Implantable medical devices for providing diagnostic and / or therapeutic cardiac functions within a patient

Abstract

An implantable medical device (2) for providing diagnostic and / or therapeutic cardiac functions in a patient (P) comprises a sensing arrangement for sensing electrocardiogram signals, a communication circuit (24) for data communication with a device (3) external to the patient (P), and a processing circuit (22) for processing the sensed electrocardiogram signals (S2). The processing circuit (22) is configured to identify the performance of a threshold test measurement (TT) by the implantable pacemaker device (1) and to trigger the transmission of information related to said threshold test measurement (TT) to the device (3) external to the patient (P).

Description

[Technical field]

[0001] The present invention relates generally to implantable medical devices, implantable therapeutic systems, and methods of operating implantable medical devices for providing diagnostic and / or therapeutic cardiac functions within a patient. [Background technology]

[0002] In general, an implantable medical device comprises a sensing arrangement for sensing electrocardiogram signals, a communication circuit for communicating data with equipment external to the patient, and a processing circuit for processing the sensed electrocardiogram signals.

[0003] An implantable medical device of the type to which this specification relates may be, for example, an implantable cardioverter defibrillator (ICD), which may be particularly configured for parenteral implantation outside the patient's heart.

[0004] Within the implantable therapy system, multiple implantable medical devices may be implanted in the patient, for example, in the form of an implantable cardioverter defibrillator along with a pacemaker device such as a leadless pacemaker. The devices of the implantable therapy system herein are in communication with external devices, for example, in a home monitoring system, such that information relating to the devices of the implantable therapy system may be communicated to the external devices and relayed via the external devices, for example, to a home monitoring service center, for evaluation, for example, by a physician.

[0005] Within an implantable therapy system, some devices may be implanted deeper into the patient than others. Additionally, some devices, such as leadless pacemaker devices, may be small in size and therefore may include only a relatively small battery with limited energy storage capacity, making them particularly energy efficient in operation.

[0006] Techniques exist for establishing an intrabody communication network to enable communication between devices in an implanted therapeutic system. However, intrabody communication technologies impose fairly strict compatibility restrictions on the implanted medical devices, requiring that the implanted medical devices interact in a prescribed manner.

[0007] In other approaches, communication with implantable medical devices deeply embedded in a patient may involve low frequency communication techniques employing, for example, coil telemetry communication, however this requires the use of a reading device that must be in close proximity to the patient's exterior to establish data transmission, making communication potentially unreliable and cumbersome for the user.

[0008] EP 2327609 describes an acoustic communication link between implanted medical devices for exchanging information between the implanted medical devices. The acoustic communication link is established to enable wireless communication between the implanted medical devices, and transmission parameters such as sensitivity and carrier frequency can be adapted to improve the existing communication link.

[0009] US Patent Application Publication No. 2010 / 0022836 discloses a multi-directional transmitter for an intrabody device, such as an implantable device. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] European Patent No. 2327609 [Patent Document 2] US Patent Application Publication No. 2010 / 0022836 Summary of the Invention

[0011] It is an object of the present invention to provide an implantable medical device, an implantable therapeutic system, and a method of operating an implantable medical device that allows for easy and reliable monitoring and information transmission related to the device, which may be deeply implanted in a patient.

[0012] This object is achieved by an implantable medical device having the features of claim 1.

[0013] In one aspect, an implantable medical device for providing diagnostic and / or therapeutic cardiac functions within a patient comprises a sensing arrangement for sensing electrocardiogram signals, a communication circuit for data communication with patient-external equipment, and a processing circuit for processing the sensed electrocardiogram signals, the processing circuit being configured to identify performance of a threshold test measurement by the implantable pacemaker device and to cause transmission of information related to said threshold test measurement to the patient-external equipment.

[0014] The implantable medical device may be an implantable non-transvenous defibrillation device, which is configured to emit a shock pulse to achieve defibrillation. An implantable non-transvenous defibrillation device, also called a non-transvenous implantable cardiac defibrillator (in short, a non-transvenous ICD), may serve to monitor and treat potentially life-threatening cardiac arrhythmias in a patient. An implantable non-transvenous defibrillation device is configured for non-transvenous implantation, i.e., implantation in which the electrode lead is not implanted intravenously in the patient's (human or animal) heart. Thus, an implantable non-transvenous defibrillation device should be implanted in a patient such that the generator and the electrode configuration, for example the shock electrode placed on the lead connected to the generator, are implanted outside the heart and do not reach the patient's heart, i.e., the right or left ventricle or the right or left atrium.

[0015] In one embodiment, the implantable non-transvenous defibrillation device comprises a lead to be implanted outside the heart and a shock electrode disposed on the lead. The shock electrode herein is placed outside the patient's heart, for example in the patient's sternum area, in the implanted state of the defibrillation device, so that a shock pulse to achieve defibrillation is generated outside the heart. Generally, the implantable non-transvenous defibrillation device does not include a portion that extends intravenously into the heart, but the defibrillation device is configured to achieve sensing and emission of signals outside the heart.

[0016] In another embodiment, the implantable medical device is an implantable monitoring device, such as, for example, a rhythm monitoring device configured for subcutaneous implantation in a patient. In yet another embodiment, the implantable medical device is a recording device, such as an implantable loop recorder, or an implantable sensor device.

[0017] The implantable medical device comprises a sensing arrangement for sensing electrocardiogram signals. The sensing arrangement may comprise, for example, one or multiple pairs of electrode posts through which electrocardiogram signals may be sensed and transferred to a processing circuit operably connected to the sensing arrangement.

[0018] The processing circuitry is configured to process the sensed electrocardiogram signal, and the processing circuitry may be generally configured to, for example, identify within the sensed electrocardiogram signal a stimulation event caused by the implantable pacemaker device. Thus, the implantable medical device is programmed to derive information from the sensed electrocardiogram signal about another implantable device, i.e., the implantable pacemaker device, that is separate and independent from the implantable medical device.

[0019] The implantable pacemaker device may in particular be a leadless pacemaker device that is implanted directly into the patient's heart, for example the right or left ventricle, and does not include leads carrying electrodes.

[0020] In particular, the processing circuitry of the implantable medical device is configured to identify the performance of a threshold test measurement by the implantable pacemaker device, for example by identifying a stimulation event based on a sensed electrocardiogram signal related to the threshold test measurement performed by the implantable pacemaker device, and to trigger the transmission of information related to the threshold test measurement to a patient-external device. Thus, the implantable medical device is operable to obtain information related to the threshold test measurement performed by the implantable pacemaker device and to communicate such information to the external device.

[0021] Generally, an implantable pacemaker device, such as a leadless pacemaker device, implanted within a patient's heart is operable to perform a threshold test measurement in which a threshold is determined for obtaining so-called capture when injecting a stimulation signal into cardiac tissue. During operation, the implantable pacemaker device outputs a stimulation pulse to cause pacing of the patient's heart. The stimulation pulse herein must have an amplitude and pulse width such that it delivers sufficient energy to effectively induce stimulation of conductive structures of the patient's heart such that the stimulation pulse causes a desired pacing event, in particular an atrial or ventricular contraction event. If the amplitude and / or pulse width of the stimulation pulse is too small, a so-called loss of capture may occur, in which the stimulation pulse does not result in a subsequent pacing event.

[0022] In order to determine at what amplitude and / or pulse width a stimulation pulse should be output to reliably obtain capture, so-called threshold test measurements are performed by the implantable pacemaker device, during which, for example, test pulses at varying amplitudes are output by the implantable pacemaker device and, based on such test pulses, the implantable pacemaker device determines a pulse amplitude threshold at which reliable stimulation can be achieved (e.g., assuming a fixed pulse width) and below which reliable stimulation is not observed.

[0023] The implantable pacemaker device may be configured to perform threshold test measurements at regular intervals, for example, once a day or twice a day. Herein, the threshold test measurements should preferably be performed by the implantable pacemaker device when the patient is at rest and has a stable low heart rate. Thus, for example, the threshold test measurements may be performed by the implantable pacemaker device during the night when the patient is likely to be asleep.

[0024] An implantable medical device, particularly one that may be implanted outside the heart, may establish a monitoring function for the implantable pacemaker device when the implantable medical device is configured to monitor the implantable pacemaker device to obtain information regarding threshold test measurements performed by the implantable pacemaker device and to communicate information related to the threshold test measurements to an external device. Thus, information regarding the operation of the implantable medical device, particularly regarding the performance of threshold test measurements, may be monitored by the implantable medical device and communicated by the implantable medical device to the external device. In this manner, data related to the operation of the implantable pacemaker device to perform threshold test measurements is obtained using the implantable medical device and communicated by the implantable medical device to the external device, thus making direct data communication between the implantable pacemaker device and the external device largely unnecessary.

[0025] Therefore, in principle, the implanted pacemaker device does not need to establish (direct) communication with an external device and thus the implanted pacemaker device can operate in a particularly energy-efficient manner.

[0026] Monitoring of the operation of the implantable pacemaker device to perform the threshold test measurements herein may be reliably established even when the implantable pacemaker device is deeply implanted in the patient, thus potentially making direct data communication of the implantable pacemaker device to an external device difficult. If monitoring of the implantable pacemaker device when performing threshold test measurements is performed by the implantable medical device based on sensing electrocardiogram signals, no data transmission is required from the implantable pacemaker device to an external device communicating information regarding the measured thresholds in order to generate a stimulation signal, and thus the deeply implanted state of the implantable pacemaker device does not affect the data communication.

[0027] When the external device receives information regarding the threshold test measurements performed by the implantable pacemaker device, the external device may record and analyze results of the threshold test measurements performed by the implantable pacemaker device. When the information regarding the threshold test measurements performed by the implantable pacemaker device is obtained using an implantable medical device that senses signals related to the threshold test measurements performed by the implantable pacemaker device, direct data communication does not need to be established between the implantable pacemaker device and the implantable medical device, and between the implantable pacemaker device and the external device, and no specific patient interaction is required to obtain the threshold test measurement results.

[0028] In one embodiment, the implantable medical device is configured to identify a stimulation event caused by the implantable pacemaker device based on the sensed electrocardiogram signal. Within a routine operation, the implantable medical device records an electrocardiogram signal, processes the sensed electrocardiogram signal, and based on the processing, a stimulation event related to a threshold test measurement performed by the implantable pacemaker device can be identified, and information about the stimulation event can be derived and transmitted to an external device. Since the identification of a stimulation event related to a threshold test measurement does not require direct communication between the implantable pacemaker device and the implantable medical device, the requirement of device compatibility can be ignored. Thus, for example, monitoring of the implantable pacemaker device can be established even in a scenario where the implantable pacemaker device and the implantable medical device are from different manufacturers.

[0029] In one embodiment, the processing circuit is configured to store a portion of the sensed electrocardiogram signal related to the threshold test measurement and transmit the stored portion of the sensed electrocardiogram signal to a patient-external device. When the implantable medical device identifies that the implantable pacemaker device is to perform a threshold test measurement (e.g., when a stimulation event output by the implantable pacemaker device is identified in the course of the implantable pacemaker device performing a threshold test measurement), the signal portion related to the threshold test measurement may be stored and communicated to the external device, such that the signal portion indicative of the threshold test measurement is forwarded to the external device for further processing.

[0030] In one embodiment, the processing circuit comprises a circular buffer for circularly storing the sensed electrocardiogram signal. The circular buffer, also called a ring memory, may have a storage capacity for storing signal portions of a specified time length, for example, in the range between 10 seconds and 5 minutes, in particular between 20 seconds and 1 minute. The circular buffer herein circularly overwrites its memory content such that at any time the circular buffer contains signal portions of a specified preceding time span.

[0031] If it is identified that the implantable pacemaker device is performing a threshold test measurement, the processing circuitry may cause the transmission of a data message containing a number of stimulation events indicative of test pulses output by the implantable pacemaker device during the threshold test measurement. Thus, as a result of the identification of the threshold test measurement, a signal portion is extracted from the circular buffer and transferred to the external device, and an electrocardiogram signal indicative of the threshold test measurement is then transmitted to the external device. In particular, the signal portion communicated to the external device may include test pulses output by the implantable pacemaker device during the threshold test measurement to determine a stimulation threshold below which reliable stimulation by the stimulation pulses may be achieved but below which reliable stimulation is not observed.

[0032] Alternatively or additionally, the processing circuitry may be configured to analyze stimulation events indicative of test pulses output by the implantable pacemaker device during the threshold test measurement and to communicate information regarding the identified stimulation threshold to a patient-external device. In particular, the processing circuitry may be configured to derive the value of the stimulation threshold determined by the implantable pacemaker device during the threshold test measurement by processing sensed electrocardiogram signals indicative of stimulation events induced by the implantable pacemaker device. The implantable medical device may then communicate the actual value of the stimulation threshold to the external device.

[0033] In one embodiment, the processing circuit is configured to count stimulation events indicative of test pulses output by the implantable pacemaker device during a threshold test measurement to determine a stimulation threshold identified by the implantable pacemaker device in the course of the threshold test measurement. When the processing circuit identifies that the implantable pacemaker device is performing a threshold test measurement, the processing circuit may observe how many test pulses are output by the implantable pacemaker device. In particular, the implantable pacemaker device may be programmed to output a specified sequence of test pulses to determine the stimulation threshold, the specified sequence being generally known to the implantable medical device. Within the sequence, the implantable pacemaker device may, for example, begin by outputting a test pulse with a defined starting amplitude, and starting from the starting amplitude, may successively reduce the amplitude of the test pulse by adopting a defined scheme known to the implantable medical device. When the implantable pacemaker device finds that a test pulse of a particular amplitude does not result in an evoked response (e.g., a ventricular contraction following the emission of the test pulse), but rather in a so-called loss of capture, the (larger) amplitude of the preceding test pulse may be considered to correspond to the threshold. The manner in which the implantable pacemaker device is programmed to vary the amplitude of the test pulses is known to the implantable medical device, so that based on counting the test pulses it can be determined how many test pulses were output by the implantable pacemaker device before the measurement by the pacemaker device was terminated, and from there it can be concluded what the measured threshold was. This value can then be communicated by the implantable medical device to the external device.

[0034] In one embodiment, the processing circuit is configured to determine the timing of the stimulation events to identify at least one backup pulse output by the implantable pacemaker device following a preceding test pulse, and to draw a conclusion based on the occurrence of the at least one backup pulse with reference to a stimulation threshold identified by the implantable pacemaker device in the course of a threshold test measurement. For example, during a threshold test measurement, the implantable pacemaker device may generate output test pulses with progressively decreasing amplitudes. If no subsequent evoked response is detected for the test pulse, this may be identified by the pacemaker device as a capture loss, and the implantable pacemaker device may then be programmed to output a so-called backup pulse to ensure that stable pacing of the patient's heart is established. The backup pulse is generally output following a preceding test pulse at a predefined timing interval, e.g., between 50 ms and 150 ms, e.g., 100 ms, such that the processing circuitry of the implantable medical device can identify, based on observing the timing between two subsequent stimulation events, that a first stimulation event corresponds to a test pulse and that a second stimulation event, which immediately follows the first stimulation event at a predefined timing, corresponds to a backup pulse. If the pacemaker device is programmed to output a backup pulse only in the event of capture loss, based on the occurrence of the backup pulse, it can be determined whether a capture loss has been obtained at the pacemaker device for the test pulse, and based thereon, information regarding the stimulation threshold measured by the implantable pacemaker device can be derived.

[0035] In one embodiment, the processing circuit is configured to identify the performance of a threshold test measurement by the implantable male pacemaker device based on recognition of a predefined pulse pattern output by the implantable pacemaker device during the performance of the threshold test measurement. For example, the implantable pacemaker device may be programmed to output test pulses and / or backup pulses according to a predefined pattern, e.g., at a specific timing, during the performance of the threshold test measurement. The pattern may be made known to the implantable medical device, so that the processing circuit of the implantable medical device may identify that the implantable pacemaker device is performing a threshold test measurement by observing the specific pulse pattern output by the implantable pacemaker device. Based on the identification, the processing circuit may then record an electrocardiogram signal related to the threshold test measurement performed by the implantable pacemaker device, or process a sensed signal to derive information regarding the threshold test measurement performed by the implantable pacemaker device.

[0036] In one embodiment, the implantable pacemaker device may be configured to output a test pulse and / or a back-up pulse at the start of a threshold test measurement according to a predefined signal analysis sequence at the start phase of the threshold test measurement.

[0037] Within the signal analysis sequence, a test pulse of relatively large amplitude may be output according to a predefined pulse pattern to assess whether an evoked response has been reliably obtained. Alternatively or additionally, pairs of pulses may be output by the implantable pacemaker device according to a predefined pulse pattern within the signal analysis sequence, with each pair containing one test pulse and a subsequent backup pulse, the backup pulse serving to verify that polarization artifacts are small enough to distinguish capture from non-capture. Thus, the processing circuitry of the implantable medical device may be configured to identify a particular pulse pattern for the signal analysis sequence at the start of a threshold test measurement to determine that the implantable pacemaker device is beginning a threshold test measurement.

[0038] In one embodiment, the processing circuitry is configured to identify the performance of a threshold test measurement by the implantable pacemaker device based on a programmed time at which the implantable pacemaker device is programmed to perform the threshold test measurement. For example, the implantable pacemaker device may be programmed to periodically perform a threshold test measurement at a predefined time, such as 2:00 a.m. each day. This time may be made known to the implantable medical device such that the processing circuitry of the implantable medical device may be configured to record and / or process signals sensed at the predefined time corresponding to the time of performance of the threshold test measurement to derive information regarding the threshold test measurement performed by the implantable pacemaker device.

[0039] In one embodiment, the processing circuitry is configured to trigger a data communication message to the patient-external device based on identifying performance of a threshold test measurement by the implantable pacemaker device. Thus, in an event-based approach, data communication may be initiated, for example, upon identifying a threshold test measurement.

[0040] Alternatively or additionally, the information related to the threshold test measurements may be included in a data message transmitted by the implantable medical device according to a predefined periodic communication scheme. The implantable medical device may, for example, be configured to periodically send a data message to the external device. Such a periodic message may also include the information related to the threshold test measurements.

[0041] The implantable therapy system, in one embodiment, comprises an implantable pacemaker device that generates cardiac stimulation signals to achieve intracardiac pacing, and an implantable medical device of the type described above. The implantable pacemaker device may, for example, be a leadless pacemaker device that is implanted directly in the heart, for example in the right or left ventricle or right or left atrium. The pacemaker device may, for example, provide a therapy for pacing the patient's heart and thus pacing the heart rate to a desired normal heart rate when bradycardia is detected. Alternatively or additionally, the pacemaker device may provide a therapy for restoring the heart rate to a desired normal rate when tachycardia is detected.

[0042] In another aspect, a method for operating an implantable medical device to provide diagnostic and / or therapeutic cardiac functions within a patient includes sensing electrocardiogram signals using a sensing configuration of the implantable medical device, and processing the sensed electrocardiogram signals using processing circuitry of the implantable medical device, the processing including identifying performance of a threshold test measurement by the implantable pacemaker device and causing transmission of information related to the threshold test measurement to equipment external to the patient.

[0043] The benefits and advantageous embodiments explained above for the implantable medical device and the implantable treatment system apply equally to the present method, and so reference is made to the above in this regard.

[0044] The inventive idea will now be explained in more detail with reference to embodiments shown in the drawings. [Brief description of the drawings]

[0045] [Figure 1] FIG. 1 is a schematic diagram of a treatment system for a medical device implanted in a patient. [Diagram 2] 1 shows a schematic diagram of an implantable medical device with an implantable pacemaker device. [Diagram 3]1 shows a schematic diagram of the starting phase of a threshold test measurement performed by an implantable pacemaker device. [Figure 4] FIG. 2 shows a schematic sequence of an example of threshold test measurements performed by an implantable pacemaker device.

[0046] Next, embodiments of the present invention will be described in detail with reference to the drawings, in which like reference numbers indicate like structural elements.

[0047] It should be noted that the embodiments do not limit the present invention but merely represent illustrative examples.

[0048] 1, in a therapeutic system setup, an implantable leadless pacemaker device 1 is implanted in a (human or animal) patient's heart H. The leadless pacemaker device 1 is implanted directly in the heart H, for example the right ventricle RV, to couple to tissue within the heart H and thus sense cardiac signals within the heart and emit stimulation signals to the cardiac tissue.

[0049] Moreover, the implantable medical device 2 in the form of a non-transvenously implantable defibrillator is implanted such that the implantable medical device 2 is entirely outside the heart H. The non-transvenously implantable medical device 2 comprises a generator 20 enclosed in a housing and a lead 21 connected to the generator 20 and carrying sensing electrodes 211, 212 as well as a shock electrode 213 in the form of a coil formed at a distal portion of the lead 21. The sensing electrodes 211, 212, for example formed as ring electrodes on either side of the shock electrode 213, serve to sense cardiac signals for processing in the generator 20 of the implantable medical device 2, so that based on the sensed signals, for example, tachycardia can be identified and a shock pulse can be generated to provide anti-tachycardia therapy.

[0050] In a setup as shown in Fig. 1, the pacemaker device 1 implanted in the heart H and the implantable medical device 2 implanted outside the heart H each include a sensing circuit, and based on processing of the sensed signals in the respective device 1, 2, a therapeutic action may be initiated. Each device 1, 2 here functions in principle independently of the other devices 2, 1, and thus, by the pacemaker device 1 implanted in the heart H, a stimulation signal may be generated, for example, to overcome bradycardia, whereas by the defibrillator device 2, a shock pulse may be issued, for example, to restore a tachycardial heart rate to a normal heart rate.

[0051] In the setup as shown in Fig. 1, the implantable pacemaker device 1 is implanted in the heart H and thus quite deep within the patient P. In contrast, the implantable medical device 2 with the generator 20 may be implanted, for example subcutaneously. The leads 21 extend from the generator 20 outside the heart H and thus do not reach intravenously into the heart H. The implantable medical device 2 is configured to establish a communication link L to the external device 3 so that data communication can take place between the implantable medical device 2 and the external device 3.

[0052] The external device 3 may, for example, be part of a home monitoring system. The external device 3 is beneficially present at the patient P's location, such as at home, and is connected to a home monitoring service center such that data can be relayed by the external device 3 to and from the home monitoring center.

[0053] 2, the pacemaker device 1 comprises a housing 10 in which an electrode arrangement 11 having electrode posts 110, 111 is disposed. The electrode posts 110, 111 form a pair of electrodes by which stimulation pulses can be injected into tissue and sensing signals can be received from tissue to provide stimulation and sensing at the implantation site of the implantable pacemaker device 1. The implantable pacemaker device 1 further comprises a control circuit 12 and a battery 13 providing energy storage, both of which are enclosed in the housing 10.

[0054] The parenterally implantable medical device 2 includes within a generator 20 a processing circuit 22 , a battery 23 for providing energy storage, and a communication circuit 24 .

[0055] The processing circuitry 22 processes signals received via the sensing electrodes 211, 212 of the sensing arrangement and is responsible for triggering a stimulation effect, for example by issuing a shock pulse via the shock electrode 213, if a tachycardia is detected.

[0056] A communication link L (see FIG. 1) to the external device 3 is established by the communication circuitry 24. The communication circuitry 24 is configured to establish communication, for example, according to the MICS protocol, the ISM protocol, the BLE protocol, the Zigbee protocol, or another communication scheme.

[0057] The pacemaker device 1 and the non-intravenously implantable medical device 2 do not function in instant connection with each other in the illustrated embodiment, i.e., the pacemaker device 1 and the implantable medical device 2 do not have a data connection with each other, and thus no control signals are exchanged between the pacemaker device 1 and the implantable medical device 2.

[0058] Rather, the pacemaker device 1 functions without knowledge of the presence of the implantable medical device 2, for example, by sensing electrocardiogram signals within the heart H and emitting a stimulation signal S1 based on processing of the sensed signals. The pacemaker device 1 may be configured, for example, to detect bradycardia and, if bradycardia is detected, to emit a stimulation pulse to cause a stimulation event Vp.

[0059] 1 and 2, the pacemaker device 1 is not in direct communication with the external device 3. To nevertheless provide monitoring of the operation of the pacemaker device 1, the implantable medical device 2 is configured to identify a stimulation event Vp caused by the pacemaker device 1 in the sensed electrocardiogram signal S2.

[0060] For example, to distinguish the stimulation pulse of the implantable pacemaker device 1 from an intrinsic electrocardiogram signal resulting from cardiac activity, the sensed electrocardiogram signal S2 may be processed in the processing circuit 22 of the generator 20 of the implantable medical device 2, for example by applying digitization, amplification, and filtering. For example, the processing circuit 22 may process the sensed electrocardiogram signal S2, for example by determining the flank slope or flank height, evaluating the positive or negative flank of the pulse, or by applying pattern recognition techniques, to identify a predefined pulse shape resulting from the stimulation pulse emitted by the pacemaker device 1.

[0061] In one embodiment, processing circuit 22 comprises a circular buffer 220 that serves to circularly store sensed electrocardiogram signal S2 such that a portion of sensed electrocardiogram signal S2 relating to a previous time span is always retained in memory and is circularly overwritten by new data. For example, circular buffer 220 may be configured to retain signal portions in memory for a time span between 10 seconds and 5 minutes, e.g., between 20 seconds and 1 minute, such that the most recent signal portions are always stored in circular buffer 220.

[0062] The processing circuitry 22 is configured to derive information from the sensed electrocardiogram signal S2 relating to the operation of the pacemaker device 1. The processing circuitry 22 is thus operable to enable monitoring of the operation of the pacemaker device 1 based solely on receipt of the electrocardiogram signal S2 and by evaluating the operation of the pacemaker device 1 according to the sensed electrocardiogram signal S2. Based on the monitoring of the operation of the pacemaker device 1, data may be transmitted to the external device 3 to effect monitoring of the operation of the pacemaker device 1.

[0063] Specifically, referring now to Figures 3 and 4, the implantable pacemaker device 1 is configured to perform a threshold test measurement TT, an example of which is shown in Figure 4, in order to determine a stimulation threshold for the pulse amplitude of a stimulation pulse. Thus, a stimulation pulse having an amplitude above the threshold is highly likely to induce cardiac stimulation, in particular ventricular contraction, whereas a stimulation pulse having an amplitude below the threshold does not reliably cause cardiac stimulation.

[0064] For example, the implantable pacemaker device 1 may be configured to perform a threshold test measurement TT periodically, once a day or twice a day, for example at a programmed time when the patient P can be considered to be at rest, for example at night, for example at 2:00 a.m. daily. In the course of a threshold test measurement TT, a test pulse TP is generated and output by the implantable pacemaker device 1, and an evoked response ER is observed to determine whether a test pulse TP at a particular amplitude induces a contraction and thus corresponds to capture.

[0065] 1, the implantable medical device 2 is configured to observe stimulation events Vp corresponding to test pulses TP and / or so-called back-up pulses BP output by the implantable pacemaker device 1 when performing a threshold test measurement TT. When the implantable medical device 2 identifies that the pacemaker device 1 is currently performing a threshold test measurement TT, the processing circuit 22 may store a signal portion relating to the threshold test measurement TT in the circular buffer 220 and may communicate such signal portion to the external device 3. Alternatively or additionally, the processing circuit 22 may process the electrocardiogram signal S2 sensed during the threshold test measurement TT performed by the implantable pacemaker device 1 and derive information regarding the threshold test measurement TT performed by the implantable pacemaker device 1 from the stimulation events Vp corresponding to the test pulses TP and / or back-up pulses BP in the course of the threshold test measurement TT.

[0066] The implantable medical device 2 may determine that the implantable pacemaker device 1 is performing the threshold test measurement TT, for example, based on the programmed time at which the implantable pacemaker device 1 is programmed to perform the threshold test measurement TT and which is also known to the implantable medical device 2. For example, if the implantable pacemaker device 1 is programmed to perform the threshold test measurement every morning at 2:00 AM, the implantable medical device 2 may sense a signal at the programmed time and may record and / or process the sensed signal to communicate information regarding the threshold test measurement TT to the external device 3.

[0067] In another embodiment, the implantable medical device 2 may determine that the implantable pacemaker device 1 is performing a threshold test measurement TT based on identifying a predefined signal pattern for the threshold test measurement TT, for example a signal pattern for the start phase of the threshold test measurement TT at which the implantable pacemaker device 1 outputs a signal analysis array SA as shown diagrammatically in FIG. 3 .

[0068] In an initiation phase preceding the performance of the actual threshold test measurement TT, the implantable pacemaker device 1 may, for example, output test pulses TP and backup pulses BP of a predefined pattern to evaluate whether or not a threshold test measurement TT should be performed.

[0069] During the signal analysis sequence SA, the implantable pacemaker device 1 may, for example, in the first phase A1, output a sequence of test pulses TP, for example with a predefined signal amplitude corresponding to a programmed starting value that should reliably result in an evoked response ER, in order to evaluate whether the test pulses TP actually result in an evoked response ER corresponding to a cardiac contraction evoked by the test pulses TP. The implantable pacemaker device 1 outputs pairs of pulses in the subsequent second phase A2, each pair including a test pulse TP and a backup pulse BP, the backup pulse BP following the test pulse TP by a predefined timing interval, for example 100 ms. The test pulses TP in the second phase A2 may have a pulse amplitude that corresponds to the amplitude of the test pulses TP during the first phase A1, so as to reliably evoke an evoked response ER by the test pulses TP. The backup pulses BP in the second phase A2 serve to evaluate so-called polarization artifacts and in particular to ensure that the polarization artifacts are small enough to distinguish capture from capture loss.

[0070] The pulse pattern or a part of the pulse pattern shown in Fig. 3 and output as the initial signal analysis sequence SA in the starting phase of the threshold test measurement TT can be observed and identified by the implantable medical device 2 based on the processing of the electrocardiogram signal S2. In particular, in the electrocardiogram signal S2, the processing circuit 22 of the implantable medical device 2 can identify the stimulation events Vp corresponding to the test pulses TP and / or pairs of pulses TP, BP output during different phases A1, A2 of the initial starting phase. If a certain pattern is identified according to the pulses of the sensed electrocardiogram signal S2, the implantable medical device 2 can conclude that the implantable pacemaker device 1 is about to start the threshold test measurement TT and can therefore start recording the electrocardiogram signal S2 for the subsequent threshold test measurement TT.

[0071] Referring now to FIG. 4, during the actual threshold test measurement TT, the implantable pacemaker device 1 generates test pulses TP with progressively decreasing pulse amplitudes to evaluate whether the test pulses TP (still) result in capture based on the evoked response ER.

[0072] 4, an initial test pulse TP1 may be generated by the implantable pacemaker device 1, for example, at a starting amplitude value of 3.0 V. When a subsequent evoked response ER1 is sensed by the implantable pacemaker device 1 indicating capture, a second test pulse TP2 is generated at a reduced amplitude of 2.4 V, after which the evoked response ER2 is also sensed. The pulse amplitude is now progressively decreased in increments of 0.6 V (a test pulse TP3 of 1.8 V resulting in an evoked response ER3, a test pulse TP4 of 1.2 V resulting in an evoked response ER4, and a test pulse TP5 of 0.6 V) until no evoked response is observed by the implantable pacemaker device 1 after test pulse TP5.

[0073] To ensure that stable pacing of the patient is obtained during the threshold test measurement, a backup pulse BP is output following test pulse TP5 at a predefined timing interval, e.g., 100 ms, and at a predefined pulse amplitude, e.g., corresponding to the starting amplitude value of test pulse TP1, thereby inducing a contraction.

[0074] Subsequently, another test pulse TP6 of the same amplitude (0.6V) as test pulse TP5 is output, after which again no evoked response is sensed and another back-up pulse BP is output.

[0075] A test pulse TP6 of the same amplitude as test pulse TP5 is output to assess whether the capture loss of test pulse TP5 was potentially false. Since test pulse TP6 also does not result in an evoked response, the pulse amplitude is now increased back to the value of the last successful test pulse TP4, a test pulse TP7 of 1.2V is output, and then the evoked response ER7 is sensed. Now the pulse amplitude is progressively reduced in 0.1V increments to generate test pulses TP8, TP9, TP10 of amplitudes 1.1V, 1.0V, 0.9V, respectively. Test pulses TP8, TP9 evoke evoked responses ER8, ER9, and thus each results in capture, whereas test pulse TP10 does not result in an evoked response, and then a backup pulse BP is output. Further test pulses TP11, TP12 of 0.9 V are then generated and output by the implantable pacemaker device 1, each test pulse TP11, TP12 eliciting an evoked response ER11, ER12, such that a pulse amplitude of 0.9 V is deemed to still result in reliable capture (a test pulse of a particular amplitude is repeated a maximum of three times, and capture is deemed to be obtained if two of the three test pulses result in an evoked response).

[0076] Now a test pulse TP13 of reduced amplitude of 0.8 V is output, followed by a backup pulse BP since test pulse TP13 does not result in an evoked response, and another test pulse TP14 of 0.8 V also does not result in an evoked response (and is therefore followed by a backup pulse BP), so the threshold is still deemed to be at 0.9 V, which corresponds to the amplitude of test pulses TP10-TP12 that resulted in successful capture.

[0077] According to the threshold value thus determined, the amplitude of the stimulation pulse for the subsequent device operation is then set by adding to the threshold value a predefined safety margin, which in the illustrated example is equal to 0.5 V. The amplitude of the stimulation pulse during the subsequent operation of the pacemaker device 1 thus corresponds to 1.4 V, which is verified by the test pulse TP15 and which results in a corresponding evoked response ER15.

[0078] The implantable medical device 2 observes and monitors, according to the sensed electrocardiogram signal S2, a pulse sequence corresponding to a threshold test measurement TT as shown in the example of Figure 4. The implantable medical device 2 may record a portion of the electrocardiogram signal S2 corresponding to the threshold test measurement TT and may communicate such signal portion to the external device 3.

[0079] Alternatively or additionally, the implantable medical device 2 may process the sensed electrocardiogram signal S2 in the context of a threshold test measurement TT performed by the implantable pacemaker device 1. For example, the implantable medical device 2 may process the electrocardiogram signal S2 to determine stimulation events Vp in the electrocardiogram signal S2 related to the test pulses TP1...TP15 and to derive the thresholds determined by the implantable pacemaker device 1 during the threshold test measurement TT.

[0080] For processing, the processing circuit 22 of the implantable medical device 2 may be configured, for example, to count the test pulses TP1...TP15. Since the implantable medical device 2 is informed of the specific scheme that the implantable pacemaker device 1 follows to vary the pulse amplitude of the test pulses TP1...TP15, by counting the test pulses TP1...TP15 it can be identified at which test pulse the measurement stopped and thus it can be derived what the measured threshold value is.

[0081] In this specification, the implantable medical device 2 may further identify a backup pulse BP output by the implantable pacemaker device 1 following a test pulse TP that does not result in an evoked response. During a threshold test measurement TT, the backup pulse BP is output only if the test pulse TP does not result in an evoked response, and based on the backup pulse BP, it may be determined when the implantable pacemaker device 1 changes the test pulse from a 0.6 V step change to a 0.1 V step change and when the test sequence has ended.

[0082] In one embodiment, the processing circuit 22 is configured to trigger the transmission of information to the external device 3 based on the identification of the threshold test measurement TT. For example, if a threshold test measurement TT is performed by the implantable pacemaker device 1 and correspondingly identified in the electrocardiogram signal S2 by the implantable medical device 1 or according to a programmed execution time, a signal portion containing the stimulation event Vp corresponding to the threshold test measurement TT and the test pulse and backup pulse output therein can be transmitted to the external device 3 in a data message. The external device 3 thus obtains information regarding the threshold test measurement TT performed by the pacemaker device 1.

[0083] Based on the identification of the threshold test measurement TT, the implantable medical device 2 may trigger data communication with the external device 3 .

[0084] In event-based communication, for example, the implantable medical device 2 may trigger a communication message in response to an event, such as the identification of a threshold test measurement performed by the pacemaker device 1. A data message is then created based on the detection of the event and transmitted to the external device 3 using the communication circuitry 24.

[0085] Additionally or alternatively, information relating to the pacemaker device 1 may be included in a data message transmitted to the external device 3 according to a regular, pre-defined communication scheme, in which, for example, data messages are exchanged between the implantable medical device 2 and the external device 3 in a regular, pre-scheduled manner. Thus, the identification of a threshold test measurement performed by the pacemaker device 1 does not, for example, cause the immediate triggering of a specific dedicated communication message, but information regarding the operation of the pacemaker device 1 is included in the regular communication messages, for example to give periodic reports.

[0086] The inventive concept is not limited to the embodiments described above but may be embodied in entirely different ways.

[0087] The implantable medical device may in particular be an implantable cardioverter defibrillator (ICD). In another embodiment, the implantable medical device may be a monitoring device, such as a so-called biomonitor, which is implanted, for example subcutaneously in close proximity to the heart, for sensing and monitoring signals, but does not itself perform a therapeutic function by emitting a stimulation signal. [Explanation of symbols]

[0088] 1. Pacemaker devices 10. Housing 11 Electrode configuration 110, 111 Electrode pillar 12 Control circuit 13 Energy storage unit (battery) 2. Non-intravenous defibrillation devices 20. Generator 21 Lead 211, 212 Sensing electrode 213 Shock Electrodes 22 Processing circuit 220 Circular Buffer 23 Energy storage unit (battery) 24 Communication Circuits 3 External equipment A1, A2 phase BP Backup Pulse ER, ER1..ER13 evoked reaction H Heart L Communication Link P patient SA Signal Analysis Array S1 stimulus signal S2 Sensed signal TP, TP1...TP13 Test Pulses TT Threshold test measurement Vp stimulation event

Claims

1. An implantable medical device (2) for providing diagnostic and / or therapeutic cardiac functions within a patient (P), comprising: a sensing arrangement for sensing an electrocardiogram signal; a communication circuit (24) for data communication with a device (3) external to the patient (P); a processing circuit (22) for processing the sensed electrocardiogram signal (S2), the processing circuit (22) being configured to identify the performance of a threshold test measurement (TT) by the implantable pacemaker device (1) and to trigger transmission of information related to the threshold test measurement (TT) to the device (3) external to the patient (P); An implantable medical device (2).

2. 2. The implantable medical device (2) of claim 1, wherein the implantable medical device (2) is an implantable non-intravenous defibrillator configured to emit shock pulses to achieve defibrillation.

3. 3. The implantable medical device (2) of claim 2, characterized in that the implantable non-intravenous defibrillation device comprises a lead (21) to be implanted outside the heart and a shock electrode (213) arranged on the lead (21).

4. 4. The implantable medical device (2) of claim 1, wherein the processing circuit (22) is configured to store a portion of the sensed electrocardiogram signal (S2) related to the threshold test measurement (TT) and to transmit the stored portion of the sensed electrocardiogram signal (S2) to the device (3) external to the patient (P).

5. 5. The implantable medical device (2) of claim 4, wherein the processing circuit (22) comprises a circular buffer (220) for circularly storing the sensed electrocardiogram signals (S2).

6. 5. The implantable medical device (2) of claim 4, characterized in that the portion includes a signal portion containing a number of stimulation events (Vp) indicative of test pulses (TP) output by the implantable pacemaker device (1) during the threshold test measurement.

7. 4. The implantable medical device (2) of claim 1, wherein the processing circuit (22) is configured to analyze a number of stimulation events (Vp) indicative of test pulses (TP) output by the implantable pacemaker device (1) during the threshold test measurement and to communicate information regarding the identified stimulation thresholds to the device (3) external to the patient (P).

8. 4. The implantable medical device (2) according to claim 1, wherein the processing circuit (22) is configured to count stimulation events (Vp) indicative of test pulses (TP) output by the implantable pacemaker device (1) during the threshold test measurement (TT) in order to determine a stimulation threshold identified by the implantable pacemaker device (1) in the course of the threshold test measurement (TT).

9. 4. The implantable medical device (2) of claim 1, wherein the processing circuit (22) is configured to determine a timing of a stimulation event (Vp) in order to identify at least one backup pulse (BP) output by the implantable pacemaker device (1) following a preceding test pulse (TP), and to determine a stimulation threshold identified by the implantable pacemaker device (1) in the course of the threshold test measurement (TT) based on the occurrence of the at least one backup pulse (BP).

10. 4. The implantable medical device (2) of claim 1, wherein the processing circuit (22) is configured to identify the performance of a threshold test measurement (TT) by the implantable pacemaker device (1) based on recognition of a predetermined pulse pattern output by the implantable pacemaker device (1) during the performance of the threshold test measurement (TT).

11. 4. The implantable medical device (2) according to claim 1, wherein the processing circuit (22) is configured to identify the performance of a threshold test measurement (TT) by the implantable pacemaker device (1) based on recognition of pulses of a predetermined pulse pattern output by the implantable pacemaker device (1) during a signal analysis sequence (SA) at the start phase of the threshold test measurement (TT).

12. 4. The implantable medical device (2) of claim 1, wherein the processing circuit (22) is configured to identify the performance of the threshold test measurement (TT) by the implantable pacemaker device (1) based on a programmed time at which the implantable pacemaker device (1) is programmed to perform the threshold test measurement (TT).

13. An implantable therapeutic system comprising an implantable pacemaker device (1) for emitting cardiac stimulation signals to achieve intracardiac pacing, and an implantable medical device (2) according to any one of claims 1 to 3.

14. 14. The implantable therapeutic system of claim 13, wherein the implantable pacemaker device (1) is a leadless pacemaker device.

15. 1. A method for operating an implantable medical device (2) for providing diagnostic and / or therapeutic cardiac function in a patient (P), comprising: sensing an electrocardiogram signal using a sensing arrangement of the implantable medical device (2); processing the sensed electrocardiogram signal (S2) using a processing circuit (22) of the implantable medical device (2), the sensed electrocardiogram signal (S2) including identifying the performance of a threshold test measurement (TT) by the implantable pacemaker device (1) and causing transmission of information related to the threshold test measurement (TT) to the device (3) external to the patient (P); A method comprising:

Images