IMPLANTABLE MEDICAL DEVICE

• US 20100292550A1
• Filed: 12/21/2007
• Published: 11/18/2010
• Est. Priority Date: 12/21/2007
• Status: Active Grant

• Current Assignee: St. Jude Medical AB (Abbott Laboratories Incorporated)
• Original Assignee: St. Jude Medical AB (Abbott Laboratories Incorporated)
• Inventors: Björling, Anders, Holmström, Nils, Snitting, Tomas, Abrahamson, Hans
• Granted Patent: US 8,433,385 B2
• Time in Patent Office: Days
• US Class Current: 600/345
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61N 1/36557 controlled by chemical substances in blood

Abstract

An analyte measuring system has an implantable medical device having a signal source arranged for generating a current signal and electrodes for applying the current signal to a surrounding tissue in a subject body. The device measures a resulting voltage signal with the electrodes and calculates an impedance signal therefrom. The system comprises a signal processor arranged for generating an estimate of a concentration of an analyte in the tissue based on a spectrum analysis of the determined impedance signal.

Claims

1. An analyte measuring system comprising:

an implantable medical device comprising;

an electrode connecting arrangement (110) connectable to at least two implantable electrodes;

a signal source that generates an current or voltage signal and for applying said current or voltage signal to a tissue using said at least two implantable electrodes;

a signal measurer that measures a resulting voltage or current signal from said tissue sensed by said at least two implantable electrodes; and

an impedance determiner that determines an impedance signal based on said generated current or voltage signal and said measured resulting voltage or current signal; and

a signal processor that generates an estimate of a concentration of an analyte in said tissue by making a spectral analysis of said impedance signal determined by said impedance determiner.

2. The system according to claim 1, wherein

said signal source is a frequency tunable signal source that sweeps a frequency of said current or voltage signal over a frequency range to obtain multiple current or voltage signals of different frequencies in said frequency range;

said signal measurer measuring multiple resulting voltage or current signals from said tissue sensed by said at least two implantable electrodes;

said impedance determiner determines said impedance signal based on at least a portion of said generated multiple current or voltage signals and said measured multiple resulting voltage or current signals; and

said signal processor generates said estimate of said concentration of said analyte based on an analysis of at least a frequency portion of said impedance signals.

3. The system according to claim 1, wherein

said signal source generates a composite current or voltage signal having a defined bandwidth covering a frequency range;

said signal measurer measures a resulting composite voltage or current signal from said tissue sensed by said at least two implantable electrodes;

said impedance determiner determines said impedance signal based on said generated composite current or voltage signal and said measured composite resulting voltage or current signal; and

said signal processor generates said estimate of said concentration of said analyte based on an analysis of said impedance signal at multiple selected frequencies in said frequency range obtained by bandpass filtering said impedance signal.

4. The system according to claim 1, wherein said implantable medical device comprises a transmitter with a connected transmitting antenna for transmitting a representation of said impedance signal to a non-implantable device comprising a receiver with a connected receiving antenna that receives said representation, wherein said signal processor is arranged in said non-implantable device.

5. The system according to claim 1, wherein said signal processor is arranged in said implantable medical device.

6. The system according to claim 1, wherein said signal processor generates an estimate of a concentration of a peptide or protein analyte in said tissue based on said spectral analysis.

7. The system according to claim 6, wherein said peptide or protein analyte is selected from the group consisting of:

B-type natriuretic peptide, BNP;

atrial natriuretic peptide, ANP;

troponin;

myoglobin; and

creatine kinase.

8. The system according to claim 1, wherein said signal source generates said current or voltage signal of a bandwidth comprising an absorbance frequency characteristic of said analyte.

9. The system according to claim 1, wherein said signal source generates multiple current or voltage signals of covering a frequency range comprising an absorbance frequency characteristic of said analyte.

10. The system according to claim 1, wherein said signal source generates said current or voltage of at least one frequency in a range of 1 MHz to 1 THz.

11. The system according to claim 10, wherein said signal source generates said current or voltage of at least one frequency in a range of 10 MHz to 10 GHz.

12. The system according to claim 11, wherein said signal source generates said current or voltage of at least one frequency in a range of 100 MHz to 10 GHz.

13. The system according to claim 1, wherein said signal processor generates said estimate of said analyte concentration based on a ratio an amplitude of said impedance signal at a first frequency and an amplitude of said impedance signal at a second frequency.

14. The system according to claim 13, wherein said signal processor generates said estimate of said analyte concentration based on a comparison of said ratio and a corresponding ratio determined by said signal processor based on a spectral analysis of a reference impedance signal determined based on a previously applied current or voltage signal and a previously measured resulting voltage or current signal.

15. The system according to claim 1, wherein said implantable medical device further comprises:

a signal analyzer generates a representation of a variation in intrinsic body activity based on a sensed electrical signal from a tissue; and

a signal controller that generates a synchronization signal based on said representation of said variation in intrinsic body activity and forwards said synchronization signal to said signal source, said signal source responding to said synchronization signal and generates said current or voltage signal based on said synchronization signal.

16. The system according to claim 1, wherein said implantable medical device further comprises comprising:

a body posture sensor that generates a representation of a body posture of a subject in whom said implantable medical device is implanted;

a signal controller that generates a synchronization signal based on said representation of said body posture and forwarding said synchronization signal to said signal source, said signal source responding to said synchronization signal by generating said current or voltage signal based on said synchronization signal.

17. The system according to claim 1, wherein said implantable medical device is selected from a group consisting of:

a pacemaker;

a cardiac defibrillator; and

a cardioverter.

18. The system according to claim 1, wherein

said signal source generates and supplies a first current or voltage signal to said tissue using a first set of two implantable electrodes of said at least two implantable electrodes, and generates and applies a second current or voltage signal to said tissue using a second set of two implantable electrodes of said at least two implantable electrodes, at least one implantable electrode of said second set being different from said two implantable electrodes of said first set;

said signal measurer measures a first resulting voltage or current signal from said tissue sensed by two first implantable electrodes of said at least two implantable electrodes, and measures a second resulting voltage or current signal from said tissue sensed by two second implantable electrodes of said at least two implantable electrodes, said two second implantable electrodes can be the same or different from said two first implantable electrodes;

said impedance determiner generates a first impedance signal based on said first current or voltage signal and said first resulting voltage or current signal and a second impedance signal based on said second current or voltage signal and said second resulting voltage or current signal; and

said signal processor generates said estimate of said concentration based on a spectral analysis of said first impedance signal and said second impedance signal.

19. An analyte estimating method comprising:

generating a current or voltage signal;

applying said current or voltage signal to a tissue using two implantable electrodes;

sensing a resulting voltage or current signal from said tissue using two implantable electrodes;

determining an impedance signal based on said generated current or voltage signal and said sensed resulting voltage or current signal; and

generating an estimate of a concentration of an analyte in said tissue by making a spectral analysis of said impedance signal.

20. The method according to claim 19, wherein

said signal generating step comprises sweeping a frequency of said current or voltage signal over a frequency range to obtain multiple current or voltage signals of different frequencies in said frequency range;

said sensing step comprises sensing multiple resulting voltage or current signals from said tissue using said two implantable electrodes;

said determining step comprises determining said impedance signal based on at least a portion of said generated multiple current or voltage signals and said measured multiple resulting voltage or current signals; and

said estimate generating step comprises generating said estimate of said concentration of said analyte based on an analysis of at least a frequency portion of said impedance signals.

21. The method according to claim 20, wherein

said signal generating step comprises generating a composite current or voltage signal having a defined bandwidth covering a frequency range;

said sensing step comprises sensing a resulting composite voltage or current signal from said tissue using said two implantable electrodes;

said determining step comprises determining said impedance signal based on said generated composite current or voltage signal and said measured composite resulting voltage or current signal; and

said estimate generating step comprises generating said estimate of said concentration of said analyte based on an analysis of said impedance signal at multiple selected frequencies in said frequency range obtained by bandpass filtering said impedance signal.