Implantable medical device with distal electrode arrangement

Abstract

In one embodiment, a device includes an elongate housing configured to be fully implanted within a first chamber of a heart, the first chamber of the heart having wall tissue; a distal electrode extending distally from a distal end of the elongate housing and configured to penetrate into wall tissue of a second chamber of the heart; a reference electrode extending from the distal end of the elongate housing; one or more proximal electrodes extending from the distal end of the elongate housing and separated from the distal electrode and the reference electrode; and a processing circuitry located within the elongated housing. The processing circuitry is coupled to the distal electrode, the reference electrode, and the one or more proximal electrodes, and is configured to sense electrical signals of the heart and pacing via the distal electrode, the reference electrode, and the one or more proximal electrodes.

Description

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 476,852, filed on December 22, 2022, the entire content of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present disclosure relates to medical devices, and more particularly to the configuration of electrodes of medical devices. BACKGROUND OF THE INVENTION

[0003] A variety of implantable medical devices (IMDs) have been implanted for treating or monitoring one or more conditions of a patient. Such IMDs can be adapted to monitor or treat conditions or functions related to the heart, muscles, nerves, brain, stomach, endocrine organs, or other organs and their associated functions. Such IMDs can be associated with leads that position electrodes at desired locations, or can be leadless, where the electrodes are integrated with and / or attached to the device housing. These IMDs can have the ability to wirelessly transmit data to another device implanted within the patient or to another instrument located outside the patient or both.

[0004] A cardiac pacemaker is an IMD configured to deliver cardiac pacing therapy to restore a more normal heart rhythm. Such an IMD senses the electrical activity of the heart and delivers cardiac pacing via electrodes based on the sensed electrical activity. Some cardiac pacemakers are implanted at a distance from the heart and are coupled to one or more leads that extend intravascularly into the heart to position the electrodes relative to heart tissue. Some cardiac pacemakers are sized to be fully implanted within one of the chambers of the heart and can include electrodes integrated with or attached to the device housing rather than leads. Some cardiac pacemakers provide dual-chamber functionality by sensing and / or stimulating the activity of both the atria and ventricles, or provide other multi-chamber functionality. A cardiac pacemaker can provide multi-chamber functionality via leads extending into the respective heart chambers, or multiple cardiac pacemakers can provide multi-chamber functionality by being implanted into the respective chambers. SUMMARY OF THE INVENTION

[0005] Generally, the present disclosure relates to implantable medical devices (IMDs) that are configured to sense electrical signals via various vectors in a three-dimensional (3D) space within a patient's tissue with a given single fixed implant orientation. More specifically, the present disclosure relates to IMDs having multiple electrodes and a reference electrode, the electrodes being configured to define orthogonal bipolar vectors similar to a Cartesian coordinate system. Each of the multiple electrodes can define a reference axis with the reference electrode. The IMD can select a sensing vector from the respective reference axes or from a combination of calculated reference axes and sense an electrical signal along the selected sensing vector. Based on the sensed electrical signal, the IMD can deliver electrical stimulation to the patient's tissue via the multiple electrodes.

[0006] In some examples, a single IMD is implanted in a chamber of a patient's heart and is capable of sensing cardiac pacing and / or delivering cardiac pacing to more than one chamber, which can obviate the need for a lead device or multiple smaller devices to provide such functionality, which can reduce the amount of material implanted in the patient. In some examples, such an implantable medical device includes a first electrode configured to penetrate the wall tissue of the heart chamber in which the device is implanted and enter the wall tissue of another heart chamber. In addition to the first electrode, the device also includes a reference electrode and one or more second electrodes configured to contact the wall tissue of the heart chamber. The electrodes can be connected to the distal end of the device. The first electrode can be a helix configured to penetrate the patient's tissue. Each of the first electrode and the second electrode can define a reference axis with the reference electrode. The reference axes together define a 3D coordinate system within which the IMD can select sensing vectors and pacing vectors. The IMD can sense electrical signals of the heart and deliver cardiac pacing to cardiac tissue in one or more chambers of the heart based on the sensing vectors and pacing vectors, respectively. Any sensed signal in the cardiac tissue can be represented by one or more sensing vectors in the 3D coordinate system. The IMD can determine cardiac pacing therapy for one or more chambers of the heart and deliver the cardiac pacing therapy to the one or more chambers along the pacing vectors within the 3D coordinate system via the first electrode and the second electrodes.

[0007] In some examples, the exemplary IMDs described herein can improve the accuracy or fidelity of sensed electrical signals, for example, by increasing a set of possible sensing vectors available to the IMD. Using electrodes of an IMD arranged according to a defined 3D coordinate system can reduce the dependence on the orientation of the IMD to accurately sense electrical signals, for example, by allowing the IMD to deviate from a single fixed sensing vector. In some examples, using electrodes of an IMD arranged according to a defined 3D coordinate system reduces the effect of rotation of the IMD on sensed electrical signals, for example, by allowing the IMD to change the sensing vector over time based on signal quality. Using electrodes of an IMD arranged according to a defined 3D coordinate system can also prevent each electrode from sensing cross contributions and / or overlapping electrical signals along other directions, thereby simplifying and improving the accuracy of the electrical signal sensing process. For example, the IMD can sense unique signal content along each reference axis of the 3D coordinate system and determine electrical signals within the tissue based on the unique signal content. The IMD can also determine one or more intermediate sensing vectors based on the sensing vectors along each reference axis and sense electrical signals along the one or more intermediate sensing vectors. The electrode arrangements described herein can also allow the IMD to deliver more accurate stimulation (capturing the stimulation of the intended tissue) and / or minimize unintended stimulation (e.g., cross-chamber stimulation). In some examples, the exemplary IMD can also reduce the pacing threshold required to successfully capture the wall tissue of a chamber of the heart.

[0008] In one example, the present disclosure relates to a device that includes: an elongate housing that extends from a proximal end of the housing to a distal end of the housing, the elongate housing configured to be fully implanted within a first chamber of a heart, the first chamber of the heart having wall tissue; a distal electrode that extends distally from the distal end of the elongate housing, the distal electrode configured to penetrate into wall tissue of a second chamber of the heart that is separated from the first chamber of the heart; a reference electrode that extends from the distal end of the elongate housing; one or more proximal electrodes that extend from the distal end of the elongate housing, wherein the one or more proximal electrodes are separated from the distal electrode and the reference electrode; sensing circuitry located within the elongate housing and coupled to the distal electrode, the reference electrode, and the one or more proximal electrodes; and processing circuitry located within the elongate housing, the processing circuitry configured to control the sensing circuitry to sense electrical signals of the heart via the distal electrode, the reference electrode, and the one or more proximal electrodes.

[0009] In some examples, the present disclosure describes a method that includes: sensing a plurality of electrical signals from the heart via a sensing circuitry of an implantable medical device (IMD) and via a plurality of combinations of a distal electrode extending distally from a distal end of the elongated housing of the IMD, a reference electrode extending from the distal end of the elongated housing, and one or more proximal electrodes extending from the distal end of the elongated housing; determining a combined electrical signal by a processing circuitry of the IMD based on the sensed electrical signals and a sensing vector; and delivering cardiac pacing therapy to one or more chambers of the heart by one or more of the distal electrode and the one or more proximal electrodes based on the combined signal, wherein the distal electrode is configured to penetrate into the wall tissue of the second chamber, and wherein the one or more proximal electrodes and the reference electrode are configured to remain in contact with the wall tissue of the first chamber without the one or more proximal electrodes penetrating the wall tissue of the first chamber.

[0010] In some examples, the present disclosure describes a device that includes: an elongated housing extending from a proximal end to a distal end, the elongated housing configured to be fully implanted within a first chamber of the heart; a distal electrode extending distally from the distal end of the elongated housing, the distal electrode configured to penetrate into the wall tissue of a second chamber of the heart, the second chamber of the heart being separated from the first chamber of the heart; two proximal electrodes extending from the distal end of the elongated housing, wherein the two proximal electrodes are separated from the distal electrode, and wherein each of the two proximal electrodes is configured to remain in contact with the wall tissue of the first chamber without penetrating the wall tissue of the first chamber; a reference electrode extending from the distal end of the elongated housing and separated from the distal electrode and the two or more proximal electrodes, the reference electrode configured to: define a first axis with the distal electrode; define a second axis with a first proximal electrode of the two proximal electrodes; and define a third axis with a second proximal electrode of the two proximal electrodes; a sensing circuitry disposed within the elongated housing; a signal generation circuitry disposed within the elongated housing; and a processing circuitry located within the elongated housing, the processing circuitry configured to: cause the sensing circuitry to sense electrical signals from the heart along at least two of the first axis, the second axis, and the third axis via the distal electrode, the first proximal electrode, and the second proximal electrode, respectively; determine a combined signal based on the sensed electrical signals and a three-dimensional (3D) sensing vector; and cause the signal generation circuitry to deliver cardiac pacing therapy to the heart via one or more of the distal electrode, the first proximal electrode, or the second proximal electrode based on the combined electrical signal.

[0011] The present invention content aims to provide an overview of the subject matter described in this disclosure. The present invention content is not intended to provide an exclusive or exhaustive explanation of the methods and systems described in detail in the following drawings and specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Details of one or more examples of the present disclosure are set forth in the following drawings and description. Other features, objects, and advantages of the present disclosure will be apparent from the description and drawings, and from the claims.

[0013] Figure 1 is a conceptual diagram showing an exemplary device implanted in a patient's heart according to one or more aspects of the present disclosure.

[0014] Figure 2A is a perspective view of an exemplary device having two or more proximal electrodes according to one or more aspects of the present disclosure Figure 1 thereof.

[0015] Figure 2B is a perspective view of an exemplary device having one proximal electrode according to one or more aspects of the present disclosure Figure 1 thereof.

[0016] Figure 3 is a functional block diagram showing an exemplary configuration of an IMD according to one or more aspects of the present disclosure Figures 1 to 2B thereof.

[0017] Figure 4 is a conceptual diagram of a device implanted at a target implantation site Figures 1 to 3 thereof.

[0018] Figure 5 is a partial view of a device according to one or more aspects of the present disclosure Figure 1 thereof.

[0019] Figure 6 is a top partial view of a device according to one or more aspects of the present disclosure Figure 1 thereof.

[0020] Figure 7 is a side view of a distal portion of a device according to one or more aspects of the present disclosure Figure 1 thereof.

[0021] Figure 8 is a flowchart showing an exemplary process for sensing cardiac electrical signals via an exemplary device in any of the Figures 1 to 7 figures and delivering cardiac pacing therapy to a patient's heart. DETAILED DESCRIPTION

[0022] Generally, the present disclosure relates to the configuration of electrodes of an implantable medical device (IMD). More specifically, the present disclosure relates to an IMD having a plurality of electrodes configured to sense electrical signals from a patient's tissue and deliver electrical stimulation (e.g., cardiac pacing) to the patient's tissue. The physical arrangement of the plurality of electrodes on the IMD can define a plurality of reference axes that define a three-dimensional (3D) coordinate system.

[0023] Figure 1 is a conceptual diagram showing an exemplary device 104 implanted in a patient's heart 102 according to one or more aspects of the present disclosure. The device 104 is shown implanted in a target implantation region 106 in the right atrium (RA) of the patient's heart 102, such as the triangle of Koch in the heart 102, where the distal end of the device 104 points towards the left ventricle (LV) of the patient's heart 102. Although in Figure 1 the example shown, the distal end of the device 104 points towards the LV, the distal end may point towards other targets, such as the interventricular septum of the heart 102. The target implantation region 106 can be located between the His bundle and the coronary sinus and can be adjacent to the tricuspid valve.

[0024] The device 104 includes a distal end 110 and a proximal end 116. The distal end 110 includes a distal electrode 112, a reference electrode 113, and one or more proximal electrodes 114. The distal electrode 112 can define a helical shape, for example, as Figure 1 shown. The distal electrode 112 extends from the distal end 110 and can penetrate the wall tissue of the first chamber (e.g., the RA in the example shown) into the wall tissue of the second chamber (e.g., the ventricular myocardium 108 of the LV in the example shown). When the distal electrode 112 penetrates the wall tissue of the first chamber, the reference electrode 113 and the proximal electrodes 114 can contact the wall tissue of the first chamber. The reference electrode 113 and the proximal electrodes 114 can be disposed at corresponding positions on the distal end 110 of the device 104, such as around the perimeter of the distal end 110.

[0025] Figure 1 The configuration of the electrodes 112, 113, and 114 shown allows the device 104 to sense cardiac signals and / or deliver cardiac pacing to multiple chambers of the heart 102, such as the RA and the ventricles in the example shown. In this way, the configuration of the electrodes 112, 113, and 114 can facilitate the delivery of A-V synchronous pacing through a single device 104 implanted within a single chamber (e.g., the RA). Although in Figure 1In the example shown, the device 104 is implanted in the target implantation region 106 to sense and / or pace the RA and ventricles, but a device having an electrode configuration according to an example of the present disclosure can be implanted at any of various locations to sense and / or pace any two or more chambers of the heart 102. For example, the device 104 can be implanted in region 106 or another region, and the first electrode 112 can extend into the tissue of the LV or the septum (e.g., myocardial tissue) to facilitate, for example, the delivery of A-V synchronous pacing. Additionally, a device having an electrode configuration according to an example of the present disclosure can be implanted at any of various locations within a patient's body for sensing and / or delivering therapy to other patient tissue.

[0026] The electrodes 112, 113, and 114 can define a 3D coordinate system. Each of the electrodes 112 and 114 can be combined with the reference electrode 113 to define a reference axis and sense the signal component of an electrical signal in the heart tissue along the reference axis. For example, the first proximal electrode 114 and the reference electrode 113 can define the X-axis of the 3D coordinate system, the second proximal electrode 114 and the reference electrode 113 can define the Y-axis of the 3D coordinate system, and the distal electrode 112 and the reference electrode 113 can define the Z-axis of the 3D coordinate system. Each reference axis can be orthogonal to each other reference axis. For example, the X-axis, Y-axis, and Z-axis defined by the electrodes 112, 113, and 114 can be orthogonal to each other. The device 104 can define and select a sensing vector based on the combination of reference axes. Then, the device 104 can sense the electrical signal within the wall tissue along the sensing vector. Any electrical signal (e.g., an electrogram (EGM) signal) within the wall tissue near the target implantation region 106 can be sensed by the device 104 along one or more sensing vectors and / or along a combination of sensing vectors. Based on the sensed electrical signal, the device 104 can determine whether an event has occurred and / or whether the heart 102 is experiencing a cardiac disorder. Based on this determination, the device 104 can then deliver cardiac pacing therapy to one or more chambers of the heart 102 along one or more pacing vectors within the 3D coordinate system.

[0027] The electrode configurations described herein may provide several advantages over other IMD designs. Using the distal electrode 112 and two or more proximal electrodes 114 to define a 3D coordinate system together with the reference electrode 113 allows each of the distal electrode 112 and the proximal electrodes 114 to sense signal components along a single axis without overlapping and / or cross contributions of electrical signals along other axes, thus simplifying the sensing vector generation and selection process. By allowing selection from multiple sensing vectors (including virtual sensing vectors based on combinations of two or more physical vectors), the use of the 3D coordinate system can further eliminate the need to precisely orient the device 104 during implantation to generate accurate and / or consistent sensing vectors. The increased consistency of the sensed electrical signals can enable the device 104 to improve the determination of signal amplitude, position, and / or morphology, thus improving the event and / or condition detection capabilities of the device 104.

[0028] Additionally, placing the reference electrode 113 at the distal end 110 provides several advantages. For example, relative to devices where the reference electrode is proximal to the distal end, placing the reference electrode 113 at the distal end 110 reduces the bipolar electrode spacing between the distal electrode 112 and the reference electrode 113 and between each proximal electrode 114 and the reference electrode 113. The reduction in bipolar electrode spacing can reduce and / or prevent the sensing of far-field signals (e.g., far-field P waves in ventricular signals, far-field R waves in atrial signals). In some examples, for the delivery of pacing or other stimulation, the reduced bipolar electrode spacing can, for example, reduce the likelihood of unintended transchamber stimulation by reducing the pacing capture threshold and voltage threshold required to stimulate cardiac tissue. Additionally, the reduction in the pacing capture threshold and voltage threshold can reduce power consumption, thus increasing the power life of the device 104.

[0029] Figure 2A is a perspective view showing the device 104. The device 104 includes a housing 200 that defines an airtight internal cavity. The housing 202 may be formed of a conductive material, which includes titanium or a titanium alloy, stainless steel, MP35N (a non-magnetic nickel-cobalt-chromium-molybdenum alloy), a platinum alloy, or other biocompatible metal or metal alloy or other suitable conductive material. In some examples, the housing 200 is formed of a non-conductive material, which includes ceramic, glass, sapphire, silicone, polyurethane, epoxy resin, acetyl copolymer plastic, polyetheretherketone (PEEK), liquid crystal polymer, other biocompatible polymers, or other suitable non-conductive materials.

[0030] The housing 200 extends between a distal end 202 and a proximal end 204. In some examples, the housing 200 can be cylindrical or substantially cylindrical, but can also be other shapes, such as prismatic or other geometric shapes. The housing 200 can include, for example, a delivery tool interface member 206 located at the proximal end 204 for engaging a delivery tool during implantation of the device 104. At the distal end 202, the housing 200 can define a face of the housing 200. The face of the housing 200 can be at least substantially orthogonal to the longitudinal axis 208. The reference electrode 113 and the proximal electrodes 114A, 114B (collectively referred to as "proximal electrodes 114") are disposed on the face of the housing 200 (e.g., around the perimeter of the housing 200) and extend distally along the longitudinal axis 208.

[0031] Each of the distal electrode 112, the reference electrode 113, and the proximal electrodes 114 is attached to the housing 200 at or near the distal end 202. The distal electrode 112 can be disposed on the distal end of an elongate body 210 that extends distally from the distal end 202 of the housing 200. The elongate body 210 can extend from a first end fixedly attached to the housing 200 at or near the distal end 202 to a second end, in Figure 2A an example, the second end is not attached to the housing 202 except via the first end (e.g., is a free end). The second end of the elongate body 210 can hold or define the distal electrode 112. The elongate body 210 can extend along the longitudinal axis 208 and can define a helical and / or coiled shape or any other shape.

[0032] The elongate body 210 can include one or more coatings (e.g., electrically insulating coatings) configured to define a distal electroactive region or the distal electrode 112. In some examples, the distal electroactive region can be closer to the second end of the elongate body 210, such as the distal end. In Figure 2A an example, the distal electroactive region includes the distal end of the elongate body 210. Each of the reference electrode 113 and / or the proximal electrodes 114 can include one or more coatings configured to define a corresponding electroactive region on the outer surface of the respective electrode. In some examples, as Figure 2A shown, the electroactive regions of the reference electrode 113 and / or the proximal electrodes 114 form a ring around the steroid eluting element or the therapeutic substance dispensing device, for example, as discussed in more detail with respect to Figure 5 Each of the reference electrode 113 and / or the proximal electrodes 114 can be a button electrode, a spring electrode, or any other suitable type or shape of electrode.

[0033] Each of the electrodes 112, 113, and 114 can be formed of a conductive material such as titanium, platinum, iridium, tantalum, stainless steel, or an alloy thereof. Each of the electrodes 112, 113, and 114 can be coated with an electrically insulating coating such as parylene, polyurethane, silicone, epoxy resin, or other insulating coatings to reduce the conductive active surface area of the corresponding electrode and to define the corresponding electroactive region. Defining the electroactive regions of the electrodes 112, 113, and 114 by covering portions of each electrode with an insulating coating can increase the electrical impedance of the electrodes 112, 113, and 114 and, thus, reduce the current delivered during a pacing pulse for capturing cardiac tissue. The lower current consumption saves the power source of the device 104, such as one or more rechargeable or non-rechargeable batteries.

[0034] In some examples, each of the electrodes 112, 113, and 114 can have a conductive material coated on the corresponding electroactive region. For example, the electroactive region of any one of the electrodes 112, 113, and 114 can be coated with titanium nitride (TiN). Each of the electrodes 112, 113, and 114 can be made of substantially similar materials or can be made of materials different from each other.

[0035] In Figure 2A the example, the elongate body 210 takes the form of a helix. In some examples, the distal electrode 112 can be the elongate body defining the helix. In some examples, the helix is an object having a three-dimensional shape similar to the three-dimensional shape of a wire uniformly wound in a single layer around a cylindrical surface or a conical surface or a mandrel such that if the surface were unwound into a plane, the wire would be a straight line. The reference electrode 113 and the proximal electrode 114 are disposed on the distal end 202, and each electrode can include a button electrode (e.g., as Figure 2A shown), or any other suitable type or shape of electrode.

[0036] In some examples, as Figure 2A shown, the device 104 can have two proximal electrodes 114 disposed on the distal end 202 of the housing 200. In other examples, for instance, as Figure 2BAs shown and described in more detail herein, the device 104 can have a proximal electrode 114 disposed on the distal end 202. Each of the proximal electrodes 114 can define a reference axis with the reference electrode 113. For example, the proximal electrode 114A can define a first reference axis with the reference electrode 113, and the proximal electrode 114B can define a second reference axis with the reference electrode 113. The proximal electrode 114 and the reference electrode 113 can be arranged around the perimeter of the distal end 202 such that the first reference axis is orthogonal to the second reference axis. In some examples, the device 104 can include three or more proximal electrodes 114 disposed on the distal end 202 of the housing 200. In such examples, any selection of the proximal electrode 112 among the three or more proximal electrodes 114 can define a separate reference axis with the reference electrode 113. The reference electrode 113 and the proximal electrode 114 can be equally spaced apart around the perimeter of the distal end 202. In some examples, one or more of the reference electrode 113 and the proximal electrode 114 can be disposed at a user-selected angle away from the proximal end of the elongate body 210.

[0037] The elongate body 210 can be formed of a conductive material (such as titanium, platinum, iridium, tantalum, or an alloy thereof), and / or formed of a non-conductive material. At least a portion of the elongate body 210 (e.g., the portion near the distal electrode 112) can be coated with an electrically insulating coating, such as parylene, polyurethane, silicone, epoxy resin, or other insulating coatings. In some examples, the elongate body 210 can be formed of a shape memory metal (such as nitinol, platinum, titanium, MP35N, etc.) and / or a shape memory polymer (such as silicone, polyurethane, polyetheretherketone (PEEK), etc.) or other materials.

[0038] In some examples, the elongate body 210 can include one or more anti-rotation features. The anti-rotation features can include the shape of the elongate body 210, the dimensions of the elongate body 210 (e.g., outer diameter, pitch, etc.), one or more features disposed on the outer surface of the elongate body 210, and the like. The shape and / or dimensions of the elongate body 210 can include the geometry of the elongate body 210, the variable diameter configuration of the elongate body 210, the variable pitch configuration of the elongate body 210, the waveform configuration of the elongate body 210, or any combination herein. One or more anti-rotation features disposed on the elongate body 210 can include, but are not limited to, elongate darts, barbs, or spines. The one or more anti-rotation features can resist rotation of the elongate body 210 and / or the distal electrode 112 (e.g., by penetrating tissue, by increasing friction between the elongate body 210 and the tissue, etc.). The one or more anti-rotation features can be disposed in any quadrant of the face of the distal end 202 (other than the quadrant containing the proximal end of the elongate body 210), for example, to stabilize the device 104 within the tissue.

[0039] In some examples, electrodes 113 and 114 are positioned on the distal end 202 of the housing 200 and resist rotation of the elongate body 210 and / or the distal electrode 112. Each of the electrodes 113 and 114 can be at least partially surrounded by tissue of the heart 102 and engage the tissue to prevent rotation of the elongate body 210 and / or the distal electrode 112. In some examples, one or more of the electrodes 113 and 114 are disposed in a quadrant of a face of the distal end 202 of the housing 200 that does not contain the proximal end of the elongate body 210, or are separated from the proximal end of the elongate body 210 by a predetermined angle, e.g., to prevent unintended rotation of the elongate body 210.

[0040] In some examples, the elongate body 210 can define a helix and / or a spiral having a varying diameter configuration, e.g., to place the distal electrode 112 at the same radial position relative to the longitudinal axis 208 as the reference electrode 113 and at a more distal longitudinal position relative to the longitudinal axis 208 than the reference electrode 113. In such examples, the distal electrode 112 can define a reference axis with the reference electrode 113 that is orthogonal to the distal end 202 of the housing 200 and parallel to the longitudinal axis 208. In some examples, the elongate body 210 can define a helix and / or a spiral having an outer diameter at the proximal end of the elongate body 210 that is less than the outer diameter at the distal end of the elongate body 210 (e.g., at the distal electrode 112). The varying diameter can cause the elongate body 210 to resist rotation within the tissue of the heart 102.

[0041] As Figure 2A shown, the elongate body 210 can be a right-handed helix, but in other examples, the distal electrode 112 can have a left-handed helix. The elongate body 210 can have a constant or varying pitch along the longitudinal axis 208. In some examples, the elongate body 210 can have a shape other than a helix. For example, the elongate body 210 can have a geometric shape (e.g., triangular shape, rectangular shape, hexagonal shape, octagonal shape, leaf-shaped, etc.). Such geometric shapes can be equilateral.

[0042] Each of the distal electrode 112, reference electrode 113, and / or proximal electrode 114 can vary in size and shape to enhance tissue contact between the electroactive region defined by any one of the electrodes 112, 113, and 114 and the tissue of the heart 102. For example, the distal electrode 112 can have a circular cross-section or can be made with a flatter cross-section (e.g., oval or rectangular) based on tissue contact specifications. In some examples, one or more of the reference electrode 113 and proximal electrode 114 can have outer surfaces that vary in size and shape (e.g., oval outer surface, outer surface with a larger diameter, etc.) to enhance tissue contact of the corresponding electroactive region. In some examples, as Figure 2A shown, the reference electrode 113 and proximal electrode 114 can be disposed directly on the distal end 202 of the housing 200.

[0043] The distal end of the distal electrode 112 can have a distal tip that is conical, hemispherical, or has an angled edge (the distal tip having a narrow tip diameter, e.g., less than 1 millimeter (mm)) for penetrating into and through a tissue layer. In some examples, the distal end of the distal electrode 112 can be a sharp or angled end or a sharp or beveled edge, but the sharpness can be constrained to avoid cutting actions that could cause lateral displacement of the distal end of the distal electrode 112 and undesired tissue trauma. In some examples, the elongated body 210 can have a maximum diameter at its base where it meets the distal end 202 of the housing. In such examples, the outer diameter of the helix defined by the elongated body 210 can decrease from the distal end 202 of the housing to the distal end of the distal electrode 112. In some examples, the diameter of the distal electrode 112 can vary from the distal end 204 of the housing to the distal end of the distal electrode 112.

[0044] In some examples, two or more of the electrodes 112, 113, and 114 can be used to sense electrical signals from the heart 102 at the target implantation region 106. The distal electrode 112 and the proximal electrode 114 can define three reference axes with the reference electrode 113, and the three reference axes can define a 3D coordinate system that includes the target implantation region 106. When the device 106 senses electrical signals (e.g., atrial signals, ventricular signals) within the target implantation region 106, each of the distal electrode 112 and the proximal electrode 114 can sense the component of the electrical signal along the corresponding reference axis. The device 104 can then represent the sensed electrical signals as a vector that includes one or more sensing vectors. The device 104 can determine the occurrence of an event (e.g., depolarization) in one or more chambers of the heart 102 or a cardiac disorder based on the sensed components and the sensing vectors. Similarly, the device 104 can determine a pacing vector within the 3D space defined by the 3D coordinate system, the pacing vector being configured to deliver cardiac pacing to one or more chambers of the heart 102. In connection with the foregoing, the inventors have found that it is desirable to configure the electrodes so as to maximize the amount or volume of living tissue between the electrodes. The embodiments disclosed herein achieve this in the context of an electrode array located at the distal end of an elongated device housing.

[0045] A sensing vector is a vector by which the device 104 senses atrial or ventricular signals from the target implantation region 106. For example, the device 104 can sense electrical signals from the target implantation region 106 along a plurality of sensing vectors to sense the electrical signals at corresponding locations (e.g., atrial myocardium, ventricular myocardium) within the target implantation region 106. The device 104 can define the sensing vectors within the 3D space defined by the 3D coordinate system. Similarly, a pacing vector is a vector by which the device 104 is used to deliver cardiac pacing to the atrial or ventricular myocardium and can be defined within the 3D space. Using the electrodes 112, 113, and 114 to define the pacing and sensing vectors can reduce the importance of the (sometimes unpredictable) orientation of the device 104 during implantation and improve pacing and / or sensing quality, for example, due to a reduction and / or elimination of overlapping signal components from another region within the target implantation region 106. For example, each of the electrodes 112 and 114 will only sense the component of the electrical signal along a single axis (e.g., the reference axis), which obviates the need to separate the cross contributions of the components of the electrical signal along multiple axes to determine the position of the sensing vector relative to the device 104.

[0046] In some examples, the proximal electrode 114 may be configured as an atrial cathode electrode for delivering a pacing pulse to atrial tissue, such as at the target implantation region 106, in combination with the reference electrode 113. The proximal electrode 114 and the reference electrode 113 may also be used to sense atrial P waves for controlling atrial pacing pulses (delivered in the absence of a sensed P wave), and for controlling atrial synchronous ventricular pacing pulses delivered using the distal electrode 112 as the cathode and the reference electrode 113 as the return anode.

[0047] For example, relative to other IMDs having a reference electrode disposed proximally on the housing 202, placing the reference electrode 113 at the distal end 202 reduces the bipolar electrode spacing between the proximal electrode 114 and the reference electrode 113 and between the distal electrode 112 and the reference electrode 113. The reduced bipolar electrode spacing may improve the sensing and pacing capabilities of the electrodes 112, 113, and 114. For example, the electrodes 112 and 114 may deliver cardiac pacing therapy to atrial myocardium and / or ventricular myocardium at a lower voltage, which may reduce the likelihood of unintended transchamber capture of cardiac tissue. For example, due to an increase in the surface area of the electrode (e.g., the proximal electrode 114), due to a decrease in impedance and / or due to the reduced bipolar electrode spacing, the electrodes 112 and 114 may deliver cardiac pacing to atrial myocardium and ventricular myocardium at a reduced pacing threshold. For example, the reduction in bipolar electrode spacing increases the current intensity of the pacing pulses delivered by the device 104 to atrial myocardium and / or ventricular myocardium, thereby reducing the pacing threshold of the atrial myocardium and / or ventricular myocardium, respectively.

[0048] At the distal end 110, the device 104 includes a distal fixation assembly that includes the distal electrode 112, the reference electrode 113, the proximal electrode 114, the elongate body 210, and the distal end 202 of the housing. The distal end of the distal electrode 112 may be configured to rest within the ventricular myocardium of the patient, and the reference electrode 113 and the proximal electrode 114 may be configured to contact the atrial endocardium of the patient. The proximal electrode 114 may be selectively coupled individually to the sensing circuitry and / or pacing circuitry encapsulated by the housing 200 to serve as an anode with the distal electrode 112 or as an atrial cathode electrode, or may be electrically common and not individually selectable. In some examples, each of the distal electrode 112 and the proximal electrode 114 may be coupled to the sensing and / or pacing circuitry within the housing 200 via a separate feedthrough or feedthrough assembly.

[0049] During implantation of device 104 into target implantation region 106, a clinician may sense signals from tissue of heart 102 at the target implantation region 106 via each of electrodes 112 and 114, e.g., to determine the position and orientation of device 104 within the target implantation region 106. The clinician may orient device 104 within the target implantation region 106 based on the sensed signals from electrodes 112 and 114. For example, the clinician may orient device 104 based on the sensed signals such that a reference axis defined by distal electrode 112 and reference electrode 113 extends distally toward tissue of a second chamber of heart 102, and a plane defined by reference electrode 113 and proximal electrode 114 encompasses tissue of a first chamber of heart 102.

[0050] Device 104 may rotate automatically, e.g., due to torque of tissue of heart 102 on device 104, and elongate body 210 may be partially ejected from tissue of heart 102, resulting in loss of contact between the tissue and at least one of electrodes 113 and 114. In such examples, device 104 may sense (e.g., via far-field sensing) signals from a first chamber of heart 102 and deliver cardiac pacing to the first chamber of the heart via distal electrode 112 and reference electrode 113. Device 104 may determine a sensing vector based on a reference axis defined by distal electrode 112 and reference electrode 113 to sense electrical signals from tissue of a first chamber of heart 102.

[0051] Figure 2B is a perspective view of an exemplary device having one proximal electrode 114C in accordance with one or more aspects of the present disclosure. Proximal electrode 114C may be substantially similar to proximal electrode 114 (i.e., proximal electrode 114A, proximal electrode 114B). As shown in FIG. 2, proximal electrode 114C may define a proximal reference axis with reference electrode 113, and distal electrode 112 may define a distal reference axis with reference electrode 113. Figure 1 In some examples, as

[0052] shown, the proximal reference axis is orthogonal to the distal reference axis. Device 104 may be configured to sense electrical signals in heart 104 along a reference plane defined by the proximal reference axis and the distal reference axis. During implantation, the clinician may rotate the device within the target implantation region 106 to rotate the reference plane about longitudinal axis 208 and place the reference plane within the target implantation region 106 in a predetermined orientation. Figure 2B

[0053] ​During implantation, a clinician can navigate a device 104 within a first chamber of a heart 102 to map the first chamber and determine a position and an expected orientation of the device 104 within a target implantation region 106 of the first chamber based on the mapping of the first chamber. For example, the clinician can sense a depolarization waveform pattern in tissue of the heart 102 via electrodes 112, 113, and 114 on the device 104 and determine the placement and / or orientation of the device 104 based on the depolarization waveform pattern. The electrodes 112, 113, and 114 form reference axes extending in different directions (e.g., orthogonal to other reference axes) that can provide the clinician with sensing and mapping capabilities in different directions at any given time, thereby simplifying the mapping process.

[0054] A reference electrode 113 and a proximal electrode 114C can be disposed on a distal end 202 of a housing 200. The placement of the distal electrode 112, the reference electrode 113, and the proximal electrode 114C can result in improved sensing and pacing capabilities and / or a reduction in pacing threshold, e.g., as described in more detail above with respect to Figure 2A More detailed description.

[0055] Figure 3 is a functional block diagram showing an exemplary configuration of the device 104. As Figure 3 shown, the device 104 includes electrodes 112, 113, and 114 that can be configured as described with respect to Figure 1 and FIG. 2. For example, as described with respect to Figure 1 and FIG. 2, the distal electrode 112 can be configured to extend from the distal end 202 of the housing 200 and can penetrate the wall tissue of a first chamber (e.g., RA) into the wall tissue of a second chamber (e.g., LV). The reference electrode 113 and the proximal electrode 114 extend from the distal end 202 of the housing 200 and can be configured to maintain contact with the wall tissue of the first chamber without penetrating the wall tissue of the first chamber.

[0056] In Figure 3 the example shown, the device 104 includes a switch circuitry 302, a sensing circuitry 304, a signal generation circuitry 306, a sensor 308, a processing circuitry 310, a telemetry circuitry 312, a memory 314, and a power supply 316. The various circuitries can be programmable or fixed-function circuitries or include programmable or fixed-function circuitries that are configured to perform the functions attributed to the respective circuitries. The memory 314 can store computer-readable instructions that, when executed by the processing circuitry 310, cause the device 104 to perform various functions. The memory 314 can be a storage device or other non-transitory medium. Figure 3 The components of the device 104 shown in

[0057] The signal generation circuitry 306 generates an electrical stimulation signal, such as a cardiac pacing pulse. The switch circuitry 302 is coupled to the electrodes 112, 113, and 114 and may include one or more switch arrays, one or more multiplexers, one or more switches (e.g., a switch matrix or other collection of switches), one or more transistors, or other circuitry. The switch circuitry 302 is configured to direct the stimulation signal from the signal generation circuitry 306 to a selected combination of the electrodes 112, 113, and 114 having a selected polarity, e.g., to selectively deliver a pacing pulse to the RA, LV, or septum of the heart 102. For example, to pace one or both ventricles, the switch circuitry 302 may couple the distal electrode 112 that penetrates the wall tissue of the ventricle or septum to the signal generation circuitry 306 as the cathode and couple one or both of the reference electrode 113 or the proximal electrode 114 to the signal generation circuitry 306 as the anode. As another example, to pace the RA, the switch circuitry 302 may couple one or more of the proximal electrodes 114 to the signal generation circuitry 306 as the cathode and couple one or both of the distal electrode 112 or the reference electrode 113 to the signal generation circuitry 306 as the anode. As another example, the switch circuitry 302 may alternately couple the electrodes 112, 113, and / or 114 to the signal generation circuitry 306 as the cathode or anode to deliver a pacing pulse to the heart 102.

[0058] The switch circuitry 302 may also selectively couple the sensing circuitry 304 to a selected combination of the electrodes 112, 113, and 114, e.g., to selectively sense the electrical activity of the RA or ventricles of the heart 102. The sensing circuitry 304 may include filters, amplifiers, analog-to-digital converters, or other circuitry configured to sense cardiac electrical signals via the electrodes 112, 113, and / or 114. For example, the switch circuitry 302 may couple one or more sensing vectors to corresponding sensing channels provided by the sensing circuitry 304 to sense ventricular or atrial cardiac electrical signals. The switch circuitry 302 may then direct the signals from one or more of the electrodes 112 and 114 that make up the sensing vector to the corresponding sensing channel.

[0059] In some examples, the sensing circuitry 304 can select sensing vectors for sensing electrical activity. Each sensing vector can be a combination of signal components from one or more of the electrodes 112 and 114. The sensing circuitry 304 can represent any vector within the 3D coordinate system based on one or more sensing vectors. For example, the sensing circuitry 304 determines an optimal sensing vector based on a sensing vector within the 3D coordinate system or a combination of two or more sensing vectors within the 3D coordinate system. Once the sensing circuitry 304 selects a sensing vector, the sensing circuitry 304 can sense electrical signals from the heart 102 along the selected sensing vector to sense the cardiac activity of one or more chambers of the heart 102. Sensing electrograms (EGMs) in cardiac tissue using sensing vectors within the 3D coordinate system by the sensing circuitry 304 reduces the dependence of the sensing circuitry 304 on the precise orientation of the device 104 (e.g., electrodes 112, 113, and 114) within the target implantation region 106 and / or eliminates the effect of rotation of the device 104 on the EGM, thereby increasing the flexibility of the sensing capabilities of the sensing circuitry 304. In some examples, the use of sensing vectors enables the sensing circuitry 304 to sense EGMs with more consistent amplitudes and morphologies. In some examples, based on changes in the orientation of the device 104 and / or the physiological function of the heart 102, the sensing circuitry 304 can adjust the sensing vectors and / or select sensing vectors accordingly to maintain the quality of the sensed signals.

[0060] In some examples, the sensing circuitry 304 is configured to detect events (e.g., depolarizations) within the cardiac electrical signals and / or cardiac conditions (e.g., the presence of arrhythmias, tachycardia, etc.) and provide an indication of the event and / or cardiac condition to the processing circuitry 310. In this manner, the processing circuitry 310 can determine the timing of atrial depolarization and ventricular depolarization and control the delivery of cardiac pacing (e.g., AV synchronous cardiac pacing) based on the timing. The processing circuitry 310 can select pacing vectors within the 3D coordinate system defined by the electrodes 112, 113, and 114. The processing circuitry 310 can include any one or more of the following: a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), discrete logic circuitry, or any other processing circuitry configured to provide the functionality attributed to the processing circuitry 310, which can be embodied herein as firmware, hardware, software, or any combination thereof.

[0061] In some examples, the sensing circuitry 304 may sense signals along each sensing vector based on signals sensed from electrodes 112 and 114 along corresponding reference axes. The sensing circuitry 304 may then combine the sensed signals to determine the signals sensed along the sensing vectors. For each sensing vector, each sensed signal may have a different gain factor for determining the sensed signal. For example, a signal from a reference axis defined by the proximal electrode 114 and the reference electrode 113 may have a different gain factor than a signal from a reference axis defined by the distal electrode 112 and the reference electrode 113. In some examples, each sensing vector is associated with and sensed by a dedicated sensing channel within the sensing circuitry 304. In some examples, each sensing vector may be switched, e.g., via the switching circuitry 302, to a sensing channel within the sensing circuitry 302 that has limited functionality.

[0062] The sensor 308 may include one or more sensing elements that convert patient physiological activity into an electrical signal to sense the value of a corresponding patient parameter. The sensor 308 may include one or more accelerometers, optical sensors, chemical sensors, temperature sensors, pressure sensors, or any other type of sensor. The sensor 308 may output a patient parameter value that may be used as feedback to control the sensing and delivery of therapy by the device 104.

[0063] The telemetry circuitry 312 supports wireless communication between the device 104 and an external programmer ( Figure 3 not shown) or another computing device under the control of the processing circuitry 310. The processing circuitry 310 of the device 104 may receive updates to operating parameters from the computing device and provide collected data, such as sensed cardiac activity or other patient parameters, via the telemetry circuitry 312. The telemetry circuitry 312 may accomplish communication via radio frequency (RF) communication techniques (e.g., via an antenna (not shown)).

[0064] The power supply 316 delivers operating power to the various components of the device 104. The power supply 316 may include a rechargeable or non-rechargeable battery and a power generation circuit to produce the operating power. Recharging may be accomplished via a near-side inductive interaction between an external charger and an inductive charging coil within the device 104.

[0065] Figure 4FIG. 0 is a conceptual diagram of the device 104 implanted at the target implantation region 106. The distal electrode 112 may be inserted (e.g., in a manner similar to rotating and advancing a threaded screw) such that tissue engages the elongate body 210. When the elongate body 210 engages tissue, the distal electrode 112 pierces into the tissue at the target implantation region 106 and advances through the atrial myocardium 406 and the central fibrous body 402 to position the distal electrode 112 in the ventricular myocardium 108, as Figure 4 shown. In some examples, the distal electrode 112 penetrates into the interventricular septum. In some examples, the distal electrode 112 does not completely penetrate the endocardial surface or the epicardial surface of the ventricle.

[0066] In some examples, a longitudinal force is provided, such as by manual pressure applied to the proximal end 204 of the housing via a deployment tool, to pierce the heart tissue at the target implantation region 106. In some examples, actuation of the deployment tool causes the elongate body 210, configured as a helix, to rotate about the longitudinal axis 208. Rotation of the elongate body 210 about the longitudinal axis 208 causes the distal electrode 112 to advance through the atrial myocardium 406 and the central fibrous body 402 to position the distal electrode 112 in the ventricular myocardium 108, as Figure 4 shown.

[0067] As the distal electrode 112 is advanced into the tissue, the distance between the distal end 202 and the atrial endocardium 404 decreases until the reference electrode 113 and the proximal electrode 114 contact and may bear against the surface of the atrial endocardium 404. The electrodes 113 and 114 may bear against the surface of the atrial endocardium 404 and compress the wall tissue. Compression of the wall tissue may increase the friction between the electrodes 113 and 114 and the wall tissue and prevent rotation of the distal electrode 112 due to movement of the tissue of the heart 102 (e.g., movement of the ventricular myocardium 108, atrial myocardium 406, central fibrous body 402, etc.). The electrodes 113 and 114 bearing against the heart tissue may cause the heart tissue to engage the electrodes 113 and 114. Retraction of the electrodes 113 and 114 from the surface of the atrial endocardium 404 may be prevented by the distal electrode 112.

[0068] In some pacing applications, the target implantation region 106 is along the atrial endocardium 404, substantially at the AV node and the lower part of the His bundle. In some examples, the target implantation region 106 is located within the Koch triangle. The distal electrode 112 can have a length that penetrates the atrial endocardium 404 in the target implantation region 106, passes through the central fibrous body 402, and enters the ventricular myocardium 108 without penetrating the ventricular endocardial surface. In some examples, when the entire length of the distal electrode 112 is fully advanced into the target implantation region 106, the distal electroactive region 216 rests within the ventricular myocardium 108, and the reference electrode 113 and the proximal electrode 114 are positioned in close contact with the atrial endocardium 404. In various examples, the distal electrode 112 can extend from the distal end 204 of the housing by about 3 mm to 12 mm. In some examples, the distal electrode 112 can extend from the housing 202 by a distance of at least 3 millimeters (mm), and in various examples, at least 3 mm but less than 20 mm, less than 15 mm, less than 10 mm, or less than 8 mm. The diameter of the distal electrode 112 can be less than 2 mm, and can be 1 mm or less, or even 0.6 mm or less.

[0069] Figure 5 A, Figure 6 and Figure 7 are partial views of a device according to one or more aspects of the present disclosure Figures 1 to 4 viewed from different perspectives. Figure 5 is a partial view of a device 104 Figure 1 including a distal end 110. The housing 200 includes a head 500. In some examples, the head 500 can be separate from or integral with the housing 200, and can be made of the same or different material as the housing 200. In some examples, as Figure 5 shown, the distal end 202 of the housing 200 includes, for example, a peripheral region surrounding the distal electrode 112. The reference electrode 113 and the proximal electrode 114 can be disposed in the peripheral region of the distal end 202. Each proximal electrode among the proximal electrodes 114 is spaced apart from the reference electrode 113 to define a reference axis. For example, the proximal electrode 114A and the reference electrode 113 define a reference axis 506B (also referred to as "X-axis 506B"), and the proximal electrode 114B and the reference electrode 113 define a reference axis 506C (also referred to as "Y-axis 506C"). Similarly, the distal electrode 112 can define a reference axis 506A (also referred to as "Z-axis 506C") with the reference electrode 113.

[0070] In some examples, the elongate body 210 can define a helix and / or a coil that defines a varying outer diameter at a distal end of the elongate body 210 than at a proximal end of the elongate body 210, e.g., to place the distal electrode 112 at the same radial position relative to the longitudinal axis 208 as the reference electrode 113. By placing the distal electrode 112 at the same radial position as the reference electrode 113, the distal electrode 112 will not sense an overlapping signal component along the reference axis 506A. The reference electrode 113 and the proximal electrode 114 can define a height that extends distally away from the distal end 202 of the housing 200, e.g., to contact tissue of the heart 102. Each of the electrodes 113 and 114 can all have the same height, can have the same height as the other of the electrodes 113 and 114, or can all have different heights, e.g., to define orthogonal reference axes 506. For example, if the distal electrode 112 is radially offset from the reference electrode 113 (e.g., the distal electrode 112 is located at the same circumferential position as the reference electrode 113), the heights of the reference electrode 113 and the proximal electrode 114 can be different, e.g., to make each of the reference axes 506A to 506C (collectively referred to as "reference axes 506") orthogonal to each other reference axis in the reference axes 506.

[0071] In some examples, as Figure 5 shown, the reference axes 506 define a 3D coordinate system. Each of the reference axes 506 can be orthogonal to each other reference axis in the reference axes 506. For example, the reference axis 506A is orthogonal to the reference axis 506B and the reference axis 506C, and vice versa. The device 104 can sense electrical signal components of the electrical signals in the heart 102 along each of the reference axes 506. The device 104 can determine the sensed electrical signal along the sensing vector based on the sensed electrical signal components. Based on the sensed electrical signal along the sensing vector, the device 104 can determine the electrical signal within the heart 102 and / or whether to deliver cardiac pacing therapy to one or more chambers of the heart 102.

[0072] Inflammation of the patient's tissue can be caused by interaction with the device 104. For example, penetration of the distal electrode 112 into the tissue and / or contact between the tissue and the reference electrode 113 and / or the proximal electrode 114 can cause inflammation of the tissue. Inflammation of the patient's tissue near the electrodes can result in a higher threshold for the stimulation delivered to the tissue to activate or capture the tissue. The higher capture threshold can in turn increase the consumption of the power source of the device 104 associated with the delivery of the stimulation.

[0073] In some examples, device 104 includes, for example, one or more steroid eluting elements 504 (collectively referred to as "steroid eluting elements 504") disposed on the distal end 202. The steroid can reduce inflammation of the patient's tissue caused by interaction with the IMD. The steroid eluting element 504 can be configured to elute one or more steroids into the tissue near the element 504 over time. In some examples, the steroid eluting element 504 includes one or more monolithic controlled release devices (MCRD). In some examples, the steroid eluting element 504 can be a therapeutic substance dispensing device.

[0074] In some examples, device 104 includes one or more steroid eluting elements 504 configured to elute one or more steroids into the tissue near the distal electrode 112. The steroid eluting element 504 can be disposed within a recess defined by the reference electrode 113 and / or the proximal electrode 114. In some examples, the steroid eluting element 504 can be disposed at the center of the face 502, for example, within an annulus defined by the elongate body 210.

[0075] Figure 6 is a partial top view of device 104 and face 502. As Figure 6 shown, the X-axis 506B and the Y-axis 506C are separated by an angle 602. Device 104 can sense an electrical signal (e.g., an atrial signal) along a sensing vector 604. The sensing vector 604 can be defined by components sensed by the proximal electrodes 114A and 114B along the X-axis 506B and the Y-axis 506C, respectively. Using the sensing vector 604 by the sensing circuitry 304 can prevent sensing of overlapping signals (e.g., ventricular signals), thereby simplifying detection of, for example, electrogram (EGM) from the atria of the heart 102. For example, sensing by the sensing circuitry 304 and via the proximal electrode 114 along the sensing vector 604 prevents sensing of electrical signals in the direction of the Z-axis 506A. In some examples, the X-axis 506B and the Y-axis 506C can be orthogonal to each other, for example, to prevent overlapping signals of electrical signals sensed by each of the electrodes 114 along other axes of the reference axis 506. For example, when the X-axis 506B and the Y-axis 506C are orthogonal, the proximal electrode 114A may not sense an electrical signal in the direction of the Y-axis 506C. In such an example, the angle 602 is 90 degrees. In some examples, the X-axis 506B and the Y-axis 506C are substantially orthogonal (e.g., the angle 602 is between about 80 degrees and 100 degrees), for example, to minimize overlapping signals sensed by the electrode 114 along the Z-axis 506A.

[0076] Figure 7 is a side view of the distal end 204 of device 104. As Figure 7As shown, the Z-axis 506A can be at an angle 702 from the X-axis 506B and at an angle 704 from the Y-axis 506C. In some examples, the Z-axis 506A can be orthogonal to both the X-axis 506B and the Y-axis 506C, for example, to prevent the distal electrode 112 from sensing electrical signals along the X-axis 506B and / or the Y-axis 506C. In such examples, the angles 702 and 704 are 90 degrees. In some examples, the X-axis 506B, the Y-axis 506C, and the Z-axis 506A are substantially orthogonal to each other. In such examples, the angles 702 and 704 are between approximately 80 degrees and 100 degrees.

[0077] In some examples, as Figure 7 shown, each of the reference electrode 113 and the proximal electrode 114 is offset from the face 502 by a distance 706, for example, to improve contact with the wall tissue of the first chamber and / or the sensing and / or pacing capabilities of the electrodes 113 and 114. The distance 706 can be between 0.34556 millimeters (mm) and approximately 1.27 mm (e.g., between approximately 0.014 inches (in) and approximately 0.05 in). Each of the electrodes 113 and 114 can be offset from the face 502 by the same distance 706, two or more of the electrodes 113 and 114 can be offset from the face 502 by the same distance 706, or each of the electrodes 113 and 114 can be offset from the face 502 by different distances within the range of values of the distance 706 as described above.

[0078] Figure 8 is a flow chart showing an exemplary process for delivering cardiac pacing therapy to a patient's heart 102 via an exemplary device of any of the Figures 1 to 7 figures. The technique will be described with reference to the device 104 ( Figure 1 ), but those of ordinary skill in the art will understand that the technique can be performed with reference to another implantable medical lead or other medical device. Additionally, although the exemplary process is described primarily with reference to the atrium of the heart 102 as the first chamber and the ventricle of the heart 102 as the second chamber Figure 8 of the exemplary process, the exemplary processes described herein can be applied to other combinations of chambers of the heart 102. The exemplary processes described herein can be similarly performed on a 2D coordinate system, where the device 104 has one proximal electrode 114 (e.g., as Figure 8 shown). Figure 2B shown).

[0079] The device 104 may select a sensing vector (802) within a 3D coordinate system defined by a distal electrode 112, a reference electrode 113, and a proximal electrode 114 of an implantable medical device (IMD) 104 (also referred to herein as "device 104"). Each of the distal electrode 112 and the proximal electrode 114 may define a reference axis 506 (e.g., Z-axis 506A, X-axis 506B, Y-axis 506C) with the reference electrode 113 and may detect a signal component of an electrical signal along the corresponding reference axis 506. For example, the distal electrode 112 and the reference electrode 113 define the Z-axis 506A and detect the signal component of the electrical signal in the heart 102 (e.g., in the target implantation region 106) along the Z-axis 506A. The reference axes 506 together define a 3D coordinate system that includes a region containing the target implantation region 106, the distal electrode 112, the reference electrode 113, and the proximal electrode 114. Each of the reference axes 506 may be orthogonal to each other reference axis 506, e.g., to prevent either of the electrodes 112 and 114 from sensing overlapping signals along the other reference axes 506. For example, when the Z-axis 506A is orthogonal to the X-axis 506B and the Y-axis 506C, the distal electrode 112 only senses the signal component of the electrical signal along the Z-axis 506A and does not sense the signal component of the electrical signal along the X-axis 506B or the Y-axis 506C. By using the 3D coordinate system, the device 104 may sense an electrical signal within the target implantation region 106 and determine characteristics of the electrical signal (e.g., EGM, signal type (i.e., atrial signal or ventricular signal)) without requiring the device 104 to be implanted in the target implantation region 106 in a specific orientation.

[0080] The device 104 may sense electrical signals (804) from one or more chambers of the heart 102 along sensing vectors. Each sensing vector may be a combination of sensed signal components from two or more of the distal electrode 112 and the proximal electrodes 114. For example, the sensing vector may be a combination of sensed signal components from the distal electrode 112 and the proximal electrode 114A, from the proximal electrode 114A and the proximal electrode 114B, or from the distal electrode 112 and the proximal electrode 114B. The sensing circuitry 304 may detect and represent any sensed signal within a 3D coordinate system based on two or more sensing vectors. The sensing circuitry 304 may sense electrical signals along some sensing vectors to sense only the electrical signals from a particular chamber of the heart 102. For example, when the device 104 is implanted within an atrium (e.g., RA) of the heart 102, the sensing circuitry 304 may sense electrical signals from a ventricle (e.g., LV) of the heart 102 via sensing vectors along the Z-axis 506A and the X-axis 506B. Similarly, the sensing circuitry 304 may sense electrical signals from an atrium of the heart 102 via sensing vectors along the X-axis 506B and the Y-axis 506C. The sensing circuitry 304 may sense electrical signals along one or more sensing vectors to determine the location (e.g., relative to one or more of the distal electrode 112, the reference electrode 113, and the proximal electrodes 114), amplitude, and / or frequency of the electrical signals within the heart 102. The sensing circuitry 304 may combine the electrical signals sensed along one or more sensing vectors into a combined electrical signal corresponding to the actual electrical signal within the heart 102.

[0081] Based on the sensed electrical signals (e.g., EGM), the device 104 (e.g., the sensing circuitry 304 and / or the processing circuitry 310) may determine the presence of an event or a cardiac condition (806). Cardiac conditions may include, but are not limited to, arrhythmias, tachycardia, etc. Events may include, but are not limited to, atrial depolarization, ventricular depolarization, etc. The device 104 may determine the presence of an event or a cardiac condition and, based on that determination, determine whether to deliver cardiac pacing therapy to one or more chambers of the heart 102. In some examples, the sensing circuitry 304 of the device 104 makes the determination and transmits the result to the processing circuitry 310 to determine whether to deliver cardiac pacing therapy and / or the parameters of the cardiac pacing therapy. In some examples, the sensing circuitry 304 transmits the sensed electrical signals to the processing circuitry 310, and the processing circuitry 310 makes the determination based on the sensed electrical signals.

[0082] Based on determining that the device 104 should deliver cardiac pacing therapy to one or more chambers of the heart 102, the processing circuitry 310 may determine a pacing vector (808) within the 3D coordinate system. The pacing vector may connect a target location for cardiac pacing to one or more of the electrodes 112, 113, and 114. After the device 104 selects the pacing vector, the processing circuitry 310 may cause the signal generation circuitry 306 to deliver cardiac pacing therapy (810) to one or more chambers of the heart 102 along the pacing vector via one or more of the proximal electrodes 112 and / or the proximal electrodes 114. For example, the device 104 may deliver cardiac pacing therapy to the ventricular myocardium 108 via the distal electrode 112 and the reference electrode 113. In another example, the device 104 may deliver cardiac pacing therapy to the atrial myocardium 406 via one or more of the proximal electrodes 114 and the reference electrode 113. In some examples, the device 104 selects the optimal proximal electrode among the proximal electrodes 114 at least partially based on the pacing vector and / or the sensed electrical signals (e.g., based on the sensed electrical signal components, based on the electrical signals sensed along the sensing vector, or based on the combined electrical signals). The device 104 may then deliver cardiac pacing to one or more chambers of the heart 102 via the optimal proximal electrode. In some examples, the device 104 may deliver cardiac pacing therapy to one or more chambers of the heart 102 (e.g., to the LA) via two proximal electrodes 114 simultaneously. In some examples, the device 104 may deliver cardiac pacing therapy alternately from the proximal electrodes 114.

[0083] It should be understood that the various aspects disclosed herein may be combined in combinations different from those specifically presented in the specification and the drawings. It should also be understood that, depending on the example, certain acts or events of any of the processes or methods described herein may be performed in a different order, may be added, combined, or omitted entirely (e.g., not all of the described acts or events may be required to perform the techniques). Additionally, although certain aspects of the present disclosure are described as being performed by a single module or unit for clarity, it should be understood that the techniques of the present disclosure may be performed by a combination of units or modules associated with, for example, a medical device.

[0084] In one or more examples, the described techniques may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. The computer-readable medium may include a non-transitory computer-readable medium that corresponds to a tangible medium, such as a data storage medium (e.g., RAM, ROM, EEPROM, flash memory, or any other medium that can be used to store the desired program code in the form of instructions or data structures and that can be accessed by a computer).

[0085] In addition, it should be noted that the systems described herein may not be limited to the treatment of human patients. In alternative examples, the systems may be implemented in non-human patients such as primates, canines, equines, porcines, and felines. These other animals may undergo clinical or research treatments that may benefit from the subject matter of this disclosure.

[0086] The instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general-purpose microprocessors, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Thus, as used herein, the term "processor" may refer to any of the foregoing structures or any other physical structure suitable for implementing the described techniques. Additionally, these techniques may be implemented entirely in one or more circuits or logic elements.

[0087] Various embodiments have been described. These and other embodiments are within the scope of the appended claims.

[0088] Example 1. A device, comprising: an elongate housing extending from a proximal end of the housing to a distal end of the housing, the elongate housing configured to be fully implanted within a first chamber of the heart, the first chamber of the heart having wall tissue; a distal electrode extending distally from the distal end of the elongate housing, the distal electrode configured to penetrate into wall tissue of a second chamber of the heart that is separated from the first chamber of the heart; a reference electrode extending from the distal end of the elongate housing; one or more proximal electrodes extending from the distal end of the elongate housing, wherein the one or more proximal electrodes are separated from the distal electrode and the reference electrode; a sensing circuitry located within the elongate housing and coupled to the distal electrode, the reference electrode, and the one or more proximal electrodes; and a processing circuitry located within the elongate housing, the processing circuitry configured to control the sensing circuitry to sense electrical signals of the heart via the distal electrode, the reference electrode, and the one or more proximal electrodes.

[0089] Example 2. The device according to Example 1, wherein the first chamber comprises an atrium of the heart and wherein the second chamber comprises a ventricle of the heart.

[0090] Example 3. The device according to any one of Examples 1 and 2, wherein each of the reference electrode and the one or more proximal electrodes is configured to remain in contact with the wall tissue of the first chamber without penetrating the wall tissue of the first chamber.

[0091] Example 4. The device according to any one of Examples 1 to 3, wherein the one or more proximal electrodes include a first proximal electrode, wherein the distal electrode and the reference electrode define a distal axis, wherein the first proximal electrode and the reference electrode define a proximal axis, and wherein the processing circuitry is configured to sense the electrical signal of the heart along a sensing vector within a plane defined by the distal axis and the proximal axis.

[0092] Example 5. The device according to Example 4, wherein the distal axis is orthogonal to the proximal axis, and wherein the distal axis extends distally away from the distal end of the housing.

[0093] Example 6. The device according to any one of Examples 1 to 5, wherein the distal electrode and the reference electrode define a first axis, wherein the first proximal electrode among the one or more proximal electrodes and the reference electrode define a second axis, and wherein the second proximal electrode among the one or more proximal electrodes and the reference electrode define a third axis.

[0094] Example 7. The device according to Example 6, wherein the processing circuitry is configured to: cause a sensing circuitry within the elongate housing to perform at least two of the following along the sensing vector: sense a first electrical signal via the first axis, sense a second electrical signal via the second axis, and sense a third electrical signal via the third axis; determine a fourth electrical signal based on the first electrical signal, the second electrical signal, and the third electrical signal among the at least two according to the sensing vector; and control delivery of cardiac pacing therapy to one or more of the first chamber or the second chamber based on the fourth electrical signal.

[0095] Example 8. The device according to Example 7, wherein the processing circuitry is configured to determine the fourth electrical signal based on the first electrical signal, the second electrical signal, the third electrical signal, and the sensing vector, wherein the sensing vector is a three-dimensional (3D) vector with respect to the first axis, the second axis, and the third axis.

[0096] Example 9. The device according to any one of Examples 6 to 8, wherein the first axis, the second axis, and the third axis are orthogonal to each other.

[0097] Example 10. The device according to any one of Examples 1 to 9, wherein each of the distal electrode and the one or more proximal electrodes is electrically connected to a signal generation circuitry within the housing through a corresponding feedthrough assembly.

[0098] Example 11. The apparatus according to any one of Examples 1 to 10, wherein the processing circuitry is configured to, before the distal electrode penetrates the wall tissue of the first chamber: cause the sensing circuitry to sense an electrical signal via the distal electrode, the reference electrode, and the one or more proximal electrodes; and determine a position and orientation of the apparatus within the first chamber of the heart based on the sensed electrical signal.

[0099] Example 12. The apparatus according to any one of Examples 1 to 11, wherein the distal electrode includes an elongated body extending distally from the distal end of the elongated housing, the elongated body including: a helix having one or more coils; and a distal end configured to pierce the wall tissue of the first chamber and extend into the wall tissue of the second chamber.

[0100] Example 13. The apparatus according to Example 12, wherein the helix extends from a proximal end to a distal end, and wherein the distal end of the helix defines a larger outer diameter than the proximal end of the helix, and wherein the distal end of the elongated body and the reference electrode define a distal axis substantially parallel to the longitudinal axis.

[0101] Example 14. The apparatus according to any one of Examples 12 and 13, wherein the helix defines a varying diameter along the longitudinal axis of the helix.

[0102] Example 15. The apparatus according to any one of Examples 1 and 14, wherein the distal end of the elongated housing further includes one or more therapeutic substance dispensing devices.

[0103] Example 16. The apparatus according to Example 15, wherein at least one therapeutic substance dispensing device is disposed within a corresponding recess within the one or more proximal electrodes or within the reference electrode.

[0104] Example 17. The apparatus according to any one of Examples 15 and 16, wherein the one or more therapeutic substance dispensing devices include one or more monolithic controlled release devices.

[0105] Example 18. The apparatus according to any one of Examples 15 to 17, wherein the one or more therapeutic substance dispensing devices are disposed around a perimeter of the distal end of the elongated housing.

[0106] Example 19. The apparatus according to any one of Examples 1 to 18, the apparatus further including one or more anti-rotation features disposed on the distal end of the housing and configured to prevent rotation of the apparatus due to movement of the wall tissue of the first chamber.

[0107] Example 20. A method, the method comprising: sensing a plurality of electrical signals from the heart through a sensing circuitry of an implantable medical device (IMD) and via a plurality of combinations of a distal electrode extending distally from a distal end of the elongated housing of the IMD, a reference electrode extending from the distal end of the elongated housing, and one or more proximal electrodes extending from the distal end of the elongated housing; determining a combined electrical signal by a processing circuitry of the IMD based on the sensed electrical signals and a sensing vector; and delivering cardiac pacing therapy to one or more chambers of the heart by one or more of the distal electrode and the one or more proximal electrodes based on the combined signal, wherein the distal electrode is configured to penetrate into the wall tissue of the second chamber, and wherein the one or more proximal electrodes and the reference electrode are configured to remain in contact with the wall tissue of the first chamber without the one or more proximal electrodes penetrating the wall tissue of the first chamber.

[0108] Example 21. The method according to Example 20, wherein the distal electrode and the reference electrode define a first axis, wherein a first proximal electrode among the one or more proximal electrodes and the reference electrode define a second axis, and wherein a second proximal electrode among the one or more proximal electrodes and the reference electrode define a third axis.

[0109] Example 22. The method according to Example 21, wherein sensing the electrical signals from the heart comprises: sensing a first electrical signal by the sensing circuitry via the first axis, a second electrical signal via the second axis, and a third electrical signal via the third axis.

[0110] Example 23. The method according to Example 22, wherein determining the combined signal comprises: determining the combined signal by the processing circuitry based on the sensing vector and a combination of two or more of the first electrical signal, the second electrical signal, and the third electrical signal, wherein the sensing vector is a three-dimensional (3D) vector with respect to the first axis, the second axis, and the third axis.

[0111] Example 24. The method according to any one of Examples 21 to 23, wherein the first axis, the second axis, and the third axis are orthogonal to each other.

[0112] Example 25. The method according to any one of Examples 21 to 24, wherein the first axis is orthogonal to the distal end of the elongated housing.

[0113] Example 26. The method according to any one of Examples 21 to 25, wherein delivering the cardiac pacing therapy to the one or more chambers of the heart comprises: determining, by the processing circuitry, based on the combined signal, whether to deliver the cardiac pacing therapy to the first chamber of the heart; and based on determining to deliver the cardiac pacing therapy to the first chamber, delivering the cardiac pacing therapy to the wall tissue of the first chamber via one or more of the first proximal electrode and the second proximal electrode.

[0114] Example 27. The method according to Example 26, wherein delivering the cardiac pacing therapy to the first chamber further comprises alternately delivering the cardiac pacing therapy to the wall tissue of the first chamber via the first proximal electrode and the second proximal electrode.

[0115] Example 28. The method according to any one of Examples 20 to 27, wherein the distal electrode comprises an elongate body extending distally from the distal end of the elongate housing, the elongate body comprising: a helix having one or more coils; and a distal end configured to pierce the wall tissue of the first chamber and extend into the wall tissue of the second chamber.

[0116] Example 29. A device comprising: an elongated housing extending from a proximal end to a distal end, the elongated housing configured to be fully implanted within a first chamber of the heart; a distal electrode extending distally from the distal end of the elongated housing, the distal electrode configured to penetrate into the wall tissue of a second chamber of the heart, the second chamber of the heart being separate from the first chamber of the heart; two proximal electrodes extending from the distal end of the elongated housing, wherein the two proximal electrodes are separated from the distal electrode, and wherein each of the two proximal electrodes is configured to maintain contact with the wall tissue of the first chamber without penetrating the wall tissue of the first chamber; a reference electrode extending from the distal end of the elongated housing and separated from the distal electrode and the two or more proximal electrodes, the reference electrode configured to: define a first axis with the distal electrode; define a second axis with a first proximal electrode of the two proximal electrodes; and define a third axis with a second proximal electrode of the two proximal electrodes; a sensing circuitry disposed within the elongated housing; a signal generation circuitry disposed within the elongated housing; and a processing circuitry located within the elongated housing, the processing circuitry configured to: cause the sensing circuitry to sense electrical signals from the heart along at least two of the first axis, the second axis, and the third axis via the distal electrode, the first proximal electrode, and the second proximal electrode, respectively; determine a combined signal based on the sensed electrical signals and a three-dimensional (3D) sensing vector; and cause the signal generation circuitry to deliver cardiac pacing therapy to the heart based on the combined electrical signal via one or more of the distal electrode, the first proximal electrode, or the second proximal electrode.

[0117] Example 30. The device according to Example 29, wherein the processing circuitry is further configured to: determine a waveform of the combined signal; and cause the signal generation circuitry to deliver the cardiac pacing therapy to the heart based on the determined waveform.

[0118] Example 31. The device according to any one of Examples 29 and 30, wherein the processing circuitry is further configured to determine the presence of a cardiac condition based on the combined signal.

[0119] Example 32. The device according to Example 31, wherein the cardiac condition includes tachycardia.

[0120] Example 33. The device according to any one of Examples 29 to 32, wherein the first chamber includes an atrium of the heart, and wherein the second chamber includes a ventricle of the heart.

[0121] Example 34. The device according to any one of Examples 29 to 33, wherein the 3D sensing vector is defined with respect to the first axis, the second axis, and the third axis.

[0122] Example 35. The device according to any one of Examples 29 to 34, wherein each of the distal electrode and the two proximal electrodes is electrically connected to the signal generation circuitry via a corresponding feedthrough assembly.

[0123] Example 36. The device according to any one of Examples 29 to 35, wherein the first axis, the second axis, and the third axis are orthogonal to each other.

[0124] Example 37. The device according to any one of Examples 29 to 36, wherein the distal electrode includes an elongate body extending distally from the distal end of the elongate housing, the elongate body including: a helix having one or more coils; and a distal end configured to pierce the wall tissue of the first chamber and extend into the wall tissue of the second chamber.

[0125] Example 38. The device according to Example 37, wherein the helix extends from a proximal end to a distal end, wherein the helix defines a greater outer diameter at the distal end than at the proximal end, and wherein the distal end of the elongate body and the reference electrode define a distal axis that is substantially parallel to the longitudinal axis.

[0126] Example 39. The device according to Example 38, wherein the distal end of the helix is disposed at the same circumferential and radial position with respect to the longitudinal axis as the reference electrode.

[0127] Example 40. The device according to any one of Examples 37 to 39, wherein the helix defines a varying diameter along the longitudinal axis of the helix.

Claims

1. An apparatus, the apparatus comprising: An elongate housing extending from a proximal end of the housing to a distal end of the housing, the elongate housing configured to be fully implanted within a first chamber of the heart, the first chamber of the heart having wall tissue; A distal electrode extending distally from the distal end of the elongate housing, the distal electrode configured to penetrate into wall tissue of a second chamber of the heart that is separated from the first chamber of the heart; A reference electrode extending from the distal end of the elongate housing; One or more proximal electrodes extending from the distal end of the elongate housing, wherein the one or more proximal electrodes are separated from the distal electrode and the reference electrode; A sensing circuitry located within the elongate housing and coupled to the distal electrode, the reference electrode, and the one or more proximal electrodes; And A processing circuitry located within the elongate housing, the processing circuitry configured to control the sensing circuitry to sense electrical signals of the heart via the distal electrode, the reference electrode, and the one or more proximal electrodes.

2. The apparatus according to claim 1, wherein the first chamber comprises an atrium of the heart, and wherein the second chamber comprises a ventricle of the heart.

3. The apparatus according to any one of claims 1 and 2, wherein the reference electrode and each proximal electrode of the one or more proximal electrodes are configured to maintain contact with the wall tissue of the first chamber without penetrating the wall tissue of the first chamber.

4. The apparatus according to any one of claims 1 to 3, wherein the one or more proximal electrodes include a first proximal electrode, wherein the distal electrode and the reference electrode define a distal axis, wherein the first proximal electrode and the reference electrode define a proximal axis, and wherein the processing circuitry is configured to sense the electrical signals of the heart along a sensing vector within a plane defined by the distal axis and the proximal axis.

5. The apparatus according to claim 4, wherein the distal axis is orthogonal to the proximal axis, and wherein the distal axis extends distally away from the distal end of the housing.

6. The apparatus according to any one of claims 1 to 5, wherein the distal electrode and the reference electrode define a first axis, wherein a first proximal electrode of the one or more proximal electrodes and the reference electrode define a second axis, and wherein a second proximal electrode of the one or more proximal electrodes and the reference electrode define a third axis.

7. The apparatus according to claim 6, wherein the processing circuitry is configured to: Cause the sensing circuitry within the elongate housing to perform at least two of the following along the sensing vector: sense a first electrical signal via the first axis, sense a second electrical signal via the second axis, and sense a third electrical signal via the third axis; Determine a fourth electrical signal based on the sensed vector based on at least two of the first electrical signal, the second electrical signal, and the third electrical signal; and Control the delivery of cardiac pacing therapy to one or more of the first chamber or the second chamber based on the fourth electrical signal.

8. The apparatus of claim 7, wherein the processing circuitry is configured to determine the fourth electrical signal based on the first electrical signal, the second electrical signal, the third electrical signal, and the sensed vector, wherein the sensed vector is a three-dimensional (3D) vector relative to the first axis, the second axis, and the third axis.

9. The apparatus of any one of claims 6 to 8, wherein the first axis, the second axis, and the third axis are orthogonal to each other.

10. The apparatus of any one of claims 1 to 9, wherein each of the distal electrode and the one or more proximal electrodes is electrically connected to a signal generation circuitry within the housing via a corresponding feedthrough assembly.

11. The apparatus of any one of claims 1 to 10, wherein the processing circuitry is configured to, prior to the distal electrode penetrating the wall tissue of the first chamber: Cause the sensing circuitry to sense electrical signals via the distal electrode, the reference electrode, and the one or more proximal electrodes; and Determine the position and orientation of the apparatus within the first chamber of the heart based on the sensed electrical signals.

12. The apparatus of any one of claims 1 to 11, wherein the distal electrode includes an elongate body extending distally from the distal end of the elongate housing, the elongate body including: A helix having one or more coils; and A distal end configured to pierce the wall tissue of the first chamber and extend into the wall tissue of the second chamber.

13. The apparatus of claim 12, wherein the helix extends from a proximal end to a distal end, and wherein the distal end of the helix defines a larger outer diameter than the proximal end of the helix, and wherein the distal end of the elongate body and the reference electrode define a distal axis substantially parallel to the longitudinal axis.

14. The apparatus of any one of claims 12 and 13, wherein the helix defines a varying diameter along the longitudinal axis of the helix.

15. The apparatus of any one of claims 1 to 14, wherein the distal end of the elongate housing further includes one or more therapeutic substance dispensing devices, or one or more anti-rotation features disposed on the distal end of the housing and configured to prevent the apparatus from rotating due to movement of the wall tissue of the first chamber.

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