Implant and method of operating same

Abstract

The invention describes an implant (1) having a measuring unit (18) for measuring a predefined physiological signal, in particular a blood pressure signal. To initiate the measurement of a physiological signal such as blood pressure at an appropriate time point, the implant (1) further comprises an accelerometer unit (20) and a processing unit (12), wherein the accelerometer unit (20) is configured to determine a plurality of acceleration data according to a predefined time scheme within predefined first time period and to transmit it to the processing unit (12), wherein the processing unit (12) is configured to determine a time-dependent activity index (AI) based on the received plurality of acceleration data and to provide an initiation signal at its interface (24) with the measuring unit (18) at a time point automatically selected on the basis of the determined time-dependent AI, the initiation signal being to trigger a measurement of the predefined physiological signal. Further, a respective operating method of such implant, a computer program product and a computer readable data carrier is disclosed.

Description

[0001] Applicant: BIOTRONIK SE & Co. KG

[0002] Date: 04.12.2025

[0003] Our Reference: 22.243P-WO

[0004] IMPLANT AND METHOD OF OPERATING SAME

[0005] The invention relates to an implant and a method of operating the same.

[0006] An implant or implantable medical device is an active or passive implantable medical device, for example, a pacemaker (with leads), an Implantable Cardiac Monitor (ICM), an Implantable Leadless Pacer (ILP), an Implantable Leadless Pressure Sensor (ILPS), an Implantable Cardiac Defibrillator (ICD) or a Subcutaneously Implanted Cardiac Defibrillator (S-ICD), a device that delivers spinal cord stimulation (SCS), deep brain stimulation (DBS) or neurostimulation. Such medical devices collect physiological signals in order to monitor the health status of the patient and / or to deliver a therapy to the patient, for example using electromagnetic waves. They may be implanted within different organs and body cavities such as the vasculature of the patient (i.e. intravascular implants).

[0007] Implantable pressure sensors which measure blood pressure in patient’s body are known, for example, the CardioMEMS® HF system (Abbott) and similar implants. The known system may be implanted in the pulmonary artery to measure the blood pressure. In this regard, US 2024 / 389868 Al discloses an automatic pressure sensing system for measuring in stressful situations. US 10376159 B2 discloses a blood pressure system with an implant and an additional pressure sensor. US 6236882 Bl describes implantable monitoring devices capable of providing ECGs.

[0008] To ensure comparability, it is important to measure blood pressure or another physiological signal while the patient rests or sleeps. For this it is known to set a measurement time via a telemetry interface that needs a communication of the set time to the implant from an external device. Alternatively, fixed measuring times are used. Both known possibilities are not very reliable and may produce incorrect results as they’ll be not flexible if the patient’s daily habits change or the patient travels. Setting a measurement time further requires patient’s or health care practitioner’s (HCP’s) initiative.

[0009] Accordingly, there is the need to provide an implant and a respective procedure that automatically initiates the measurement of a physiological signal such as blood pressure at an appropriate instant of time.

[0010] The above object is solved by the implant having the features of claim 1, by the method of operating such implant having the features of claim 9 as well as by a respective computer program product and computer readable data carrier.

[0011] In particular, the object is solved by an implant, and in particular one implant, having a measuring unit for measuring a predefined physiological signal, in particular a blood pressure signal, wherein the implant further comprises an accelerometer unit and a processing unit, wherein the accelerometer unit is configured to determine a plurality of acceleration data according to a predefined time scheme within predefined first time period and to transmit it to the processing unit, wherein the processing unit is configured to determine a time-dependent activity index (Al) based on the received plurality of acceleration data and to provide an initiation signal at its interface with the measuring unit at a time point automatically selected on the basis of the determined time-dependent Al , the initiation signal being to trigger a measurement of the predefined physiological signal. According to the invention the triggered measurement of the predefined physiological signal shall take place at minimal physical activity. Moreover, the processing unit calculates a timedependent activity index (Al) and predicts minimal physical activity after the first time period. Further, the processing unit is configured to determine a second time period before and / or during the triggered measurement of the predefined physiological signal. Also, the accelerometer unit is configured to determine a plurality of acceleration data according to a predefined time scheme within the predefined second time period and to transmit it to the processing unit. The processing unit is configured to determine a time-dependent activity index (Al) based on the received plurality of acceleration data of the first and the second time period or the second period alone. The processing unit is further configured to provide an initiation signal at its interface with the measuring unit at a time point automatically

[0012] 22.243P-WO | 04.12.2025 selected on the basis of the determined time-dependent Al, the initiation signal being to trigger a measurement of the predefined physiological signal at predefined physiological status, in particular at minimal physical activity. In that, the processing unit is configured to determine a time-dependent activity index (Al) based on the activity data of the first time period and the second time period, confirming by the additional data of the second time period that - at the time when the measurement of the predefined physiological signal is triggered - the measurement takes place at a status of minimal activity. Alternatively or additionally, the processing unit is configured to determine a time-dependent activity index (Al) based on the activity data of the first time period, to provide an initiation signal at its interface with the measuring unit at a time point automatically selected on the basis of the determined time-dependent Al, the initiation signal being to trigger a measurement of the predefined physiological signal at a predefined physiological status, in particular at minimal activity, and further configured to initiate a second time period of measuring physical activity during the measurement of a predefined physiological signal in order to determine a time-dependent activity index (Al) based on the activity data of the second time period. In case the time-dependent activity index (Al) during the second time period confirms a predefined physiological status, such as minimal physical activity, the measurement of the physiological signal is determined valid. In case the time-dependent activity index (Al) during the second time period does not confirm a predefined physiological status, such as minimal physical activity, and confirms physical activity, the measurement of the physiological signal is determined invalid and has to be repeated during a time of minimal physical activity. Additionally, the processing unit is configured to determine a timedependent activity index (Al) based on the received plurality of acceleration data and to provide an initiation signal at its interface with the measuring unit at a time point automatically selected on the basis of the determined time-dependent Al , the initiation signal being to trigger a measurement of the predefined physiological signal. The processing unit is further configured to determine a second time period before and during the triggered measurement of the predefined physiological signal to determine a time-dependent activity index (Al) based on the received plurality of acceleration data of the first and the second time period or the second period alone. In case the plurality of activity data of the second time period confirms minimal physical activity the measurement of the predefined physiological signal is determined valid. In case the time-dependent activity index (Al)

[0013] 22.243P-WO | 04.12.2025 during the second time period does not confirm a predefined physiological status, such as minimal physical activity, and confirms physical activity, the measurement of the physiological signal is determined invalid and has to be repeated during a time of minimal physical activity.

[0014] In that the object is solved by an implant, and in particular one implant, having a measuring unit for measuring a predefined physiological signal, in particular a blood pressure signal, wherein the implant further comprises an accelerometer unit and a processing unit, wherein the accelerometer unit is configured to determine a plurality of acceleration data according to a predefined time scheme within predefined first time period and to transmit it to the processing unit, wherein the processing unit is configured to determine a time-dependent activity index (Al) based on the received plurality of acceleration data and to provide an initiation signal at its interface with the measuring unit at a time point automatically selected on the basis of the determined time-dependent Al , the initiation signal being to trigger a measurement of the predefined physiological signal, wherein the processing unit is configured to determine a second time period before and / or during the triggered measurement of the predefined physiological signal and the accelerometer unit is configured to determine a plurality of acceleration data according to a predefined time scheme within the predefined second time period and to transmit the data to the processing unit, wherein the processing unit is configured to determine a time-dependent activity index (Al) based on the received plurality of acceleration data of the first and / or the second time period, and to determine if the triggered measurement of the predefined physiological signal was performed in a predefined physical activity status, in particular in minimal activity.

[0015] The above implant is configured to be implanted partly or fully within an organ or cavity of the patient’s body, e.g. the vasculature. As one example for such an implant, the implant is an intravascular pressure sensor measuring the blood pressure intravascularly. Alternatively, the implant is a pacemaker, ILP, ICM, ICD or a device that delivers SCS, neurostimulation or DBS.

[0016] The implant comprises the measuring unit, the accelerometer unit and the processing unit which are electrically interconnected. This means, inter alia, that they are capable to

[0017] 22.243P-WO | 04.12.2025 exchange data. In one embodiment the implant further comprises a timer. In one embodiment the implant comprises a measuring unit, an accelerometer unit, a processing unit which are electrically interconnected, a power supply, e.g. a battery, and a timer within a housing as defined herein. A housing shall be understood as one housing such that all components mentioned above together with the housing form one implant. In one embodiment the implant only comprises for the functional units of the one implant a group consisting of a electrical circuitry, measuring unit, an accelerometer unit, a processing unit which are electrically interconnected, a power supply, e.g. a battery, a data memory, a communication unit and a timer within a housing as defined herein.

[0018] In one embodiment, the measuring unit comprises a blood pressure sensor that is configured to determine the blood pressure within the blood vessel in which the implant is located after implantation. The measuring unit is configured to measure the predefined physiological signal, for example blood pressure, heartbeat, predefined substance concentration within the blood or within different bodily fluid or a similar physiological signal. Further, the measuring unit may be configured to pre-process and / or digitize the measured physiological data prior transmitting them to the processing unit.

[0019] The accelerometer unit, which is provided in order to gather the acceleration data caused by the movement of the patient's body, i.e. of the implant that is fixed within the patient’s body. The accelerometer unit may comprise a 3-dimensional or a 2-dimensional accelerometer sensor, for example one 3 -dimensional accelerometer, one 2-dimensional accelerometer or several 1- or 2-dimensional accelerometers, such as a piezo electric and / or micro-electro mechanical (MEMs) accelerometer and / or mechanical accelerometer and / or gravimeter or any combination of these sensors. Accordingly, in one embodiment, the acceleration data comprise acceleration values of at least two spatial directions. The term 2-dimensional or 3- dimensional means that the acceleration unit is configured to determine 2-dimensional or 3- dimensional proper acceleration data along sensitive axes corresponding to the abovedefined two and, if applicable three, orthogonal axes of a Cartesian coordinate system. Accordingly, the acceleration data determined by the acceleration unit always comprise two data components, namely the acceleration along the first orthogonal axis of the coordinate system and the acceleration along the second orthogonal axis of the coordinate system, and,

[0020] 22.243P-WO | 04.12.2025 if applicable, the acceleration along the third orthogonal axis of the coordinate system. Proper acceleration is the acceleration (the rate of change of velocity) of the accelerometer unit in its own instantaneous rest frame. For example, an accelerometer at rest on the surface of the Earth will measure an acceleration into the direction of gravity due to Earth's gravity, straight upwards (by definition) of g ~ 9.81 m / s2because the Earth's surface exerts a normal force upwards relative to the local inertial frame (the frame of a freely falling object near the surface). In contrast, accelerometers in free fall (falling toward the center of the Earth at a rate of about 9.81 m / s2) will measure zero. Usually, the acceleration is quantified in the SI unit m / s2or in terms of standard gravity (multiples of g). In one embodiment, at least one spatial direction of the accelerometer unit may be parallel to one axis of the patient’s body.

[0021] The accelerometer unit produces acceleration data and transmits them to the processing unit. To provide a reliable information about the rest time and / or sleep time of the patient, the acceleration data are measured according to a predefined time scheme within a predefined, sufficiently long first time period. In one embodiment, the predefined first time period is several consecutive days, for example a period between 5 to 100 consecutive days. In one embodiment, the time scheme is an observation time period between 1 second and 1 minute every x hours, wherein x is between 0.5 and 5. Hence, the accelerometer is used in a mode that requires the accelerometer to measure activity of the patient at short time points while being dormant during the rest of the time of the first time period. Thereby, the accelerometer is used to provide activity data for the patient, but at very low energy costs.

[0022] From the determined plurality of acceleration data within the first time period the processing unit calculates a time-dependent activity index (Al). The activity index reflects the activity behavior of a patient in the first time period and can be used to predict, based on the data collected during the first time period, activity behavior in the future. A predefined second time period, after and / or during which in particular a measurement of the physiological signal shall be initiated, triggered and conducted, can be defined to support determining a predefined status of physical activity, e.g. minimal physical activity, during the triggered measurement of the physiological signal. Hence, the second time period is set after the first time period. More details of the Al calculation are provided below. There are different approaches for the calculation of the Al. The second time period shall be chosen based on

[0023] 22.243P-WO | 04.12.2025 calculation of the processing unit, to comprise a time scheme to collect activity data for updating the time-dependent activity index, in particular prior or during to a new measurement of the physiological signal. This time scheme may have the same intervals as defined above during the first time period. For example, the second time period covers a time period of, in particular collecting activity data from the accelerometer for calculating an updated time-dependent Al for example of at least two days, preferably four days, or alternatively in the range between four to one day, preferably 72 to 36 hours before a new measurement of the physiological signal is initiated and / or measured as the most recent changes in the patient’s behavior shall be covered for the determination of the most suitable time point of a new measurement of the physiological signal. Also, the second time period may also cover a time period during the new measurement of the physiological signal.

[0024] If the time period of the minimal physical activity (i.e. the patient sleeps or is at rest) is sufficiently well determined, for example by using data of the first period alone, a time point of minimum Al is automatically selected for provision of the initiation signal for the measurement of the predefined physiological signal on the basis of the determined timedependent Al.

[0025] For example, a timer is activated from the recent time or a time interval is stored in a realtime clock (RTC) to trigger the subsequent measurements. The measurements may result in a time point at or around the center time of minimal Al or at a predetermined time interval after the initiation signal to reliably measure within such time. From then on, the measurements are performed automatically and exclusively controlled by the timer or RTC. As indicated below, the timer or time interval may be updated to adapt to the changed conditions in connection with the patient’s behavior, for example based on a determined time-dependent activity index (Al) based on activity data collected during a second time period. A measurement of the predefined physiological signal during physical activity may then be discarded and repeated during a predefined physical status, e.g. at minimal physical activity.

[0026] Accordingly, in one embodiment, the second time period may additionally comprise a time period shortly before a new measurement of the physiological signal is initiated and / or

[0027] 22.243P-WO | 04.12.2025 measured, for example 0.5 hours to 5 minutes before such new measurement is initiated (i.e. the initiation signal is provided at the interface of the processing unit). This embodiment may detect short-term modifications in the patient’s behavior, e.g. if the patient is travelling, and may cause adaption of the time point or even prevent triggering of a measurement of the predefined physiological signal. If such short-term modification is detected over, for example, the predefined second time period, the adaption of the timer or time interval may be performed. In one embodiment, the second time period may additionally comprise a time period during a new measurement of the physiological signal. Additionally, the second time period may additionally comprise a time period shortly before and during a new measurement of the physiological signal is initiated and / or measured.

[0028] The implant may comprise a hermetically sealed housing and at least one fixation element extending from the housing for fixing / anchoring the implant within the vasculature at the pre-determined measuring location, for example within the pulmonary artery.

[0029] The housing of the implant may further comprise electrical circuitry, a power supply, e.g. a battery or a rechargeable battery, a data memory, and, in one embodiment, a communication unit. All aforementioned elements are electrically interconnected, also with the processing unit, and located within the housing. The processing unit may comprise a clock unit for provision of the initiation signal as indicated below.

[0030] In one embodiment, the implant has an elongated housing comprising a first end and a second end, wherein a first fixation element is located, fixed to and extends from the first end and / or a second fixation element is located, fixed to and extends from at the second end. Such configuration is advantageous because the elongated housing may easily be advanced through the vasculature of the patient using, for example, a catheter and may be arranged at the pre-determined measuring location (target location) of the implant. Additionally, the first fixation element and / or the second fixation element may be adapted such that it is flexible and / or takes an elongated configuration for implantation and movement through the vasculature of the patient and a deployed configuration for fixation at the pre-determined location for measuring physiological signals within the vasculature. For example, the first fixation element and / or the second fixation element may comprise or consist of at least one

[0031] 22.243P-WO | 04.12.2025 material of the group comprising Nitinol, Titanium alloy. The dimensions of the housing may be suitable for an implantation within a blood vessel, in particular for an implantation within the pulmonary artery.

[0032] In one embodiment, wherein the implant is a blood pressure sensor, the blood pressure sensor comprises a membrane (diaphragm) forming one section of an outer surface of the housing. For example, the housing and the membrane may consist of Titanium or Titanium alloy and form a hermetically sealed Titanium or Titanium alloy capsule. The membrane may be welded to the housing covering a respective through hole within the housing. The membrane may have a thickness of 10 pm to 50 pm. The membrane conducts the pressure signal provided by the surrounding blood, for example, to a pressure transducing medium, e.g. an oil filling, located within the housing. The membrane directly contacts the pressure transducing medium. In the embodiment, the housing may be filled with silicone oil acting as pressure transducer. By the pressure transducing medium the pressure signal is transduced to a pressure sensor chip (e.g. a piezo-sensor, a capacitive sensor) located within the housing of the implant, wherein the pressure transducing medium is in direct contact with the pressure sensor chip, as well. It may transmit a pressure range of 500 hPa to 1,300 hPa. In one embodiment, the housing comprises two expansion grooves for compensation of pressures changes caused by thermal effects. Accordingly, the blood pressure sensor may be formed by the membrane, the pressure transducing medium, the pressure sensor chip and the processor as well as the circuitry form the blood pressure sensor.

[0033] In one embodiment, the first fixation element and / or the second fixation element comprises or consists of a biocompatible material providing a shape memory effect, for example Nitinol. Further, the first fixation element and / or the second fixation element and / or the housing may partially comprise a biocompatible coating, for example, Parylene.

[0034] In one embodiment, the data memory may store the determined physiological data, e.g. the blood pressure data as well as data for the timer for triggering the measurement of the physiological , and may include any volatile, non-volatile, magnetic, or electrical media, such as a random-access memory (RAM), read-only memory (ROM), non-volatile RAM

[0035] 22.243P-WO | 04.12.2025 (NVRAM), electrically-erasable programmable ROM (EEPROM), flash memory, or any other memory device.

[0036] In one embodiment, the intravascular implant comprises a communication unit. The communication unit may be adapted for data communication with an external relay device and / or an external computing unit (server). For example, communication may be provided wirelessly (“over the air”) using electromagnetic waves, for example Bluetooth, WLAN, ZigBee, NFC, Wibree or WiMAX, MICS (Medical Implant Communication Service) in the radio frequency region, or IrDA or free-space optical communication (FSO) in the infrared or optical frequency region. The communication may be one-directional (from the implant to the external relay device or computing unit) or bi-directional. Accordingly, the communication unit may comprise a respective transmitter or a transceiver, e.g. an antenna, to send the determined blood pressure data to the relay device and / or computing unit. The first fixation element and / or the second fixation element may be configured to function as an antenna and / or the housing may be configured to function as an antenna. Accordingly, the respective fixation element and / or the housing may be coupled to the communication unit.

[0037] In one embodiment, the implant may be connected with a home monitoring service via the communication unit and an optional external relay device, wherein the home monitoring service provides manual or automatic monitoring of blood pressure data provided by the implant. If the patient faces any critical situation, the home monitoring service may contact an HCP based on the received physiological data, e.g. blood pressure data.

[0038] In one embodiment, the activity index Al is determined as wherein ax, ayand azare the acceleration component values of the respective measured acceleration data value into the directions x, y, z with regard to a Cartesian coordinate system, g is the gravitation vector and T is the duration of the used observation time period of the predefined time scheme. In this example, the sum of the squares of the components ax, ayand azof the acceleration values minus the square of the gravitation vector g is

[0039] 22.243P-WO | 04.12.2025 determined and its absolute value integrated over the observation period T of the predefined time scheme. Accordingly, if, e.g., the time scheme has every 2 hours an observation period of 10 s, the integration is calculated over T = 10 s. Different calculation rules for Al can be used, as well.

[0040] In one embodiment, the processing unit comprises a clock generator, wherein the processing unit is configured to determine the number of clock pulses and to count this number to determine the time point at which the initiation signal at its interface is provided. By such procedure a time interval from one to the next generation of an initiation signal may be realized. The clock generator is advantageously used to determine the time point at which the initiation signal is provided at the interface of the processing unit.

[0041] The above object is further solved by a method of operating an implant having a measuring unit for measuring a predefined physiological signal, in particular a blood pressure signal, wherein the implant further comprises an accelerometer unit and a processing unit, comprising the following steps:

[0042] - determining of a plurality of acceleration data according to a predefined time scheme within predefined first time period and transmitting it to the processing unit,

[0043] - determining of a time-dependent activity index (Al) based on the received plurality of acceleration data and

[0044] - providing an initiation signal at an interface of the processing unit with the measuring unit at a time point automatically selected on the basis of the determined time-dependent Al, the initiation signal being to trigger a measurement of the predefined physiological signal.

[0045] The method may further comprise the steps of:

[0046] - predicting a time-dependent activity index (Al) based on the received plurality of acceleration data

[0047] - determining of a plurality of acceleration data according to a predefined time scheme within a predefined second time period and transmitting it to the processing unit,

[0048] - determining of a time-dependent activity index (Al) based on the received plurality of acceleration data of the first and the second time period or the second time period alone.

[0049] 22.243P-WO | 04.12.2025 The method may further comprise the step of determining whether the measurement of the predefined physiological signal was conducted during a predefined physical status, and further the step of determining whether the measurement has to be repeated or not.

[0050] In particular, the method may further comprise the step of determining whether the measurement of the predefined physiological signal, in particular the blood pressure was conducted during a predefined physical status, in particular at minimal physical activity.

[0051] The above method has the same advantages as the above described implant. It is referred to the above explanations, as well. The same applies to the further embodiments of the method listed below. As soon as the initiation signal is received by the measuring unit, the measuring unit is configured to measure the predefined physiological signal at least once or several times within a predefined time period.

[0052] The above method may be realized as a computer implemented method as it is executed by the accelerometer unit (and its processor) and the processing unit, and, if applicable, by the measuring unit (and its processor).

[0053] In one embodiment of the method, the predefined first or second time period comprises several consecutive days and / or wherein the time scheme is an observation time period between 1 second and 1 minute every x hours, wherein x is between 0.5 and 5, and / or wherein the second time period is at least two days before a new measurement of the physiological signal is initiated or during the measurement of the physiological signal.

[0054] In one embodiment of the method, the second time period further comprises a time period shortly before and / or during a new measurement of the physiological signal is initiated and / or measured.

[0055] In one embodiment of the method, the acceleration data comprise acceleration values of at least two spatial directions.

[0056] In one embodiment of the method (equation (1)), the Al is determined as

[0057] 22.243P-WO | 04.12.2025 wherein ax, ayand a- are the components of the acceleration values into the orthogonal directions x, y, z with regard to Cartesian coordinate system, g is the gravitation vector and T is the duration of the used observation time period of the predefined time scheme, for example, as indicated above, between 1 second and 1 minute.

[0058] Alternatively, the following calculation schemes for Al may be used (equations (2) to (5)) or ) or wherein amx= ax(i.e. the average value of the respective acceleration component), wherein with regard to all above equations (2) to (5) ax, ayand a- are the components of the acceleration values into the orthogonal directions x, y, z with regard to Cartesian coordinate system, a(i) the ith acceleration measurement value (z = 1...ri) within T and T the duration of the used observation time period of the predefined time scheme.

[0059] 22.243P-WO | 04.12.2025 In one embodiment of the method, the processing unit determines the number of clock pulses of a clock generator of the processing unit and counts this number to determine the time point at which the initiation signal at its interface is provided.

[0060] Furthermore, a computer program product is disclosed comprising instructions which, when executed by a processor, causes the processor to perform the steps of the above defined method. Accordingly, a computer readable data carrier storing such computer program product is disclosed.

[0061] The present invention will now be described in further detail with reference to the accompanying schematic drawing, wherein

[0062] Fig. 1 shows an embodiment of the inventive implant in a side view,

[0063] Fig. 2 depicts some elements accommodated within the housing of the implant of Fig. 1,

[0064] Fig. 3 the activity index dependent on time over a period of 24 days,

[0065] Fig. 4 the activity index dependent on time over a period of 74 days (upper curve), the activity index dependent on time minus the daily mean value and in the lower curve a signum function applied to the values of the middle curve.

[0066] The embodiment of an implant 1, namely an intravascular pressure sensor depicted in Fig. 1 and 2 comprises a hermetically sealed housing 10. One section of the housing 10 may be formed by a membrane for transmitting the blood pressure into the housing 10 when implanted. The housing 10 and the membrane consist of an, e.g., Titanium alloy. Within the housing 10 the implant 1 comprises electrical circuitry, a battery, a processing unit 12, a data memory and a communication unit. The electrical circuitry, the battery, the processing unit 12, the data memory, and the communication unit are electrically connected to each other. Further, the implant 1 comprises a first fixation loop 14 and a second fixation loop 16, wherein the first fixation loop 14 is mechanically connected to a first end of the elongated housing 10 and the second fixation loop 16 to a second end of the elongated housing 10,

[0067] 22.243P-WO | 04.12.2025 located opposite the first end. The first fixation loop 14 and the second fixation loop 16 provide a mechanical fixation of the implant at a predefined target location within the patient’s vasculature. The first fixation loop 14 and the second fixation loop 16 consist of, e.g., Nitinol.

[0068] In this embodiment, the housing 10 is further filled with silicone oil that directly contacts the membrane thereby transducing the pressure signal to a MEMS sensor located within the housing 10. The silicone oil is in direct contact with the MEMS sensor. The MEMS sensor is electrically connected to the processing unit 12 to which the measured blood pressure data are transmitted. Accordingly, the measuring unit, generally shown with reference number 18 in Fig. 2 comprises the membrane, the silicone oil and the MEMS sensor. After implantation of the implant 1 to the predetermined measuring location within the patient’s vasculature the blood pressure data may be determined at time points initiated by the processing unit 12.

[0069] To determine a measuring time for the blood pressure where the patient sleeps or is at rest, the implant 1 uses a 3 -dimensional accelerometer 20 that is electrically connected to the processing unit 12 and accommodated with in the housing 10. At first, a plurality of acceleration data of the patient is recorded and digitized by the accelerometer 20, for example, for 10 seconds every two hours over a first time period of 1 week. These acceleration data are transmitted to the processing unit 12. The processing unit 12 calculates a time-dependent activity index (Al) using one of the equations (1) to (5) as indicated above. An example of such data is shown in Fig. 3 where the calculated Al (using equation (1) for T = 10 5)) is depicted dependent on time for a period of 24 days. Accordingly, the upper curve of Fig. 4 shows the determined Al dependent on time over a plurality of days, as well. The middle curve of Fig. 4 shows the Al values with a mean value of the Al based on a period of 24h subtracted from each value such that it fluctuates around zero. Then, for example, a signum function may be used to determine the time ranges in which the Al is below the zero threshold. From this, the time ranges with no or little activity of the patient can be derived, which is then used as an input parameter for a timer 22 having a clock generator.

[0070] 22.243P-WO | 04.12.2025 After determining the time ranges with smallest Al values, the processing unit 12 starts timing using the clock generator of timer 22. The processing unit 12 provides an initiation signal at an interface 24 of the processing unit 12. The timer 22 may be controlled such that, for example, the initiation signal is provided approximately in the centre of the minimal value regions of the lower curve signal of Fig. 4. Each generated initiation signal is transmitted from the interface 24 to the measuring unit 18 (see arrow 26) thereby triggering determination of the actual blood pressure within the vasculature of the patient. The initiation signal triggers the determination either directly at the time the initiation signal is transmitted or at a predetermined time after the transmission of the initiation signal, in particular at a time between 1 and 3 hours, in particular 2 hours after the transmission of the initiation signal. The respective blood pressure value is then transmitted to the processing unit 12 via the connection depicted by arrow 28 in Fig. 2.

[0071] When the behavior of the patient is changed, e.g. if the patient travels, the sleep or rest time periods may shift. Accordingly, the accelerometer 20 continues to determine the acceleration data and the processing unit 12 continues to determine the Al. The processing unit 12 uses the Al values of, for example, the last 2 days to control the provision of the initiation signal for the blood pressure measurement, i.e. to adapt the timer 22 accordingly. Additionally, the accelerometer may determine 10 minutes before the measurement is initiated whether the patient is actually at rest. The measurement is initiated only by the processing unit 12 if the most recent acceleration date is below a predefined threshold value.

[0072] In one embodiment, the communication unit may transmit the measured blood pressure data (including the associated measurement time point) to an external relay device using, for example, wireless data transmission in the MICS band. The external relay device forwards the data to a home monitoring service. There, the measured data may be assessed by an HCP. With regard to data communication, the first fixation loop 14 may be used as an antenna.

[0073] Accordingly, the inventive implant 1 makes it possible to measure blood pressure data or similar physiological data at appropriate time points with regard to the activity of the patient that increase reliability of the data. The invention reduces the amount of care required for patients who carry an implant that measures a predefined physiological value. No manual

[0074] 22.243P-WO | 04.12.2025 readjustment of the measurement time is required in the event of time changes or travel. In addition, the measurement time is automatically adjusted to the patient's individual circadian rhythm. Furthermore, the implant does not need to have a bidirectional communication interface for the purpose of setting the measurement time.

[0075] 22.243P-WO | 04.12.2025

Claims

Claims1. An implant (1) having a measuring unit (18) for measuring a predefined physiological signal, in particular a blood pressure signal, wherein the implant (1) further comprises an accelerometer unit (20) and a processing unit (12), wherein the accelerometer unit (20) is configured to determine a plurality of acceleration data according to a predefined time scheme within predefined first time period and to transmit it to the processing unit (12), wherein the processing unit (12) is configured to determine a time-dependent activity index (Al) based on the received plurality of acceleration data and to provide an initiation signal at its interface (24) with the measuring unit (18) at a time point automatically selected on the basis of the determined time-dependent Al, the initiation signal being to trigger a measurement of the predefined physiological signal, wherein the processing unit is configured to determine a predefined second time period before and / or during the triggered measurement of the predefined physiological signal and the accelerometer unit is configured to determine a plurality of acceleration data according to a predefined time scheme within the predefined second time period and to transmit the data to the processing unit, wherein the processing unit is configured to determine a time-dependent activity index (Al) based on the received plurality of acceleration data of the first and / or the second time period.

2. The implant (1) according to claim 1, wherein the predefined first time period is several consecutive days, for example 5 days to 100 days.

3. The implant (1) according to claim 2, wherein the second time period comprises a time period shortly before and / during the measurement of the physiological signal is initiated and / or measured.

4. The implant (1) according to any one of the previous claims, wherein the acceleration data comprise acceleration values of at least two spatial directions.22.243P-WO | 04.12.20255. The implant (1) according to any one of the previous claims, wherein the time scheme is an observation time period between 1 second and 1 minute every x hours, wherein x is between 0.5 and 5.

6. The implant (1) according to any one of the previous claims, wherein the second time period is at least two days before the measurement of the physiological signal is initiated and / or measured.

7. The implant (1) according to any one of the previous claims, wherein the Al is determined aswherein ax, ayand azare the acceleration values in the orthogonal directions x, y, z with regard to a Cartesian coordinate system, g is the gravitation vector and T is the duration of the used observation time period of the predefined time scheme.

8. The implant (1) according to any one of the previous claims, wherein the processing unit (12) comprises a clock generator, wherein the processing unit is configured to determine the number of clock pulses and to count this number to determine the time point at which the initiation signal at its interface is provided.

9. A method of operating an implant (1) having a measuring unit (18) for measuring a predefined physiological signal, in particular a blood pressure signal, wherein the implant (1) further comprises an accelerometer unit (20) and a processing unit (12), comprising the following steps:- determining of a plurality of acceleration data according to a predefined time scheme within predefined first time period and transmitting it to the processing unit (12),- determining of a time-dependent activity index (Al) based on the received plurality of acceleration data and- providing an initiation signal at an interface (24) of the processing unit (12) with the measuring unit (18) at a time point automatically selected on the basis of the22.243P-WO | 04.12.2025determined time-dependent Al, the initiation signal being to trigger a measurement of the predefined physiological signal.

10. The method of claim 9, wherein the predefined first or second time period comprises several consecutive days and / or wherein the time scheme is an observation time period between 1 second and 1 minute every x hours, wherein x is between 0.5 and 5, and / or wherein the second time period is at least two days before a new measurement of the physiological signal is initiated or during the measurement of the physiological signal.

11. The method according to claim 10, wherein the second time period further comprises a time period shortly before and / or during a new measurement of the physiological signal is initiated and / or measured.

12. The method according to any one of the previous claims, wherein Al is determined aswherein ax, ayand azare the acceleration values in the orthogonal directions x, y, z with regard to a Cartesian coordinate system, g is the gravitation vector and T is the duration of the used observation time period of the predefined time scheme.

13. The method according to any one of the previous claims, wherein the processing unit (12) determines the number of clock pulses of a clock generator of the processing unit (12) and counts this number to determine the time point at which the initiation signal at its interface is provided.

14. A computer program product comprising instructions which, when executed by a processor, causes the processor to perform the steps of the method according to any one of the claims 9 to 13.

15. Computer readable data carrier storing a computer program product according to claim 14.22.243P-WO | 04.12.2025

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