Supraventricular tachycardia management and antitachycardia pacing adjustment in atrially implanted leadless pacemakers

Abstract

The present disclosure relates to a leadless device (100) for implantation in an atrium (A) of a heart comprising a connector (110) for connecting the device to the interior wall of the atrium (A) and a sensor (120) for directly sensing atrial activity of the heart. Further aspects relate to systems (S) comprising such devices and methods performed by such devices.

Description

[Technical Field]

[0001] The present invention relates generally to leadless devices that can be implanted in the atria of the heart, e.g., leadless cardiac implants, and methods and computer programs for operating such devices, particularly for directly sensing activity in the atria of the heart. [Background technology]

[0002] Devices that can be implanted in a patient to sense the patient's cardiac activity and / or to pace or defibrillate the heart have long been known. Such devices have recently been provided as leadless devices. Leadless implants may be implanted directly into the heart in a self-contained manner, with no external leads, e.g., transvenous leads, to interface with the heart. Historically, leadless implants have been used for implantation in the right ventricle. Thus, leadless devices often facilitate cardiac therapy through direct contact with the ventricle as a self-contained system. This distinguishes them from lead-based cardiac devices, which may have a main unit outside the heart (e.g., in the pectoral region), where the interior wall of the ventricle may be in contact with the ends of a transvenous lead system extending from the main unit.

[0003] Known leadless devices may include a stimulator and a sensor in direct contact with the inner wall of the right ventricle. This enables direct electrical stimulation (e.g., pacing) of the right ventricle and direct sensing of electrical signals corresponding to ventricular activity. The leadless device therefore enables therapies based on ventricular pacing and ventricular sensing, and specific stimulation may be based on specific ventricular activity (e.g., VVI mode). However, many common cardiac therapies based on ventricular pacing may require sensing in the atria of the heart (e.g., VDD mode). Detecting mechanical contractions of atrial activity in the right atrium with an accelerometer in a ventricular-placed leadless device is known. However, this is an indirect interpretation of atrial activity by sensing that mechanical signal at any distance within the beating heart. This approach therefore results in high signal processing complexity, a low signal-to-noise ratio, and a high error rate, which may result in imperfect detection of atrial events, which may be based on only a rough estimate.

[0004] In the field of lead-based systems, devices are known that use a single lead connection to the right side of the heart but incorporate multiple electrodes along the length of the lead to support signal acquisition from both the ventricles and the atria. Therefore, VDD therapy can be provided without the need to implant multiple leads. However, enabling direct electrode contact to the atria may require intentionally placing a bend in the lead during surgery so that one or more electrodes of the lead make direct contact with the inner wall. Nevertheless, contact to the atria can be unreliable due to the high fixation complexity of the lead during implantation, which also increases mechanical stress on the patient. In cardiac motion situations, the lead can easily become surrounded by blood volume, leading to unreliable sensing of atrial activity.

[0005] Furthermore, lead-based systems generally may be at a disadvantage due to known drawbacks of lead-based systems, such as a high risk of infection due to their direct physical route of access to the heart (particularly infections occurring within the chest pocket of legacy devices). Furthermore, they place a large amount of hardware into the patient that may include components that are difficult to explant and subject to mechanical failure in the harsh physiological environment in which they reside. Indeed, it is these very complexities (i.e., risk of infection and lead failure) that largely drove the emergence of leadless pacing. Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, at least in some cases, it may be advantageous to replace lead-based devices with leadless devices that offer reduced patient stress, reduced risk of infection, and reduced risk of device failure.

[0007] However, currently known techniques for leadless cardiac implants are not always optimal, particularly with respect to sensing atrial activity. Thus, there is a need for improved sensing of atrial activity. [Means for solving the problem]

[0008] According to a first aspect, the above needs are met at least in part by a leadless device for implantation in an atrium of a heart comprising a connector or fixation mechanism for connecting the device to the interior wall of the atrium and a sensor for directly sensing atrial activity of the heart. Within this description, the fixation mechanism is also referred to as the connector, and vice versa.

[0009] The concept underlying the present invention is that the device enables highly reliable determination of atrial activity compared to prior art approaches that rely on remote sensing (e.g., via an accelerometer within the ventricle). This is achieved by implanting the device in the atrium using a fixation mechanism for engaging the device with the inner wall of the atrium (or a connector for connecting the device to the inner wall of the atrium). The connector can provide a stable connection to the atrial wall so that atrial activity can be captured directly from the atrial wall and / or in close proximity to the cardiac conduction system and / or sinoatrial node. Thus, atrial activity can be measured directly at the signal source (e.g., the sinoatrial node in many supraventricular tachycardia situations as well as healthy sinus rhythm situations), minimizing the effects of external interfering signals that may be present when measuring in the ventricle and that can significantly interfere with the measurement of atrial activity. Thus, atrial activity is accurately assessed based on signals coming from the source and not simply interpreted based on indirect sensing techniques. This achieves great medical benefit because atrial activity can be used as a starting point for corresponding cardiac therapy, which is highly dependent on accurate assessment of atrial activity for the desired therapeutic outcome. For example, accurate determination of atrial activity may be necessary for supraventricular tachycardia management and / or antitachycardia pacing adjustments, e.g., as outlined below.

[0010] The fixation feature may be configured to attach the leadless device to the inner wall of the atrium, e.g., by providing a direct mechanical (e.g., physical) connection with the inner wall. The sensor may be proximate to the fixation feature such that the fixation feature can ensure direct electrical contact of the sensor to the atrium. The connector, also referred to as the fixation feature in this overview and the detailed description below, may be configured as a base mount for the leadless device that serves as a stable surgical anchor point and / or bottom surface for the leadless device when implanted in the atrium. The sensor may also be formed at the base of the leadless device. Thus, the sensor may be pressed directly by the connector against the inner wall of the atrium close to the cardiac conduction system, e.g., by the connector. The anchor point may also be referred to as the fixation point in this overview and the detailed description below.

[0011] Second, compared to prior art lead-based approaches, some of the fixation issues of atrial lead-based systems, as outlined above, can be avoided with a system like DX, particularly one that attempts to acquire signals from multiple ventricles. DX represents a unique hybrid system that combines the benefits of both single-chamber implantable cardioverter-defibrillator (ICD) systems and dual-chamber implantable cardioverter-defibrillator systems. It offers AF detection, three-channel IEGM, supraventricular tachycardia (SVT) discrimination, and atrioventricular (AV) sequential pacing like dual-chamber systems, while eliminating procedural complexity and enabling a low implant complication rate.

[0012] According to one example, the leadless device can be (or can be used as) an atrial-placed implant that supports direct measurement of SVTs (and means to terminate and / or respond to them).

[0013] According to an example, a leadless device may be configured to determine one or more PP intervals of a heart based at least in part on directly sensed atrial activity. Atrial activity often corresponds to a P-wave signal representative of atrial depolarization (i.e., the electrical signature of atrial contraction), and the PP interval is the duration between two P-waves. Using directly sensed P-waves at the signal origin to determine the PP interval has significant advantages over indirect or remote sensing approaches. For example, a sensor placed in a ventricle configured to sense atrial activity is directly affected by the high-amplitude signal of ventricular contraction (i.e., R-wave). In this case, the R-wave signal can significantly interfere with the low-amplitude P-wave signal, significantly complicating signal processing in the leadless device to determine the PP interval. Indirect approaches incur high power consumption due to high computational complexity and gain settings, ultimately resulting in a high rate of incorrectly determined or missed PP intervals. This suboptimal approach can shorten the device's lifetime and can adversely affect cardiac management, which may be based on easily corrupted input signaling. According to the present invention, it is possible to determine the PP interval using information coming directly from the signal source, thus significantly minimizing any error propagation in the subsequent evaluation of the PP interval and corresponding processing. Instead of, or in addition to, reliably determining the PP interval, the device may also be configured to reliably determine the atrial event corresponding to the PP interval based at least in part on directly sensed atrial activity.

[0014] In one example, the leadless device can be configured to determine an atrial activity state based at least in part on the determined one or more PP intervals and / or the determined one or more atrial events. The atrial activity state can represent, for example, a normal atrial activity state or a deviation (e.g., one or more PP intervals and / or number of events can deviate from expected normal values and / or ranges). The current atrial activity state can also include information that a particular state is currently active (e.g., a supraventricular tachycardia state such as an atrial fibrillation state) and / or that a particular previous state has ended (e.g., atrial fibrillation); for example, the (current) duration of the current state (and / or the duration of a previous state that has ended) and / or a counter of the number of times the state has been encountered can be included in the state.

[0015] In another example, the leadless device may be further configured to determine at least one variability in the duration of one or more PP intervals and compare the at least one variability to a setpoint. The device may be further configured to determine an atrial activity state based at least in part on variability greater than or less than a setpoint. The variability may be the difference in duration of adjacent PP intervals expressed as a percentage. For example, if a first PP interval of 1 second is followed by a second PP interval of 1.2 seconds, the variability may be defined as (1.2 seconds - 1 second) / 1.2 seconds, or approximately 17%. The determination of the atrial activity state may be based on the percentage difference in variability greater than or less than a setpoint. The setpoint may be predetermined and correspond to a statistically significant change in PP intervals, which may be associated with certain cardiac conditions, such as supraventricular tachycardia (SVT), e.g., paroxysmal supraventricular tachycardia (PSVT), atrial fibrillation (AF), or an atrial abnormality such as Wolff-Parkinson-White syndrome.

[0016] In a further example, the device may be configured to determine a predetermined number of (adjacent) PP intervals, where the variability may include the variability of two respective periods of adjacent pairs of the predetermined number of PP intervals. The leadless device may be further configured to determine an AF state as an atrial activity state if at least a minimum number of the variability of two respective periods is greater than a set value.

[0017] In this summary and the detailed description that follows, atrial activity states may also be referred to as atrial signaling or atrial events.

[0018] For example, a predetermined number of (adjacent) PP intervals may be considered a detection window containing a specific number of PP intervals (e.g., 16, 50, 100, 200, 350 intervals). For example, if five adjacent PP intervals are determined, the variability of the second PP interval compared to the first may be determined, the variability of the third PP interval compared to the second, and so on. For each of these variability, it may be checked whether it is greater than a set value. If this is the case for the variability, the detection interval may be counted. If the number of detection intervals (or variability exceeding a set value) is greater than a minimum number (which may be considered a detection limit), an AF state may be determined.

[0019] In other words, an AF state is determined when the number of PP intervals within the detection window that have a variability greater than a set value exceeds the detection limit.

[0020] In another example, a predetermined number of PP intervals may be considered as an end window. Each variation within the end window may be checked to see if it is greater than a set value. If this is the case for the variation, the end interval may be counted. If the number of end intervals (or variations exceeding the set value) is less than a maximum number (which may be considered an end limit), it may be determined that the AF state has ended. In other words, the maximum number may be considered as an end limit.

[0021] Based on the above, an AF state can be determined, as can when the AF state has ended, thereby determining the duration of the AF state. For example, after determining an AF state, successive windows may be evaluated for an ending window state. The leadless device may be configured to verify whether the duration of the AF state exceeds a predetermined threshold (e.g., a clinically relevant time, e.g., configured by a clinician at the time of implant and / or during testing) and, if so, may determine an AF episode. Data regarding the AF state and / or AF episode may be stored by the leadless device and / or communicated to an external device. If an AF episode is determined, for example, an AF episode count may be incremented and / or one or more Holter and / or ECG snapshots associated with the episode may be interrogated and stored for subsequent relay to an external device. For example, at least one snapshot at the start and / or end of the episode may be used for that purpose. In another example, if an AF state is determined, one or more snapshots may be stored and / or communicated even if an AF episode is not determined and the AF episode count is not incremented.

[0022] In some examples, the determination of an AF state and / or AF episode may also include a geminy rejection step, as further outlined herein. Gemini may be understood as a rhythm caused by atrial and / or ventricular premature contractions that manifest as a repetitive sequence of beat periods, which may be described as an irregular rhythm. This should not be mistakenly determined as an AF state. For example, the duration (within the time period used for AF state determination) during which geminy rejection was in effect could be determined. During such rejection, significant PP interval pairs are not counted if they are separated by one, two, three, or four intervals that are considered stable (i.e., the variability between the PP intervals is less than a set value). The recognition of geminy may simply terminate the AF state.

[0023] In some examples, the leadless device may also be configured to determine noise conditions to avoid falsely determining an AF state. For example, PP intervals that include a noise marker at their beginning or end are excluded from the AF detection algorithm. A noise marker may be understood as a deviation of a directly sensed signal from an expected signal shape exceeding a predetermined amount. A noise marker may also be understood as signal jitter exceeding a predetermined amount, etc. The determined AF state may further be terminated if the number of noise events (e.g., intervals with noise markers) within a noise detection window reaches an AF noise threshold.

[0024] The above technique ensures quantitative assessment of variability in multiple PP intervals. Detection or termination limits correspond to statistically significant changes in PP intervals within the detection and / or termination windows, which may be associated with specific cardiac conditions, such as atrial abnormalities such as SVT, PSVT, AF, or Wolff-Parkinson-White syndrome. Note that the maximum and minimum numbers (potential matches), set points, and predetermined numbers may be defined in a patient-specific manner.

[0025] In another example, the leadless device is further configured to evaluate / qualify atrial signaling based at least in part on motion state. In particular, the motion state corresponds to the patient's motion state despite the device being implanted in the patient's heart. The patient's motion is made available through a filtering process that screens cardiac wall motion signaling. The patient may be participating in physical activity, which may change the patient's demand for cardiac rate support to a level that is favorably matched with the intrinsic atrial rate. Considering the motion state when evaluating atrial events may be used for additional validation that the determined atrial state is appropriate or otherwise takes into account the patient's general physical activity. For example, if frequent, sporadic, or variable atrial events occur frequently and the implant reports a motion state corresponding to minimal physical activity, the atrial activity state may be considered particularly significant as a possible arrhythmia. In some examples, frequent, sporadic, or variable atrial events may be matched with a corresponding motion rate input above a predetermined threshold. In such cases, the atrial signaling is nominally consistent with the patient's rate expectations while engaged in physical activity and therefore does not inherently qualify as an arrhythmia. In some examples, the leadless device may comprise an accelerometer for determining the patient's motion state.

[0026] In further examples, the leadless device may comprise an additional sensor for sensing ventricular activity of the heart, and the leadless device may be further configured to determine atrial activity state based at least in part on the sensed ventricular activity and / or determine the clinical significance of observability of atrial signaling based at least in part on the sensed ventricular signal. In some examples, ventricular activity may be determined. For example, sensing and / or determining ventricular activity based on far-field sensing allows a secondary assessment when determining atrial activity state, which may improve the quality and / or reliability of the determination.

[0027] For example, far-field sensing may be applied as an additional screening routine that may improve the device's ability to classify problematic arrhythmias both in the atria and, to some extent, in the ventricles. In some examples, an atrial activity state may be determined. If ventricular activity is consistent with this state, the state may be confirmed as significant. Otherwise, the atrial activity state may be discarded and / or terminated. It is understood that the additional sensor may be an integral part of the atrium-implantable or implanted leadless device, i.e., a sensor element located in the ventricle may not be required.

[0028] Another example is monitoring ventricular signaling to determine whether atrial events are conducted to the ventricles. Evaluating this information in response to non-arrhythmic conditions provides a means for the device to report on the patient's atrioventricular block (AV block) status / condition. Because AV block status can change and / or deteriorate over time, statistics on conduction are collected.

[0029] In a further example, the leadless device may comprise a stimulator for directly stimulating the atria of the heart. Thus, the device may be used for combined sensing and pacing / defibrillation. The stimulator may share elements, at least in part, with the sensor (e.g., they may use the same electrodes) or the stimulator may embody separate elements of the leadless device (e.g., with separate specific electrodes). The stimulator may be designed to provide therapy output at the base of the distal tip of the leadless device and may be pressed directly against the inner wall of the atrium, e.g., by an anchoring mechanism, similar to that outlined herein for the sensor.

[0030] In a further example, the stimulator may be adapted to stimulate the atrium based at least in part on directly sensed atrial activity. Thus, the device may be configured as a pacemaker to deliver atrial pacing and atrial sensing therapy (e.g., AAI mode support). Stimulation may be based on one or more determined PP intervals, determined atrial activity states, determined AF states, and / or device motion states and / or sensed ventricular activity, as outlined above. Thus, the device configuration may enable an atrial stimulation therapy response responsive to sensed atrial activity (e.g., to treat acute arrhythmia conditions), such as to suppress SVT.

[0031] For example, if directly sensed atrial activity indicates SVT (e.g., an AF state and / or AF episode), the stimulator may be adapted to apply stimulation bursts to the atrium adapted to counteract SVT. For example, to terminate or suppress the condition, (high-rate output) non-invasive programmed stimulation (i.e., atrial NIPS) may be applied by stimulation bursts to the atrium, which may occur at a predetermined frequency or at a frequency compatible with the determined activity state of the atrium (e.g., an AF state). Stimulation may be delivered over a duration and / or at an absolute number compatible with the determined activity state. However, the duration, absolute number, and / or frequency may also be predetermined by the physician / patient at the time of implantation or during follow-up. In general, for example, in the case of high-rate tachycardias as well as in the case of noisy sensed signals, stimulation may be adapted to suppress atrial arrhythmias by attempting to override the sensed atrial signal with the applied stimulation.

[0032] Additionally or alternatively, the stimulator may be adapted to switch to a no-tracking mode (i.e., the stimulator does not track or record events) when directly sensed atrial activity is indicative of SVT (e.g., AF state and / or AF episodes). For example, in such a mode, stimulation may skip tracking certain events, e.g., atrial events. For example, based on directly sensed atrial activity by the leadless device, the leadless device may track or not track certain atrial events, e.g., paced atrial events, thereby avoiding tracking arrhythmia conditions. The stimulator may also generally inhibit or stop its output, e.g., when SVT is determined.

[0033] In one example, the leadless device may be configured to communicate with an external device (e.g., inductively coupled magnetic, acoustic / ultrasonic, conduction, impedance change, and / or optical methods) to allow for external configuration and / or data transfer without explanting the device.

[0034] In one example, the leadless device may be configured to store information based on directly sensed atrial activity. The information may be one or more determined PP intervals, a determined atrial activity state, a determined AF state, and / or a device motion state, as outlined above. Thus, the device may be further configured to determine an atrial activity state based at least in part on the device motion state. This allows the device to collect statistics over time, which a database may store (e.g., after transfer to an external device). The stored information may include Holter snapshots, ECG snapshots, and / or histograms, etc. The device may be configured to categorize the information. The device may store the information itself.

[0035] Additionally or alternatively, the device may communicate the information or classification based thereon to an external device (e.g., a patient relay device) periodically (e.g., every two weeks) or whenever communication can be established, e.g., during a medical checkup, allowing readout of the medical history and rapid assessment of the cardiac status of a patient who may be implanted with a leadless device.

[0036] Information stored by the leadless device and / or communicated to an external device can also include, for example, information regarding detected SVT events. For example, SVT events can be determined based on directly sensed atrial activity. Information can include not only a count of such events, but also the intensity and / or duration of such events. It can also include detection and / or termination (Holter and / or ECG) snapshots or parameters thereof, for example, to enable detailed post-mortem analysis of the events.

[0037] In another example, the leadless device can be configured to cooperate with at least one additional implantable leadless device. The additional implantable leadless device can be for implantation in a cardiac chamber (e.g., atrium and / or ventricle). The additional leadless device can be a device for directly stimulating and / or directly sensing the ventricle and a device for determining the activity-state of each ventricle in which it can be implanted.

[0038] In a further example, the leadless device can be configured for device-to-device communication with at least one additional implantable leadless device. The leadless device and the additional implantable leadless device can comprise a communication unit, transmitter, receiver, or transceiver to enable device-to-device communication. The communication can be based on electromagnetic waves (e.g., IR). The communication can also be based on using organic tissue (e.g., of a patient's body) as a transmission medium for communication (e.g., by galvanic-coupled intrabody communication).

[0039] For example, based on atrial activity sensed directly by the leadless device, the leadless device may communicate to a pacing device in a chamber to track or not track certain atrial events, e.g., paced ventricular events, thereby avoiding tracking of arrhythmia conditions. It may also communicate, e.g., upon determining an AF state, to switch its mode of operation, e.g., to VV mode (e.g., VVI-R) and / or (if configured as a pacing device) to adjust or cease its output. Thus, in general, the operating modes of the leadless device and further implantable leadless devices (e.g., ventricular pacing devices) may be coordinated or synchronized.

[0040] Furthermore, in (high-power) non-invasive programmed stimulation examples as outlined above, the leadless device may be configured to adapt stimulation to ventricular activity (e.g., ventricular events paced and / or sensed by at least one other leadless device when implanted as a ventricular pacemaker). However, in other examples, such adaptation may also be achieved by an optional sensor in the leadless device for sensing ventricular activity (e.g., via the far field or via an accelerometer).

[0041] Additionally or alternatively, the leadless device can be adapted to receive sensor data from at least one further implantable leadless device such that atrial activity state can also be determined by the leadless device based at least in part thereon, e.g., allowing for more reliable determination of AF state.

[0042] A second aspect relates to a system comprising a leadless device and at least one additional implantable leadless device as generally described above, where the devices in the system may be configured as generally described above.

[0043] In one example, a system may be configured to determine an atrial activity state based on sensory inputs from multiple leadless devices included in the system. For example, the system may determine an atrial activity state and / or an AF state based on (directly) sensed activity in two or more chambers, e.g., atrial activity and ventricular activity. This approach may also consider the atrial response in the chambers, thereby increasing reliability and reducing erroneously determined atrial activity states and / or AF states.

[0044] In one example, the system may be configured to determine atrial activity state and / or AF state as outlined above in a cooperative manner (e.g., in a distributed manner) across multiple leadless devices, e.g., by dividing algorithms and / or method steps across devices of the system.

[0045] Additionally or alternatively, in one example, at least one further implanted leadless device of the system may be adapted as a pacemaker to stimulate a ventricle based at least in part on directly sensed atrial activity and / or based at least in part on direct atrial stimulation (if present). This enables a wide range of cardiac therapies that cannot be implemented solely by atrial stimulation, e.g., VVI mode, VDD mode, DDD mode, etc. The system may be configured, among other things, to coordinate the ventricular stimulation (tracking) response with the sensed atrial activity and / or atrial stimulation. For example, the ventricular-placed device may be switched to a non-tracking mode, e.g., VVI mode, based on the sensed atrial activity and / or atrial stimulation, and the system may adapt (e.g., terminate) the atrial stimulation accordingly. This may be useful, for example, if the atrial-placed device detects an AF condition.

[0046] Additionally, the additional implantable leadless device itself need not be part of a system with an atrial-placed device as outlined herein, but may appear as a separate part of the invention.

[0047] A third aspect relates to a method for determining atrial activity-state of a heart using at least one leadless device implanted in an atrium of a heart. The method may include determining, by the device, one or more PP intervals of the heart by directly sensing atrial activity of the heart. It may further include determining, by the device, at least one variability in duration of one or more PP intervals and comparing, by the device, the at least one variability to a set value. The method may further include determining, by the device, the atrial activity-state based at least in part on the at least one variability being greater than or less than the set value.

[0048] In one example, the method may be used to determine, classify and / or report AV block conditions.

[0049] A fourth aspect relates to a computer program comprising instructions for implementing the method as outlined above when the instructions are executed by a computer. In one example, the computer program instructions may be stored on a non-transitory medium. For example, the computer program may be stored on a leadless device or on a device within a system described herein, which may include means for executing the computer program instructions. The computer program allows for autonomous, automated implementation of the aspects described herein, which may result in minimal technical intervention from medical staff and patients.

[0050] It should be noted that method steps described herein may include all aspects described herein even if not explicitly set forth as method steps, but rather with reference to an apparatus (or device). Further, devices outlined herein may include means for performing all aspects outlined herein, even if described in the context of a method step.

[0051] The functions described herein, whether described as method steps, computer programs, and / or means, may be implemented in hardware, software, firmware, and / or combinations thereof. If implemented in software / firmware, the functions may be stored on or transmitted as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media, including any medium that facilitates transfer of a computer program from one place to another. Storage media may be any available medium that can be accessed by a general-purpose or special-purpose computer. By way of example, and not limitation, such computer-readable storage media may comprise RAM, ROM, EEPROM, FPGA, CD / DVD or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer or a general-purpose or special-purpose processor. A control unit as described herein may also be implemented in hardware, software, firmware, and / or combinations thereof, e.g., by one or more general-purpose or special-purpose computers and / or general-purpose or special-purpose processors. [Brief explanation of the drawings]

[0052] [Figure 1] 1 is a schematic diagram of an exemplary embodiment of a system according to the present invention; [Figure 2] 1 is a schematic diagram of an exemplary embodiment of the method according to the invention; DETAILED DESCRIPTION OF THE INVENTION

[0053] FIG. 1 shows a schematic diagram of an exemplary system S according to the present invention.

[0054] The system S may comprise a leadless device 100 according to the invention. The leadless device 100 may be implanted in an atrium A of a heart (e.g., in an atrium A of a human heart). The leadless device 100 may be specifically configured for implantation, for example, in the right atrium of a patient.

[0055] The leadless device 100 can include a fixation mechanism 110 to mechanically connect the leadless device 100 to the interior wall of atrium A. The connector 110 can be configured as a base mount for the leadless device 100, which can serve as a surgical fixation point during the implant procedure. The connector 110 can include one or more fixation teeth and / or anchor structures and / or threaded fixation mechanisms to enable a stable and reliable connection to atrium A.

[0056] The leadless device 100 may further comprise a sensor 120. The sensor 120 may be configured to directly sense atrial activity. Direct sensing of atrial activity can infer that all sensor elements are located within the atrium, thereby capturing any atrial signals directly, i.e., as opposed to remote sensing (e.g., by a sensor within the ventricle). In particular, the sensor 120 may be in direct contact with the inner wall of atrium A such that an electrical connection is established. The sensor 120 may be configured to sense electrical signals within atrium A that may be present at the inner wall of atrium A. The sensor 120 may include a conductive material that may be formed by an electrode (e.g., a cathode or an anode). Thus, the sensor 120 may directly sense atrial activity by capturing electrical signals from the inner wall of atrium A. In particular, the sensor 120 may be positioned near the cardiac conduction system to enable sensing as close as possible to the source of the atrial activity. Thus, the sensor 120 may directly measure the cardiac P wave, which corresponds to atrial depolarization. The sensor 120 or its electrodes may have a coating (e.g., by zinc plating), a texture (with sized porosity), and / or a particular shape (e.g., a thread shape, a flat circular shape, etc.), which may be optimized with respect to the characteristics of the inner wall of the atrium A to ensure well-functioning sensing contact for sensing low-amplitude atrial activity signals.

[0057] The sensor 120 can be near the connector 110, for example, on the bottom surface of the leadless device 100. Thus, the sensor 120 can be pressed directly by the connector 110 against the interior wall of atrium A to ensure stable, persistent, and reliable contact of the sensor 120 with its sensing medium or input signal source.

[0058] In one example, the sensor 120 and connector 110 can share elements, thus enabling mechanical anchoring and sensing functions of the leadless device 100 through a single structural element, e.g., an electrode that also serves to mechanically couple the leadless device 100 at least in part to the wall of atrium A.

[0059] In one example, sensor 120 can also be configured to sense signals from a ventricle V of the heart to indirectly measure ventricular activity (e.g., far-field sensing). In other examples, leadless device 100 can comprise an additional sensor (not shown in FIG. 1 ) for sensing and / or determining ventricular activity. The additional sensor can share one or more elements with sensor 120, e.g., an electrode. The additional sensor can be part of (integral with) leadless device 100 (e.g., located in an atrium).

[0060] The leadless device 100 may further comprise a stimulator 130. The stimulator 130 may be configured to apply electrical stimulation to the interior wall of atrium A. The stimulator 130 may be configured to deliver a specific amount of electrical energy to atrium A. The stimulator 130 may be connected to power electronics that can provide a defined energy for stimulation, for example, in the form of stimulation bursts. The stimulation may be for cardiac pacing and / or defibrillation purposes. The stimulator 130 may also have electrodes that provide, for example, direct electrical connection to the atrium wall, as outlined above with reference to the sensor 120. The stimulator 130 and sensor 120 may share one or more electrodes and / or have separate electrodes.

[0061] The amount of electrical energy delivered by the stimulator 130 may be adjustable. For example, the electrical energy may be delivered in the form of pulses with adjustable energy and / or adjustable pulse timing or frequency. For example, the electrical energy and / or pulses may be determined by the leadless device 100 or the system S in response to directly sensed atrial activity.

[0062] The leadless device 100 can further comprise a battery 140 that can serve as a power source for the leadless device 100. The battery 140 can have a slightly smaller form factor compared to batteries used in devices implanted in the ventricles due to the small size of the atria.

[0063] The leadless device 100 may include an activity sensor 150 that can be used to sense and determine the device's motion state (e.g., activity state). The activity sensor 150 may be implemented by or include an accelerometer and / or a piezoelectric sensor that detects body vibrations.

[0064] The leadless device may further comprise a control unit 160. The control unit 160 may be at least one computational unit (e.g., a microprocessor, microcontroller, embedded system, electronic circuit, etc.) that may implement computational instructions. The control unit 160 may control various device elements based on configurations that may be defined by the computational instructions (e.g., by a computer program running on the control unit 160). The control unit 160 may be connected to the various device elements outlined above via several input / output ports for respective electrical signaling and control. The control unit 160 may have its own memory and / or be coupled to a separate memory that may be included in the leadless device 100.

[0065] Control unit 160 may be coupled to stimulator 130 and / or the power electronics of stimulator 130, and specific signaling of control unit 160 may effect a desired stimulation output onto atrium A of the heart via stimulator 130. Thus, control unit 160 may control the stimulation output within atrium A, which may be based on several input factors that may be processed and analyzed by control unit 160. As an example, the paced output may be in response to a determined atrial activity state, such as an AF state, to suppress an arrhythmia condition.

[0066] For example, control unit 160 may be coupled to sensor 120 to receive its raw sensory input, which may be far-field signals of directly sensed atrial and / or ventricular activity. Control unit 160 may then use its computing power to process the sensory input. Thus, based on atrial and / or ventricular sensed input, control unit 160 may enable leadless device 100 to determine a particular cardiac condition, which may be the basis for a particular stimulation output, e.g., for therapeutic reasons. To this end, control unit 160 may analyze directly sensed atrial activity signals to determine one or more PP intervals and / or their variability. Signatures other than PP intervals may also be used for the analysis. Methods that may be implemented in a computer program that may execute on control unit 160 are described in more detail below with respect to FIG. 2.

[0067] The system S optionally includes an additional leadless device 200 according to the invention, shown in dashed lines in FIGURE 1. The additional leadless device 200 can be implanted in a ventricle V of a heart (e.g., ventricle V of a human heart). The leadless device 200 can be specifically configured, for example, for implantation in a patient's right ventricle.

[0068] The additional leadless device 200 may comprise device elements that may be generally similar to those described herein for the leadless device 100. In particular, the additional leadless device 200 may comprise a connector 210, a sensor 220, a stimulator 230, a battery 240, an activity sensor 250, and / or a control unit 260. Because the additional leadless device 200 may be implanted in a cardiac chamber, its device elements may have features configured for a cardiac chamber. If the cardiac chamber is a larger chamber than the atrium, the general form factor of the additional leadless device 200 may be larger than that of the atrial-placed leadless device 100. For example, the battery 240 may be larger than the battery 140, which may correspond to an overall larger leadless device 200. Other device elements may similarly have similar or larger form factors compared to corresponding elements of the leadless device 100 (e.g., connector 210, sensor 220, stimulator 230, activity sensor 250, etc.).

[0069] Furthermore, sensor 220 may be optimized to sense ventricular activity directly by capturing electrical signals from the inner wall of ventricle V. Sensor 220 may be positioned close to the cardiac conduction system to enable sensing as close as possible to the source of ventricular activity. Thus, sensor 220 may directly measure cardiac R waves corresponding to ventricular polarization, from which additional leadless device 200 may determine one or more RR intervals. Additional leadless device 200 may be optimized to sense relatively high amplitude ventricular activity (compared to relatively low amplitude atrial activity). In particular, the range of ventricular activity signals may be three to six times larger than the range of atrial activity signals, and sensors 120 and 220 and / or corresponding control units 160 and 260 may be adapted accordingly (e.g., with respect to analog-to-digital conversion, etc.). Thus, in general, additional leadless device 200 may be configured differently compared to leadless device 100 to account for the different requirements for processing sensed ventricular activity signals. Sensor 220 or its electrodes may have material properties (e.g., those outlined with reference to sensor 120) that may be optimized with respect to the properties of the inner wall of ventricle V to ensure well-functioning sensing contact in order to directly sense high amplitude ventricular activity signals.

[0070] The leadless device 100 and additional leadless devices 200 of the system S may be configured to cooperate with one another. For example, the devices may enable combinations of therapy modes resulting from direct pacing and / or sensing in the atria and direct pacing and / or sensing in the ventricles (e.g., VD mode (e.g., VDD), AD mode (e.g., ADD), DD mode (e.g., DDD), etc.). The devices may be configured to apply coordinated stimulation therapy outputs with or without inter-device communication. For example, the devices may determine the activity state of the stimulation output of each other chamber and / or each other device based on their respective far-field sensing and adjust their respective stimulation outputs. Thus, far-field sensing may provide a link for coordinated therapy modes without requiring inter-device communication means.

[0071] In one example, the leadless device 100 and the additional leadless devices 200 of a system S may be configured for device-to-device communication. Thus, the system S allows for the exchange of data to share independently sensed activity or determined data (e.g., activity states). For example, the system S may determine a signature, which may be based on directly sensed activity in the atria and / or ventricles, which may be used to determine an atrial activity state, e.g., an SVT condition such as AF. For example, the additional leadless device 200 may communicate directly sensed ventricular activity and / or a state determined therefrom to the leadless device 100. Similarly, the leadless device 100 may directly communicate sensed atrial activity and / or a state determined therefrom to the additional leadless device 200. Additionally or alternatively, each of the devices 100 and 200 may communicate commands, e.g., regarding the pacing activity of the respective other device, based on, e.g., directly sensed activity and / or a state determined therefrom by the respective devices 100 and 200.

[0072] Thus, multi-chamber assessment may be more reliable and reduce erroneously determined atrial activity states. Classification algorithms and / or methods for determining atrial activity states, such as signatures or AF states, may be performed in a distributed manner by devices (100, 200) in system S. Statistical control of the system's data (e.g., determined activity states, clinical signatures) may also be processed and / or stored in a distributed manner.

[0073] The system S also enables a reliable triggering mechanism to stop therapy output attempting to track atrial activity (or atrial activity state). This may take the form of stopping (or throttling) the leadless device 100's own output (e.g., atrial pacing) while signaling additional leadless devices 200 to "mode switch" to a non-tracking therapy state (e.g., VVI(R) mode). This may avoid adverse tracking conditions in the heart that may result from AF.

[0074] The system S (or just the leadless device 100) may be further configured to actively suppress SVT via the leadless device 100. It may support routines that can deliver electrical stimulation to the atria, e.g., non-invasive programmed stimulation (NIPS). The routines may be delivered at a user-selected frequency, at a frequency that may be based on a determined atrial activity state (e.g., AF state), or at a fixed frequency applied uniformly to all patients. Atrial stimulation may be based on ventricular stimulation and / or far-field assessment of ventricular activity that may correspond to a ventricular activity state, as outlined herein.

[0075] 2 shows a schematic diagram of an exemplary method 300 according to the invention for determining atrial activity state of a heart. The method may be implemented by a leadless device 100 implanted in an atrium of a heart, for example by the control unit 160 of the leadless device 100.

[0076] As a starting point, method 300 may include determining 310, by the device, one or more PP intervals (PP cycle lengths) of the heart by directly sensing atrial activity of the heart. Control unit 160 may be configured to run an interval detection algorithm over the directly sensed atrial activity, which may determine the period between two adjacent P waves of the heart. PP interval detection may be based on a rising edge or a falling edge, or on reaching a certain threshold.

[0077] Subsequently, the method 300 may include determining 320, by the device, at least one variability in the duration of one or more PP intervals. The variability may be expressed as a percentage of change between adjacent PP intervals, as outlined herein. The variability may be interpreted as a figure of merit for the regularity or irregularity of adjacent atrial beats.

[0078] Subsequently, the method 300 may include comparing 330, by the device, the at least one variability to a set value, which may be expressed as a predetermined PP variability limit against which the actual (determined) variability of adjacent PP intervals is compared.

[0079] Subsequently, the method 300 may include determining 340, by the device, an atrial activity-state based at least in part on the at least one variation being greater than or less than a set value.

[0080] In particular, the setpoint may be selected to be the maximum deviation of the atrial heart rate that can be considered stable. If the setpoint is exceeded, the deviation may be a significant PP deviation associated with an atrial abnormality such as SVT, PSVT, AF, or Wolff-Parkinson-White syndrome. For example, the setpoint may be within a range of 5% to 20%. The setpoint may be selected to account for measurement tolerances and reduce false positives.

[0081] Determining 320 at least one variability in the duration of one or more PP intervals may further include determining the variability of a plurality of PP intervals within a detection window. The detection window may include a plurality of consecutive PP intervals forming a detection window length. For example, a corresponding particular atrial activity state may be determined only if a plurality of significant PP deviations exist within the detection window. For example, the detection window length may be within a range of 16 to 350 intervals.

[0082] Specifically, the method 300 may further include determining an AF state if a minimum number of significant PP intervals is determined within the detection window. If so, the overall variation may be considered significant. A significant PP interval may also be referred to as a detection interval. In particular, the method may include incrementing a detection interval counter by 1 for each detected significant PP interval. After analyzing the detection window, an AF state may be determined if the counter exceeds the minimum number of detection intervals. The minimum number of detection intervals may be in the range of 2 to 250 intervals, which may depend on the selected detection window length.

[0083] In some examples, AF status may not be determined after analyzing a single detection window. Instead, a certain number (e.g., consecutive) of detection windows may be required to meet the above criteria before AF status is determined. For example, the certain number of detection windows may be in the range of 1 to 50 detection windows. This number may depend on the length of the detection window.

[0084] The leadless device 100 may be configured to periodically and / or continuously initiate the detection algorithm and / or method 300. For example, it may analyze one or more detection windows at predetermined intervals.

[0085] Because AF may resolve, it may be necessary to further determine the termination of the AF state, which may result in the atrial cardiac rhythm mode changing to a "normal" activity state in the absence of AF. This may also be useful for assessing the effectiveness of actions applied by the leadless device 100 and / or system S in response to determining the AF state to counteract the AF state. Thus, determining 320 at least one variability in the duration of one or more PP intervals may further include determining the variability of multiple PP intervals in a termination window. The termination window may include multiple consecutive PP intervals forming a termination window length. For example, the termination window length may be in the range of 16 to 350 intervals.

[0086] Specifically, method 300 may further include terminating the AF state if the maximum number of significant PP intervals is not exceeded within the termination window. If so, the overall variation may be considered insignificant. A significant PP interval may also be referred to as a termination interval. In particular, method 300 may include incrementing a termination interval counter by 1 for each detected significant PP interval. After analyzing the termination window, if the counter falls below the maximum number of termination intervals, the AF state may be terminated. The maximum number of termination intervals may be in the range of 1 to 80 intervals, which may depend on the selected termination window length.

[0087] In some instances, the AF state may not be terminated after analyzing a single termination window. Instead, a specific number of (e.g., consecutive) termination windows may be required to meet the above criteria before the AF state is terminated. For example, the specific number of termination windows may be in the range of 1 to 50 detection windows.

[0088] The AF status determination outlined above may be turned on or off by the clinician, for example, at the time of implant and / or during follow-up.

[0089] In one example, the method 300 may include considering various AF sensitivity levels when determining an AF state. The AF sensitivity levels may be predetermined as low, medium, or high, or may be user-adjustable. The AF sensitivity level may be based on a set of parameters associated with the method. For example, one set may include a particular setting value, a particular detection window length, a particular number of detection / termination intervals, and / or a particular number of detection / termination windows, which may be associated with a particular AF sensitivity level as an overall setting. For example, this approach may cover the detection / termination of an AF state across a wide range of statistical deviation types. For example, one setting may easily detect short periods with large amounts of deviation, while another setting may easily detect infrequent deviations that can progress over a long period of time.

[0090] The method 300 may also include setting an AF confirmation time, for example, by a clinician at implant and / or during follow-up. This may be a time period representing a clinically relevant period of AF activity. If the duration of the AF state exceeds the AF confirmation time, a clinical AF episode may be determined and an AF episode counter may be incremented. Information about the clinical AF episode may be stored for statistics in the leadless device 100, which may be performed by the control unit 160. The information may include one or more Holter snapshots that may be acquired during the duration of the clinical AF episode. The confirmation time may be adjustable, with a value ranging from 1 to 30 minutes. Note that information about determined AF states (e.g., Holter snapshots) that do not indicate a clinical AF episode may also be stored.

[0091] The method 300 may further include gemini rejection, which may be turned on or off (e.g., by a clinician) when determining an AF state. It may further include adjusting gemini rejection sensitivity. Gemini refers to a rhythm caused by premature atrial or ventricular contractions, which may appear as a repetitive sequence of beat periods. The resulting irregular rhythm pattern may be erroneously determined as AF, e.g., an erroneously determined AF state. When enabled, gemini rejection may be active for a defined gemini rejection time during the AF confirmation time. During the gemini rejection time, the system S may not determine an AF state if a pair of PP intervals separated by one, two, three, or four intervals can be considered stable for an atrial heartbeat as described herein. For example, if the variability of a pair of PP intervals separated by one interval is below a set value, the system may not determine an AF state even if adjacent PP intervals meet the AF state criteria. In this case, the respective gemini criteria may be determined to be met. The gemini rejection interval separation may be adjusted, for example, by a clinician as part of the gemini sensitivity setting. The method may apply gemini screening after determining AF status as a verification of atrial activity status. If gemini status is determined during gemini screening, the AF status may then be terminated. The gemini rejection time may be in the range of 1 to 10 minutes, which may depend on the configured AF confirmation time.

[0092] In one example, method 300 may screen for noise to avoid erroneous determination of an atrial activity state, such as an AF state. Cardiac intervals that may contain noise markers (e.g., characteristic visual noise) at their beginning or end may be excluded from the method / algorithm for determining an atrial activity state. If the number of noise events during the AF noise window reaches an AF noise threshold, determination of an AF state may further be terminated. The AF noise threshold may be configured as a percentage (e.g., a minimum) of the number of PP intervals that may be used to determine an AF state. As an example, if the number of upper (lower) PP intervals that may determine (terminate) an AF state is 10, a 50% noise threshold may indicate that an AF state may be determined (terminate) if a maximum of five noise intervals are detected within the detection window and / or between significant PP intervals. The AF noise threshold may be adjustable within a range of 10% to 75% or may be turned off. The AF noise window may be a set amount of time during which noise-based termination may be active. It may be within a range of 0.5 to 2 minutes or may be specifically configured as an AF confirmation time.

[0093] In one example, the method 300 can further include determining a "no motion" condition that can be based on sensed activity from the activity sensor 150. "No motion" can be a device motion state corresponding to little or no motion of a patient with the leadless device 100 implanted in the patient's heart. If the "no motion" condition can be associated with directly sensed atrial activity, an atrial activity state, and / or an AF state, validation can be added that the signaling is not the result of motion.

[0094] In one example, method 300 may further include assessing far-field ventricular activity. The assessment may be based on the R-R interval of the ventricular R wave and may apply an algorithm to determine a ventricular signature (e.g., ventricular activity-state). When an atrial activity-state can be determined, it may be compared with corresponding assessed far-field activity and / or ventricular signature, which may serve as additional confirmation of the determined (or terminated) atrial activity-state.

[0095] The far-field checks outlined above and the "no motion" checks may be applied separately or in combination.

[0096] As outlined in detail herein, leadless device 100 (and / or leadless device 200) may also comprise a stimulator for directly stimulating the atria (and / or ventricles), and stimulation may be based on directly sensed atrial activity and / or conditions determined at least in part thereon. It is understood, therefore, that method 300 may also include corresponding method steps for stimulation by any of the techniques outlined herein.

[0097] Method 300 may also be performed by a system S comprising leadless device 100 and additional leadless devices 200. For example, the method may be performed essentially by leadless device 100. However, leadless device 100 may, for example, additionally take into account ventricular activity sensed directly by the additional leadless devices 200 (e.g., instead of assessing far-field ventricular activity as outlined above). This can be highly advantageous when determining atrial activity state, since it does not require indirect assessment based on potentially noisy far-field signals with high signal processing complexity. Also, leadless device 100 may not only react to the results of the method for determining activity state itself, but may additionally or alternatively communicate instructions to the additional leadless devices 200 as outlined above.

[0098] Consequently, method 300 is not limited to intra-atrial leadless device 100 and may be augmented by one or more additional leadless devices when implanted in the patient's heart. Also, method 300 need not be essentially performed solely by leadless device 100. Instead, the method may be performed in a distributed manner, for example, between each control unit 160, 260. Thus, the computational effort when performing the method may be shared, which may be beneficial for efficient use of selectively available computing power. The method when performed by system S may further comprise assessing "no motion" based on intra-atrial activity sensor 150 and / or intra-ventricular activity sensor 250, which may serve as a dual authentication in the presence of physical motion.

Claims

1. A leadless device (100) for implantation in the atrium (A) of the heart, wherein the leadless device (100) is A connector (110) for connecting the device to the inner wall of the atrium (A), A sensor (120) for directly sensing the atrial activity of the aforementioned heart, A leadless device (100) equipped with [a specific feature].

2. The device is configured to determine one or more P-P intervals of the heart, at least partially based on the directly sensed atrial activity. The leadless device according to claim 1.

3. The device is configured to determine the atrial activity state based at least partially on one or more P-P intervals determined. The leadless device according to claim 2.

4. The device described above, Determine at least one variation of the one or more P-P interval periods, Compare the at least one of the aforementioned fluctuations with a set value, The atrial activity state is further configured to be determined at least partially based on the at least one variation that is greater than or less than the set value, The leadless device according to claim 3.

5. The aforementioned P-P interval includes a predetermined number of adjacent P-P intervals, The aforementioned variation includes the variation in each of the two adjacent pairs of P-P intervals, If at least the minimum number of the aforementioned fluctuations in each of the two periods is greater than the aforementioned set value, the leadless device (100) is configured to detect the AF state. The leadless device according to claim 4.

6. The device is further configured to determine the atrial activity state, at least partially based on the motion state of the device. The leadless device according to claim 3.

7. The device further comprises additional sensors for sensing the ventricular activity of the heart, and the leadless device (100) is further configured to determine the atrial activity state based at least in part on the sensed ventricular activity. The leadless device according to claim 3.

8. The leadless device further comprises a stimulator (130) for directly stimulating the atrium (A) of the heart. The leadless device according to claim 1.

9. The stimulator (130) is adapted to stimulate the atrium (A) at least partially based on the directly sensed atrial activity. The leadless device according to claim 8.

10. If the directly detected atrial activity indicates supraventricular tachycardia, the stimulator (130) is adapted to apply a stimuli burst adapted to counteract the supraventricular tachycardia to the atrium (A) and / or to switch to non-tracking mode. The leadless device according to claim 9.

11. The device is configured to cooperate with at least one further implantable leadless device (200). A leadless device (100) according to any one of claims 1 to 10.

12. The leadless device (100) and, The at least one further implantable leadless device (200) according to claim 11, A system (S) equipped with the following features.

13. The at least one further implantable leadless device (200) is adapted as a pacemaker that stimulates the ventricle (V) at least partially based on the directly sensed atrial activity. The system according to claim 12.

14. A method (300) for determining the atrial activity state of a heart using at least one leadless device (100) implanted in the atrium (A) of the heart, wherein the method (300) The device determines one or more P-P intervals of the heart by directly sensing the atrial activity of the heart (310), The device performs the step (320) of determining at least one variation of the period of the one or more P-P intervals, The device performs the step (330) of comparing the at least one variation with a set value, The device determines the atrial activity state (340) at least partially based on the at least one variation that is greater than or less than the set value, A method including (300).

15. A computer program comprising an instruction that, when executed by a computer, carries out the method according to claim 14.

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