Patent Description:
Implantable medical devices (IMDs), such as cardiac pacemakers or implantable cardioverter defibrillators, deliver therapeutic stimulation to patients' hearts thereby improving the lives of millions of patients living with heart conditions. Conventional pacing techniques involve pacing one or more of the four chambers of patient's heart <NUM>-left atrium (LA) <NUM>, right atrium (RA) <NUM>, left ventricle (LV) <NUM> and right ventricle (RV) <NUM>, all of which are shown in <FIG>. One common conventional therapeutic pacing technique that treats a slow heart rate, referred to as Bradycardia, involves delivering an electrical pulse to a patient's right ventricular tissue. In response to the electrical pulse, both the right and left ventricles contract. However, the heart beat process may be significantly delayed because the pulse travels from the right ventricle through the left ventricle. The electrical pulse passes through the muscle cells that are referred to as myocytes. Myocyte-to-myocyte conduction may be very slow. Delayed electrical pulses can cause the left ventricle to be unable to maintain synchrony with the right ventricle.

Over time, the left ventricle can become significantly inefficient at pumping blood to the body. In some patients, heart failure can develop such that the heart is too weak to pump blood to the body. Heart failure may be a devastating diagnosis since, for example, fifty percent of the heart failure patients have a life expectancy of five years. To avoid the potential development of heart failure, some physicians have considered alternative pacing methods that involve the cardiac conduction system. The cardiac conduction system, like a "super highway," may be described as quickly conducting electrical pulses whereas pacing cardiac muscle tissue may slowly conduct electrical pulses, like "traveling on a dirt road.

The cardiac conduction system includes sinoatrial node (SA node) <NUM>, atrial internodal tracts <NUM>, <NUM>, <NUM> (i.e., anterior internodal <NUM>, middle internodal <NUM>, and posterior internodal <NUM>), atrioventricular node (AV node) <NUM>, His bundle <NUM> (also known as atrioventricular bundle or bundle of His), and right and left bundle branches 8a, 8b. <FIG> also shows the arch of aorta <NUM> and Bachman's bundle <NUM>. The SA node, located at the junction of the superior vena cava and right atrium, is considered to be the natural pacemaker of the heart since it continuously and repeatedly emits electrical impulses. The electrical impulse spreads through the muscles of right atrium <NUM> to left atrium <NUM> to cause synchronous contraction of the atria. Electrical impulses are also carried through atrial internodal tracts to atrioventricular (AV) node <NUM> - the sole connection between the atria and the ventricles. Conduction through the AV nodal tissue takes longer than through the atrial tissue, resulting in a delay between atrial contraction and the start of ventricular contraction. The AV delay, which is the delay between atrial contraction and ventricular contractor, allows the atria to empty blood into the ventricles. Then, the valves between the atria and ventricles close before causing ventricular contraction via branches of the bundle of His. His bundle <NUM> is located in the membranous atrioventricular septum near the annulus of the tricuspid valve. His bundle <NUM> splits into right and left bundle branches 8a, 8b and are formed of specialized fibers called "Purkinje fibers" <NUM>. Purkinje fibers <NUM> may be described as rapidly conducting an action potential down the ventricular septum (VS), spreading the depolarization wavefront quickly through the remaining ventricular myocardium, and producing a coordinated contraction of the ventricular muscle mass.

While cardiac conduction system pacing therapy is increasingly used as an alternative to traditional pacing techniques, cardiac conduction system pacing therapy has not been widely adopted for a variety of reasons. For example, cardiac conduction system pacing electrodes should be positioned within precise target locations (e.g., within about <NUM> millimeter) of portions or regions of the cardiac conduction system, such as the His bundle, which may be difficult. Additionally, adjustment of cardiac conduction system pacing therapy during delivery of therapy may be challenging. Further, determination of whether the cardiac conduction system pacing therapy is selective (i.e., only pacing the cardiac conduction system) or non-selective (i.e., pacing both the cardiac conduction system and the myocardial tissue) may also be challenging. It is desirable to develop new cardiac conduction system pacing therapy systems, devices, and methods and systems that overcome some of the disadvantages associated with previously-performed cardiac conduction system pacing therapies.

<CIT> relates to His-bundle pacing for rate regularization.

<CIT> relates to a method and apparatus for right ventricular resynchronization.

This disclosure generally relates to pacing the cardiac conduction system such as, for example, the His-Purkinje system, including His bundle, left bundle branches, and right bundle branches. In particular, illustrative devices and methods are described herein to provide adaptative cardiac conduction system pacing therapy that may selectively provide pacing therapy in conjunction with traditional left ventricular pacing therapy. Such adaptive cardiac conduction system pacing therapy may be able to determine and adjust an AV delay and a VV delay (between the cardiac conduction system pacing therapy and traditional left ventricular pacing therapy) based on near-field or far-field signals so as to be able to provide effective cardiac therapy to a patient. Additionally, such adaptive cardiac conduction system pacing therapy may be able switch between cardiac conduction system pacing therapy alone and cardiac conduction system pacing therapy in combination with traditional left ventricular pacing therapy so as to be able to provide effective cardiac therapy to a patient.

The illustrative devices and methods, the methods not being claimed as such, may be described as utilizing a triple-chamber device solution for cardiac resynchronization therapy-indicated patients that may include a standard right atrial lead, a <NUM> or <NUM> D lead for His or left bundle branch (LBB) area pacing, and an left ventricular lead. The illustrative devices and methods may use one or more processes for adaptive left ventricular pacing based on efficacy of left ventricular activation from His/LBB area pacing. Such processes may "'adapt"' between His or LBB area only pacing and His or LBB area in conjunction with left ventricular pacing based on an electrocardiogram based efficacy metric for preactivation of the left ventricle with conduction system pacing.

One illustrative implantable medical device may include a plurality of implantable electrodes to sense and pace a patient's heart. The plurality of electrodes may include a left ventricular electrode positionable proximate the patient's left ventricle and a cardiac conduction system electrode positionable proximate a portion of the patient's cardiac conduction system. The deice may further include a computing apparatus comprising processing circuitry. The computing apparatus may be operably coupled to the plurality of implantable electrodes and configured to initiate delivery of cardiac conduction system pacing therapy to the patient's cardiac conduction system using the cardiac conduction system electrode and monitor local electrical activity of the patient using the left ventricular electrode during the delivery of cardiac conduction system pacing therapy using the cardiac conduction system electrode. The computing apparatus may be further configured to switch to delivery of both cardiac conduction system pacing therapy to the patient's cardiac conduction system using the cardiac conduction system electrode and left ventricular pacing therapy to the patient's left ventricle using the left ventricular electrode in response to the monitored local electrical activity.

One illustrative method not claimed as such may include delivering cardiac conduction system pacing therapy to a patient's cardiac conduction system using a cardiac conduction system electrode implanted proximate a portion of the patient's cardiac conduction system and monitoring local electrical activity of the patient using a left ventricular electrode implanted proximate the patient's left ventricle during the delivery of cardiac conduction system pacing therapy using the cardiac conduction system electrode. The illustrative method may further include switching to delivery of both cardiac conduction system pacing therapy to the patient's cardiac conduction system using the cardiac conduction system electrode and left ventricular pacing therapy to the patient's left ventricle using the left ventricular electrode in response to the monitored local electrical activity.

One illustrative implantable medical device may include a plurality of implantable electrodes to sense and pace a patient's heart. The plurality of electrodes may include a left ventricular electrode positionable proximate the patient's left ventricle and a cardiac conduction system electrode positionable proximate a portion of the patient's cardiac conduction system. The deice may further include a computing apparatus comprising processing circuitry. The computing apparatus may be operably coupled to the plurality of implantable electrodes and configured to determine a paced AV delay for use in delivery of cardiac conduction system pacing therapy using the cardiac conduction system electrode. The paced AV delay is a time period between an atrial event and delivery of cardiac conduction system pacing therapy. The computing apparatus may be further configured to determine a paced VV delay for use in delivery of cardiac conduction system pacing therapy using the cardiac conduction system electrode and delivery of left ventricular pacing therapy using the left ventricular electrode. The paced VV delay is a time period between the delivery of the left ventricular pacing therapy and the delivery of the cardiac conduction system pacing therapy. The computing apparatus may be further configured to deliver either cardiac conduction system pacing therapy using the paced AV delay or cardiac conduction system pacing therapy and left ventricular pacing therapy using the paced AV delay and the paced VV delay.

One illustrative method not claimed as such may include determining a paced AV delay for use in delivery of cardiac conduction system pacing therapy using a cardiac conduction system electrode implanted proximate a portion of the patient's cardiac conduction system. The paced AV delay is a time period between an atrial event and delivery of cardiac conduction system pacing therapy. The illustrative method may further include determining a paced VV delay for use in delivery of cardiac conduction system pacing therapy using the cardiac conduction system electrode and delivery of left ventricular pacing therapy using a left ventricular electrode implanted proximate the patient's left ventricle. The paced VV delay is a time period between the delivery of the left ventricular pacing therapy and the delivery of the cardiac conduction system pacing therapy. The illustrative method may further include delivering either cardiac conduction system pacing therapy using the paced AV delay or cardiac conduction system pacing therapy and left ventricular pacing therapy using the paced AV delay and the paced VV delay.

Left bundle branch (LBB) area pacing may be important for treating both bradycardia and heart failure, left bundle branch block (HF-LBBB) patients for correcting left bundle branch block. It may be described that LBB is an optimal area for physiologic pacing. However, distinction of selective versus non-selective capture of the LBB may be important for titrating optimal pacing at the LBB. Selective capture includes capture of the left bundle branch without local myocardial capture and is closer to physiologic or normal activation of left bundle branch compared to non-selective pacing. Non-selective pacing also involves cell-to-cell stimulation of the septal area and may provide a slower path of whole-heart activation than selective. The illustrate devices and methods may utilize a near-field electrogram based device diagnostic for distinguishing between selective and non-selective capture, which may be important for long-term monitoring of efficacy of left bundle pacing. With the goal being selective capture, if non-selective capture is detected, one or more pacing parameters (e.g., pacing outputs, vectors, etc.) may be adjusted to achieve selective capture.

Illustrative devices and methods are described herein to provide cardiac conduction system pacing therapy and to determine whether such cardiac conduction system pacing therapy has selectively or non-selectively captured the cardiac conduction system. Cardiac conduction system pacing therapy having selective capture of the cardiac conduction system may be defined as pacing therapy that delivers pacing therapy only to the cardiac conduction system and that does not delver pacing therapy directly to myocardial or muscular cardiac tissue. In other words, selective cardiac conduction system pacing therapy paces the cardiac conduction system alone. Cardiac conduction system pacing therapy having non-selective capture of the cardiac conduction system may be defined as pacing therapy that delivers pacing therapy to the cardiac conduction system and directly to the myocardial or muscular cardiac tissue. In other words, non-selective cardiac conduction system pacing therapy paces both the cardiac conduction system and myocardial or muscular cardiac tissue. The illustrative devices and methods, using a near-field signal, may be able to determine whether the delivered cardiac conduction system pacing therapy is selective or non-selective, which may be helpful in delivery effective cardiac therapy to a patient.

One illustrative implantable medical device may include a plurality of implantable electrodes to sense and pace a patient's heart and a computing apparatus comprising processing circuitry. The computing apparatus may be operably coupled to the plurality of implantable electrodes and configured to initiate a delivery of pacing therapy to the patient's heart, monitor a near-field signal over a sensing time period proximate the left bundle branch using the plurality of implantable electrodes following the delivery of pacing therapy, generate a derivative signal based on the near-field signal, and determine whether the pacing therapy has selective or non-selective capture of the cardiac conduction system based on the derivative signal.

The above summary is not intended to describe each embodiment or every implementation of the present disclosure. A more complete understanding will become apparent and appreciated by referring to the following detailed description and claims taken in conjunction with the accompanying drawings.

In the following detailed description of illustrative embodiments, reference is made to the accompanying figures of the drawing which form a part hereof, and in which are shown, by way of illustration, specific embodiments which may be practiced. It is to be understood that other embodiments may be utilized, and structural changes may be made without departing from (e.g., still falling within) the scope of the disclosure presented hereby.

Illustrative devices and methods shall be described with reference to <FIG>. It will be apparent to one skilled in the art that elements or processes from one embodiment may be used in combination with elements or processes of the other embodiments, and that the possible embodiments of such devices and methods using combinations of features set forth herein is not limited to the specific embodiments shown in the Figures and/or described herein. Further, it will be recognized that the embodiments described herein may include many elements that are not necessarily shown to scale. Still further, it will be recognized that timing of the processes and the size and shape of various elements herein may be modified but still fall within the scope of the present disclosure, although certain timings, one or more shapes and/or sizes, or types of elements, may be advantageous over others.

<FIG> are conceptual diagrams illustrating one example therapy system <NUM> that may be used to provide therapy to heart <NUM> of patient <NUM>. Patient <NUM> ordinarily, but not necessarily, will be a human. Therapy system <NUM> includes IMD <NUM>, which is coupled to leads <NUM>, <NUM>, <NUM> and programmer <NUM>. IMD <NUM> may be, for example, an implantable pacemaker, cardioverter, and/or defibrillator that provides electrical signals to heart <NUM> via electrodes coupled to one or more of leads <NUM>, <NUM>, <NUM>. Further non-limiting examples of IMD <NUM> include: a pacemaker with a medical lead, an implantable cardioverter-defibrillator (ICD), an intracardiac device, a leadless pacing device (LPD), a subcutaneous ICD (S-ICD), and a subcutaneous medical device (e.g., nerve stimulator, inserted monitoring device, etc.).

Leads <NUM>, <NUM>, <NUM> extend into heart <NUM> of patient <NUM> to sense electrical activity of heart <NUM> and/or deliver electrical stimulation to heart <NUM>. In the example shown in <FIG>, right ventricular (RV) lead <NUM> extends through one or more veins (not shown), the superior vena cava (not shown), and right atrium (RA) <NUM>, and into right ventricle <NUM>. Left ventricular (LV) coronary sinus lead <NUM> extends through one or more veins, the vena cava, right atrium <NUM>, and into the coronary sinus <NUM> to a region adjacent to the free wall of left ventricle <NUM> of heart <NUM>. Cardiac conduction system pacing therapy lead <NUM> (e.g., His-bundle or bundle-branch pacing lead) extends through one or more veins and the vena cava, and into the right atrium <NUM> of heart <NUM> to pace the cardiac conduction system (e.g., triangle of Koch, septal wall, left bundle branch, right bundle branch, the His bundle, etc.). In some embodiments, the cardiac conduction system pacing therapy lead <NUM> may be positioned within about <NUM> millimeter of the triangle of Koch, septal wall, His bundle, or one or both bundle branches.

As used herein, cardiac conduction system pacing therapy refers to any pacing therapy configured to deliver pacing therapy (e.g., pacing pulses) to the cardiac conduction system including, e.g., the His bundle, left bundle branch, right bundle branch, etc. As used herein, the term "activation" refers to a sensed or paced event. For example, an atrial activation may refer to an atrial sense or event (As) or an atrial pace or artifact of atrial pacing (Ap). Similarly, a ventricular activation may refer to a ventricular sense or event (Vs) or a ventricular pace or artifact of ventricular pacing (Vp), which may be described as ventricular stimulation pulses. In some embodiments, activation interval can be detected from As or Ap to Vs or Vp, as well as Vp to Vs. In particular, activation intervals may include a pacing (Ap or Vp) to ventricular interval (LV or RV sense) or an atrial-sensing (As) to ventricular-sensing interval (LV or RV sense).

One example of a cardiac conduction system pacing therapy lead <NUM> (e.g., a His lead) can be the S ELECTSURE™ <NUM>. A description of the SELECTSURE™ <NUM> is found in the Medtronic model SELECTSURE™ <NUM> manual (<NUM>). The SELECTSURE™ <NUM> includes two or more conductors with or without lumens.

An elongated conductor of the lead may extend through a hermetic feedthrough assembly, and within an insulative tubular member of the lead, and may electrically couple an electrical pulse generator (contained within housing) to the helical tip electrode, or cardiac conduction system electrode, of the cardiac conduction system pacing therapy lead <NUM>. The conductor may be formed by one or more electrically conductive wires, for example, MP35N alloy known to those skilled in the art, in a coiled or cabled configuration, and the insulative tubular member may be any suitable medical grade polymer, for example, polyurethane, silicone rubber, or a blend thereof. According to an illustrative embodiment, the flexible lead body extends a pre-specified length (e.g., about <NUM> centimeters (cm) to about <NUM>, or about <NUM> to <NUM>) from a proximal end of housing to the other end. The lead body is less than about <NUM> French (FR) but typically in the range of about <NUM> to <NUM> FR in size. In one or more embodiments, about <NUM> to about <NUM> FR size lead body is employed.

Cardiac conduction system pacing therapy can be performed by other leads. Another illustrative lead, including two or more pacing electrodes, can be used to deliver multisite pacing pulses to the bundle of His or one or both bundle branches. Multisite pacing can be delivered simultaneously or sequentially, as described and shown by <CIT>, filed on April <NUM>, <NUM>, entitled EFFICIENT DELIVERY OF MULTI-SITE PACING, the disclosure of which is incorporated by reference in its entirety.

Since the electrodes in multi-site or multi-point stimulation may be in close proximity to each other, it may be important to detect and verify effective capture of individual electrodes during delivery of such therapy. Delivering multisite pacing pulses may include delivering pacing pulses to a first tissue site and a second tissue site through first and second pacing electrodes, respectively, all of which may occur within the same cardiac cycle.

In particular, a lead configured to perform multi-site pacing, which is different than LV coronary sinus lead <NUM>, can be placed in the ventricular septum with the first (distal) electrode on the left side of the ventricular septum for left bundle branch pacing and with the second electrode (proximal) on the right side of the septum for pacing the right bundle branch. An interelectrode distance may be defined as the distance between the first and second electrodes, or the distance that the electrodes are apart. In some embodiments, the interelectrode distance is at least about <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> millimeters (mm). In some embodiments, the interelectrode distance is at most about <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>. For example, the interelectrode distance may be in a range from about <NUM> to <NUM> apart. Once the pacing is delivered, both the left bundle branch and the right bundle branch may be stimulated such that both ventricles are naturally or near-naturally synchronized. In contrast, in traditional CRT, the ventricles may be described as not naturally synchronized.

A single lead, including two (or more) pacing electrodes (e.g., cathodes) may deliver cathode pacing outputs at two separate locations (e.g., left and right bundle branches), so both bundle branches can be excited at the same time.

His bundle pacing, though a leading candidate for physiological pacing, may be hard to implant, may have a relatively high pacing threshold, and may have an unstable long-term pacing threshold in patients with conduction disease. Bundle branch pacing may bypass the pathological region and may have a low and stable pacing threshold. In some embodiments, only one bundle branch may be paced by using pacing leads. One aspect of this disclosure provides pacing of both bundle branches at the same time (e.g., dual bundle branch pacing), which may mimic intrinsic activation propagation via the His bundle-Purkinje conduction system, e.g., paced activation propagates via both bundle branches to both ventricles for synchronized contraction. Traditional His bundle pacing, on the other hand, typically paces the His bundle proximal to the bundle branches. In some embodiments, IMD <NUM> may include one, two, or more electrodes located in one or more bundle branches configured for bundle branch pacing. In some embodiments, IMD <NUM> may be an intracardiac pacemaker or leadless pacing device (LPD).

As used herein, "leadless" refers to a device being free of a lead extending out of patient's heart <NUM>. In other words, a leadless device may have a lead that does not extend from outside of the patient's heart to inside of the patient's heart. Some leadless devices may be introduced through a vein, but once implanted, the devices are free of, or may not include, any transvenous lead and may be configured to provide cardiac therapy without using any transvenous lead. In one or more embodiments, an LPD for bundle pacing does not use a lead to operably connect to an electrode disposed proximate to the septum when a housing of the device is positioned in the atrium. A leadless electrode may be leadlessly coupled to the housing of the medical device without using a lead between the electrode and the housing.

IMD <NUM> may sense electrical signals attendant to the depolarization and repolarization of heart <NUM> via electrodes (not shown in <FIG>) coupled to at least one of leads <NUM>, <NUM>, <NUM>. In some examples, IMD <NUM> provides pacing pulses to heart <NUM> based on the electrical signals sensed within heart <NUM>. The configurations of electrodes used by IMD <NUM> for sensing and pacing may be unipolar or bipolar. IMD <NUM> may also provide defibrillation therapy and/or cardioversion therapy via electrodes located on at least one of leads <NUM>, <NUM>, <NUM>. IMD <NUM> may detect arrhythmia of heart <NUM>, such as fibrillation of ventricles <NUM> and <NUM>, and deliver defibrillation therapy to heart <NUM> in the form of electrical pulses. In some examples, IMD <NUM> may be programmed to deliver a progression of therapies, e.g., pulses with increasing energy levels, until a fibrillation of heart <NUM> is stopped. IMD <NUM> may detect fibrillation employing one or more fibrillation detection techniques known in the art.

In some examples, programmer <NUM> (<FIG>) may be a handheld computing device or a computer workstation or a mobile phone. Programmer <NUM> may include a user interface that receives input from a user. The user interface may include, for example, a keypad and a display, which may for example, be a cathode ray tube (CRT) display, a liquid crystal display (LCD) or light emitting diode (LED) display. The keypad may take the form of an alphanumeric keypad or a reduced set of keys associated with particular functions. Programmer <NUM> can additionally or alternatively include a peripheral pointing device, such as a mouse, via which a user may interact with the user interface. In some embodiments, a display of programmer <NUM> may include a touch screen display, and a user may interact with programmer <NUM> via the display. Through the graphical user interface on programmer <NUM>, a user may select one or more optimized parameters.

Additionally, various pacing settings may be adjusted, or configured, based on various sensed signals. For example, various near-field and far-field signals may be sensed by one or more electrodes of the IMD <NUM> and/or other devices operatively coupled thereto. For example, Vp to QRS end or offset within a near-field or far-field signal may be used to adjust or configure the AV delay of cardiac conduction system pacing therapy. Further, for example, QRS within a near-field or far-field signal may be used to adjust or configure the VV delay between cardiac conduction system pacing therapy and traditional left ventricular pacing therapy. Still further, left bundle branch electrocardiogram following a post-blanking time period after ventricular pacing may be analyzed determine whether cardiac conduction system pacing therapy is selective or non-selective. Thus, QRS complexes may be detected using near field and/or far-field electrical signals. For example, the far-field electrical signals may be sensed in a far-field electrogram (EGM) monitored by IMD <NUM> and a corresponding lead or a separate device, such as a subcutaneously implanted device. QRS duration is the time from which the Q wave is detected until the S wave ends.

As used herein, the term "far-field" electrical signal refers to the result of measuring cardiac activity using a sensor, or electrode, positioned outside of an area of interest. For example, an ECG signal measured from an electrode positioned outside of the patient's heart is one example of a far-field electrical signal of the patient's heart. As another example, a far-field electrical signal representing electrical activity of a chamber of the patient's heart may be measured from a sensor, or electrode, positioned in an adjacent chamber.

As used herein, the term "near-field" electrical signal refers to the result of measuring cardiac activity using a sensor, or electrode, positioned near an area of interest. For example, an EGM signal measured from an electrode positioned on the left side of the patient's ventricular septum is one example of a near-field electrical signal of the patient's LV.

R-wave timing is the time in which QRS is detected. Typically, R-wave timing includes using the maximal first derivative of an R-wave upstroke (or the time of the maximal R-wave value). R-wave timing is also used in the device marker channel to indicate the time of the R-wave or the time of ventricular activation.

Pacing-RV sensing or pacing-LV sensing (e.g., pacing-to-RV sensing or pacing-to-LV sensing) is the time interval from the pacing (or pacing artifact) to the time of RV or LV sensing. For example, if pacing-RV sensing is much longer than pacing-LV sensing, this may indicate that the LV activation is occurring much earlier than RV activation (so pacing-RV sensing is longer), then RV pacing may be delivered in synchronization with bundle pacing, so RV and LV activation can occur approximately at the same time.

A user, such as a physician, technician, or other clinician, may interact with programmer <NUM> to communicate with IMD <NUM>. For example, the user may interact with programmer <NUM> to retrieve physiological or diagnostic information from IMD <NUM>. One illustrative IMD <NUM> is described in the Medtronic AMPLIA MRITM CRT-D SURESCAN™ DTMB2D1 manual, which is incorporated by reference in its entirety. A user may also interact with programmer <NUM> to program IMD <NUM>, e.g., select values for operational parameters of the IMD.

IMD <NUM> and programmer <NUM> may communicate via wireless communication using any techniques known in the art. Examples of communication techniques may include, for example, low frequency or radiofrequency (RF) telemetry, but other techniques are also contemplated. In some examples, programmer <NUM> may include a programming head that may be placed proximate to the patient's body near the IMD <NUM> implant site in order to improve the quality or security of communication between IMD <NUM> and programmer <NUM>.

<FIG> is a conceptual diagram illustrating IMD <NUM> and leads <NUM>, <NUM>, <NUM> of therapy system <NUM> in greater detail. The triple chamber IMD <NUM> may be used for cardiac rhythm therapy and defibrillation or cardioversion therapy (CRT-D). Leads <NUM>, <NUM>, <NUM> may be electrically coupled to a stimulation generator, a sensing module, or other modules of IMD <NUM> via connector block <NUM>. In some examples, proximal ends of leads <NUM>, <NUM>, <NUM> may include electrical contacts that electrically couple to respective electrical contacts within connector block <NUM>. In addition, in some examples, leads <NUM>, <NUM>, <NUM> may be mechanically coupled to connector block <NUM> with the aid of set screws, connection pins, or another suitable mechanical coupling mechanism.

Each of the leads <NUM>, <NUM>, <NUM> includes an elongated, insulative lead body, which may carry any number of concentric coiled conductors separated from one another by tubular, insulative sheaths. In the illustrated example, an optional pressure sensor <NUM> and bipolar electrodes <NUM> and <NUM> are located proximate to a distal end of lead <NUM>. In addition, bipolar electrodes <NUM> and <NUM> are located proximate to a distal end of lead <NUM> and bipolar electrodes <NUM> and <NUM> are located proximate to a distal end of lead <NUM>. In <FIG>, pressure sensor <NUM> is disposed in right ventricle <NUM>. Pressure sensor <NUM> may respond to an absolute pressure inside right ventricle <NUM>, and may be, for example, a capacitive or piezoelectric absolute pressure sensor. In other examples, pressure sensor <NUM> may be positioned within other regions of heart <NUM> and may monitor pressure within one or more of the other regions of heart <NUM>, or pressure sensor <NUM> may be positioned elsewhere within or proximate to the cardiovascular system of patient <NUM> to monitor cardiovascular pressure associated with mechanical contraction of the heart. Optionally, a pressure sensor in the pulmonary artery can be used that is in communication with IMD <NUM>.

Electrodes <NUM>, <NUM> and <NUM> may take the form of ring electrodes, and electrodes <NUM>, <NUM> and <NUM> may take the form of extendable and/or fixed helix tip electrodes mounted within insulative electrode heads <NUM>, <NUM> and <NUM>, respectively. Each of electrodes <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> may be electrically coupled to a respective one of the coiled conductors within the lead body of its associated lead <NUM>, <NUM>, <NUM>, and thereby coupled to respective ones of the electrical contacts on the proximal end of leads <NUM>, <NUM><NUM>.

Electrodes <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> may sense electrical signals attendant to the depolarization and repolarization of heart <NUM>. The electrical signals are conducted to IMD <NUM> via the respective leads <NUM>, <NUM>, <NUM>. In some examples, IMD <NUM> also delivers pacing pulses via electrodes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> to cause depolarization of cardiac tissue of heart <NUM>. In some examples, as illustrated in <FIG>, IMD <NUM> includes one or more housing electrodes, such as housing electrode <NUM>, which may be formed integrally with an outer surface of hermetically-sealed housing <NUM> of IMD <NUM> or otherwise coupled to housing <NUM>. In some examples, housing electrode <NUM> may be defined by an uninsulated portion of an outward facing portion of housing <NUM> of IMD <NUM>. Electrode <NUM> may be used for pacing and/or sensing of the His bundle or bundle branch tissue. Other divisions between insulated and uninsulated portions of housing <NUM> may be employed to define two or more housing electrodes. In some examples, housing electrode <NUM> includes substantially all of housing <NUM>. Any of the electrodes <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> may be used for unipolar sensing or pacing in combination with housing electrode <NUM> or for bipolar sensing with two electrodes in the same pacing lead. In one or more embodiments, housing <NUM> may enclose a stimulation generator (see <FIG>) that generates cardiac pacing pulses and defibrillation or cardioversion shocks, as well as a sensing module for monitoring the patient's heart rhythm.

Leads <NUM>, <NUM>, <NUM> may also include elongated electrodes <NUM>, <NUM>, <NUM>, respectively, which may take the form of a coil. IMD <NUM> may deliver defibrillation shocks to heart <NUM> via any combination of elongated electrodes <NUM>, <NUM>, <NUM>, and housing electrode <NUM>. Electrodes <NUM>, <NUM>, <NUM>, <NUM> may also be used to deliver cardioversion pulses to heart <NUM>. Electrodes <NUM>, <NUM>, <NUM> may be fabricated from any suitable electrically conductive material, such as, but not limited to, platinum, platinum alloy or other materials known to be usable in implantable defibrillation electrodes.

Pressure sensor <NUM> may be coupled to one or more coiled conductors within lead <NUM>. In <FIG>, pressure sensor <NUM> is located more distally on lead <NUM> than elongated electrode <NUM>. In other examples, pressure sensor <NUM> may be positioned more proximally than elongated electrode <NUM>, rather than distal to electrode <NUM>. Further, pressure sensor <NUM> may be coupled to another one of the leads <NUM>, <NUM> in other examples, or to a lead other than leads <NUM>, <NUM>, <NUM> carrying stimulation and sense electrodes. In addition, in some examples, pressure sensor <NUM> may be self-contained device that is implanted within heart <NUM>, such as within the septum separating right ventricle <NUM> from left ventricle <NUM>, or the septum separating right atrium <NUM> from left atrium <NUM>. In such an example, pressure sensor <NUM> may wirelessly communicate with IMD <NUM>.

<FIG> shows IMD <NUM> coupled to leads <NUM>, <NUM>, <NUM>, <NUM>. Right atrial (RA) lead <NUM> may extend through one or more veins and the vena cava, and into the right atrium <NUM> of heart <NUM>. RA lead <NUM> may be connected to triple chamber IMD <NUM>, e.g., using a Y-adaptor. IMD <NUM> may be used for cardiac rhythm therapy and defibrillation or cardioversion therapy (CRT-D). RA lead <NUM> may include electrodes that are the same or similar to the electrodes of lead <NUM>, <NUM>, <NUM>, such as ring electrodes <NUM>, <NUM> and <NUM>, extendable helix tip electrodes <NUM>, <NUM> and <NUM>, and/or elongated electrodes <NUM>, <NUM>, <NUM>, in the form of a coil.

The configuration of therapy system <NUM> illustrated in <FIG> are merely examples. In other examples, a therapy system may include epicardial leads and/or patch electrodes instead of or in addition to the transvenous leads <NUM>, <NUM>, <NUM> and/or cardiac conduction system pacing lead <NUM> illustrated in <FIG> or other configurations shown or described herein or incorporated by reference. Further, IMD <NUM> need not be implanted within patient <NUM>. In examples in which IMD <NUM> is not implanted in patient <NUM>, IMD <NUM> may deliver defibrillation shocks and other therapies to heart <NUM> via percutaneous leads that extend through the skin of patient <NUM> to a variety of positions within or outside of heart <NUM>.

In other examples of therapy systems that provide electrical stimulation therapy to heart <NUM>, such therapy systems may include any suitable number of leads coupled to IMD <NUM>, and each of the leads may extend to any location within or proximate to heart <NUM>. For example, other examples of therapy systems may include three transvenous leads located as illustrated in <FIG>, and an additional lead located within or proximate to left atrium <NUM> (<FIG>). As another example, other examples of therapy systems may include a single lead that extends from IMD <NUM> into right atrium <NUM> or right ventricle <NUM>, or two leads that extend into a respective one of right ventricle <NUM> and right atrium <NUM>. An example of this type of therapy system is shown in <FIG>. If four leads are required for therapy delivery, an IS-<NUM> connector may be used in conjunction with Y-adaptor <NUM> extending from the RA port of the connector. The Y-adaptor allows two separate leads-e.g., right atrial lead and the bundle pacing bundle lead--to extend from the two separate legs of the "Y shape" while the single leg is inserted into connector block <NUM> on IMD <NUM>.

<FIG> is a conceptual diagram illustrating another example of therapy system <NUM>. Therapy system <NUM> shown in <FIG> may be useful for providing defibrillation and pacing pulses to heart <NUM>. Therapy system <NUM> is similar to therapy system <NUM> of <FIG> or <FIG>, but includes two leads <NUM>, <NUM>, rather than three leads. Therapy system <NUM> may utilize an IMD <NUM> configured to deliver, or perform, dual chamber pacing. Leads <NUM>, <NUM> are implanted within right ventricle <NUM> and right atrium <NUM> to pace one or more portions of the cardiac conduction system such as the His bundle or one or both bundle branches, respectively.

Cardiac conduction system pacing lead <NUM> may be in the form of a helix (also referred to as a helical electrode) may be positioned proximate to, near, adjacent to, or in, area or portions of the cardiac conduction system such as, e.g., ventricular septum, triangle of Koch, the His bundle, left right bundle branch tissues, and/or right bundle branch tissue. Cardiac conduction system pacing lead <NUM> may be configured as a bipolar lead or as a quadripolar lead that may be used with a pacemaker device, a CRT-P device or a CRT-ICD.

<FIG> is a functional block diagram of one example configuration of IMD <NUM>, which includes processor <NUM>, memory <NUM>, stimulation generator <NUM> (e.g., electrical pulse generator or signal generating circuit), sensing module <NUM> (e.g., sensing circuit), telemetry module <NUM>, and power source <NUM>. One or more components of IMD <NUM>, such as processor <NUM>, may be contained within a housing of IMD <NUM> (e.g., within a housing of a pacemaker). Telemetry module <NUM>, sensing module <NUM>, or both telemetry module <NUM> and sensing module <NUM> may be included in a communication interface. Memory <NUM> includes computer-readable instructions that, when executed by processor <NUM>, cause IMD <NUM> and processor <NUM> to perform various functions attributed to IMD <NUM> and processor <NUM> herein. Memory <NUM> may include any volatile, non-volatile, magnetic, optical, or electrical media, such as a random-access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically-erasable programmable ROM (EEPROM), flash memory, or any other digital media.

Processor <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 integrated logic circuitry. In some examples, processor <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 processor <NUM> herein may be embodied as software, firmware, hardware or any combination thereof. Processor <NUM> controls stimulation generator <NUM> to deliver stimulation therapy to heart <NUM> according to a selected one or more of therapy programs (e.g., optimization of the AV delay, VV delay, VV delay etc.), which may be stored in memory <NUM>. Specifically, processor <NUM> may control stimulation generator <NUM> to deliver electrical pulses with amplitudes, pulse widths, frequency, or electrode polarities specified by the selected one or more therapy programs.

In some embodiments, RA lead <NUM> may be operably coupled to electrode <NUM>, which may be used to monitor or pace the RA. Stimulation generator <NUM> may be electrically coupled to electrodes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, e.g., via conductors of respective lead <NUM>, <NUM>, <NUM>, <NUM> or, in the case of housing electrode <NUM>, via an electrical conductor disposed within housing <NUM> of IMD <NUM>. Stimulation generator <NUM> may be configured to generate and deliver electrical stimulation therapy to heart <NUM>. For example, stimulation generator <NUM> may deliver defibrillation shocks to heart <NUM> via at least two of electrodes <NUM>, <NUM>, <NUM>, <NUM>. Stimulation generator <NUM> may deliver pacing pulses via ring electrodes <NUM>, <NUM>, <NUM> coupled to leads <NUM>, <NUM>, <NUM>, respectively, and/or helical electrodes <NUM>, <NUM>, and <NUM> of leads <NUM>, <NUM>, or <NUM>, respectively. Cardiac conduction system pacing therapy can be delivered through cardiac conduction system lead <NUM> that is connected to an atrial, RV, or LV connection port of connector block <NUM>. In some embodiments, the cardiac conduction system pacing therapy can be delivered through leads <NUM> and/or <NUM>. In some examples, stimulation generator <NUM> delivers pacing, cardioversion, or defibrillation stimulation in the form of electrical pulses. In other examples, stimulation generator <NUM> may deliver one or more of these types of stimulation in the form of other signals, such as sine waves, square waves, or other substantially continuous time signals.

Stimulation generator <NUM> may include a switch module and processor <NUM> may use the switch module to select, e.g., via a data/address bus, which of the available electrodes are used to deliver defibrillation shocks or pacing pulses. The switch module may include a switch array, switch matrix, multiplexer, or any other type of switching device suitable to selectively couple stimulation energy to selected electrodes.

Sensing module <NUM> monitors signals from at least one of electrodes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM> in order to monitor electrical activity of heart <NUM>, e.g., via electrical signals, such as electrocardiogram (ECG) signals and/or electrograms (EGMs). Sensing module <NUM> may also include a switch module to select which of the available electrodes are used to sense the heart activity. In some examples, processor <NUM> may select the electrodes that function as sense electrodes via the switch module within sensing module <NUM>, e.g., by providing signals via a data/address bus. In some examples, sensing module <NUM> includes one or more sensing channels, each of which may include an amplifier. In response to the signals from processor <NUM>, the switch module may couple the outputs from the selected electrodes to one of the sensing channels.

In some examples, one channel of sensing module <NUM> may include an R-wave amplifier that receives signals from electrodes <NUM>, <NUM>, which are used for pacing and sensing in right ventricle <NUM> of heart <NUM>. Another channel may include another R-wave amplifier that receives signals from electrodes <NUM>, <NUM>, which are used for pacing and sensing proximate to left ventricle <NUM> of heart <NUM>. In some examples, the R-wave amplifiers may take the form of an automatic gain-controlled amplifier that provides an adjustable sensing threshold as a function of the measured R-wave amplitude of the heart rhythm.

In addition, in some examples, one channel of sensing module <NUM> may include a P-wave amplifier that receives signals from electrodes <NUM>, <NUM>, which are used for pacing and sensing in right atrium <NUM> of heart <NUM>. In some examples, the P-wave amplifier may take the form of an automatic gain-controlled amplifier that provides an adjustable sensing threshold as a function of the measured P-wave amplitude of the heart rhythm. Examples of R-wave and P-wave amplifiers are described in <CIT> and is entitled, "APPARATUS FOR MONITORING ELECTRICAL PHYSIOLOGIC SIGNALS. " Other amplifiers may also be used. Furthermore, in some examples, one or more of the sensing channels of sensing module <NUM> may be selectively coupled to housing electrode <NUM>, or elongated electrodes <NUM>, <NUM>, or <NUM>, with or instead of one or more of electrodes <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM>, e.g., for unipolar sensing of R-waves or P-waves in any of chambers <NUM>, <NUM>, or <NUM> of heart <NUM>.

In some examples, sensing module <NUM> includes a channel that includes an amplifier with a relatively wider pass band than the R-wave or P-wave amplifiers or a high-resolution amplifier with relatively narrow-pass band for His bundle or bundle branch potential recording. Signals from the selected sensing electrodes that are selected for coupling to this wide-band amplifier may be provided to a multiplexer, and thereafter converted to multi-bit digital signals by an analog-to-digital converter for storage in memory <NUM> as an electrogram (EGM). In some examples, the storage of such EGMs in memory <NUM> may be under the control of a direct memory access circuit. Processor <NUM> may employ digital signal analysis techniques to characterize the digitized signals stored in memory <NUM> to detect and classify the patient's heart rhythm from the electrical signals. Processor <NUM> may detect and classify the heart rhythm of patient <NUM> by employing any of the numerous signal processing methodologies known in the art.

If IMD <NUM> is configured to generate and deliver pacing pulses to heart <NUM>, processor <NUM> may include pacer timing and control module, which may be embodied as hardware, firmware, software, or any combination thereof. The pacer timing and control module may include a dedicated hardware circuit, such as an ASIC, separate from other processor <NUM> components, such as a microprocessor, or a software module executed by a component of processor <NUM>, which may be a microprocessor or ASIC. The pacer timing and control module may include programmable counters which control the basic time intervals associated with DDD, VVI, DVI, VDD, AAI, DDI, DDDR, VVIR, DVIR, VDDR, AAIR, DDIR and other modes of single and dual chamber pacing. In the aforementioned pacing modes, "D" may indicate dual chamber, "V" may indicate a ventricle, "I" may indicate inhibited pacing (e.g., no pacing), and "A" may indicate an atrium. The first letter in the pacing mode may indicate the chamber that is paced, the second letter may indicate the chamber in which an electrical signal is sensed, and the third letter may indicate the chamber in which the response to sensing is provided.

Intervals defined by the pacer timing and control module may include atrial and ventricular pacing escape intervals, refractory periods during which sensed P-waves and R-waves are ineffective to restart timing of the escape intervals, and the pulse widths of the pacing pulses. As another example, the pace timing and control module may define a blanking time period and provide signals from sensing module <NUM> to blank one or more channels, e.g., amplifiers, for a period during and after delivery of electrical stimulation to heart <NUM>. The durations of these intervals may be determined by processor <NUM> in response to stored data in memory <NUM>. The pacer timing and control module may also determine the amplitude of the cardiac pacing pulses.

During pacing, escape interval counters within the pacer timing/control module may be reset upon sensing of R-waves and P-waves. Stimulation generator <NUM> may include pacer output circuits that are coupled, e.g., selectively by a switching module, to any combination of electrodes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> appropriate for delivery of a bipolar or unipolar pacing pulse to one of the chambers of heart <NUM>. Processor <NUM> may reset the escape interval counters upon the generation of pacing pulses by stimulation generator <NUM>, and thereby control the basic timing of cardiac pacing functions, including anti-tachyarrhythmia pacing.

In some examples, processor <NUM> may operate as an interrupt driven device, and is responsive to interrupts from pacer timing and control module, where the interrupts may correspond to the occurrences of sensed P-waves and R-waves and the generation of cardiac pacing pulses. Any necessary mathematical calculations to be performed by processor <NUM> and any updating of the values or intervals controlled by the pacer timing and control module of processor <NUM> may take place following such interrupts. A portion of memory <NUM> may be configured as a plurality of recirculating buffers, capable of holding series of measured intervals, which may be analyzed by processor <NUM> in response to the occurrence of a pace or sense interrupt to determine whether the patient's heart <NUM> is presently exhibiting atrial or ventricular tachyarrhythmia.

Telemetry module <NUM> includes any suitable hardware, firmware, software or any combination thereof for communicating with another device, such as programmer <NUM> (<FIG>). Under the control of processor <NUM>, telemetry module <NUM> may receive downlink telemetry from and send uplink telemetry to programmer <NUM> with the aid of an antenna, which may be internal and/or external. Processor <NUM> may provide the data to be uplinked to programmer <NUM> and the control signals for the telemetry circuit within telemetry module <NUM>, e.g., via an address/data bus. In some examples, telemetry module <NUM> may provide received data to processor <NUM> via a multiplexer.

The various components of IMD <NUM> are coupled to power source <NUM>, which may include a rechargeable or non-rechargeable battery. A non-rechargeable battery may be selected to last for several years, while a rechargeable battery may be inductively charged from an external device, e.g., on a daily or weekly basis.

The illustrative devices and methods described herein may provide adaptive cardiac conduction system pacing therapy. The illustrative adaptive cardiac conduction system pacing therapy may provide configuration of the timing of the cardiac conduction system pacing as well as timing for traditional left ventricular pacing when used in conjunction with the cardiac conduction system pacing therapy. Additionally, the illustrative adaptive cardiac conduction pacing therapy may also provide switching from cardiac conduction system pacing therapy only to a combination of cardiac conduction system pacing therapy and traditional left ventricular pacing therapy.

An illustrative method <NUM> of adaptive cardiac conduction system pacing therapy that may be utilized by the devices of <FIG> is depicted in <FIG>. As shown, the method <NUM> may determine a paced AV delay <NUM> for use in delivery of cardiac conduction system pacing therapy using the cardiac conduction system electrode. The paced AV delay is a time period between a sensed or paced atrial event (e.g., depolarization of the atrium, p-wave in an electrocardiogram, etc.) and delivery of cardiac conduction system pacing therapy (e.g., delivery of a pacing pulse to the cardiac conduction system).

The paced AV delay may be determined using various illustrative processes. One illustrative process of determining AV delay <NUM> of the method of <FIG> is depicted in <FIG>. The process <NUM> of <FIG> may include measuring an intrinsic AV delay using a cardiac conduction system electrode <NUM>. The cardiac conduction system electrode is the electrode configured to deliver cardiac conduction system (for example, an electrode positioned on cardiac conduction system lead <NUM> as described herein). The intrinsic AV delay is a time period between a sensed intrinsic, or naturally-occurring, atrial event (e.g., depolarization of the atrium, p-wave in an electrocardiogram, etc.) and a sensed intrinsic, or naturally-occurring, ventricular event (e.g., depolarization of the left ventricle or both ventricles, r-wave in an electrocardiogram, etc.).

The measured intrinsic AV delay may be used when testing various paced AV delays. For example, the process <NUM> may include delivering cardiac conduction system pacing therapy to the patient's cardiac conduction system using the cardiac conduction system electrode at a plurality of different paced AV delays that are less than the intrinsic AV delay <NUM>. In this example, the plurality of different paced AV delays may be based on various percentages of the intrinsic AV delay. Each various percentage may be referred to an AV delay percentage. For instance, the plurality of different paced AV delays may be between about <NUM>% of the intrinsic AV delay and about <NUM>% of the intrinsic AV delay. For example, the plurality of different paced AV delays may include a range of paced AV delays based on different AV delay percentages spaced <NUM>% or more apart from one another. In at least one embodiment, the plurality of different paced AV delays may include <NUM>% of the intrinsic AV delay, <NUM>% of the intrinsic AV delay, <NUM>% of the intrinsic AV delay, <NUM>% of the intrinsic AV delay, <NUM>% of the intrinsic AV delay, <NUM>% of the intrinsic AV delay, and <NUM>% of the intrinsic AV delay.

The cardiac conduction system pacing therapy may be delivered for one or a plurality of cardiac cycles at each different paced AV delay (or each different AV delay percentage) to, e.g., provide an appropriate sample size of data to evaluate. The process <NUM> may further monitor far-field electrical activity <NUM> during delivery of the cardiac conduction system pacing therapy. The far-field electrical activity may be monitored by any electrode positioned outside of the cardiac conduction system pacing therapy area of interest. In at least one embodiment, the far-field electrical activity may be monitored by a ring electrode positioned on a left ventricular lead located in the coronary sinus. In at least one embodiment, the far-field electrical activity may be monitored by an external electrode disposed on the skin of the patient's torso.

Then, a paced AV delay of the plurality of different paced AV delays may be selected <NUM> based on the far-field electrical activity monitored during the delivery of cardiac conduction system pacing therapy at the plurality of different paced AV delays. More specifically, one or more metrics may be derived or determined from the far-field electrical activity that may be used to determine the most effective or optimal paced AV delay for the cardiac conduction system pacing therapy. In at least one embodiment, a time period between the delivery of the cardiac conduction system pacing therapy and an end of ventricular depolarization (e.g., QRS offset) may be determined for each of the plurality of different paced AV delays. Then, the paced AV delay or AV delay percentage providing the shortest time period between the delivery of the cardiac conduction system pacing therapy and an end of ventricular depolarization may be selected.

As noted herein, it is to be understood that the selected paced AV delay may be percentage of the intrinsic AV delay, which may be referred to as an AV delay percentage. For example, the selected AV delay percentage may be <NUM>% of the intrinsic AV delay. In this way, the intrinsic AV delay may be measured periodically by halting any cardiac pacing therapy, and the paced AV delay may be adjusted accordingly according the selected AV delay percentage.

Thus, the process <NUM> may result in a selected AV delay for delivery of cardiac conduction system pacing therapy. The method <NUM> may further include determining a VV delay for cardiac conduction system and left ventricular pacing therapy <NUM>. The VV delay may be the time period between the delivery of the cardiac conduction system pacing therapy and the delivery of the left ventricular pacing therapy.

The paced VV delay may be determined <NUM> using various illustrative processes. One illustrative process of determining VV delay <NUM> of the method of <FIG> is depicted in <FIG>. The process <NUM> of <FIG> may deliver cardiac conduction system pacing therapy to the patient's cardiac conduction system at the selected AV delay and delivering left ventricular pacing therapy at a plurality of different paced VV delays <NUM>. In this example, the plurality of different paced VV delays may include a range of different time values. For instance, the plurality of different paced VV delays may be between about -<NUM> milliseconds (ms) to about <NUM>. In other words, the left ventricular pacing may be delivered between about <NUM> before the delivery of the cardiac conduction system pacing therapy to about <NUM> after the delivery of the cardiac conduction system pacing therapy. For example, the plurality of different paced VV delays may include a range of paced VV delays spaced apart from one another by a selected interval such as <NUM>. In at least one embodiment, the plurality of different paced VV delays may include -<NUM>, -<NUM>, -<NUM>, <NUM>, <NUM>, <NUM>, and <NUM>.

Further, the cardiac conduction system pacing therapy and left ventricular pacing therapy may be delivered <NUM> for one or a plurality of cardiac cycles at each different paced VV delay to, e.g., provide an appropriate sample size of data to evaluate. The process <NUM> may further monitoring far-field electrical activity <NUM> during delivery of the cardiac conduction system and left ventricular pacing therapy. The far-field electrical activity may be monitored by any electrode positioned outside of the cardiac conduction system pacing therapy area of interest. In at least one embodiment, the far-field electrical activity may be monitored by a ring electrode positioned on a left ventricular lead located in the coronary sinus. In at least one embodiment, the far-field electrical activity may be monitored by an external electrode disposed on the skin of the patient's torso.

Then, a paced VV delay of the plurality of different paced VV delays may be selected <NUM> based on the far-field electrical activity monitored during the delivery of cardiac conduction system pacing therapy and left ventricular pacing therapy at the plurality of different paced VV delays. More specifically, one or more metrics may be derived or determined from the far-field electrical activity that may be used to determine the most effective or optimal paced VV delay for the cardiac conduction system and left ventricular pacing therapy. In at least one embodiment, the time period between the earliest pacing (e.g., either cardiac conduction system pacing therapy or left ventricular pacing therapy depending on the present VV delay) and an end of ventricular depolarization (e.g., QRS duration, the time period between QRS onset and QRS offset, etc.) may be determined for each of the plurality of different paced VV delays. Then, the paced VV delay providing the shortest, or narrowest, time period between pacing and the end of ventricular depolarization (e.g., QRS duration) may be selected.

Thus, the process <NUM> may result in a selected VV delay for delivery of cardiac conduction system and left ventricular pacing therapy when used in combination. As a result, the method <NUM> may then be configured to deliver cardiac conduction system pacing therapy and combined cardiac conduction system and left ventricular pacing therapy, if needed. Thus, the method <NUM> may initiate or begin delivery of cardiac conduction system pacing therapy alone <NUM> and monitoring local electrical activity of the patient using a left ventricular electrode <NUM> during the delivery of cardiac conduction system pacing therapy. The local electrical activity may be used to determine whether to switch to combined cardiac conduction system and left ventricular pacing therapy <NUM>. For example, various metrics may be derived or generated from the local electrical activity, which may then be used to determine whether to switch to combined cardiac conduction system and left ventricular pacing therapy <NUM>.

An illustrative process <NUM> of switching to combined cardiac conduction system and left ventricular pacing therapy of the method of <FIG> is depicted in <FIG>. The process <NUM> includes determining an interval between the delivery of cardiac conduction system pacing therapy and a peak in the local monitored local activity <NUM> and then comparing the interval to a threshold value <NUM>. The threshold value may be between about <NUM> and about <NUM>. In at least one embodiment, the threshold value is <NUM>. In other embodiments, the threshold value may be greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, etc. and/or less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, etc. If the measured interval is greater than or equal to the threshold value, then it may be determined that the cardiac conduction system pacing therapy may be less than optimal or most effective, and thus may be adjusted and/or may benefit from the additional of left ventricular pacing therapy. If the measured interval is less than the threshold value, then it may be determined that the cardiac conduction system pacing therapy is effective and the process may return to monitoring the local electrical activity <NUM>.

As shown in process <NUM> of <FIG>, the cardiac conduction system pacing therapy may be adjusted <NUM> if the interval is greater than or equal to the threshold. For example, the cardiac conduction system pacing output may be increased (e.g., amplitude or voltage may be increased, pacing burst lengthened, pacing frequency increased, number of bursts per pulse increased, etc.). Further, for example, the electrode vector of cardiac conduction system pacing therapy may be changed (e.g., increase the number of electrodes used to deliver cardiac conduction system pacing therapy, change to different electrodes or a different electrode combination being used to deliver cardiac conduction system pacing therapy). Simultaneously, the process <NUM> may continue monitoring the local electrical activity <NUM> and comparing the interval to the threshold <NUM>, and if the interval becomes less than the threshold, then the process <NUM> may return to delivering cardiac conduction system pacing therapy at the newly-adjusted pacing output and monitoring local electrical activity.

If adjustment of a cardiac conduction system pacing therapy output parameter does not result in the interval being less than the threshold, the process <NUM> may continue looping to adjust the output parameter until the adjustments are exhausted <NUM>. The pacing output parameter adjustments may be exhausted when the pacing output cannot be further adjusted or increased. In other words, the cardiac conduction system pacing output may be exhausted when it is at its upper, or maximum, limit. When the adjustments are exhausted, the process <NUM> may proceed to delivering combined cardiac conduction system and left ventricular pacing therapy <NUM> according to the previously-determined AV delay and VV delay. Thus, the process <NUM> may switch from cardiac conduction system pacing therapy only to cardiac conduction system pacing therapy being used in conjunction with left ventricular pacing therapy.

The method <NUM> further includes adjusting the paced AV delay <NUM>, e.g., periodically, based on measuring the intrinsic AV delay in the absence of delivery of pacing therapy and using the previously-determined AV delay percentage to determine the new paced AV delay.

The illustrative devices and methods described herein may be further configured to determine whether cardiac conduction system pacing therapy being delivered to the patient's cardiac conduction system has selectively or non-selectively captured the patient's cardiac conduction system. Cardiac conduction system pacing therapy having selective capture of the cardiac conduction system may be defined as pacing therapy that delivers pacing therapy only to the cardiac conduction system and that does not deliver pacing therapy directly to myocardial or muscular cardiac tissue. In other words, selective cardiac conduction system pacing therapy paces the cardiac conduction system alone. Cardiac conduction system pacing therapy having non-selective capture of the cardiac conduction system may be defined as pacing therapy that delivers pacing therapy to the cardiac conduction system and also directly to the myocardial or muscular cardiac tissue. In other words, non-selective cardiac conduction system pacing therapy paces both the cardiac conduction system and myocardial or muscular cardiac tissue. The illustrative devices and methods, using a near-field signal, may be able to determine whether the delivered cardiac conduction system pacing therapy is selective or non-selective, which may be helpful in delivery of effective cardiac therapy to a patient.

An illustrative method <NUM> of determining whether cardiac conduction system pacing therapy has selectively captured the cardiac conduction system is depicted in <FIG>. The method <NUM> may include delivering cardiac conduction system pacing therapy <NUM> using, for example, one of the illustrative devices described herein with respect to <FIG>, and monitoring near-field electrical activity <NUM> during delivery of the cardiac conduction system pacing therapy. The near-field electrical activity may be monitored via one or more implantable electrodes that are located proximate the left bundle branch.

The near-field electrical activity <NUM> may be monitored for a sensing time period following the delivery of the cardiac conduction system pacing therapy. The sensing time period may be between about <NUM> and about <NUM>. In at least one embodiment, the sensing time period is <NUM>. In other embodiments, the sensing time period may be greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, etc. and/or less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, etc..

Additionally, the sensing time period may follow a blanking time period following the delivery of the cardiac conduction system pacing therapy. The blanking time period may be between about <NUM> and about <NUM>. In at least one embodiment, the blanking time period is <NUM>. In other embodiments, the blanking time period may be greater than or equal to <NUM>, greater than or equal to <NUM>, greater than or equal to <NUM>, etc. and/or less than or equal to <NUM>, less than or equal to <NUM>, less than or equal to <NUM>, etc..

In other words, following the delivery of the cardiac conduction system pacing therapy, a blanking time period, which may be <NUM>, may delay the measuring or monitoring of the near-field electrical activity that may then be measured or monitored for a sensing time period, which may be <NUM>.

A derivative signal may be generated <NUM> based on the monitored near-field electrical activity during the sensing time period. The derivative signal may be described as computing a derivative of the near-field electrical signal (e.g., electrocardiogram) by taking differences of successive samples. In at least one embodiment, a <NUM>-point derivative of the near-field signal is generated, e.g., so as to provide a smoother derivative signal and mute the chances of large changes due to local artifacts.

The method <NUM> may then determine whether the pacing therapy has selective or non-selective capture of the cardiac conduction system based on the derivative signal <NUM>. Determining whether the pacing therapy has selective or non-selective capture of the cardiac conduction system based on the derivative signal may be performed, or executed, a variety of different ways and using a variety of different metrics. An illustrative process <NUM> of determining whether cardiac conduction system pacing therapy has selectively or non-selectively captured the cardiac conduction system is depicted in <FIG>.

As shown in <FIG>, a number of change events within the derivative signal over the sensing period may be determined <NUM> and then compared to a change event threshold <NUM>. In this example, the change event threshold is <NUM>. Thus, if more than <NUM> change events occur within the derivative signal over the sensing period, then it may be determined that the cardiac conduction system pacing therapy has selective capture <NUM>. Conversely, if less than or equal to <NUM> change events occur within the derivative signal over the sensing period, then it may be determined that the cardiac conduction system pacing therapy has non-selective capture <NUM>. Although the change event threshold in this example is <NUM>, the change event threshold may be less than <NUM> or greater than <NUM>. For example, the change event threshold may be between about <NUM> and about <NUM>, depending on the length of the sensing time period, among other things.

A change event may generally be described as an event where the derivative signal changes sign from positive-to-negative or positive-to-negative. For example, a minimum change threshold may be used such as, e.g., <NUM> Volts. Thus, a change event may be counted or determined for every sign change that is greater than <NUM> Volt within the derivative signal over the sensing period. Although the minimum change threshold in this example is <NUM> Volts, the minimum change threshold may be less than <NUM> Volts or greater than <NUM> Volts. For example, the minimum change threshold may be between about <NUM> Volts and about <NUM> Volts.

A left bunch branch electrocardiogram <NUM> showing selective cardiac conduction system capture is depicted in <FIG>. As shown, more than <NUM> change events have occurred within the sensing time period <NUM> following the cardiac conduction system pacing therapy <NUM> thereby indicating selective capture of the cardiac conduction system. A left bunch branch electrocardiogram <NUM> showing non-selective cardiac conduction system capture is depicted in <FIG>. As shown, less than or equal to <NUM> change events have occurred within the sensing time period <NUM> following the cardiac conduction system pacing therapy <NUM> thereby indicating non-selective capture of the cardiac conduction system.

Various examples have been described. These and other examples are within the scope of the following claims. For example, a single chamber, dual chamber, or triple chamber pacemakers (e.g., CRT-P) or ICDs (e.g., CRT-D) devices can be used to implement the illustrative methods described herein.

This disclosure has been provided with reference to illustrative embodiments and examples and is not meant to be construed in a limiting sense. As described previously, one skilled in the art will recognize that other various illustrative applications may use the techniques as described herein to take advantage of the beneficial characteristics of the devices and methods described herein. Various modifications of the illustrative embodiments and examples will be apparent upon reference to this description.

The terms "coupled" or "connected" refer to elements being attached to each other either directly (in direct contact with each other) or indirectly (having one or more elements between and attaching the two elements). Either term may be modified by "operatively" and "operably," which may be used interchangeably, to describe that the coupling or connection is configured to allow the components to interact to carry out at least some functionality (for example, a mobile user device may be operatively coupled to a cellular network transmit data to or receive data therefrom).

As used herein, "have," "having," "include," "including," "comprise," "comprising" or the like are used in their open-ended sense, and generally mean "including, but not limited to. " It will be understood that "consisting essentially of," "consisting of," and the like are subsumed in "comprising," and the like.

The term "and/or" means one or all of the listed elements or a combination of at least two of the listed elements.

Claim 1:
An implantable medical device comprising:
a plurality of implantable electrodes to sense and pace a patient's heart, wherein the plurality of electrodes comprise:
a left ventricular electrode (<NUM>, <NUM>) positionable proximate the patient's left ventricle; and
a cardiac conduction system electrode (<NUM>) positionable proximate a portion of the patient's cardiac conduction system; and
a computing apparatus comprising processing circuitry, the computing apparatus operably coupled to the plurality of implantable electrodes, wherein the computing apparatus is configured to:
initiate delivery of cardiac conduction system pacing therapy to the patient's cardiac conduction system using the cardiac conduction system electrode;
monitor local electrical activity of the patient using the left ventricular electrode during the delivery of cardiac conduction system pacing therapy using the cardiac conduction system electrode; and
switch to delivery of both cardiac conduction system pacing therapy to the patient's cardiac conduction system using the cardiac conduction system electrode and left ventricular pacing therapy to the patient's left ventricle using the left ventricular electrode in response to the monitored local electrical activity.