WO2002007815A1

WO2002007815A1 - A system for monitoring an implantable medical device using graphical representation

Info

Publication number: WO2002007815A1
Application number: PCT/SE2001/001577
Authority: WO
Inventors: Eric Samuelsson
Original assignee: St. Jude Medical Ab
Priority date: 2000-07-21
Filing date: 2001-07-05
Publication date: 2002-01-31
Also published as: SE0002751D0

Abstract

A programmer for an implantable medical device is described. It includes means for displaying a graphical representation of a quantity influenced by the operation of the medical device and means for associating parameters relating to the control of the device with portions of said graphical representations. An operator can add graphical elements representing variations in the quality caused by functions of the medical device to the representation to generate a modified graphical representation. The arrangement responds to this modification by associating new or modified parameters with the modified representation. This enables an operator to generate custom graphical representations that illustrate the effect achieved by a medical device, rather than setting parameter values and then observing the effect. The resulting system is thus not only more intuitive and thus easier to use for a medical practitioner, it will also be safer for the patient, since there is less likelihood of the operator programming unsuitable parameter values.

Description

A SYSTEM FOR MONITORING AN IMPLANTABLE MEDICAL DEVICE USING GRAPHICAL REPRESENTATION

Field of Invention

The invention relates to implantable medical devices and specifically to programming systems for implantable medical devices.

Background Art

Implantable medical devices perform numerous and often highly complex functions many of which need to be adapted to the particular diagnosis of a patient. For example, implantable cardiac pacers, which provide stimulating impulses to a heart with a disturbed cardiac rhythm, are capable of applying a range of different parameters values and also functions to meet the needs of different patients.

In addition to the programmable parameters, conventional cardiac pacers typically also store large quantities of measured data. To this end they are equipped with sensors for monitoring the activity of the heart, and possibly other physiological activity. Information obtained through monitoring can be used for diagnosing certain patient conditions, which in turn can be treated by adapting the pacer functions in some way. The programming and interrogation of implanted devices is commonly performed non-invasively using a computer- or microprocessor-based programmer, which communicates with the pacer via a telemetry link. These programmers include a display and some form of input device or keyboard. When the programmer interrogates the implanted device, stored and measured data will be transferred to the programmer.

This information must be displayed to the operator. Parameter values, whether programmable, measured or fixed, are conventionally displayed numerically or alphanumerically. An example of such a programmer is described in US 5,833,623. When large amounts of data are available for consultation only some of the data will be displayed on the screen at any one time. The grouping of data for simultaneous display is typically dictated by the manner in which data is organised within the programmer, which in turn is dependent on technical restraints. The data organisation is thus often not optimal for ease of consultation by a medically skilled practitioner.

A problem with the operation of such prior art programmers is therefore that an operator attempting to program an implantable medical device must be very familiar with the programmers functions if he is to fully exploit all the functions and possibilities of a device. The majority of such medical devices are, however, programmed and monitored by medically skilled practitioners, who have a thorough understanding of the patient's condition, but may have less knowledge of the possibilities of the medical device. Moreover, a single practitioner may be required to monitor several different types of medical devices, working in different modes and implanted in patients with different diagnoses. As a result of this, an operator will rarely encounter two medical devices of the same type and configured to address the same patient diagnosis. Owing to most operators' inevitable unfamiliarity with the advanced workings of the majority of implanted devices, many functions that could be obtained through these devices when programmed properly are left unused. Consequently implantable medical devices often retain the default parameter values set on manufacture throughout their lifetime.

It is thus an object of the invention to provide a programmer for monitoring and controlling the operation of an implantable device that is easy to operate, and thus enables an operator to exploit all possible functions of a medical device with little knowledge of the programmer. It is a further object of the invention to provide a programmer that provides the operator with an interface to the medical device that is easy to understand and operate, and thus enables an operator to exploit the functions of a medical device with little knowledge of the programmer.

SUMMARY OF INVENTION

This object is achieved in an arrangement for monitoring and controlling the operation of an implantable medical device, having means for communicating with the medical device, means for displaying a graphical representation of at least one quantity that can be influenced by the operation of the medical device and associating parameters relating to the control of the device with portions of said graphical representation, means for enabling the addition of at least one graphical element to the graphical representation to form a modified graphical representation, wherein the graphical element represents a variation in the quantity that can be produced by functions of the implantable medical device, means responsive to the modified graphical representation for generating new and/or modified parameters associated with the graphical representation, the values of these parameters being dependent on the location of the graphical element in the modified graphical representation, and means for programming the medical device with the new and/or modified parameters.

By means of this arrangement, parameters for the control of the medical device are linked to a graphical representation, which can then be modified or customised by an operator by the addition of further graphical elements representing the effects of functions of the device. The operator can therefore generate a modified graphical representation illustrating the influence of the medical device on the quantity. The operator is effectively able to select parameters on the basis of the effect intended, rather than setting parameters numerically and then observing the effect in operation. The resulting system is thus not only more intuitive and thus easier to use for a medical practitioner, it will also be safer for the patient, since there is less likelihood of the operator programming unsuitable parameter values.

Preferably the quantity is a measurable physiological activity commonly used for evaluating the condition of the patient. For example, when the medical device is a cardiac stimulating device, a useful quantity for use in programming the device control parameters is the electrical activity of the heart in the form of an electrocardiogram (ECG) or intracardial electrogram (IEGM), which is commonly measured by the device or the programmer and serves as an important diagnostic tool for evaluating the condition of the patient and the operation of the implanted device. Other waveforms, for example showing the variation of the quantity over time, are also useful for programming parameter values.

When the medical device is a cardiac stimulating device the graphical elements preferably include an electrical pulse generated by the medical device for stimulating a patient's heart. More specifically, the graphical element preferably includes an atrial stimulation pulse and/or a ventricular stimulation pulse. The modified graphical representation thus illustrates the electrical activity of a paced heart. In this case the new and/or modified parameters include a basic pacing rate and/or an AV interval.

In addition to showing the graphical elements, such as an atrial and/or ventricular stimulation pulse, the modified graphical representation may also show other variations in the quantity resulting from the addition of the graphical elements. For example, the timing in an ECG waveform may be modified to better reflect the influence of a pacing pulse. Similarly, the expected ventricular depolarization may be shown on the modified graphical representation. Obviously, some implanted devices will only permit specific discrete parameter values to be used. The programming arrangement thus advantageously includes means for setting a nearest authorised modified parameter value in response to the modification of the graphical representation.

The graphical representation may be a stored representation of the quantity and to this end the arrangement includes storage means. Advantageously, however, the arrangement includes means for collecting data relating to said quantity, and means for constructing a graphical representation of said quantity for display. In this way any desired effect expressed by the modification of the graphical representation will be more closely related to the actual effect achieved during operation of the medical device.

The invention further relates to a method for controlling the operation of an implantable medical device, including the steps of: displaying a graphical representation of a quantity that can be influenced by the operation of the medical device, mapping parameters relating to the control of the device onto portions of the graphical representation, enabling the addition of at least one graphical element to the graphical representation, the graphical element representing a variation in the quantity that can be produced by functions of the implantable medical device, displaying a modified graphical representation including the graphical element and generating new and/or modified parameters in response to the modified graphical representation, the values of the parameters being dependent on the position of the graphical element in the modified graphical representation, and programming the medical device with the new and/or modified parameters. In accordance with a further aspect of the invention, the above object is achieved by a computer program product as defined in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS Further objects and advantages of the present invention will become apparent from the following description of the preferred embodiments that are given by way of example with reference to the accompanying drawings. In the figures:

Fig. 1 schematically shows a system for programming a medical device in accordance with the present invention,

Fig. 2a and 2b show a basic and modified graphical representation displayed on the display of the system of Fig. 1 for use in programming the medical device in accordance with a first embodiment of the invention,

Fig. 3 a to 3 c show basic graphical representations displayed on the display of the system of Fig. 1 for use in programming the medical device in accordance with a second embodiment of the invention, and

Fig. 4a to 4c show modified graphical representations displayed on the display of the system of Fig. 1 in accordance with the second embodiment of the invention. DETAILED DESCRIPTION OF THE DRAWINGS

Fig. 1 schematically shows an arrangement for programming an implanted medical device. In the illustrated embodiment, the medical device is a cardiac pacer implanted in a patient. The pacer comprises a pacer control unit 10, which is generally implanted near the shoulder of the patient under the skin and one or more electrodes 14, which are anchored in the patient's heart 5. A lead 12 connects each electrode 14 to the pacer control unit 10. The pacer is capable of operating autonomously and is powered by a battery (not shown).

The electrodes 14 are used to apply stimulating pulses to the heart tissue and also sense the electrical activity of the heart and possibly other physiological activities, such as respiration and relay this information to the pacer control unit 10. The pacer control unit 10 stores this information, for example in the form of an intracardial electrogram (IEGM) for later consultation by a medical practitioner during a routine check-up. Other information collected and stored in the pacer control unit 10 can include data relating to the condition of the pacer, such as the residual battery power or the impedance of the leads 12. The information stored in a pacer can be consulted using a programmer 20, which is preferably computer-, or microprocessor based.

The programmer 20 includes a control unit 22, a display 24, a telemetry head 26, internal storage means 28 and some form of data input device 30 that may be a keyboard, a mouse, a touch-sensitive screen, some combination of these or similar. A disk drive 32 may also be provided in the programmer 20 for receiving a diskette, CD-ROM or similar portable storage element capable of carrying computer-readable code. Software used for controlling the operation of the programmer is stored in the storage means 28 and executed by the control unit 22 using the storage means 28. Additional software applications can be provided on a removable diskette and read with the aid of the disk drive 32. These additional software applications may be used to extend the functions of the programmer, for example to allow a different class of pacer device 10 to be programmed. Alternatively, additional software applications may assure more basic functions that are specific to a class of implantable device; this may be of interest when the internal storage means 28 of the programmer 20 are of limited capacity, for example. Communication between the programmer 20 and the pacer control unit 10 is effected via a telemetry link, whereby the telemetry head 26, which preferably includes an inductive coil, is placed over the implantation site of the pacer control unit 10. Once a link has been established, the programmer 20 interrogates the pacer control unit 10 and downloads the stored information. Modifications to the pacer settings programmed by the programmer 20 are also uploaded to the pacer control unit via the telemetry link. The exchange of information between the pacer control unit 10 and the programmer 20 may occur throughout a programming session, for example to obtain recent ECG or IEGM signals recorded by the pacer 10 when testing a modified parameter value.

Interaction between the operator and the programmer 20 is through the display 24 and input device 30 and more particularly through a software application that provides a graphical user interface of the programmer 20. Through the graphical user interface, the operator may use the programmer 20 to set programmable parameter values, carry out tests on the implantable device and also view diagnostic data.

In accordance with the present invention, the programmer 20 displays parameter values in graphical form. More specifically, the programmer 20 displays a representation of a quantity that is influenced by the operation of the implanted medical device. Preferably this quantity is also measured by the implanted medical device 10. Preferably the quantity represents a physiological activity influenced by the device 10 and commonly used by a clinician for evaluating the patient's condition and also the operation of the implanted device 10. The parameters used for controlling the operation of the medical device are mapped to this representation in such a way that the relative dimensions of parts of the representation indicate to the operator the relative magnitudes of the mapped parameters.

The representation of a physiological activity is preferably in the form of a waveform. In the present example, which relates to a cardiac pacer 10, the waveform illustrates the electrical activity of the heart and is essentially an ECG or IEGM signal. These signals are routinely used by medical practitioners to evaluate both a patient's condition and the operation of an implanted pacer during programmer sessions. Data representing the measured electrical activity of the heart in the form of an ECG or IEGM is also readily available from the pacer device itself. By displaying parameters in such a graphical form, and moreover, permitting the modification of parameters by manipulating the graphical representation, the operator is able immediately to visualise what effect the programmed parameters will have on the patient's condition.

An example of such a graphical representation is shown in Fig. 2a. Fig. 2a illustrates the image that is displayed on the display 24 by the graphical user interface when the operator selects the commencement of programming the implanted pacer 10. The graphical representation is a waveform 100 representing the electrical activity of a heart cycle against time. This is essentially one cycle of an electrocardiogram (ECG) recording of normal, i.e. spontaneous, heart activity. The waveform includes a P wave 101, representing atrial depolarization, an R wave 102 representing ventricular depolarization and a T wave 103, which represents ventricular repolarization. This waveform is essentially an ideal spontaneous heart rhythm. At the side of the screen, two further vertical lines 105, 106 are illustrated, each representing an electrical impulse in the ECG signal. These lines represent a pacing stimulus pulse delivered to the atrium of the heart and a ventricular stimulus pulse. Each of these lines is individually selectable and movable by the operator. This may be done by means of a cursor-moving device, such as a mouse, or by inputting commands through a keyboard. The operator is requested to select one of these lines and to place it at the desired location on the ECG waveform 100. The resulting modified waveform 100' is shown in Fig. 2b. The atrial stimulus pulse 105 is accordingly positioned on curve 100' before the P wave 101. The ventricular stimulus pulse 106 is located to the right of the atrial pulse 105, indicating a delay in time. Although not indicated in Fig. 2b, the dimensions of curve 100' may also be modified relative to the basic curve 100 to reflect the influence of the pacing pulses 105, 106 on the depolarization of the heart chambers. Accordingly, the R wave 102 would be modified to follow the ventricular pulse 106. Several programmable parameter values are mapped to the modified waveform 100'. Specifically, these parameters are associated with the various relative dimensions of the waveform. A simple example is the distance separating the inserted atrial and ventricular stimulus pulses 105, 106, which is mapped to real values in time defining the AV interval. Similarly the basic rate of the pacer will be determined by the placement of the stimulus pulses 105, 106. As the stimulus pulses 105, 106 are added to the waveform, the programmer calculates these various parameter values associated with the positions of the pacing pulses 105, 106. These values may also be displayed to the user in numerical format in a small overlaid window as the user is positioning the lines 105, 106. After the operator has terminated the modification of the waveform 100' to obtain a desired effect, the programmer control unit 22 sets the associated selected parameter values and downloads the same to the pacer control unit 10 through the telemetry head 26. These modified parameter values will then be used by the pacer device 10 in operation. The lines 105, 106 are preferably identified on the screen as being an atrial or ventricular stimulus pulse, so that the programmer control unit 22 can determine whether the pulse is placed in the correct region of the curve 100'.

The option to select the stimulus pulse lines 105, 106 will depend on the configuration of the pacer. Single chamber systems clearly require only either an atrial or a ventricular pulse. This fact can be reflected in the programmer's graphical user interface, which can be adapted to display only the appropriate pulse to the operator after the routine identification of the pacer device and its configuration at the start of communication between the programmer 20 and the pacer control unit 10.

In an alternative arrangement, the display 24 does not display separate lines representing the atrial and/or ventricular pacing pulses 105, 106 that may be selected and moved. Instead, the user interface instructs the operator to indicate a position on the curve 100 for inserting an atrial and/or ventricular stimulus pulse. The relative dimensions of the waveform 100 will then be modified as described above to take account of the selected positions resulting in a modified waveform 100'. Preferably the stimulus pulses 105, 106 will also be automatically shown on the modified waveform 100' so that the operator can see immediately on the display 24 the effect of positioning the stimulus pulses.

The modified waveform 100' depicted in Fig. 2b illustrates a case for a dual chamber pacer when both an atrial and ventricular stimulus pulse are delivered to the heart. However, if a heart can sustain some spontaneous activity, it is often preferable to inhibit the corresponding pacing pulse and allow the spontaneous activity to drive the heart for as long as possible. Such spontaneous activity may occur only infrequently and the form it takes may also vary. Accordingly, the pacer device must be capable of reacting to different types of cardiac activity. As described with reference to Fig. 1 the pacer electrodes 14 sense electrical activity as well as delivering stimulus pulses. If spontaneous activity is sensed in a time window prior to the delivery of a stimulus pulse, this pulse may be inhibited. This function may also be programmed by means of a graphical representation of an ECG or IEGM signal. This is illustrated in Figs. 3a to 3c and Fig. 4a to 4c.

Figs. 3a to 3c shows three waveforms 300, 400, 500 representing activity of a patient's heart measured by the pacer device 10. The operator is asked to define the positions in time when stimulus pulses should be delivered after the pacer device detects these waveform patterns. The waveforms include in Fig. 3a a spontaneous heart cycle 300 including a P wave 301, R wave 302 and T wave 303. In Fig. 3b a waveform 400 is illustrated which includes only a P wave; no spontaneous ventricular activity is present. Finally in Fig. 3c the display 24 presents a waveform 500 to the operator that includes a P-wave without following ventricular activity (cf. Fig.3a) but then a premature ventricular contraction 304. As for the waveform in Fig. 2a, the operator is invited to place the stimulus pulses where these are required in the three waveforms 300, 400, 500 of Figs. 3a to 3c. This is shown in Fig. 4a to 4c. In

Fig. 4a no stimulus pulses are added to the waveform 300 of Fig. 3a. The timing of the spontaneous activity presented in the waveform of Fig. 3 a is considered acceptable to drive both chambers of the heart. Thus no stimulus pulses are added and the waveform 300' in Fig. 4a corresponds to that of Fig. 3 a. Naturally if the operator wished to ensure that the heart is paced even when spontaneous activity is present, or to change the rhythm, for example when the spontaneous ventricular depolarization is too long, stimulus pulses could be inserted. In the waveform 400 of Fig. 3b containing only a P-wave 301 a ventricular stimulus pulse 306 has been inserted resulting in the modified waveform 400' of Fig 4b. In addition to displaying the added stimulus pulse 306, the modified waveform 400' also includes the expected ventricular depolarization 307 resulting from this ventricular stimulus pulse 306 shown with a dashed line. A ventricular stimulus pulse 306 has also been added to the waveform 500 of Fig. 3 c resulting in the modified waveform 500' shown in Fig. 4c. The expected ventricular depolarization 307 following the stimulus pulse 306 is again shown as a dashed line. Delivering a ventricular stimulation pulse after the P wave is expected to prevent the reoccurrence of the premature ventricular contraction 304 (PVC) present in the waveform 500 of Fig. 3c. The PVC 304 is thus not present in the modified waveform 500' of Fig. 4c. After the operator has terminated the modification of the waveforms

300, 400, 500 to obtain the desired result and the programmer control unit 22 has determined the associated selected parameter values, these values are downloaded to the pacer control unit 10 through the telemetry head. In operation, the pacer will apply the programmed parameter values associated with the corrected waveforms 300', 400', 500' illustrated in Figs. 4a to 4c in a pacing cycle immediately following the corresponding detected heart rhythms shown in Figs. 3a to 3c.

The basic waveforms 100, 300, 400, 500 of the kind illustrated in Figs. 2 and 3a to 3c are stored in the storage means 28. These waveforms may be stylised pre-programmed waveforms either contained in the programmer storage means 28 or loaded directly via the disk drive 32. Alternatively, the waveforms may be generated by the programmer from data recorded by the pacer 10 as an intracardial electrogram (IEGM) signal and downloaded to the programmer 20 through the telemetry link 26. The waveforms may be constituted by a single recorded IEGM cycle or be generated using several recorded cycles to create an average recorded cycle. Most pacers have a restricted number of discrete programmable parameter values. The programmer thus selects the nearest allowable value that corresponds to the relative dimensions of the modified waveform.

By illustrating heart rhythms in the form of a waveform and allowing the operator to modify these waveforms in accordance with the desired pacer behaviour by adding stimulus pulses or other elements, an immediate and clear picture is generated of the operation of the pacer. The associated parameters are mapped to the waveform by the programmer without the intervention of the operator. The operator thus selects the effect of a pacer program. The programming of individual parameter values associated with the generated waveform is hidden from the operator, rendering the programming process simple and intuitive.

Claims

1. An arrangement for monitoring and controlling the operation of an implantable medical device (10), characterised by: means (26) for communicating with said medical device (10), means (22, 24) for displaying a graphical representation of at least one quantity that can be influenced by the operation of said medical device and associating parameters relating to the control of the device with portions of said graphical representation, means (22, 30) for enabling the addition of at least one graphical element to said graphical representation to generate a modified graphical representation, wherein said graphical element represents a variation in said at least one quantity that can be produced by functions of said implantable medical device, means (22) responsive to said modification for generating new and/or modified parameters associated with said modified graphical representation, the values of said parameters being dependent on the location of said graphical element in said modified graphical representation, and means (22, 26) for programming said medical device with said new or modified parameters.

2. An arrangement as claimed in claim 1, characterised in that said quantity is a measurement of at least one physiological activity influenced by said medical device.

3. An arrangement as claimed in claim 1 or 2, characterised in that said graphical representation includes a waveform representing the variation of said quantity against time.

4. An arrangement as claimed in any previous claim, characterised in that the graphical representation is a curve representing an electrocardiogram (ECG) or intracardial electrogram (IEGM) signal of at least one cardiac cycle.

5. An arrangement as claimed in claim 4, characterised in that said medical device is a cardiac stimulating device (10) and said graphical element (105, 106, 306) includes an electrical pulse generated by said medical device for stimulating a patient's heart.

6. An arrangement as claimed in claim 4 or 5, characterised in that said graphical element (105, 106, 306) includes an atrial stimulation pulse and/or a ventricular stimulation pulse.

7. An arrangement as claimed in claim 6, characterised in that said new and/or modified parameters include at least one of a basic pacing rate and an AV interval.

8. An arrangement as claimed in any previous claim, characterised in that storage means (28) are provided for storing said graphical representations.

9. An arrangement as claimed in any previous claim, characterised by means (26, 10) for obtaining measured data relating to said quantity, and means (22) for constructing said graphical representation from said measured data.

10. An arrangement as claimed in any previous claim, characterised by means (22) for generating a nearest authorised modified or new parameter value in response to the generated modified graphical representation.

11. A method for controlling the operation of an implantable medical device, characterised by the steps of: displaying a graphical representation of a quantity that can be influenced by the operation of said medical device, mapping parameters relating to the control of the device onto portions of said graphical representation, enabling the addition of at least one graphical element to said graphical representation, said graphical element representing a variation in said quantity that can be produced by functions of said implantable medical device, displaying a modified graphical representation including said graphical element and generating new and/or modified parameters in response to said modified graphical representation, the values of said parameters being dependent on the position of said graphical element in said modified graphical representation, and programming said medical device with the new and/or modified parameters.

12. A method as claimed in claim 11, characterised in that said mapping step includes mapping parameter magnitudes with selected dimensions of said graphical representation.

13. A method as claimed in claim 11 or 12, characterised by generating said graphical representation from a plurality of measured curves and/or values.

14. A method as claimed in any one of claims 11 to 14, characterised by displaying a measurement of at least one physiological activity as said graphical representation.

15. A method as claimed in any one of claims 11 to 14, characterised by displaying a waveform representing the variation of said quantity against time as said graphical representation.

16. A method as claimed in claim 15, characterised in that said waveform represents at least one cycle of an electrocardiogram (ECG) or intracardial electrogram (IEGM) signal.

17. A method as claimed in claim 16, characterised in that said waveform represents at least one cycle of an electrocardiogram (ECG) or intracardial electrogram (IEGM) signal showing a faulty heart rhythm.

18. A method as claimed in any one of claims 11 to 17 characterised by modifying said graphical representation to show the influence on said quantity of adding said graphical element.

19. A computer program product, characterised by computer readable code, which when loaded in digital processing means causes the execution of the method as claimed in any one of claims 11 to 18.

20. A computer readable storage medium carrying a computer program product as claimed in claim 19.