MEDICAL DEVICE AND METHOD FOR EVALUATING DATA FOR DEFECTS IN AN ELECTRODE LEAD

Abstract

A medical device has at least one electrode lead with at least one electrode pole that is configured to measure electrical potentials in human or animal tissue, and a measurement and control unit that is connected to the electrode lead. The measurement and control unit is configured to initiate measurements of the impedance via the electrode pole of the electrode lead. The measurements of the impedance have at least one individual measurement, an individual measurement occurring over a defined window of time.

Claims

1. A medical device, comprising: at least one electrode lead having at least one electrode pole, said electrode lead configured to measure electrical potentials in human or animal tissue; and a measurement and control unit connected to said electrode lead, said measurement and control unit configured to initiate measurements of impedance via said electrode pole of said electrode lead, the measurements of impedance have a plurality of individual measurements, and one individual measurement occurs over a defined window of time, and changes in impedance above a specific slew rate are detected and evaluated.

2. The medical device according to claim 1, wherein the defined window of time is 5 seconds to 360 seconds in length.

3. The medical device according to claim 1, wherein each of the individual measurements is a recording of impedance values by means of a sampling frequency, the sampling frequency being between 8 Hz and 128 Hz.

4. The medical device according to claim 1, wherein there being a defined time period of 0.5 hours to 24 hours between two individual measurements.

5. The medical device according to claim 4, wherein the defined time period is 1 hour between the individual measurements.

6. The medical device according to claim 1, wherein: said measurement and control unit evaluates measured impedance values; or the medical device is configured to provide the measured impedance values to an external device or to an external service center, where they are evaluated.

7. The medical device according to claim 6, wherein the measured impedance values being evaluated in that the measured impedance values or differential values between the measured impedance values are compared to a threshold value, the threshold value being a predefined value, or the threshold value being a value that is updated regularly using current impedance measurements, the medical device being configured to transmit stored impedance values and/or the differential values to the external device or to the external service center.

8. The medical device according to claim 7, wherein a differential value is calculated between two discrete, successive impedance values.

9. The medical device according to claim 1, further comprising a right ventricular shock coil, further comprising an atrial shock coil; further comprising a ring electrode; further comprising a tip electrode connected to said electrode lead; wherein said electrode pole is associated with one of said right ventricular shock coil, said atrial shock coil, said ring electrode, or said tip electrode of said electrode lead; further comprising a device housing having a further electrical pole; wherein said measurement and control unit is connected to said electrode pole and said further electrical pole of said device housing; and wherein said measurement and control unit is configured to conduct measurements of the impedance between said electrode pole and said further electrical pole of said device housing.

10. The medical device according to claim 9, wherein: said electrode lead is one of a plurality of electrode leads; and/or said electrode lead has a plurality of electrode poles; and said measurement and control unit is configured to conduct a measurement of the impedance between two of said electrode poles, wherein said two electrode poles have at least a combination of said electrode poles and/or said further electrical pole of said device housing.

11. The medical device according to claim 10, wherein impedance values are evaluated individually for each combination of said electrode poles and/or said further electrical pole of said device housing.

12. The medical device according to claim 6, wherein said measurement and control unit is configured to increment a counter value for an individual measurement when a threshold value is exceeded by the measured impedance values or by a calculated differential value, and to store the measured impedance values when a counter limit is exceeded.

13. The medical device according to claim 12, wherein said measurement and control unit is configured to store the measured impedance values of an individual measurement from a series of individual measurements, the individual measurement represents the individual measurement from the series of individual measurements that has a highest counter value, or represents a chronologically first individual measurement from the series of individual measurements for which the counter limit was exceeded.

14. The medical device according to claim 12, wherein the measured impedance values are stored within a sub-window of time, the sub-window of time being linked to a time at which the counter limit is exceeded.

15. A method for evaluating impedance values for defects in an electrode lead, which comprises the steps of: measuring an impedance using an electrode pole of the electrode lead; and evaluating measured impedance values for defects in the electrode lead, wherein measurements of the impedance have at least one individual measurement, and the one individual measurement occurs across a defined window of time.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0069] FIG. 1 is an illustration depicting an exemplary embodiment of the present invention using a stimulation device having a ring electrode and a tip electrode;

[0070] FIG. 2 is an illustration depicting an exemplary embodiment of the present invention using a stimulation device having a ring electrode, a tip electrode, and a shock coil; and

[0071] FIG. 3 is an illustration depicting an exemplary embodiment of the present invention using a stimulation device having a ring electrode, a tip electrode, and two shock coils.

DETAILED DESCRIPTION OF THE INVENTION

[0072] Functionally equivalent or identically acting elements in the figures are provided the same reference numbers. The figures are schematic representations of the invention. They do not illustrate specific parameters of the invention. Moreover, the figures merely reflect typical embodiments of the invention and shall not limit the invention to the illustrated embodiments.

[0073] Referring now to the figures of the drawings in detail and first, particularly to FIG. 1 thereof, there is shown an exemplary embodiment of the present invention using a stimulation device 10 having a ring electrode 3 and a tip electrode 2. Specific embodiments are implantable cardiac pacemakers, brain pacemakers, spinal cord stimulators, and the like. The stimulation device 10 comprises a device housing 1, the tip electrode 2, the ring electrode 3, and electrical lines 6 for the electrodes. According to the invention, the impedance may be measured for detecting defects in the electrode, electrode conductors, or insulation, for example via

a) Derivation 11 (between tip electrode 2 and ring electrode 3) and/or
b) Derivation 12 (between ring electrode 3 and device housing 1).

[0074] FIG. 2 depicts an exemplary embodiment of the present invention using a stimulation device 20 having the ring electrode 3, the tip electrode 2, and a shock coil 4. One specific embodiment is an implantable cardioverter defibrillator (ICD). The stimulation device 20 comprises the device housing 1, the tip electrode 2, the ring electrode 3, the shock coil 4, and the electrical leads 6 for the electrodes. According to the invention, the measurement of the impedance for detecting defects in the electrode, electrode lead, or insulation may be conducted, for instance, using:

a) Derivation 11 (between tip electrode 2 and ring electrode 3), and/or
b) Derivation 12 (between ring electrode 3 and device housing 1), and/or
c) Derivation 13 (between tip electrode and shock coil 4), and/or
d) Derivation 14 (between shock coil 4 and device housing 1).

[0075] FIG. 3 depicts one exemplary embodiment of the present invention using a stimulation device 30 having a ring electrode, a tip electrode, a shock coil 4, and another shock coil 5. One specific embodiment is an implantable cardioverter defibrillator (ICD) having a right ventricular shock coil and an SVC shock coil. The stimulation device 30 comprises the device housing 1, the tip electrode 2, the ring electrode 3, the shock coil 4, shock coil 5, and the electrical lines 6 for the electrodes. According to the invention, the measurement of the impedance for detecting defects in the electrode, electrode lead, or insulation may be conducted, for example, using:

a) Derivation 11 (between tip electrode 2 and ring electrode 3), and/or
b) Derivation 12 (between ring electrode 3 and device housing 1), and/or
c) Derivation 13 (between tip electrode and shock coil 4), and/or
d) Derivation 14 (between shock coil 4 and device housing 1), and/or
e) Derivation 15 (between shock coil 5 and device housing 1), and/or
f) Derivation 16 (between shock coil 4 and shock coil 5).

[0076] According to one aspect of the invention, changes in impedance above a specific slew rate are detected and evaluated. According to one embodiment of the invention, a differential value between two discrete, successive impedance values is preferably calculated for the signal evaluation. According to one example, measurements of the impedance are conducted between every two electrical poles, the two poles comprising at least a combination of the following:

a) Right ventricular coil electrode and device housing,
b) Right ventricular coil electrode and right ventricular tip electrode,
c) Right ventricular ring electrode and device housing,
d) Right ventricular ring electrode and right ventricular tip electrode,
e) SVC coil electrode and device housing, and/or
f) SVC coil electrode and right ventricular coil electrode.

[0077] According to one preferred embodiment of the invention, the measurement and control unit is configured to increment a counter value for an individual measurement when a threshold value is exceeded by the calculated differential value, and to store the measured impedance values when a counter limit is exceeded.

[0078] According to one aspect of the invention, the aforesaid threshold value is a function of the observed derivation.

[0079] According to one embodiment in which the medical device is preferably embodied as an implantable cardiac therapy device, at least one counter for the specific derivation may be incremented when the impedance difference by sample is measured higher than:

a) Right ventricular coil electrode and device housing: approx. or exactly 24 Ohms,
b) Right ventricular coil electrode and right ventricular tip electrode: approx. or exactly 78 Ohms,
c) Right ventricular ring electrode and device housing: approx. or exactly 78 Ohms,
d) Right ventricular ring electrode and right ventricular tip electrode: approx. or exactly 137 Ohms,
e) SVC coil electrode and device housing: approx. or exactly 24 Ohms, and/or
f) SVC coil electrode and right ventricular coil electrode: approx. or exactly 40 Ohms.

[0080] According to one embodiment, the frequency of these events per time segment (e.g. day) is counted and evaluated.

[0081] According to one embodiment, alternatively or in addition to the above described embodiment, the absolute impedance may be compared, by sample, to an absolute threshold value. The absolute threshold value may be parameterized specifically for the electrode used or may be automatically continuously revised from the previous measurements (e.g. from trend data).

REFERENCE SIGNS

[0082] 1 Device housing [0083] 2 Tip electrode [0084] 3 Ring electrode [0085] 4 Shock coil [0086] 5 Shock coil [0087] 6 Electrode leads [0088] 10 Medical device [0089] 11 Derivation from tip electrode 2 to ring electrode 3 [0090] 12 Derivation from ring electrode 3 to device housing 1 [0091] 13 Derivation from tip electrode to shock coil 4 [0092] 14 Derivation from shock coil 4 to device housing 1 [0093] 15 Derivation from shock coil 5 to device housing 1 [0094] 16 Derivation from shock coil 4 to shock coil 5 [0095] 20 Medical device [0096] 30 Medical device

ABBREVIATIONS AND DEFINITIONS OF TERMS

[0097]

TABLE-US-00001 Derivation/measurement In the context of the invention, derivation and derivation measurement derivation shall be construed to mean a recorded measurement signal that corresponds to the course of the electrical potential from one measurement electrode to a second measurement electrode or to a neutral electrode. Distal end For an electrode lead, the end that is arranged farthest from the device housing. ECG Electrocardiograph Electrode/electrode pole In the context of the invention, electrode and electrode pole shall be construed to mean a metal unit connected to an electrode lead, the unit, in combination with a second electrode or a counterelectrode, permitting recording of voltage potentials or current to be output. Electrode lead In the context of the invention, an electrode lead shall be construed to mean a line made of electrically conducting material. Electrodes or electrode poles for measuring voltage potentials or for outputting current may disposed at the end of or along the electrode lead. As a rule, an electrode lead is formed from a plurality of electrode conductors that are insulated from one another. ICD Implantable cardioverter defibrillator IEGM Intrakardiales Elektrogram (English: intracardial electrogram) Intermittent In the context of the invention, intermittent shall be construed to describe a temporary and non-continuous event. Insulation Insulation shall be construed to be the means for electrically insulating an electrode lead. Proximal end For an electrode lead, the end that is coupled to the device housing. Semi-continuous In the context of the invention, semi-continuous describes a measurement that takes place continuously over a certain time period or over a certain window of time. In the case of measurements of impedance values that are detected by sample via a sample frequency, from a purely technical perspective this is not a continuous measurement (as would be the case for an analog measurement signal) - therefore the term semi- continuous. The invention shall not be limited to a semi-continuous measurement of impedance, however. SCS Spinal cord stimulation/spinal cord stimulator Sensing In the context of the invention, the term sensing shall be construed to mean the detection of physiological signals by measuring electrical potentials. SVC Superior Vena Cava TENS Transcutaneous electrical nerve stimulation VNS Vagus nerve stimulation