Biatrial engagement

Abstract

Engagement of both atria by atrial pacing therapy is determined using one or more metrics based on monitored external electrical activity. For instance, external electrical activity may be monitored during the delivery of atrial pacing therapy, right and left atrial components may be generated based on the monitored external electrical activity, and one more metrics may be generated based on the right and left atrial components. The one or more metrics may then be used to determine if the atrial pacing therapy has biatrial engagement.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from U.S. Provisional Patent Application 63 / 612,719 filed 20 December 2023, the entire content of which is incorporated herein by reference.BIATRIAL ENGAGEMENT

[0002] The disclosure herein relates to systems and methods for use in determining biatrial engagement, or engagement of both atria, by cardiac therapy, and more specifically, for example, engagement of the Bachmann’s Bundle by cardiac conduction system pacing therapy.

[0003] Patients with atrial dyssynchrony often have wider P-waves and slower atrial conduction than healthy patients, which may result in delayed atrial kick and lessened contribution of atrial kick to filling and can compromise ventricular function (e.g., heart failure). Atrial dyssynchrony may also be a cause for atrial arrhythmias and atrial fibrillation. Atrial pacing therapy may help restore atrial synchrony and lead to better outcomes in these patients including bettering heart failure symptoms and potentially reducing burden of atrial arrhythmias.SUMMARY

[0004] The techniques of this disclosure generally relate to systems and methods for guiding implantation of one or more pacing electrodes carried by a lead or part of a leadless implantable medical device into the right atria to engage both atria so as to deliver pacing therapy to both atria. In one embodiment, the system and methods are configured to assist, or guide, implantation of one or more electrodes in or near the Bachmann’s bundle (also called the Bachmann bundle or the interatrial tract) to deliver pacing therapy thereto (e.g., cardiac conduction system pacing therapy). In the heart's conduction system, the Bachmann's bundle is a branch of the anterior intemodal tract that resides on the inner wall of the left atrium and is a broad band of cardiac muscle that passes from the right atrium, between the superior venacava and the ascending aorta. Bachmann's bundle is considered the preferential path for electrical activation of the left atrium during normal sinus rhythm and is therefore considered to be part of the “atrial conduction system” of the heart. When the Bachmann's bundle is sufficiently captured by cardiac conduction system pacing therapy, the pacing may provide more simultaneous right atrial and left atrial activation. However, while Bachmann’s bundle pacing may provide atrial cardiac physiological pacing, it may be difficult to accurately target the Bachmann's bundle, for example, because there is not a universally recognized landmark for guiding implantation. In other words, without sufficient targeting methods, the benefits of implanting pacing at the Bachmann's bundle may not be fully realized. Additionally, the illustrative systems and methods described herein may be utilized to configure atrial pacing therapy by, for example, adjusting one or more paced settings to most effectively engage both atria. Still further, the illustrative systems and methods described herein may be utilized to evaluate atrial pacing therapy being delivered to a patient after implantation and configuration thereof to, e.g., confirm that such therapy is still effectively engaging both atria.

[0005] In other words, the present disclosure provides systems and methods for determining biatrial engagement by one or more electrodes, and in at least in one embodiment, systems and methods for determining biatrial engagement of the Bachmann's bundle (e.g., by one or more electrodes implanted at or near the Bachmann's bundle).

[0006] In one embodiment, an illustrative system for implanting an atrial pacing lead for delivery of a cardiac pacing therapy to both atria includes at least one external electrode configured to be positioned proximate a patient’s skin to sense external electrical activity, and a computing apparatus including processing circuitry and coupled to the at least one external electrode, the computing apparatus configured to initiate delivery of atrial pacing therapy at a target site to deliver cardiac pacing therapy to both atria, monitor external electrical activity using the at least one external electrode during the delivery of the atrial pacing therapy, generate a right atrial component representative of right atrial activation and a left atrial component representative of left atrial activation based on the external electrical activity monitored during the delivery of the atrial pacing therapy, generate at least one metric based on the right atrial component and the left atrial component, and determine engagement of both atria by the atrial pacing therapy delivered to the target site based on the at least one metric.

[0007] In one embodiment, an illustrative method of implanting an atrial pacing lead for delivery of a cardiac pacing therapy to both atria includes initiating delivery of atrial pacingtherapy at a target site to deliver cardiac pacing therapy to both atria, monitoring external electrical activity using at least one external electrode during the delivery of the atrial pacing therapy, generating a right atrial component representative of right atrial activation and a left atrial component representative of left atrial activation based on the external electrical activity monitored during the delivery of the atrial pacing therapy, generating at least one metric based on the right atrial component and the left atrial component, and determining engagement of both atria by the atrial pacing therapy delivered to the target site based on the at least one metric.

[0008] The details of one or more aspects of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the techniques described in this disclosure will be apparent from the description and drawings, and from the claims.BRIEF DESCRIPTION OF DRAWINGS

[0009] FIG. 1 A is an illustrative implantation system for use in navigating and implanting one or more devices at cardiac therapy sites.

[0010] FIG. IB is a diagram illustrating the ten standard electrode positions used to obtain a twelve-lead ECG measurement using, for example, the system of FIG. 1 A.

[0011] FIG. 1C is a block diagram illustrating the three signal measurements included in Einthoven's triangle of the twelve-lead ECG measurement of FIG. IB.

[0012] FIG. 2 is an illustrative diagram of a method of determining engagement of both atria by atrial pacing therapy.

[0013] FIG. 3 is an illustrative process of generating a right atrial component and a left atrial component based on monitored external electrical activity as in the method of FIG. 2.

[0014] FIG. 4 are illustrative processes of generating metrics based on the right atrial component and the left atrial component as in the method of FIG. 2.

[0015] FIG. 5A is an illustrative graph of external electrical activity monitored from Lead II of a twelve-lead ECG measurement of the system of FIG. 1 A.

[0016] FIG. 5B is the illustrative graph of electrical activity of FIG. 5 A including a right atrial component and a left atrial component derived therefrom and depicting various metrics generated therefrom in accordance with the methods and processes of FIGS. 2-4.

[0017] FIG. 6A is another illustrative graph of external electrical activity monitored from Lead II of a twelve-lead ECG measurement of the system of FIG. 1 A.

[0018] FIG. 6B is the illustrative graph of electrical activity of FIG. 6A including a right atrial component and a left atrial component derived therefrom and depicting various metrics generated therefrom in accordance with the methods and processes of FIGS. 2-4.

[0019] FIG. 7 is an illustrative method for determining one or more metrics for use in determining engagement of both atria by atrial pacing therapy.

[0020] FIG. 8 is a diagram of an illustrative system including an illustrative implantable medical device (IMD).

[0021] FIG. 9 is a diagram of the illustrative IMD of FIG. 8.

[0022] FIG. 10 is a block diagram of an illustrative IMD, e.g., of the systems of FIGS. 8- 9.DETAILED DESCRIPTION

[0023] In the following detailed description of illustrative embodiments, reference is made to the accompanying figures of the drawing which form a part thereof, 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.

[0024] Illustrative systems and devices shall be described with reference to Figures 1-10. 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 systems 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.

[0025] Patients with atrial dyssynchrony may experience wider P-waves and slower atrial conduction than health patients, which may result in delayed atrial kick and a reduction in the contribution of atrial kick to filling of the heart and can compromise ventricular function (e.g., heart failure). Atrial dyssynchrony may also be a cause for atrial arrhythmias and atrial fibrillation. Atrial pacing therapy may be utilized to help restore atrial synchrony and lead tobetter outcomes in these patients including reducing heart failure symptoms and potentially reducing burden of atrial arrhythmias.

[0026] Atrial pacing that uses a single lead in the atrium that targets the atrial septum, and more specifically, in one or more embodiments, the Bachmann's bundle for synchronized atrial activation may be used to treat atrial dyssynchrony. One limitation to the use of such pacing therapy to address atrial dyssynchrony is in finding a target site in the septum, such as the Bachmann’s Bundle. As will be described below, using an implantable lead and one or more external electrodes, the lead can be positioned at or near a target site (e.g., at or near the Bachmann’s bundle) to provide biatrial engagement by cardiac pacing therapy. Another possible pacing therapy for treating atrial dyssynchrony may include multi-site atrial stimulation using two leads, one positioned in the right atrium and the other being positioned within the left atrium. However, implantation of a lead in the left atrium may be challenging and the utilization of multiple leads adds complexity. Thus, atrial pacing that uses a single lead in the atrium that targets the atrial septum, and more specifically, in one or more embodiments, the Bachmann's bundle for synchronized atrial activation may be advantageous over a multi-site atrial stimulation system.

[0027] FIG. 1 A is a diagram illustrating an overview of an implantation system 110 (e.g., image-guided implantation system) for use in implanting a catheter, lead, or other medical device for use in providing cardiac therapy. For example, the system 110 can be used for implanting a lead in the atrial septum such as, for example, at or near the Bachmann's bundle of a patient 114. It should further be noted that the implantation system 110 may be used to navigate any other type of instrument or delivery system, including guide wires, needles, drug delivery systems, cell delivery systems, gene delivery systems and biopsy systems. Moreover, these instruments may be used for cardiac therapy or any other therapy in the body or be used to navigate or map any other regions of the body, such as moving body structures. However, each region of the body poses unique requirements to navigate, as disclosed herein.

[0028] The implantation system 110 can include a controller or computing apparatus 134 having a display 136 and a user interface 138. The computing apparatus 134 provides facilities for displaying on the display 136, saving, digitally manipulating, or printing a hard copy of the received images. The computing apparatus 134 can include at least one processor coupled to at least one memory. The at least one memory can include random access memory and / or other storage such as a hard drive disk. The user interface 138, which may include or be a keyboard, mouse, touch pen, touch screen or other suitable device, may allow aphysician or other user to select one or more metrics and / or reports for viewing. Additionally, the display 136 may be configured to display monitored electrical activity and one or more metrics derived or generated therefrom as will be described further herein in conjunction with FIGS. 2-7.

[0029] The system 110 further includes a navigation probe interface 150 and an electromagnetic catheter 152 as well as any other type of instrument for use in implanting an implantable medical device, such as a lead carrying electrodes or leadless implantable medical device including electrodes, in the atrial septum. The navigation probe interface 150 can include amplifiers, filters and buffers configured to directly interface with sensors included in the distal end 158 of the catheter 152. Alternatively, the catheter 152 may employ a wireless communications channel as opposed to being coupled directly to the navigation probe interface 150.

[0030] The catheter 152, as will be described in detail below, can be equipped with at least one, and generally multiple, localization sensors at or near the distal end 158. The catheter 152 is also generally a steerable catheter that includes a handle at a proximal end and the multiple location sensors at or near the distal end 158 fixed to the catheter body and spaced axially from one another along the distal segment of the catheter 152. The catheter 152, as shown in FIG. 1 A includes four localization sensors at or near the distal end 158. The localization sensors at or near the distal end 158 are generally formed as electromagnetic receiver coils, such that the electromagnetic field generated by a transmitter coil array that induces current in the electromagnetic receiver coils or sensors at or near the distal end 158. The catheter 152 may also be equipped with one or more sensors operable to sense various physiological signals. For example, the catheter 152 may be provided with electrodes for sensing myopotentials or action potentials. An absolute pressure sensor may also be included, as well as other electrode sensors.

[0031] The catheter 152 may also be provided with an open lumen, further discussed herein, to allow the delivery of an implantable medical device. For example, the catheter 152 may be used as a guide catheter for deploying an implantable medical device, such as a cardiac lead or leadless implantable medical device for use in delivering cardiac pacing and / or defibrillation. In some embodiments, the catheter 152 can be used to deploy a cardiac lead or leadless implantable medical device to be implanted into the atrial septum to deliver biatrial cardiac therapy (e.g., at or near the Bachmann’s bundle of the patient 114 to delivery cardiac conduction system pacing therapy thereto).

[0032] The system 110 further includes an electrocardiogram (ECG) device 162, which is attached to the patient 114, via one or more external electrodes 164 (e.g., configured to be positioned adjacent a patient’s skin in various locations as will be described with respect to FIGS. 1B-1C), and in communication with the computing apparatus 134. In some embodiments, the electrocardiogram device 162 can be a twelve-lead electrocardiogram (e.g., a standard twelve-lead electrocardiogram). In some embodiments, the one or more external electrodes 164 can include a Lead II electrode and / or a VI electrode of a standard 12-lead electrocardiogram as will be described further herein with respect to FIGS. 1B-1C.

[0033] To enable navigation, the system 110 is able to detect both the position of the patient's anatomy and the position of the catheter 152 or other surgical instrument. Knowing the location of these two items allows the implantation system 110 to compute and display the position of the catheter 152 in relation to the patient 114.

[0034] FIG. IB is a diagram 166 illustrating the ten standard electrode positions on the patient 114 used to obtain a twelve-lead ECG measurement using, for example, the system of FIG. 1 A. As described herein, the system 110 of FIG. 1 A may utilize a 12-lead electrocardiogram system using the one or more external electrodes 164, and thus, the one or more external electrodes 164 of the system 110 may be positioned in the positions as shown in diagram 166 of FIG. IB. As shown in FIG. IB, electrodes RA, LA, and LL are positioned on a patient's right arm, left arm, and left leg respectively, and a ground is generally placed on the right leg (RL). Further, other electrodes VI through V6 are placed on the patient's chest. Various electrode pairs are used to obtain the standard set of twelve leads included in an ECG measurement.

[0035] Three of the signals measured using twelve-lead ECG measurement are commonly referred to as Lead I, Lead II, and Lead III. These refer to measurements between RA and LA, between RA and LL, and between LA and LL, respectively. These three signal measurements comprise what is called Einthoven's triangle as shown in FIG. 1C. This triangle is commonly used to show the relationship between the measured electrical signals and the lead positions. This can be expressed in equation form as follows Lead II = Lead I + Lead III. This concept is based on Kirchoff s voltage law, wherein the voltage signals as measured between the right to left arm, between left arm to left leg, and between left leg to right arm may be added to obtain a sum of zero if the first point in each pair is considered the voltage reference point. As is evident from the foregoing equation, any one of the signals of Einthoven's triangle may be approximated if the other two signals are known. By extendingthis concept, all of the signals included in the standard 12-lead ECG may be approximated if only two of the signals are known.

[0036] The illustrative systems and methods described herein may be used to provide noninvasive assistance to a user in the evaluation of cardiac therapy such as atrial pacing therapy by use of one or more pacing electrodes configured to deliver pacing therapy to both atria (such as the devices described herein with respect to FIGS. 8-10). For example, the illustrative systems and methods may be configured to measure external electrical activity using one or more external electrodes of a standard 12-lead ECG or the like during the delivery of cardiac therapy using a lead or leadless implantable medical device positioning one or more electrodes in the atrial septum (e.g., near or at the Bachmann’s Bundle so as to deliver cardiac conduction system pacing therapy to the Bachmann’s Bundle thereby engaging or capturing both atria). In one or more embodiments, the illustrative systems and methods may be described as being noninvasive because such systems and methods utilize electrical activity monitored from the exterior of the patient (e.g., the skin) as opposed to measurements using electrodes or probes located on the interior the patient.

[0037] An illustrative method 400 of determining engagement of both atria by atrial pacing therapy is depicted in FIG. 2. In at least one embodiment, the method 400 may be configured to determine a target site to engage the Bachmann’s bundle in a heart of a patient (e.g., the patient 114 in FIG. 1 A). In some embodiments, the method 400 can be implemented (e.g., as instructions) in a memory and executed by a processor of, e.g., the computing apparatus 134 of FIG. 1 A. The method 400 can be used to position a pacing electrode on a lead or leadless implantable medical device in the atrial septum, e.g., at or near the Bachmann’s Bundle of the patient and configure atrial pacing therapy delivered by such pacing electrode.

[0038] The method 400 includes moving the pacing electrode to a target site 402. In some embodiments, the pacing electrode can be included in a lead. In some embodiments, the electrode can be included in a leadless pacemaker. In some embodiments, the lead can be a right atrial lead as will be described further herein with respect to FIGS. 8-10. Further, the pacing electrode can include one or both of a helix electrode and a ring electrode carried on a distal end of a right atrial lead or leadless pacemaker. In some embodiments, a user such as a human practitioner (e.g., a cardiac surgeon) can move the lead and / or pacing electrode using a catheter, such as the catheter 152 in FIG. 1A. In some embodiments, the method 400 can cause a prompt to position the pacing electrode to be displayed to the human practitioner. Forexample, the method 400 can cause a prompt to position the pacing electrode to be displayed at the display 136. In some embodiments, the method 400 can wait a predetermined amount of time for the human practitioner to move the pacing electrode to the target site. The target site can be a location on a cardiac wall of the heart of the patient. More specifically, the target site can be a location on the atrial septum within the right atria of the heart of the patient. It is to be understood that the target site may be a cardiac surface at which a pacing electrode is positioned or implanted into or a location within cardiac tissue such as the atrial septum.

[0039] After the electrode is positioned at the target site 402, the method 400 can initiate delivery of atrial pacing therapy at the target site using the pacing electrode 404. The atrial pacing therapy may be delivered using a plurality of pacing parameters, or paced settings, such as, e.g., pulse width or duration, pulse amplitude (voltage), number of pulses in pulse train, and timing relative to an atrial or ventricular event. In some embodiments, the initial delivery of atrial pacing therapy is delivered at a predetermined or default pulse width or duration, and a predetermined or default pulse amplitude (voltage). The default, or predetermined, pulse amplitude may be about 0.5 volts to about 1.5 volts and the default, or predetermined, pulse width or duration may be about 0.03 ms to about 1.5 ms.

[0040] The method 400 includes monitoring external electrical activity using at least one external electrode 406 at least during the delivery of the atrial pacing therapy 404. The at least one external electrode can be coupled to the skin of the patient. In some embodiments, at least one external electrode included in the at least one external electrode can be coupled to an abdomen of the patient. In some embodiments, the at least one external electrode can be and / or include more than one electrode 164 as shown in FIG. 1 A. For example, the at least one external electrode may include a Lead II electrode and / or a VI electrode of a standard 12-lead electrocardiogram. Although it is noted that the external electrical activity is monitored using at least one external electrode 406 during the delivery of the atrial pacing therapy 404, it is to be understood that the external electrical activity may be monitored continuously (e.g., before, after, and during the atrial pacing therapy), which may include before, during, and after implantation of the pacing electrode. In one embodiment, one or more processes of method 400 are utilized post-operatively (e.g., days, weeks, months after implantation of the pacing electrode) to determine whether the atrial pacing therapy is engaging both atria.

[0041] Monitoring external electrical activity 406 results in electrical signals representative of electrical and mechanical activity of the heart such as the polarization anddepolarization of one or more chambers of the heart and contraction and relaxation of one or more chambers of the heart. In this method 400, the electrical activity representative of electrical and mechanical activity of atria, e.g., P-waves, are utilized to determine whether both atria are engaged by the atrial pacing therapy. In one embodiment, it may be described that P-wave data (e.g., atrial activation data) is generated using the at least one external electrode. In some embodiments, the P-wave data can include multiple complete P-waves. In one embodiment, to capture or monitor electrical activity representative of electrical and mechanical activity of the atria, the external electrical activity is or can be monitored for a selected time period following initiation of delivery of the atrial pacing therapy. The selected time may be predetermined or provided by a user such as the human practitioner. In some embodiments, the selected time period may start a predetermined amount of time before the atrial pacing therapy is delivered. In other words, the selected time period may begin a predetermined amount of time before a pacing pulse is delivered or applied at the target site using the pacing electrode. The selected time period may begin about one to ten milliseconds before the atrial pacing therapy is delivered. In some embodiments, the selected time period may end at the end of the atrial pacing therapy. In some embodiments, the selected time period may end a predetermined amount of time after the atrial pacing therapy is delivered. In other words, the selected time period may end a predetermined amount of time after the current being applied at the target ceases. The selected time period may end about two hundred milliseconds to three seconds after the atrial pacing therapy ceases being delivered. The selected time period may include a time period preceding the delivery of the atrial pacing therapy, a time period during the atrial pacing therapy, and a time period following delivery of the atrial pacing therapy. In some embodiments, the selected time period may end after one heartbeat has occurred following delivery of the atrial pacing therapy (e.g., about two hundred milliseconds after delivery of the atrial pacing therapy). In some embodiments, the selected time period may end after multiple heartbeats have occurred following delivery of the atrial pacing therapy. In some embodiments, the selected time period may end after at least three heartbeats have occurred following delivery of the atrial pacing therapy (e.g., about one second to three seconds after delivery of the atrial pacing therapy depending on the patient). In this way, the process 406 can monitor and / or receive multiple complete P-waves.

[0042] Illustrative external electrical activity 500 monitored from Lead II of a twelve- lead ECG measurement, for example, of the system of FIG. 1 A is depicted in FIG. 5A, and illustrative external electrical activity 514 monitored from Lead II of a twelve-lead ECGmeasurement, for example, of the system of FIG. 1 A is depicted in FIG. 6A. More specifically, a portion of electrical activity 500, 514 immediately preceding and following the delivery of cardiac pacing therapy is depicted. Such illustrative external electrical activity 500, 514 will be processed using the method 400 as will be further described herein.

[0043] The method 400 further includes generating a right atrial component representative of right atrial activation and a left atrial component representative of left atrial activation 408 based on the monitored external electrical activity monitored during the delivery of the atrial pacing therapy. The right and left atrial components are utilized further by method 400 to determine engagement of both atria by the atrial pacing therapy delivered to the target site as will be described further herein.

[0044] Generation of the right and left atrial components may be performed using a variety of different processes and techniques. One illustrative process of generating the right and left atrial components 409 based on the external electrical activity is depicted in FIG. 3. In some embodiments, the process 409 can be implemented (e.g., as instructions) in a memory and executed by a processor such as, e.g., a computing apparatus, and / or a computing apparatus (e.g., the computing apparatus 134 of the system 110 of FIG. 1A). The process 409 first includes curve fitting the external electrical activity 416. The process 409 can fit a curve to the external electrical activity using any fitting technique. In one embodiment, curve fitting the external electrical activity 416 includes a second degree Gaussian function fitting. The Gaussian fitting technique may include one or more constraints that must be met when fitting the curve. The one or more constraints can include a requirement that the curve be positive. In another embodiment, curve fitting the external electrical activity 416 includes fitting the external electrical activity using a MATLAB fit function. In another embodiment, curve fitting the external electrical activity 416 includes rectifying the external electrical activity, generating a half derivative of the rectified external electrical activity, and identifying peaks and / or maximums included in the half derivative of the rectified external electrical activity. In some embodiments, before curve fitting the external electrical activity, the process 409 can include preprocessing the external electrical activity. The preprocessing of the external electrical activity can include filtering and / or smoothing the external electrical activity.

[0045] After curving fitting 416, the process 409 includes generating a first atrial component based on the curve fit to the external electrical activity 418 and generating a second atrial component based on the curve fit to the external electrical activity 420. The firstatrial component corresponds to activity of one of the atria while the second atrial component corresponds to activity of the other atria. In other words, the first atrial component corresponds to activity of one of the left atrium and right atrium, and the second atrial component corresponds to activity of whichever atria that the first atrial component did not correspond to.

[0046] In one embodiment, the first atrial component is generated based on a first peak included in the curve that was fit to the P-wave data. The first atrial component may be described as a curve that approximates the first atrial activation that includes the peak of the first atrial activation. In some embodiments, the first atrial component can include the peak of the first atrial activation. Likewise, in one embodiment, the second atrial component is generated based on a second peak included in the curve that was fit to the P-wave data. The second atrial component may be described as a curve that approximates the second atrial activation that includes the peak of the second atrial activation. In some embodiments, the second atrial component can include the peak of the second atrial activation.

[0047] It is to be understood that the use of the terms first and second in conjunction with the term peak refer to the chronological order of the peaks, and the terms first and second in conjunction with the term component refer to the peaks that they are based thereon. Thus, the terms first and second used with such terms do not connote whether such components or peaks correspond to left or right atrial activation. In other words, the second peak chronologically follows the first peak, and the data derived therefrom will follow the same first and second labeling.

[0048] In some embodiments, the first and second atrial component are generated based on predetermined reference curves. The reference curves may represent the shape of a typical right or left atrial activation. Using such reference curves, the process 409 may generate the right atrial component with a more normalized shape.

[0049] The first atrial component, and in this case, the left atrial component, 504 and the second atrial component, and in this case, the right atrial component, 502 is depicted in FIG. 5B. Likewise, the first atrial component, and in this case, the left atrial component, 518 and the second atrial component, and in this case, the right atrial component, 516 is depicted in FIG. 6B.

[0050] As shown in FIG. 5B, each of the atrial components is determined based on the maximum amplitudes of the external electrical activity 500. More specifically, the right atrial maximum amplitude value 510 and the left atrial maximum amplitude value 512 weredetermined, and then the right atrial component 502 and the left atrial component 504 were determined based therein using the processes described herein (e.g., 2nddegree curve fitting). As shown in FIG. 6B, each of the atrial components is determined based on the maximum amplitudes of the external electrical activity 514. More specifically, the right atrial maximum amplitude value 524 and the left atrial maximum amplitude value 526 were determined, and then the right atrial component 516 and the left atrial component 518 were determined based therein using the processes described herein (e.g., 2nddegree curve fitting).

[0051] Thus, the process 409 results in a first and second atrial components derived, or generated, from the monitored external electrical activity. Such first and second atrial components may be further used to determine engagement of both atria by the atrial pacing therapy as will be further described herein. It is to be understood that the first atrial component may correspond to the left atrium and the second atrial component may correspond to the right atrium, and vice versa, depending on which atrium activates first according to the monitored electrical activity. As such, the process 409 results in a right atrial component representative of right atrial activation and a left atrial component representative of left atrial activation.

[0052] After generation of the right and left atrial components 408, the method 400 generates at least one metric 410 based on the right atrial component and the left atrial component. The at least one metric includes any metric that may be useful to determine engagement of both atria by the atrial pacing therapy. In some embodiments, the at least one metric includes a right atrial maximum amplitude of the right atrial component to left atrial maximum amplitude of the left atrial component ratio value. In other words, the maximum amplitude of the right atrial component is compared (e.g., divided) to the maximum amplitude of the left atrial component resulting in a value, which may be referred to as a right atrial maximum amplitude of the right atrial component to left atrial maximum amplitude of the left atrial component ratio value. Generation of illustrative right atrial maximum amplitude of the right atrial component to left atrial maximum amplitude of the left atrial component ratio values will be described further herein with respect to FIGS. 4-6.

[0053] In some embodiments, the at least one metric includes an atrium-to-atrium activation delay value. The atrium-to-atrium activation delay value represents the delay between activation of a first atrium (either the right or the left atrium) and a second atrium (whichever atrium is not the first atrium). The atrium-to-atrium activation delay value may be generated, or computed, using a variety of processes or techniques. In one embodiment, afiducial point within each of the left and right atrial components is selected, and the time period or duration therebetween is measured resulting in the atrium-to-atrium activation delay value. The fiducial point can be any measurable value with the left and right atrial components that is reliable for determining an activation delay therebetween. In one embodiment, the fiducial point is a peak or maximum amplitude of the atrial component. In one embodiment, the fiducial point is a maximum negative slope of the atrial component. Generation of illustrative atrium-to-atrium activation delay values will be described further herein with respect to FIGS. 4-6.

[0054] In some embodiments, the at least one metric includes a P-wave width value. The P-wave width value is a time period between initialization of the P-wave and a cessation of the P-wave. Generation of illustrative P-wave width values will be described further herein with respect to FIGS. 4-6. In some embodiments, the at least one metric includes a P-R interval value generated based on the external electrical activity. Shorter P-R intervals may be associated with greater biatrial engagement.

[0055] Illustrative processes 411 for generating one or more metrics based on a right atrial component and a left atrial component are shown in FIG. 4. In some embodiments, the processes 411 can be implemented (e.g., as instructions) in a memory and executed by a processor. In some embodiments, the processes 411 can be implemented and executed by a controller, a computing apparatus, and / or a computing apparatus (e.g., the computing apparatus 134 of system 110 of FIG. 1A).

[0056] The processes 411 can include determining a P-wave width value 426 based on the monitored external electrical activity. In one embodiment, the P-wave width value is determined using two time values (i.e., y-axis values) of the monitored external electrical activity where the external electrical activity has approximately equal amplitude values. Then, the approximate length of a P-wave can be determined based on each of those determined time values. In other words, the duration or time period between each of the two time values may be measured or computed resulting in the P-wave width value. In one embodiment, one of the time values can be at a predetermined length of time following delivery of the atrial pacing therapy (e.g., about five milliseconds following delivery of the atrial pacing therapy). In one embodiment, the P-wave width value is determined using two time values (i.e., y-axis values) of the monitored external electrical activity where the external electrical activity crosses a threshold or baseline value, and the duration or time period therebetween may be measured or computed resulting in P-wave width value. In oneembodiment, the P-wave width value is determined based on a start value and an end value generated by a curve fit function (e.g., a MATLAB fit function). In this embodiment, the P- wave width value can be equal to the difference between the start value and the end value. In some embodiments, the processes 411 can include determining a P-R interval value generated based on the external electrical activity.

[0057] The processes 411 include determining a right atrial maximum amplitude value 428 based on the right atrial component and a left atrial maximum amplitude value 430 based on the left atrial component. In one embodiment, the right and left atrial maximum amplitude values are the absolute maximum amplitude values included in the right and left atrial components, respectively.

[0058] The right and left atria maximum amplitudes are compared (e.g., divided) to each other to determine a right atrial maximum amplitude of the right atrial component to left atrial maximum amplitude of the left atrial component ratio value 436. In other words, the process 436 can compute, or set, the right atrial maximum amplitude of the right atrial component to left atrial maximum amplitude of the left atrial component ratio value to be equal to the right atrial maximum amplitude value divided by the left atrial maximum amplitude value.

[0059] The processes 411 further include determining a right atrial maximum amplitude time value based on the right atrial component 432 and determining a left atrial maximum amplitude time value based on the left atrial component 434. The right and left atrial maximum amplitude time values are time points associated with an absolute maximum amplitude value included in the right and left atrial components, respectively. In other words, the right atrial maximum amplitude time value can be equal to the time value (i.e., y-axis value) of when the right atrial component has an absolute maximum amplitude, and the left atrial maximum amplitude time value can be equal to the time value (i.e., y-axis value) of when the left atrial component has an absolute maximum amplitude.

[0060] The processes 411 include determining the atrium -to-atrium activation delay value 438 based on the right atrial maximum amplitude time value and the left atrial maximum amplitude time value. The atrium-to-atrium activation delay value can indicate a delay between the right atrial component and the left atrial component. In one embodiment, determining the atrium-to-atrium activation delay value includes subtracting the left atrial maximum amplitude time value from the right atrial maximum amplitude time value.

[0061] With reference to FIG. 5B, the right atrial maximum amplitude value 510 and the left atrial maximum amplitude value 512 may be used to determine the right atrial maximum time amplitude value 506 and left atrial maximum time amplitude value 508. As a result, an atrium-to-atrium activation delay value and a right atrial maximum amplitude of the right atrial component to left atrial maximum amplitude of the left atrial component ratio value may be generated or determined based on such determinations. Additionally, a P-wave width value 501 may be generated based on the external electrical activity 500. With reference to FIG. 6B, the right atrial maximum amplitude value 524 and the left atrial maximum amplitude value 526 may be used to determine the right atrial maximum time amplitude value 520 and left atrial maximum time amplitude value 522. As a result, an atrium-to-atrium activation delay value and a right atrial maximum amplitude of the right atrial component to left atrial maximum amplitude of the left atrial component ratio value may be generated or determined based on such determinations. Additionally, a P-wave width value 515 may be generated based on the external electrical activity 514. As shown, each of the atrium-to- atrium activation delay value, a right atrial maximum amplitude of the right atrial component to left atrial maximum amplitude of the left atrial component ratio value, and the P-wave width value of FIG. 6B generated from the electrical activity 514 of FIG. 6A is smaller than the each of the atrium-to-atrium activation delay value, a right atrial maximum amplitude of the right atrial component to left atrial maximum amplitude of the left atrial component ratio value, and the P-wave width value of FIG. 5B generated from the electrical activity 500 of FIG. 5 A thereby indicating that the cardiac pacing therapy resulting in the electrical activity 514 of FIG. 6A better engages both of the atria than the cardiac pacing therapy resulting in the electrical activity 500 of FIG. 5 A.

[0062] Referring back to FIG. 2, after the at least one metric is generated 410, the method 400 includes determining engagement of both atria by the atrial pacing therapy 412 based on the at least one metric. For example, generally, each of the at least one metrics may be compared to threshold values, and if the metrics meets such threshold values, then it may be determined that the both atria are engaged by the atrial pacing therapy. Conversely, generally, if each of the at least one metrics if the metrics do not meet such threshold values, then it may be determined that both atria are not engaged by the atrial pacing therapy. If it is determined that the both atria are engaged by the atrial pacing therapy, then the method 400 may proceed to implanting the pacing electrode at the target site 414, e.g., for using in providing atrial pacing therapy. If it is determined that the both atria are not engaged by the atrial pacingtherapy, then the method 400 may return to potentially adjusting the atrial pacing therapy 415, potentially moving the pacing electrode to a new target site 402, and then restarting the evaluation processes.

[0063] In other words, in some embodiments, the method 400 can determine the atrial pacing therapy is engaging both atrium by outputting at least one of the right atrial maximum amplitude of the right atrial component to left atrial maximum amplitude of the left atrial component ratio value, the atrium-to-atrium activation delay value, the P-wave width value, and / or the one or more indicators that the current target site is more suitable for implantation than previous target sites to a display (e.g., the display 136 in FIG. 1A). The method 400 can the receive an indication of acceptability or unacceptability from the user. If the method 400 determines that the target site for the atrial pacing therapy is not acceptable, the method 400 can proceed to potentially adjusting the atrial pacing therapy 415 and potentially moving the pacing electrode another target site 402. If the method 400 determines that the atrial pacing therapy is engaging both atria, the method 400 can proceed to implanting the electrode at the target site 414.

[0064] In one embodiment, determining whether the atrial pacing therapy is engaging both atria includes determining whether the atrial pacing therapy is most effective based on the at least one metric. The determining whether the atrial pacing therapy is engaging both atria may include generating at least one metric at a plurality of target sites. In this way, a physician or other user can pace map multiple target sites in order to determine a suitable implantation location. In some embodiments, the effectiveness of the atrial pacing therapy is generated based on one or more of the right atrial maximum amplitude of the right atrial component to left atrial maximum amplitude of the left atrial component ratio value and the atrium-to-atrium activation delay value. For example, each of the right atrial maximum amplitude of the right atrial component to left atrial maximum amplitude of the left atrial component ratio value, the atrium-to-atrium activation delay value, and P-wave width value may be given a weight, or multiplier, and then summed resulting in an effectiveness score for each target site where the electrode is positioned and for each different combination of paced settings. The target site and combination of paced settings having the highest effectiveness score may be determined.

[0065] In one embodiment, the effectiveness of the atrial pacing therapy is generated based on one or more predetermined threshold values. For example, the right atrial maximum amplitude of the right atrial component to left atrial maximum amplitude of the left atrialcomponent ratio value, the atrium-to-atrium activation delay value, and / or the P-wave width value can be compared to one or more predetermined threshold values. The one or more predetermined threshold values can include a predetermined maximum delay value, a predetermined maximum ratio value, a predetermined minimum ratio value, and / or a maximum P-wave width value. If a particular metric meets the predetermined threshold value, the method can indicate that the predetermined threshold value has been met. For example, the method 400 can compare the atrium-to-atrium activation delay value to the predetermined maximum delay value, and if the atrium-to-atrium activation delay value is below the predetermined maximum delay value, output an indication that the predetermined maximum delay value has been met. The indication can be a visual indicator (e.g., a green checkmark) that indicates the threshold has been met. In one embodiment, the analyzer has preset threshold values so that it returns a "green checkmark" or some other form of validation when the parameters are met along with the measured values.

[0066] In one embodiment, determining whether the atrial pacing therapy is engaging both atria includes determining an acceptability of the atrial pacing therapy based on the at least one metric. In some embodiments, the acceptability of the atrial pacing therapy is based on one or more of the right atrial maximum amplitude of the right atrial component to left atrial maximum amplitude of the left atrial component ratio value, and the atrium-to-atrium activation delay value. In some embodiments, determining the acceptability of the atrial pacing therapy is further based on the P-wave width value. In some embodiments, determining the acceptability of the atrial pacing therapy is further based on the P-R interval value.

[0067] In some embodiments, the method 400 includes displaying or showing at least one of the right atrial maximum amplitude of the right atrial component to left atrial maximum amplitude of the left atrial component ratio value, the atrium-to-atrium activation delay value, and the P-wave width value to a user such as the human practitioner using a display. In some embodiments, the method 400 includes displaying or showing at least one of biatrial effectiveness score, e.g., for each target site and paced setting combination, to a user such as the human practitioner using a display. In some embodiments, the method 400 can display historical values of one or more of the right atrial maximum amplitude of the right atrial component to left atrial maximum amplitude of the left atrial component ratio value, the atrium-to-atrium activation delay value, the P-wave width value, and the P-R interval value to the user. In other words, the method 400 may determine if the right atrial maximumamplitude of the right atrial component to left atrial maximum amplitude of the left atrial component ratio value, the atrium-to-atrium activation delay value, the P-wave width value, and / or the P-R interval value are acceptable. In some embodiments, the method 400 may attempt to minimize at least one of the right atrial maximum amplitude of the right atrial component to left atrial maximum amplitude of the left atrial component ratio value, the atrium-to-atrium activation delay value, the P-wave width value, and / or the P-R interval value. Lower values of one or more of the right atrial maximum amplitude of the right atrial component to left atrial maximum amplitude of the left atrial component ratio value, the atrium-to-atrium activation delay value, the P-wave width value, and the P-R interval value may indicate that the electrode is at or near the Bachmann’s bundle. For example, the method 400 and the user may attempt to minimize the right atrial maximum amplitude of the right atrial component to left atrial maximum amplitude in order to target the Bachmann’s bundle. As another example, the method 400 and / or the user may attempt to minimize the atrium-to- atrium activation delay value in order to target the Bachmann’s bundle. In a further example, the method 400 and / or the user may attempt to minimize the P-wave width value in order to target the Bachmann’s bundle. In a still further example, the method 400 and / or the user may attempt to minimize the P-R interval value in order to target the Bachmann’s bundle. In some embodiments, the method 400 and / or the user may attempt to minimize at least two of the right atrial maximum amplitude of the right atrial component to left atrial maximum amplitude of the left atrial component ratio value, the atrium-to-atrium activation delay value, and / or the P-wave width value, but with certain values having greater priority. As one example, the method 400 and / or the user may wish to minimize both the right atrial maximum amplitude of the right atrial component to left atrial maximum amplitude of the left atrial component ratio value and the atrium-to-atrium activation delay value, with greater emphasis on minimizing the right atrial component to left atrial maximum amplitude of the left atrial component ratio value. As another example, the method 400 and / or the user may wish to minimize both the right atrial maximum amplitude of the right atrial component to left atrial maximum amplitude of the left atrial component ratio value and the atrium-to- atrium activation delay value, with greater emphasis on minimizing the atrium-to-atrium activation delay value. In a further example, the method 400 and / or the user may wish to minimize the right atrial maximum amplitude of the right atrial component to left atrial maximum amplitude of the left atrial component ratio value, the atrium-to-atrium activation delay value, and the P-wave width value, with the most emphasis on minimizing the rightatrial component to left atrial maximum amplitude of the left atrial component ratio value, the second most emphasis on the atrium-to-atrium activation delay value, and the least emphasis on the atrium-to-atrium activation delay value. In some embodiments, the method 400 can output one or more indicators that indicate if the electrode at the target site has improved the right atrial maximum amplitude of the right atrial component to left atrial maximum amplitude of the left atrial component ratio value, the atrium-to-atrium activation delay value, and / or the P-wave width value as compared to previous values. For example, the method 400 may determine that current values of the right atrial maximum amplitude of the right atrial component to left atrial maximum amplitude of the left atrial component ratio value, the atrium-to-atrium activation delay value, and / or the P-wave width value have improved over previous values at different target sites, and output one or more indicators that the current target site is more suitable for implantation than previous target sites.

[0068] Another illustrative method for determining one or more metrics for use in determining engagement of both atria by atrial pacing therapy is depicted in FIG. 7. In particular, the method 600 may include determining a right atrial maximum amplitude of a right atrial component to left atrial maximum amplitude of a left atrial component ratio value 636, an atrium-to-atrium activation delay value 638, and a P-wave width value 622. The method 600 can receive P-wave data 602, e.g., generated using a Lead II electrode and / or a VI electrode of a standard 12-lead electrocardiogram. The method 600 includes curve fitting 604 the P-wave data to generate a right atrial activation function 610 and a left atrial activation function 612. The method 600 further includes determining 608 two time points xi and xrwhere a P-wave 606 included in the P-wave data is approximately equal. The method 600 includes determining the P-wave width value 620 by determining a difference between the two time points. The method 600 includes identifying 614 a right atrial peak amplitude value 624 and a right atrial peak location value 628 based on the right atrial activation function 610. The method 600 includes determining 616 a left atrial peak amplitude value 626 and a left atrial peak location value 630 based on the left atrial activation function 612. The method 600 further includes determining 632 the right atrial component to left atrial maximum amplitude of the left atrial component ratio value 636 based on the right atrial peak amplitude value 624 and the left atrial peak amplitude value 626 and determining 634 the atrium-to-atrium activation delay value 638 based on the right atrial peak location value 628 and the left atrial peak location value 630.

[0069] Illustrative cardiac therapy systems and devices may be further described herein with reference to FIGS. 8-10 that may be the illustrative systems, methods, and processes described herein with respect to FIGS. 1-7. The illustrative cardiac therapy systems and devices described herein may be configured to deliver atrial septal pacing, Bachmann's bundle pacing (i.e., cardiac conduction system pacing therapy directed to the Bachmann’s bundle), left atrial pacing, or biatrial pacing. For example, the Bachmann's bundle may be described as a path for electrical activation of the left atrium during normal sinus rhythm and is therefore considered to be part of the “conduction system” of the heart. Therefore, atrial pacing using a single lead in the atrium that targets the Bachmann's bundle for synchronized atrial activation may be used to treat atrial dyssynchrony. Another possible pacing therapy for treating atrial dyssynchrony may include multi-site atrial stimulation using two leads, one positioned in the right atrium and the other being positioned within the left atrium.

[0070] FIG. 8 is a conceptual diagram illustrating an illustrative therapy system 10 that may be used to deliver pacing therapy to a patient 14. Patient 14 may, but not necessarily, be a human. The therapy system 10 may include an implantable medical device 16 (IMD), which may be coupled to leads 18, 20, 22. The IMD 16 may be, e.g., an implantable pacemaker, cardioverter, and / or defibrillator, that delivers, or provides, electrical signals (e.g., paces, etc.) to and / or senses electrical signals from the heart 12 of the patient 14 via electrodes coupled to one or more of the leads 18, 20, 22.

[0071] The leads 18, 20, 22 extend into the heart 12 of the patient 14 to sense electrical activity of the heart 12 and / or to deliver electrical stimulation to the heart 12. In the example shown in FIG. 8, the right ventricular (RV) lead 18 extends through one or more veins (not shown), the superior vena cava (not shown), and the right atrium 26, and into the right ventricle 28. The left ventricular (LV) coronary sinus lead 20 extends through one or more veins, the vena cava, the right atrium 26, and into the coronary sinus 30 to a region adjacent to the free wall of the left ventricle 32 of the heart 12. The right atrial (RA) lead 22 extends through one or more veins and the vena cava, and into the right atrium 26 of the heart 12.

[0072] The RA lead 22 is positioned such that its distal end is in the vicinity of the atrial septal wall to deliver biatrial cardiac therapy (e.g., pacing to both of the atria). Specifically, in at least one embodiment, the RA lead 22 is positioned such that its distal end is in the vicinity of the Bachmann’s Bundle between the superior vena cava and the ascending aorta so as to deliver cardiac conduction system pacing therapy to the Bachmann’s Bundle. The RA lead 22may be referred to as a Bachmann’s Bundle lead. Positioning the RA lead 22 at the Bachmann’s bundle rather than the other locations in or around the right atrium may improve pacing efficacy in certain applications. In other words, if placed at the Bachmann’s Bundle, the RA lead 22 may function in place of a traditional right atrial lead and provide the benefits of positioning the lead at the Bachmann’s Bundle (e.g., increased pacing efficacy). The RA lead 22 is equipped with one or more of a ring electrode 48, a tip electrode 50, and helix electrode 54. In at least one embodiment, instead of a helix electrode 54, the RA lead 22 may include a needle electrode. The helix electrode 54 may extend from the distal end (in conjunction with or in replace of the tip electrode 50) for sensing and pacing in the Bachmann’s Bundle. Additionally, in one embodiment, the helix electrode 54 may be mounted retractably within the electrode head 56 of the RA lead 22. The ring electrode 48, the tip electrode 50, and the helix electrode 54 are each connected to an insulated conductor with the body of the RA lead 22.

[0073] The IMD 16 may sense, among other things, electrical signals attendant to the depolarization and repolarization of the heart 12 via electrodes coupled to at least one of the leads 18, 20, 22. In some examples, the IMD 16 provides pacing therapy (e.g., pacing pulses) to the heart 12 based on the electrical signals sensed within the heart 12. The IMD 16 may be operable to adjust one or more parameters associated with the pacing therapy such as, e.g., A- V delay and other various timings, pulse width, amplitude, voltage, burst length, etc. Further, the IMD 16 may be operable to use various electrode configurations to deliver pacing therapy, which may be unipolar, bipolar, quadripoloar, or further multipolar. For example, as described herein, the one or more parameters may be adjusted to in an attempt to engage or capture the Bachmann’s Bundle. Additionally, a multipolar lead may include several electrodes that can be used for delivering pacing therapy. Hence, a multipolar lead system may provide, or offer, multiple electrical vectors to pace from. A pacing vector may include at least one cathode, which may be at least one electrode located on at least one lead, and at least one anode, which may be at least one electrode located on at least one lead (e.g., the same lead, or a different lead) and / or on the casing, or can, of the IMD. While improvement in cardiac function as a result of the pacing therapy may primarily depend on the cathode, the electrical parameters like impedance, pacing threshold voltage, current drain, longevity, etc. may be more dependent on the pacing vector, which includes both the cathode and the anode. The IMD 16 may also provide defibrillation therapy and / or cardioversion therapy via electrodes located on at least one of the leads 18, 20, 22. Further, the IMD 16 may detectarrhythmia of the heart 12, such as fibrillation of the ventricles 28, 32, and deliver defibrillation therapy to the heart 12 in the form of electrical pulses. In some examples, IMD 16 may be programmed to deliver a progression of therapies, e.g., pulses with increasing energy levels, until a fibrillation of heart 12 is stopped.

[0074] FIG. 9 are conceptual diagrams illustrating the IMD 16 and the leads 18, 20, 22 of therapy system 10 of FIG. 8 in more detail. The leads 18, 20, 22 may be electrically coupled to a therapy delivery module (e.g., for delivery of pacing therapy), a sensing module (e.g., for sensing one or more signals from one or more electrodes), and / or any other modules of the IMD 16 via a connector block 34. In some examples, the proximal ends of the leads 18, 20, 22 may include electrical contacts that electrically couple to respective electrical contacts within the connector block 34 of the IMD 16. In addition, in some examples, the leads 18, 20, 22 may be mechanically coupled to the connector block 34 with the aid of set screws, connection pins, or another suitable mechanical coupling mechanism.

[0075] Each of the leads 18, 20, 22 includes an elongated insulative lead body, which may carry a number of conductors (e.g., concentric coiled conductors, straight conductors, etc.) separated from one another by insulation (e.g., tubular insulative sheaths). In the illustrated example, bipolar electrodes 40, 42 are located proximate to a distal end of the lead 18. In addition, bipolar electrodes 44, 45, 46, 47 are located proximate to a distal end of the lead 20 and bipolar electrodes 48, 50, 54 are located proximate to a distal end of the lead 22.

[0076] The electrodes 40, 44, 45, 46, 47, 48 may take the form of ring electrodes, and the electrode 42 may take the form of extendable helix tip electrode mounted retractably within the insulative electrode heads 52. Each of the electrodes 40, 42, 44, 45, 46, 47, 48, 50, 54 may be electrically coupled to a respective one of the conductors (e.g., coiled and / or straight) within the lead body of its associated lead 18, 20, 22, and thereby coupled to a respective one of the electrical contacts on the proximal end of the leads 18, 20, 22.

[0077] Additionally, electrodes 44, 45, 46 and 47 may have an electrode surface area of about 5.3 mm2to about 5.8 mm2. Electrodes 44, 45, 46, and 47 may also be referred to as LV1, LV2, LV3, and LV4, respectively. The LV electrodes (i.e., left ventricle electrode 1 (LV1) 44, left ventricle electrode 2 (LV2) 45, left ventricle electrode 3 (LV3) 46, and left ventricle 4 (LV4) 47 etc.) on the lead 20 can be spaced apart at variable distances. For example, electrode 44 may be a distance of, e.g., about 21 millimeters (mm), away fromelectrode 45, electrodes 45 and 46 may be spaced a distance of, e.g., about 1.3 mm to about 1.5 mm, away from each other, and electrodes 46 and 47 may be spaced a distance of, e.g., 20 mm to about 21 mm, away from each other.

[0078] The electrodes 40, 42, 44, 45, 46, 47, 48, 50, 54 may further be used to sense electrical signals (e.g., morphological waveforms within electrograms (EGM)) attendant to the depolarization and repolarization of the heart 12. The electrical signals are conducted to the IMD 16 via the respective leads 18, 20, 22. In some examples, the IMD 16 may also deliver pacing pulses via the electrodes 40, 42, 44, 45, 46, 47, 48, 50, 54 to cause depolarization of cardiac tissue of the patient's heart 12. In some examples, as illustrated in FIG. 9, the IMD 16 includes one or more housing electrodes, such as housing electrode 58, which may be formed integrally with an outer surface of a housing 60 (e.g., hermetically sealed housing) of the IMD 16 or otherwise coupled to the housing 60. Any of the electrodes 40, 42, 44, 45, 46, 47, 48, 50, 54 may be used for unipolar sensing or pacing in combination with the housing electrode 58. It is generally understood by those skilled in the art that other electrodes can also be selected to define, or be used for, pacing and sensing vectors. Further, any of electrodes 40, 42, 44, 45, 46, 47, 48, 50, 54, 58, when not being used to deliver pacing therapy, may be used to sense electrical activity during pacing therapy.

[0079] As described in further detail with reference to FIG. 9, the housing 60 may enclose a therapy delivery module that may include a stimulation generator for generating cardiac pacing pulses and defibrillation or cardioversion shocks, as well as a sensing module for monitoring the electrical signals of the patient’s heart (e.g., the patient's heart rhythm). The leads 18, 20, 22 may also include elongated electrodes 62, 64, 66, respectively, which may take the form of a coil. The IMD 16 may deliver defibrillation shocks to the heart 12 via any combination of the elongated electrodes 62, 64, 66 and the housing electrode 58. The electrodes 58, 62, 64, 66 may also be used to deliver cardioversion pulses to the heart 12. Further, the electrodes 62, 64, 66 may be fabricated from any suitable electrically conductive material, such as, but not limited to, platinum, platinum alloy, and / or other materials known to be usable in implantable defibrillation electrodes. Since electrodes 62, 64, 66 are not generally configured to deliver pacing therapy, any of electrodes 62, 64, 66 may be used to sense electrical activity and may be used in combination with any of electrodes 40, 42, 44, 45, 46, 47, 48, 50, 54, 58. In at least one embodiment, the RV elongated electrode 62 may be used to sense electrical activity of a patient's heart during the delivery of pacing therapy (e.g.,in combination with the housing electrode 58, or defibrillation electrode-to-housing electrode vector).

[0080] The configuration of the illustrative therapy system 10 illustrated in FIGS. 8-10 is merely one example. In other examples, the therapy system may include epicardial leads and / or patch electrodes instead of or in addition to the transvenous leads 18, 20, 22 illustrated in FIG. 8. Additionally, in other examples, the therapy system 10 may be implanted in / around the cardiac space without transvenous leads (e.g., leadless / wireless pacing systems) or with leads implanted (e.g., implanted transvenously or using approaches) into the left chambers of the heart (in addition to or replacing the transvenous leads placed into the right chambers of the heart as illustrated in FIG. 8). For example, a leadless IMD may be implanted in the right atrium at the atrial septum to implant a helix or needle electrode into the atrial septal wall to engage the Bachmann’s Bundle (e.g., to deliver cardiac conduction system pacing therapy thereto). Further, in one or more embodiments, the IMD 16 need not be implanted within the patient 14. For example, the IMD 16 may deliver various cardiac therapies to the heart 12 via percutaneous leads that extend through the skin of the patient 14 to a variety of positions within or outside of the heart 12. In one or more embodiments, the system 10 may utilize wireless pacing (e.g., using energy transmission to the intracardiac pacing component(s) via ultrasound, inductive coupling, RF, etc.) and sensing cardiac activation using electrodes on the can / housing and / or on subcutaneous leads.

[0081] In other examples of therapy systems that provide electrical stimulation therapy to the heart 12, such therapy systems may include any suitable number of leads coupled to the IMD 16, and each of the leads may extend to any location within or proximate to the heart 12. For example, other examples of therapy systems may include three transvenous leads located as illustrated in FIGS. 8-10. Still further, other therapy systems may include a single lead that extends from the IMD 16 into the right atrium 26 or the right ventricle 28, or two leads that extend into a respective one of the right atrium 26 and the right ventricle 28.

[0082] FIG. 10 is a functional block diagram of one illustrative configuration of the IMD 16. As shown, the IMD 16 may include a control module 81, a therapy delivery module 84 (e.g., which may include a stimulation generator), a sensing module 86, and a power source 90.

[0083] The control module, or apparatus, 81 may include a processor 80, memory 82, and a telemetry module, or apparatus, 88. The memory 82 may include computer-readableinstructions that, when executed, e.g., by the processor 80, cause the IMD 16 and / or the control module 81 to perform various functions attributed to the IMD 16 and / or the control module 81 described herein. Further, the memory 82 may include any volatile, non-volatile, magnetic, optical, and / or electrical media, such as a random-access memory (RAM), readonly memory (ROM), non-volatile RAM (NVRAM), electrically erasable programmable ROM (EEPROM), flash memory, and / or any other digital media. An illustrative capture management module may be the left ventricular capture management (LVCM) module described in U.S. Pat. No. 7,684,863 entitled "LV THRESHOLD MEASUREMENT AND CAPTURE MANAGEMENT" and issued March 23, 2010, which is incorporated herein by reference in its entirety.

[0084] The processor 80 of the control module 81 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), and / or equivalent discrete or integrated logic circuitry. In some examples, the processor 80 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, and / or one or more FPGAs, as well as other discrete or integrated logic circuitry. The functions attributed to the processor 80 herein may be embodied as software, firmware, hardware, or any combination thereof.

[0085] The control module 81 may control the therapy delivery module 84 to deliver therapy (e.g., electrical stimulation therapy such as pacing) to the heart 12 according to a selected one or more therapy programs, which may be stored in the memory 82. More, specifically, the control module 81 (e.g., the processor 80) may control various parameters of the electrical stimulus delivered by the therapy delivery module 84 such as, e.g., A-V delays, V-V delays, pacing pulses with the amplitudes, pulse widths, frequency, or electrode polarities, etc., which may be specified by one or more selected therapy programs (e.g., A-V and / or V-V delay adjustment programs, pacing therapy programs, pacing recovery programs, capture management programs, etc.). As shown, the therapy delivery module 84 is electrically coupled to electrodes 40, 42, 44, 45, 46, 47, 48, 50, 54, 58, 62, 64, 66, e.g., via conductors of the respective lead 18, 20, 22, or, in the case of housing electrode 58, via an electrical conductor disposed within housing 60 of IMD 16. Therapy delivery module 84 may be configured to generate and deliver electrical stimulation therapy such as pacing therapy to the heart 12 using one or more of the electrodes 40, 42, 44, 45, 46, 47, 48, 50, 54, 58, 62, 64, 66.

[0086] For example, therapy delivery module 84 may deliver pacing stimulus (e.g., pacing pulses) via ring electrodes 40, 44, 45, 46, 47, 48 coupled to leads 18, 20, 22 and / or helical or tip electrodes 42, 50, 54 of leads 18, 22. Further, for example, therapy delivery module 84 may deliver defibrillation shocks to heart 12 via at least two of electrodes 58, 62, 64, 66. In some examples, therapy delivery module 84 may be configured to deliver pacing, cardioversion, or defibrillation stimulation in the form of electrical pulses. In other examples, therapy delivery module 84 may be configured to deliver one or more of these types of stimulation in the form of other signals, such as sine waves, square waves, and / or other substantially continuous time signals.

[0087] The IMD 16 may further include a switch module 85 and the control module 81 (e.g., the processor 80) may use the switch module 85 to select, e.g., via a data / address bus, which of the available electrodes are used to deliver therapy such as pacing pulses for pacing therapy, or which of the available electrodes are used for sensing. The switch module 85 may include a switch array, switch matrix, multiplexer, or any other type of switching device suitable to selectively couple the sensing module 86 and / or the therapy delivery module 84 to one or more selected electrodes. More specifically, the therapy delivery module 84 may include a plurality of pacing output circuits. Each pacing output circuit of the plurality of pacing output circuits may be selectively coupled, e.g., using the switch module 85, to one or more of the electrodes 40, 42, 44, 45, 46, 47, 48, 50, 54, 58, 62, 64, 66 (e.g., a pair of electrodes for delivery of therapy to a bipolar or multipolar pacing vector). In other words, each electrode can be selectively coupled to one of the pacing output circuits of the therapy delivery module using the switch module 85.

[0088] The sensing module 86 is coupled (e.g., electrically coupled) to sensing apparatus, which may include, among additional sensing apparatus, the electrodes 40, 42, 44, 45, 46, 47, 48, 50, 54, 58, 62, 64, 66 to monitor electrical activity of the heart 12, e.g., electrocardiogram (ECG) / electrogram (EGM) signals, etc. The ECGZEGM signals may be used to measure or monitor activation times (e.g., ventricular activations times, etc.), heart rate (HR), heart rate variability (HRV), heart rate turbulence (HRT), deceleration / acceleration capacity, deceleration sequence incidence, T-wave alternans (TWA), P-wave to P-wave intervals (also referred to as the P-P intervals or A- A intervals), R-wave to R-wave intervals (also referred to as the R-R intervals or V-V intervals), P-wave to QRS complex intervals (also referred to as the P-R intervals, A-V intervals, or P-Q intervals), QRS-complex morphology, ST segment(i.e., the segment that connects the QRS complex and the T-wave), T-wave changes, QT intervals, electrical vectors, etc.

[0089] The switch module 85 may also be used with the sensing module 86 to select which of the available electrodes are used, or enabled, to, e.g., sense electrical activity of the patient's heart (e.g., one or more electrical vectors of the patient's heart using any combination of the electrodes 40, 42, 44, 45, 46, 47, 48, 50, 54, 58, 62, 64, 66). Likewise, the switch module 85 may also be used with the sensing module 86 to select which of the available electrodes are not to be used (e.g., disabled) to, e.g., sense electrical activity of the patient's heart (e.g., one or more electrical vectors of the patient's heart using any combination of the electrodes 40, 42, 44, 45, 46, 47, 48, 50, 54, 58, 62, 64, 66), etc. In some examples, the control module 81 may select the electrodes that function as sensing electrodes via the switch module within the sensing module 86, e.g., by providing signals via a data / address bus.

[0090] In some examples, sensing module 86 includes a channel that includes an amplifier with a relatively wider pass band than the R-wave or P-wave amplifiers. Signals from the selected sensing electrodes may be provided to a multiplexer, and thereafter converted to multi-bit digital signals by an analog-to-digital converter for storage in memory 82, e.g., as an electrogram (EGM). In some examples, the storage of such EGMs in memory 82 may be under the control of a direct memory access circuit.

[0091] In some examples, the control module 81 may operate as an interrupt-driven device and may be 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 may be performed by the processor 80 and any updating of the values or intervals controlled by the pacer timing and control module may take place following such interrupts. A portion of memory 82 may be configured as a plurality of recirculating buffers, capable of holding one or more series of measured intervals, which may be analyzed by, e.g., the processor 80 in response to the occurrence of a pace or sense interrupt to determine whether the patient's heart 12 is presently exhibiting atrial or ventricular tachyarrhythmia.

[0092] The telemetry module 88 of the control module 81 may include any suitable hardware, firmware, software, or any combination thereof for communicating with another device, such as a programmer. For example, under the control of the processor 80, thetelemetry module 88 may receive downlink telemetry from and send uplink telemetry to a programmer with the aid of an antenna, which may be internal and / or external. The processor 80 may provide the data to be uplinked to a programmer and the control signals for the telemetry circuit within the telemetry module 88, e.g., via an address / data bus. In some examples, the telemetry module 88 may provide received data to the processor 80 via a multiplexer.

[0093] The various components of the IMD 16 are further coupled to a power source 90, 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.

[0094] The techniques described in this disclosure, including those attributed to the IMD 16, the local computing apparatus 134, and / or various constituent components, 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 processors, including one or more microprocessors, DSPs, ASICs, FPGAs, or any other equivalent integrated or discrete logic circuitry, as well as any combinations of such components, embodied in programmers, such as physician or patient programmers, stimulators, image processing devices, or other devices. The term "module," "processor," or "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.

[0095] Such hardware, software, and / or firmware may be implemented within the same device or within separate devices to support the various operations and functions described in this disclosure. In addition, any of the described units, modules, or components may be implemented together or separately as discrete but interoperable logic devices. Depiction of different features as modules or units is intended to highlight different functional aspects and does not necessarily imply that such modules or units must be realized by separate hardware or software components. Rather, functionality associated with one or more modules or units may be performed by separate hardware or software components or integrated within common or separate hardware or software components.

[0096] When implemented in software, the functionality ascribed to the systems, devices and techniques described in this disclosure may be embodied as instructions on a computer-readable medium such as RAM, ROM, NVRAM, EEPROM, FLASH memory, magnetic data storage media, optical data storage media, or the like. The instructions may be executed by processing circuitry and / or one or more processors to support one or more aspects of the functionality described in this disclosure.ILLUSTRATIVE EXAMPLES

[0097] Example Exl : A system for implanting an atrial pacing lead for delivery of a cardiac pacing therapy to both atria includes at least one external electrode configured to be positioned proximate a patient’s skin to sense external electrical activity, and a computing apparatus including processing circuitry and coupled to the at least one external electrode, the computing apparatus configured to initiate delivery of atrial pacing therapy at a target site to deliver cardiac pacing therapy to both atria, monitor external electrical activity using the at least one external electrode during the delivery of the atrial pacing therapy, generate a right atrial component representative of right atrial activation and a left atrial component representative of left atrial activation based on the external electrical activity monitored during the delivery of the atrial pacing therapy, generate at least one metric based on the right atrial component and the left atrial component, and determine engagement of both atria by the atrial pacing therapy delivered to the target site based on the at least one metric.

[0098] Example Ex2: A method of implanting an atrial pacing lead for delivery of a cardiac pacing therapy to both atria includes initiating delivery of atrial pacing therapy at a target site to deliver cardiac pacing therapy to both atria, monitoring external electrical activity using at least one external electrode during the delivery of the atrial pacing therapy, generating a right atrial component representative of right atrial activation and a left atrial component representative of left atrial activation based on the external electrical activity monitored during the delivery of the atrial pacing therapy, generating at least one metric based on the right atrial component and the left atrial component, and determining engagement of both atria by the atrial pacing therapy delivered to the target site based on the at least one metric.

[0099] Example Ex3: The system as in Example Exl or the method as in Example Ex2, wherein the at least one external electrode includes one or more of a Lead II electrode and a VI electrode of a standard 12-lead electrocardiogram.

[0100] Example Ex4: The system or method as in any one of Examples Exl-3, wherein the at least one metric includes a right atrial maximum amplitude of the right atrial component to left atrial maximum amplitude of the left atrial component ratio value.

[0101] Example Ex5: The system or method as in any one of Examples Exl-4, wherein the at least one metric includes an atrium-to-atrium activation delay value.

[0102] Example Ex6: The system or method as in Example Ex5, wherein the atrium-to- atrium activation delay value is a time period between a right atrial maximum amplitude of the right atrial component and a left atrial maximum amplitude of the left atrial component.

[0103] Example Ex7: The system or method as in any one of Examples Exl-6, wherein the computing apparatus is further configured to execute or the method further includes determining a P-wave width value based on the external electrical activity monitoring delivery of the atrial pacing therapy, and wherein the determining engagement of both atria by the atrial pacing therapy delivered to the target site is further based on the P-wave width value.

[0104] Example Ex8: The system or method as in any one of Examples Exl-7, wherein the generating the right atrial component representative of right atrial activation and the left atrial component representative of left atrial activation includes curve fitting the external electrical activity to generate the right atrial component representative of right atrial activation and the left atrial component representative of left atrial activation.

[0105] Example Ex9: The system or method as in Example Ex8, wherein the curve fitting includes a second degree Gaussian function fitting.

[0106] Example ExlO: The system or method as in any one of Examples Exl-9, wherein the external electrical activity monitored during the delivery of the atrial pacing therapy includes the external electrical activity monitored for a selected time period following initiation of delivery of the atrial pacing therapy.

[0107] Example Exl 1 : The system or method as in Example ExlO, wherein the selected time period is less than or equal to about two hundred milliseconds.

[0108] Example Exl2: The system or method as in any one of Examples Exl-11, wherein the computing apparatus is further configured to execute or the method further includes displaying the at least one metric on a user interface.

[0109] Example Exl3: The system or method as in any one of Examples Exl-12, wherein the computing apparatus is further configured to execute or the method further includes moving the delivery of atrial pacing therapy to a different a target site in response to determination that both atria are not engaged by the atrial pacing therapy delivered to the target site based on the at least one metric.

[0110] Example Exl4: The system or method as in any one of Examples Exl-13, wherein the computing apparatus is further configured to execute or the method further includes changing at least one paced setting of the atrial pacing therapy in response to determination that both atria are not engaged by the atrial pacing therapy delivered to the target site based on the at least one metric.

[0111] Example Exl5: The system or method as in any one of Examples Exl-14, wherein the determining engagement of both atria by the atrial pacing therapy delivered to the target site based on the at least one metric includes determining engagement of the Bachmann’s Bundle by the atrial pacing therapy delivered to the target site based on the at least one metric.

[0112] Example Exl6: The system or method as in any one of Examples Exl-15, wherein the computing apparatus is further configured to execute or the method further includes determining a P-R interval value based on the external electrical activity monitoring delivery of the atrial pacing therapy, and wherein the determining engagement of both atria by the atrial pacing therapy delivered to the target site is further based on the P-R interval value.

[0113] This disclosure has been provided with reference to illustrative embodiments 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 apparatus and methods described herein. Various modifications of the illustrative embodiments, as well as additional embodiments of the disclosure, will be apparent upon reference to this description.

Claims

CLAIMSWhat is claimed is:

1. A system for determination engagement of both atria by atrial pacing therapy at a target site, the system comprising: at least one external electrode configured to be positioned proximate a patient’s skin to sense external electrical activity; and a computing apparatus comprising processing circuitry and coupled to the at least one external electrode, the computing apparatus configured to: initiate delivery of atrial pacing therapy at a target site to deliver cardiac pacing therapy to both atria; monitor external electrical activity using the at least one external electrode during the delivery of the atrial pacing therapy; generate a right atrial component representative of right atrial activation and a left atrial component representative of left atrial activation based on the external electrical activity monitored during the delivery of the atrial pacing therapy; generate at least one metric based on the right atrial component and the left atrial component; and determine engagement of both atria by the atrial pacing therapy delivered to the target site based on the at least one metric.

2. A method for determination engagement of both atria by atrial pacing therapy at a target site, the method comprising: monitoring external electrical activity using at least one external electrode during delivery of the atrial pacing therapy; generating a right atrial component representative of right atrial activation and a left atrial component representative of left atrial activation based on the external electrical activity monitored during the delivery of the atrial pacing therapy; generating at least one metric based on the right atrial component and the left atrial component; and determining engagement of both atria by the atrial pacing therapy delivered to the target site based on the at least one metric.

3. The system as in claim 1 or the method as in claim 2, wherein the at least one external electrode comprises one or more of a Lead II electrode and a VI electrode of a standard 12- lead electrocardiogram.

4. The system or method as in any one of claims 1-3, wherein the at least one metric comprises a right atrial maximum amplitude of the right atrial component to left atrial maximum amplitude of the left atrial component ratio value.

5. The system or method as in any one of claims 1-4, wherein the at least one metric comprises an atrium-to-atrium activation delay value.

6. The system or method as in claim 5, wherein the atrium-to-atrium activation delay value is a time period between a right atrial maximum amplitude of the right atrial component and a left atrial maximum amplitude of the left atrial component.

7. The system or method as in any one of claims 1-6, wherein the computing apparatus is further configured to execute or the method further comprises determining a P-wave width value based on the external electrical activity monitoring delivery of the atrial pacing therapy, and wherein the determining engagement of both atria by the atrial pacing therapy delivered to the target site is further based on the P-wave width value.

8. The system or method as in any one of claims 1-7, wherein the generating the right atrial component representative of right atrial activation and the left atrial component representative of left atrial activation comprises: curve fitting the external electrical activity to generate the right atrial component representative of right atrial activation and the left atrial component representative of left atrial activation.

9. The system or method as in any one of claims 1-8, wherein the external electrical activity monitored during the delivery of the atrial pacing therapy comprises the externalelectrical activity monitored for a selected time period following initiation of delivery of the atrial pacing therapy.

10. The system or method as in claim 9, wherein the selected time period is less than or equal to about two hundred milliseconds.

11. The system or method as in any one of claims 1-10, wherein the computing apparatus is further configured to execute or the method further comprises displaying the at least one metric on a user interface.

12. The system or method as in any one of claims 1-11, wherein the computing apparatus is further configured to execute or the method further comprises moving the delivery of atrial pacing therapy to a different a target site in response to determination that both atria are not engaged by the atrial pacing therapy delivered to the target site based on the at least one metric.

13. The system or method as in any one of claims 1-12, wherein the computing apparatus is further configured to execute or the method further comprises changing at least one paced setting of the atrial pacing therapy in response to determination that both atria are not engaged by the atrial pacing therapy delivered to the target site based on the at least one metric.

14. The system or method as in any one of claims 1-13, wherein the determining engagement of both atria by the atrial pacing therapy delivered to the target site based on the at least one metric comprises determining engagement of the Bachmann’s Bundle by the atrial pacing therapy delivered to the target site based on the at least one metric.

15. The system or method as in any one of claims 1-14, wherein the computing apparatus is further configured to execute or the method further comprises determining a P-R interval value based on the external electrical activity monitoring delivery of the atrial pacing therapy, and wherein the determining engagement of both atria by the atrial pacing therapy delivered to the target site is further based on the P-R interval value.

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