Implantable medical device operative in the presence of an MRI device

Abstract

An implantable medical device comprises a sensing device for sensing a measurement quantity indicative of a presence of an MRI device, a processing device for controlling operation of the implantable medical device and for identifying a presence of an MRI device based on measurement values obtained from the sensing device; and a program memory. An analysis module is configured to store information concerning a multiplicity of events relating to operation of the implantable medical device. The program memory is configured to store at least two program routines for operating the implantable medical device in case of a presence of an MRI device. The processing device is configured, for controlling operation of the implantable medical device in the presence of an MRI device, to select one of said at least two program routines based on a statistical analysis of information concerning a predefined number of events of said multiplicity of events.

Claims

1. An implantable medical device, comprising: a sensing device for sensing a measurement quantity indicative of a presence of an MRI device a processing device for controlling operation of the implantable medical device and for identifying a presence of an MRI device based on measurement values obtained from the sensing device; program memory; and an analysis module configured to store information concerning a multiplicity of events relating to operation of the implantable medical device, wherein the program memory is configured to store at least two program routines for operating the implantable medical device case of a presence of an MRI device, wherein the processing device is configured, for controlling operation of the implantable medical device in the presence of an MRI device, to select one of said at least two program routines based on a statistical analysis of information concerning a predefined number of events of said multiplicity of events.

2. The implantable medical device of claim 1, wherein the analysis module comprises a circular buffer for storing information concerning said predefined number of events.

3. The implantable medical device of claim 1, wherein at least some events of said multiplicity of events relate to events of cardiac activity.

4. The implantable medical device of claim 3, wherein events of cardiac activity are events of stimulated contractions or intrinsic contractions.

5. The implantable medical device of claim 1, wherein at least some events of said multiplicity of events relate to stimulation events.

6. The implantable medical device of claim 5, wherein stimulation events are events of a cardiac stimulation or a neuro-stimulation.

7. The implantable medical device of claim 1, wherein at least some events of said multiplicity of events relate to a triggering of a therapeutic function.

8. The implantable medical device of claim 1, wherein one of said at least two program routines represents an OFF mode in which a stimulation function is switched off.

9. The implantable medical device of claim 1, wherein one of said at least two program routines represents an asynchronous mode employing an asynchronous stimulation.

10. The implantable medical device of claim 1, wherein the processing device is configured to control the implantable medical device for cyclically conducting test operations for obtaining information concerning events relating to the operation of the implantable medical device.

11. The implantable medical device of claim 1, wherein the processing device is configured to adapt at least one parameter of any one of said at least two program routines based on a statistical analysis of information concerning said multiplicity of events.

12. The implantable medical device of claim 1, wherein said a predefined number of events is programmable by a user.

13. A method for operating an implantable medical device comprising: sensing a measurement quantity indicative of a presence of an MRI device using a sensing device; identifying a presence of an MRI device based on measurement values obtained from the sensing device using a processing device for controlling operation of the implantable medical device; storing, using an analysis module, information concerning a multiplicity of events relating to operation of the implantable medical device; and selecting, based on a statistical analysis of information concerning a predefined number of events of said multiplicity of events, by the processing device in case of a presence of an MRI device one of at least two program routines for operating the implantable medical device in the presence of an MRI device, the at least two program routines being stored in a program memory.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Various features and advantages of the present invention may be more readily understood with reference to the following detailed description and the embodiments shown in the drawings. Herein,

[0049] FIG. 1 shows a schematic illustration of an implantable medical device in a patient;

[0050] FIG. 2 shows a schematic drawing of an MRI device;

[0051] FIG. 3 shows a schematic drawing of an implantable medical device;

[0052] FIG. 4 shows a schematic drawing of preparatory steps for conducting an MRI examination on a patient carrying an implantable medical device such as a pacemaker device; and

[0053] FIG. 5 shows a schematic drawing of an implantable medical device being configured for adapting operation in case of a presence of an MRI device.

DETAILED DESCRIPTION

[0054] Subsequently, embodiments of the present invention shall be described in detail with reference to the drawings. In the drawings, like reference numerals shall designate functionally similar structural elements, if appropriate.

[0055] It is to be noted that the embodiments are not limiting for the present invention, but merely represent illustrative examples.

[0056] FIG. 1 shows a schematic illustration of an implantable medical device 1, for example, in the shape of a stimulation device, such as a pacing device or a defibrillation device. The implantable medical device 1 may, for example, comprise a generator 10 which, for example, as illustrated in FIG. 1, may be subcutaneously implanted into a patient, wherein an electrode 11 is connected to the generator 10 and extends from the generator 10 towards a region of interest, for example, the patient's heart, such that a therapy function may be provided at the region of interest, for example, in the patient's heart.

[0057] An implantable medical device 1 of this kind may, for example, be configured to provide a therapy function over a prolonged period of time, for example, a pacing function or a defibrillator function. The implantable medical device 1, for this, may be permanently implanted into a patient P and may function in a substantially autarkic manner, wherein a communication connection may be established with the implantable medical device 1 using an external device 2, for example, to program the implantable medical device 1 or to transfer, using, for example, telemetry, data from the implantable medical device 1 to the external device 2.

[0058] An external device 2 may communicate with the implantable medical device 1 using electromagnetic means, for example, by establishing an inductive coupling in between the implantable medical device 1 and the external device 2.

[0059] The external device 2 may alternatively be a permanent magnet which may be brought into the vicinity of the implantable medical device 1 in order to trigger an action of the implantable medical device 1, for example, for waking up the medical device 1.

[0060] If, as schematically illustrated in FIG. 2, a patient P shall undergo an MRI examination using an MRI device 3, the patient P, carrying an implantable medical device 1, is introduced into a bore 30 of the MRI device 3 by placing the patient P on a patient bed 31 and by continuously moving, using an electro-motoric drive of the patient bed 31, the patient P into the bore 30 in a movement direction V. When moving the patient P into the bore 30 of the MRI device 3, the patient P herein is brought into the range of a constant magnetic field M of the MRI device 3, the magnetic field M generally having a maximum magnetic field strength (corresponding to the magnetic flux density B and indicated usually in Tesla [T]) within the bore 30. Hence, when the patient P is moved into the bore 30 of the MRI device 3, the magnetic field strength of the magnetic field M at the location of the implantable medical device 1 will steadily increase.

[0061] Caused by a magnetic field M of an MRI device 3 electrical signals may be induced within an implantable medical device 1. Hence, it shall be detected if an implantable medical device 1 comes into the range of an MRI device 3, such that operation of the implantable medical device 1 can suitably be modified in order to avoid a disturbance of operation by the MRI device 3.

[0062] FIG. 3 illustrates an embodiment of a generator 10 of an implantable medical device 1, for example, in the shape of a stimulation device such as a pacemaker device or a defibrillator device. Included in a housing of the generator device 10 is a processing device 101, implemented, e.g., by electronic circuitry on a circuit board, which serves to control operation of the generator 10 for transmission of electrical stimulation energy via the electrodes 11 connected to a connector block 100 of the generator 10, and for analyzing sense signals received, e.g., via the electrodes 11 to provide for a therapy aligned to an activity of, for example, the patient's heart.

[0063] The generator 10 further comprises an energy storage 102 in the shape of a battery, a sensing device 103, for example, in the shape of a GMR sensor for sensing magnetic fields, and a communication device 104 for establishing a communication connection, for example, to an external device 2, as illustrated in FIG. 1.

[0064] The sensing device 103 is connected to the processing device 101 and is configured to conduct measurements yielding measurement values indicative of a magnetic field strength at the location of the sensing device 103. The sensing device 103 may, for example, be configured to conduct measurements at a specified sampling rate, for example, at a rate in between 1 Hz and 50 Hz, for example 4 Hz. The sensing device 103 provides (discrete) measurement values to the processing device 101, which are analyzed by the processing device 101 and are used to identify the presence of an MRI device 3.

[0065] Referring now to FIG. 4, if a patient P carrying an implantable medical device 1 (for example, in the shape of a pacemaker device, such as a CRT device) has to undergo an MRI examination, the patient P typically has to visit a physician C such that the physician C may adapt operation of the implantable medical device 1 in order to avoid a malfunction of the implantable medical device 1 during MRI examination (steps A1, A2 in FIG. 4). In the course of adaption, for example, an MRI compatible operating mode is enabled in which a stimulation function of the implantable medical device 1 is switched off, or in which the stimulation function is adapted such that the implantable medical device 1 may safely operate in the presence of electromagnetic fields as caused by an MRI device 3.

[0066] Such adaption of the configuration of the implantable medical device 1 should take place within a rather short time range prior to the MRI examination, for example, within 14 days prior to the MRI examination. The patient P may then undergo the MRI examination (steps A3, A4 in FIG. 4), wherein the MRI compatible operating mode is activated once the presence of the MRI device 3 is detected by the implantable medical device 1 such that during the MRI examination the implantable medical device operates according to its modified, MRI compatible operating mode. Subsequent to the MRI examination data may be reported to a home monitoring system 4 (steps A5, A6 in FIG. 4), and the implantable medical device 1 may switch back to resume normal operation.

[0067] In a conventional scenario, a patient P hence must visit a physician C prior to an MRI examination, which must suitably configure the implantable medical device 1 in order to enable an operation adapted for a potential interaction with electromagnetic fields of an MRI device 3. This increases the burden for the patient P, and also causes additional costs.

[0068] Referring now to FIG. 5, an implantable medical device 1 is adapted for an automatic change in configuration if a presence of an MRI device 3 is detected based on measurement data obtained from a sensing device 103.

[0069] The implantable medical device as shown in FIG. 5 comprises a processing device 101 which controls operation of the implantable medical device 1, in particular to control a stimulation module 105 configured to transmit stimulation energy towards electrodes 11 attached to a generator portion 10 of the implantable medical device 1 and to receive sensing data from the electrodes 11. For example, in one embodiment the implantable medical device 1 may be configured to provide for an anti-bradycardia stimulation, for which a therapeutic function is triggered once a bradycardia is detected in order to provide for a pacing counteracting the bradycardia.

[0070] Generally, in a default operating mode the processing device 101 may, for example, provide for a stimulation based on sensed measurement data, in order to, for example, provide a stimulation in a synchronous fashion in synchronicity and triggered by sensed activity. For example, in a default operating mode the processing device may be configured to operate in a so-called VVI mode, relating, for example, to a ventricular anti-bradycardia pacing, or a DDD mode, relating, for example, to a dual-chamber anti-bradycardia pacing.

[0071] In case the processing device 101 identifies, based on measurement data obtained from a sensing device 103 (such as a GMR sensor for measuring a magnetic field strength at the location of the implantable medical device 1), the presence of an MRI device 3, the processing device 101 is configured to automatically adapt operation of the implantable medical device 1. For this, the processing device 101 switches to one of a multiplicity of program routines R1, R2, which are stored in a program memory 106 and provide for modular functions which provide for a suitable operation of the implantable medical device 1 in the presence of electromagnetic fields of an MRI device 3. In particular, by means of the program routines R1, R2 it is made sure that malfunctions due to interaction with electromagnetic fields of the MRI device 3 are avoided.

[0072] In the program memory 106, different program routines R1, R2 are stored, which provide for different modes of operations. Herein, the processing device 101 is configured to select one of the program routines R1, R2 based on a statistical analysis of information relating to a predefined number of events as stored in an analysis module 107.

[0073] The analysis module 101 may, for example, comprise a circular buffer having a fixed size, such that in the analysis module 17 information relating to a predefined number of events may be stored.

[0074] The events may, for example, relate to events of cardiac activity, events of stimulation, events of a triggering of a therapeutic function, or other events, such as programming events.

[0075] Information relating to events of cardiac activity may, for example, be measurement data indicating an intrinsic or stimulated cardiac activity, such as an atrial or ventricular activity. Such measurement data may, for example, be obtained in test operations, which are performed cyclically, for example, in regular intervals once a day, twice a day, 3 times a day, 4 times a day, each hour, or each half hour. During a measurement period herein, for example, the heart rate and/or other characteristics of cardiac activity may be obtained, such as an amplitude, a pulse width, a pulse energy or the like, wherein the respective characteristic value may be averaged over the measurement period, such that, for example, an averaged heart rate at different time instances per day is obtained.

[0076] Information relating to events of stimulation may, for example, indicate a triggering of a specific stimulation, such as a defibrillation shock, or a neuro-stimulation.

[0077] Information relating to events of a triggering of a therapeutic function may, for example, indicate whether a specific function, such as an anti-bradycardia stimulation, a biventricular stimulation for resynchronization, an SCS stimulation or another neuro-stimulation has been triggered.

[0078] Based on the statistical analysis it in particular may be determined whether and what type of simulation may be required for a particular patient P during an MRI examination.

[0079] One of the program routines R1, R2 may, for example, represent an OFF mode in which a stimulation function is switched off, such that, if the implantable medical device 1 is operated according to the particular program routines R1, R2, no stimulation takes place once the patient P is in the vicinity of an MRI device 3.

[0080] Another of the program routines R1, R2 in turn may represent an asynchronous mode in which a stimulation takes place, but in an asynchronous fashion, i.e., without sensing data and without basing a stimulation, such as a pacing action, on sensed data. The asynchronous mode may, for example, be a VOO or a DOO mode.

[0081] The processing device 101 may, for example, be configured to choose between the to program routines R1, R2 based on an analysis whether a particular patient P requires a stimulation or not during the time period of an MRI examination. If it, for example, is found based on the statistical analysis that a patient P requires a pacing action even during the MRI examination, the processing device 101 may switch to a program routine R1, R2 which represents an asynchronous mode.

[0082] If in contrast it is found based on the statistical analysis that no stimulation is necessarily required during the time of the MRI examination, the processing device 101 may switch to a program routine R1, R2 which represents the OFF mode, such that stimulation is switched off during the MRI examination. If it is, for example, found, based on the statistical analysis, that the heart rate has been stable for the patient over recent measurements, requiring, e.g., no anti-bradycardia stimulation, it may be switched to the OFF mode.

[0083] In addition to selecting a particular program routine R1, R2, the processing device 101 may be configured to adapt and program a particular parameter of a particular program routine R1, R2, such as a stimulation energy/amplitude, a stimulation frequency, a stimulation location (for example, in the right ventricle, in the left ventricle, or in both the right ventricle and the left ventricle), a particular mode of operation (DOO vs. VOO mode) or the like.

[0084] The selection of the program routine R1, R2 takes place once the processing device 101, based on readings of the sensing device 103, identifies the presence of an MRI device 3.

[0085] The sensing device 103 herein may, for example, be configured to measure a magnetic field strength for identifying, for example, a rise of the magnetic field strength. Alternatively, the sensing device 103 may be adapted to measure a gradient field vector, an RF field, a position, a vibration, or a characteristic electrical signal pattern as, for example, induced on the electrodes 11. Multiple sensors measuring different measurement quantities may be used in combination.

[0086] Once the processing device 101 identifies that the patient P no longer is in the presence of an MRI device 3, the processing device 101 switches back to the default operating mode, by, for example, switching on a stimulation function or switching to a synchronous mode.

[0087] By means of the processing device 101, hence, an automatic switching of operation to a program routine R1, R2 which is suitable for use during an MRI examination is provided. This makes it possible for a patient P to undergo an MRI examination without specific preparation, in particular without having to visit a physician C (as shown in FIG. 4) for the purpose of configuring the implantable medical device 1 prior to undergoing the MRI examination. The burden for the patient P hence is reduced, while at the same time saving time and costs.

[0088] It will be apparent to those skilled in the art that numerous modifications and variations of the described examples and embodiments are possible in light of the above teachings of the disclosure. The disclosed examples and embodiments are presented for purposes of illustration only. Other alternate embodiments may include some or all of the features disclosed herein. Therefore, it is the intent to cover all such modifications and alternate embodiments as may come within the true scope of this invention, which is to be given the full breadth thereof. Additionally, the disclosure of a range of values is a disclosure of every numerical value within that range, including the end points.

LIST OF REFERENCE NUMERALS

[0089] 1 Implantable medical device (pacemaker device) [0090] 10 Generator [0091] 100 Connector block [0092] 101 Processing device [0093] 102 Energy storage [0094] 103 Sensing device [0095] 104 Communication module [0096] 105 Stimulation module [0097] 106 Program memory [0098] 107 Analysis module [0099] 11 Electrode [0100] 2 External device [0101] 3 MRI device [0102] 30 Bore [0103] 31 Patient bed [0104] 4 Home monitoring system [0105] A1-A6 Steps [0106] C Clinician [0107] M Magnetic field (magnetic flux density) [0108] P Patient [0109] R1, R2 Program routine [0110] V Moving direction