Patent Description:
Various types of implantable medical leads have been implanted for treating or monitoring one or more conditions of a patient. Such implantable medical leads may be adapted to allow medical devices to monitor or treat conditions or functions relating to heart, muscle, nerve, brain, stomach, endocrine organs or other organs and their related functions. Implantable medical leads include electrodes and/or other elements for physiological sensing and/or therapy delivery. Implantable medical leads allow the sensing/therapy elements to be positioned at one or more target locations for those functions, while the medical devices electrically coupled to those elements via the leads are at different locations.

Implantable medical leads, e.g., distal portions of elongated implantable medical leads, may be implanted at target locations selected to detect a physiological condition of the patient and/or deliver one or more therapies. For example, implantable medical leads may be delivered to locations within an atria or ventricle to sense intrinsic cardiac signals and deliver pacing or antitachyarrhythmia shock therapy from a medical device coupled to the lead. In other examples, implantable medical leads may be tunneled to locations adjacent a spinal cord or other nerves for delivering pain therapy from a medical device coupled to the lead Implantable medical leads may include anchoring components to secure a distal end of the lead at the target location.

<CIT> relates to minimally invasive methods for implanting a sacral stimulation lead.

The claimed subject-matter is defined by the independent claim <NUM>. An implantable medical lead comprises a lead body comprising an interior surface with the interior surface defining a lumen. The lead body defines a longitudinal axis extending through the lumen. The lead includes an inner member within the lumen, with the inner member configured to rotate around the longitudinal axis and relative to the inner surface defining the lumen. A dilator including a dilator electrode is coupled to the inner member. The dilator is configured to rotate relative to the inner surface, and the inner member is configured to transmit a torque to the dilator when the inner member rotates around the longitudinal axis of the lead body. The dilator is configured to penetrate tissue when the dilator receives the torque and the dilator contacts the tissue. The implantable medical lead further includes a fixation member (e.g., one or more tines) configured to secure a distal end of the lead body to the tissue. In examples, the implantable medical lead comprises a probe wire configured to extend through an inner lumen and an inner lumen opening of the dilator.

In examples, the dilator defines a dilator axis and includes a helical screw thread on an exterior surface of the dilator, and the helical screw thread is configured to cause the dilator to translate substantially parallel to the dilator axis when the inner member transmits the torque to the dilator and the helical screw thread contacts a tissue in a patient, such as a heart tissue. The inner member may be configured to stretch when the dilator laterally translates within the tissue. In examples, the inner member includes a helical coil configured to stretch when the dilator laterally translates. The implantable lead may include a return electrode mounted to the lead body, and may include a distal electrode mounted distal to the return electrode. The dilator electrode, the distal electrode, and/or the return electrode may be coupled to respective electrical conductors that extend through the lead body, and thereby act as electrodes for sensing and/or therapy.

A technique for delivering a dilator electrode to a target site in a patient includes navigating a lead body to the target site. The technique includes contacting a fixation member (e.g., one or more tines) attached to a distal end of the lead body with tissues at or near the target site, and grasping the tissues using the one or more tines. The technique further includes rotating an inner member within a lumen defined by an interior surface of the lead body, with the rotation relative to the interior surface. The technique includes rotating the dilator including the dilator electrode using the rotation of the inner member, and translating the dilator into the tissues at or near the target site using the rotation of the dilator. The technique may include translating a probe wire through an inner lumen defined by the inner member and the dilator. The technique may include penetrating the tissues at or near the target site with the probe wire and using the probe wire to guide the translation of the dilator into the tissues.

This disclosure describes an implantable medical lead configured to deliver a dilator electrode to tissues at a target site within a patient. A dilator including the dilator electrode is configured to translate laterally and penetrate tissues at or near the target site, allowing for delivery of electrical stimulation therapies to the tissue. For example, the dilator may be configured to penetrate the septum of a patient's heart in order to deliver electrical stimulations to activate a left bundle branch (LBB), other conduction system tissues, and/or or other ventricular tissues of the heart. The dilator is configured to penetrate the tissues as a clinician causes the dilator to rotate about a dilator axis. The dilator may be configured such that control of the rotation controls a depth to which the dilator penetrates the tissues (e.g., ventricular tissues), allowing the dilator to be substantially positioned at a pre-determined location based on, for example, pace mapping. The implantable medical lead includes an inner member allowing a clinician to transmit a torque causing rotation of the dilator and providing for control of the penetration depth. In examples, the implantable medical lead includes a probe wire and a probe electrode configured to penetrate the tissues at or near the target site (e.g., prior to penetration by the dilator). The probe wire may be configured to conduct pace mapping within the tissue, and may be configured to serve as a guiding wire for the dilator during dilator rotation and penetration of the tissue.

The implantable medical lead includes an elongated lead body having an interior surface defining a lead body lumen and defining a lumen opening at a distal end of the lead body. The lead body includes a fixation member (e.g., one or more tines) configured to extend from the distal end of the lead body and implant within tissue, such that the distal end of the lead body may be substantially anchored within a tissue wall (e.g., a septal wall) at or near the target site. In examples, the distal end of the lead body is delivered to the tissue wall using a delivery catheter, and the tines are resiliently biased to expand radially outward as the lead body is distally displaced relative to the delivery catheter (e.g., the lead body is distally extended relative to the delivery catheter and/or the delivery catheter is proximally withdrawn relative to the lead body).

The lead body lumen is configured to surround the dilator, and configured such that the dilator may slidably translate through the lead body lumen and through the lumen opening. Further, the dilator is configured to be rotatable within the lead body lumen about the dilator axis. An exterior surface of the dilator is configured such that, when a distal end of the dilator is in contact with tissues at or near the target site, a rotation of the dilator may at least in part cause the dilator to penetrate and translate within the tissue. In examples, the dilator exterior surface defines a helical thread pattern around the dilator axis, with the helical thread pattern configured to engage the tissue and convert a rotation of the dilator around the dilator axis into a lateral translation substantially parallel to the dilator axis. The lateral translation of the dilator may cause the dilator to travel from a location at least partially within the lead body lumen, through the lumen opening at the distal end of the lead body, and into tissues at or near the target site. In some examples, when the one or more tines anchor the lead body distal end to a tissue wall (e.g., a septal wall), the dilator may be slidably translated toward the lead body distal end to cause contact between the tissue wall and a distal end of the dilator. In some examples, when the one or more tines anchor the lead body distal end to a tissue wall, the dilator may be positioned within the lead body lumen such that the distal end of the dilator is in contact with the tissue wall when the one or more tines anchor.

An inner member is attached to a proximal end of the dilator and additionally extends through the lead body lumen. At least some portion of the inner member (e.g., the portion attached to the proximal end of the dilator) is configured to pass through the lumen opening of the lead body lumen. The inner member is rotatable within the lead body lumen and configured to transmit a torque to the dilator, such that when the inner member rotates within the lead body lumen (e.g., is caused to rotate by a clinician), the inner member causes the dilator to rotate substantially synchronously with the inner member. The inner member may be a coil (e.g., a helical coil) configured to transfer the torque to the dilator. In addition, the inner member may be expandable lengthwise, such that a displacement between a first point on the inner member and a second point on the inner member increases when a distally directed force is exerted on a distal end of the inner member (e.g., exerted by the dilator during tissue penetration). Thus the inner member may stretch within the lead body lumen when the dilator penetrates and translates within the tissue. In examples, the lengthwise expansion of the inner member allows lead body to remain attached to the lead body as the dilator translates into the tissue.

The implantable medical lead may be configured to conduct pace mapping within the septum or other ventricular tissues (e.g., prior to dilator penetration) using a probe wire extending through the implantable medical lead. The probe wire may extend through a channel defined by the inner member and through an inner lumen of the dilator. The probe wire is slidably translatable within the channel and the inner lumen, and configured such that at least a portion of the probe wire may be extended from an inner lumen opening at a distal end of the dilator. The probe wire may penetrate the tissues and place a probe electrode (e.g., an uninsulated section of the probe wire) in contact with a tissue interior, such as the interior of a septal wall. In examples, the probe electrode is in electrical communication with processing circuitry configured to deliver electrical therapy and/or conduct electrical sensing via the probe electrode. A clinician may manipulate the slidably translatable probe wire to vary a depth of the probe electrode in the tissue (e.g., in a septal wall) in order to conduct pace mapping with limited distortion of the target tissue area.

In examples, a distal portion of the probe wire includes a shape memory alloy configured to define a curvature of the probe wire when the distal portion is unconstrained by surrounding tissue. For example, the shape memory alloy may be configured to define a curvature when the distal portion of the probe wire has passed from a right ventricle of heart through the septum and entered the left ventricle. The distal portion of the probe may be resiliently biased to form a relatively compact configuration, such that a straight-line displacement between two points on the distal portion is less than a displacement measured along the probe wire itself. For example, the distal portion of the probe wire may be configured to form a loop (e.g., helix) or some other shape. The relatively compact configuration may serve to substantially retain the distal end of the probe wire nearer to the septal wall (e.g., in the left ventricle), as well as serve as a fluoroscopy marker for the septal wall (e.g., the endocardial surface of the septal wall).

<FIG> is a conceptual diagram illustrating a portion of an example medical device system <NUM> including an implantable medical lead <NUM>. Implantable medical lead <NUM> includes an elongated lead body <NUM> with a distal portion <NUM> positioned at a target site <NUM> within a patient <NUM>. Distal portion <NUM> may be, for example, a sleeve head of implantable medical lead <NUM>. In some examples, as illustrated in <FIG>, the target site <NUM> may include a portion of a heart <NUM>, such as an interventricular septal wall of a right ventricle (RV) of heart <NUM>, as illustrated in <FIG>, or atrioventricular septal wall of a right atrium (RA) of heart <NUM> or other locations within a body of patient <NUM>. A clinician may maneuver distal portion <NUM> through the vasculature of patient <NUM> in order to position distal portion <NUM> at or near target site <NUM>. For example, the clinician may guide distal portion <NUM> through the superior vena cava (SVC), into the RA, and past the Tricuspid valve into the RV in order to access target site <NUM> on the atrioventricular septal wall. In some examples, other pathways or techniques may be used to guide distal portion <NUM> into other target implant sites within the body of patient <NUM>. Medical device system <NUM> may include a delivery catheter and/or outer member (not shown), and implantable medical lead <NUM> may be guided and/or maneuvered within a lumen of the delivery catheter in order to approach target site <NUM>. For example, in one or more examples described herein, target site <NUM> may be the triangle of Koch region in the atrioventricular septal wall of the patient's heart or the ventricular septal wall in the basal (e.g., high basal or high septal) region or apical (e.g., low septal or near the apex) region. Implantable medical lead <NUM> includes one or more tines (not shown) configured to grasp tissues at or near target site <NUM> and substantially secure a distal end of implantable medical lead <NUM> to the target site. For example, the one or more tines may be configured to substantially secure the distal end of implantable medical lead <NUM> to tissues of the interventricular septal wall of a right ventricle (RV) of heart <NUM>.

Implantable medical lead <NUM> includes a dilator <NUM> including a dilator electrode. Dilator <NUM> is configured to penetrate the tissues at or near target site <NUM>. For example, dilator <NUM> may be configured to penetrate the atrioventricular septal wall of a right ventricle (RV) of heart <NUM> in order to stimulate the LBB of heart <NUM> using the dilator electrode. The dilator electrode of dilator <NUM> may be electrically connected to a conductor (not shown) extending through implantable medical lead <NUM> from the dilator electrode. In examples, the conductor is electrically connected to therapy delivery circuitry of an implantable medical device (IMD) <NUM>, with the therapy delivery circuitry configured to provide electrical signals through the conductor to the dilator electrode of dilator <NUM>. The dilator electrode may conduct the electrical signals to the target tissue of heart <NUM>, causing the cardiac muscle, e.g., of the ventricles, to depolarize and, in turn, contract at a regular interval. In examples in which dilator <NUM> penetrates to a position at or near the HB, RBB, LBB, or other specialized conductive tissue of heart <NUM>, the cardiac pacing delivered via the dilator electrode may be conduction system pacing (CSP) of heart <NUM>, which may provide more physiologic activation and contraction of heart <NUM>. Dilator <NUM> may also be connected to sensing circuitry of IMD <NUM> via the conductor, and the sensing circuitry may sense electrical activity of heart <NUM> via dilator <NUM> (e.g., via the dilator electrode).

In some examples, dilator <NUM> is configured to be rotatable using inner member <NUM>, and dilator <NUM> is configured to penetrate the tissues as the rotation occurs. For example, dilator <NUM> may define a helical screw thread configured to engage tissues at or near target site <NUM> and convert a rotation of dilator <NUM> into a lateral translation of dilator <NUM> into the tissue. The rotation of inner member <NUM> and dilator <NUM> may be controlled by a clinician, such that dilator <NUM> may be positioned relatively precisely within the atrioventricular septal wall. For example, a clinician may control the rotation of inner member <NUM> and dilator <NUM> by rotating a connector pin on the proximal end of lead body <NUM>. In some examples, a proximal end of inner member <NUM> is configured to substantially maintain electrical contact with processing circuitry as inner member <NUM> is rotated. For example, a proximal end of inner member <NUM> may have an uninsulated section configured to establish electrical contact with a component (e.g., an alligator clip) electrically connected to the processing circuitry. The uninsulated section may be configured to maintain the electrical contact with the component (e.g., the alligator clip) as inner member <NUM> is rotated. This may rotation of inner member <NUM> without an attendant requirement to electrically disconnect and/or reconnect inner member <NUM> to the processing circuitry.

As will be discussed, in some examples, dilator <NUM> and inner member <NUM> may be guided to target site <NUM> using a probe wire (not shown) configured to penetrate the tissues at or near target site <NUM>. The probe wire may include a probe electrode connected to processing circuitry configured to sense a condition using the probe electrode as probe wire penetrates the tissues. For example, the probe wire may be connected to processing circuitry configured to electrically map within the interventricular septal wall in order to locate advantageous positions for conduction system pacing using the LBB.

<FIG>, <FIG>, and <FIG> are conceptual diagrams illustrating a plan view of a portion of an implantable medical lead <NUM> in various operating configurations. Implantable medical lead <NUM> is an example of implantable medical lead <NUM> (<FIG>). <FIG>, <FIG>, and <FIG> depict implantable medical lead <NUM> in the proximity of a target site <NUM> on a tissue wall <NUM> of tissue <NUM>. Tissue wall <NUM> may be, for example, the interventricular septal wall of a right ventricle (RV) of heart <NUM>, and tissue <NUM> may be the septum of heart <NUM> (<FIG>). Implantable medical lead <NUM> includes lead body <NUM>, distal portion <NUM> of lead body <NUM> ("lead body distal portion <NUM>"), dilator <NUM>, and inner member <NUM>, which may be configured similarly to and operate relative to other implantable medical lead <NUM> components in the same manner as the like-named components of implantable medical lead <NUM>. Further, although <FIG> and <FIG> depict implantable medical lead <NUM> within a lumen of a delivery catheter <NUM> for the purpose of discussing various operating modes of implantable medical lead <NUM>, implantable medical lead <NUM> may operate in either the absence or the presence of delivery catheter <NUM>. <FIG>, <FIG>, <FIG> illustrate a longitudinal cross-section of lead body <NUM> and delivery catheter <NUM>, with a cutting plane taken parallel to the page.

<FIG> depicts implantable medical lead <NUM> including lead body <NUM> positioned within a lumen of delivery catheter <NUM>. Lead body <NUM> comprises an interior surface <NUM> ("lead interior surface <NUM>") surrounding a longitudinal axis L defined by lead body <NUM>. Lead interior surface <NUM> defines a lumen <NUM> ("lead body lumen <NUM>"), and defines an opening <NUM> to lead body lumen <NUM> ("lumen opening <NUM>") at a distal end <NUM> of lead body <NUM> ("lead distal end <NUM>"). Implantable medical lead <NUM> includes dilator <NUM> positioned within lead body lumen <NUM>, and inner member <NUM> extending through lead body lumen <NUM>. Inner member <NUM> and dilator <NUM> are configured to rotate within lumen <NUM> relative to interior surface <NUM>. Additionally, inner member <NUM> is configured to transmit a torque to dilator <NUM>, such that when inner member <NUM> rotates substantially around a longitudinal axis L defined by lead body <NUM>, inner member <NUM> causes a rotation of dilator <NUM> around longitudinal axis L.

In general, a tine 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 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.

One or more tines such as tine <NUM> extend distally from lead body <NUM> around lumen opening <NUM>. In general, a tine may refer to any structure that is capable of securing a lead or leadless implantable medical device to a tissue at a target site (e.g., target site <NUM> (<FIG>)) within a patient. In some examples, a tine may be composed of a shape-memory that allows deformation along the length of the tine. A tine may be substantially flat along the length of the tine. Tine <NUM> includes a fixed end <NUM> coupled to lead body <NUM> and a free end <NUM> opposite fixed end <NUM>. In the configuration depicted in <FIG>, tine <NUM> is depicted in a delivery configuration, wherein free end <NUM> is distal to a midpoint M on tine <NUM> between fixed end <NUM> and free end <NUM>. Additionally, although <FIG> depicts implantable medical lead <NUM> (e.g., free end <NUM> of tine <NUM>) in close proximity to a distal end <NUM> of delivery catheter <NUM> ("delivery catheter distal end <NUM>"), implantable medical lead <NUM> is slidably translatable within delivery catheter <NUM> and may be located anywhere in delivery catheter <NUM> relative to delivery catheter distal end <NUM>.

A probe wire <NUM> including a probe electrode <NUM> extends substantially parallel to longitudinal axis L through an inner channel (not illustrated) of inner member <NUM> and an inner lumen (not illustrated) defined by dilator <NUM>. Probe wire <NUM> extends through an inner lumen opening substantially at a distal end <NUM> of dilator <NUM> ("dilator distal end <NUM>"). Probe wire <NUM> is slidably translatable within the inner channel of inner member <NUM>, within the inner lumen of dilator <NUM>, and through the inner lumen opening, such that probe wire <NUM> may be manipulated to move both distally and proximally relative to, for example, dilator <NUM> and/or interior surface <NUM>. Probe wire <NUM> is configured to penetrate tissue wall <NUM> and establish probe electrode <NUM> within tissue <NUM>. Probe electrode <NUM> may be in electrical communication with processing circuitry configured to deliver electrical therapy and/or conduct electrical sensing via probe electrode <NUM>. Thus, with implantable medical lead <NUM> positioned proximal to delivery catheter distal end <NUM>, a clinician may manipulate the slidably translatable probe wire <NUM> to position probe electrode <NUM> to various depths within tissue <NUM> and utilize the processing circuitry to conduct pace mapping within tissue <NUM>. For example, probe wire <NUM> may be placed at various depths across a septum of a heart in order to determine an advantageous location for stimulation of an LBB for conduction system pacing (CSP) of the heart. In examples, probe wire <NUM> is a relatively small diameter wire configured to penetrate and be repositioned with reduced (or minimal) trauma to the tissue <NUM>. Probe wire <NUM> may be a memory shape alloy configured to substantially straighten when probe wire <NUM> is pulled proximally through tissue <NUM>.

In examples, probe wire <NUM> includes a conductor substantially covered by an insulating jacket, and probe electrode <NUM> is a section of the conductor without the insulating jacket (e.g., with the insulating jacket removed). Other electrode configurations may be used in other examples. Implantable medical lead <NUM> further includes a return electrode <NUM> on lead body <NUM>. In some examples, implantable medical lead <NUM> includes a distal electrode <NUM> positioned adjacent to or near lead distal end <NUM>.

<FIG> illustrates a distal portion <NUM> of probe wire <NUM> ("probe distal portion <NUM>") advanced completely through tissue <NUM> and forming a loop <NUM>. <FIG> additionally depicts lead distal end <NUM> adjacent tissue wall <NUM> and tine <NUM> penetrating tissue wall <NUM>, however medical lead <NUM> is configured such that probe wire <NUM> may be advanced through tissue <NUM> and form loop <NUM> with lead distal end <NUM> and tine <NUM> remaining substantially in the positions depicted in <FIG>.

In examples, probe distal portion <NUM> includes a shape-memory alloy configured to define a curvature (e.g., loop <NUM>) when probe distal portion <NUM> is unconstrained by surrounding tissues. For example, probe distal portion <NUM> may be configured to define the curvature of loop <NUM> when probe distal portion <NUM> is within a cardiac chamber of heart <NUM> (<FIG>), such as a left atrium, left ventricle, right atrium, or right ventricle. Probe distal portion <NUM> may be configured to assume the relaxed, zero-stress condition when probe distal portion <NUM> is in a substantially zero-stress position, where any stresses on probe distal portion <NUM> arise from properties or phenomena purely internal to probe distal portion <NUM>, such as mass, internal temperature, residual stresses, and the like. In examples, probe distal portion <NUM> may be imaged using fluoroscopy or other imaging techniques, such that loop <NUM> may serve as a visible marker. For example, loop <NUM> may serve as a visible marker indicating an approximate location of an endocardial surface of an interventricular septal wall of a left ventricle (LV) of heart <NUM>.

As discussed, <FIG> depicts lead distal end <NUM> substantially adjacent tissue wall <NUM> and tine <NUM> having penetrated tissue wall <NUM>. Tine <NUM> is configured to penetrate tissues when lead body <NUM> is translated proximally toward tissue wall <NUM>. In examples, tine <NUM> is resiliently biased such that, unless sufficiently constrained (e.g., by delivery catheter <NUM>) to maintain the delivery configuration depicted in <FIG>, free end <NUM> tends to expand radially outward from longitudinal axis L to assume a delivery configuration. Tine <NUM> may be resiliently biased to cause free end <NUM> to pivot radially outward. For example, <FIG> depicts delivery catheter <NUM> withdrawn proximally such that delivery catheter distal end <NUM> is proximal to at least free end <NUM> of tine <NUM>, such that tine <NUM> is relatively unconstrained. In an example, tine <NUM> establishes a first radial distance from free end <NUM> to longitudinal axis L in the delivery configuration and a second radial distance from free end <NUM> to longitudinal axis L in the deployment configuration, and the second radial distance is greater than the first radial distance. In some examples, free end <NUM> is proximal to midpoint M in the deployed configuration (e.g., tine <NUM> forms a U-shape in the deployed configuration).

<FIG> additionally depicts dilator <NUM> positioned within lead body lumen <NUM> and substantially adjacent tissue wall <NUM>. Dilator <NUM> is in a first position proximal to lead distal end <NUM>. As previously discussed, dilator <NUM> is rotatable within lead body lumen <NUM> and configured to axially translate (e.g., substantially parallel to longitudinal axis L) within lead body lumen <NUM>. Inner member <NUM> is configured to transmit a torque to dilator <NUM> and cause a rotation of dilator <NUM> about longitudinal axis L. Dilator <NUM> is configured such that rotation of dilator <NUM> may cause the dilator to penetrate tissue wall <NUM> and translate within tissue <NUM>. Loop <NUM> of probe wire <NUM> may be utilized as a fluoroscopy marker during the penetration of dilator <NUM> to assist in the placement of dilator <NUM> and dilator electrode <NUM> within tissue <NUM>. For example, loop <NUM> may substantially mark a location of the LV endocardium as dilator <NUM> is rotated by inner member <NUM> for penetration of an interventricular septal wall. Loop <NUM> may act to stabilize probe wire <NUM> within tissue <NUM> to assist dilator <NUM> in traveling into tissue <NUM>.

<FIG> illustrates dilator <NUM> having penetrated tissue wall <NUM> and within tissue <NUM> as a result of rotation about the longitudinal axis L by inner member <NUM>. Delivery catheter <NUM> and probe wire <NUM> (<FIG>, <FIG>) have been withdrawn proximally, although this is not necessary in all examples. Rotation of dilator <NUM> by inner member <NUM> has caused dilator <NUM> to translate from the first position proximal to lead distal end <NUM> (<FIG>) to a second position distal to lead distal end <NUM>. In the second position distal to lead distal end <NUM>, dilator electrode <NUM> is in contact with tissues <NUM>. In an example, dilator <NUM> is positioned distal to lead distal end <NUM> such that dilator electrode <NUM> is substantially located at a position within tissue <NUM> identified by probe electrode <NUM>. Implantable medical lead <NUM> may be configured to allow dilator <NUM> to penetrate a septum of heart <NUM> (<FIG>) to a depth such that dilator electrode <NUM> may stimulate the LBB of heart <NUM>. Implantable medical lead <NUM> may be configured to allow dilator <NUM> to penetrate to a depth substantially determined by probe wire <NUM> during, for example, pace mapping of a septum or other ventricular tissues.

In some examples, dilator electrode <NUM> is mounted on an exterior surface <NUM> of dilator <NUM> ("dilator exterior surface <NUM>") and is a substantially separate component from dilator exterior surface <NUM>. In some examples, dilator electrode <NUM> comprises some or all of dilator exterior surface <NUM>. In some examples, some or all of exterior surface <NUM> is an electrically conductive material substantially covered by an insulative material, with dilator electrode <NUM> defined by one or more portions of dilator exterior surface <NUM> where the insulative material is removed (e.g., a masked electrode). The insulative material may be is selectively removed at one or more locations to define dilator electrode <NUM> at a specific location on dilator <NUM>, and/or to define a pattern of locations through which dilator electrode <NUM> may act.

Dilator exterior surface <NUM> may be configured such that, when dilator distal end <NUM> is in contact with tissue wall <NUM> and/or tissue <NUM>, rotation of dilator <NUM> causes dilator <NUM> to penetrate tissue wall <NUM> and/or tissue <NUM>. In examples, dilator exterior surface <NUM> is configured to engage with a surrounding environment (e.g., tissue <NUM>) and convert a rotation of dilator <NUM> around longitudinal axis L into a translation of dilator <NUM> substantially parallel to longitudinal axis L. For example, dilator exterior surface <NUM> may define a helical thread pattern configured to engage tissue wall <NUM> and/or tissue <NUM> and convert a rotation of the dilator around a dilator axis defined by dilator <NUM> into a lateral translation substantially parallel to the dilator axis.

Inner member <NUM> may be configured to expand lengthwise (e.g., along longitudinal axis L) as inner member <NUM> transmits a torque to dilator <NUM> and dilator <NUM> translates within tissue <NUM>. For example, inner member <NUM> may have a first configuration where a first point P1 on inner member <NUM> is displaced from a second point P2 by a displacement D1 (<FIG>), and have a second configuration where the first point P1 is displaced from the second point P2 by a displacement D2 (<FIG>), where D2 is greater than D1. Inner member <NUM> may be configured to substantially transition from the first configuration to the second configuration as dilator <NUM> translates substantially parallel to longitudinal axis L due to a rotation by inner member <NUM>. Thus, some portion of or substantially all of inner member <NUM> may stretch within lead body lumen <NUM> when dilator <NUM> penetrates and translates within tissue <NUM>. In an example, inner member <NUM> includes a helical coil around longitudinal axis L and configured to stretch while transferring a torque to dilator <NUM>.

Lead body <NUM> may be configured such that distal electrode <NUM> is adjacent to or located on lead distal end <NUM>. Lead body <NUM> may be configured such that distal electrode <NUM> is adjacent to or in contact with a tissue wall when lead distal end <NUM> is in contact with the tissue wall and/or the one or more tines (e.g., tine <NUM>) penetrate the tissue wall. Distal electrode <NUM> may be in electrical communication with processing circuitry configured to deliver electrical therapy and/or conduct electrical sensing via distal electrode <NUM>. For example, distal electrode <NUM> may contact the RV endocardium of a heart <NUM> (<FIG>) when tine <NUM> when lead distal end <NUM> is in contact with the RV endocardium and/or tine <NUM> penetrates the RV endocardium. Distal electrode <NUM> may be configured to stimulate an interventricular septum of heart <NUM>. Thus, implantable medical lead <NUM> may be configured such that dilator <NUM> and dilator electrode <NUM> may penetrate an interventricular septum to a depth sufficient to stimulate the LBB of heart <NUM> while distal electrode <NUM> is positioned adjacent or on the RV endocardium for stimulation of the RBB or right ventricular septum of heart <NUM>.

<FIG> illustrates an implantable medical lead <NUM> illustrating lead body <NUM>, dilator <NUM>, and inner member <NUM> in cross-section, with a cutting plane taken parallel to the page. <FIG> illustrates lead body <NUM>, lead body distal portion <NUM>, fixed end <NUM> and free end <NUM> of tine <NUM>, dilator <NUM>, dilator electrode <NUM>, inner member <NUM>, probe wire <NUM>, probe electrode <NUM>, lead interior surface <NUM>, lead body lumen <NUM>, lumen opening <NUM> at lead distal end <NUM>, return electrode <NUM>, distal electrode <NUM>, and dilator distal end <NUM>.

Dilator <NUM> is configured to rotate relative to lead interior surface <NUM>. Dilator <NUM> is rotationally coupled to inner member <NUM>, such that a rotation of inner member <NUM> around longitudinal axis L causes a rotation of dilator <NUM> around longitudinal axis L. In examples, inner member <NUM> is rotationally coupled to dilator <NUM> such that, when inner member <NUM> rotates about longitudinal axis L, dilator <NUM> rotates synchronously with inner member <NUM> about longitudinal axis L. Dilator <NUM> is configured to receive a torque imparted by inner member <NUM> and rotate (e.g., around longitudinal axis L) in response to the imparted torque. Dilator <NUM> may be configured to rotate substantially synchronously with inner member <NUM>. In examples, dilator <NUM> is configured to translate in a direction substantially parallel to longitudinal axis L when inner member <NUM> rotates dilator <NUM>.

Here and elsewhere, when a first component is rotationally coupled to a second component, this means a rotation of the first component causes a rotation of the second component. In examples, the rotation of the first component around an axis causes the rotation of the second component around the axis. The rotation of the first component in a particular direction (e.g., clockwise) around the axis may cause the rotation of the second component in the particular direction around the axis. In examples, the rotation of the first component causes the second component to rotate substantially synchronously with the first component.

Dilator <NUM> may be configured to convert a rotation (e.g., caused by inner member <NUM>) into a lateral translation relative to interior surface <NUM>, with the lateral translation substantially parallel to longitudinal axis L. Dilator <NUM> may convert the rotation into a lateral translation in the distal direction D. In examples, dilator <NUM> is configured such that rotation of dilator <NUM> in a first direction (e.g., clockwise) around longitudinal axis L generates a lateral translation of dilator <NUM> in a first lateral direction (e.g., the distal direction D), and a rotation of dilator <NUM> in a second direction (e.g., counter-clockwise) opposite the first direction generates a lateral translation of dilator <NUM> in a second lateral direction (e.g., the proximal direction P). In examples, dilator <NUM> includes a set of helical threads configured to engage a material surrounding dilator <NUM> (e.g., tissue <NUM> (<FIG>, <FIG>, <FIG>)) and convert the rotation of dilator <NUM> into the lateral translation of dilator <NUM>.

For example, <FIG> illustrates dilator <NUM> including helical threads <NUM>. Dilator <NUM> defines a dilator axis D passing through dilator distal end <NUM> and a proximal end of dilator proximal <NUM> ("dilator proximal end <NUM>"). Dilator axis D may be substantially parallel to longitudinal axis L. Dilator <NUM> is configured such that helical threads <NUM> substantially surround dilator axis D. Helical threads <NUM> are configured such that, when helical threads <NUM> engage surrounding material <NUM>, helical threads <NUM> convert a rotation of dilator <NUM> about dilator axis D into a lateral translation of dilator <NUM> through material <NUM> in a direction substantially parallel to dilator axis D. Dilator <NUM> may be caused to rotate by a rotation of inner member <NUM>. Helical threads <NUM> define a screw thread lead which substantially determines the lateral translation of dilator <NUM> (e.g., the thread advance) that occurs due to a given amount of rotation of inner member <NUM> around longitudinal axis L. Hence, rotation of inner member <NUM> may be used to control the lateral translation of dilator <NUM> within surrounding material <NUM>. <FIG> further illustrates dilator electrode <NUM> and probe wire <NUM> forming a loop (e.g., loop <NUM> (<FIG>)).

Helical threads <NUM> may be any type of thread capable of engaging surrounding material <NUM>. Helical threads <NUM> may have any pitch, thread angle, major diameter, and root diameter. Helical threads <NUM> may be configured as V threads, square threads, acme threads, buttress threads, right-handed threads, left-handed threads, and other configurations. Dilator exterior surface <NUM> may define helical threads <NUM>. In examples, helical threads <NUM> have a unitary body construction with dilator exterior surface <NUM>, such that helical threads <NUM> and dilator exterior surface <NUM> are inseparable portions of dilator <NUM>. In some examples, helical threads <NUM> comprise a separate thread insert or other component installed around some portion of dilator <NUM>.

<FIG> illustrates an example dilator <NUM> including helical threads <NUM> defined by a dilator exterior surface <NUM>. Dilator <NUM> is an example of dilator <NUM>, <NUM>. Helical threads <NUM> extend around a dilator axis D substantially from dilator distal end <NUM> to dilator proximal end <NUM>. An inner member <NUM> is mechanically attached to dilator proximal end <NUM>. Inner member <NUM> is configured to transmit a torque around dilator axis D to dilator <NUM>. A probe wire <NUM> extends through an inner lumen (not shown) of dilator <NUM>. In the example of <FIG>, dilator exterior surface <NUM> comprises an electrically conducting material and substantially defines dilator electrode <NUM> as a part of or substantially all of dilator exterior surface <NUM>. For example, dilator exterior surface <NUM> may be substantially covered by an insulative material, with dilator electrode <NUM> defined by a portion of dilator exterior surface <NUM> where the insulative material is removed. As discussed, in other examples, dilator electrode <NUM> may be mounted on dilator exterior surface <NUM> as a substantially separate component from dilator exterior surface <NUM>.

<FIG> illustrates an example dilator <NUM> having dilator exterior surface <NUM>. Dilator <NUM> is an example of dilator <NUM>, <NUM>. Dilator exterior surface <NUM> is configured to define a prolate spheroid shape substantially around dilator axis D. The prolate spheroid shape may extend substantially from dilator distal end <NUM> to dilator proximal end <NUM>. In some examples, dilator distal end <NUM> may be configured to facilitate penetration of dilator <NUM> into tissue when dilator <NUM> rotates (e.g., rotates clockwise, counter-clockwise, and/or alternately clockwise and counter-clockwise). For example, dilator distal end <NUM> may include a bevel configured to facilitate the penetration. An inner member <NUM> is mechanically attached to dilator proximal end <NUM>, with inner member <NUM> configured to transmit a torque around dilator axis D to dilator <NUM>. The prolate spheroid shape of dilator <NUM> is configured to at least enable a translation of dilator <NUM> in a direction substantially parallel to dilator axis D when inner member <NUM> causes a rotation of dilator <NUM> around dilator axis D. Dilator exterior surface <NUM> may comprise an electrically conducting material and substantially define a dilator electrode <NUM> as a part of or substantially all of dilator exterior surface <NUM>. In examples, dilator exterior surface may be substantially covered by an insulative material, with dilator electrode <NUM> defined by a portion of dilator exterior surface where the insulative material is removed. In other examples, dilator electrode <NUM> is mounted on exterior surface <NUM> as a substantially separate component from dilator exterior surface <NUM>.

In examples, dilator <NUM>, <NUM>, <NUM> includes an anti-rotation feature configured to limit and/or eliminate rotation of dilator <NUM>, <NUM>, <NUM> caused by a force on dilator <NUM>, <NUM>, <NUM> acting in the proximal direction P. The anti-rotation feature may be configured to limit and/or eliminate rotation due to a force exerted on dilator <NUM>, <NUM>, <NUM> by inner member <NUM> due to an elasticity of inner member <NUM> (e.g., when inner member <NUM> stretches such that D2 is greater than D1 (<FIG>, <FIG>)). The anti-rotation feature may be configured such that a torque on dilator <NUM>, <NUM>, <NUM> necessary to cause dilator <NUM>, <NUM>, <NUM> to move in a first direction (e.g., the proximal direction P) within tissue <NUM> (<FIG>) is greater than a torque on dilator <NUM>, <NUM>, <NUM> necessary to cause dilator <NUM>, <NUM>, <NUM> to move in a second direction opposite the first direction (e.g., the distal direction D) within tissue <NUM> (<FIG>). The anti-rotation feature may be, for example, a ramp formed on some portion of dilator exterior surface <NUM>. The ramp may be configured to cause a first resistance to movement caused by the torque in the first direction and a second resistance to movement cause by the torque in the second direction, with the first resistance greater than the second resistance. In some examples, inner member <NUM> has a greater torsional strength when delivering the torque in the first direction to dilator <NUM>, <NUM>, <NUM> than when delivering the torque in the second direction to dilator <NUM>, <NUM>, <NUM>.

Returning to <FIG>, dilator <NUM> is configured to allow passage of probe wire <NUM> through at least some portion of dilator <NUM>. For example, dilator <NUM> may define an inner lumen <NUM> and an inner lumen opening <NUM>, with inner lumen <NUM> and inner lumen opening <NUM> sized to allow at least some portion of probe wire <NUM> (e.g., probe distal portion <NUM> (<FIG>)) to pass therethrough. Inner lumen <NUM> may substantially extend from dilator proximal end <NUM> to dilator distal end <NUM>. Inner lumen opening <NUM> may be substantially located at dilator distal end <NUM>. In examples, inner lumen <NUM> substantially surrounds dilator axis D. Inner lumen <NUM> and inner lumen opening <NUM> are configured to allow slidable translation of at least probe distal portion <NUM> and probe electrode <NUM> through inner lumen <NUM> and inner lumen opening <NUM>, such that an extension of probe electrode <NUM> distal to dilator distal end may be varied as a result of a pushing force (e.g., in the distal direction D) or a pulling force (e.g., in the proximal direction P) applied to probe wire <NUM>.

As discussed, dilator <NUM> is depicted in <FIG> as a longitudinal cross-section with a cutting plane parallel to the page. Dilator <NUM> may have any longitudinal cross-section sufficient to convert a rotation about longitudinal axis L into a lateral translation of dilator <NUM> substantially parallel to longitudinal axis L. Further, dilator <NUM> may have any axial cross-section sufficient to engage a surrounding material <NUM> (<FIG>). The axial cross-section of dilator <NUM> may be circular, oval shaped, polygonal, and may include straight and curved segments. The axial cross-section of dilator <NUM> may be substantially solid over substantially all or a portion of the axial cross-section, and may define open areas.

In some examples, dilator <NUM> includes a plug <NUM>. In examples, plug <NUM> is configured to extend into inner lumen <NUM> to restrict and/or block a flow of fluid through inner lumen <NUM> (e.g., from lumen opening <NUM>). Probe wire <NUM> may be configured to puncture and pass through plug <NUM> when probe wire <NUM> extends through inner lumen <NUM>. In examples, plug <NUM> may comprise an expandable material (e.g., silicone) configured to substantially expand against a periphery of probe wire <NUM> when probe wire <NUM> passes through plug <NUM>. In examples, plug <NUM> is configured to expand and substantially block inner lumen <NUM> when probe wire <NUM> is proximally withdrawn from inner lumen <NUM> and/or plug <NUM>. In some examples, plug <NUM> comprises a material configured to swell when in contact with a fluid (e.g., water). In some examples, plug <NUM> is configured to release a therapeutic agent such as a steroid when in contact with a fluid within a patient.

Inner member <NUM> is configured to transmit a torque to dilator <NUM> and cause dilator <NUM> to rotate about dilator axis D and/or longitudinal axis L. Inner member <NUM> is configured to rotate (e.g., about longitudinal axis L) within lead body lumen <NUM> and relative lead interior surface <NUM>. Additionally, at least some portion of inner member <NUM> may be configured to axially translate (e.g., substantially parallel to longitudinal axis L) relative to lead interior surface <NUM>. For example, some portion of inner member <NUM> (e.g., point P2 (<FIG>)) may be configured to axially translate within lead body lumen <NUM> when inner member <NUM> stretches as dilator <NUM> axially translates in the distal direction D. Inner member <NUM> may extend from dilator <NUM> through lead body lumen <NUM> and through an opening (not shown) proximal to lead body distal portion <NUM>, such that a torque may be imparted on inner member <NUM> from a location outside of lead body distal portion <NUM>. Inner member <NUM> may be configured to transmit the exerted torque through implantable medical lead <NUM> to dilator <NUM>, in order to effect a rotation of dilator <NUM> relative to lead interior surface <NUM>. In examples, inner member <NUM> is configured such that a clearance C is present between some portion of inner member <NUM> and lead interior surface <NUM> to assist in the independent rotation and translation of inner member <NUM> relative to lead interior surface <NUM>, although this is not required. Inner member <NUM> may be configured to contact (intentionally or incidentally) lead interior surface <NUM> over some portion of or substantially all of inner member <NUM>.

Inner member <NUM> may be configured to allow passage of probe wire <NUM> through at least some portion of inner member <NUM>. For example, inner member <NUM> may define a channel <NUM> ("Inner member channel <NUM>") sized to allow at least some portion of probe wire <NUM> (e.g., probe distal portion <NUM> (<FIG>)) to pass therethrough. Inner member channel <NUM> may substantially extend from a distal end <NUM> of inner member <NUM> ("inner member distal end <NUM>"). In examples, inner member channel <NUM> substantially surrounds at least some portion of longitudinal axis L. Inner member channel <NUM> may be configured to allow slidable translation of at least probe distal portion <NUM> and probe electrode <NUM> through inner member channel <NUM>, such that probe distal portion <NUM> and probe electrode <NUM> may laterally translate as a result of a pushing force (e.g., in the distal direction D) or a pulling force (e.g., in the proximal direction P) applied to probe wire <NUM>. In an example, inner member channel <NUM> opens to inner lumen <NUM> at inner member distal end <NUM>, such that at least probe distal portion <NUM> and probe electrode <NUM> may pass from inner member channel <NUM> into inner lumen <NUM> of dilator <NUM>.

Inner member <NUM> may be mechanically connected to dilator <NUM> in any manner which establishes a rotational coupling between inner member <NUM> and dilator <NUM>. For example, inner member distal end <NUM> may be attached to dilator proximal end <NUM> by welding, soldering, adhesives, pins, or some other suitable fastening method. In some examples, inner member <NUM> is a torque coil having the form of a helix substantially surrounding a helix interior, and inner member <NUM> is configured such that, when inner member <NUM> is rotationally coupled to dilator <NUM>, longitudinal axis L passes through at least some portion of the helix interior. Inner member <NUM> may define a helix substantially symmetric around some portion of longitudinal axis L. In some examples, the helix interior defines at least part of inner member channel <NUM>.

In examples, implantable medical lead <NUM> includes a conductor (not shown) electrically connected to dilator electrode <NUM>. In some examples, the conductor extends at least partially through inner member channel <NUM>. In other examples, inner member <NUM> includes the conductor. For example, inner member <NUM> be an insulated, coiled conductor electrically connected to dilator electrode <NUM> and configured to transmit a torque to dilator <NUM>. The insulated, coiled conductor may include one or more portions configured to translate (e.g., substantially parallel to longitudinal axis L) relative to lead interior surface <NUM>. For example, some portion of the insulated, coiled conductor (e.g., point P2 (<FIG>)) may be configured to stretch as dilator <NUM> axially translates in the distal direction D. The conductor of implantable medical lead <NUM> may be electrically connected to processing circuitry (e.g., IMD <NUM>) configured to deliver electrical therapy and/or conduct electrical sensing via dilator electrode <NUM>. IMD <NUM> may be configured to provide electrical signals, e.g., pacing therapy, through the conductor to dilator electrode <NUM>, distal electrode <NUM>, and/or return electrode <NUM>, and receive electrical signals, e.g., sensed cardiac electrical signals, through the conductor from dilator electrode <NUM>, distal electrode <NUM>, and/or return electrode <NUM>. In some examples, the conductor is configured to rotate when inner member <NUM> rotates. In other examples, the conductor is configured such that inner member <NUM> rotates relative to the conductor.

As discussed, inner member <NUM> is depicted in <FIG> as a longitudinal cross-section with a cutting plane parallel to the page. Inner member <NUM> may have any longitudinal cross-section sufficient to generate the rotational coupling with dilator <NUM>. Further, inner member <NUM> may have any axial cross-section (e.g., a cross-section perpendicular to the longitudinal cross-section) sufficient to generate the rotational coupling with dilator <NUM>. The axial cross-section may be circular, oval shaped, polygonal, and may include straight and curved segments. The axial cross-section may be substantially solid over substantially all or a portion of the axial cross-section, and may define open areas (e.g., a cross-section of inner member channel <NUM>) over a portion of the axial cross-section.

As depicted in <FIG>, implantable medical lead <NUM> includes one or more tines such as tine <NUM> attached to lead distal end <NUM> of lead body <NUM>. Tine <NUM> is configured to penetrate tissues (e.g., tissue <NUM> (<FIG>, <FIG>, <FIG>)) when lead distal end <NUM> is in contact with or substantially adjacent to a tissue wall (e.g., tissue wall <NUM> (<FIG>, <FIG>, <FIG>)). In examples, tine <NUM> is an elongated member including fixed end <NUM> attached to lead body <NUM> and free end opposite fixed end <NUM>. Tine <NUM> may be resiliently biased such that, unless sufficiently constrained (e.g., by delivery catheter <NUM> (<FIG>, <FIG>)), tine <NUM> tends to assume a position where free end <NUM> has a greater radial displacement from longitudinal axis L than fixed end <NUM>. In an example, the resilient biasing of tine <NUM> results in a tendency of free end <NUM> to return or attempt to return to an initial position relative to a point P on lead interior surface <NUM> when free end <NUM> is displaced from the initial position by, for example, a force F1 or force F2 acting on free end <NUM> in the direction shown in <FIG>. The biasing tending to drive free end <NUM> radially outward when tine <NUM> is unconstrained may cause tine <NUM> to more securely anchor to the tissue of a patient. The one or more tines further include tine <NUM>, which may be configured similarly to tine <NUM>.

In some examples, the one or more tines is a plurality of tines with each tine including a fixed end attached to lead body <NUM> and including a free end opposite the fixed end. For example, <FIG> illustrates and end view of implantable medical lead <NUM> with a plurality of tines <NUM> including tine <NUM>, tine <NUM>, and tine <NUM>. Dilator <NUM>, inner lumen opening <NUM>, and longitudinal axis L are additionally depicted for reference. Dilator axis D (not shown) may be substantially coincident with longitudinal axis L. Tine <NUM> includes fixed end <NUM> attached to lead body <NUM> and free end <NUM> opposite fixed end <NUM>. Tine <NUM> includes fixed end <NUM> attached to lead body <NUM> and free end <NUM> opposite fixed end <NUM>. Free ends <NUM>, <NUM>, <NUM> are depicted in hidden lines. Each of fixed ends <NUM>, <NUM>, and <NUM> are attached to lead body <NUM> substantially at or adjacent to lumen opening <NUM> at lead body distal end <NUM>. As illustrated, in examples, the one or more tines <NUM>, <NUM>, <NUM> may be configured such that a plurality of fixed ends <NUM>, <NUM>, <NUM> substantially surround lumen opening <NUM>.

Individual tines within plurality of tines <NUM> may be spaced apart from each other around lumen opening <NUM>. For example, <FIG> illustrates tines <NUM> and tine <NUM> spaced apart from each other by a distance d1. Distance d1 may expressed as a linear distance over a line oriented perpendicular to longitudinal axis L, and may be between any portion of tine <NUM> and any portion of tine <NUM> (e.g., may be between fixed end <NUM> and fixed end <NUM>, between free end <NUM> and free and <NUM>, or between other portions of tine <NUM> and tine <NUM>). The distance d1 may also be expressed as an angle having a vertex on longitudinal axis L. In some examples, distance d1 may be in the range of <NUM> to <NUM> degrees. The illustrated number and arrangement of plurality of tines <NUM> is one nonlimiting example, and implantable medical lead <NUM> may, in other examples, include a different number of individual tines comprising plurality of tines <NUM> and/or a different positions of one or more individual tines comprising plurality of tines <NUM>. In an example, implantable medical lead <NUM> may include a plurality of tines <NUM> substantially equally distributed circumferentially around lumen opening <NUM>.

One or more of tines <NUM>, <NUM>, <NUM> may be a substantially elastic member (e.g., may tend to return to a zero-stress shape in the absence of externally imparted forces), and may be configured to pierce and potentially penetrate into or through target tissue. One or more of tines <NUM>, <NUM>, <NUM> may be formed to have a preset shape and may be formed using any suitable material. In examples, one or more of tines <NUM>, <NUM>, <NUM> comprise a nickel-titanium alloy such as Nitinol.

Distal electrode <NUM>, return electrode <NUM>, dilator electrode <NUM>, and/or probe electrode <NUM> may be configured to deliver low-voltage electrical pulses to the heart or may sense a cardiac electrical activity, e.g., depolarization and repolarization of the heart. Distal electrode <NUM>, return electrode <NUM>, dilator electrode <NUM>, and/or probe electrode <NUM> may be any of a number of different types of electrodes, including ring electrodes, short coil electrodes, paddle electrodes, hemispherical electrodes, directional electrodes, or the like. Distal electrode <NUM>, return electrode <NUM>, dilator electrode <NUM>, and/or probe electrode <NUM> may be the same or different types of electrodes. Each of distal electrode <NUM>, return electrode <NUM>, dilator electrode <NUM>, and/or probe electrode <NUM> may be electrically isolated from any other of the distal electrode <NUM>, return electrode <NUM>, dilator electrode <NUM>, and/or probe electrode <NUM> by an electrically insulating material between each electrode and any other electrode. Each of distal electrode <NUM>, return electrode <NUM>, dilator electrode <NUM>, and/or probe electrode <NUM> may have its own separate conductor such that a voltage may be applied to or a signal sensed from the each electrode independently from the any other electrode. In some configurations, distal electrode <NUM>, return electrode <NUM>, dilator electrode <NUM>, and/or probe electrode <NUM> may be coupled to a common conductor such that each electrode may apply a voltage simultaneously.

<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 distal electrode <NUM>, return electrode <NUM>, and/or dilator electrode <NUM>, <NUM>, <NUM> (<FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <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 be 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.

A technique for inserting a dilator <NUM> into the tissue at or near a target site <NUM> is illustrated in <FIG>. Although the technique is described mainly with reference to implantable medical lead <NUM> of <FIG>, <FIG>, <FIG>, and <FIG>, the technique may be applied to other implantable medical leads in other examples.

The technique includes navigating a lead body <NUM> to the target site <NUM> in a patient <NUM> (<FIG>) (<NUM>). Target site <NUM> may be location on a septal wall, such as an interventricular septal wall of a right ventricle (RV) of heart <NUM> (<FIG>). The technique may include navigating a delivery catheter <NUM> to target site <NUM>, and navigating a probe wire <NUM> to target site <NUM> using delivery catheter <NUM>. The technique may include translating probe wire <NUM> and a probe electrode <NUM> through an inner lumen <NUM> and inner lumen opening <NUM> at a dilator distal end <NUM> of a dilator <NUM> within lead body <NUM>. Probe wire <NUM> may penetrate a tissue wall <NUM> of tissue <NUM>. The technique may include varying a penetration depth of probe wire <NUM> in tissues <NUM> to vary a location of a probe electrode <NUM> in tissue <NUM>. The technique may include repositioning delivery catheter <NUM> to vary a penetration trajectory of probe wire <NUM>. The technique may include delivering electrical therapy and/or conducting electrical sensing via probe electrode <NUM> (e.g., pace mapping) using processing circuitry in electrical communication with probe electrode <NUM>.

The technique may include extending probe wire <NUM> and probe electrode <NUM> through tissue wall <NUM> and allowing at least a probe distal portion <NUM> to form a curvature such as loop <NUM>. The technique may include forming loop <NUM> after pace mapping using probe electrode <NUM>. Probe distal portion <NUM> may form the curvature such that loop <NUM> is in contact with or substantially adjacent to a tissue wall of tissue <NUM> opposite tissue wall <NUM>. For example, probe distal portion <NUM> may form loop <NUM> in contact with or substantially adjacent to an endocardial surface of the interventricular septal wall of a left ventricle (LV) of heart <NUM> (<FIG>). In examples, the technique includes imaging probe distal portion <NUM> using fluoroscopy or other imaging techniques.

The technique may include navigating lead body <NUM> over probe wire <NUM> to target site <NUM>. Lead body <NUM> may be navigated to target site <NUM> within delivery catheter <NUM>. Delivery catheter <NUM> may constrain one or more tines <NUM>, <NUM>, <NUM> extending from lead body <NUM> in a delivery configuration. The technique includes contacting the one or more tines <NUM>, <NUM>, <NUM> with tissue wall <NUM> at target site <NUM>. Contacting the one or more tines <NUM>, <NUM>, <NUM> may include translating lead body <NUM> within delivery catheter <NUM> toward tissue wall <NUM>. The technique includes grasping tissue wall <NUM> using one or more of tines <NUM>, <NUM>, <NUM>. In examples, tines <NUM>, <NUM>, <NUM> are resiliently biased to expand radially outward from a longitudinal axis L of lead body <NUM> unless a free end <NUM>, <NUM>, <NUM> is constrained (e.g., by delivery catheter <NUM>). Grasping the tissue wall may include withdrawing delivery catheter <NUM> and causing free end <NUM>, <NUM>, <NUM> to expand radially outward. The technique may include positioning a distal electrode <NUM> in close proximity or contact with tissue wall <NUM>. The technique may include delivering electrical therapy and/or conducting electrical sensing via distal electrode <NUM> using processing circuitry (e.g., IMD <NUM> (<FIG>)) in electrical communication with distal electrode <NUM>.

The technique includes rotating dilator <NUM> within a lead body lumen <NUM> defined by a lead interior surface <NUM> of lead body <NUM> (<NUM>). In examples, the technique includes translating dilator <NUM> within lead body lumen <NUM> toward tissue wall <NUM>. The technique may include rotating dilator <NUM> around a dilator axis D (<FIG>). Rotating dilator <NUM> includes rotating an inner member <NUM> relative to lead interior surface <NUM> and causing a rotation of dilator <NUM> relative to lead interior surface <NUM>. The technique includes translating dilator <NUM> into tissues <NUM> using the rotation of inner member <NUM>. In examples, the technique includes engaging tissue wall <NUM> and/or tissue <NUM> with a set of helical threads <NUM> on a dilator exterior surface <NUM> of dilator <NUM> and converting the rotation of dilator <NUM> into a translation of dilator <NUM> substantially parallel to dilator axis D. In examples, the technique includes positioning a dilator electrode <NUM> within tissues <NUM> using the rotation of dilator <NUM>. Positioning dilator electrode <NUM> may include placing dilator electrode <NUM> in electrical contact with tissues <NUM>. The technique may include delivering electrical therapy and/or conducting electrical sensing via dilator electrode <NUM> using processing circuitry (e.g., IMD <NUM> (<FIG>)) in electrical communication with dilator electrode <NUM>.

The technique may include causing inner member <NUM> to stretch longitudinally as dilator <NUM> translates into tissues <NUM>. Stretching inner member <NUM> may include increasing a displacement along longitudinal axis L between a first point P1 on inner member <NUM> and a second point P2 on inner member <NUM>. Some portion of or substantially all of inner member <NUM> may be a helical coil substantially surrounding longitudinal axis L, and stretching inner member <NUM> may include causing the helical coil to stretch lengthwise along the longitudinal axis. The technique may include measuring electrical parameters while translating dilator <NUM> into tissue <NUM> and positioning dilator <NUM> within tissues <NUM> based on the pace mapping conducted using probe wire <NUM> and a probe electrode <NUM>.

The technique may include withdrawing probe distal portion <NUM> from tissue wall <NUM>. Withdrawing probe distal portion <NUM> may include withdrawing probe wire <NUM> proximally through inner lumen opening <NUM> and inner lumen <NUM> of dilator <NUM>. Withdrawing probe wire <NUM> may include withdrawing probe wire <NUM> proximally through an inner member channel <NUM> defined by inner member <NUM>.

The technique may include delivering electrical therapy and/or conducting electrical sensing via dilator electrode <NUM>, distal electrode <NUM>, and or return electrode <NUM> using processing circuitry (e.g., IMD <NUM> (<FIG>)) in electrical communication with at least dilator electrode <NUM> and distal electrode <NUM>. Implantable medical lead <NUM> may be configured to deliver a first electrical signal via dilator electrode <NUM> and a second electrical signal via distal electrode <NUM> using the processing circuitry (e.g., IMD <NUM>). The technique may include using dilator electrode <NUM> to deliver electrical therapy to and/or conduct electrical sensing of tissue <NUM> and using distal electrode <NUM> to deliver electrical therapy to and/or conduct electrical sensing of tissue wall <NUM>. For example, the technique may include using dilator electrode <NUM> to deliver electrical therapy to and/or conduct electrical sensing of a interventricular septum of heart <NUM> (<FIG>) to activate a left bundle branch (LBB) of heart <NUM> and using distal electrode <NUM> to deliver electrical therapy to and/or conduct electrical sensing of an interventricular septal wall of a right ventricle (RV) of heart <NUM> to activate a right bundle branch (RBB) of heart <NUM>.

Claim 1:
An implantable medical lead comprising:
a lead body (<NUM>) comprising an interior surface (<NUM>) defining a lumen (<NUM>), wherein the lead body defines a longitudinal axis (L);
an inner member (<NUM>) within the lumen, wherein the inner member is configured to rotate about the longitudinal axis and rotate relative to the interior surface;
a dilator (<NUM>) coupled to the inner member, wherein:
the dilator is configured to rotate relative to the interior surface,
the inner member is configured to transmit a torque to the dilator when the inner member rotates around the longitudinal axis,
the dilator is configured to penetrate tissue when the dilator receives the torque and the dilator contacts the tissue, and
the dilator includes a dilator electrode (<NUM>) configured to provide stimulation to the tissue when the dilator penetrates the tissue; and
a fixation member (<NUM>) attached to a distal end (<NUM>) of the lead body, wherein the fixation member is configured to secure the distal end of the lead body to the tissue.