Patent Description:
Some types of implantable medical device (IMD) systems, such as cardiac pacemaker or implantable cardioverter defibrillator systems, may be used to provide cardiac sensing and therapy for a patient via one or more electrodes. Some IMDs include an implantable housing that encloses a pulse generator and other electronic components, which may be configured to be implanted subcutaneously in the chest of the patient, as an example. The IMD may be connected to one or more implantable medical electrical leads that include one or more electrodes. The leads may be configured such that the electrodes may, as examples, be implanted within the heart, e.g., transvenous leads, or outside of the heart and vasculature, e.g., extravascular leads. Extravascular leads of such IMD systems may be configured such that the electrodes, e.g., located on a distal portion of the lead, are implanted subcutaneously, substemally, or in other extravascular locations. <CIT> relates to extravascular lead designs for optimized pacing and sensing having segmented, partially electrically insulated defibrillation coils.

In general, the disclosure is directed to devices, systems, and techniques for using a medical device lead having an arrangement of electrodes that provides a set of electrode vectors for sensing electrical signals and/or providing electrical therapy. When used for sensing cardiac electrogram signals and/or delivering cardiac pacing, for example, the vectors have differing spatial positions and orientations relative to the heart. In some examples, a resting or implant state of at least a portion of the medical device lead may be curvilinear, positioning the electrodes such that at least two of the set of vectors are not parallel. Non-parallel vectors may enable a medical device coupled to the medical device lead to sense cardiac electrogram signals from different perspectives relative to the heart, or deliver electrical therapy from different perspectives relative to the heart.

Electric signals may be sensed with reference to two points. For example, a medical device may measure a difference in voltage between two electrodes, thus establishing a sensing electrode vector between the two electrodes. The ability to sense according to the set of vectors provided by a medical device lead configured according to the techniques of this disclosure may increase the probability that the medical device will be able to detect and process cardiac depolarizations and other features of a cardiac electrogram, e.g., for determining a therapy to deliver to the patient. Similarly, therapy delivered via different electrical therapy vectors may be differently able to capture target tissue, and the ability of a medical device to select from the set of vectors may increase the probability that therapy is effective and/or allow selection of a vector whose therapy captures the tissue with relatively lower energy consumption.

An example medical device lead may include at least one defibrillation electrode. A defibrillation electrode, in some examples, may be disposed along a curvilinear portion of the medical device lead. The defibrillation electrode may include a proximal coated portion, a distal coated portion, and an uncoated portion between the proximal coated portion and the distal coated portion. The coated portions of the defibrillation electrode may be configured to allow conduction of relatively higher voltage signals and prevent conduction of relatively lower voltage signals. As such, in some cases, the proximal and distal coated portions may be configured to conduct defibrillation pulses, prevent transmission of pacing pulses, and prevent sensing of cardiac depolarizations. The uncoated portion of the defibrillation electrode, in some cases, may be configured to conduct defibrillation pulses, conduct pacing pulses, and allow sensing of cardiac depolarizations. In this way, the uncoated portion of the defibrillation electrode may be configured to, in combination with other electrodes, form vectors for detecting cardiac depolarizations and other cardiac electrical activity, and form cardiac pacing vectors.

In some examples, the defibrillation electrode is disposed along a curvilinear portion of the medical device lead, causing the defibrillation electrode to form an arc, where the uncoated portion of the defibrillation electrode is located at a peak of the arc. Additionally, in some cases, a first pace/sense electrode is disposed on the medical device lead proximal to the defibrillation electrode and a second pace/sense electrode is disposed on the medical device lead distal to the defibrillation electrode. As such, in examples where the defibrillation electrode is arc shaped with the uncoated portion located at the peak of the arc, the uncoated portion of the defibrillation electrode is displaced from an axis between the first pace/sense electrode and the second pace-sense electrode. In this way, the first pace/sense electrode, the second pace/sense electrode, and the uncoated portion of the defibrillation electrode may form three possible vectors: a first vector between the first pace/sense electrode and the second pace/sense electrode, a second vector which extends between the first pace/sense electrode and the uncoated portion, and a third vector between the second pace/sense electrode and the uncoated portion.

The techniques of this disclosure may provide one or more advantages. For example, straight or near-straight medical device leads, or leads of any shape where the pace/sense electrode are located on or near a common axis, might only be able to sense cardiac depolarizations according to vectors that are aligned with a single axis. Example leads having a curvilinear shape, in contrast, may be configured with non-coaxial electrodes that are configured to form vectors that form angles with each other. For example, a first line that passes through the first pace/sense electrode and the second pace/sense electrode may form an angle with a second line that passes through the first pace/sense electrode and the uncoated portion of the defibrillation electrode. Propagation of electric signals during cardiac cycles varies from patient to patient. For example, the heart of each patient may be set slightly differently within the chest cavity, causing a direction of electric depolarizations to vary between patients. As such, it may be beneficial to provide the option to sense cardiac depolarizations according to vectors that are angularly displaced relative to one another, in order to increase a probability of accurately capturing and processing cardiac depolarizations in a large number of patients.

Additionally, it may be beneficial to include an uncoated portion of the defibrillation electrode that is placed at an apex of the curvilinear figure of the defibrillation electrode, where the uncoated portion is relatively small compared to a size of the defibrillation electrode. For example, by making the uncoated portion relatively small compared to the size of the defibrillation electrode, the IMD may be able to increase a length of the vectors and increase an angle that the vectors form with each other. Furthermore, use of an uncoated portion of a defibrillation electrode to provide the set cardiac sensing and/or pacing vectors, instead of the addition of dedicated pace/sense electrodes, may allow a defibrillation electrode and an electrode for pacing and sensing to share a desired position along the medical lead relative to the heart, and may avoid the addition of electrical conductors and connections associated with additional pace/sense electrodes to the lead. The proximal coated portion and the distal coated portion of the defibrillation electrode may also decrease an amount of passive shunting that occurs in signals sensed by the medical device via the medical device lead.

In some examples, a medical electrical lead includes a lead body and a high voltage electrode positioned on the lead body, the high voltage electrode including a proximal coated portion, a distal coated portion, and an uncoated portion between the proximal coated portion and the distal coated portion, where the proximal coated portion and the distal coated portion are coated with an electrically insulating material configured to prevent conduction of signals having a first range of voltages between the high voltage electrode and patient tissue and allow conduction of signals having a second range of voltages between the high voltage electrode and the patient tissue, where the first range of voltages is lower than the second range of voltages. Additionally, the medical electrical lead includes a set of low voltage electrodes positioned on the lead body, the set of low voltage electrodes including a first low voltage electrode and a second low voltage electrode distal to the first low voltage electrode, where the set of low voltage electrodes and the uncoated portion are positioned on the lead body such that: a first angle is formed between a first line passing through the first low voltage electrode and the second low voltage electrode and a second line passing through the first low voltage electrode and the uncoated portion, and a second angle is formed between the first line and a third line passing through the second low voltage electrode and the uncoated portion.

In some examples, a medical device system includes a medical electrical lead including a lead body and a high voltage electrode positioned on the lead body, the high voltage electrode including a proximal coated portion, a distal coated portion, and an uncoated portion between the proximal coated portion and the distal coated portion, where the proximal coated portion and the distal coated portion are coated with an electrically insulating material configured to prevent conduction of signals having a first range of voltages between the high voltage electrode and patient tissue and allow conduction of signals having a second range of voltages between the high voltage electrode and the patient tissue, where the first range of voltages is lower than the second range of voltages. Additionally, the medical device system includes a set of low voltage electrodes positioned on the lead body, the set of low voltage electrodes including a first low voltage electrode and a second low voltage electrode distal to the first low voltage electrode, where the set of low voltage electrodes and the uncoated portion are positioned on the lead body such that a first angle is formed between a first line passing through the first low voltage electrode and the second low voltage electrode and a second line passing through the first low voltage electrode and the uncoated portion, and a second angle is formed between the first line and a third line passing through the second low voltage electrode and the uncoated portion. Additionally, the medical device system includes a medical device including sensing circuitry electrically coupled to the medical electrical lead, where the sensing circuitry is configured to one or more of: sense a first electrogram according to a first vector including the first low voltage electrode and the second low voltage electrode; sense a second electrogram according to a second vector including the first low voltage electrode and the uncoated portion; or sense a third electrogram according to a third vector including the second low voltage electrode and the uncoated portion.

In some examples, a medical electrical lead includes a lead body including a first curvilinear portion and a second curvilinear portion distal to the first curvilinear portion; a first high voltage electrode positioned on the first curvilinear portion of lead body, where the first high voltage electrode includes at least one coated portion that is coated with an electrically insulating material configured to prevent conduction of signals having a first range of voltages between the first high voltage electrode and patient tissue and allow conduction of signals having a second range of voltages between the first high voltage electrode and the patient tissue, where the first range of voltages is lower than the second range of voltages; a second high voltage electrode positioned on the second curvilinear portion of the lead body; and a set of low voltage electrodes positioned on the lead body, the set of low voltage electrodes including a first low voltage electrode and a second low voltage electrode distal to the first low voltage electrode, where the first low voltage electrode is positioned on the lead body proximal to the first high voltage electrode, and where the second low voltage electrode is placed on the lead body between the first high voltage electrode and the second high voltage electrode.

Like reference characters denote like elements throughout the description and figures.

This disclosure describes techniques for using a medical device lead having an arrangement of electrodes that provides a set of non-parallel electrode vectors. The medical device lead, in some cases, may include a set of electrodes including at least one defibrillation electrode and at least two pace/sense electrodes. The medical device lead may include at least one curvilinear portion such that the set of vectors form angles with one another. In some examples, a defibrillation electrode may be disposed along a curvilinear portion of the medical device lead such that the defibrillation electrode forms an arc, and may include an uncoated portion at or near the peak or apex of the arc configured to conduct relatively lower voltage signals, such as cardiac pacing pulses and sensed electrical signals from the heart, and thus form vectors with the pace/sense electrodes for pacing and sensing. In some examples, the first pace/sense electrode, the second pace/sense electrode, and the uncoated portion of the defibrillation electrode may form a triangle. In some examples, defibrillation electrodes may be referred to herein as "high voltage electrodes. " In some examples, pace/sense electrodes may be referred to herein as "low voltage electrodes.

<FIG> are conceptual diagrams of a medical device system <NUM> implanted within a patient <NUM>. <FIG> is a front view of medical device system <NUM> implanted within patient <NUM>. <FIG> is a side view of medical device system <NUM> implanted within patient <NUM>. <FIG> is a transverse view of medical device system <NUM> implanted within patient <NUM>.

In some examples, medical device system <NUM> is an extravascular implantable cardioverter-defibrillator (EV-ICD) system implanted within patient <NUM>. However, the techniques described herein may be applicable to other implanted and/or external cardiac systems, including cardiac pacemaker systems, cardiac resynchronization therapy defibrillator (CRT-D) systems, cardioverter systems, wearable automated external defibrillator (WAED) systems, or combinations thereof, as well as other stimulation and/or sensing systems, such as neurostimulation systems. In addition, system <NUM> may not be limited to treatment of a human patient. In alternative examples, system <NUM> may be implemented in non-human patients, such as primates, canines, equines, pigs, bovines, ovines, felines, or the like. These other animals may undergo clinical or research therapies that may benefit from the subject matter of this disclosure.

IMD <NUM> is configured to be implanted in a patient, such as patient <NUM>. In some examples, IMD <NUM> is implanted subcutaneously or submuscularly on the left midaxillary of patient <NUM>, such that IMD <NUM> may be positioned on the left side of patient <NUM> above the ribcage. In some other examples, IMD <NUM> may be implanted at other subcutaneous locations on patient <NUM> such as at a pectoral location or abdominal location. IMD <NUM> includes housing <NUM> that may form a hermetic seal that protects components of IMD <NUM>. In some examples, housing <NUM> of IMD <NUM> may be formed of a conductive material, such as titanium, or of a combination of conductive and non-conductive materials, which may function as a housing electrode. IMD <NUM> may also include a connector assembly (also referred to as a connector block or header) that includes electrical feedthroughs through which electrical connections are made between lead <NUM> and electronic components included within the housing. Housing <NUM> may house one or more of processing circuitry, memories, transmitters, receivers, sensors, sensing circuitry, therapy circuitry, power sources and other appropriate components.

In general, medical device systems (e.g., system <NUM>) may include one or more medical devices, leads, external devices, or other components configured to implement the techniques described herein. In the example illustrated in <FIG>, IMD <NUM> is connected to one implantable cardiac lead <NUM>. In other examples, two or more leads may be connected to IMD <NUM>. In some examples, IMD <NUM> may be configured to deliver high-energy anti-tachyarrhythmia (e.g., cardioversion or defibrillation) shocks to heart <NUM> when a ventricular tachyarrhythmia, e.g., ventricular tachycardia (VT) or ventricular fibrillation (VF), is detected. Cardioversion shocks are typically delivered in synchrony with a detected R-wave when fibrillation detection criteria are met. Defibrillation shocks are typically delivered when fibrillation criteria are met, and the R-wave cannot be discerned from signals sensed by IMD <NUM>.

Lead <NUM> includes an elongated lead body having a proximal end that includes a connector <NUM> configured to be connected to IMD <NUM> and a distal portion that includes electrodes 32A, 32B, 36A, and 36B (collectively, "electrodes <NUM>, <NUM>"). Lead <NUM> extends subcutaneously above the ribcage from IMD <NUM> toward a center of the torso of patient <NUM>. At a location near the center of the torso, lead <NUM> bends or turns and extends intrathoracically superior posterior to sternum <NUM>. Lead <NUM> thus may be implanted at least partially in a substernal space, such as at a target site between the ribcage or sternum <NUM> and heart <NUM>. In one such configuration, a proximal portion of lead <NUM> may be configured to extend subcutaneously from IMD <NUM> toward sternum <NUM> and a distal portion of lead <NUM> may be configured to extend superior posterior to sternum <NUM> in the anterior mediastinum <NUM> (<FIG>). Lead <NUM> may include one or more curved sections as discussed herein to configure lead <NUM> to naturally (e.g., in a self-biasing manner) extend in this way upon deployment.

For example, lead <NUM> may extend intrathoracically superior posterior to sternum <NUM> within anterior mediastinum <NUM>. Anterior mediastinum <NUM> may be viewed as being bounded posteriorly by pericardium <NUM>, laterally by pleurae <NUM>, and anteriorly by sternum <NUM>. In some examples, the anterior wall of anterior mediastinum <NUM> may also be formed by the transversus thoracis and one or more costal cartilages. Anterior mediastinum <NUM> includes a quantity of loose connective tissue (such as areolar tissue), some lymph vessels, lymph glands, substernal musculature (e.g., transverse thoracic muscle), and small vessels or vessel branches. In one example, the distal portion of lead <NUM> may be implanted substantially within the loose connective tissue and/or substernal musculature of anterior mediastinum <NUM>. In such examples, the distal portion of lead <NUM> may be physically isolated from pericardium <NUM> of heart <NUM>. A lead implanted substantially within anterior mediastinum <NUM> may be referred to herein as a substernal lead. Electrical therapy, such as anti-arrhythmia pacing, cardioversion or defibrillation, provided by lead <NUM> implanted substantially within anterior mediastinum <NUM> may be referred to herein as substernal electrical therapy, substernal pacing, substernal cardioversion, or substernal defibrillation.

The distal portion of lead <NUM> is described herein as being implanted substantially within anterior mediastinum <NUM>. Thus, some of distal portion of lead <NUM> may extend out of anterior mediastinum <NUM> (e.g., a proximal end of the distal portion), although much of the distal portion may be positioned within anterior mediastinum <NUM>. In other examples, the distal portion of lead <NUM> may be implanted intrathoracically in other non-vascular, extra-pericardial locations, including the gap, tissue, or other anatomical features around the perimeter of and adjacent to, but not attached to, the pericardium <NUM> or other portion of heart <NUM> and not above sternum <NUM> or the ribcage. As such, lead <NUM> may be implanted anywhere within the "substernal space" defined by the undersurface between the sternum and/or ribcage and the body cavity but not including pericardium <NUM> or other portions of heart <NUM>. The substernal space may alternatively be referred to by the terms "retrosternal space" or "mediastinum" or "infrasternal" and may include the anterior mediastinum <NUM>. In other words, the distal portion of lead <NUM> may be implanted in the region around the outer surface of heart <NUM>, but not attached to heart <NUM>. For example, the distal portion of lead <NUM> may be physically isolated from pericardium <NUM>.

Lead <NUM> may include an insulative lead body having a proximal end that includes connector <NUM> configured to be connected to IMD <NUM> and a distal portion that includes one or more electrodes. As shown in <FIG>, the one or more electrodes of lead <NUM> may include electrodes 32A, 32B, 36A, and 36B although in other examples, lead <NUM> may include more or fewer electrodes. Lead <NUM> also includes one or more conductors that form an electrically conductive path within the lead body and interconnect the electrical connector and respective ones of the electrodes. In some cases, lead <NUM> includes a first conductor electrically coupled to defibrillation electrode 32A, a second conductor electrically coupled to defibrillation electrode 32B, a third conductor electrically coupled to pace/sense electrode 36A, and a fourth conductor electrically coupled to pace/sense electrode 36B. In some examples, a proximal end of the first conductor, a proximal end of the second conductor, a proximal end of the third conductor, and a proximal end of the fourth conductor may be coupled to sensing circuitry and/or signal generation circuitry within housing <NUM> of IMD <NUM> via interconnects in the connector <NUM>.

Electrodes 32A, 32B may be defibrillation electrodes (individually or collectively "defibrillation electrode(s) <NUM>"). Although electrodes <NUM> may be referred to herein as "defibrillation electrodes <NUM>," electrodes <NUM> may be configured to deliver other types of anti-tachyarrhythmia shocks, such as cardioversion shocks. In some examples, defibrillation electrodes 32A, 32B may functionally be different sections of a single defibrillation electrode <NUM>, such that both defibrillation electrodes <NUM> are coupled to the same conductor or are otherwise configured to provide the same electrical therapy. Additionally, in some examples, defibrillation electrodes 32A, 32B may each be coupled to different conductors. In such examples, defibrillation electrodes 32A, 32B may be configured to provide electrical therapy together or separately via switches within IMD <NUM>. Although defibrillation electrodes <NUM> are depicted in <FIG> as coil electrodes, it is to be understood that defibrillation electrodes <NUM> may be of other configurations in other examples. Defibrillation electrodes <NUM> may be located on the distal portion of lead <NUM>, where the distal portion of lead <NUM> is the portion of lead <NUM> that is configured to be implanted to extend along sternum <NUM>.

Defibrillation electrodes <NUM> may, in some cases, may include one or more portions that are coated with an electrically insulating material. Defibrillation electrode portions that are coated with at least one electrically insulating material may be referred to herein as "coated portions. " Additionally, in some cases, defibrillation electrodes <NUM> may each include one or more portions that are not coated with an electrically insulating material. Defibrillation electrode portions that are not coated with an electrically insulating material may be referred to herein as "uncoated portions. " In some cases, an entire surface area of a defibrillation electrode of defibrillation electrodes <NUM> may be coated. In some cases, an entire surface area of a defibrillation electrode of defibrillation electrodes <NUM> may be uncoated.

In the example illustrated in <FIG>, defibrillation electrode 32A includes a proximal coated portion 33A, a distal coated portion 33B, and an uncoated portion <NUM> between proximal coated portion 33A and distal coated portion 33B. In some examples, uncoated portion <NUM> is a first uncoated portion, proximal coated portion 33A is a first proximal uncoated portion, and distal coated portion 33B is a first distal uncoated portion. In some such examples, defibrillation electrode 32B includes a second proximal coated portion, a second distal coated portion, and a second uncoated portion between the second proximal coated portion and the second distal coated portion. In other examples, however, one of defibrillation electrodes 32A or 32B may not include any coated portion, but instead be entirely uncoated, or may not include any uncoated portion, and be entirely coated. In another example, neither of the defibrillation electrodes 32A or 32B may include coated and uncoated portions. Instead, one defibrillation electrode <NUM> (e.g., defibrillation electrode 32A) may be entirely coated and the other one of defibrillation electrodes <NUM> (e.g., defibrillation electrode 32B) may be entirely uncoated. For each of defibrillation electrodes <NUM>, a "proximal" coated portion may be more proximal on lead <NUM> (e.g., more proximal to connector <NUM>) than a "distal" coated portion.

In some examples, the electrically insulating material which coats proximal coated portion 33A and distal coated portion 33B (collectively, "coated portions <NUM>") prevents conduction of relatively lower voltage signals between coated portions <NUM> and tissue of patient <NUM>. Additionally, the electrically insulating material may allow conduction of relatively higher voltage signals between coated portions <NUM> and tissue of patient <NUM>. Uncoated portion <NUM> may be configured to both allow conduction of relatively lower voltage signals and allow conduction of relatively higher voltage signals. For example, coated portions <NUM> may be configured to prevent transmission of a pacing pulse, prevent sensing of a cardiac depolarization, and allow transmission of a defibrillation shock. Uncoated portion <NUM>, on the other hand, may be configured to transmit a defibrillation shock, transmit a pacing pulse, sense an electrical signal corresponding to a cardiac depolarization, or any combination thereof. As such, an entire length of a defibrillation electrode such as defibrillation electrode 32A may be configured to conduct a defibrillation shock delivered by signal generation circuitry within housing <NUM>, and a portion (e.g., uncoated portion <NUM>) of defibrillation electrode 32A may be configured to transmit pacing pulses and sense cardiac depolarizations or other relatively lower voltage electrical signals. In this way, uncoated portion <NUM> of defibrillation electrodes <NUM> may perform at least some of the same functionalities as pace/sense electrodes <NUM>. Coated portions <NUM> may, in some cases, prevent or decrease an extent of passive shunting by an electrode <NUM> during sensing of cardiac electrograms by IMD <NUM> via other electrodes of lead <NUM>, e.g., electrodes <NUM>.

The electrically insulating material may, in some examples, extend around the entire circumference of coated portions <NUM> of defibrillation electrodes <NUM>. The electrically insulating material may be any of a number of material such as single or combinations of tantalum pentoxide, titanium oxides, zirconium oxide, vanadium oxide, niobium oxide, doped silicon, silicon dioxide, boron doped diamond, doped glass, ceramic coating or polymer composite or other material that has the property of substantially preventing the transmission or delivery of low voltages while not substantially preventing the transmission or delivery of high voltages. A thickness of the electrically insulating material may vary based on a type of material that defibrillation electrodes <NUM> are made of, the type of electrically insulating material, dimensions of the respective coated portion <NUM>, an expected depth and position of the distal portion of lead <NUM>, e.g., substernal or subcutaneous location. In examples where tantalum pentoxide is the electrically insulating material, the thickness of the electrically insulating material may be within a range from <NUM> micrometers (µm) to less than or equal to <NUM>. However, other thicknesses may be utilized without departing from the scope of this disclosure. In one example, coated portions <NUM> are coated with tantalum pentoxide having a thickness within a range from <NUM> to <NUM> microns. In such an example, the tantalum pentoxide coating significantly blocks current flow up to 90V, thus preventing the sensing of cardiac depolarization events and preventing the transmission of pacing pulses. Additionally, in such an example, electrical signals having voltages higher than 90V (e.g., defibrillation shocks) overcome the electrically insulating property of the tantalum pentoxide coating and may conduct through coated portions <NUM> of defibrillation electrodes <NUM>.

Coated portions <NUM> and uncoated portion <NUM> may vary in size. In some examples, uncoated portion <NUM> may be less than or equal to <NUM>% of the length of defibrillation electrode 32A. Additionally, in some examples, uncoated portion <NUM> may be less than or equal to <NUM>% of the length of defibrillation electrode 32A. Uncoated portion <NUM> may, in some examples, have a surface area that is less than or equal to <NUM> millimeters squared (mm<NUM>). In other instances, uncoated portion <NUM> may have a surface area that is less than or equal to <NUM><NUM>. Uncoated and coated portions may have sizes other than those described above.

Lead <NUM> may be implanted at a target site posterior to sternum <NUM> such that a therapy electrode vector is substantially across a ventricle of heart <NUM>, substantially across an atrium of heart <NUM>, or substantially across both of a ventricle and an atrium of heart <NUM>. In some examples, a therapy vector may be between defibrillation electrodes <NUM> and a housing electrode formed by or on IMD <NUM>, as discussed further below. The therapy electrode vector may, in one example, be viewed as a line that extends from a point on defibrillation electrodes <NUM> (e.g., a center of one of the defibrillation electrodes <NUM>) to a point on a housing electrode of IMD <NUM>. As such, it may be advantageous to increase an amount of area across which defibrillation electrodes <NUM> (and therein the distal portion of lead <NUM>) extends across heart <NUM>. Accordingly, lead <NUM> may be configured to define a curvilinear distal portion as depicted in <FIG>. In some examples, the curvilinear distal portion of lead <NUM> may help improve the efficacy and/or efficiency of pacing, sensing, and/or defibrillation to heart <NUM> by IMD <NUM>, in addition to the techniques for controlling the delivery of cardiac therapy described herein.

The defibrillation electrodes 32A, 32B may be electrically connected to one or more conductors, which may be disposed in a body wall of the lead <NUM> and/or may be disposed in one or more insulated lumens (not shown) defined by the lead <NUM>. In some examples, each of the defibrillation electrodes 32A, 32B is connected to a common conductor such that IMD <NUM> may apply a voltage simultaneously to all the defibrillation electrodes 32A, 32B to deliver a defibrillation shock to a patient's heart (e.g., heart <NUM>). In some examples, the defibrillation electrodes 32A, 32B may be attached to separate conductors such that IMD <NUM> may apply a voltage to each defibrillation electrode <NUM> independent of the other defibrillation electrodes <NUM>. In this case, IMD <NUM> or lead <NUM> may include one or more switches or other mechanisms to electrically connect the defibrillation electrode segments to the same or different voltage sources.

Housing <NUM> may be charged with or function as a polarity different than the polarity of the one or more defibrillation electrodes <NUM> and/or pace/sense electrodes <NUM> such that electrical energy may be delivered between the housing <NUM> and the defibrillation electrodes <NUM> and/or pace/sense electrodes <NUM> to heart <NUM>. Each defibrillation electrode <NUM> may have the same polarity as every other defibrillation electrode <NUM> when a voltage is applied to it such that a defibrillation shock may be delivered from each of defibrillation electrodes <NUM> to housing <NUM>. In examples in which defibrillation electrodes <NUM> are electrically connected to a common conductor within lead body <NUM>, this is the only configuration of defibrillation electrodes <NUM>. However, in other examples, defibrillation electrodes <NUM> may be coupled to separate conductors within lead body <NUM> and may therefore each have different polarities such that electrical energy may flow between defibrillation electrodes <NUM>, or between one or more of defibrillation electrodes <NUM> and an electrode on housing <NUM>.

Pace/sense electrodes 36A and 36B (collectively, "pace/sense electrodes <NUM>") may be located on the distal portion of lead <NUM>. Electrodes <NUM> may be referred to herein as pace/sense electrodes as they generally are configured for use in delivery of pacing pulses and/or sensing of cardiac electrical signals. In some instances, electrodes <NUM> may provide only pacing functionality, only sensing functionality, or both pacing functionality and sensing functionality. Pace/sense electrode 36A and pace/sense electrode 36B may be separated by defibrillation electrode 32A. In examples in which lead <NUM> includes more or fewer electrodes <NUM>, <NUM>, such electrodes may be positioned at other locations on lead <NUM>. In some examples, IMD <NUM> may include one or more electrodes <NUM>, <NUM> on another lead (not shown). Other lead configurations may be used, such as various electrode arrangements. For example, one or more pace/sense electrodes <NUM> may be placed between two defibrillation electrodes <NUM>, such as described above. In an example, multiple pace/sense electrodes <NUM> may be placed between two defibrillation electrodes <NUM>. In an example, two defibrillation electrodes <NUM> may be adjacent (e.g., such that the two defibrillation electrodes <NUM> are not separated by any pace/sense electrodes <NUM> between the two defibrillation electrodes <NUM>). Other arrangements may additionally or alternatively be used.

Lead <NUM> may define different sizes and shapes as may be appropriate for different purposes (e.g., for different patients or for different therapies). As discussed above, in some examples, the distal portion of lead <NUM> may have a curvilinear portion that includes one or more curved sections. As shown in the example of <FIG>, the distal portion of lead <NUM> is a curvilinear shape that includes two "C" shaped curves, which together may resemble the Greek letter epsilon, "ε. " Defibrillation electrodes <NUM> are each carried by one of the two respective C-shaped curved portions of the lead body distal portion. The two C-shaped curves extend or curve in the same direction away from a central axis of the lead body. In some examples, pace/sense electrodes <NUM> may be substantially aligned with the central axis of the distal portion of lead <NUM>. In such examples, mid-points of defibrillation electrodes <NUM> are laterally offset from pace/sense electrodes <NUM>. In some examples, the central axis of the distal portion of lead <NUM> represents a line that passes through each pace/sense electrode of pace/sense electrodes <NUM>. Other examples of extra-cardiovascular leads including one or more defibrillation electrodes <NUM> and one or more pace/sense electrodes <NUM> carried by the curvilinear (e.g., curving, serpentine, undulating or zig-zagging) distal portion of lead <NUM> also may be implemented using the techniques described herein. In some examples, the distal portion of lead <NUM> may be straight (e.g., straight or nearly straight).

In some examples, the electrode arrangement on lead <NUM> may correspond to a geometry of lead <NUM>. For example, pace/sense electrodes <NUM> may be positioned on relative peaks of a curved lead shape, while defibrillation electrodes <NUM> may be positioned on relative valleys of the curved lead shape. The relative valleys may, in some cases, represent curvilinear portions of lead <NUM>. Additionally, uncoated portion <NUM> may be positioned at the "bottoms" of the respective curvilinear portions or valleys. In other examples, the distal portion of lead <NUM> may include branches, biased portions expanding away from a central shaft, or other shapes (e.g., with one or more of electrodes <NUM>, <NUM> disposed on the branches, shaft, or biased portions) that may provide appropriate monitoring information or therapy. Deploying lead <NUM> such that electrodes <NUM>, <NUM> are thusly at these depicted peaks and valleys of the curvilinear shape of the distal portion of lead <NUM> may therein increase an efficacy of system <NUM>. For example, electrodes <NUM>, <NUM> may provide access to better sensing or therapy vectors when lead <NUM> is deployed into the curvilinear shape, in addition to the techniques for controlling the delivery of cardiac therapy described herein.

Orienting the curvilinear-shaped lead such that pace/sense electrodes <NUM> are closer to heart <NUM> may provide better electrical sensing of the cardiac signal and/or lower pacing capture thresholds than if pace/sense electrodes <NUM> were oriented further from heart <NUM>. The curvilinear or other shape of the distal portion of lead <NUM> may have increased fixation to patient <NUM> as a result of the shape providing resistance against adjacent tissue when an axial force is applied. Another advantage of a shaped distal portion is that pace/sense electrodes <NUM> may have access to greater surface area over a shorter length of heart <NUM> relative to a lead having a straighter distal portion.

In some examples, the elongated lead body of lead <NUM> may have a diameter within a range from <NUM> French (Fr) to <NUM> Fr, although lead bodies having diameters less than <NUM> Fr and more than <NUM> Fr may also be utilized. In another example, the distal portion and/or other portions of the lead body may have a flat, ribbon or paddle shape. In such examples, the width across the flat portion of the flat, ribbon or paddle shape may be between <NUM> and <NUM>. Other lead body designs may be used without departing from the scope of this disclosure. The lead body of lead <NUM> may be formed from a non-conductive material, including silicone, polyurethane, fluoropolymers, mixtures thereof, and other appropriate materials, and shaped to form one or more lumens within which the one or more conductors extend. However, the techniques are not limited to such constructions.

In some examples, defibrillation electrodes <NUM> may have a length within a range from <NUM> centimeters (cm) to <NUM>. In some examples, defibrillation electrodes <NUM> may be a flat ribbon electrode, paddle electrode, braided or woven electrode, mesh electrode, segmented electrode, directional electrode, patch electrode or other type of electrode besides an elongated coil electrode.

Pace/sense electrodes <NUM> may include ring electrodes, short coil electrodes, hemispherical electrodes, segmented electrodes, directional electrodes, or the like. In some examples, pace/sense electrodes <NUM> may have substantially the same outer diameter as the lead body. In one example, pace/sense electrodes <NUM> may have surface areas within a range from <NUM> millimeter squared (mm<NUM>) to <NUM><NUM>. Pace/sense electrodes <NUM> may, in some examples, have relatively the same surface area or different surface areas. Depending on the configuration of lead <NUM>, pace/sense electrodes <NUM> may be spaced apart by the length of defibrillation electrodes <NUM>, plus some insulated length on each side of defibrillation electrode <NUM>, e.g., within a range from <NUM> to <NUM>. In other examples, such as when a pair of pace/sense electrodes <NUM> are not separated by a defibrillation electrode <NUM>, the electrode spacing may be smaller, e.g., up to <NUM>. The example dimensions provided above are exemplary in nature and should not be considered limiting of the examples described herein.

In some examples, IMD <NUM> may include one or more housing electrodes (not shown) positioned on housing <NUM> of IMD <NUM>. Such housing electrodes may be formed integrally with an outer surface of hermetically-sealed housing <NUM> of IMD <NUM>, or otherwise may be coupled to housing <NUM>. In some examples, a housing electrode may be defined by an uninsulated portion of an outward facing portion of housing <NUM> of IMD <NUM>. In some examples, housing <NUM> may define one or more additional housing electrodes, which may be defined by corresponding divisions between insulated and uninsulated portions of housing <NUM>. In still other examples, substantially all of housing <NUM> may be uninsulated, such that substantially all of housing <NUM> defines a housing electrode.

In general, system <NUM> may sense electrical signals, such as via one or more vectors that include combinations of uncoated portion <NUM> of defibrillation electrodes <NUM>, pace/sense electrodes <NUM>, and/or a housing electrode of IMD <NUM>. The sensed electrical intrinsic signals may include electrical signals generated by cardiac muscle and indicative of depolarizations and repolarizations of heart <NUM> at various times during the cardiac cycle. IMD <NUM> may be configured to analyze the electrical signals sensed by the one or more vectors to detect an arrhythmia, such as ventricular tachycardia (VT), ventricular fibrillation (VF), atrial tachycardia (AT), atrial fibrillation (AF), or any combination thereof. In response to detecting the arrhythmia , in some cases, IMD <NUM> may begin to charge a storage element, such as a bank of one or more capacitors. When the capacitors are charged, IMD <NUM> may deliver substernal electrical therapy, e.g., anti-tachycardia pacing (ATP), cardioversion or defibrillation shocks, bradycardia pacing, asystole pacing, and/or post-shock pacing. In some examples, IMD <NUM> may generate and deliver bradycardia pacing in addition to ATP, cardioversion or defibrillation shocks, and/or post-shock pacing.

In some examples, system <NUM> may include external device <NUM>. External device <NUM> may be a computing device that is configured for use in a home, ambulatory, clinic, or hospital setting to communicate with IMD <NUM> via wireless telemetry. Examples of communication techniques used by IMD <NUM> and external device <NUM> include radiofrequency (RF) telemetry, which may include an RF link established via Bluetooth®, wireless local networks, or medical implant communication service (MICS). The communication may include one-way communication in which one device is configured to transmit communication messages and the other device is configured to receive those messages. Alternatively, or additionally, the communication may include two-way communication in which each device is configured to transmit and receive communication messages.

External device <NUM> may include communication circuitry configured to communicate with one or more devices of system <NUM> (e.g., IMD <NUM>) in accordance with the techniques described above. For example, external device <NUM> may be used to program commands or operating parameters of IMD <NUM> for controlling functioning of IMD <NUM> when external device <NUM> is configured as a programmer for IMD <NUM>. External device <NUM> may be used to communicate with IMD <NUM> to retrieve data such as operational data, physiological data accumulated in IMD memory, or the like. As such, external device <NUM> may function as a programmer for IMD <NUM>, an external monitor for IMD <NUM>, or a consumer device such as a smartphone. External device <NUM> may be coupled to a remote patient monitoring system, such as CARELINK® Network, available from Medtronic plc, of Dublin, Ireland. In other examples, a clinician may use external device <NUM> to program or update therapy parameters that define cardiac therapy, and/or program or update modifications to the cardiac therapy parameters, sensing parameters, and/or electrode vectors associated with the plurality of heart position states, or perform other activities with respect to IMD <NUM>. The clinicians may be a physician, technician, surgeon, electrophysiologist, or other healthcare professional. In some examples, the user may be patient <NUM>.

Although described herein in the context of example IMD <NUM>, the techniques for controlling the delivery of cardiac therapy described herein may be implemented with other types of IMD configured to deliver cardiac therapy. In some examples, the techniques described herein may be implemented with an external defibrillation device, or other devices or systems configured to deliver cardiac therapy. Although in the examples illustrated in <FIG>, lead <NUM> may be implanted substernally, in some examples, lead <NUM> may be implanted at other extracardiovascular locations including subcutaneously or submuscularly anterior to the sternum and/or the rib cage.

<FIG> is a functional block diagram illustrating an example configuration of IMD <NUM>, in accordance with one or more techniques described herein. As shown in <FIG>, IMD <NUM> includes processing circuitry <NUM>, sensing circuitry <NUM>, signal generation circuitry <NUM>, sensors <NUM>, communication circuitry <NUM>, and storage device <NUM>. Storage device <NUM> may store therapy and sensing parameters <NUM> and collected data <NUM>. In addition, IMD <NUM> is electrically coupled to one or more electrodes <NUM>, 32A, 32B, 36A, and 36B.

Processing circuitry <NUM> may include fixed function circuitry and/or programmable processing circuitry. Processing circuitry <NUM> may include any one or more of a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or equivalent discrete or analog logic circuitry. In some examples, processing circuitry <NUM> may include multiple components, such as any combination of one or more microprocessors, one or more controllers, one or more DSPs, one or more ASICs, or one or more FPGAs, as well as other discrete or integrated logic circuitry. The functions attributed to processing circuitry <NUM> herein may be embodied as software, firmware, hardware or any combination thereof.

Sensing circuitry <NUM> monitors electrical cardiac signals from any combination of electrodes <NUM>, 32A, 32B, 36A, and 36B, the various combinations of electrodes <NUM>, 32A, 32B, 36A, and 36B forming a set of electrode vectors. In some examples, sensing circuitry <NUM> may include one or more amplifiers, filters, and analog-to-digital converters. For example, sensing circuitry <NUM> may include one or more detection channels, each of which may include an amplifier. The detection channels may be used to sense cardiac signals, such as a cardiac EGM. The channels may detect cardiac EGM signals from a particular combination (e.g., a vector) of electrodes <NUM>, 32A, 32B, 36A, and 36B. Some detection channels may detect events, such as R-waves, P-waves, and T-waves and provide indications of the occurrences of such events to processing circuitry <NUM>. One or more other detection channels may provide signals to an analog-to-digital converter (ADC), for conversion into a digital signal for processing, analysis, storage, or output by processing circuitry <NUM>.

Each detection channel of sensing circuitry <NUM> may include a filter configured to pass a custom range of frequency values. For example, sensing circuitry <NUM> may include one or more narrow band channels, each of which may include a narrow band filtered sense-amplifier. Additionally, or alternatively, sensing circuitry <NUM> may include one or more wide band channels, each of which include an amplifier with a relatively wider pass band than the narrow band channels. Signals sensed by the narrow band channels and the wide band channels of sensing circuitry <NUM> may be converted to multi-bit digital signals by an ADC provided by, for example, sensing circuitry <NUM> or processing circuitry <NUM>. In some examples, processing circuitry <NUM> analyzes the digitized version of signals from sensing circuitry <NUM>. In other examples, processing circuitry <NUM> stores the digitized versions of the signals in storage device <NUM> (e.g., as collected data <NUM>), outputs the digitized versions of the signals via communication circuitry <NUM>, or any combination thereof. Thresholds, filter parameter values, blanking intervals, and other parameter values for controlling the sensing and processing of cardiac signals by sensing circuitry <NUM> and processing circuitry <NUM> may be stored as therapy and sensing parameters <NUM> in storage device <NUM>.

Generally, processing circuitry <NUM> controls signal generation circuitry <NUM> to deliver therapy to heart <NUM> of patient <NUM> according to selected values of therapy and sensing parameters <NUM>, which may be stored storage device <NUM>. As an example, processing circuitry <NUM> may control signal generation circuitry <NUM> to deliver electrical pulses with the amplitudes, pulse widths, frequency, and/or electrode polarities (which define a therapy vector) specified by the therapy and sensing parameters <NUM>. Therapy and sensing parameters <NUM> stored in storage device <NUM> may include thresholds or other conditions, which may be compared to parameters of the EGM, and based on which processing circuitry <NUM> controls signal generation circuitry <NUM> to deliver therapy, such as cardiac rates, intervals, and/or EGM morphology parameters.

Signal generation circuitry <NUM> is configured to generate and deliver electrical therapy to patient <NUM>. As shown in <FIG>, signal generation circuitry <NUM> is electrically coupled to electrodes <NUM>, 32A, 32B, 36A, and 36B, e.g., via conductors within the respective lead <NUM> and, in the case of electrodes disposed on housing <NUM> of IMD <NUM>, within housing <NUM>. For example, signal generation circuitry <NUM> may deliver pacing, defibrillation or cardioversion pulses to heart <NUM> via at least two of electrodes <NUM>, 32A, 32B, 36A, and 36B. In some examples, signal generation circuitry <NUM> delivers therapy in the form of signals other than pulses such as sine waves, square waves, or other substantially continuous time signals. In some examples, signal generation circuitry <NUM> may include one or more capacitors, charge pumps, current sources, or other signal generation circuitry.

Sensing circuitry <NUM> and signal generation circuitry <NUM> may be selectively coupled to electrodes <NUM>, 32A, 32B, 36A, and 36B, e.g., via switching circuitry (not illustrated in <FIG>) as controlled by processing circuitry <NUM>. The switching circuitry may include one or more transistors or other circuitry for selectively coupling electrodes <NUM>, 32A, 32B, 36A, and 36B to other circuitry of IMD <NUM>. Sensing circuitry <NUM> may monitor signals from electrodes <NUM>, 32A, 32B, 36A, and 36B in order to monitor electrical activity of heart (e.g., to detect depolarizations for heart rate determination and/or to produce a cardiac electrogram for morphological or other analyses).

Sensor(s) <NUM> may include one or more accelerometers. Sensors <NUM> may additionally or alternatively include other sensors such as gyrometers, magnetometers, barometers, acoustic sensors, pressure sensors, flow sensors, oxygen (O<NUM>) saturation sensors. Information obtained from sensor(s) <NUM> may be used to determine activity level, posture, blood pressure, blood flow, blood oxygen level, or respiratory rate, as examples. In some examples, this information may be used by processing circuitry <NUM> to aid in the classification of an abnormal heart rhythm. In some examples, at least some of sensor(s) <NUM> may be located outside of the housing <NUM> of IMD <NUM>. Sensor(s) <NUM> may be located on a lead (e.g., lead <NUM>) that is coupled to IMD <NUM> or may be implemented in a remote sensor that wirelessly communicates with IMD <NUM> via communication circuitry <NUM>. In any case, sensor(s) <NUM> are electrically or wirelessly coupled to circuitry contained within housing <NUM> of IMD <NUM>.

Communication circuitry <NUM> may include any suitable hardware, firmware, software or any combination thereof for communicating with another device, such as external device <NUM>. Under the control of processing circuitry <NUM>, communication circuitry <NUM> may receive downlink telemetry from, as well as send uplink telemetry to, external device <NUM> or another device. In some examples, communication circuitry <NUM> exchanges information with the aid of an internal or external antenna (not illustrated in <FIG>). In addition, processing circuitry <NUM> may communicate with a networked computing device via an external device (e.g., external device <NUM>) and a computer network, such as the Medtronic CareLink® Network developed by Medtronic, plc, of Dublin, Ireland. Communication circuitry <NUM> may include any combination of a Bluetooth® radio, an electronic oscillator, frequency modulation circuitry, frequency demodulation circuitry, amplifier circuitry, and power switches such as a metal-oxide-semiconductor field-effect transistors (MOSFET), a bipolar junction transistor (BJT), an insulated-gate bipolar transistor (IGBT), a junction field effect transistor (JFET), or another element that uses voltage for its control.

Storage device <NUM> may be configured to store information within IMD <NUM> during operation. Storage device <NUM> may include a computer-readable storage medium or computer-readable storage device. In some examples, storage device <NUM> includes one or more of a short-term memory or a long-term memory. Storage device <NUM> may include, for example, random access memories (RAM), dynamic random access memories (DRAM), static random access memories (SRAM), magnetic discs, optical discs, flash memories, or forms of electrically programmable memories (EPROM) or electrically erasable and programmable memories (EEPROM). In some examples, storage device <NUM> is used to store data indicative of instructions for execution by processing circuitry <NUM>.

In some examples, IMD <NUM> may be configured to sense, using sensing circuitry <NUM>, cardiac signals according to a selected one or more of set of vectors. Processing circuitry <NUM> may control sensing circuitry <NUM> to obtain, for each vector of the set of vectors, data corresponding to a difference in electric potential between nodes of the respective vector. Nodes of each vector may correspond to a pair of electrodes <NUM>, 32A, 32B, 36A, and 36B, or more than two electrodes <NUM>, 32A, 32B, 36A, and 36B if two of the electrodes are connected as a common node. Each of electrodes <NUM>, 32A, 32B, 36A, and 36B, including electrodes <NUM>, <NUM> may be coupled to sensing circuitry <NUM> via a respective electrical conductor. In this way, IMD <NUM> may be able to obtain a signal (e.g., a signal indicative of an electric potential) using each electrode of electrodes <NUM>, 32A, 32B, 36A, and 36B. A vector may be defined by a set of parameters including a combination of two or more electrodes, a spatial arrangement of the two or more electrodes, and a polarity of each electrode of the two or more electrodes.

For example, processing circuitry <NUM> may be configured to control sensing circuitry <NUM> to obtain a first electrogram via a first vector including first pace/sense electrode 36A and second pace/sense electrode 36B. In some examples, the first electrogram is proportional to a difference in electric potential between first pace/sense electrode 36A and second pace/sense electrode 36B. Additionally, processing circuitry <NUM> may be configured to control sensing circuitry <NUM> to obtain a second electrogram via a second vector including first pace/sense electrode 36A and uncoated portion <NUM> of first defibrillation electrode 32A. In some examples, the second electrogram is proportional to a difference in electric potential between first pace/sense electrode 36A and uncoated portion <NUM>. The second vector may form a first angle with the first vector. In other words, a line which passes through first pace/sense electrode 36A and second pace/sense electrode 36B may form the first angle with a line that passes through first pace/sense electrode 36A and uncoated portion <NUM>. The first angle is within a range from thirty degrees to sixty degrees.

Since cardiac depolarizations are directional in nature and follow a three-dimensional path through heart <NUM> of patient <NUM>, it may be beneficial for the first vector to form an angle with the second vector such IMD <NUM> may be able obtain different angular perspectives of directional cardiac depolarizations, e.g., allowing selection of one of the vectors providing a preferred signal characteristics.

Additionally, processing circuitry <NUM> may control sensing circuitry <NUM> to obtain a third electrogram via a third vector including second pace/sense electrode 36B and uncoated portion <NUM> of first defibrillation electrode 32A. In some examples, the third electrogram is proportional to a difference in electric potential between second pace/sense electrode 36B and uncoated portion <NUM>. The third vector may form a second angle with the first vector. In other words, a line which passes through first pace/sense electrode 36A and second pace/sense electrode 36B may form the second angle with a line that passes through second pace/sense electrode 36B and uncoated portion <NUM>. The second angle is within a range from thirty degrees to sixty degrees. It may be beneficial for the third vector to form an angle with the first vector such that IMD <NUM> may obtain another angular perspective of the directional cardiac depolarizations in addition to the perspectives provided by the first vector and the second vector. Additionally, the second vector and the third vector may form an angle (e.g., within a range from <NUM> to <NUM> degrees) such that the first vector, the second vector, and the third vector form a triangle between first pace/sense electrode 36A, second pace/sense electrode 36B, and uncoated portion <NUM>.

First pace/sense electrode 36A, second pace/sense electrode 36B, and uncoated portion <NUM> may, in some cases, be proximate to a ventricle of heart <NUM>. In some cases, processing circuitry <NUM> may store one or more of the first electrogram, the second electrogram, and the third electrogram in storage device <NUM> as a part of collected data <NUM>, where the first electrogram, the second electrogram, and the third electrogram are different.

In addition to being configured to selectively determine data corresponding to the first vector, the second vector, and/or the third vector which are located proximate to the ventricles of heart <NUM>, processing circuitry <NUM> may be configured to direct sensing circuitry <NUM> to collect data via electrodes that are proximate to the atria of heart <NUM>. For example, processing circuitry <NUM> may control sensing circuitry <NUM> to obtain a fourth electrogram vie a fourth vector including second pace/sense electrode 36B and a third pace/sense electrode (not illustrated in <FIG> and <FIG>) distal to defibrillation electrode 32B. In some examples, the fourth electrogram is proportional to a difference in electric potential between second pace/sense electrode 36B and the third pace/sense electrode. Additionally, processing circuitry <NUM> may control sensing circuitry <NUM> to obtain a fifth electrogram via a fifth vector including second pace/sense electrode 36B and a second uncoated portion (not illustrated) located on second defibrillation electrode 32B. In some examples, the fifth electrogram is proportional to a difference in electric potential between second pace/sense electrode 36B and the second uncoated portion. The fifth vector may form a third angle with the fourth vector. In other words, a line which passes through second pace/sense electrode 36B and the third pace/sense electrode may form the third angle with a line that passes through second pace/sense electrode 36B and the second uncoated portion. In some examples, the third angle is within a range from thirty degrees to sixty degrees. However, the third angle is not meant to be limited to such a range. In some cases, the third angle may be less than thirty degrees or greater than sixty degrees. Since cardiac depolarizations are directional in nature and follow a three-dimensional path through heart <NUM> of patient <NUM>, it may be beneficial for the fifth vector to form an angle with the fourth vector such that IMD <NUM> obtains different angular perspectives of directional cardiac depolarizations according to the fourth vector and the fifth vector.

Additionally, processing circuitry <NUM> may control sensing circuitry <NUM> to obtain a sixth electrogram via a sixth vector including the third pace/sense electrode and the second uncoated portion of second defibrillation electrode 32B. In some examples, the sixth electrogram is proportional to a difference in electric potential between the third pace/sense electrode and the second uncoated portion. The sixth vector may form a fourth angle with the fourth vector. In other words, a line which passes through second pace/sense electrode 36B and the third pace/sense electrode may form the fourth angle with a line that passes through the third pace/sense electrode and the second uncoated portion. In some examples, the fourth angle is within a range from thirty degrees to sixty degrees. However, the fourth angle is not meant to be limited to such a range. In some cases, the fourth angle may be less than thirty degrees or greater than sixty degrees. It may be beneficial for the sixth vector to form an angle with the fourth vector such that IMD <NUM> may obtain another angular perspective of the directional cardiac depolarizations in addition to the perspectives provided by the fourth vector and the fifth vector. Additionally, the fifth vector and the sixth vector may form an angle (e.g., within a range from <NUM> to <NUM> degrees) such that the fourth vector, the fifth vector, and the sixth vector form a triangle between second pace/sense electrode 36B, the third pace/sense electrode, and the second uncoated portion.

Second pace/sense electrode 36B, the third pace/sense electrode, and the second uncoated portion may, in some cases, be proximate to atria of heart <NUM>. In some cases, processing circuitry <NUM> may be configured to store the fourth electrogram, the fifth electrogram, and the sixth electrogram in storage device <NUM> as a part of collected data <NUM>, where the fourth electrogram, the fifth electrogram, and the sixth electrogram are different.

Although the set of vectors including the first vector, the second vector, the third vector, the fourth vector, the fifth vector, and the sixth vector are described herein with respect to sensing cardiac depolarizations, IMD <NUM> may also deliver electric stimulation (e.g., pacing pulses) according to the set of vectors. For example, processing circuitry <NUM> may control signal generation circuitry <NUM> to deliver electrical stimulation according to any one or more of the first vector, the second vector, and the third vector in order to deliver electrical stimulation to ventricles of heart <NUM>. Additionally, processing circuitry <NUM> may control signal generation circuitry <NUM> to deliver electric stimulation according to any one or more of the fourth vector, the fifth vector, and the sixth vector in order to deliver electric stimulation to the atria of heart <NUM>. Since each of the set of vectors offer different perspectives with respect to heart <NUM>, it may be beneficial for IMD <NUM> to selectively deliver electric stimulation according to a selected one or more of the set of vectors.

Power source <NUM> is configured to deliver operating power to the components of IMD <NUM>. Power source <NUM> may include a battery and a power generation circuit to produce the operating power. In some examples, the battery is rechargeable to allow extended operation. In some examples, recharging is accomplished through proximal inductive interaction between an external charger and an inductive charging coil within IMD <NUM>. Power source <NUM> may include any one or more of a plurality of different battery types, such as nickel cadmium batteries and lithium ion batteries.

Although six vectors are described with respect to <FIG>, processing circuitry <NUM> may be configured to determine data corresponding to other vectors. Such other vectors may represent differences in measured parameters between any two or more of electrodes <NUM>, 32A, 32B, 36A, and 36B. For example, although the six vectors are described herein as including two electrodes, one or more techniques of this disclosure may be implemented such that a vector may include three or more electrodes, where at least two of the three or more electrodes are connected as a common node. In this way, a vector may include two nodes, each node including one or more electrodes. Additionally, each of the six vectors described with respect to <FIG> may correspond to an opposite polarity vector. For example, IMD <NUM> may change the polarity of any of the six vectors to obtain data corresponding to the respective opposite polarity vector.

A clinician or another user may retrieve data from IMD <NUM> using external device <NUM>, or by using another local or networked computing device (e.g., a remote computer located with the clinician) configured to communicate with processing circuitry <NUM> via communication circuitry <NUM>. For example, a clinician may retrieve collected data <NUM> for analysis using external device <NUM>. In some examples, the clinician may also program parameters of IMD <NUM> (e.g., therapy and sensing parameters <NUM> using external device <NUM> or another local or networked computing device.

Although processing circuitry <NUM> of IMD <NUM> is described above as being configured to control sensing circuitry <NUM> to sense cardiac electrogram signals and signal generation circuitry <NUM> to deliver cardiac pacing according to a selected one or more vectors from a set of vectors, any steps described herein as being carried out by processing circuitry <NUM> of IMD <NUM> may carried out by processing circuitry of one or more other devices. For example, processing circuitry of external device <NUM>, a remote computer, or any other suitable implantable or external device or server, may be configured to carry out one or more of the steps of the techniques described herein, such as via communication circuitry <NUM> of IMD <NUM>.

<FIG> is a block diagram illustrating an example configuration of components of external device <NUM>, in accordance with one or more techniques described herein. In the example of <FIG>, external device <NUM> includes processing circuitry <NUM>, communication circuitry <NUM>, storage device <NUM>, user interface <NUM>, and power source <NUM>. Storage device <NUM> is configured to store operational parameters <NUM> and retrieved data <NUM>.

Processing circuitry <NUM>, in one example, may include one or more processors that are configured to implement functionality and/or process instructions for execution within external device <NUM>. For example, processing circuitry <NUM> may be capable of processing instructions stored in storage device <NUM>. Processing circuitry <NUM> may include, for example, microprocessors, DSPs, ASICs, FPGAs, or equivalent discrete or integrated logic circuitry, or a combination of any of the foregoing devices or circuitry. Accordingly, processing circuitry <NUM> may include any suitable structure, whether in hardware, software, firmware, or any combination thereof, to perform the functions ascribed herein to processing circuitry <NUM>.

Communication circuitry <NUM> may include any suitable hardware, firmware, software or any combination thereof for communicating with another device, such as IMD <NUM>. Under the control of processing circuitry <NUM>, communication circuitry <NUM> may receive downlink telemetry from, as well as send uplink telemetry to, IMD <NUM> or another device. In some examples, communication circuitry <NUM> includes a first set of communication circuitry configured for transmitting and receiving signals according to a communication protocol developed by the manufacturer of IMD <NUM> or a third-party developer. In some such examples, communication circuitry <NUM> further includes a second set of communication circuitry which defines a Bluetooth® radio configured for transmitting and receiving signals according to Bluetooth® communication protocols. However, communication circuitry <NUM> does not necessarily include separate sets of circuitry corresponding to different communication protocols. In some examples, communication circuitry <NUM> includes a single set of circuitry configured for transmitting and receiving signals according to a plurality of communication protocols.

In some examples, communication circuitry <NUM> includes any combination of a Bluetooth® radio, an electronic oscillator, frequency modulation circuitry, frequency demodulation circuitry, amplifier circuitry, and power switches such as a MOSFET, a BJT, an IGBT, a JFET, or another element that uses voltage for its control.

Storage device <NUM> may be configured to store information within external device <NUM> during operation. Storage device <NUM> may include a computer-readable storage medium or computer-readable storage device. In some examples, storage device <NUM> includes one or more of a short-term memory or a long-term memory. Storage device <NUM> may include, for example, RAM, DRAM, SRAM, magnetic discs, optical discs, flash memories, or forms of EPROM or EEPROM. In some examples, storage device <NUM> is used to store data indicative of instructions for execution by processing circuitry <NUM>. Storage device <NUM> may be used by software or applications running on external device <NUM> to temporarily store information during program execution.

Data exchanged between external device <NUM> and IMD <NUM> may include any of operational parameters <NUM> stored in storage device <NUM>. External device <NUM> may transmit data including computer readable instructions which, when implemented by IMD <NUM>, may control IMD <NUM> to change one or more operational parameters according to operational parameters <NUM> and/or export collected data. For example, processing circuitry <NUM> may transmit an instruction to IMD <NUM> which requests IMD <NUM> to export collected data (e.g., a portion of collected data <NUM>) to external device <NUM>. In turn, external device <NUM> may receive the collected data from IMD <NUM> and store the collected data in storage device <NUM> (e.g., as retrieved data <NUM>). Additionally, or alternatively, processing circuitry <NUM> may export instructions to IMD <NUM> requesting IMD <NUM> to update electrode vectors for therapy or sensing according to operational parameters <NUM>. For example, processing circuitry <NUM> may export instructions to IMD <NUM> requesting IMD <NUM> to update which vectors (e.g., the first vector, the second vector, the third vector, the fourth vector, the fifth vector, the sixth vector, or another vector) are used to monitor the electrical signals of heart <NUM>.

A user, such as a clinician or patient <NUM>, may interact with external device <NUM> through user interface <NUM>. User interface <NUM> includes a display (not shown), such as an LCD or LED display or other type of screen, with which processing circuitry <NUM> may present information related to IMD <NUM> (e.g., EGM signals obtained using one of the set of vectors). In addition, user interface <NUM> may include an input mechanism to receive input from the user. The input mechanisms may include, for example, any one or more of buttons, a keypad (e.g., an alphanumeric keypad), a peripheral pointing device, a touch screen, or another input mechanism that allows the user to navigate through user interfaces presented by processing circuitry <NUM> of external device <NUM> and provide input. In other examples, user interface <NUM> also includes audio circuitry for providing audible notifications, instructions or other sounds to patient <NUM>, receiving voice commands from patient <NUM>, or both. Storage device <NUM> may include instructions for operating user interface <NUM> and for managing power source <NUM>.

Power source <NUM> is configured to deliver operating power to the components of external device <NUM>. Power source <NUM> may include a battery and a power generation circuit to produce the operating power. In some examples, the battery is rechargeable to allow extended operation. Recharging may be accomplished by electrically coupling power source <NUM> to a cradle or plug that is connected to an alternating current (AC) outlet. In addition, recharging may be accomplished through proximal inductive interaction between an external charger and an inductive charging coil within external device <NUM>. In other examples, traditional batteries (e.g., nickel cadmium or lithium ion batteries) may be used. In addition, external device <NUM> may be directly coupled to an alternating current outlet to operate.

<FIG> is a front view of a distal portion of medical lead <NUM>, in accordance with one or more techniques described herein. In the illustrated example, lead <NUM> includes first defibrillation electrode 32A, second defibrillation electrode 32B, first pace/sense electrode 36A, and second pace/sense electrode 36B. First defibrillation electrode 32A includes proximal coated portion 33A, distal coated portion 33B, and uncoated portion <NUM> between proximal coated portion 33A and distal coated portion 33B. In some examples, proximal coated portion 33A is a first proximal coated portion, distal coated portion 33B is a first distal coated portion, and uncoated portion <NUM> is a first uncoated portion. In some examples not illustrated in <FIG>, second defibrillation electrode 32B includes a second proximal coated portion, a second distal coated portion, and a second uncoated portion between the second proximal coated portion and the second distal coated portion.

Defibrillation electrodes <NUM>, in some examples, are coil electrodes formed by a conductor. For example, first defibrillation electrode 32A and second defibrillation electrode 32B may represent coil electrodes disposed in-line with a wall of lead <NUM>, around an exterior of the wall of lead <NUM>, or within the wall of lead <NUM>. Additionally, in some examples, defibrillation electrodes <NUM> may be flat ribbon electrode segments, paddle electrode segments, braided or woven electrode segments, mesh electrode segments, directional electrode segments, patch electrode segments or other types of electrode segments configured to deliver a defibrillation shock to the heart <NUM>. Defibrillation electrodes <NUM> may be formed from any of a number of conductive material(s), including but not limited to, metals, metal oxides, metal alloys, coated metals and composite materials based on a combination of platinum, gold, iridium, titanium, tantalum, vanadium, aluminum, copper, zirconium, carbon, graphene, diamond, zirconium, diamond like coatings (DLC), silicon, and/or boron. This also includes glasses and dielectric materials such as borosilicate or chalcogenide glass, zirconia, alumina as well as conductive polymers, semiconductors and conductive ceramics in pure form or with additives such as boron, carbon, gold, silver and similar metal particles and/or fibers from micro to nano dimensions.

In some examples, an electrically insulating material covers respective conductors of defibrillation electrode 32A at coated portions <NUM>. The electrically insulating material, in some cases, prevents conduction of relatively lower voltage signals (e.g., less than <NUM> Volts (V)) between coated portions <NUM> and tissue of patient <NUM>. Additionally, the electrically insulating material may allow conduction of relatively higher voltage signals (e.g., greater than or equal to <NUM> V) between coated portions <NUM> and tissue of patient <NUM>. For example, coated portions <NUM> may be configured to prevent transmission of a pacing pulse, prevent sensing of a cardiac depolarization, and allow transmission of a defibrillation shock, since a voltage of the defibrillation shock is substantially higher than the voltages of the cardiac depolarization and the pacing pulse. The electrically insulating material may be any of a number of materials, such as single or combinations of tantalum pentoxide, titanium oxides, zirconium oxide, vanadium oxide, niobium oxide, doped silicon, silicon dioxide, boron doped diamond, doped glass, ceramic coating or polymer composite or other material that has the property of substantially preventing the transmission or delivery of low voltages while not substantially preventing the transmission or delivery of high voltages.

In some examples, defibrillation electrode 32A is not coated with an electrically insulating material at uncoated portion <NUM>. In other words, uncoated portion <NUM> may represent a section of exposed conductor material on defibrillation electrode 32A, such sections of exposed conductor material allowing for the transmission of lower-voltage signals. For example, uncoated portion <NUM> may be configured to both allow conduction of relatively lower voltage signals (e.g., less than <NUM> V) and allow conduction of relatively higher voltage signals (e.g., greater than or equal to 100V). For example, uncoated portion <NUM> may be configured to transmit a defibrillation shock, transmit a pacing pulse, sense an electrical signal corresponding to a cardiac depolarization, or any combination thereof. As such, an entire length of a defibrillation electrode such as defibrillation electrode 32A may be configured to conduct a defibrillation shock delivered by signal generation circuitry within housing <NUM>, and a portion (e.g., uncoated portion <NUM>) of defibrillation electrode 32A may be configured to transmit pacing pulses and sense cardiac depolarizations. In this way, uncoated portion <NUM> of defibrillation electrode 32A may perform at least some of the same functionalities as pace/sense electrodes <NUM>.

The electrically insulating material may, in some examples, extend around the entire circumference of coated portions <NUM> of defibrillation electrodes <NUM>. In other examples, the electrically insulating material may extend around a portion of the circumference of coated portions <NUM>. For example, the electrically insulating material may extend around a portion of the circumference of coated portions <NUM> that is facing heart <NUM>. The electrically insulating material may be any of a number of material such as single or combinations of tantalum pentoxide, titanium oxides, Zirconium oxide, Vanadium oxide, niobium oxide, doped silicon, silicon dioxide, boron doped diamond, doped glass, ceramic coating or polymer composite or other material that has the property of substantially preventing the transmission or delivery of low voltages while not substantially preventing the transmission or delivery of high voltages. A thickness of the electrically insulating material may vary based on a type of material that defibrillation electrode 32A is made of, the type of electrically insulating material, dimensions of the respective coated portion <NUM>, an expected depth and position of the distal portion of lead <NUM>, e.g., substernal or subcutaneous location. In examples where tantalum pentoxide is the electrically insulating material, the thickness of the electrically insulating material may be within a range from <NUM> micrometers (µm) to less than or equal to <NUM>. However, other thicknesses may be utilized without departing from the scope of this disclosure. In one example, coated portions <NUM> are coated with tantalum pentoxide having a thickness within a range from <NUM> to <NUM> microns. In such an example, the tantalum pentoxide coating significantly blocks current flow up to 100V, thus preventing the sensing of cardiac depolarization events and preventing the transmission of pacing pulses. Additionally, in such an example, electrical signals having voltages higher than 100V (e.g., defibrillation shocks) overcome the electrically insulating property of the tantalum pentoxide coating and may conduct through coated portions <NUM> of defibrillation electrodes <NUM>.

A length of each of defibrillation electrodes <NUM> may be within a range between <NUM> and <NUM>. However, lengths of greater than <NUM> and less than <NUM> may be utilized without departing from the scope of this disclosure. In some examples, defibrillation electrode 32A and defibrillation electrode 32B are the same length. In other examples, defibrillation electrode 32A and defibrillation electrode 32B are of differing lengths. In some examples, first defibrillation electrode 32A and second defibrillation electrode 32B may be spaced apart on lead <NUM> by a distance within a range from <NUM> to <NUM>. In the example illustrated in <FIG>, first defibrillation electrode 32A and second defibrillation electrode 32B are spaced apart by enough of a distance such that second pace/sense electrode 36B is placed between first defibrillation electrode 32A and second defibrillation electrode 32B. In some examples, second pace/sense electrode 36B may be located at or near a median point along a section of lead <NUM> that separates first defibrillation electrode 32A and second defibrillation electrode 32B (i.e., lead section <NUM>). For example, a center of second pace/sense electrode 36B may be located within a range between <NUM>% of the length of lead section <NUM> from a proximal end of lead section <NUM> to <NUM>% of the length of lead section <NUM> from the proximal end of lead section <NUM>. In other words, in an example where a length of lead section <NUM> is <NUM>, the center of second pace/sense electrode 36B may be located within a range from <NUM> from the proximal end of first lead section <NUM> to <NUM> from the proximal end of lead section <NUM>.

Coated portions <NUM> and uncoated portion <NUM> may vary in size. In some examples, an uncoated portion (e.g., uncoated portion <NUM>) may be less than or equal to <NUM>% of the length the respective defibrillation electrode 32A. Additionally, in some examples, uncoated portion <NUM> may be less than or equal to <NUM>% of the length of the respective defibrillation electrode 32A. In some examples, a combined length and/or surface area of all of the uncoated portion <NUM> of defibrillation electrodes <NUM> may be less than or equal to <NUM>% of a combined length and/or surface area of defibrillation electrodes <NUM> or less than or equal to <NUM>% of the combined length and/or surface area of the defibrillation electrodes <NUM>. Each of the uncoated portion <NUM> may, in some examples, have a surface area that is less than or equal to <NUM> square millimeters (mm<NUM>). In other instances, uncoated portion <NUM> may have a surface area that is less than or equal to <NUM><NUM>. Uncoated and coated portions may have sizes other than those described above.

Uncoated portion <NUM> may be located at or near a median point along the length of first defibrillation electrode 32A. For example, a center of uncoated portion <NUM> may be located within a range between <NUM>% of the length of first defibrillation electrode 32A from the proximal end of first defibrillation electrode 32A to <NUM>% of the length of first defibrillation electrode 32A from the proximal end of first defibrillation electrode 32A. In other words, in an example where first defibrillation electrode 32A is <NUM> in length, the center of uncoated portion <NUM> may be located within a range from <NUM> from the proximal end of first defibrillation electrode 32A to <NUM> from the proximal end of first defibrillation electrode 32A. In this way, the respective coated portions (e.g., proximal coated portion 33A and distal coated portion 33B) may be the same length or differ in length based on the location of uncoated portion <NUM> along first defibrillation electrode 32A. For example, if uncoated portion <NUM> is located closer to the proximal end of first defibrillation electrode 32A than the distal end of first defibrillation electrode 32A, a length of proximal coated portion 33A may be shorter than a length of distal coated portion 33B. Additionally, if uncoated portion <NUM> is located closer to the distal end of first defibrillation electrode 32A than the proximal end of first defibrillation electrode 32A, a length of proximal coated portion 33A may be longer than a length of distal coated portion 33B.

<FIG> is a conceptual diagram illustrating vectors available from the distal portion of medical lead <NUM>, in accordance with one or more techniques described herein. The example illustrated in <FIG> includes uncoated portion 34A of defibrillation electrode 32A, first pace/sense electrode 36A, and second pace/sense electrode 36B. Additionally, <FIG> illustrates first vector 110A, second vector 110B, third vector 110C (collectively, "vectors <NUM>") and angles 112A-112C (collectively, "angles <NUM>").

In some examples, IMD <NUM> may be configured to sense, via electrodes on the distal portion of lead <NUM>, cardiac electrograms, e.g., including cardiac depolarizations, or other electrical signals according vectors <NUM>. Each vector of vectors <NUM> may, in some cases, represent a difference in electric potential between respective electric potential signals obtained by a pair of electrodes (e.g., any combination of uncoated portion <NUM> of defibrillation electrodes <NUM>, pace/sense electrodes <NUM>, and electrodes disposed on housing <NUM> of IMD <NUM>). In some examples, a vector may be defined by a set of parameters including a combination of two or more electrodes, a spatial arrangement of the two or more electrodes, and a polarity of each electrode of the two or more electrodes.

For example, processing circuitry <NUM> may be configured to control sensing circuitry <NUM> to obtain a first electrogram via first vector 110A which includes first pace/sense electrode 36A and second pace/sense electrode 36B. In some examples, the first electrogram is proportional to a difference in electric potential between first pace/sense electrode 36A and second pace/sense electrode 36B. Additionally, processing circuitry <NUM> may control sensing circuitry <NUM> to obtain a second electrogram via second vector 110B including first pace/sense electrode 36A and uncoated portion <NUM> of first defibrillation electrode 32A. In some examples, the second electrogram is proportional to a difference in electric potential between first pace/sense electrode 36A and uncoated portion <NUM>. Second vector 110B may form angle 112A with first vector 110A. The angle 112A is within a range from <NUM> degrees to <NUM> degrees. In one example, angle 112A is <NUM> degrees. Since cardiac depolarizations are directional in nature and follow a three-dimensional path through heart <NUM> of patient <NUM>, it may be beneficial for first vector 110A to form an angle with the second vector 110B such IMD <NUM> may obtain different angular perspectives of a directional cardiac depolarization.

Additionally, processing circuitry <NUM> may control sensing circuitry <NUM> to obtain a third electrogram via third vector 110C including second pace/sense electrode 36B and uncoated portion <NUM> of first defibrillation electrode 32A. In some examples, the third electrogram is proportional to a difference in electric potential between second pace/sense electrode 36B and uncoated portion <NUM>. Third vector 110C may form angle 112B with first vector 110A. The angle 112B is within a range from <NUM> degrees to <NUM> degrees. For example, angle 112B may be <NUM> degrees. It may be beneficial for third vector 110C to form an angle with first vector 110A such that IMD <NUM> may obtain another angular perspective of the directional cardiac depolarization in addition to the perspectives provided by first vector 110A and second vector <NUM>10B. Additionally, second vector 110B and third vector 110C may form angle 112C such that first vector 110A, second vector 110B, and third vector 110C form a triangle between first pace/sense electrode 36A, second pace/sense electrode 36B, and uncoated portion <NUM>. In some examples, angle 112C is within a range from <NUM> degrees to <NUM> degrees. For example, angle 112C may be <NUM> degrees. Since first vector 110A, second vector 110B, and third vector 110C form a triangle, a summation of angle 112A, angle 112B, and angle 112C may be <NUM> degrees.

First pace/sense electrode 36A, second pace/sense electrode 36B, and uncoated portion <NUM> may, in some cases, be proximate to a ventricle of heart <NUM>. In some cases, IMD <NUM> may store the first electrogram, the second electrogram, and the third electrogram in a storage device (e.g., storage device <NUM>).

Although the set of vectors including vectors <NUM> are described herein with respect to sensing cardiac depolarizations, IMD <NUM> may also deliver electric stimulation (e.g., pacing pulses) according to vectors <NUM>. For example, processing circuitry <NUM> may control signal generation circuitry <NUM> to deliver electrical stimulation according to any one or more of first vector 110A, second vector 110B, and third vector 110C in order to deliver electrical stimulation to ventricles of heart <NUM>. Since each of the set of vectors offer different perspectives with respect to heart <NUM>, it may be beneficial for IMD <NUM> to deliver electric stimulation according to different combinations of the set of vectors.

Since lead <NUM> is implanted within patient <NUM>, and patient <NUM> moves about over the course of time, lead <NUM> may migrate relative to heart <NUM> after lead <NUM> is implanted within patient <NUM>. Angles <NUM>, in some cases, may change over a period of time due to such migration. For example, if the distal portion of lead <NUM> is compressed such that pace/sense electrodes <NUM> move closer together, angles 112A and 112B, may increase while angle 112C and decreases. Additionally, if the distal portion of lead <NUM> is stretched such that pace/sense electrodes <NUM> move farther apart, angles 112A and 112B may decrease while angles 112C increases. Any sort of relative movement of uncoated portion <NUM> and pace/sense electrodes <NUM> may cause angles <NUM> to change. Although three vectors <NUM> are described with respect to <FIG>, IMD <NUM> may be configured to collect data or deliver therapy (e.g., pacing pulses) according to other vectors not illustrated in <FIG>. Such other vectors may represent differences in measured parameters between any two or more of uncoated portion <NUM> of defibrillation electrodes <NUM>, pace/sense electrodes <NUM>, and electrodes disposed on can <NUM> of IMD <NUM>.

<FIG> is a side view of the distal portion of medical lead <NUM>, in accordance with one or more techniques described herein. Although the distal portion of medical lead <NUM> forms a curvilinear shape, from a side view, the distal portion of medical lead <NUM> appears to be straight. For example, the curvilinear portions of the distal portion of medical lead <NUM> extend into and out from the plane of <FIG>. In other words, <FIG> illustrates a view of lead <NUM> where the line extending from A to A' as seen in <FIG> extends into the page. As such, defibrillation electrodes <NUM> having coated portions <NUM> and uncoated portion <NUM>, and pace/sense electrodes <NUM>, may be represented in <FIG> according to the side view of the distal end of lead <NUM>.

<FIG> is a side view of a distal portion of another example medical lead <NUM>, in accordance with one or more techniques described herein. Medical lead <NUM> may be similar to medical lead <NUM> except for differences outlined below. The example of <FIG> may include first defibrillation electrode 122A and second defibrillation electrode 122B (collectively, "defibrillation electrodes <NUM>"), and pace/sense electrode 126A and pace/sense electrode 126B (collectively, "pace/sense electrodes <NUM>"). Defibrillation electrode 122A includes coated portion <NUM> and uncoated portion <NUM>. Second defibrillation electrode 122B may, in some cases, be entirely uncoated. The example of <FIG> may be substantially the same as the example of <FIG>, <FIG>, and <FIG> except that in the example of <FIG>, uncoated portion <NUM> may be partially disposed around the circumference of lead <NUM> rather than being fully disposed around the circumference of lead <NUM>. The remaining portions of the circumference of lead <NUM> (e.g., the portion that does not include uncoated portions <NUM>) may be coated by the electrically insulating material. As such, coated portion <NUM> may cover portions of the respective defibrillation electrodes <NUM> proximal and distal to uncoated portion <NUM> and the remaining portions of the circumference of lead <NUM> that do not include uncoated portion <NUM>.

<FIG> is a flow diagram illustrating an example operation for sensing electrical signals, in accordance with one or more techniques of this disclosure. For convenience, <FIG> is described with respect to IMD <NUM> and external device <NUM> of <FIG>. However, the techniques of <FIG> may be performed by different components of IMD <NUM> or by additional or alternative medical devices.

IMD <NUM>, in some examples, may include lead <NUM>. Lead <NUM> may include a lead body having a curvilinear shape. For example, a distal portion of lead <NUM> may include one or more arc-shaped portions. The distal portion of lead <NUM> may include two arc-shaped portions, which together may resemble the Greek letter epsilon, "ε. " In some examples, defibrillation electrodes <NUM> are each carried by one of the two respective arc-shaped portions of the lead body distal portion. The two arc-shaped portions extend or curve in the same direction away from a central axis of the distal portion of lead <NUM>. In some examples, pace/sense electrodes <NUM> may be disposed on the lead body such that pace/sense electrodes <NUM> are substantially aligned with the central axis. In such examples, mid-points of defibrillation electrodes <NUM> are laterally offset from pace/sense electrodes <NUM>. Respective uncoated portion <NUM> of defibrillation electrodes <NUM> may be located at or near mid-points of defibrillation electrodes <NUM>. Other examples of extra-cardiovascular leads including one or more defibrillation electrodes <NUM> and one or more pace/sense electrodes <NUM> carried by the curvilinear (e.g., curving, serpentine, undulating or zig-zagging) distal portion of lead <NUM> also may be implemented using the techniques described herein.

Processing circuitry <NUM> of IMD <NUM> selects one or more sensing vectors from a set of non-parallel vectors (<NUM>). Additionally, processing circuitry <NUM> selects one or more therapy vectors from the set of non-parallel vectors (<NUM>). The set of non-parallel vectors may include a first vector, a second vector, and a third vector. In some examples, the first vector may include first pace/sense electrode 36A and second pace/sense electrode 36B, the second vector may include first pace/sense electrode 36A and uncoated portion <NUM>, and the third vector may include second pace/sense electrode 36B and uncoated portion <NUM>. IMD <NUM> senses electrical signals and delivers therapy via the selected vectors (<NUM>). For example, sensing circuitry <NUM> of IMD <NUM> may sense the electrical signals according to the one or more selected sensing vectors and signal generation circuitry <NUM> of IMD <NUM> may deliver the therapy according to the one or more selected therapy vectors.

At block <NUM>, processing circuitry <NUM> may determine whether to update the vector selections. For example, processing circuitry <NUM> may determine whether to update the vector selections based on one or more of a vector update schedule, user input, a detection of a loss of therapy effectiveness (e.g., a loss of therapy capture), and a detection of a loss of sensing effectiveness (e.g., a detection of under sensing of cardiac depolarizations). If processing circuitry <NUM> determines not to update the vector selections ("NO" branch of block <NUM>), the example operation returns to block <NUM> and IMD <NUM> senses electrical signals and delivers therapy via the selected vectors. If processing circuitry <NUM> determines to update the vector selections ("YES" branch of block <NUM>), the example operation returns to block <NUM> and processing circuitry <NUM> selects one or more sensing vectors from the set of non-parallel vectors and processing circuitry <NUM> selects one or more therapy vectors from the set of non-parallel vectors.

The techniques described in this disclosure may be implemented, at least in part, in hardware, software, firmware, or any combination thereof. For example, various aspects of the techniques may be implemented within one or more microprocessors, DSPs, ASICs, FPGAs, or any other equivalent integrated or discrete logic QRS circuitry, as well as any combinations of such components, embodied in external devices, such as physician or patient programmers, stimulators, or other devices. The terms "processor" and "processing circuitry" may generally refer to any of the foregoing logic circuitry, alone or in combination with other logic circuitry, or any other equivalent circuitry, and alone or in combination with other digital or analog circuitry.

For aspects implemented in software, at least some of the functionality ascribed to the systems and devices described in this disclosure may be embodied as instructions on a computer-readable storage medium such as RAM, DRAM, SRAM, magnetic discs, optical discs, flash memories, or forms of EPROM or EEPROM. The instructions may be executed to support one or more aspects of the functionality described in this disclosure.

Claim 1:
A medical electrical lead (<NUM>, <NUM>) comprising:
a lead body;
a high voltage electrode (<NUM>, 32A, 32B, <NUM>, 122A, 122B) positioned on the lead body, the high voltage electrode (<NUM>, 32A, 32B, <NUM>, 122A, 122B) comprising a proximal coated portion (33A, <NUM>), a distal coated portion (33B, <NUM>), and an uncoated portion (<NUM>, <NUM>) between the proximal coated portion (33A, <NUM>) and the distal coated portion (33B, <NUM>),
wherein the proximal coated portion (33A, <NUM>) and the distal coated portion (33B, <NUM>) are coated with an electrically insulating material configured to prevent conduction of signals having a first range of voltages between the high voltage electrode (<NUM>, 32A, 32B, <NUM>, 122A, 122B) and patient (<NUM>) tissue and allow conduction of signals having a second range of voltages between the high voltage electrode (<NUM>, 32A, 32B, <NUM>, 122A, 122B) and the patient (<NUM>) tissue, wherein the first range of voltages is lower than the second range of voltages; and
a set of low voltage electrodes (<NUM>, 36A, 36B, <NUM>, 126A, 126B) positioned on the lead body, the set of low voltage electrodes (<NUM>, 36A, 36B, <NUM>, 126A, 126B) comprising a first low voltage electrode (36A, 126A) and a second low voltage electrode (36B, 126B) distal to the first low voltage electrode (36A, 126A), wherein the set of low voltage electrodes (<NUM>, 36A, 36B, <NUM>, 126A, 126B) and the uncoated portion (<NUM>, <NUM>) are positioned on the lead body such that:
a first angle (112A) is formed between a first line passing through the first low voltage electrode (36A, 126A) and the second low voltage electrode (36B, 126B) and a second line passing through the first low voltage electrode (36A, 126A) and the uncoated portion (<NUM>, <NUM>), and
a second angle (112B) is formed between the first line and a third line passing through the second low voltage electrode (36B, 126B) and the uncoated portion (<NUM>, <NUM>),
wherein the first angle (112A) is within a range from thirty degrees to sixty degrees, and
wherein the second angle (112B) is within a range from thirty degrees to sixty degrees.