, leadlet <NUM> (e.g., leadlet body <NUM>, leadlet distal end <NUM>, leadlet electrode <NUM>, and/or another portion of leadlet <NUM>) may include a bearing structure <NUM> (<FIG>) configured to receive an elongated body such as a stylet. Bearing structure <NUM> may be configured to receive a force (e.g., in the direction D1 and/or D2) and transfer the force to leadlet <NUM> to cause a translation of leadlet <NUM> relative to device body <NUM>. In examples, IMD <NUM> is configured such that leadlet <NUM> may translate in at least one direction (e.g., in the direction D1 or D2) when proximal body portion <NUM> is substantially rotationally stationary with respect to distal body portion <NUM>. For example, IMD <NUM> may be configured to allow leadlet <NUM> to translate in the first direction D1 when proximal body portion <NUM> is substantially rotationally stationary with respect to distal body portion <NUM>, such that, for example, a clinician may extend leadlet <NUM> by using the elongated body to exert a force on bearing structure <NUM> as proximal body portion <NUM> remains rotationally stationary with respect to distal body portion <NUM>. In other examples, IMD <NUM> may be configured such that a force exerted on bearing structure <NUM> to increase or decrease the extension length LE causes and/or results in rotation of proximal body portion <NUM> relative to distal body portion <NUM>. Hence, IMD <NUM> may be configured such that a clinician may exert a force on bearing structure <NUM> to cause leadlet <NUM> to position leadlet electrode <NUM> at a desired location within the tissue of heart <NUM>.

In some examples, leadlet body <NUM> is configured to receive a force from proximal body portion <NUM> and transfer the force to leadlet distal end <NUM> to cause leadlet distal end <NUM> to penetrate tissues of heart <NUM>. Leadlet body <NUM> may be configured to remain substantially stiff as leadlet body <NUM> transfers the force to leadlet distal end <NUM>, such that the penetration of tissue by leadlet distal end <NUM> may substantially be caused by a rotation of proximal body portion <NUM> relative to distal body portion <NUM>. For example, IMD <NUM> may be configured such that, when fixation mechanism <NUM> secures distal body portion <NUM> to tissue in a target site and proximal body portion <NUM> rotates around longitudinal axis L, the rotation of proximal body portion <NUM> imparts a force to leadlet body <NUM> increasing the extension length LE of leadlet <NUM> and causing leadlet distal end <NUM> to contact tissues in the target site. Leadlet body <NUM> may have a stiffness such that leadlet body <NUM> transfers force to leadlet distal end <NUM> sufficient to cause leadlet distal end <NUM> to penetrate the tissues in the target site as rotation of proximal body portion <NUM> continues. Hence, IMD <NUM> may be configured such that a clinician may position leadlet electrode <NUM> at a desired location within heart <NUM> using a rotation of proximal body portion <NUM> relative to distal body portion <NUM>. In examples, leadlet distal end <NUM> defines a shape configured to facilitate penetration into the tissue such as, for example, a substantially sharp shape, a shape defining an substantially pointed apex, or some other shape configured to facilitate penetration when leadlet body <NUM> transfers a force to leadlet distal end <NUM>.

As discussed, although depicted in <FIG> as extending substantially perpendicular to longitudinal axis L. IMD <NUM> may be configured to cause leadlet <NUM> to extend in any direction relative to longitudinal axis L in other examples. In some examples, IMD <NUM> includes a directing structure <NUM> (<FIG>) configured to cause leadlet <NUM> to extend in a particular direction relative to longitudinal axis L when proximal body portion <NUM> rotates relative to distal body portion <NUM> to impart a force on leadlet proximal end <NUM>. In examples, as illustrated in <FIG>, proximal body portion <NUM> defines at least some portion of directing structure <NUM>. In other examples, distal body portion <NUM> defines at least some portion of directing structure <NUM>. Directing structure <NUM> may be a platform and/or ramp configured to direct leadlet <NUM> (e.g., leadlet body <NUM>) in a specific direction relative to longitudinal axis L when device body <NUM> imparts a force on leadlet proximal end <NUM>. Directing structure <NUM> may be configured to substantially direct leadlet distal end <NUM> through leadlet access <NUM> to cause leadlet <NUM> to extend in a direction away from device body <NUM> when proximal body portion <NUM> rotates relative to distal body portion <NUM>.

In some examples, leadlet body <NUM> includes a shape-memory material biased to extend in a certain direction relative to longitudinal axis L when leadlet <NUM> extends away from device body <NUM>. Leadlet body <NUM> may be configured such that, when a section of leadlet body is in a substantially relaxed condition (e.g., free of external forces imparted by device body <NUM>), the resilient biasing of the shape memory material tends to cause leadlet body <NUM> to extend in the specific direction. The shape memory material may be resiliently biased such that leadlet body <NUM> tends to extend in a specific direction substantially perpendicular to longitudinal axis L, in a specific direction substantially parallel to longitudinal axis L, or in any other specific direction relative to longitudinal axis L.

Leadlet access <NUM> may be defined anywhere on device body <NUM>, and may be configured to allow an extension of leadlet <NUM> in any direction relative to longitudinal axis L. In examples leadlet access <NUM> is defined by distal body portion <NUM>. Leadlet access <NUM> may be configured to allow passage of leadlet distal end <NUM> and/or leadlet body <NUM> therethrough when directing structure <NUM> directs leadlet distal end <NUM> and/or leadlet body <NUM> in a specific direction relative to longitudinal axis L. In examples, leadlet access <NUM> is configured such that leadlet <NUM> translates over a path between directing structure <NUM> and leadlet access <NUM> when leadlet proximal end <NUM> receives force from device body <NUM> (e.g., proximal body portion <NUM>).

In examples, device body <NUM> defines an axial portion <NUM> (<FIG>) extending from proximal body portion <NUM> and configured to allow proximal body portion <NUM> to rotate relative to distal body portion <NUM>. Axial portion <NUM> may be configured to rotate when proximal body portion <NUM> rotates. In examples, axial portion <NUM> is configured to rotate within an inner perimeter defined by the distal body portion <NUM>. IMD <NUM> may be configured such that longitudinal axis L intersects axial portion <NUM>. Axial portion <NUM> may be configured to rotate around longitudinal axis L when proximal body portion <NUM> rotates around longitudinal axis L. In examples, axial portion <NUM> defines at least some portion of rotary joint <NUM>. Distal body portion <NUM> may be configured to at least partially surround axial portion <NUM> when rotary joint <NUM> operably couples distal body portion <NUM> and proximal body portion <NUM>. In examples, distal body portion <NUM> is configured to substantially cover axial portion <NUM> when rotary joint <NUM> operably couples distal body portion <NUM> and proximal body portion <NUM>. In some examples, distal body portion <NUM> defines a base surface <NUM> ("distal portion base surface <NUM>) and proximal body portion <NUM> defines a base surface <NUM> ("proximal portion base surface <NUM>), and distal portion base surface <NUM> is configured to substantially face proximal portion base surface <NUM> when distal body portion <NUM> at least partially surround axial portion <NUM>. Distal portion base surface <NUM> may be configured to substantially face proximal portion base surface <NUM> when rotary joint <NUM> operable couples distal body portion <NUM> and proximal body portion <NUM>. In some examples, distal portion base surface <NUM> and distal portion base surface <NUM> are configured to define substantially parallel surfaces when distal body portion <NUM> at least partially surround axial portion <NUM> and/or rotary joint <NUM> operable couples distal body portion <NUM> and proximal body portion <NUM>.

In examples, IMD <NUM> is configured to substantially maintain leadlet <NUM> in a stowage configuration. IMD <NUM> may be configured to substantially maintain leadlet <NUM> in the stowage configuration until proximal body portion <NUM> is caused to rotate (e.g., by a clinician) relative to distal body portion <NUM>. Leadlet <NUM> and /or device body <NUM> may be configured such that leadlet <NUM> is positioned within the outer boundary B defined by device body <NUM> when leadlet <NUM> is in the stowage configuration. IMD <NUM> may be configured such that rotation of proximal body portion <NUM> relative to distal body portion <NUM> (e.g., in the first rotational direction W1) causes leadlet <NUM> (e.g., leadlet distal end <NUM>) to pass through and/or cross the outer boundary B and increase the extension length LE (e.g., by passing through leadlet access <NUM>). IMD <NUM> may be configured such that rotation of proximal body portion <NUM> relative to distal body portion <NUM> (e.g., in the second rotational direction) causes leadlet <NUM> (e.g., leadlet distal end <NUM>) to substantially retract back to within the outer boundary B (e.g., by passing through leadlet access <NUM>). Hence, IMD <NUM> may be configured such that leadlet <NUM> may be extended beyond the outer boundary B from a stowage configuration, and subsequently retracted back within the outer boundary B to substantially re-establish the stowage configuration. Thus, leadlet <NUM> may be substantially maintained in the stowage configuration during delivery of IMD <NUM> through vasculature to heart <NUM>, deployed from the stowage condition to position leadlet electrode <NUM> within tissues of heart <NUM>, and/or re-established in the stowage configuration in the event IMD <NUM> is retrieved through vasculature from heart <NUM>.

In examples, device body <NUM> defines a leadlet stowage space <NUM> configured to substantially surround leadlet <NUM> when leadlet <NUM> is in the stowage configuration. Leadlet stowage space <NUM> may be volume defined within the outer boundary B of device body <NUM>. Leadlet access <NUM> may be an opening to leadlet stowage space <NUM>. In examples, IMD <NUM> is configured such that a rotation of proximal body portion <NUM> relative to distal body portion <NUM> (e.g., in the first rotational direction W1) causes leadlet distal end <NUM> to emerge from leadlet stowage space <NUM> via leadlet access <NUM>. IMD <NUM> may be configured such that a rotation of proximal body portion <NUM> relative to distal body portion <NUM> (e.g., in the second rotational direction W2) causes leadlet distal end <NUM> to displace from a position outside of outer boundary B to a position within leadlet stowage space <NUM> via leadlet access <NUM>.

Device body <NUM> may be configured to define leadlet stowage space <NUM> between proximal body portion <NUM> and distal body portion <NUM>. In examples, device body <NUM> is configured to define leadlet stowage space <NUM> between axial portion <NUM> and distal body portion <NUM> when distal body portion <NUM> at least partially surrounds axial portion <NUM>. In some examples, leadlet <NUM> is configured to substantially coil around longitudinal axis L (<FIG>) when leadlet <NUM> is positioned within leadlet stowage space <NUM>. Leadlet <NUM> may be configured to substantially coil around axial portion <NUM> when leadlet <NUM> is positioned within leadlet stowage space <NUM>. IMD <NUM> may be configured such that rotation of proximal body portion <NUM> relative to distal body portion <NUM> (e.g., in the first rotational direction W1) causes leadlet <NUM> to substantially spool out of leadlet stowage space <NUM> through leadlet access <NUM> when leadlet <NUM> is substantially coiled around longitudinal axis L. IMD <NUM> may be configured such that rotation of proximal body portion <NUM> relative to distal body portion <NUM> (e.g., in the second rotational direction W2) causes leadlet <NUM> to retract toward device body <NUM> and substantially coil around longitudinal axis L within leadlet stowage space <NUM>.

Fixation mechanism <NUM> is configured to engage tissue at a target site (e.g., target site <NUM> (<FIG>)) to secure IMD <NUM> to the tissue. Fixation mechanism <NUM> may be configured to substantially secure distal body portion <NUM> in a position relative to the tissues at the target site, such that a torque applied to proximal body portion <NUM> causes proximal body portion <NUM> to rotate around longitudinal axis L relative to distal body portion <NUM>. In examples, fixation mechanism <NUM> is configured to be rotationally stationary with respect to distal body portion <NUM>. Fixation mechanism <NUM> may include, for example, one or more elongated tines such as fixation tine <NUM> configured to substantially maintain an orientation of distal body portion <NUM> with respect to a target site (e.g., target site <NUM>). Fixation mechanism <NUM> may include fixation tines of any shape, including helically-shaped fixation tines. In examples, fixation mechanism <NUM> is configured to substantially maintain contact between second electrode <NUM> and tissues within a target site when fixation mechanism <NUM> engages the tissue. Fixation mechanism <NUM> may be configured to position within the cup section of delivery catheter <NUM> (<FIG>) when IMD <NUM> is positioned within the cup section, with one or more tines such as tine <NUM> resiliently biased to deploy outward to grasp tissue when delivery catheter <NUM> is proximally withdrawn (e.g., by the clinician).

As an example, <FIG> illustrates an example IMD <NUM> positioned within a cup section <NUM> of a delivery catheter <NUM>. <FIG> illustrates IMD <NUM> with delivery catheter <NUM> and cup section <NUM> proximally displaced from IMD <NUM>. Delivery catheter <NUM> is illustrated as a cross-section with a cutting plane parallel to the page. Delivery catheter <NUM> is an example of delivery catheter <NUM>. IMD <NUM> is an example of IMD <NUM>. IMD <NUM> further includes device body <NUM>, proximal body portion <NUM>, distal body portion <NUM>, second electrode <NUM>, return electrode <NUM>, fixation mechanism <NUM> with fixation tine <NUM>, and leadlet access <NUM>, which may be configured individually and in relation to each other in the same manner as that described for like-named components of IMD <NUM>.

Cup section <NUM> may define a lumen <NUM> configured to at least circumferentially surround IMD <NUM>, such that delivery catheter <NUM> may deliver IMD <NUM> to heart <NUM> (<FIG>). In examples, cup section <NUM> includes an inner wall <NUM> defining lumen <NUM>. Cup section <NUM> may define a lumen opening <NUM> opening to lumen <NUM> at a distal end <NUM> of cup section <NUM> ("cup distal end <NUM>") configured such that fixation mechanism <NUM> and device body <NUM> may pass therethrough. Fixation mechanism <NUM> may be configured to engage tissue (e.g., within target site <NUM> (<FIG>)) as fixation mechanism <NUM> passes through lumen opening <NUM>. In examples, fixation mechanism <NUM> (e.g., fixation tine <NUM>) is configured to extend distally from distal body portion <NUM> when IMD <NUM> is positioned within cup section <NUM>. Fixation mechanism <NUM> may be configured to penetrate tissues as fixation mechanism <NUM> passes through lumen opening <NUM> in order to engage the tissues. For example, a portion of fixation mechanism <NUM> (e.g., fixation tine <NUM>) may be resiliently biased to expand outward as fixation mechanism <NUM> passes through lumen opening <NUM>, in order to aid in grasping the tissue. Cup section <NUM> may be configured to radially constrain fixation mechanism <NUM> (e.g., fixation tine <NUM>) when fixation mechanism <NUM> is proximal to lumen opening <NUM>.

In examples, fixation tine <NUM> includes a fixed end <NUM> mechanically supported by distal body portion <NUM> and a free end <NUM> opposite fixed end <NUM>. In examples, free end <NUM> is configured to penetrate tissue. Fixation tine <NUM> may be biased so that at least some portion of fixation tine <NUM> expands radially as fixation tine <NUM> passes through lumen opening <NUM>. Fixation tine <NUM> may be biased to drive free end <NUM> radially outward from longitudinal axis L of IMD <NUM> as free end <NUM> passes through lumen opening <NUM>, as illustrated in <FIG>. The biasing tending to drive free end <NUM> radially outward as fixation tine <NUM> extends through lumen opening <NUM> may cause fixation tine <NUM> to substantially grasp tissue and more securely attach distal body portion <NUM> to tissues (e.g., within heart <NUM>). Free end <NUM> may pierce the tissue and may act to pull IMD <NUM> toward a target site as fixation tine <NUM> elastically bends or curves radially outward. Fixation mechanism <NUM> may include any number of fixation tines, which may be configured similarly to fixation tine <NUM>.

The biasing of fixation tine <NUM> tending to drive free end <NUM> radially outward may cause fixation tine <NUM> to assume any general shape. In some examples, the biasing of fixation tine <NUM> tends to cause fixation tine <NUM> to position such that free end <NUM> establishes a position distal to a midpoint M between fixed end <NUM> and free end <NUM> (e.g., as depicted in <FIG>). In some examples, the biasing of fixation tine <NUM> tends to cause fixation tine <NUM> to position such that free end <NUM> establishes a position proximal to midpoint M. Fixation tine <NUM> may be formed to have a preset shape and may be formed using any suitable material. In examples, fixation tine <NUM> comprises a nickel-titanium alloy such as Nitinol.

In some examples, fixation tine <NUM> may be configured to substantially maintain a delivery configuration where free end <NUM> is distal to fixed end <NUM> and distal to midpoint M (e.g., as depicted in <FIG>). For example, fixation tine <NUM> may be configured to substantially maintain the delivery configuration when free end <NUM> is constrained from outward radial motion by inner wall <NUM>. Cup section <NUM> may be configured to substantially maintain fixation tine <NUM> in the delivery configuration as delivery catheter <NUM> translates through vasculature to deliver IMD <NUM> to heart <NUM>. Substantially maintaining free end <NUM> distal to midpoint M (e.g., in the delivery configuration) may facilitate the penetration of tissue by free end <NUM> when fixation tine <NUM> passes through lumen opening <NUM> of delivery catheter <NUM>.

Fixation tine <NUM> may refer to any structure that is capable of securing a lead or leadless implantable medical device to a location within the heart. In some examples, a tine (e.g., fixation tine <NUM>) may be composed of a shape-memory allow that allows deformation along the length of the tine. A tine may be substantially flat along the length of the tine. In other examples, a tine may substantially define a helix and/or helical member.

In examples, IMD <NUM> is configured to receive a force imparted by a delivery tether <NUM>. Delivery tether <NUM> may be configured to impart a force to cause IMD <NUM> to translate in a proximal or distal direction. For example, delivery tether <NUM> may be configured to impart a force to cause IMD <NUM> to pass through lumen opening <NUM> to at least partially exit cup section <NUM>. In examples, delivery tether <NUM> is configured to impart a torque around longitudinal axis L to IMD <NUM> to cause some portion of IMD <NUM> (e.g., proximal body portion <NUM>) to rotate around longitudinal axis L. Delivery tether <NUM> may be configured to impart a torque proximal body portion <NUM> to cause proximal body portion <NUM> to rotate relative to distal body portion <NUM> (e.g., when fixation mechanism <NUM> engages tissue within, for example, target site <NUM> (<FIG>)). In examples, delivery tether <NUM> is configured to mechanically engage IMD <NUM> (e.g., proximal body portion <NUM>) to impart a force and/or torque to IMD <NUM>.

<FIG> illustrate an example IMD <NUM> configured to cause a leadlet <NUM> to extend from a device body <NUM> in a direction substantially parallel to longitudinal axis L. Device body <NUM> includes proximal body portion <NUM> and a distal body portion <NUM>, with distal body portion <NUM> shown as a transparent component for illustration. IMD <NUM>, leadlet <NUM>, device body <NUM>, proximal body portion <NUM>, and distal body portion <NUM> are examples of IMD <NUM>, <NUM>, leadlet <NUM>, <NUM>, device body <NUM>, <NUM>, proximal body portion <NUM>, <NUM>, and distal body portion <NUM>, <NUM> respectively. IMD <NUM> further includes leadlet electrode <NUM>, second electrode <NUM>, return electrode <NUM>, fixation mechanism <NUM> with fixation tine <NUM>, leadlet body <NUM>, leadlet distal end <NUM>, leadlet access <NUM>, directing structure <NUM>, and leadlet stowage space <NUM>, which may be configured individually and in relation to each other in the same manner as that described for like-named components of IMD <NUM> and/or IMD <NUM>.

<FIG> illustrates leadlet <NUM> in a stowage configuration within leadlet stowage space <NUM> defined between distal body portion <NUM> and proximal body portion <NUM>. <FIG> illustrates IMD <NUM> with proximal body portion <NUM> having rotated around longitudinal axis L to cause leadlet <NUM> to extend through leadlet access <NUM>. IMD <NUM> includes directing structure <NUM> configured to cause leadlet <NUM> to extend in a direction substantially parallel to longitudinal axis L when a force is exerted on leadlet body <NUM> (e.g., by proximal body portion <NUM>). <FIG> illustrates leadlet <NUM> extending in the direction substantially parallel to longitudinal axis L. Directing structure <NUM> may be defined by some portion of proximal body portion <NUM> and/or distal body portion <NUM>. Leadlet access <NUM> may be configured such that, when directing structure <NUM> causes leadlet <NUM> to extend in a direction substantially parallel to longitudinal axis L, leadlet <NUM> passes through leadlet access <NUM>.

In examples, distal body portion <NUM> includes a marker <NUM> ("distal marker <NUM>") and proximal body portion <NUM> includes a marker <NUM> ("proximal marker <NUM>"). Distal marker <NUM> may be configured to visually align with proximal marker <NUM> (as illustrated in <FIG>) when proximal body portion <NUM> establishes a particular rotational orientation with respect to distal body portion <NUM>. Distal marker <NUM> and proximal marker <NUM> may be configured such that a displacement between distal marker <NUM> and proximal marker <NUM> is indicative of a rotational position of proximal body portion <NUM> relative to distal body portion <NUM>. In examples, distal marker <NUM> and proximal marker <NUM> are configured such that a displacement between distal marker <NUM> and proximal marker <NUM> is indicative of the extension length of leadlet <NUM> (e.g., the extension length LE (<FIG>)). In some examples, distal marker <NUM> and proximal marker <NUM> are configured to align when proximal body portion <NUM> reaches a limit of rotation relative to distal body portion <NUM>. For example, distal marker <NUM> and proximal marker <NUM> may be configured to align when proximal body portion <NUM> reaches a rotational limit such that proximal body portion <NUM> is prevented from further rotation in the first rotational direction W1 (<FIG>) relative to distal body portion <NUM>. Distal marker <NUM> and proximal marker <NUM> may be configured to align when proximal body portion <NUM> reaches a rotational limit such that proximal body portion <NUM> is prevented from further rotation in the second rotational direction W2 (<FIG>) relative to distal body portion <NUM>. IMD <NUM> may include any number of distal markers and/or proximal markers, which may be configured to indicate any rotational orientation of proximal body portion <NUM> with respect to distal body portion <NUM>.

In examples, distal marker <NUM> and/or proximal marker <NUM> are configured to be visible on an imaging display of an imaging apparatus when IMD <NUM> is within a patient and imaged by the imaging apparatus. The imaging apparatus may be any type of imaging apparatus configured to image, or provide images of, IMD <NUM> within a patient. For example, the imaging apparatus may be configured to capture images of IMD <NUM> within a patient using one or more image modalities such as x-ray images, fluoroscopy, ultrasound, computed tomography (CT), magnetic resonance imaging (MRI), and/or others. Hence, distal marker <NUM> and/or proximal marker <NUM> may be configured such that clinician may view an image of distal marker <NUM> and/or proximal marker <NUM> on the imaging display to estimate the relative orientation of proximal body portion <NUM> with respect to distal body portion <NUM>.

As discussed, medical system <NUM> (e.g., IMD <NUM>, <NUM>, <NUM>, or another external device) may include circuitry <NUM> configured to deliver therapy to and/or sense cardiac signals from heart <NUM> (<FIG>) using leadlet electrode <NUM>, <NUM>, <NUM>, return electrode <NUM>, <NUM>, <NUM>, and/or second electrode <NUM>, <NUM>, <NUM>. Circuitry <NUM> may be operably coupled to leadlet electrode <NUM>, <NUM>, <NUM>, return electrode <NUM>, <NUM>, <NUM>, and/or second electrode <NUM>, <NUM>, <NUM> via one or more conductors. Circuitry <NUM> may be configured to transmit therapy signals using leadlet electrode <NUM>, <NUM>, <NUM>, return electrode <NUM>, <NUM>, <NUM>, and/or second electrode <NUM>, <NUM>, <NUM>, and may be configured to receive data representative of heart <NUM> from leadlet electrode <NUM>, <NUM>, <NUM>, return electrode <NUM>, <NUM>, <NUM>, and/or second electrode <NUM>, <NUM>, <NUM>. In examples, circuitry <NUM> includes one or more processors that are configured to implement functionality and/or process instructions stored in a storage device. Circuitry <NUM> may include, for example, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or equivalent discrete or integrated logic circuitry, or a combination of any of the foregoing devices or circuitry. Circuitry <NUM> may include any suitable structure, whether in hardware, software, firmware, or any combination thereof, to perform the functions ascribed herein to the circuitry.

In examples, circuitry <NUM> is located within a housing of IMD <NUM>, <NUM>, <NUM>. In other examples, circuitry <NUM> is located within another device or group of devices external to IMD <NUM>, <NUM>, <NUM> (e.g., within a device or group of devices not illustrated in <FIG>). As such, techniques and capabilities attributed herein to circuitry <NUM> may be attributed to any combination of IMD <NUM>, <NUM>, <NUM> and other devices that are not illustrated in <FIG>. Hence, medical system <NUM> (<FIG>) may represent a system wherein portions are configured to be implanted within a patient and/or configured to be extracorporeal to a patient, and may include any fixed or mobile computer system (e.g., a controller, a microcontroller, a personal computer, minicomputer, tablet computer, etc.), and may be generally described as including substantially all or some portion of circuitry <NUM>.

A technique for implanting an IMD <NUM>, <NUM>, <NUM> within a heart <NUM> is illustrated in <FIG>. Although the technique is described mainly with reference to IMD <NUM>, <NUM>, <NUM>, <FIG>, the technique may be applied to other medical devices in other examples.

The technique includes rotating a proximal body portion <NUM>, <NUM>, <NUM> relative to a distal body portion <NUM>, <NUM>, <NUM> (<NUM>). The technique may include securing distal body portion <NUM>, <NUM>, <NUM> to tissue within target site <NUM> using fixation mechanism <NUM>, <NUM>, <NUM>. In examples, proximal body portion <NUM>, <NUM>, <NUM> rotates relative to distal body portion <NUM>, <NUM>, <NUM> as fixation mechanism <NUM>, <NUM>, <NUM> substantially maintains distal body portion <NUM>, <NUM>, <NUM> substantially stationary with respect to the tissue within target site <NUM>.

In examples, the technique includes guiding IMD <NUM>, <NUM>, <NUM> through vasculature of a patient to target site <NUM> within heart <NUM> using delivery catheter <NUM>, <NUM>. Delivery catheter <NUM>, <NUM> may substantially retain IMD <NUM>, <NUM>, <NUM> within lumen <NUM> of cup section <NUM> as delivery catheter <NUM>, <NUM> guides IMD <NUM>, <NUM>, <NUM> to target site <NUM>. Delivery catheter <NUM>, <NUM> may retain fixation mechanism <NUM>, <NUM>, <NUM> in a delivery configuration within cup section <NUM> using inner wall <NUM>. In examples, the technique includes exerting a distal force on IMD <NUM>, <NUM>, <NUM> to cause IMD <NUM>, <NUM>, <NUM> to pass through lumen opening <NUM> when, for example, delivery catheter <NUM>, <NUM> positions IMD <NUM>, <NUM>, <NUM> at or in the vicinity of target site <NUM>. Fixation tine <NUM>, <NUM> may expand radially outward from longitudinal axis L of IMD <NUM>, <NUM>, <NUM> when fixation mechanism <NUM>, <NUM>, <NUM> passes through lumen opening <NUM> to secure IMD <NUM>, <NUM>, <NUM> to target site <NUM>.

The technique includes deploying leadlet <NUM>, <NUM>, <NUM> to extend over an extension length LE in a direction away from device body <NUM>, <NUM>, <NUM>. The technique may include exerting a force on leadlet <NUM>, <NUM>, <NUM> to cause leadlet <NUM>, <NUM>, <NUM> to extend away from device body <NUM>, <NUM>, <NUM>. In examples, the technique includes using the rotation of proximal body portion <NUM>, <NUM>, <NUM> relative to distal body portion <NUM>, <NUM>, <NUM> to exert the force on leadlet <NUM>, <NUM>, <NUM>. In examples, the technique includes exerting the force on leadlet <NUM>, <NUM>, <NUM> using an elongated body such as a stylet. Leadlet distal end <NUM>, <NUM> may penetrate tissues at or in the vicinity of target site <NUM> when leadlet <NUM>, <NUM>, <NUM> deploys to extend over the extension length LE. Leadlet <NUM>, <NUM>, <NUM> may pass through leadlet access <NUM>, <NUM>, <NUM> when leadlet <NUM>, <NUM>, <NUM> deploys to extend over the extension length LE.

The technique may include altering the extension length LE defined by leadlet <NUM>, <NUM>, <NUM> using the rotation of proximal body portion <NUM>, <NUM>, <NUM> relative to distal body portion <NUM>, <NUM>, <NUM> (<NUM>). Proximal body portion <NUM>, <NUM>, <NUM> may rotate relative to distal body portion <NUM>, <NUM>, <NUM> in the first rotational direction W1 and/or in the second rotational direction W2. In examples, the rotation of proximal body portion <NUM>, <NUM>, <NUM> relative to distal body portion <NUM>, <NUM>, <NUM> causes the extension length LE to increase. In examples, the rotation of proximal body portion <NUM>, <NUM>, <NUM> relative to distal body portion <NUM>, <NUM>, <NUM> causes the extension length LE to decrease. In examples, the technique includes rotating proximal body portion <NUM>, <NUM>, <NUM> relative to distal body portion <NUM>, <NUM>, <NUM> to align distal marker <NUM> and proximal marker <NUM>.

The technique may include retaining leadlet <NUM>, <NUM>, <NUM> within leadlet stowage space <NUM>, <NUM> as delivery catheter <NUM>, <NUM> transports IMD <NUM>, <NUM>, <NUM> through vasculature of a patient. Leadlet <NUM>, <NUM>, <NUM> may deploy from leadlet stowage space <NUM>, <NUM> when leadlet <NUM>, <NUM>, <NUM> establishes the extension length LE. In examples, the rotation of proximal body portion <NUM>, <NUM>, <NUM> relative to distal body portion <NUM>, <NUM>, <NUM> causes leadlet <NUM>, <NUM>, <NUM> to deploy from the stowage configuration. In examples, the rotation of proximal body portion <NUM>, <NUM>, <NUM> relative to distal body portion <NUM>, <NUM>, <NUM> causes leadlet <NUM>, <NUM>, <NUM> to retract toward device body <NUM>, <NUM>, <NUM> and substantially re-establish the stowage configuration.

The rotation of proximal body portion <NUM>, <NUM>, <NUM> relative to distal body portion <NUM>, <NUM>, <NUM> may cause leadlet <NUM>, <NUM>, <NUM> to substantially establish the extension length LE in a specific direction relative to the longitudinal axis L. In examples, leadlet <NUM>, <NUM>, <NUM> establishes the extension length LE in a direction substantially perpendicular to longitudinal ais L. In examples, leadlet <NUM>, <NUM>, <NUM> establishes the extension length LE in a direction substantially parallel to longitudinal ais L. Directing structure <NUM> may engage leadlet <NUM>, <NUM>, <NUM> to cause leadlet <NUM>, <NUM>, <NUM> to establish the extension length LE in the specific direction relative to longitudinal axis L.

The technique may include causing second electrode <NUM>, <NUM>, <NUM> to contact tissues of heart <NUM> when fixation mechanism <NUM>, <NUM>, <NUM> secures IMD <NUM>, <NUM>, <NUM> to target site <NUM>. The technique may include delivering therapy to and/or sensing cardiac signals from heart <NUM> using circuitry <NUM>. Circuitry <NUM> may deliver therapy and/or sense cardiac signals using leadlet electrode <NUM>, <NUM>, <NUM>, return electrode <NUM>, <NUM>, <NUM>, and/or second electrode <NUM>, <NUM>, <NUM>. Circuitry <NUM> may deliver therapy and/or sense cardiac signals when leadlet <NUM>, <NUM>, <NUM> establishes the extension length LE. Circuitry <NUM> may deliver therapy and/or sense cardiac signals when fixation mechanism <NUM>, <NUM>, <NUM> secures distal body portion <NUM>, <NUM>, <NUM> to tissue at or in the vicinity of target site <NUM>.

Claim 1:
An implantable medical device (<NUM>) configured to deliver pacing therapy, the implantable medical device comprising:
a device body (<NUM>) configured to position within a heart, wherein the device body comprises a proximal body portion (<NUM>) and a distal body portion (<NUM>) and defines a longitudinal axis (L) extending through the proximal body portion and the distal body portion, the proximal body portion is configured to rotate around the longitudinal axis relative to distal body portion; and
a leadlet (<NUM>) mechanically coupled to the device body, wherein the leadlet mechanically supports an electrode (<NUM>), and wherein in response to the proximal body portion rotating relative to the distal body portion, the device body is configured to alter an extension length of the leadlet.