Patent Description:
<CIT> relates to systems and methods for threating cardiac arrythmias. <CIT> relates to papillary muscle stimulation.

In one illustrative implantable medical device, the device includes a plurality of electrodes. The plurality of electrodes may include a right atrial electrode positionable within the right atrium to deliver cardiac therapy to or sense electrical activity of the right atrium of the patient's heart and at least one left ventricular electrode positionable proximate the left ventricle of the patient's heart. The device may further include a housing extending from a proximal end region to a distal end region and the right atrial electrode may be leadlessly coupled to the proximal end region. The device may further include a leadlet extending from a proximal region to a distal region, where the proximal region is coupled to the distal end region of the housing and the at least one ventricular electrode is coupled to the distal region of the leadlet. Further, the leadlet may be configured to extend through the coronary sinus ostium and into the coronary sinus or a coronary vein of the patient's heart to position the least one left ventricular electrode proximate the left ventricle of the patient's heart. The device may further include a therapy delivery circuit within the housing and operably coupled to the plurality of electrodes to deliver cardiac therapy to the patient's heart and a sensing circuit within the housing and operably coupled to the plurality of electrodes to sense electrical activity of the patient's heart. The device may further include a controller within the housing and comprising processing circuitry operably coupled to the therapy delivery circuit and the sensing circuit. The controller may be configured to monitor electrical activity using the processing circuitry and one or more of the plurality of electrodes and delivering pacing therapy using the processing circuitry and one or more of the plurality of electrodes.

In one illustrative method, the method may include implanting a right atrial electrode in the right atrial endocardium or in the right atrial myocardium of a patient's heart, the right atrial electrode being leadlessly coupled to a proximal end region of an implantable housing. The method may further include implanting at least one left ventricular electrode through the coronary sinus ostium and into the coronary sinus or a coronary vein of the patient's heart, where the at least one left ventricular electrode being coupled to a distal region of a leadlet and a proximal region of the leadlet being coupled to a distal end region of the implantable housing. Processing circuitry may be located, positioned, or disposed, in the housing and operably coupled to the right atrial electrode and the at least one left ventricular electrode. The method may further include monitoring electrical activity using the processing circuitry and one or more of the right atrial electrode and the at least one left ventricular electrode and delivering pacing therapy using the processing circuitry and at one or more of the right atrial electrode and the at least one left ventricular electrode.

In one illustrative method, the method may include delivering a delivery catheter and a penetration element located, positioned, or disposed, in the delivery catheter to the right ventricular endocardium of the interventricular septal wall of a patient's heart, puncturing the right ventricular endocardium using the penetration element to form an opening through the right ventricular endocardium and into the interventricular septal wall, and retracting the penetration element. The method may further include advancing a distal portion of a guide element through the delivery catheter and the opening and into the interventricular septal wall to extend along the left ventricular endocardial wall and delivering a distal portion of an implantable medical lead over the guide element to the left ventricular myocardium to extend along the left ventricular endocardial wall to position at least one left ventricular electrode on the distal portion in the left ventricular myocardium.

In one illustrative system for delivering an implantable medical lead into the interventricular septal wall and proximate the left ventricular myocardium, the system may include a delivery catheter extending from a proximal end region to a distal end region, where the distal end region positionable adjacent to the right ventricular endocardium of the interventricular septal wall of a patient's heart. The system may further include a penetration element locatable, positionable, or disposable, in the delivery catheter to form an opening through the right ventricular endocardium and into the interventricular septal wall and a guide element extending from a proximal end region to a distal end region. The guide element may be locatable, positionable, or disposable, in the delivery catheter to enter the interventricular septal wall through the opening and to extend along the left ventricular endocardial wall.

The above summary is not intended to describe each embodiment or every implementation of the present disclosure. A more complete understanding will become apparent and appreciated by referring to the following detailed description and claims taken in conjunction with the accompanying drawings. In other words, these and various other features and advantages will be apparent from a reading of the following detailed description.

The present disclosure makes reference to a leadless implantable medical device (LIMD). Examples LIMDs having a leadlet that may be used are described in <CIT>.

The present disclosure also makes reference to the triangle of Koch region. Examples of uses of the triangle of Koch region are described <CIT>.

In general, any suitable type of IMD (or LIMD) including a lead or leadlet may be used. Non-limiting examples of suitable IMDs include an implantable transvenous pacemaker, a transvenous cardiac resynchronization therapy (CRT) device, a transvenous CRT pacemaker (CRT-P), a transvenous CRT defibrillator (CRT-D), an implantable transvenous cardioverter defibrillator (ICD), a subcutaneous ICD (S-ICD), and a subcutaneous medical device.

One example of a LIMD <NUM> positioned in the right atrium (RA) of a patient's heart <NUM> including a leadlet <NUM> positioned in the RA of the patient's heart <NUM> is depicted in <FIG>. The LIMD <NUM> may include a housing <NUM> extending from a distal end region <NUM> to a proximal end region <NUM>. The leadlet <NUM> may be physically and operably coupled to the proximal end region <NUM> of the housing <NUM> of LIMD <NUM>.

The LIMD <NUM> may be used to sense electrical activity of the patient's heart or to deliver cardiac therapy to the patient's heart. In general, a first electrode <NUM> operably and physically coupled to the leadlet <NUM> may be implanted in the RA endocardium or myocardium. And, a second electrode <NUM> may be operably and physically coupled to a fixation element <NUM> extending from the distal end region <NUM> of the LIMD <NUM> and may be implanted in the left ventricular (LV) myocardium. More specifically, the second electrode <NUM> may be coupled to a distal end region <NUM> of an implantable housing <NUM> of the LIMD <NUM>, such as disposed on a fixation element <NUM> (e.g., helical or screw-like structure) extending away from the housing <NUM> of the LIMD <NUM> to facilitate fixation. The first electrode <NUM> may be coupled to a leadlet <NUM> extending from a proximal end region <NUM> of the housing <NUM> of the LIMD <NUM>. The LIMD <NUM> may be described as a ventricular LIMD implanted in the atrium that paces the ventricle that also includes a leadlet, or "pig tail," that paces the atrium.

The LIMD <NUM> may be used in any suitable manner. In some embodiments, a method of using the LIMD <NUM> may include implanting the first, or right atrial, electrode <NUM> on the right atrial endocardium or in the right atrial myocardium of the patient's heart <NUM>. It may be described that the leadlet <NUM> extends from a distal end, or first portion, to a proximal end, or second portion. The first, or right atrial, electrode <NUM> may be coupled to the distal end, or first portion, of the leadlet <NUM>. The proximal end, or second portion, of the leadlet <NUM> may be coupled to the proximal end region <NUM> of the housing <NUM> of the LIMD <NUM>. Processing circuitry <NUM> may be disposed in the housing <NUM> and operably coupled to the electrodes <NUM>, <NUM>.

An illustrative method may include implanting a left ventricular electrode through or proximate to the triangle of Koch region of the right atrium, such as in the coronary sinus (CS) ostium, through the right atrial endocardium, and through central fibrous body and into the basal, septal, or basal-septal region in the left ventricular myocardium of the patient's heart. The left ventricular electrode may be leadlessly coupled to a distal portion of the implantable housing. The processing circuitry may be operably coupled to the left ventricular electrode. The method may further include monitoring electrical activity using the processing circuitry and at least one of the right atrial electrode and the left ventricular electrode. Further, the method may include delivering pacing therapy using the processing circuitry and at least one of the right atrial electrode and the left ventricular electrode.

In another embodiment, an LIMD similar to the LIMD <NUM> of <FIG> may be utilized in a different configuration or method. For example, the LIMD may include a right atrial electrode for implantation on the right atrial endocardium or in the right atrial myocardium of the patient's heart, and the right atrial electrode may be leadlessly coupled to a distal end region, or distal portion, of an implantable housing of the LIMD. Further, a left ventricular electrode may be implanted through or proximate to the triangle of Koch region of the right atrium, such as in the CS ostium, through the right atrial endocardium, and through central fibrous body and into the basal, septal, or basal-septal region in the left ventricular myocardium of the patient's heart. The left ventricular electrode may be coupled to a distal end region, or a first portion, of a leadlet. A proximal end region, or a second portion, of the leadlet may be coupled to a proximal end region, or proximal portion, of the implantable housing of the LIMD. The processing circuitry located in the housing may be operably coupled to both of the right and the left ventricular electrode. The LIMD may monitor electrical activity using the processing circuitry and at least one of the right atrial electrode and the left ventricular electrode. Further, the LIMD may deliver pacing therapy using the processing circuitry and at least one of the right atrial electrode and the left ventricular electrode.

An illustrative LIMD <NUM> including a deployable leadlet is depicted in <FIG>. The LIMD <NUM> may include one or more fixation elements (although not shown), a deployable leadlet <NUM>, a first electrode <NUM>, and a second electrode <NUM> coupled to the leadlet <NUM>. The leadlet <NUM> extends from a proximal end region <NUM> to a distal end region <NUM>, and the second electrode is located proximate (or within) the distal end region <NUM>.

The LIMD <NUM> may include a body portion <NUM> and a sheath portion <NUM> moveable with respect to the body portion <NUM>. The sheath portion <NUM> may define an opening or aperture within which the body portion <NUM> is located. The LIMD <NUM> may define a stowed configuration or position as shown in <FIG> and a deployed configuration as shown in <FIG>. When in the stowed configuration, the body portion <NUM> may be located substantially completely within the opening of the sheath portion <NUM> such that, e.g., the deployable leadlet <NUM> is also in a stowed configuration where the leadlet <NUM> does not extend beyond or outside of the sheath portion <NUM>. More specifically, when in the stowed configuration, the leadlet <NUM> may reside within a recess, or groove, <NUM>. The leadlet <NUM> may include (e.g., be formed of) resilient materials such that, e.g., when the sheath portion <NUM> is retracted <NUM> away exposed a distal end region <NUM> of the body portion <NUM>, the leadlet <NUM> may move <NUM> away from (e.g., pivot or partially rotate away from) the body portion <NUM> in at least partially radial manner to position the distal end region <NUM>, and consequently, the second electrode <NUM>, of the leadlet <NUM>, away from the body portion <NUM>.

Although not shown in <FIG>, one or more fixation elements may be disposed on the distal end region <NUM> of the body portion <NUM> of the LIMD <NUM> and extend distally from the body portion <NUM>. The one or more fixation elements may be electrically active or passive. The first electrode <NUM> may be positioned on the distal end region <NUM> of the body portion <NUM> of the LIMD <NUM> to engage the endocardial wall of the patient's heart. The second electrode <NUM> may be coupled to the leadlet <NUM> extending at least partially in a radial direction away from the body portion <NUM> in a deployed position. As described herein, the body portion <NUM> may define, or include, a recess <NUM> to at least partially receive the leadlet <NUM> in the stowed position. In other words, it may be described that the body portion <NUM> may be delivered in a "cup" (e.g., defined by the sheath portion <NUM>) and protracted to deploy the body portion <NUM> for implantation. In some embodiments, the endocardial wall is the right atrial endocardial wall. Additionally, as can be seen in <FIG>, the leadlet <NUM> may described as defining a shape have two sections or portions. The first section, which is closest to the proximal end region <NUM>, may extend tangentially and in a straight line away from the outside (e.g., circumference) of the body portion <NUM>. The second section, which is closer to the distal end region <NUM>, may then curve or bend away from the tangentially straight line defined by the first section back towards a path somewhat or partially parallel to the outside (e.g., circumference) of the body portion <NUM>.

An illustrative LIMD <NUM> including a deployable leadlet <NUM> is depicted in <FIG>. The LIMD <NUM> may include one or more fixation elements <NUM> (e.g., curved tines), a deployable leadlet <NUM>, a first electrode <NUM>, and a second electrode <NUM> coupled to the leadlet <NUM>. The leadlet <NUM> extends from a proximal end region <NUM> to a distal end region <NUM>, and the second electrode <NUM> is located proximate (or within) the distal end region <NUM>.

The LIMD <NUM> may include a body portion <NUM> and a sheath portion <NUM> moveable with respect to the body portion <NUM>. The sheath portion <NUM> may define an opening or aperture within which the body portion <NUM> is located. The LIMD <NUM> may define a stowed configuration or position when the body portion <NUM> is substantially completely within the opening of the sheath portion <NUM> such that, e.g., the deployable leadlet <NUM> is also in a stowed configuration or position where the leadlet <NUM> does not extend beyond or outside of the sheath portion <NUM>. The LIMD <NUM> may further define a deployed configuration as shown in <FIG>. More specifically, when in the stowed configuration, the leadlet <NUM> may reside within a recess or groove. The leadlet <NUM> may include (e.g., be formed of) resilient materials such that, e.g., when the sheath portion <NUM> is retracted <NUM> away exposed a distal end region <NUM> of the body portion <NUM>, the leadlet <NUM> may move <NUM> (e.g., pivot or partially rotate) away from the body portion <NUM> in at least partially radial manner to position the distal end region <NUM>, and consequently, the second electrode <NUM>, of the leadlet <NUM>, away from the body portion <NUM>.

One or more fixation elements <NUM> may be disposed on the distal end region <NUM> of the body portion <NUM> of the LIMD <NUM> and extend distally from the body portion <NUM>. The one or more fixation elements <NUM> may be electrically active or passive. The first electrode <NUM> may be positioned on the distal end region <NUM> of the body portion <NUM> of the LIMD <NUM> to engage the endocardial wall of the patient's heart. The second electrode <NUM> may be coupled to the leadlet <NUM> extending at least partially in a radial direction away from the body portion <NUM> in a deployed position as shown. As described herein, the body portion <NUM> may define, or include, a recess to at least partially receive the leadlet <NUM> in the stowed position. In other words, it may be described that the body portion <NUM> may be delivered in a "cup" (e.g., defined by the sheath portion <NUM>) and protracted to deploy the body portion <NUM> for implantation. In some embodiments, the endocardial wall is the right atrial endocardial wall.

Another illustrative LIMD <NUM> including a deployable leadlet <NUM> is depicted in <FIG>. The LIMD <NUM> may be substantially similar to the LIMD <NUM> except for the movement of the leadlet <NUM>. As shown, the leadlet <NUM> of LIMD <NUM> swings, or rotates, away from the body portion <NUM> in an opposite direction than the leadlet <NUM> of LIMD <NUM> to, e.g., provide ease of re-sheathing the body portion <NUM> into the sheath portion <NUM>. More specifically, the sheath portion <NUM> may contact and "fold down" the leadlet <NUM> when the body portion <NUM> is moved with respect to the sheath portion <NUM> of the LIMD <NUM> to position the body portion <NUM> within the aperture or opening of the sheath portion <NUM> (i.e., the body portion <NUM> being retracted into the sheath portion <NUM>). In other words, the LIMD <NUM> may be provide "easy" retraction of the body portion <NUM> within the sheath portion <NUM>.

The LIMDs <NUM>, <NUM>, <NUM> may be used in any suitable manner. In some embodiments, a method of using the LIMDs <NUM>, <NUM>, <NUM> may include attaching one or more fixation elements <NUM> thereof to the endocardial wall of the patient's heart. The fixation elements <NUM> may be coupled to the distal end region, or distal portion, <NUM>, <NUM> of the body portion <NUM>, <NUM>. Processing circuitry <NUM> may be disposed in the body portion <NUM>, <NUM>. The method of using the LIMDs <NUM>, <NUM>, <NUM> may also include implanting the first electrode <NUM>, <NUM> to engage the endocardial wall of the patient's heart when the fixation element is attached. The first electrode <NUM>, <NUM> may be leadlessly coupled to the distal end region, or distal portion, <NUM>, <NUM> of the body portion <NUM>, <NUM>. The processing circuitry <NUM> may be operably coupled to each of the first and second electrodes <NUM>, <NUM>, <NUM>, <NUM>.

The method of using the LIMDs <NUM>, <NUM>, <NUM> may further include implanting the second electrode <NUM>, <NUM> to engage the endocardial wall of the patient's heart when the LIMD <NUM>, <NUM>, <NUM> is in the deployed configuration placing the leadlet <NUM>, <NUM> in the deployed position. More specifically, it may be described that the second electrode <NUM>, <NUM> is coupled to the distal end region, or a first portion, <NUM>, <NUM> of the leadlet <NUM>, <NUM> and the proximal end region, or a second portion, <NUM>, <NUM> of the leadlet <NUM>, <NUM> may be coupled to the distal end region <NUM>, <NUM> of the body portion <NUM>, <NUM>. As described herein, the leadlet <NUM>, <NUM> may extend at least partially in a radial direction away from the body portion <NUM>, <NUM> in the deployed configuration/position so as to, e.g., engage cardiac tissue with the second electrode <NUM>, <NUM>.

The method of using the LIMDs <NUM>, <NUM>, <NUM> may further include monitoring electrical activity using the processing circuitry <NUM> and at least one of the first electrode <NUM>, <NUM> and the second electrode <NUM>, <NUM>. Further, the method of using the LIMDs <NUM>, <NUM>, <NUM> may further include delivering pacing therapy using the processing circuitry <NUM> and at least one of the first electrode <NUM>, <NUM> and the second electrode <NUM>, <NUM>.

Although no fixation element is depicted on the LIMD <NUM> in <FIG> and tines <NUM> are depicted on the LIMD <NUM> of <FIG>, it is to be understood that any suitable fixation element may be used. In some embodiments, the fixation elements may include one or more helix structures or screw-like structures. In some embodiments, the fixation elements may include one or more adhesives (which may be used in conjunction with other fixation elements such as a helix structure).

A conceptual diagram of an LIMD <NUM> positioned in the right atrium of a patient's heart including a leadlet <NUM> extending through the coronary sinus (CS) ostium of the patient's heart is depicted in <FIG>. The LIMD <NUM> may include an implantable housing <NUM> extending from a proximal end region <NUM> to a distal end region <NUM>. The LIMD <NUM> may include a plurality of electrodes. The plurality of electrodes may include one or more right atrial electrodes configured to sense and/or pace right atrial tissue and one or more left ventricular electrodes configured to sense and/or pace left ventricular tissue. For example, as shown, the LIMD <NUM> includes a right atrial electrode <NUM> positioned on the proximal end region <NUM> of the implantable housing <NUM> of the LIMD <NUM>. The right atrial electrode <NUM> may be implanted in the right atrial endocardium or in the right atrial myocardium of the patient's heart. In some embodiments, the right atrial electrode <NUM> may be positioned proximate to (e.g., in contact with, adjacent, partially within, within, etc.) the right atrial appendage.

The LIMD <NUM> in <FIG> also includes a pair of left ventricular electrodes <NUM> coupled to the leadlet <NUM> extending distally from the housing <NUM>. The leadlet <NUM> may be described as extending from a proximal region <NUM> to a distal region <NUM>. The proximal region <NUM> is coupled to the distal end region <NUM> of the housing <NUM>. The electrodes <NUM> are positioned on or proximate the distal region <NUM> of the leadlet <NUM>. When implanted, the leadlet <NUM> may extend through the coronary sinus ostium and into the coronary sinus or a coronary vein of the patient's heart to position the left ventricular electrodes <NUM> proximate the left ventricle of the patient's heart. Thus, in some embodiments, the left ventricular electrodes <NUM> may be implanted in the coronary sinus or a coronary vein, and in other embodiments, the left ventricular electrodes may be implanted in the left ventricular myocardium of the patient's heart, for example, using a helical structure or screw-like structure. In the embodiment depicted in <FIG>, it may be described that a plurality of left ventricular electrodes <NUM> are coupled to the leadlet <NUM>, for example, including an anode and a cathode. In some embodiments, the plurality of left ventricular electrodes <NUM> may be used for field steering, for example, to avoid capture of the left atrium (LA) of the patient's heart.

The LIMD <NUM> may be described as being implanted in the atrium to sense or pace the atrium. The leadlet <NUM>, which may be advanced a relatively long way down the coronary sinus, anterior interventricular vein (AIV) or great cardiac vein (GCV), or lateral vein, to pace the left ventricle or may be advanced a short way into the coronary sinus and then fixated "down" into left ventricular myocardium to pace the left ventricle. In some embodiments, the leadlets described herein may be quadripolar leadlets including four electrodes. Further, any of the leadlets described herein may also use active fixation, which may allow for adjustment of electrode depth, for example, into the left ventricular myocardium.

The LIMD <NUM> of <FIG> may be used in any suitable manner. In some embodiments, a method of using the LIMD <NUM> may include implanting the right atrial electrode <NUM> on the right atrial endocardium or in the right atrial myocardium of the patient's heart. The right atrial electrode <NUM> may be leadlessly coupled to a proximal end region, or portion, <NUM> of the implantable housing <NUM>. Processing circuitry <NUM> may be disposed in the housing <NUM> and may be operably coupled to the right atrial electrode <NUM>.

The method of using the LIMD <NUM> may also include implanting the left ventricular electrodes <NUM> through the coronary sinus ostium and into the coronary sinus or a coronary vein of the patient's heart. The left ventricular electrodes <NUM> may be coupled to the distal region, or first portion, <NUM> of the leadlet <NUM>. The proximal region, or second portion, <NUM> of the leadlet <NUM> may be coupled to the distal end region <NUM> of the implantable housing <NUM>. The processing circuitry <NUM> may also be operably coupled to the left ventricular electrodes <NUM>.

The method of using the LIMD <NUM> may further include monitoring electrical activity using the processing circuitry <NUM> and at least one of the right atrial electrode <NUM> and the left ventricular electrodes <NUM> and may include delivering pacing therapy using the processing circuitry <NUM> and at least one of the right atrial electrode <NUM> and the left ventricular electrodes <NUM>. In some embodiments, implanting the left ventricular electrodes <NUM> may include implanting the left ventricular electrodes <NUM> into the left ventricular myocardium from the coronary sinus proximal to the posterior vein of the patient's heart. In some embodiments, implanting the left ventricular electrodes <NUM> may include implanting the left ventricular electrodes <NUM> into the anterior interventricular vein (AIV) of the patient's heart. In some embodiments, implanting the left ventricular electrodes <NUM> may include implanting the left ventricular electrodes <NUM> into the lateral vein of the patient's heart. Further, in some embodiments, delivering pacing therapy may include utilizing field steering to avoid left atrial capture by the left ventricular electrodes <NUM>.

Conceptual diagrams showing one example of implantation of an implantable medical device (IMD) <NUM> including an implantable medical lead or leadlet <NUM> extending through the right ventricular (RV) endocardium are depicted in <FIG>. Although a lead is described herein, a leadlet extending from an intracardiac implantable housing of an LIMD may also be used. In other words, the lead <NUM> could be either a lead extending from an IMD located, or positioned, outside of the heart or a leadlet extending from a LIMD located, or positioned, inside of the heart.

The lead <NUM> may extend from a proximal portion coupled to the a control portion of the IMD <NUM> (e.g., a housing, battery, controller, processing circuitry, etc.) to a distal portion <NUM> that is positioned in or proximate the left ventricular myocardium extending along the left ventricular endocardial wall <NUM>, for example, toward the apex of the patient's heart. The distal portion <NUM> may be proximate to the left bundle branch (LBB) of the patient's heart. Although any suitable delivery system may be used to deliver the lead <NUM>, a delivery system and method of implantation using such delivery system are shown and described with respect to <FIG>. Generally, the delivery system may be described as puncturing the right ventricular endocardium <NUM> to allow a lead <NUM> to be simply pushed into the septal myocardium <NUM>, or interventricular septal wall, and tunneled up or down the septum. The lead <NUM> may be tunneled into the basal-septal, mid-septal, or even apical septal region with the septal myocardium <NUM>.

The lead <NUM> may be a multipolar lead such as, e.g., the quadripolar lead <NUM> described herein with respect to <FIG>. More specifically, a distal portion <NUM> of the lead <NUM> may have a quadripolar configuration, which may be the same or similar to an ATTAIN STABILITY™ or ATTAIN STABILITY QUAD™ or ATTAIN PERFORMA™ leads available from Medtronic plc of Dublin, Ireland. A side helix or hook usable for fixation that may be disposed on the distal portion, which may be selectively electrically active or passive and may be mechanically active or adjustable. Another exemplary lead that may be employed is described in <CIT>, in which electrodes are jumpered in a diagonal configuration in order to increase the opportunity to capture cardiac tissue.

A guide element <NUM>, such as a guidewire, a steerable stylet or wire, or a hybrid of stylet guidewire that is a part of the ATTAIN family, may be used to guide <NUM> the lead <NUM> into the septum <NUM>. With multiple electrodes and different spacing, one lead <NUM> may be used to pace the atrium and multiple locations down the septum <NUM>. One example of a guiding element that may be used is described in <CIT>,.

The IMD <NUM> including the lead <NUM> may be used in any suitable manner. In some embodiments, a method of delivering and using the IMD <NUM> may include delivering a delivery catheter <NUM> and a penetration element <NUM> disposed in the delivery catheter <NUM> to the right ventricular endocardium <NUM> of the interventricular septal wall of a patient's heart as shown in <FIG>. The delivery catheter <NUM> may be configured to provide positioning of the distal end <NUM> of the delivery catheter to target implantation location <NUM> such that the distal end <NUM> is positioned adjacent to (e.g., substantially flush or in contact with) the right ventricular endocardium <NUM>. For example, in one embodiment, the delivery catheter <NUM> extends from a proximal portion to a distal portion <NUM>, and the distal portion <NUM> defines a curvature to position the distal end <NUM> of the catheter <NUM> substantially flush to the right ventricular endocardium <NUM>.

The method may include puncturing the right ventricular endocardium <NUM> using the penetration element <NUM> to form an opening through the right ventricular endocardium <NUM> and into the interventricular septal wall <NUM> as shown in <FIG>. The penetration element <NUM> may then be retracted through the delivery catheter <NUM>. Then, a distal portion of a guide element <NUM> may be advanced through the delivery catheter <NUM> and the opening and into the interventricular septal wall <NUM> to extend along the left ventricular endocardial wall <NUM>. The guide element <NUM> may extend from a proximal region to a distal region <NUM> and the distal region <NUM> may be configured to be positioned into the interventricular septal wall <NUM> to extend along the left ventricular endocardial wall <NUM>. In at least one embodiment, the distal region <NUM> may define or include a distal curvature portion that curves when exiting the delivery catheter <NUM> into the interventricular septal wall <NUM> so as to deliver at least a region of a distal portion <NUM> of an implantable medical lead <NUM> substantially parallel to the interventricular septal wall <NUM> in the left ventricular myocardium.

In addition, a distal portion of the implantable medical lead <NUM> of the device <NUM> may be advanced or delivered over the guide element <NUM> to the left ventricular myocardium to extend along the left ventricular endocardial wall <NUM> to position one or more left ventricular electrodes <NUM> on the distal portion in the left ventricular myocardium. In one or more embodiments, the guide element <NUM> does not extend beyond the tip of the lead <NUM>, and instead, may remain a selected distance away from the tip (e.g., about <NUM> centimeter) to allow tip to flex during blunt dissection/tunneling of the lead150. Further, Examples of the guide element <NUM> may include a steerable stylet, shaped stylets, etc. In some embodiments, one or more left ventricular electrodes <NUM> may be positioned proximate to the left bundle branch (LBB) of the conduction system of the patient's heart.

In some embodiments, a right ventricular electrode <NUM> on the lead <NUM> may be positioned/implanted proximate to the right ventricular endocardium <NUM>. The right ventricular electrode <NUM> may be positioned proximal to the left ventricular electrode on the distal portion <NUM> of the implantable medical lead <NUM>.

Further, the method of using IMD <NUM> may include monitoring electrical activity of at least one of the right ventricular electrode <NUM> and one or more of the left ventricular electrodes <NUM>, and delivering pacing therapy using at least one of the right ventricular electrode <NUM> and the left ventricular electrodes <NUM>. In some embodiments, delivering pacing therapy may include delivering pacing pulses to the left ventricular electrodes <NUM> configured to pace the left bundle branch of the conduction system of the patient's heart. In some embodiments, the implantable medical lead <NUM> may include a plurality of left ventricular electrodes, a plurality of right ventricular electrodes, or both.

<FIG> are conceptual diagrams showing one example of an implantable medical device (IMD) <NUM> including an implantable medical lead or leadlet <NUM> extending through the right atrial endocardium. Although a lead <NUM> is described herein, a leadlet extending from an intracardiac implantable housing may also be used. A distal portion <NUM> of the lead <NUM> may be positioned in the left ventricular myocardium extending along the left ventricular endocardial wall, for example, toward the apex of the patient's heart. The distal portion <NUM> may be proximate to the left bundle branch (LBB) of the patient's heart <NUM>. Any suitable delivery system and method may be used to deliver the lead <NUM>. In at least one embodiment, the delivery systems described herein with respect to <FIG> and <FIG> may be utilized. For example, a delivery system may be configured to puncture the right atrial endocardium and central fibrous body (CFB) to allow the lead <NUM> to be simply pushed into the septal myocardium, or interventricular septal wall, and tunneled up or down the septum as shown by the trajectory <NUM> in <FIG>. The lead <NUM> may be tunneled into the basal-septal, mid-septal, or even apical septal region.

A multipolar lead may be used such as, e.g., the quadripolar lead <NUM> described herein with respect to <FIG>. The distal portion <NUM> of the lead <NUM> may have a quadripolar configuration, which may be the same or similar to an ATTAIN STABILITY™ or ATTAIN STABILITY QUAD™ or ATTAIN PERFORMA™ leads available from Medtronic plc of Dublin, Ireland. A side helix or hook usable for fixation that may be disposed on the distal portion, which may be selectively electrically active or passive and may be mechanically active or adjustable. Another exemplary lead that may be employed is described in <CIT>, in which electrodes are jumpered in a diagonal configuration in order to increase the opportunity to capture cardiac tissue.

The guiding element may be a guidewire, a steerable stylet or wire, or a hybrid of stylet guidewire that is a part of the ATTAIN family, may be used to guide the lead into the septum. With multiple electrodes and different spacing, one lead may be used to pace the atrium and multiple locations down the septum. One example of a guiding element that may be used is described in <CIT>.

The IMD <NUM> may be used in any suitable manner. In some embodiments, a method of implanting and using the IMD <NUM> may include delivering the delivery catheter and a penetration element disposed in the delivery catheter to the right atrial endocardium in or proximate to the triangle of Koch region of a patient's heart, such as in the coronary sinus ostium. The method of implanting and using the IMD <NUM> may also include puncturing the right atrial endocardium and the central fibrous body using the penetration element to form an opening through the right ventricular endocardium and the central fibrous body and into the interventricular septal wall. Then, the penetration element may be retracted. Then, a distal portion of a guide element may be advanced through the delivery catheter and the opening and into the interventricular septal wall to extend along the left ventricular endocardial wall.

In addition, the method of implanting and using the IMD <NUM> may include delivering a distal portion <NUM> of an implantable medical lead <NUM> over the guide element to the left ventricular myocardium to extend along the left ventricular endocardial wall to position one or more left ventricular electrodes <NUM> on the distal portion <NUM> in the left ventricular myocardium. In some embodiments, the left ventricular electrodes <NUM> may be positioned proximate to the left bundle branch of the conduction system of the patient's heart. In some embodiments, the method of implanting and using the IMD <NUM> may also include implanting one or more right atrial electrodes <NUM> proximate to the right atrial endocardium. The right atrial electrodes <NUM> may be positioned proximally along the lead <NUM> to the left ventricular electrodes <NUM> on the distal portion <NUM> of the implantable medical lead <NUM>.

In some embodiments, the method of using the IMD <NUM> may further include monitoring electrical activity of at least one of the right atrial electrodes <NUM> and the left ventricular electrodes <NUM>, and delivering pacing therapy using at least one of the right atrial electrodes <NUM> and the left ventricular electrodes <NUM>. In some embodiments, delivering pacing therapy may include delivering pacing pulses to the left ventricular electrodes <NUM> configured to pace the left bundle branch of the conduction system of the patient's heart. Further, In some embodiments, the implantable medical lead may include a plurality of left ventricular electrodes, a plurality of right atrial electrodes, or both.

A conceptual diagram showing one example of a "screw-like" structure that may be used to support and fixate one or more electrodes in myocardial tissue is depicted in <FIG>. In some embodiments, IMD or LIMD may include an elongate member <NUM> extending between a proximal portion and a distal portion <NUM>. A first electrode <NUM> may be disposed on the distal portion <NUM> of the elongate member. A second electrode <NUM> may be disposed proximal to the first electrode <NUM> on the distal portion <NUM> of the elongate member <NUM>. A first threaded bulb region <NUM> may be disposed between the first and second electrodes <NUM>, <NUM> on the distal portion <NUM> of the elongate member <NUM>. A second threaded bulb region <NUM> disposed between the first threaded bulb region <NUM> and the second electrode <NUM> on the distal portion <NUM> of the elongate member <NUM>. In some embodiments, the threaded bulb regions <NUM>, <NUM> may share a similar threaded pattern or spacing.

<FIG> is a block diagram of circuitry that may be enclosed within the housings of an illustrative IMD <NUM> to provide the functions of cardiac therapy described herein with respect to <FIG>. In other words, the IMD <NUM> may be used with any one or more of the embodiments described with respect to <FIG>. The electronic circuitry of the device <NUM> may include software, firmware, and hardware that cooperatively monitor atrial and ventricular electrical cardiac signals, determine when a cardiac therapy is necessary, and/or deliver electrical pulses to the patient's heart according to programmed therapy mode and pulse control parameters. The electronic circuitry may include a control circuit <NUM> (e.g., including processing circuitry), a memory <NUM>, a therapy delivery circuit <NUM>, a sensing circuit <NUM>, and/or a telemetry circuit <NUM>. In some examples, the device <NUM> includes one or more sensors <NUM> for producing a signal that is correlated to a physiological function, state, or condition of the patient, such as a patient activity sensor, for use in determining a need for pacing therapy and/or controlling a pacing rate.

The power source <NUM> may provide power to the circuitry of the device <NUM> including each of the components <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, as needed. The power source <NUM> may include one or more energy storage devices, such as one or more rechargeable or non-rechargeable batteries. The connections between the power source <NUM> and each of the components <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are to be understood from the general block diagram illustrated but are not shown for the sake of clarity. For example, the power source <NUM> may be coupled to one or more charging circuits included in the therapy delivery circuit <NUM> for providing the power needed to charge holding capacitors included in the therapy delivery circuit <NUM> that are discharged at appropriate times under the control of the control circuit <NUM> for delivering pacing pulses, e.g., according to a dual chamber pacing mode such as DDI(R). The power source <NUM> may also be coupled to components of the sensing circuit <NUM>, such as sense amplifiers, analog-to-digital converters, switching circuitry, etc., sensors <NUM>, the telemetry circuit <NUM>, and the memory <NUM> to provide power to the various circuits.

Any suitable technique may be used to recharge a rechargeable power source <NUM>. In some embodiments, the device <NUM> may include an antenna, inductive coils, or other inductive coupling structures configured to couple to another device, such as an external charger or programmer, to receive power in situ. Various examples of charging a leadless implantable medical device are described in <CIT>, entitled "Recharge of Implanted Medical Devices,". The device <NUM> may also be configured to use various techniques to extend the life of the power source <NUM>, such as a low-power mode.

Various examples of power sources and techniques related to power sources may be used, such as those found in, for example, <CIT>, <CIT>, and <CIT>.

The functional blocks shown represent functionality included in the device <NUM> and may include any discrete and/or integrated electronic circuit components that implement analog, and/or digital circuits capable of producing the functions attributed to the device <NUM> herein. The various components may include processing circuitry, such as an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group), and memory that execute one or more software or firmware programs, a combinational logic circuit, state machine, or other suitable components or combinations of components that provide the described functionality. The particular form of software, hardware, and/or firmware employed to implement the functionality disclosed herein will be determined primarily by the particular system architecture employed in the medical device and by the particular detection and therapy delivery methodologies employed by the medical device. Providing software, hardware, and/or firmware to accomplish the described functionality in the context of any modern cardiac medical device system, given the disclosure herein, is within the abilities of one of skill in the art.

The memory <NUM> may include any volatile, non-volatile, magnetic, or electrical non-transitory computer readable storage media, such as random-access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically-erasable programmable ROM (EEPROM), flash memory, or any other memory device. Furthermore, the memory <NUM> may include a non-transitory computer readable media storing instructions that, when executed by one or more processing circuits, cause the control circuit <NUM> and/or other processing circuitry to perform a single, dual, or triple chamber pacing (e.g., single or multiple chamber pacing) function or other sensing and therapy delivery functions attributed to the device <NUM>. The non-transitory computer-readable media storing the instructions may include any of the media listed above.

The control circuit <NUM> may communicate, e.g., via a data bus, with the therapy delivery circuit <NUM> and the sensing circuit <NUM> for sensing cardiac electrical signals and controlling delivery of cardiac electrical stimulation therapies in response to sensed cardiac events, e.g., P-waves and R-waves, or the absence thereof. The electrodes <NUM>, <NUM>, <NUM> (e.g., left ventricular electrodes, right ventricular electrodes, right atrial electrodes, housing electrodes, etc.) may be electrically coupled to the therapy delivery circuit <NUM> for delivering electrical stimulation pulses to the patient's heart and to the sensing circuit <NUM> and for sensing cardiac electrical signals.

The sensing circuit <NUM> may include an atrial (A) sensing channel <NUM> and a ventricular (V) sensing channel <NUM>. For example, the electrodes <NUM>, <NUM> may be coupled to the atrial sensing channel <NUM> for sensing atrial signals, e.g., P-waves attendant to the depolarization of the atrial myocardium. Further, in some examples, the sensing circuit <NUM> may include switching circuitry for selectively coupling one or more of the available electrodes to cardiac event detection circuitry included in the atrial sensing channel <NUM>. Switching circuitry may include a switch array, switch matrix, multiplexer, or any other type of switching device suitable to selectively couple components of the sensing circuit <NUM> to selected electrodes. Further, for example, electrodes <NUM>, <NUM> may be coupled to the ventricular sensing channel <NUM> for sensing ventricular signals, e.g., R-waves attendant to the depolarization of the ventricular myocardium.

Each of the atrial sensing channel <NUM> and the ventricular sensing channel <NUM> may include cardiac event detection circuitry for detecting P-waves and R-waves, respectively, from the cardiac electrical signals received by the respective sensing channels. The cardiac event detection circuitry included in each of the channels <NUM> and <NUM> may be configured to amplify, filter, digitize, and rectify the cardiac electrical signal received from the selected electrodes to improve the signal quality for detecting cardiac electrical events. The cardiac event detection circuitry within each channel <NUM> and <NUM> may include one or more sense amplifiers, filters, rectifiers, threshold detectors, comparators, analog-to-digital converters (ADCs), timers, or other analog or digital components. A cardiac event sensing threshold, e.g., a P-wave sensing threshold and an R-wave sensing threshold, may be automatically adjusted by each respective sensing channel <NUM> and <NUM> under the control of the control circuit <NUM>, e.g., based on timing intervals and sensing threshold values determined by the control circuit <NUM>, stored in the memory <NUM>, and/or controlled by hardware, firmware, and/or software of the control circuit <NUM> and/or the sensing circuit <NUM>.

Upon detecting a cardiac electrical event based on a sensing threshold crossing, the sensing circuit <NUM> may produce a sensed event signal that is passed to the control circuit <NUM>. For example, the atrial sensing channel <NUM> may produce a P-wave sensed event signal in response to a P-wave sensing threshold crossing. The ventricular sensing channel <NUM> may produce an R-wave sensed event signal in response to an R-wave sensing threshold crossing. The sensed event signals may be used by the control circuit <NUM> for setting pacing escape interval timers that control the basic time intervals used for scheduling cardiac pacing pulses. A sensed event signal may trigger or inhibit a pacing pulse depending on the particular programmed pacing mode. For example, a P-wave sensed event signal received from the atrial sensing channel <NUM> may cause the control circuit <NUM> to inhibit a scheduled atrial pacing pulse and schedule a ventricular pacing pulse at a programmed atrioventricular (AV) pacing interval. If an R-wave is sensed before the AV pacing interval expires, the ventricular pacing pulse may be inhibited. If the AV pacing interval expires before the control circuit <NUM> receives an R-wave sensed event signal from the ventricular sensing channel <NUM>, the control circuit <NUM> may use the therapy delivery circuit <NUM> to deliver the scheduled ventricular pacing pulse synchronized to the sensed P-wave.

In some examples, the device <NUM> may be configured to deliver a variety of pacing therapies including bradycardia pacing, cardiac resynchronization therapy, post-shock pacing, and/or tachycardia-related therapy, such as ATP, among others. For example, the device <NUM> may be configured to detect non-sinus tachycardia and deliver ATP. The control circuit <NUM> may determine cardiac event time intervals, e.g., P-P intervals between consecutive P-wave sensed event signals received from the atrial sensing channel <NUM>, RR intervals between consecutive R-wave sensed event signals received from the ventricular sensing channel <NUM>, and P-R and/or R-P intervals received between P-wave sensed event signals and R-wave sensed event signals. These intervals may be compared to tachycardia detection intervals for detecting non-sinus tachycardia. Tachycardia may be detected in a given heart chamber based on a threshold number of tachycardia detection intervals being detected.

The therapy delivery circuit <NUM> may include atrial pacing circuit <NUM> and ventricular pacing circuit <NUM>. Each pacing circuit <NUM> and <NUM> may include charging circuitry, one or more charge storage devices such as one or more low voltage holding capacitors, an output capacitor, and/or switching circuitry that controls when the holding capacitor(s) are charged and discharged across the output capacitor to deliver a pacing pulse to the pacing electrode vector coupled to respective pacing circuits <NUM> or <NUM>. The electrodes <NUM>, <NUM> may be coupled to the ventricular pacing circuit <NUM> as a bipolar cathode and anode pair for delivering ventricular pacing pulses, e.g., upon expiration of an AV or VV pacing interval set by the control circuit <NUM> for providing atrial-synchronized ventricular pacing and a basic lower ventricular pacing rate.

The atrial pacing circuit <NUM> may be coupled to, for example, the electrodes <NUM>, <NUM> to deliver atrial pacing pulses. The control circuit <NUM> may set atrial pacing intervals according to a programmed lower pacing rate or a temporary lower rate set according to a rate-responsive sensor indicated pacing rate. Atrial pacing circuit may be controlled to deliver an atrial pacing pulse if the atrial pacing interval expires before a P-wave sensed event signal is received from the atrial sensing channel <NUM>. The control circuit <NUM> starts an AV pacing interval in response to a delivered atrial pacing pulse to provide synchronized multiple chamber pacing (e.g., dual or triple chamber pacing).

Charging of a holding capacitor of the atrial or ventricular pacing circuit <NUM> or <NUM> to a programmed pacing voltage amplitude and discharging of the capacitor for a programmed pacing pulse width may be performed by the therapy delivery circuit <NUM> according to control signals received from the control circuit <NUM>. For example, a pace timing circuit included in the control circuit <NUM> may include programmable digital counters set by a microprocessor of the control circuit <NUM> for controlling the basic pacing time intervals associated with various single chamber or multiple chamber pacing (e.g., dual or triple chamber pacing) modes or anti-tachycardia pacing sequences. The microprocessor of the control circuit <NUM> may also set the amplitude, pulse width, polarity, or other characteristics of the cardiac pacing pulses, which may be based on programmed values stored in the memory <NUM>.

The device <NUM> may include other sensors <NUM> for sensing signals from the patient for use in determining a need for and/or controlling electrical stimulation therapies delivered by the therapy delivery circuit <NUM>. In some examples, a sensor indicative of a need for increased cardiac output may include a patient activity sensor, such as an accelerometer. An increase in the metabolic demand of the patient due to increased activity as indicated by the patient activity sensor may be determined by the control circuit <NUM> for use in determining a sensor-indicated pacing rate.

Control parameters utilized by the control circuit <NUM> for sensing cardiac events and controlling pacing therapy delivery may be programmed into the memory <NUM> via the telemetry circuit <NUM>, which may also be described as a communication interface. The telemetry circuit <NUM> includes a transceiver and antenna for communicating with an external device such as a programmer or home monitor, using radio frequency communication or other communication protocols. The control circuit <NUM> may use the telemetry circuit <NUM> to receive downlink telemetry from and send uplink telemetry to the external device. In some cases, the telemetry circuit <NUM> may be used to transmit and receive communication signals to/from another medical device implanted in the patient.

An illustrative ventricular septum lead and delivery system <NUM> is depicted in <FIG> that may be used in a similar manner as the illustrative method and system described herein with respect to <FIG> The lead and delivery system <NUM> may include a delivery catheter <NUM> that extends from a proximal end region (not depicted) to a distal end region <NUM>. The delivery catheter <NUM> may define an opening, or aperture, extending from a proximal end to a distal end <NUM>. The other components of the lead and delivery system <NUM> may be located, or positioned, within the opening of the delivery catheter <NUM> for delivery to a target location such as right ventricular endocardium, the ventricular septum, etc..

The delivery catheter <NUM> may be manipulable by a clinician to locate, or position, the distal end <NUM> proximate (e.g., adjacent, in close contact with, substantially flush to, etc.) a target location such as, e.g., the right ventricular endocardium of the interventricular septal wall of a patient's heart, the right atrial endocardium and central fibrous body (CFB), etc. When the delivery catheter <NUM> is positioned proximate the target location, the delivery catheter <NUM> may be retracted thereby exposing an penetration element <NUM> located within an inner lead body <NUM>, which is located in an outer lead body <NUM>, as shown in <FIG>. In other words, the delivery catheter <NUM> may be moved relative to the remaining components of the system <NUM>. In at least one embodiment, the remaining components of the system <NUM> may be held, or kept, secure and stationary while the delivery catheter <NUM> is pulled proximally away from the target location.

The outer lead body <NUM> extends from a proximal end region to a distal end region <NUM> and includes, among other things, fixation elements <NUM> located proximate the distal end region <NUM>. The fixation elements <NUM> may be resilient such that, e.g., they may be "folded up" within the delivery catheter <NUM> and may move, or "spring," to a deployed state as shown in <FIG>. In other words, the fixation elements <NUM> may be configured in a stowed configuration and a deployed configuration. The fixation elements <NUM> may be predisposed in the deployed configuration and configured to move back to the deployed configuration without application of an outside force. Thus, the delivery catheter <NUM> may provide an outside force by contacting the fixation elements <NUM> to hold (e.g., "fold down," restrict, etc.) the fixation elements <NUM> in the stowed configuration when the distal end region <NUM> is located within the opening of the delivery catheter <NUM>. More specifically, each of the fixation elements extends from a proximal end <NUM> attached to the distal end region <NUM> to a distal end <NUM>, and when the stowed configuration, the distal end <NUM> may extend and point to the distal end <NUM> of the delivery catheter <NUM>. When the distal end <NUM> of the delivery catheter <NUM> is adjacent tissue at a target location and the delivery catheter <NUM> is moved to release the fixation elements <NUM> of the outer lead body <NUM>, the fixation elements <NUM> may pierce the tissue at the target location and "pull" the outer lead body <NUM> (and inner lead body <NUM> and penetration element <NUM>) into the tissue. Such fixation element configuration is described further in <CIT>, Although two fixation elements <NUM> are depicted in <FIG>, it is be understood that one fixation element or more than two fixation elements may be used with the illustrative systems and methods described herein.

A distance <NUM> may be defined between where the proximal end <NUM> of the fixation element <NUM> is coupled to (e.g., extends from) the outer lead body <NUM> and a distal penetration end <NUM> of the penetration element <NUM>. The distance <NUM> may be between about <NUM> millimeters (mm) and about <NUM>. In one embodiment, the distance <NUM> may be <NUM>. In one or more embodiments, the distance <NUM> may be greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, etc. and/or less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM> etc..

In some embodiments, the distance <NUM> may be referred to as an initial penetration distance because, for example, the force applied to the inner lead body <NUM> and penetration element <NUM> by the fixation elements <NUM> being released in the deployed positioned and "grabbing" tissue may be sufficient to drive the inner lead body <NUM> and penetration element <NUM> into the target location up to the distal end region <NUM> of the outer lead body <NUM>. In other words, the fixation elements <NUM> may "drive" the inner lead body <NUM> and penetration element <NUM> into the tissue across the distance <NUM>.

Further, a relationship between the distance <NUM> and the length and shape of the fixation element <NUM> (i.e., from the proximal end <NUM> to the distal end <NUM>) may be defined to provide effective penetration to a particular target location. For example, the length of the fixation elements <NUM> may be less than the distance <NUM> by about <NUM>% or mm to, e.g., allow the penetration element <NUM> and the inner lead body <NUM> (e.g., at least the distal end <NUM>) to contact and/or penetrate the endocardium prior the fixation elements <NUM> contacting the endocardium.

The outer lead body <NUM> may include one or more electrodes within the distal end region <NUM>. In at least one embodiment, the fixation elements <NUM> may function as electrodes to, e.g., sense and or pace right ventricular tissue when the fixation elements <NUM> are located in the right ventricular endocardium.

The outer lead body <NUM> defines an opening extending from the proximal end region to the distal end region <NUM>, and as shown in <FIG>, the inner lead body <NUM> may be located therein. The inner lead body <NUM> may also extend from a proximal end region to a distal end region <NUM> and may define an opening extending from the proximal end region to the distal region <NUM>, within which the penetration element <NUM>, a guide wire, or stylet may be inserted (e.g., located therethrough). As shown in <FIG>, a penetration element <NUM> extends from a proximal end to the distal penetration end <NUM> and is located in the opening of the inner lead body <NUM> extending distally from a distal end <NUM> of the inner lead body <NUM>.

The system <NUM> may be configured to restrict, or limit, the distance <NUM> that the penetration element <NUM> may extend beyond the distal end <NUM> of the inner lead body <NUM>. The distance <NUM> may be defined between the distal end <NUM> of the inner lead body <NUM> and the distal penetration end <NUM> of the penetration element <NUM> (e.g., a sharpened point configured for penetration for the right ventricular endocardium). The distance <NUM> may be between about <NUM> millimeter (mm) and about <NUM>. In one embodiment, the distance <NUM> may be <NUM>. In one or more embodiments, the distance <NUM> may be greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, etc. and/or less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM> etc..

The inner lead body <NUM> may further include one or more electrodes <NUM> that may be configured to be positioned within the intraventricular septum to sense cardiac electrical activity and deliver pacing therapy (e.g., cardiac conduction system pacing therapy, left bundle branch pacing therapy, etc.). Only one of the electrodes <NUM> is exposed on <FIG>.

Once the outer lead body <NUM> is fixated to the target location such as, e.g., the right ventricular endocardial wall, the inner lead body <NUM> may be moved relative to the outer lead body <NUM> to implant the distal end region <NUM> of the inner lead body <NUM> within the ventricular septum. More specifically, the outer lead body <NUM> may remain relatively stationary as being fixated, or anchored, to tissue at the target location. The penetration element <NUM> will have been used to penetrate the target location (e.g., the right ventricular endocardium), and thus, the inner lead body <NUM> may then follow the opening made by the penetration element <NUM> (e.g., tunnel into the opening). First, the penetration element may be removed (e.g., retracted proximally) from the inner lead body <NUM>. In some embodiments, the inner lead body <NUM> may then be moved relative the outer lead body <NUM> to position to the distal end region <NUM> in the desired location for sensing and/or pacing (e.g., with the intraventricular septum proximate the left ventricular endocardium with puncturing or penetrating the left ventricular endocardium). In other embodiments, a guide wire or stylet may be inserted through the opening of the inner lead body <NUM>, which may then be used to position the distal end region <NUM> of the inner lead body <NUM> in the desired location. Additionally, the distal end region <NUM> and distal end <NUM> of the inner lead body <NUM> may define a curvature or taper configured to provide tunneling functionality into tissue and to effectively expand the opening made by the penetration element <NUM>.

The inner lead body <NUM> and the outer lead body <NUM> are depicted in <FIG> with the penetration element <NUM> and the delivery catheter <NUM> completely removed therefrom. The inner lead body <NUM> moved distally away from the outer lead body <NUM>, e.g., after the outer lead body <NUM> is fixated to a target location, is depicted in <FIG>. As shown, the inner lead body <NUM> may also include, or define, fixation elements <NUM> configured to fixate, or fix, the inner lead body <NUM> within the desired location. In this embodiment, the fixation elements <NUM> are configured to provide "one-way" fixation. Thus, the fixation elements <NUM> restrict the inner lead body <NUM> from moving proximally towards (e.g., back towards) the outer lead body <NUM> after the inner lead body <NUM> has been moved away (e.g., distally) from the outer lead body <NUM>. Further, as the inner lead body <NUM> becomes more exposed, more of the electrodes <NUM> along the inner lead body <NUM> are shown.

In brief, the lead and delivery system <NUM> of <FIG> may provide for mechanical injection into the intraseptal space. It may be described that the lead is loaded into a delivery system, a perforating element is extended out of the distal of the lead and is shrouded by the catheter. After lead has been positioned in desired implant location, the lead may be extended out of catheter. As the lead extends out of catheter, the fixation elements (e.g., nitinol tines) may engage the endocardium. Further, as the fixation elements actuate, they extend the lead out of the delivery system. Still further, as the lead tip/needle is actuated forward, the lead is injected into the septum and simultaneously fixated. Then, the needle may be retracted, and the inner assembly of the lead may then be tunneled to desired location. In at least one example, to guide the lead during tunneling, the lead/catheter can be shifted, and shaped/steerable stylets can be used. Further, the inner and outer lead assemblies may then be secured.

An illustrative quadripolar lead <NUM> that may be used with the systems and methods described herein is depicted <FIG>. As shown, the lead <NUM> includes four dipole electrodes <NUM> spaced along the length of the lead <NUM>. The electrodes <NUM> may be spaced apart between about <NUM> millimeters (mm) and about <NUM>. Additionally, the lead <NUM> includes a plurality of small fixation elements <NUM> located between each of the electrodes <NUM>. In one embodiment, the fixation elements <NUM> may be flexible, polymer tines that can fold down in a delivery catheter and can deploy into to muscle fiber when deployed. Also, when enough force is applied, the fixation elements <NUM> will flex and allow removal chronically (e.g., pulled out of an implant location, moved proximally away from an implant location).

In another embodiment, the lead <NUM> may include a helix or helical fixation element as opposed to the fixation elements <NUM> shown in <FIG>. A helix may allow the lead <NUM> to be fixated, and then the inner lead body to be advanced after outer lead body is fixated.

In another embodiment, similar to the fixation elements <NUM> of the inner lead body <NUM>, the fixation elements <NUM> may be configured to be predominantly "one-way. " In other words, the fixation elements <NUM> may restrict proximal movement of the lead <NUM> more than distal movement of the lead <NUM> to, e.g., allow for implantation but restrict dislodgment in the proximal direction.

Terms related to orientation, such as "proximal," "distal," or "end," are used to describe relative positions of components and are not meant to limit the absolute orientation of the embodiments contemplated.

The terms "coupled" or "connected" refer to elements being attached to each other either directly (in direct contact with each other) or indirectly (having one or more elements between and attaching the two elements). Either term may be modified by "operatively" and "operably," which may be used interchangeably, to describe that the coupling or connection is configured to allow the components to interact to carry out functionality.

The singular forms "a," "an," and "the" encompass embodiments having plural referents unless its context clearly dictates otherwise.

The term "or" is generally employed in its inclusive sense, for example, to mean "and/or" unless the context clearly dictates otherwise. The term "and/or" means one or all of the listed elements or a combination of at least two of the listed elements.

The phrases "at least one of," "comprises at least one of," and "one or more of" followed by a list refers to any one of the items in the list and any combination of two or more items in the list.

Claim 1:
An implantable medical device comprising:
a plurality of electrodes comprising:
a right atrial electrode (<NUM>) positionable within the right atrium to deliver cardiac therapy to or sense electrical activity of the right atrium of the patient's heart; and
at least one left ventricular electrode (<NUM>) positionable proximate the left ventricle of the patient's heart to deliver cardiac therapy to or sense electrical activity of the left ventricle of the patient's heart;
a housing (<NUM>) extending from a proximal end region (<NUM>) to a distal end region (<NUM>), wherein the right atrial electrode is leadlessly coupled to the proximal end region;
a leadlet (<NUM>) extending from a proximal region (<NUM>) to a distal region (<NUM>), wherein the proximal region is coupled to the distal end region of the housing and the at least one ventricular electrode is coupled to the distal region of the leadlet, wherein the leadlet is configured to extend through the coronary sinus ostium and into the coronary sinus or a coronary vein of the patient's heart to position the at least one left ventricular electrode proximate the left ventricle of the patient's heart;
a therapy delivery circuit (<NUM>) within the housing and operably coupled to the plurality of electrodes to deliver cardiac therapy to the patient's heart;
a sensing circuit (<NUM>) within the housing and operably coupled to the plurality of electrodes to sense electrical activity of the patient's heart; and
a controller (<NUM>) within the housing and comprising processing circuitry operably coupled to the therapy delivery circuit and the sensing circuit, the controller configured to:
monitor electrical activity using the processing circuitry and one or more of the plurality of electrodes; and
delivering pacing therapy using the processing circuitry and one or more of the plurality of electrodes.