Method and apparatus for implantation of a medical electrical lead

Abstract

A medical device system is provided for guiding implantation of a medical electrical lead. The system includes processing circuitry configured to receive first patient body image data and second patient body image data and register the first patient body image data and the second patient body image data. The processing circuitry may be further configured to receive a signal from at least one location sensor disposed at a known distance from a feature of a removable outer sheath of a delivery tool configured to deliver an extravascular lead to an implant site of a patient via a non-transvenous pathway. The processing circuitry may determine from the location sensor signal a location of a feature of the removable outer sheath in a coordinate system space corresponding to the second patient body image data.

Description

Ref. No. A0012739US01METHOD AND APPARATUS FOR IMPLANTATION OF A MEDICAL ELECTRICAL LEAD

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 726,178, filed November 27, 2024, the entire content of which is incorporated herein by reference.TECHNICAL FIELD

[0002] This disclosure relates to a system and method for guiding implantation of a medical electrical lead.BACKGROUND

[0003] Medical devices may sense electrophysiological signals from the heart, brain, nerve, muscle or other tissue. Such devices may be implantable, wearable or external devices using implantable and / or surface (skin) electrodes for sensing the electrophysiological signals. In some cases, such devices may be configured to deliver a therapy based on the sensed electrophysiological signals. For example, implantable or external cardiac pacemakers, cardioverter defibrillators, cardiac monitors and the like, sense cardiac electrical signals from a patient’s heart. The medical device may sense cardiac electrical signals from one or more heart chambers and deliver electrical stimulation therapies to the heart using electrodes carried by a medical electrical lead. Other medical devices may deliver therapeutic electrical stimulation pulses via electrodes carried by a medical electrical lead without requiring electrophysiological signal sensing, such as for pain therapy.

[0004] A cardiac pacemaker or cardioverter defibrillator may deliver therapeutic electrical stimulation to the heart via electrodes carried by one or more medical electrical leads coupled to the medical device. A transvenous lead may be advanced through a venous pathway to position electrodes within the patient’s heart. In other instances, a non- transvenous lead may position electrodes outside the patient’s heart, in an extravascular location, for sensing cardiac signals and delivering cardiac stimulation pulses. The electrical stimulation may include cardiac pacing pulses and / or cardioversion or defibrillation (CV / DF) shocks, as examples. In some cases, a medical device may sense cardiac event signals attendant to the intrinsic depolarizations of the myocardium andRef. No. A0012739US01 control delivery of stimulation pulses to the heart based on sensed cardiac event signals. Cardiac signals sensed within a heart chamber using endocardial electrodes carried by transvenous leads, for example, generally have a high signal strength and quality for reliably sensing cardiac event signals, such as ventricular R-waves sensed from within a ventricle or atrial P-waves sensed from within an atrium. Upon detection of an abnormal rhythm, such as bradycardia, tachycardia or fibrillation, an electrical stimulation pulse or pulses may be delivered to restore or maintain a more normal rhythm of the heart. For example, an implantable cardioverter defibrillator (ICD) may deliver pacing pulses to the heart of the patient upon detecting bradycardia or tachycardia or deliver CV / DF shocks to the heart upon detecting tachycardia or fibrillation.SUMMARY

[0005] In general, this disclosure is directed to a medical device system and techniques for guiding implantation of an extravascular (EV) medical electrical lead, referred to herein as an “EV lead,” along a non-transvenous implant pathway. The medical device system includes a delivery tool equipped with one or more location sensors. The delivery tool includes a tunneling rod for advancement along an internal, non-transvenous pathway of a patient’s body. A removable outer sheath carrying the location sensors can be disposed over the tunneling rod. An open lumen of the removable outer sheath is sized to receive the tunneling rod and the EV lead after removal of the tunneling rod from the open lumen to facilitate advancement of the EV lead to the implant site via the open lumen of the removable outer sheath.

[0006] The medical device system includes processing circuitry configured to receive preoperative patient body image data of a patient body region in which the EV lead is to be implanted. The preoperative patient body image data may include imaging data corresponding to anatomical structures around and in the vicinity of the EV lead implant site, e.g., including body tissue or an organs that is being electrically stimulated by or producing electrical signals sensed by the EV lead. The processing circuitry is further configured to receive intraoperative patient body image data that can be registered to the preoperative patient body image data. The processing circuitry can be configured to determine the location of the delivery tool location sensors in a coordinate system corresponding to the intraoperative patient body image data. A display unit may receiveRef. No. A0012739US01 the delivery tool location information and the registered patient body image data for generating a display of the delivery tool position or portion thereof relative to a graphical rendering of at least a portion of the preoperative patient body image data to guide a clinician during the EV lead implant procedure.

[0007] In one example, the disclosure provides a medical device system including a delivery tool configured to deliver an extravascular lead to an implant site of a patient via a non-transvenous pathway. The delivery tool may include a removable outer sheath configured to be disposed over a tunneling rod. The removable outer sheath may have an outer wall extending from a sheath proximal end to a sheath distal end and an open lumen defined by the outer wall, the open lumen extending from the sheath proximal end for receiving the tunneling rod, the open lumen further configured to receive the extravascular lead after the tunneling rod is removed from the removable outer sheath. The removable outer sheath may include at least one location sensor disposed at a known distance from a feature of the removable outer sheath. The medical device system may further include processing circuitry configured to receive first patient body image data, receive second patient body image data, and register the first patient body image data and the second patient body image data. The processing circuitry may be further configured to receive a signal from the at least one location sensor determine, from the location sensor signal, a first location of the feature of the removable outer sheath in a coordinate system space corresponding to the second patient body image data and provide to a display unit the first location of the feature of the removable outer sheath and the registered first patient body image data and the second patient body image data for displaying, by the display unit, a first location representation of the first location of the feature of the removable outer sheath relative to a graphical rendering of at least a portion of the first patient body image data.In another example, the disclosure provides a method including

[0008] In another example, the disclosure provides a method including receiving first patient body image data, receiving second patient body image data and registering the first patient body image data and the second patient body image data. The method may further include receiving a signal from the at least one location sensor disposed at a known distance from a feature of a removable outer sheath of a delivery tool. The delivery too configured to deliver an extravascular lead to an implant site of a patient via a non-Ref. No. A0012739US01 transvenous pathway. The removable outer sheath having an outer wall extending from a sheath proximal end to a sheath distal end and an open lumen defined by the outer wall. The open lumen extending from the sheath proximal end for receiving a tunneling rod. The open lumen is further configured to receive the extravascular lead after the tunneling rod is removed from the removable outer sheath. The method further including determining from the location sensor signal a first location of the feature of the removable outer sheath in a coordinate system space corresponding to the second patient body image data and providing to a display unit the first location of the feature of the removable outer sheath and the registered first patient body image data and the second patient body image data for displaying, by the display unit, a first location representation of the first location of the feature of the removable outer sheath relative to a graphical rendering of at least a portion of first patient body image data.

[0009] In yet another example, the disclosure provides a non-transitory computer readable medium storing a set of instructions that, when executed by processing circuitry of a medical device system, cause the medical device system to receive first patient body image data, receive second patient body image data and register the first patient body image data and the second patient body image data. The instructions may further cause the medical device system to receive a signal from the at least one location sensor that is disposed at a known distance from a feature of a removable outer sheath of a delivery tool. The delivery tool is configured to deliver an extravascular lead to an implant site of a patient via a non-transvenous pathway. The removable outer sheath has an outer wall extending from a sheath proximal end to a sheath distal end and an open lumen defined by the outer wall. The open lumen can extend from the sheath proximal end for receiving a tunneling rod. The open lumen is further configured to receive the extravascular lead after the tunneling rod is removed from the removable outer sheath. The instructions may further cause the medical device system to determine from the location sensor signal a first location of the feature of the removable outer sheath in a coordinate system space corresponding to the second patient body image data and provide to a display unit the first location of the feature of the removable outer sheath and the registered first patient body image data and the second patient body image data for displaying, by the display unit, a first location representation of the first location of the feature of the removable outerRef. No. A0012739US01 sheath relative to a graphical rendering of at least a portion of first patient body image data.

[0010] This summary is intended to provide an overview of the subject matter described in this disclosure. It is not intended to provide an exclusive or exhaustive explanation of the apparatus and methods described in detail within the accompanying drawings and description below. Further details of one or more examples are set forth in the accompanying drawings and the description below.BRIEF DESCRIPTION OF DRAWINGS

[0011] FIG. 1 illustrates a medical device system for facilitating navigation and positioning of an EV lead at a target implant site according to some examples.

[0012] FIG. 2 is a diagram of the delivery tool shown in FIG. 1 according to some examples.

[0013] FIGs. 3A-3C are conceptual diagrams of a patient implanted with an ICD system including an EV lead.

[0014] FIG. 4 is a flow chart of a method for implanting an EV lead using the medical device system of FIG. 1 according to some examples.

[0015] FIG. 5 is a flow chart of a method for implanting an EV lead using the medical device system of FIG. 1 according to another example.

[0016] FIG. 6 is an illustration of a graphical display be that may be presented to a clinician by the display unit of FIG. 1 according to the techniques disclosed herein.

[0017] FIG. 7 is a diagram of a graphical display that may be presented by the display unit of FIG. 1 according to another example.DETAILED DESCRIPTION

[0018] In general, this disclosure describes a medical device system and techniques for navigating a medical electrical lead to an implant position for providing cardiac electrical signal sensing and / or cardiac electrical stimulation pulse delivery. The medical electrical lead may be delivered non-transvenously to an extra-vascular (EV) implant site using the system and techniques disclosed herein. As used herein, the term “extra-vascular” refers to a position outside the blood vessels and heart of a patient and may be outside the pericardium surrounding the heart of the patient in some examples. The extra-vascularRef. No. A0012739US01 lead may be positioned extra-thoracically (outside the ribcage and sternum) or intra- thoracically (e.g., beneath the ribcage or sternum) in various examples.

[0019] A medical electrical lead carrying electrodes for sensing electrophysiological signals, such as electrocardiograms (ECGs), neurological signals, or electromyograms (EMGs), may be advanced extra-venously to a target implant site that enables reliable sensing of the electrophysiological signals. Additionally or alternatively, the electrodes carried by the medical electrical lead advanced to an EV implant site may be used for delivering electrical stimulation pulses to an excitable tissue. The medical electrical lead may be advanced via minimally invasive procedures through a small incision without line of sight view of the pathway of the medical electrical lead. Visualization of the lead pathway by medical imaging can be limited due to anatomical structures that can block the view of the lead or the inability to view the lead relative to anatomical structures in three dimensions. During the implant procedure, improper advancement of the medical electrical lead could result in unintended injury or damage to patient body tissue and / or suboptimal lead placement for sensing electrophysiological signals or delivering electrical stimulation pulses. The medical device system and techniques disclosed herein provide guidance during a surgical procedure for implanting an EV lead at a target implant site that reduces the likelihood of human error and inadvertent tissue injury and promotes reliable sensing and / or therapy delivery performance by the EV lead and a medical device coupled to the EV lead.

[0020] FIG. 1 illustrates a medical device system 10 (also referred to herein as “system” 10) for facilitating navigation and positioning of an EV lead at a target implant site according to some examples. System 10 may include a delivery tool 20 used to deliver and deploy an EV lead (not shown in FIG. 1) at an implant site. The delivery tool 20 may include location sensors, which may be provided as electromagnetic (EM) sensors 26. In other examples, the location sensors of delivery tool 20 are not necessarily limited to being EM sensors but may include accelerometers, gyroscopes, magnetometers, or other sensors producing a signal that can be used to determine the location of the sensor in 3D space.

[0021] System 10 may further include a processing device 50 including a processor 54 configured to receive patient body image data and the EM sensor signals. Processor 54 is configured to determine a location of one or more features of the delivery tool 20 from the EM sensor signals and register the location of the delivery tool feature(s) to the patientRef. No. A0012739US01 body image data. Processor 54 may provide the delivery tool feature location and the patient body image data to a display unit 52 for generating a graphical display of the location of the delivery tool feature relative to a graphical rendering of anatomy of the patient based on the patient body image data, as further described herein.

[0022] Processing device 50 may include or be connected to display unit 52. Processing device 50 may include memory 53, a processor 54, signal input / data ports 55, user interface 56, and communication unit 58. Processor 54 is coupled to the other components and units of processing device 50, e.g., via a data bus, for performing and controlling the functions attributed to processing device 50 herein. Processor 54 may execute instructions stored in memory 53. Processor 54 may include any one or more of a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or equivalent discrete or analog logic circuitry. In some examples, processor 54 may include multiple components, such as any combination of one or more microprocessors, one or more controllers, one or more DSPs, one or more ASICs, or one or more FPGAs, as well as other discrete or integrated logic circuitry. The functions attributed to processor 54 herein may be embodied as software, firmware, hardware or any combination thereof. Memory 53 may include any volatile, non-volatile, magnetic, optical, or electrical media, such as a random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically-erasable programmable ROM (EEPROM), flash memory, or any other digital or analog media.Memory 53 may include non-transitory computer-readable media that may store instructions that, when executed by processor 54, cause medical device system 10 to perform various methods and functions attributed to medical device system 10 as disclosed herein.

[0023] User interface unit 56 may include a mouse, touch screen, keypad or the like to enable a user to interact with processing device 50, e.g., to initiate and terminate an implant session, for uploading image data, adjust settings of display unit 52, enter display selections or make other user requests. Display unit 52, which may include a liquid crystal display, light emitting diodes (LEDs) and / or other visual display components, may generate a display of location information of delivery tool 20 and / or the EV lead being implanted by delivery tool 20 (e.g., relative to patient anatomical structures), intraoperative patient body images obtained by imaging unit 40 (e.g., fluoroscopy imagingRef. No. A0012739US01 unit, ultrasound imaging unit, x-ray imaging unit, or other intraoperative imaging unit) and a graphic rendering of 3D pre-operative patient image data 70 that may be received and stored in memory 53 for subsequent use during the implant procedure.

[0024] Display unit 52 may be configured to generate the display in a graphical user interface (GUI) including various windows, icons, user selectable menus, etc. to facilitate interaction by a user with the processing device 50. As described below, display unit 52 may display various windows to a user, e.g., in a GUI, for enabling a clinician or other user to view delivery tool location information registered to a rendering of the preoperative patient body image from different views or angles and at different time points during the implant procedure, which may be viewed in real time as the delivery tool 20 is being advanced in some examples.

[0025] Display unit 52 may function as an input and / or output device using technologies including liquid crystal displays (LCD), quantum dot display, dot matrix displays, light emitting diode (LED) displays, organic light-emitting diode (OLED) displays, cathode ray tube displays, e-ink, or monochrome, color, or any other type of display capable of generating tactile, audio, and / or visual output. In some examples, display unit 52 is a presence-sensitive display. Display unit 52 may serve as a user interface device that operates both as one or more input devices and one or more output devices.

[0026] Processing device 50 may include signal input / data ports 55 for receiving EM signals from EM sensors 26, pre-operative image data 70, and intra-operative image data from imaging unit 40. In some examples, an EM field emitter device 60, described further below, may be connected to signal input / data ports 55 for enabling processing device 50 to control generation of an EM field by EM field emitter device 60 to facilitate determination of the location and orientation of EM sensors 26 in the 3D space of the emitted EM field. In some examples, signal input / data ports 55 may include an external hard drive, flash drive, memory card or other data storage device for storing patient body image data, e.g., preoperative patient body image data 70, for transferring the image data to memory 53.

[0027] Additionally or alternatively, processing device 50 may receive the pre-operative image data 70, intra-operative image data from imaging unit 40, and / or EM sensor signals via a wireless or hardwired connection to communication unit 58. Communication unit 58 may include a transceiver and antenna configured for bidirectional communication with other devices or components of medical device system 10. Communication betweenRef. No. A0012739US01 devices or components of medical device system 10 may be established using a radio frequency (RF) link such as BLUETOOTH®, Wi-Fi, Medical Implant Communication Service (MICS) or other communication bandwidth. For example, imaging unit 40, EM field emitter 60 and processing device 50 may communicate using near field communication (NFC) or any of various types of other wireless communication protocols, which may include, but are not limited to, a BLUETOOTH® technology -based protocol (e.g., BLUETOOTH® low energy (BTLE) protocol), an ultra-wideband (UWB) technology -based protocol, or any other proprietary or non-proprietary communication protocols.

[0028] In various examples, communication between components and devices of medical device system 10 can be facilitated over a personal area network (PAN), a local area network (LAN) (e.g., a Wireless Fidelity (Wi-Fi) network) that can provide for communication over greater distances than the NFC protocol or provide other advantages (e.g., stronger encryption protocols). In some embodiments, the imaging unit 40, a storage device, server or database storing the pre-operative image data 70, processing device 50 and / or EM field emitting device 60 can communicate with one another and / or another device (e.g., a server device or a tertiary device) over a wide area network (WAN) using cellular or Hyper Text Transfer Protocol (HTTP)-based communication protocols (e.g., session initiation protocol (SIP)).

[0029] As such, processing device 50 may be in wired or wireless connection to a communications network via communication unit 58 for transferring data to / from a centralized database, server or computer to allow pre-operative image data 70 and intraoperative image data from imaging unit 40 to be downloaded to processing device memory 53 for access by processor 54. Communication unit 58 may be coupled to a communication network / cloud for receiving and transmitting data to a computing device, which may be a personal computer, personal mobile device or other computing device at a remote location from the patient to enable remote monitoring of the implant procedure.

[0030] System 10 may include the EM field emitting device 60 (also referred to herein as “EM field emitter” 60). When the EM sensors 26 of delivery tool 20 are placed within the EM field produced by EM field emitting device 60, EM sensor signals can be received by processing device 50 for determining the location of at least one feature of the delivery tool 20 in the EM field, e.g., in a 2D or 3D coordinate system defined relative to the EMRef. No. A0012739US01 field emitting device 60. System 10 may further include markers 62 and / or markers 64 located near or on the patient 12 in the EM field produced by EM field emitter 60. An imaging unit 40 may capture intra-operative patient body images during the implant procedure. The markers 62 and / or markers 64 may be positioned to appear in the patient body images to facilitate registration of the location of EM sensors 26 in the intraoperative patient body images.

[0031] Markers 62 may be incorporated as an array or grid-like pattern in EM field emitting device 60 in some examples. When the patient is in a prone position the grid-like arrangement of markers 62 can be observed in the anterior posterior (AP) view of the intra-operative patient body images. As such, markers 62 are referred to hereafter as AP view markers 62. It is to be understood, however, that markers 62 may not be limited to being viewed in an AP view of the intra-operative patient body images depending on the intraoperative position of the patient and the location of the EM field emitting device. Markers 64 may be positioned at anatomical landmarks along a lateral side of the patient in some examples or be arranged in an array or grid on a substrate that may be positioned alongside or attached to the patient. Markers 64 can be observed in a lateral view of the intra-operative patient body images in some instances. As such, markers 64 are referred to hereafter as lateral view markers 64. It is to be understood, however, that markers 64 may not be limited to being viewed in lateral view of the intra-operative patient body images depending on the intraoperative position of the patient and the location of the markers relative to the patient.

[0032] Processing device 50 may receive one or more intra-operative patient body images from imaging unit 40 and pre-operative patient body image data 70, which may be stored in the memory of an imaging device, in a patient database, on a memory card or other storage media. As such, pre-operative body image data 70 may represent a computer- readable storage medium storing the pre-operative body image data for accessibility by processing device 50. Processing device 50 may be configured to register the pre-operative patient body image data with the intra-operative patient body image data received from imaging unit 40. In this way, the feature location of the delivery tool 20 determined from EM sensor signals by processing device 50 can be registered to the intra-operative image data that is registered to the pre-operative patient body image. The pre-operative patient body image data 70 may be a 3D image of the patient’s anatomy, e.g., a computedRef. No. A0012739US01 tomography (CT) scan, magnetic resonance imaging scan, ultrasound or other 3D image. All or a portion of the pre-operative 3D image data 70, e.g., corresponding to one or more anatomical structures, a body organ, etc., can be rendered in a graphical display presented by display unit 52 in combination with the delivery tool feature location and optionally superimposed with an intra-operative patient body image from imaging unit 40 to provide user guidance during the EV lead implantation procedure as further described herein.

[0033] System 10 may further include the display unit 52 configured to generate a graphical display of the location of a feature of the delivery tool 20 relative to a graphical rendering of the preoperative patient body image or portion thereof to provide a clinician or other user visualization of the position of at least a portion of the delivery tool 20 (and / or an estimated position of the EV lead or portion thereof when delivered to an implant site by the delivery tool 20) relative to the patient’s anatomy. In this way, a clinician or other user of the medical device system 10 can be guided to advance the delivery tool 20 to an optimal site relative to the patient’s anatomy without line of sight view for positioning an EV lead for sensing electrophysiological signals and / or delivering electrical stimulation pulses.

[0034] Delivery tool 20 includes a tunneling rod 24 and a removable outer sheath 22 that can be placed over the tunneling rod 24. Delivery tool 20 includes one or more EM sensors 26, which may be positioned along an inner or outer diameter of the removable outer sheath 22 or embedded in a wall of the removable outer sheath 22 in various examples. Delivery tool 20 may be advanced along a non-transvenous tissue pathway to an EV lead implant site. The tunneling rod 24 may be inserted and fully advanced through an inner lumen (shown in FIG. 2) of the removable outer sheath 22 prior to advancement of the tunneling rod 24 through patient body tissue to the target implant site. The tunneling rod 24 may be subsequently withdrawn from the removable outer sheath 22 to enable advancement of the EV lead (not shown in FIG. 1) within the inner lumen of the removable outer sheath 22. Based on the graphical display produced by display unit 52 of at least one location of a feature of the delivery tool 20 relative to the graphical rendering of the patient’s anatomy from the pre-operative body image data, a clinician may confirm that the delivery tool is advanced to a target implant site for deploying the EV lead. The removable outer sheath 22 can be withdrawn leaving the EV lead positioned at the target implant site.Ref. No. A0012739US01

[0035] The EM sensor(s) 26 of delivery tool 20 may be disposed along the outer removable sheath 22, e.g., at the sheath distal end 28 and / or at one or more known distance(s) from the sheath distal end 28. In other examples, one or more EM sensors 26 may be located at, or known distances from, one or more other landmark features of the removable outer sheath 22 (e.g., the sheath proximal end, the mid-point, a preformed bend or curve of sheath 22) or of delivery tool 20. Processing device 50 may be configured to determine the EM sensor locations in the EM field produced by EM field emitter 60 based on signals received from the EM sensors 26. The EM sensor locations may be determined as coordinates in a coordinate system space of the EM field volume corresponding to a patient body region. Being at or a known distance from a feature of sheath 22 (or delivery tool 20), e.g., at or a known distance from sheath distal end 28, the location of the feature, e.g., sheath distal end 28, can be registered in a two-dimensional (2D) or three- dimensional (3D) image of the patient 12 based on the EM sensor signals. Registration of the EM sensor locations (or delivery tool and / or EV lead feature locations derived therefrom) in an intra-operative image of the patient 12 taken by imaging unit 40 can be facilitated by the location of AP view markers 62 and / or lateral view markers 64 in the intra-operative patient body image. The intra-operative patient body image data can be registered to pre-operative patient body image data 70 enabling processing device 50 to register the location of the feature of the removable outer sheath 22 (or delivery tool 20) and the pre-operative patient body image data 70.

[0036] In illustrative examples presented herein, an EV lead can be implanted substernally using delivery tool 20 for providing cardiac electrical signal sensing and delivering cardiac electrical stimulation. A graphical depiction of an expected position of the EV lead or portion thereof when advanced within the removable outer sheath 22 of delivery tool 20 and / or the expected position of the EV lead or portion thereof after the removable outer sheath 22 is retracted and withdrawn from the patient’s body 12 may be presented to a clinician by display unit 52. The expected position of the EV lead or portion thereof may be determined by the processing device 50 based on the registration of the position of EM sensor(s) 26 (or a delivery tool feature at a known distance from EM sensor(s) 26) in an intra-operative image, taken by imaging unit 40. The intra-operative image can be registered with the pre-operative image that may be a 3D image including the patient’s heart. In this way, the location of a feature of the delivery tool 20 determined from the EMRef. No. A0012739US01 sensor signals can be provided to display unit 52 as 3D coordinates, for example, for displaying the delivery tool feature location relative to a graphical rendering of the preoperative 3D patient body image or portion thereof. For example, a 3D graphical rendering of the patient’s heart may be generated from the pre-operative image data received by processing device 50, which may be superimposed with intra-operative images received from imaging unit 40 and a graphical representation of the delivery tool feature location and / or corresponding estimated EV lead location.

[0037] Two-dimensional fluoroscopic images taken intraoperatively allow a clinician to visualize the location of the delivery tool 20 being advanced relative to radiopaque anatomical structures, such as the patient’s sternum and ribs. Repeated fluoroscopic imaging throughout the implant procedure, however, exposes both the patient and the operating room staff to radiation. The techniques disclosed herein can be used in a manner that minimizes the number of fluoroscopic images taken during the EV lead implantation procedure with improved navigational guidance of the delivery tool 20 to a position for implanting the EV lead relative to the patient’s heart. Cardiac tissues and cardiac landmarks are not very well observed in a fluoroscopic image, particularly without the use of contrast dye. As such, the use of only fluoroscopic images acquired during the EV lead implantation procedure provides a clinician a limited visualization of the location of the delivery tool and expected EV lead implant position relative to the patient’s heart. Using the techniques disclosed herein, visual guidance of delivery tool location and estimated location of the EV lead relative to the patient’s heart is improved as further described below.

[0038] The EM field emitter 60 may include an array of the AP view markers 62. AP view markers 62 may be provided as tungsten beads or other radiopaque elements, that can be arranged at known distances from each other. When EM field emitter 60 including the array of AP view markers 62 is positioned relative to the patient, a grid of fiducial points corresponding to the AP view markers 62 can be viewed in an intra-operative patient body image taken by imaging unit 40, e.g., a fluoroscopic image taken by imaging unit 40. The grid of fiducial points corresponding to AP view markers 62 can be used in the registration of the location of the EM sensors 26 in the intra-operative patient body image. The AP view markers 62, e.g., provided as tungsten elements, may be viewed in the intra-operative patient body image without interference by the EM field emitter 60.Ref. No. A0012739US01

[0039] In the example shown, the EM field emitter 60 is shown positioned posteriorly, beneath the patient’s thorax, who may be in a prone position for the implant procedure. In this way, the AP view markers 62 can be viewed as a grid of fiducial points in the AP view of the patient 12 in an image taken by imaging unit 40. It is recognized however that depending on the position of patient 12 during the implant procedure, the delivery tool entry point, the delivery tool pathway and final EV lead implant position, the markers 62 may be positioned to appear as a grid of fiducial points in other intraoperative views of the patient images, not limited to an AP view as described here. Additionally or alternatively, medical device system 10 may include lateral view markers 64 that can be positioned on or along the patient 12 in a grid-like array and / or at one or more anatomical landmarks. Lateral view markers 64 may be provided as tungsten beads or other radiopaque elements. Lateral view markers 64 may be attached to the patient’s skin or disposed on a substrate that can be positioned relative to the patient’s anatomy. In the example shown, lateral view markers 64 may be positioned on or along a lateral side of patient 12 so that corresponding fiducial points can be viewed in a lateral view of an intra-operative patient body image taken by imaging unit 40. In this way, fiducial points corresponding to AP view markers 62 of EM field emitter 60 and fiducial points corresponding to lateral view markers 64 positioned on or along patient 12 may be observed in images taken by imaging unit 40 in one or more views of the patient body images (e.g., an AP view, anterior oblique views at one or more angles, lateral view, etc.). The fiducial point locations corresponding to AP view markers 62 and lateral view markers 64 in the coordinate system space corresponding to the EM field can facilitate registration of the EM sensor locations, delivery tool feature location and EV lead location or portion thereof in the intra-operative body image acquired during the EV lead implant procedure, which can be registered to the pre-operative body image data, e.g., relative to a 3D image of the patient’s heart.

[0040] In some examples, EM sensors 26 include tunnel magnetoresistance (TMR) sensors, which output a signal in response to a strength of a magnetic field at the sensor location. Interference from the imaging unit 40 or other sources can be avoided using a TMR sensor compared to other types of EM sensors. As the delivery tool 20 having EM sensors 26 is advanced internally in the patient, the EM sensors 26 output a signal correlated to the strength of the EM field emitted from EM emitter 60 at the respective EM sensor locations. The EM sensor signals can be converted to a coordinate location in theRef. No. A0012739US01 coordinate system space of the EM field and imaged patient body region. The strength of the signal output by the TMR sensor increases as a distance between the TMR sensor and the magnetic field source decreases, and conversely, decreases as a distance between the TMR sensor and the magnetic field source increases. The position of the EM sensors 26 relative to a reference 3D coordinate system, and thus a location of the sheath distal end 28 or other feature location of delivery tool 20, within an EM field generated by EM field emitter 60 can be derived. While a TMR sensor can be advantageously used as an EM sensor 26 to avoid interference with fluoroscopic images that may be captured by imaging unit 40, it is envisioned that removable outer sheath 22 may include any suitable location sensor configured to produce a signal correlated to the position of the sensor in an EM field or 3D coordinate space, such as for example, a hall sensor or hall effect sensor, an anisotropic magneto resistance sensor, a giant magnetoresistance sensor, or combinations thereof.

[0041] FIG. 2 is a diagram of the delivery tool 20 shown in FIG. 1 according to some examples. Delivery tool 20 may include a handle 34, elongated removable outer sheath 22 (also referred to herein as “removable outer sheath” or “sheath”), elongated tunneling rod 24 (also referred to herein as “tunneling rod”) and an external guide 36. Tunneling rod 24 extends from a rod proximal end 30 coupled to handle 34 to a rod distal end 32. Tunneling rod 24 may have a fixed geometry or may be adjustable or bendable to provide different angles or bends to accommodate the patient’s anatomy along a tunneling path. In some examples, tunneling rod 24 may include a preformed bend near distal end 32 but may be malleable to enable adjustments as needed for a given patient’s anatomy. Tunneling rod 24 may be stainless steel or other malleable or rigid material. Rod distal end 32 may be a rounded, e.g., non-piercing or atraumatic, distal end to slide between tissue layers with a reduced likelihood of piercing or puncturing through an organ or causing undue tissue damage.

[0042] Tunneling rod 24 may be between 15 and 30 centimeters (cm) in length and may be 20 to 25 cm in length as examples. Delivery tool 20 may be provided in different sizes having different lengths of tunneling rod 24 to accommodate patients of different sizes. Tunneling rod 24 may be 2 mm to 5 mm in diameter, as examples, and is about 3 mm or 9 French in diameter in an example. Tunneling rod 24 may be sized to enable advancement of tunneling rod 24 substemally, e.g., in the anterior mediastinum, approached from aRef. No. A0012739US01 location below the xyphoid process or ribcage, for placement of an EV lead in a substernal location as further described below. It is to be understood that tunneling rod 24 may be sized and shaped for advancement along an internal body pathway as needed for placement of an EV lead for a given medical application.

[0043] Delivery tool 20 may include external guide 36 for providing physical and visual guidance to the user relating to the location of tunneling rod 24 as it is being advanced. As such, external guide 36 can be an elongated member having a total length terminating at a guide distal end 39 that is aligned with tunneling rod distal end 32 (as indicated by the vertical dashed line L). In this way, the user can have a visual indication of the distance and direction that the tunneling rod distal end 32 is advanced. From an exterior view, the location of external guide distal end 39 can indicate to the user how far the tunneling rod distal end 32 has been advanced from an entry point, e.g., from an incision below the xyphoid process or ribcage, in a superior direction from the entry point and the rod’s general direction relative to the patient’s sternum or a medial sagittal plane, e.g., to the left, right or centered.

[0044] The external guide 36 may provide control over the depth of the tunneling rod 24 in that external guide 36 may remain external to the patient and glided along the skin of the patient, for example. As such a vertical distance 38 between external guide 36 and tunneling rod 24 may be fixed or adjustable to promote a desired depth beneath the skin of tunneling rod 24 as it is advanced, e.g., posterior to the sternum and / or ribcage in the illustrative example of positioning a substernal EV lead.

[0045] As such, external guide 36 may be aligned in parallel to tunneling rod 24, separated from tunneling rod 24 by a vertical distance 38, and having guide distal end 39 vertically aligned with tunneling rod distal end 32, as indicated by the dashed vertical line L. In some examples, external guide 36 is coupled to handle 34 by a proximal hinge 35. External guide 36 may be provided with a thumb lever 37 that enables a user to raise or lower external guide 36 to increase or decrease vertical distance 38 or lift external guide away from the exterior skin surface. In some examples exterior guide 36 is completely removable from handle 34 and / or adjustable in distance 38 from tunneling rod 24 as needed according to user preference and individual patient anatomy.

[0046] Tunneling rod 24 can be inserted (e.g., manually or using a robotic arm) into the body of the patient via an incision and advanced along a desired pathway, e.g., beneath theRef. No. A0012739US01 patient’s sternum and within the anterior mediastinum to create a route in the substernal space through which an EV lead can be implanted in. Using the techniques disclosed herein for guiding the clinician during delivery tool advancement can reduce the likelihood of damaging the nerves in the auxiliary region, piercing the lungs, piercing the heart, perforating muscles, routing the delivery tool 20 between muscle layers, etc. While placement of the EV lead in a substernal location is described herein as an illustrative example of the use of medical device system 10, it is to be understood that the presently disclosed techniques and medical device system 10 can be adapted for use in other medical device applications which utilize a non-transvenous, EV lead.

[0047] Removable outer sheath 22 includes an outer sidewall 29 that may be generally circumferential to accommodate tunneling rod 24 and advancement of the EV lead through an open lumen 23 defined by outer sidewall 29. Outer sidewall 29 extends from a sheath proximal end 27 to a sheath distal end 28 and defines the open lumen 23 that is sized to receive tunneling rod 24. Removable outer sheath 22 may include a side port 31 that can be used to flush fluid through the open lumen 23. Removable outer sheath 22 may include proximal tabs 21 to facilitate retraction / advancement of removable outer sheath 22 over tunneling rod 24 and for stabilizing the position of removable outer sheath 22 during removal of tunneling rod 24 and insertion of an EV lead in its place within open lumen 23.

[0048] After tunneling rod 24, fully advanced through open lumen 23 of removable outer sheath 22, is advanced to a desired substernal (or other non-transvenous) location, tunneling rod 24 may be withdrawn from removable outer sheath 22 such that sheath 22 is left in the desired substernal (or other non-transvenous) location. The EV lead can be advanced through open lumen 23 to the implant site, and removable outer sheath 22 can be withdrawn leaving the EV lead in place at the implant site. Removable outer sheath 22 may be a splitable sheath to facilitate withdrawal of sheath 22 over the EV lead and removal from the patient.

[0049] In some cases, suboptimal placement of the EV lead in a subcutaneous or substernal space can lead to medical device performance issues. In the case of a cardiac pacemaker or ICD being coupled to the EV lead after implantation, suboptimal EV lead placement may lead to cardiac signal sensing issues due to poor signal quality (e.g., low or variable signal strength). Suboptimal EV lead placement may lead to therapy delivery issues, e.g., due to relatively high cardiac defibrillation threshold and / or relatively highRef. No. A0012739US01 cardiac pacing capture thresholds. Repositioning of the EV lead due to suboptimal positioning may increase the operation time required to implant the EV lead.

[0050] Suboptimal positioning of an EV lead may occur when the distance from the lead to the patient’s heart is relatively large or when the lead is advanced too far superiorly or not far enough. External guide 36 can provide a general indication of the location of tunneling rod distal end 32 from an external view. The distance and location of the delivery tool 20 from the patient’s heart, anatomical landmarks of the heart, and / or other internal anatomical landmarks, however, cannot be seen by the implanting clinician. A fluoroscopic image can be taken during an EV lead implant procedure but a two- dimensional cross-sectional view may not provide accurate positional information relative to the patient’s heart or other anatomical structures.

[0051] To promote optimal lead placement, removable outer sheath 22 includes one or more EM sensors 26a and 26b (collectively 26) to enable EM navigation and registration of the location of at least one landmark feature of delivery tool 20 relative to a 2D or 3D view of the cardiothoracic space. For example, when EM sensors 26 are positioned at the distal end 28 of sheath 22 (as shown), or at a known distance from sheath distal end 28, the location of sheath distal end 28 can be registered in an intra-operative 2D fluoroscopy image that is registered to pre-operative 3D body image data. In this way, a relatively precise visual representation of the location of the EV lead or portions thereof (e.g., the EV lead distal end and / or one or more electrodes carried by the EV lead) with respect to a graphical rendering of the 3D patient body image can be displayed to the implanting clinician. The estimated implant location of the EV lead can be visually represented by medical device system 10, e.g., distances from the heart, based on the localization of the EM sensors 26, even before tunneling rod 24 is removed and the EV lead is fully advanced through sheath 22. A desired implant region for optimal sensing and therapy delivery when the EV lead is delivered via the delivery tool and subsequently coupled to an ICD (or other medical device for sensing cardiac electrical signals and / or delivering cardiac electrical stimulation therapies) can be verified by the clinician prior to removing tunneling rod 24, prior to advancing the EV lead within removable outer sheath 22, and / or prior to removing the outer sheath 22.

[0052] In some examples, orientation information of the EM sensors 26 may be determined in addition to the location information (e.g., x-, y- and z- coordinates in aRef. No. A0012739US01 coordinate space of the EM field). For instance, the roll, yaw and / or pitch of the EM sensors 26 may be determined relative to the axes of the coordinate space of the EM field from the EM sensor signals. For instance, when a single EM sensor 26a or 26b is provided, the yaw and / or pitch angles may be determined by processor 54 or processing device 50. When both EM sensors 26a and 26b are provided, a third orientation angle, e.g., the roll angle, may be determined using the two EM sensor signals. An orientation angle may be determined from the magnitudes of the EM sensor signals using trigonometric relationships, e.g., using the x-, y- and z- vectors representing the EM sensor (x, y, z) location in the 3D coordinate space. In some examples, as further described below, the EV lead may have a lead body having a preformed shape including one or more bends or curves and / or carry electrodes having a directional orientation.

[0053] As such, a specified orientation of the EV lead may be desired upon release from the removable outer sheath 22. As such, the orientation of the removable outer sheath 22 may be determined by processor 54 of processing device 50 based on the EM sensor signals so that the EV lead can be advanced into the removable outer sheath 22 having a known orientation relative to the patient’s body. One or more guides or markers, e.g., the direction of tabs 21, at the sheath proximal end 27 may indicate to the clinician the correct orientation of the EV lead for advancement into the removable outer sheath 22. In this way, confirmation of the orientation of the removable outer sheath 22 allows the EV lead body, advanced within sheath 22 according to a known orientation, to relax into a preformed shape oriented as desired relative to anatomical structures. When the lead body carries directional electrodes, the correct orientation of the EV lead can be confirmed based on the orientation of the sheath distal end and relative orientation / alignment of the EV lead advanced within sheath 22 so that the directional electrodes are positioned in a desired direction relative to anatomical structures, e.g., relative to the chambers of the patient’s heart.

[0054] The electrical signals from EM sensors 26 may be received by processing device 50 (FIG. 1) for determining a location (and orientation) of a feature of the delivery tool 20. As described herein, the location of the feature of the delivery tool 20 can be registered to an intra-operative image obtained by imaging unit 40 (shown in FIG. 1). As such, removable outer sheath 22 may include insulated, elongated electrical conductors 25 extending through or along the outer sidewall 29. In some examples, elongated electricalRef. No. A0012739US01 conductors 25 are embedded in the outer sidewall 29. In other examples, elongated electrical conductors 25 may be sealed to the inner or outer surface of outer sidewall 29. Each EM sensor 26a and 26b may be electrically coupled to a respective one of conductors 25 extending from the EM sensor 26a or 26b to sheath proximal end 27. The conductors 25 may be electrically coupled to a connector assembly 33 that enables electrical connection to external processing device 50 to transmit signals from sensors 26a and 26b to the external processing device 50 via conductors 25 and connector assembly 33. Connector assembly 33 may be provided for hardwired connection to processing device 50. In other examples, connector assembly 33 may include a communication circuit for wirelessly transmitting the EM sensor signals, e.g., via local communication network or BLUETOOTH.

[0055] In the example shown, EM sensors 26 are positioned at the sheath distal end 28. In other examples, however, an EM sensor may additionally or alternatively be positioned at other locations along sheath 22. For example, an EM sensor may be positioned at a distance proximal from sheath distal end 28 that corresponds to a location of an electrode carried by the EV lead when the EV lead is fully advanced within sheath 22. The location of the EM sensor determined from the EM sensor signal then corresponds to the location of the EV lead electrode when it is advanced within the sheath 22. However, when EM sensors 26 are positioned at the sheath distal end 28, the relative distances from sheath distal end of EV lead electrodes when the EV lead is advanced within the sheath are known distances. These known distances from sheath distal end 28 can be used in combination with the determined location of sheath distal end 28 for determining estimated EV lead electrode locations as further described below.

[0056] FIGs. 3A-3C are conceptual diagrams of patient 12 implanted with an EV ICD system 100. FIGs. 3A — 3C are diagrams of one example of an implantable medical device system, in this case an ICD system 100, that may include an EV lead 116. EV lead 116 is an example of an EV lead that can be advanced non-transvenously to an implant site using delivery tool 20 of FIG. 2 with the guidance of the medical device system 10 of FIG. 1 according to the techniques disclosed herein. FIG. 3 A is a front view of patient 12 implanted with ICD system 100. FIG. 3B is a side or lateral view of patient 12 implanted with ICD system 100. FIG. 3C is a transverse view of patient 12 implanted with ICD system 100.Ref. No. A0012739US01

[0057] In the example shown, EV lead 116 extends subcutaneously or submuscularly over the ribcage 132 medially from ICD 114 toward a center of the torso of patient 12, e.g., toward xiphoid process 120 of patient 12. At a location near xiphoid process 120, EV lead 116 bends or turns and extends superiorly within anterior mediastinum 136 (see FIG. 3C) in a substernal position. Anterior mediastinum 136 may be viewed as being bounded laterally by pleurae 139, posteriorly by pericardium 138, and anteriorly by sternum 122 (see FIG. 3C). The distal portion 125 of EV lead 116 may extend posteriorly to sternum 122 substantially within the loose connective tissue and / or substernal musculature of anterior mediastinum 136. EV lead 116 implanted such that the distal portion 125 is substantially within anterior mediastinum 136, may be referred to as a “substernal lead.”

[0058] Although illustrated in FIG. 3 A as being substantially centered beneath sternum 122, in other examples the final implant position of the distal portion 125 of EV lead 116 may be offset laterally from the center of sternum 122 and may extend substantially parallel to sternum 122 or angled laterally from sternum 122 toward the left or the right. In some instances, EV lead 116 may extend angled laterally such that distal portion 125 of EV lead 116 is underneath / below the ribcage 132 in addition to or instead of sternum 122. In other examples, the distal portion 125 of EV lead 116 may be implanted in other extravascular, intra-thoracic locations. Alternatively, EV lead 116 may be placed along other subcutaneous or submuscular paths. The path of EV lead 116 may depend on the location of ICD 114, the arrangement and position of electrodes carried by EV lead 116, individual patient anatomy and / or other factors.

[0059] The illustrative examples presented herein refer to an EV lead that is coupled to an ICD 114. It is contemplated, however, that delivery tool 20 and aspects of the techniques disclosed herein may be adapted for use in implantation of other EV leads for a variety of medical applications, which may be implanted in various internal body locations including subcutaneous, submuscular, substernal, intrathoracic or intraabdominal locations depending on the particular medical application and the medical device that the EV lead is being connected to. The medical device that the EV lead is being connected to is not necessarily limited to being an ICD and may be another type of medical device, such as a pacemaker, cardiac monitor, electrophysiological monitor, neurostimulator, or the like.

[0060] In this example, ICD system 100 includes ICD 114 and EV lead 116 for sensing cardiac electrical signals, detecting arrhythmia and delivering electrical stimulationRef. No. A0012739US01 therapy. ICD system 100 may be configured to provide high voltage CV / DF shocks and / or cardiac pacing pulses in response to detecting a cardiac arrhythmia based on processing and analysis of cardiac electrical signals sensed via EV lead 116. Electrodes carried by EV lead 116 may be used for sensing the cardiac electrical signals and delivering cardiac electrical stimulation pulses from a substernal implant site, for example.

[0061] ICD 114 includes a housing 115 that forms a hermetic seal that protects internal components of ICD 114. The housing 115 of ICD 114 may be formed of a conductive material, such as titanium or titanium alloy. The housing 115 may function as an electrode (sometimes referred to as a “can” electrode). Housing 115 may be used as an active can electrode for use in delivering CV / DF shocks or other high voltage pulses delivered using a high voltage therapy circuit. In other examples, housing 115 may be available for use in delivering unipolar, relatively lower voltage cardiac pacing pulses and / or for sensing cardiac electrical signals in combination with electrodes carried by EV lead 116.

[0062] The optimal or target implant position of lead 116 and implant pathway guided by delivery tool 20 may depend on the implant location of ICD 114. In order to achieve reliable cardiac signal sensing and / or cardiac electrical stimulation, an electrode vector between two electrodes carried by lead 116 and / or an electrode vector between one or more electrodes carried by lead 116 and housing 115 extends through or in operative proximity to heart 8. ICD 114 may be implanted between the left posterior axillary line and the left anterior axillary line of patient 12. In the example shown, ICD 114 is shown implanted subcutaneously on the left side of patient 12 along the ribcage 132. In this case, the EV lead 116 may extend toward xyphoid process 120 then superiorly to the substernal position illustrated in FIGs. 3A — 3C. In this way, a substantial mass of the ventricles of the heart 8 is encompassed by an electrode vector between electrodes carried by distal portion 125 of EV lead 116 and ICD housing 115. ICD 114 may, however, be implanted at other subcutaneous or submuscular locations in patient 12. For example, ICD 114 may be implanted in a subcutaneous pocket in the pectoral region. In this case, lead 116 may extend subcutaneously or submuscularly from ICD 114 toward the manubrium of sternum 122 and bend or turn and extend inferiorly from the manubrium to the desired location subcutaneously, submuscularly or substemally, for instance. In yet another example, ICD 114 may be placed abdominally. As such, EV lead 116 may be implanted in other locations than the example shown. The ICD and EV lead implant configuration shown in FIGs.Ref. No. A0012739US013A — 3C is illustrative in nature and should not be considered limiting in the practice of the techniques disclosed herein.

[0063] ICD 114 includes a connector assembly 117 (also referred to as a connector block or header) that includes electrical feedthroughs crossing housing 115 to provide electrical connections between conductors (not shown) extending within the lead body 118 of lead 116 and electronic components included within the housing 115 of ICD 114. ICD housing 115 may house one or more processing circuits, memories, transceivers, cardiac electrical signal sensing circuitry, therapy delivery circuitry that may include pacing pulse generation circuitry and / or CV / DF shock pulse generation circuitry, power source(s) and other components for sensing cardiac electrical signals, detecting a heart rhythm, and controlling and delivering electrical stimulation pulses to treat an abnormal heart rhythm.

[0064] Elongated lead body 118 has a proximal end 127 that includes a lead connector (not shown) configured to be connected to ICD connector assembly 117 after confirming the implant position of EV lead 116 according to the techniques disclosed herein. The distal portion 125 of elongated lead body 118 includes one or more electrodes. In the example illustrated in FIGs. 3 A and 3B, the distal portion 125 includes defibrillation electrodes 124 and 126 and pace / sense electrodes 128 and 130. In some cases, defibrillation electrodes 124 and 126 may together form a defibrillation electrode in that they may be configured to be activated concurrently. Alternatively, defibrillation electrodes 124 and 126 may form separate defibrillation electrodes in which case each of the electrodes 124 and 126 may be activated independently.

[0065] Electrodes 124 and 126 (and in some examples housing 115) are referred to herein as “defibrillation electrodes” because they can be utilized, individually or collectively, for delivering high voltage stimulation therapy (e.g., CV / DF shocks). Electrodes 124 and 126 may be elongated coil electrodes and generally have a relatively high surface area for delivering high voltage electrical stimulation pulses compared to pacing and sensing electrodes 128 and 130. However, electrodes 124 and 126 and housing 115 may also be utilized to provide pacing functionality, sensing functionality or both pacing and sensing functionality in addition to or instead of high voltage stimulation therapy. In this sense, the use of the term “defibrillation electrode” herein should not be considered as limiting the electrodes 124 and 126 for use in only high voltage CV / DF shock therapy applications. For example, either of electrodes 124 and 126 may be used as a sensing electrode in aRef. No. A0012739US01 sensing electrode vector for sensing cardiac electrical signals and determining a need for an electrical stimulation therapy.

[0066] Electrodes 128 and 130 are relatively smaller surface area electrodes which are available for use in sensing electrode vectors for sensing cardiac electrical signals and may be used for delivering relatively low voltage pacing pulses in some configurations. Electrodes 128 and 130 are referred to as pace / sense electrodes because they are generally configured for use in low voltage applications, e.g., used as either a cathode or anode for delivery of pacing pulses and / or sensing of cardiac electrical signals, as opposed to delivering high voltage CV / DF shocks. In some instances, electrodes 128 and 130 may provide only pacing functionality, only sensing functionality or both.

[0067] ICD 114 may obtain cardiac electrical signals corresponding to electrical activity of heart 8 via one or more sensing electrode vectors that include combinations of electrodes 124, 126, 128 and / or 130. ICD 114 may be configured to perform morphology analysis of the cardiac electrical signal and / or sense cardiac electrical event signals, e.g., R-waves and / or P-waves attendant to myocardial depolarizations, for detecting cardiac arrhythmias. Sensed cardiac signals may be used for determining the heart rate and rhythm and determining a need for cardiac pacing (e.g., for treating bradycardia, atrioventricular conduction block, or asystole) or for determining a need for tachyarrhythmia therapies (e.g., anti-tachycardia pacing (ATP) or CV / DF shocks).

[0068] In the example illustrated in FIGs. 3 A and 3B, electrode 128 is located proximal to defibrillation electrode 124, and electrode 130 is located between defibrillation electrodes 124 and 26. In some examples, a third pace / sense electrode (not shown) may be located distal to defibrillation electrode 126, proximate to or on the distal end 129 of lead body 118. Electrodes 128 and 130 are illustrated as ring electrodes; however, electrodes 128 and 130 may comprise any of a number of different types of electrodes, including ring electrodes, short coil electrodes, hemispherical electrodes, directional electrodes, segmented electrodes, or the like. Electrodes 128 and 130 may be positioned at other locations along lead body 118 and are not necessarily limited to the positions shown. In other examples, EV lead 116 may include fewer or more pace / sense electrodes and / or defibrillation electrodes than the example shown here.

[0069] The electrical conductors (not illustrated) extending through one or more lumens of the elongated lead body 118 of lead 116 are electrically coupled to the lead connector atRef. No. A0012739US01 the proximal lead end 127 to and to respective electrodes 124, 126, 128 and 130 located along the distal portion 125 of the lead body 118. The elongated electrical conductors contained within the lead body 118 may be separate insulated conductors to electrically couple the electrodes 124, 126, 128 and 130 to circuitry, such as a therapy delivery circuit and / or a sensing circuit, of ICD 114 via connections in the connector assembly 117, including associated electrical feedthroughs crossing housing 115. The electrical conductors transmit electrical stimulation pulses from a therapy delivery circuit within ICD 114 to one or more of defibrillation electrodes 124 and 126 and / or pace / sense electrodes 128 and 130 and transmit electrical signals produced by the patient’s heart 8 from one or more of defibrillation electrodes 124 and 126 and / or pace / sense electrodes 128 and 130 to the sensing circuit within ICD 14.

[0070] Using the techniques described herein, the distal portion 125 of EV lead 116 can be inserted into the patient’s body via an incision 121 and advanced to a substernal implant position using delivery tool 20. The guidance provided by medical device system 10 of FIG. 1 enables a clinician to advance the delivery tool 20 and distal portion 125 of EV lead 116 to an optimal implant site without being advanced too close to the lungs, heart or other tissues that could cause undue injury or risk of lead migration or dislodgment over time while promoting an optimal distance and location of electrodes 124, 126, 128, and 130 with respect to heart 8 for sensing cardiac signals and delivering cardiac electrical stimulation therapies. The lead proximal end 127 may be advanced subcutaneously or submuscularly from the incision 121 to the ICD 114 for connection to connector assembly 117.

[0071] In some examples, the distal end 129 of lead 116 may be advanced to within a target region 140 relative to heart 8 with the guidance of the medical device system 10 of FIG. 1 by advancing the sheath distal end 28 (FIG. 2) of delivery tool 20 to the target region 140. The target region 140 may be a 3D region (as seen in FIGs. 3 A and 3B) that, when EV lead distal end 120 falls within, promotes positioning of electrodes 124, 126, 128 and 130 in reliable operative locations relative to heart 8. The target region 140 may be defined by maximum and minimum distances from heart 8 (see FIG. 3B), which may be relative to a specified anatomical landmark of heart 8 or an epicardial surface of heart 8 during a minimum volume of heart 8 and / or during a maximum volume of heart 8 as examples. The target region 140 may additionally or alternatively be defined relative toRef. No. A0012739US01 non-cardiac anatomical landmarks, such as the manubrium of sternum 125, the posterior surface of sternum 125, xyphoid process 120, an nth rib or an nth intercostal space, as examples.

[0072] The target region 140 may be depicted in a graphical rendering of a patient body image displayed by display unit 52. For example, the target region 140 may be superimposed on a 3D rendering of the patient’s heart 8 derived from the pre-operative 3D body image, which may be superimposed on one or more 2D body images, e.g., an AP and left lateral fluoroscopic images, taken during the implant procedure by imaging unit 40 (FIG. 1). The boundaries of the target region 140 may be specified based on empirical data from a population of patients receiving an EV lead and ICD system. For example, the boundaries of target region 140 relative to one or more anatomical landmarks may be based on a distribution of locations of the EV lead distal end relative to the anatomical landmark(s) versus defibrillation thresholds, successful CV / DF shock delivery, unnecessary CV / DF shock delivery due to false tachyarrhythmia detection, or other clinical outcomes.

[0073] The lead body 118 of EV lead 116 may be formed from a non-conductive material, including silicone, polyurethane, fluoropolymers, mixtures thereof, and / or other appropriate materials, and shaped to form one or more lumens within which the one or more conductors extend. To accommodate advancement through the delivery tool removable outer sheath 22 for implantation, lead body 118 may be generally tubular or cylindrical in shape. In other examples, the distal portion 125 (or all of) the elongated lead body 118 may have a flat, ribbon or paddle shape. Lead body 118 can be provided with the longitudinal stiffness and outer diameter sized to be advanceable and retractable through the inner open lumen 23 of removable outer sheath 22. In other examples, lead body 118 may include a hollow lumen for receiving a guidewire that can provide longitudinal stiffness to lead body 118 for facilitating advancement of the distal portion 125 through the removable outer sheath 22. Lead body 118 may be formed having a preformed distal portion 125 that is generally straight, curving, bending, serpentine, undulating or zigzagging. When advanced within the inner open lumen 23 of removable outer sheath 22 (after tunneling rod 24 is withdrawn), any preformed bends or curves of lead body 118 may straighten to conform to the inner open lumen 23. The lead body 118 may be held in a straightened position when held within the confines of the inner open lumen 23 (shown inRef. No. A0012739US01FIG. 2). When removable outer sheath 22 is retracted and withdrawn to leave EV lead 116 at the implant position, lead body 118 may relax into its preformed shape that may include one or more preformed bends or curves.

[0074] In the example shown, lead body 118 includes a pre-formed curving distal portion 125 having two “C” shaped curves, which together may resemble the Greek letter epsilon, “s ” Defibrillation electrodes 124 and 126 are each carried by one of the two respective C- shaped portions of the lead body distal portion 125. The two C-shaped curves are seen to extend or curve in the same direction away from a central axis of lead body 118, along which pace / sense electrodes 128 and 130 are positioned. Pace / sense electrodes 128 and 130 may, in some instances, be approximately aligned with the central axis of the straight, proximal portion of lead body 118 such that mid-points of defibrillation electrodes 124 and 126 are laterally offset from pace / sense electrodes 128 and 130.

[0075] Other examples of extra-cardiovascular leads including one or more defibrillation electrodes and one or more pacing and sensing electrodes carried by curving, serpentine, undulating or zig-zagging distal portion of the lead body 118 that may be implemented with the techniques described herein are generally disclosed in U.S. Patent No. 10,675,478 (Marshall, et al.), incorporated herein by reference in its entirety. In other examples, lead body 118 is a flexible elongated lead body without any pre-formed shape, bends or curves. In this case, the distal portion 125 of EV lead 116 may remain in the position that is conformed to the position of the outer removable sheath 22 when the EV lead 116 is advanced through sheath 22, which may be a substantially straight position. The techniques disclosed herein are not limited to any particular lead body design as long as at least a distal portion 125 is sized with an outer diameter that can fit for advancement within the inner open lumen 23 of removable outer sheath 22.

[0076] In some cases, the position of the target implant region 140 may take into account any retraction of distal end 129 that may occur as lead body 118 transitions from the straightened position within removable outer sheath 22 to assume the C-shape bends shown in FIG. 3 A (or any other pre-formed bends or curves). One example of an EV lead (or “non-transvenous” lead) that may be implanted using the system and techniques disclosed herein is the EPSILAEV™ MRI SURESCAN™ Model EV2401 extravascular lead available from Medtronic, Inc. (Dublin, Ireland).Ref. No. A0012739US01

[0077] In order to promote an optimal therapy delivery electrode vector between defibrillation electrodes 124, 126 and housing 115, the C-shaped curves of lead body 118 carrying defibrillation electrodes 124 and 126 may extend generally toward the patient’s right as shown. As such EV lead 116 may be advanced within removable outer sheath 22 of delivery tool 20 having an orientation that promotes the relaxation of the preformed C- shaped curves pushing defibrillation electrodes 124 and 126 in the rightward direction. To facilitate a desired orientation of distal portion 125 within sheath 22, one or more markers on lead body 118 and / or the proximal lead connector at the lead proximal end 127 may be aligned with corresponding guides or markers of the proximal sheath end 29 or tabs 21 (see FIG. 2). In this way, when removable outer sheath is withdrawn and distal portion 125 relaxes into its normal shape, the C-shaped curves carrying defibrillation electrodes 124 and 126 will extend in the desired direction relative to heart 8 and ICD 114.

[0078] In other examples, the EV lead 116 may include directional electrodes that do not necessarily wholly circumscribe the lead body 118. Electrodes 124, 126, 128 and 130 may fully circumscribe the lead body distal portion 125. In other instances, however, one or more electrodes carried by an EV lead may have an exposed, electrically conductive surface along only one side or only a portion of the circumference of the lead body to direct the electrical energy delivered by the electrode in a desired direction or to sense electrical signals arising primarily from a desired direction. In this case, a desired orientation of the directional electrode may be promoted by providing orientation guides or markers for aligning the EV lead with the removable outer sheath 22 as the EV lead is advanced within the open lumen 23. Furthermore, processing device 50 may be configured to determine the orientation of the sheath 22 based on the EM sensor signals for promoting a desired orientation of the EV lead upon release from sheath 22.

[0079] In the various example implant locations of EV lead 116 shown or described herein, cardiac signals sensed by ICD 114 may have a relatively low and / or variable signal strength, e.g., caused by postural changes, respiration, cardiac motion or other body movement. Cardiac signals sensed by EV lead 116 may be contaminated by skeletal muscle myopotentials and / or environmental noise, e.g., electromagnetic interference. Undersensing of R- waves or fibrillation waves may result in an undetected tachyarrhythmia when ATP or CV / DF therapy may be needed. Oversensing of cardiac P- waves or T-waves due to R-wave variability or oversensing of skeletal muscleRef. No. A0012739US01 myopotentials or other electrical noise signals as false R-waves may lead to a false tachyarrhythmia detection resulting in unnecessary ATP or CV / DF shock delivery. In other instances, oversensing of cardiac signals (e.g., falsely sensing P-waves or T-waves as being R-waves) or non-cardiac noise (skeletal muscle myopotentials, EMI or other electrical noise) may result in withholding of pacing pulses when cardiac pacing is actually needed to prevent a long ventricular pause or asystole. Undersensing of R-waves or fibrillation waves may cause unneeded ventricular pacing pulse delivery that could confound VT / VF detection. As such, the implant location of EV lead 116 can impact the long term performance of ICD 114 in properly sensing and detecting cardiac rhythms and in delivering cardiac electrical stimulation therapies for treating detected arrhythmias.

[0080] Furthermore, the pacing capture threshold and / or CV / DF threshold required to depolarize myocardial cells can be relatively high if the positions of therapy delivery electrodes are too far away from the heart 8 or the therapy delivery electrode vector does not encompass sufficient heart mass. EV lead position that results in relatively low pacing capture thresholds and defibrillation thresholds can promote longevity of the ICD battery and promote reliable and successful therapy delivery.

[0081] Techniques disclosed herein provide improvements in implantation guidance and navigation techniques for implanting an EV lead to reduce the likelihood of low or variable cardiac signal strength (or other electrophysiological signal strength) and / or reduce the likelihood of high pacing and / or CV / DF capture thresholds (or the need for relatively high electrical stimulation energy in other therapy delivery applications such as neurostimulation therapies). The techniques disclosed herein provide specific improvements in a medical device system for guiding EV lead implantation that reduces human error and may reduce surgery time and risk of complications during and / or after surgery as it relates to EV lead placement and can improve the performance of an implantable medical device and EV lead system, such as the ICD system 100 of FIGs. 3A- 3C.

[0082] FIG. 4 is a flow chart 200 of a method for implanting an EV lead using medical device system 10 of FIG. 1 according to some examples. At block 202, with continued reference to FIGs. 1 and 2, processing device 50 may receive 3D image data of the patient 8. The 3D image data may be obtained as one or more preoperative images of the region of the patient’s body in which the EV lead is to be implanted and may include one or moreRef. No. A0012739US01 preoperative images of region(s) of the patient’s body through which the EV lead is to be advanced and / or the final intended implant location. For the sake of illustration, the flow charts and other diagrams presented herein relate to the implant procedure of EV lead 116 of FIGs. 3A-3C, being implanted substemally for sensing cardiac signals and delivering cardiac electrical stimulation therapies. As such, the 3D image data received by processing device 50 at block 202 includes the patient’s heart and may include the substernal area where the EV lead 116 is to be implanted. For instance, data from a preoperative chest computed tomography (CT) scan or other chest 3D imaging data that includes a 3D image of the patient’s heart and cardiothoracic region may be received by processing device 50. Processing device 50 may be configured to extract heart segmentation data from the chest CT scan, for example. The heart segmentation data can be used by processing device 50 for generating a graphical rendering of the heart image that can be displayed by display unit 52 during the implant procedure as further described below.

[0083] The 3D image data received at block 202 is generally referred to herein as “preoperative” image data because the 3D imaging equipment, such as CT imaging equipment, is generally not available in the surgical theater where the EV lead implantation procedure is performed. As such, the 3D image data is generally, but not necessarily, obtained preoperatively as part of the surgical planning and preparation. When 3D imaging equipment is available at the time of the implant procedure, the 3D image data may be obtained and received by the processing device 50 as part of the implant procedure.

[0084] During the implant procedure, 2D fluoroscopic images, e.g., in AP and lateral views, may be obtained from imaging unit 40 and provided as input received by processing device 50 at block 204. In some examples, the 2D images may be obtained in at least two orthogonal views, e.g., an AP view and a left lateral view, though one view or more than two views may be obtained for registration with the preoperative 3D image data. In this example, the intraoperative image data corresponds to 2D fluoroscopic images, however in other examples other 2D or 3D images may be obtained, e.g., using ultrasound, x-ray or other imaging methods that can provide an image that includes the 3D coordinate space of the EM field produced by EM field emitter 60.

[0085] At block 206, processor 54 of processing device 50 registers the 3D image data to the intra-operative image data. For instance, heart image segments derived from theRef. No. A0012739US01 received pre-operative image data (which may be stored in processing device memory 53) may be registered to the 2D image data, e.g., in the AP and left lateral views, received from imaging unit 40. One or more anatomical landmarks may be used in registering the 3D image data relative to the 2D image data. In some examples, the 3D image data may be converted to a 3D mesh representing the 3D image data in polygonal shapes and vertices that define the 3D shape of the patient’s anatomy, e.g., the 3D volumetric shape of the patient’s heart. A segmentation of the 3D mesh or a projection of the 3D mesh onto a 2D plane can be used in registering the 3D image data to the 2D intraoperative image. Various error or distance calculations may be performed, e.g., using a cost function, to determine the optimal registration between the 3D mesh and the 2D intraoperative image. In some examples, artificial intelligence methods may be used for registering the 3D image data to the 2D intraoperative images. The registration process may include determining rotation, translation, scaling and projection parameters for transforming the 3D image data into the 2D image coordinate system, which may be defined by two 2D planar views, e.g., an AP and lateral view. Example techniques for registering 3D and 2D image data that may be adapted for use in the methods disclosed herein are generally described in U.S. Patent No. 8,942,455 (Chou, et al.) and in U.S. Patent No. 8,036,441 (Frank, et al.), both of which incorporated herein by reference in their entirety. Various algorithms for registering the 3D image data and the 2D image data may be used for generating a graphical rendering of the patient’s heart relative to the biplanar 2D image data for display by display unit 52.

[0086] At block 208, processing device 50 receives EM sensor signals from delivery tool 20 as it is advanced into the substernal space, e.g., posterior to the patient’s sternum in the mediastinum as generally described above. The outer removable sheath 22 can be assembled over the tunneling rod 24 prior to insertion of tunneling tool 24 into the patient’s body so that the rod distal end 32 (see FIG. 2) can be advanced through the tissue pathway. As the tunneling tool 24 is advanced along the tissue pathway, the EM sensors 26 of removable sheath 22, assembled over tunneling tool 24, can provide sensor signals for tracking the location (and in some examples the orientation) of the sheath distal end 28. The approximate location of rod distal end 32 is known from knowing the location of sheath distal end 28 because rod distal end 32 can extend a known distance out from sheath distal end 28 when tunneling rod 24 is fully inserted through the open inner lumen 23 of sheath 22.Ref. No. A0012739US01

[0087] The EM sensor signals are responsive to changes in the position of the EM sensors 26 as their location changes in the 3D space of the EM field produced by EM field emitter 60. Fiducial points corresponding to AP view markers 62 and / or lateral view markers 64 may facilitate registration of the location of EM sensors 26 in the AP and lateral views of the patient 12. By registering the location of EM sensors 26 to the intra-operative imaging data that is registered with the 3D pre-operative image data, the location information of EM sensors relative to the patient’s 3D heart image data can be determined by processor 54 and passed to display unit 52 at block 210. For instance, processor 54 may be configured to compute x, y and z coordinates of the location of EM sensors 26 in a 3D coordinate space defined by the EM field. The location of the EM sensors 26, the location of the sheath distal end 28 (known based on the location of the EM sensors 26), and / or the location of one or more other delivery tool features in the 3D coordinate space may be determined based on the determined location of EM sensors 26. Additionally or alternatively, processor 54 may be configured to determine the estimated location of EV lead features, e.g., the estimated location of EV lead electrodes or the EV lead distal end, based on the EM sensor signals and relative distances of respective EV lead features from sheath distal end 28 or from EM sensors 26 corresponding to when the EV lead 116 is fully inserted through inner open lumen 23. One or any combination of the locations of features of delivery tool 20 and / or EV lead 116 can be mapped onto the AP and lateral views of the intraoperative image data. At block 210, processor 54 may pass the location information derived from the EM sensor signals and registration data to display unit 52 for displaying the one or more locations of delivery tool and / or EV lead features relative to a graphic rendering of the 3D image of the patient’s heart. The locations of delivery tool and / or EV lead features relative to the graphic rendering of the patient’s heart may be superimposed on the intra-operative images received from imaging unit 40 that both of the locations derived from the EM sensor signals and the preoperative image data are registered to.

[0088] It is to be understood that EV lead 116 need not necessarily be advanced within removable outer sheath 22 in order for processing device 50 to determine and display estimated locations of one or more EV lead features. For example, the estimated locations of EV electrodes 124, 126, 128 and 130 may be determined and displayed by display unit 52 relative to the rendering of the patient’s heart in 3D and the AP and lateral fluoroscopicRef. No. A0012739US01 images used to map the EM sensor signal-derived locations to the imaging data of the patient’s heart. The estimated locations of one or more EV lead electrodes 124, 126, 128 and 130 can be determined based on known distances of each electrode from the EM sensors 26 corresponding to when the EV lead 116 is fully advanced within the inner open lumen 23 of sheath 22. To illustrate, when EV lead 116 is fully advanced within open lumen 23, the EV lead distal end 129 may be at or a known distance from sheath distal end 28. Knowing a first distance between EM sensors 26 and sheath distal end 28, a second distance between sheath distal end 28 and the EV lead distal end 129 when the EV lead is fully inserted into sheath 22, and the distances of any of the electrodes 124, 126, 128 and / or 130 from the EV lead distal end 129, the respective locations of any one or more of electrodes 124, 126, 128 and 130 can be estimated by processor 54 from the received EM signals, even before EV lead 116 is advanced within sheath 22. In this way, the estimated locations of the EV lead electrodes can be verified as acceptable locations prior to removing tunneling rod 24 and inserting EV lead 116 into removable outer sheath 22. If the estimated locations of EV lead electrodes are not acceptable, the position of the delivery tool 20 can be adjusted as needed before removing tunneling rod 24.

[0089] Furthermore, it is to be understood that processing device 20 may determine estimated locations of features of EV lead 116 corresponding to the position of EV lead 116 after removable outer sheath 22 is withdrawn from EV lead 116 and the EV lead body 118 relaxes into its normal shape that may include one or more preformed bends or curves. For instance, in the example of EV lead 116 having two pre-formed C-shaped curves carrying electrodes 124 and 126, the mid-point of the electrodes 124 and 126 at the point of greatest excursion of the C-shaped curves may be estimated by processor 54 based on the known geometric relationships, e.g., angles and distances, from the location of lead distal end 129 when EV lead 116 is held in a straightened position within sheath 22 and when sheath 22 is withdrawn and EV lead 116 is relaxed into its preformed shape. In this way, a user can visualize the final estimated locations of one or more of the EV lead electrodes corresponding to a position fully advanced within removable outer sheath 22 and / or corresponding to a position after the outer sheath 22 is withdrawn from its current location within the patient’s body.

[0090] These estimated locations of one or more features of EV lead may be determined by processor 54 prior to removal of tunneling rod 24 to enable adjustments of the deliveryRef. No. A0012739US01 tool position prior to inserting EV lead 116 within removable outer sheath 22. After removing the tunneling rod 24 and advancing EV lead 116 fully within outer sheath 22, any of the determined locations of features of removable outer sheath 22 and / or estimated locations of features of EV lead 116 (in a constrained straightened position and / or in a relaxed curved position) may be redetermined to verify that shifting or migration of the removable outer sheath 22 has not occurred during the removal of tunneling rod 24 and the insertion of EV lead 116.

[0091] A marker, icon, or other graphical indicator of the determined or estimated locations of the one or more features of the delivery tool 20 and / or EV lead 116 may be displayed by display unit 52 as the delivery tool 20 is advanced within patient 12. The marker, icon, or other graphical indicator may be moved in the display, e.g., substantially in real time in some examples, as the delivery tool position changes and may be superimposed on the 2D intraoperative images and graphical rendering of the 3D image of the patient’s heart.

[0092] In some examples, the display presented by display unit 52 may include a target region for the sheath distal end 28 to provide guidance to the clinician. For example, the target region 140 shown in FIGs. 3 A and 3B may be displayed in a GUI. In some cases, when the graphical indicator of the location of sheath distal end 28 is within the target region 140, the clinician can be confident that the delivery tool 20 is well positioned for deployment of EV lead 116. The tunneling rod 24 may be removed, and the EV lead 116 may be advanced through removable outer sheath 22, which can be subsequently withdrawn and removed from the patient leaving the EV lead 116 in place. Display of other indications, e.g., as markers, icons or other graphical indicators, of delivery tool feature locations and / or EV lead feature locations may or may not be included when the target region 140 is displayed by display unit 52, with a confirming indicator when the location of sheath distal end 28 is within target region 140, for guiding the user to position the delivery tool 20 for optimal EV lead placement.

[0093] FIG. 5 is a flow chart 250 of a method for implanting an EV lead according to another example. Identically numbered blocks in flow chart 250 correspond to like- numbered blocks of flow chart 200 described above. In this example, the processing device 50 may be configured to determine 3D boundaries of the heart corresponding to one or more positions during a cardiac cycle (block 203). For example, processor 54 mayRef. No. A0012739US01 be configured to determine boundaries of the heart at its maximum and / or minimum volumes from the 3D image data received at block 202. Accordingly, the 3D image data may include segmentations of the patient’s heart at multiple time points (which may be referred to as 4D images) over the cardiac cycle so that a 3D boundary of the heart wall can be determined in the coordinate system space registered to the 2D intraoperative images, so that the locations of delivery tool 20 and / or EV lead 116 can be mapped relative to the heart wall boundaries at one or more time points of the cardiac cycle based on the EM sensor signals.

[0094] In some examples, processor 54 may determine a 3D boundaries of the heart when the ventricles are at a maximum volume, e.g., an anterior heart wall boundary at end diastole. In addition to or alternatively to determining this end diastolic anterior heart wall boundary, processor 54 may determine 3D boundaries of the heart at its minimum volume of the cardiac cycle, e.g., at a minimum ventricular volume which may coincide with the end systolic ventricular volume. External processing device 50 may store the 3D boundary coordinates for the maximum and / or minimum volume heart wall boundaries in memory 53 to enable distances between the heart wall boundary and the locations of delivery tool features and / or EV lead features to be determined by processor 54 during the implant procedure.

[0095] As described above, processing device 50 may receive intraoperative image data at block 204 and registers the preoperative 3D image data to the intraoperative image data (block 206). Processor 54 receives the EM sensor signals at block 208. At block 210, external processing device 50 may determine the one or more locations of delivery tool features and / or EV lead features as described above, which can be graphically displayed at block 210 relative to a rendering of the 3D preoperative image of the heart based on the registration to the intraoperative image data.

[0096] At block 214, processor 54 may determine if a feature location of the delivery tool 20 and / or EV lead 116 is less than a recommended minimum distance from a heart wall boundary and / or more than a maximum distance from the heart wall boundary. For instance, processor 54 may be configured to compute a minimum distance between the location of sheath distal end 28 (as determined based on a location of EM sensors 26) from the end diastolic anterior heart wall boundary to determine if the delivery tool 20 is being advanced too close to the heart, e.g., too deep relative to the patient’s sternum.Ref. No. A0012739US01Additionally or alternatively, external processing device 50 may be configured to compute a maximum distance between the sheath distal end 28 and the end systolic anterior heart wall boundary to determine if the delivery tool 20 is being advanced too far away from the heart. When the final EV lead position is too far from the patient’s heart, relatively high capture thresholds and / or low cardiac signal strength may result.

[0097] In other examples, an estimated location of the EV lead distal end 129 and / or an estimated location of an electrode carried by the EV lead 116 may be determined based on the location of the EM sensors 26. A maximum and / or minimum distance of the estimated location of a feature of EV lead 116 (based on the current position of the removable outer sheath 22) to the heart wall boundary (at minimum volume and / or maximum volume) may be computed by processor 54 at block 214.

[0098] Processor 54 may compare determined distance(s) to the heart wall boundary to a minimum recommended threshold distance and / or to a maximum recommended threshold distance at block 214. If a determined distance from a delivery tool feature and / or EV lead feature to a heart wall boundary falls outside a recommended distance from the computed heart wall boundary, e.g., less than a minimum recommended threshold distance and / or more than a maximum recommended threshold distance, processor 54 may generate an alert at block 216. The alert may be generated as a visual and / or audible alert to the clinician, e.g., displayed or broadcast by display unit 52, prompting the user to re-evaluate and adjust the position or pathway of advancement of the delivery tool 20.

[0099] External processing device 50 may update the delivery tool feature location coordinates as it is being advanced, for example, based on the EM sensor signals being received. In this way, the displayed location of a delivery tool feature location and / or an estimated EV lead feature location can be updated on display unit 52 (at block 210). This process may continue until the clinician stops advancement of the delivery tool 20 and the determined delivery tool feature location(s) and / or estimated EV lead feature location(s) fall within a recommended distance threshold or range relative to the heart wall boundaries. It is noted that the estimated EV lead feature location(s) may be determined and displayed prior to actually inserting the EV lead through the removable outer sheath 22 so that any adjustments of the delivery tool position can be made prior to withdrawing the tunneling rod 24.Ref. No. A0012739US01

[0100] In some examples, processor 54 may confirm that the location of the sheath distal end 29 (or other delivery tool feature and / or EV lead feature) falls within a specified target region (at block 220), e.g., target region 140 shown in FIGs. 3A and 3B. If not, processor 54 may generate an alert at block 216 to notify the clinician, e.g., via display unit 52, to adjust the delivery tool position. The boundaries of the target region 140 may be stored in memory 53 of processing device 50 according to 3D coordinates in the coordinate system space corresponding to the intraoperative imaging data and localization of the EM sensors 26. Once the delivery tool location is confirmed to be advanced within recommended distances from the heart (block 216) and / or is positioned within a target region (block 220), processor 54 may generate a notification at block 228 to indicate that the delivery tool 20 is acceptably positioned for EV lead deployment.

[0101] The clinician may remove the tunneling rod 24 from the removable outer sheath 22 and advance EV lead 116 through the lumen 23 of removable outer sheath 22 in response to the notification generated and displayed at block 228. The removable outer sheath 22 and / or EV lead 116 may include guides or stops that facilitate full insertion of the EV lead 116, e.g., so that its distal end 129 is substantially aligned with the sheath distal end 28 or a known distance therefrom without being over-advanced.

[0102] In some examples, processing device 50 may determine an orientation of the removable outer sheath 22 based on the EM sensor signals at block 222. The orientation may be determined be determining the pitch, roll, and / or yaw of the sheath distal end 28 in various examples. One or more of the pitch, roll and / or yaw angles with respect to respective axes or planes of the 3D coordinate system of the EM field may be determined and compared to respective target orientation angles or target orientation angle ranges at block 224 to verify that an orientation angle meets a threshold angle. When any of the orientation angles are out of a target orientation angle range, for example when an orientation angle does not meet a threshold angle at block 224, the processor 54 may generate an alert at block 226. The display unit 52 may display a user prompt in response to the generated alert to prompt the user to rotate sheath 22 and / or adjust the position of tunneling rod 24 to adjust the orientation of the removable outer sheath to promote a desired orientation of the sheath 22 prior to delivery of the EV lead. A threshold angle that defines a target orientation angle or target orientation angle range may be determined from empirical data obtained from a population of patients based on acute and / or chronicRef. No. A0012739US01 outcomes of the EV lead performance. The threshold angle(s) may be stored in memory 53 of processing device 50.

[0103] Processor 54 may redetermine one or more delivery tool feature locations, EV lead feature locations, and / or removable outer sheath orientation after the EV lead 116 is fully advanced within removable outer sheath 22 to verify that the removable outer sheath 22 is still in the acceptable deployment position and orientation. Processing device 50 and display unit 52 may cooperatively generate a confirmation notification at block 222. In response to the confirmation notification, the clinician may withdraw and remove the removal outer sheath 22 leaving the EV lead 116 in the target implant position.

[0104] The EV lead 116 may be connected to an external pacing system analyzer or ICD 114 (shown in FIGs. 3 A — 3C) for performing any desired testing of EV lead 116 or ICD system 100, e.g., reviewing cardiac signal sensing, performing pacing capture threshold testing and / or performing defibrillation threshold testing. The proximal end of EV lead 116 may be tunneled to a subcutaneous pocket for connection to ICD 114 after confirmation of the final EV lead position.

[0105] FIG. 6 is an illustration of a graphical display 300 be that may be presented to a clinician by display unit 52 according to the techniques disclosed herein. Processor 54 of processing device 50 may provide intraoperative image data, registered preoperative image data, and feature location information determined from EM sensor signals to display unit 52 for generating a display of the interoperative image(s) superimposed by a graphical rendering of the preoperative image data. In the example shown, an AP fluoroscopic image 302 and a left lateral fluoroscopic image 304 may be displayed. The graphical renderings 306 and 308 of the patient’s heart registered to the intraoperative images 302 and 304 may each be displayed as a 3D rendering in the respective AP and left lateral views. If the ICD 114 has already been positioned in a subcutaneous pocket at the time that the intraoperative images are obtained, the location of the ICD 114 may be viewed in the AP and lateral views.

[0106] The intraoperative images may be acquired before or after the delivery tool 20 is advanced in the patient’s body. As such, the delivery tool 20 may or may not be visible in the intraoperative images 302 and 304. However, the AP view markers 62 and the lateral view markers 64 may be positioned relative to the patient prior to obtaining the intraoperative images 302 and 304 such that fiducial points 362 (corresponding to AP viewRef. No. A0012739US01 markers 62) and fiducial points 364 (corresponding to lateral view markers 64) can be observed in the respective AP and lateral views.

[0107] Once the intraoperative images 302 and 304 are registered to preoperative image data for registering the 3D graphical rendering of the patient’s heart to the intraoperative images 302 and 304, additional intraoperative images may not be needed. The locations of features of delivery tool 20 and / or EV lead 116 can be determined or estimated by processing device 50 based on the EM sensor signals as the delivery tool 20 is advanced from an entry point to a position deemed acceptable for deployment of the EV lead 116. These locations can be registered to the intraoperative images 302 and 304, facilitated by the locations of fiducial points 362 and 364, and updated in the graphical display 300 as the delivery tool 20 position changes.

[0108] In the example shown, a graphical indicator 329 displayed by display unit 52 based on location information received from processor 54 may mark the determined location of the sheath distal end 28. Additionally or alternatively, one or more graphical indicators 324, 326, 328, and / or 330 displayed by display unit 52 may mark the determined, respective locations of the EV lead electrodes 124, 126, 128 and / or 130 based on estimated location information received from processor 54. The graphical indicators may be unique, e.g., in shape or color, to distinguish between the delivery tool feature or EV lead feature that is being represented. While not shown explicitly in FIG. 6, it is to be understood that a key may be provided to indicate what delivery tool feature or EV lead feature each graphical indicator represents. For instance, in the example shown, a circle 329 represents the sheath distal end 28, X’s represents the defibrillation electrodes 124 and 126 and rectangles 328 and 330 represent the ring electrodes 128 and 130 of EV lead 116.

[0109] In the example shown, the graphical indicator 329 may mark the location of sheath distal end 28 after the delivery tool 20 has been advanced to a substernal lead deployment position. The target region 340 may be represented in the graphical display 300 by a dashed line, shaded area, or other representation. When the graphical indicator 329 corresponding to the location of sheath distal end 28 falls within the target region 340, processor 54 may generate a notification to notify to the user that the delivery tool 20 is in an acceptable position for EV lead deployment. For example in response to the generated notification, the target region 340 and / or the graphical indicator 329 corresponding to sheath distal end 28 may change color (e.g., turn from red to green) or change fromRef. No. A0012739US01 blinking to solid. Additionally or alternatively, a text user prompt 310 may be displayed to notify the user that the delivery tool position is acceptable; no further adjustment of the delivery tool position is required for positioning EV lead 116 at the implant site. Additionally or alternatively an audible notification may be broadcast by a speaker 312 of display unit 52 in response to the notification generated by processor 54. In response to the notification, which may be observed by the clinician as the graphical indicator 329 being within target region 340 and / or any of the other examples given above, the clinician may remove the tunneling rod 24 and insert the EV lead 116 into sheath 22.

[0110] In the example shown, the locations of EV lead electrodes 124, 126, 128 and 130 represented by graphical indicators 324, 326, 328 and 330, respectively, may indicate the estimated locations of the EV lead electrodes when EV lead 116 is constrained within the inner open lumen 23 of removable outer sheath 22. The user prompt 310 may be displayed by display unit 54 in response to a notification from processor 54 indicating that the distance of at least one estimated EV lead electrode location is within an acceptable range from a heart wall boundary in some examples. In response to the user prompt 310, the clinician may advance the EV lead 116 within sheath 22 and withdraw and remove sheath 22. In addition or alternatively to user prompt 310, the graphical indicators 324, 326, 328 and / or 330 may be displayed in a manner that indicates to the clinician that the estimated locations of the respective EV lead electrodes are at an acceptable distance from a heart wall boundary. For example, the graphical indicator 324, 326, 328 and / or 330 may change in color from red to green, change from blinking to solid, or other noticeable change to notify the clinician that the removable outer sheath 22 is acceptably positioned for EV lead placement.[oni] FIG. 7 is a diagram of a graphical display 301 that may be presented by display unit 52 according to another example. Identical reference numbers correspond to the reference numbers shown in FIG. 6 and described above. However, in this example, the graphical indicators 324 and 326 that correspond to the estimated locations of the defibrillation electrodes 124 and 126 of EV lead 116 are shown offset from the graphical indicators 328 and 330 corresponding to EV lead pacing and sensing electrodes 128 and 130. In this instance, processor 54 may pass the location information of the EV lead electrodes 124, 126, 128 and 130 that corresponds to their respective estimated locations after EV lead 116 is released from the removable outer sheath 22 and relaxes into itsRef. No. A0012739US01 normal, preformed shape. In the example of the “epsilon” shaped EV lead 116 shown in FIG. 3A, for example, the midpoints of defibrillation electrodes 124 and 126 may be offset from the center axis of pacing and sensing electrodes 128 and 130. As such, graphical indicators 324 and 326 may be displayed at an estimated or expected location of the defibrillation electrodes 124 and 126 when the EV lead 116 is fully advanced into the removable outer sheath 22 in its current position and the removable outer sheath 22 is retracted and withdrawn from EV lead 116. The displayed estimated locations of graphical indicators 324 and 326 may be presented in graphical display 301 to correspond to the estimated locations of defibrillation electrodes 124 and 126 when EV lead 116 relaxes into its preformed shape unconstrained by removable outer sheath 22. The displayed estimated locations of a feature of the EV lead 116, therefore, may be radially offset from the removable outer sheath 22 (e.g., in a location that is located outside the open lumen 23), when the EV lead body is expected to relax into a preformed bent or curved shape when released from the open lumen of the outer sheath 22.

[0112] The estimated locations of the defibrillation electrodes 124 and 126 when released from a current position of the removable outer sheath 22 may be based on the determined location of a delivery tool feature (e.g., delivery tool distal end 28) and the determined orientation of the removable outer sheath 22. As described above, processor 54 may be configured to determine one or more orientation angles (e.g., pitch, roll and / or yaw) of the EM sensors 26 with respect to the axes of the 3D coordinate space of the EM field. In some instances, when the EV lead 116 is released from sheath 22 when it is not rotated into a desired orientation, the preformed curves of the “epsilon” shaped EV lead 116 may relax in a direction that is not considered optimal, e.g., generally toward the patient’s left instead of toward the patient’s right. As such, in some examples, the processor 54 may generate a notification that can be displayed in the user prompt 310 by display unit 52 to indicate to the clinician to either adjust the orientation of the removable outer sheath 22 or that the orientation is acceptable and the EV lead may be advanced through sheath 22 for final lead placement. When the orientation of the removable outer sheath 22 falls within desired orientation angles, alignment of the EV lead 116 advanced within removable outer sheath 22 according to one or more guides or markers as described above can promote an optimal orientation of a preformed lead body and / or directional electrodes.

[0113] Further disclosed herein is the subject matter of the following examples:Ref. No. A0012739US01

[0114] Example 1. A medical device system including processing circuitry and a delivery tool configured to deliver an extravascular lead to an implant site of a patient via a non- transvenous pathway. The delivery tool may include a removable outer sheath configured to be disposed over a tunneling rod. The removable outer sheath may include an outer wall extending from a sheath proximal end to a sheath distal end and an open lumen defined by the outer wall. The open lumen extending from the sheath proximal end may be configured to receive the tunneling rod and further configured to receive the extravascular lead after the tunneling rod is removed from the removable outer sheath. The removable outer sheath may further include at least one location sensor disposed at a known distance from a feature of the removable outer sheath. The processing circuitry may be configured to receive first patient body image data, receive second patient body image data, register the first patient body image data and the second patient body image data, receive a signal from the at least one location sensor, and determine from the location sensor signal a first location of the feature of the removable outer sheath in a coordinate system space corresponding to the second patient body image data. The processing circuitry may provide to a display unit the first location of the feature of the removable outer sheath and the registered first patient body image data and the second patient body image data for displaying, by the display unit, a first location representation of the first location of the feature of the removable outer sheath relative to a graphical rendering of at least a portion of the first patient body image data.

[0115] Example 2. The medical device system of example 1 wherein the delivery tool includes the elongated tunneling rod having a rod distal end and a rod proximal end. The elongated tunneling rod being sized for insertion through the sheath open lumen. The delivery tool may further include a handle coupled to the rod proximal end.

[0116] Example 3. The medical device system of any one of examples 1 — 2 wherein the processing circuitry is further configured to estimate, from the location sensor signal, one or more second locations of a respective one or more lead features of the extravascular lead in the coordinate system space corresponding to the second patient body image data. The processing circuitry may provide the one or more second locations of the one or more lead features to the display unit for displaying a second location representation for each of the one or more second locations of the respective one or more lead features relative to the graphical rendering of at least the portion of first patient body image data.Ref. No. A0012739US01

[0117] Example 4. The medical device system of example 3 wherein the processing circuitry is further configured to, based on at least one of the location sensor signal or the first location, estimate the one or more second locations of the respective one or more lead features before the extravascular lead is advanced within the open lumen of the removable outer sheath.

[0118] Example 5. The medical device system of any one of examples 3 — 4 wherein the processing circuitry is further configured to, based on at least one of the location sensor signal or the first location, estimate at least one of the one or more second locations as being a location within the open lumen of the removable outer sheath.

[0119] Example 6. The medical device system of any one of examples 3 — 5 wherein the processing circuitry is further configured to, based on at least one of the location sensor signal or the first location, estimate at least one of the one or more second locations as being a location displaced radially outside the open lumen of the removable outer sheath corresponding to an unconstrained relaxed position of the extravascular lead after release from the removable outer sheath.

[0120] Example 7. The medical device system of any one of examples 3 — 6 wherein the processing circuitry is further configured to determine the one or more second locations by determining at least one electrode location corresponding to an electrode carried by the extravascular lead.

[0121] Example 8. The medical device system of any one of examples 1 — 7 wherein the processing circuitry is further configured to determine that the first location is within a specified target region of the registered first image data and second image data and generate a notification in response to determining that the first location is in the specified target region to inform a user that the delivery tool is in an acceptable position for deploying the extravascular lead.

[0122] Example 9. The medical device system of any one of examples 1 — 8 wherein the processing circuitry is further configured to determine an anatomical landmark location from the first body image data and determine a distance from the anatomical landmark location to the first location. The processing circuitry may be configured to determine that the distance is outside a threshold distance, generate an alert in response to determining that the distance is outside the threshold distance and provide the alert to the display unit for displaying a user prompt to adjust a position of the delivery tool.Ref. No. A0012739US01

[0123] Example 10. The medical device system of example 9 wherein the processing circuitry is further configured to determine the anatomical landmark location from the first patient body image data by determining at least a first heart border.

[0124] Example 11. The medical device system of example 10 wherein the processing circuitry is further configured to determine at least the first heart border by determining one of an end diastolic ventricular volume heart border or an end systolic ventricular volume heart border.

[0125] Example 12. The medical device system of any one of examples 10 — 11 wherein the processing circuitry is further configured to determine the first heart border as the end systolic ventricular volume heart border and determine the second heart border as the end diastolic ventricular volume heart border. The processing circuitry may be further configured to determine a first distance between the first location and the end systolic ventricular volume heart border, determine a second distance between the first location and the end diastolic ventricular volume heart border and detect that at least one of the first distance or the second distance is outside a threshold range. The processing circuitry may generate the alert in response to at least one of the first distance or the second distance being outside the threshold range.

[0126] Example 13. The medical device system of any one of examples 1 — 12 wherein the processing circuitry is further configured to receive the first patient body image data as three dimensional image data.

[0127] Example 14. The medical device system of any one of examples 1 — 13 wherein the processing circuitry is further configured to receive the second patient body image data as two dimensional image data in at least a first planar view and a second planar view, the second planar view different than the first planar view.

[0128] Example 15. The medical device system of any one of examples 1 — 14 wherein the processing circuitry is further configured to provide to the display unit the registered first patient body image data and the second patient body image data for generating the graphical rendering of at least a portion of the first patient body image data by generating a three dimensional graphical rendering of a heart of the patient.

[0129] Example 16. The medical device system of any one of examples 1 — 15 wherein the location sensors comprise electromagnetic sensors.Ref. No. A0012739US01

[0130] Example 17. The medical device system of example 16 further comprising an electromagnetic field emitting device configured to emit an electromagnetic field and a plurality of fiducial point markers in the emitted electromagnetic field. The processing circuitry may be further configured to determine the first location of the feature of the removable outer sheath by determining the first location in the coordinate system space corresponding to the second patient body image data using the plurality of fiducial point markers.

[0131] Example 18. The medical device system of any one of examples 1 — 17 wherein the processing circuitry is further configured to determine from the at least one location sensor signal at least one orientation angle of the sheath distal end.

[0132] Example 19. The medical device system of example 18 wherein the processing circuitry is further configured to compare the at least one orientation angle to a threshold angle, determine that the orientation angle does not meet the threshold angle, generate a notification in response to the orientation angle not meeting the threshold angle and provide the notification to the display unit for displaying a user prompt to adjust the delivery tool.

[0133] Example 20. The medical device of any one of examples 1 — 19 wherein the processing circuitry is further configured to determine based on at least the first location that the delivery tool is in an acceptable position for deployment of the extravascular lead and generate a notification in response to determining that the delivery tool is in an acceptable position for deployment of the extravascular lead. The processing circuitry may provide the notification to the display unit for displaying, by the display unit, a user prompt to advance the extravascular lead through the removable outer sheath.

[0134] Example 21. A method comprising receiving first patient body image data, receiving second patient body image data, registering the first patient body image data and the second patient body image data and receiving a signal from at least one location sensor disposed at a known distance from a feature of a removable outer sheath of a delivery tool configured to deliver an extravascular lead to an implant site of a patient via a non- transvenous pathway. The removable outer sheath may include an outer wall extending from a sheath proximal end to a sheath distal end and an open lumen defined by the outer wall. The open lumen may extend from the sheath proximal end for receiving a tunneling rod. The open lumen may be further configured to receive the extravascular lead after theRef. No. A0012739US01 tunneling rod is removed from the removable outer sheath. The method may further include determining from the location sensor signal a first location of the feature of the removable outer sheath in a coordinate system space corresponding to the second patient body image data. The method may further include providing to a display unit the first location of the feature of the removable outer sheath and the registered first patient body image data and the second patient body image data for displaying, by the display unit, a first location representation of the first location of the feature of the removable outer sheath relative to a graphical rendering of at least a portion of first patient body image data.

[0135] Example 22. The method of example 21 further comprising estimating, from the location sensor signal, one or more second locations of a respective one or more lead features of the extravascular lead in the coordinate system space corresponding to the second patient body image data. The method may include providing the one or more second locations of the one or more lead features to the display unit for displaying a second location representation for each of the one or more second locations of the respective one or more lead features relative to the graphical rendering of at least the portion of first patient body image data.

[0136] Example 23. The method of example 22 further comprising, based on at least one of the location sensor signal or the first location, estimating the one or more second locations of the respective one or more lead features before the extravascular lead is advanced within the open lumen of the removable outer sheath.

[0137] Example 24. The method of any one of examples 22 — 23 further comprising, based on at least one of the location sensor signal or the first location, estimating at least one of the one or more second locations as being a location within the open lumen of the removable outer sheath.

[0138] Example 25. The medical device system of any one of examples 22 — 24 further comprising, based on at least one of the location sensor signal or the first location, estimating at least one of the one or more second locations as being a location displaced radially outside the open lumen of the removable outer sheath corresponding to an unconstrained relaxed position of the extravascular lead after release from the removable outer sheath.Ref. No. A0012739US01

[0139] Example 26. The method of any one of examples 22 — 25 further comprising determining the one or more second locations by determining at least one electrode location corresponding to an electrode carried by the extravascular lead.

[0140] Example 27. The method of any one of examples 21 — 26 further including determining that the first location is within a specified target region of the registered first image data and second image data. The method may further include generating a notification in response to determining that the first location is in the specified target region to inform a user that the delivery tool is in an acceptable position for deploying the extravascular lead.

[0141] Example 28. The method of any one of examples 21 — 27 further including determining an anatomical landmark location from the first patient body image data and determining a distance from the anatomical landmark location to the first location. The method may further include determining that the distance is outside a threshold distance, generating an alert in response to determining that the distance is outside the threshold distance and providing the alert to the display unit for displaying a user prompt to adjust a position of the delivery tool.

[0142] Example 29. The method of example 28 further including determining the anatomical landmark location from the first patient body image data by determining at least a first heart border.

[0143] Example 30. The method of example 29 further including determining at least the first heart border by determining one of an end diastolic ventricular volume heart border or an end systolic ventricular volume heart border.

[0144] Example 31. The method of any one of examples 29 — 30 further including determining the first heart border as the end systolic ventricular volume heart border, determining the second heart border as the end diastolic ventricular volume heart border, determining a first distance between the first location and the end systolic ventricular volume heart border, determining a second distance between the first location and the end diastolic ventricular volume heart border. The method may further include detecting that at least one of the first distance or the second distance is outside a threshold range. The method may include generating the alert in response to at least one of the first distance or the second distance being outside the threshold range.Ref. No. A0012739US01

[0145] Example 32. The method of any one of examples 21 — 31 further comprising receiving the first patient body image data as three dimensional image data.

[0146] Example 33. The method of any one of examples 21 — 32 further including receiving the second patient body image data as two dimensional image data in at least a first planar view and a second planar view, the second planar view different than the first planar view.

[0147] Example 34. The method of any one of examples 21 — 33 further including providing to the display unit the registered first patient body image data and the second patient body image data for generating the graphical rendering of at least a portion of the first patient body image data by generating a three dimensional graphical rendering of a heart of the patient.

[0148] Example 35. The method of any one of examples 21 — 34 further including receiving the signal from the at least one location sensor by receiving an electromagnetic sensor signal.

[0149] Example 36. The method of example 35 further including emitting an electromagnetic field by an emitting device where a plurality of fiducial point markers are in the emitted electromagnetic field and determining the first location of the feature of the removable outer sheath by determining the first location in the coordinate system space corresponding to the second patient body image data using the plurality of fiducial point markers.

[0150] Example 37. The method of any one of examples 21 — 36 further including determining from the at least one location sensor signal at least one orientation angle of the sheath distal end.

[0151] Example 38. The method of example 37 further including comparing the at least one orientation angle to a threshold angle, determining that the orientation angle does not meet the threshold angle, and generating a notification in response to the orientation angle not meeting the threshold angle. The method may further include providing the notification to the display unit for displaying a user prompt to adjust the delivery tool.

[0152] Example 39. The method of any one of examples 21 — 38 further including determining, based on at least the first location, that the delivery tool is in an acceptable position for deployment of the extravascular lead and generating a notification in response to determining that the delivery tool is in an acceptable position for deployment of theRef. No. A0012739US01 extravascular lead. The method may further include providing the notification to the display unit for displaying, by the display unit, a user prompt to advance the extravascular lead through the removable outer sheath.

[0153] Example 40. A non-transitory, computer readable medium storing a set of instructions that, when executed by processing circuitry of a medical device system, cause the medical device system to receive first patient body image data, receive second patient body image data and register the first patient body image data and the second patient body image data. The instructions further cause the medical device system to receive a signal from the at least one location sensor disposed at a known distance from a feature of a removable outer sheath of a delivery tool configured to deliver an extravascular lead to an implant site of a patient via a non-transvenous pathway, the removable outer sheath including an outer wall extending from a sheath proximal end to a sheath distal end and an open lumen defined by the outer wall. The open lumen extending from the sheath proximal end for receiving a tunneling rod is further configured to receive the extravascular lead after the tunneling rod is removed from the removable outer sheath. The instructions may further cause the medical device system to determine from the location sensor signal a location of the feature of the removable outer sheath in a coordinate system space corresponding to the second patient body image data. The instructions may further cause the medical device system to provide to a display unit the location of the feature of the removable outer sheath and the registered first patient body image data and the second patient body image data for displaying, by the display unit, a representation of the location of the feature of the removable outer sheath relative to a graphical rendering of at least a portion of the first patient body image data.

[0154] It should be understood that, depending on the example, certain acts or events of any of the methods described herein can be performed in a different sequence, may be added, merged, or left out altogether (e.g., not all described acts or events are necessary for the practice of the method). Moreover, in certain examples, acts or events may be performed concurrently, e.g., through multi -threaded processing, interrupt processing, or multiple processors, rather than sequentially. In addition, while certain aspects of this disclosure are described as being performed by a single circuit or unit for purposes of clarity, it should be understood that the techniques of this disclosure may be performed by a combination of units or circuits associated with, for example, a medical device.Ref. No. A0012739US01

[0155] In one or more examples, the functions described 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. Computer-readable media may include computer-readable storage media, which corresponds to a tangible medium such as data storage media (e.g., RAM, ROM, EEPROM, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer).

[0156] 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 logic arrays (FPLAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term “processor,” as used herein may refer to any of the foregoing structure or any other structure suitable for implementation of the techniques described herein. Also, the techniques could be fully implemented in one or more circuits or logic elements.

[0157] Thus, a medical device has been presented in the foregoing description with reference to specific examples. It is to be understood that various aspects disclosed herein may be combined in different combinations than the specific combinations presented in the accompanying drawings. It is appreciated that various modifications to the referenced examples may be made without departing from the scope of the disclosure and the following claims.

Claims

Ref. No. A0012739US01WHAT IS CLAIMED IS:

1. A medical device system comprising: a delivery tool configured to deliver an extravascular lead to an implant site of a patient via a non-transvenous pathway, the delivery tool comprising: a removable outer sheath configured to be disposed over a tunneling rod, the removable outer sheath comprising: an outer wall extending from a sheath proximal end to a sheath distal end; an open lumen defined by the outer wall, the open lumen extending from the sheath proximal end for receiving the tunneling rod, the open lumen further configured to receive the extravascular lead after the tunneling rod is removed from the removable outer sheath; and at least one location sensor disposed at a known distance from a feature of the removable outer sheath; and processing circuitry configured to: receive first patient body image data; receive second patient body image data; register the first patient body image data and the second patient body image data; receive a signal from the at least one location sensor; determine from the location sensor signal a first location of the feature of the removable outer sheath in a coordinate system space corresponding to the second patient body image data; and provide to a display unit the first location of the feature of the removable outer sheath and the registered first patient body image data and the second patient body image data for displaying, by the display unit, a first location representation of the first location of the feature of the removable outer sheath relative to a graphical rendering of at least a portion of the first patient body image data.

2. The medical device system of claim 1 wherein the delivery tool further comprises:Ref. No. A0012739US01 the elongated tunneling rod having a rod distal end and a rod proximal end, the elongated tunneling rod being sized for insertion through the sheath open lumen; and a handle coupled to the rod proximal end.

3. The medical device system of any one of claims 1 — 2 wherein the processing circuitry is further configured to: estimate, from the location sensor signal, one or more second locations of a respective one or more lead features of the extravascular lead in the coordinate system space corresponding to the second patient body image data; and provide the one or more second locations of the one or more lead features to the display unit for displaying a second location representation for each of the one or more second locations of the respective one or more lead features relative to the graphical rendering of at least the portion of first patient body image data.

4. The medical device system of claim 3 wherein the processing circuitry is further configured to, based on at least one of the location sensor signal or the first location, estimate the one or more second locations of the respective one or more lead features before the extravascular lead is advanced within the open lumen of the removable outer sheath.

5. The medical device system of any one of claims 3 — 4 wherein the processing circuitry is further configured to, based on at least one of the location sensor signal or the first location, estimate at least one of the one or more second locations as being a location within the open lumen of the removable outer sheath.

6. The medical device system of any one of claims 3 — 5 wherein the processing circuitry is further configured to, based on at least one of the location sensor signal or the first location, estimate at least one of the one or more second locations as being a location displaced radially outside the open lumen of the removable outer sheath corresponding to an unconstrained relaxed position of the extravascular lead after release from the removable outer sheath.Ref. No. A0012739US017. The medical device system of any one of claims 3 — 6 wherein the processing circuitry is further configured to determine the one or more second locations by determining at least one electrode location corresponding to an electrode carried by the extravascular lead.

8. The medical device system of any one of claims 1 — 7 wherein the processing circuitry is further configured to: determine an anatomical landmark location from the first patient body image data; determine a distance from the anatomical landmark location to the first location; determine that the distance is outside a threshold distance; generate an alert in response to determining that the distance is outside the threshold distance; and provide the alert to the display unit for displaying a user prompt to adjust a position of the delivery tool.

9. The medical device system of claim 8 wherein the processing circuitry is further configured to determine the anatomical landmark location from the first patient body image data by determining at least a first heart border.

10. The medical device system of claim 9 wherein the processing circuitry is further configured to determine at least the first heart border by determining one of an end diastolic ventricular volume heart border or an end systolic ventricular volume heart border.

11. The medical device system of any one of claims 1 — 10 wherein the processing circuitry is further configured to: receive the first patient body image data as three dimensional image data; receive the second patient body image data as two dimensional image data in at least a first planar view and a second planar view, the second planar view different than the first planar view; andRef. No. A0012739US01 provide to the display unit the registered first patient body image data and the second patient body image data for generating the graphical rendering of at least a portion of the first patient body image data by generating a three dimensional graphical rendering of a heart of the patient.

12. The medical device system of any one of claims 1 — 11 wherein the location sensors comprise electromagnetic sensors.

13. The medical device system of claim 12 further comprising: an electromagnetic field emitting device configured to emit an electromagnetic field; a plurality of fiducial point markers in the emitted electromagnetic field; wherein the processing circuitry is further configured to determine the first location of the feature of the removable outer sheath by determining the first location in the coordinate system space corresponding to the second patient body image data using the plurality of fiducial point markers.

14. The medical device system of any one of claims 1 — 13 wherein the processing circuitry is further configured to: determine from the at least one location sensor signal at least one orientation angle of the sheath distal end; compare the at least one orientation angle to a threshold angle; determine that the orientation angle does not meet the threshold angle; generate a notification in response to the orientation angle not meeting the threshold angle; and provide the notification to the display unit for displaying a user prompt to adjust the delivery tool.

15. The medical device of any one of claims 1 — 14 wherein the processing circuitry is further configured to: determine based on at least the first location that the delivery tool is in an acceptable position for deployment of the extravascular lead;Ref. No. A0012739US01 generate a notification in response to determining that the delivery tool is in an acceptable position for deployment of the extravascular lead; and provide the notification to the display unit for displaying, by the display unit, a user prompt to advance the extravascular lead through the removable outer sheath.

Images