Method and apparatus for muscle function measurement

• US 20060167358A1
• Filed: 01/26/2005
• Published: 07/27/2006
• Est. Priority Date: 01/26/2005
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Bennett, Tommy D., Karamanoglu, Mustafa, Splett, Vincent E.
• Granted Patent: US 7,470,233 B2
• Time in Patent Office: Days
• US Class Current: 600/485
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: A61B 5/4519 Muscles A61B5/389, A61B5/224 take precedence
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives

Abstract

The present invention provides an apparatus and method for monitoring muscle function based on an index derived from a pressure or force signal. The muscle function index is derived from an instantaneous muscle stiffness ratio computed as the ratio of the first time derivative of the pressure or force waveform to the corresponding instantaneous pressure or force. The instantaneous stiffness ratio, {dot over (E)}/E(t), is in units of 1/sec and relates to the rate of strong bond formation and will be influenced by calcium handling properties of the muscle fibers and the intracellular calcium concentration. As such, an index derived from {dot over (E)}/E(t) provides a measure of the inotropic status of the muscle.

Claims

1. A method, comprising:

sensing a pressure signal produced at least in part from a muscular contraction event;

computing an instantaneous stiffness ratio waveform as a ratio of the first time derivative of the pressure signal to an instantaneous pressure metric; and

deriving an index of muscle function from the instantaneous stiffness ratio waveform.

2. A method according to claim 1, wherein the pressure signal comprises a cardiac chamber pressure signal.

3. A method according to claim 1, wherein the index of muscle function comprises a peak of the stiffness ratio waveform.

4. A method according to claim 1, wherein the pressure signal comprises an intramuscular pressure signal.

5. A method according to claim 1, wherein the muscular contraction event comprises at least part of one of a myocardial depolarization sequence and a myocardial repolarization event.

6. A method according to claim 1, wherein the pressure signal relates to development of fluid pressure using one of an intracardiac force transducer and a intracardiac pressure transducer.

7. A method according to claim 6, wherein the intracardiac pressures transducer is adapted to be disposed within a portion of a right ventricular chamber.

8. A method, comprising:

sensing a force signal during at least a portion of a muscular contraction, wherein said force signal relates at least in part to said muscular contraction;

computing an instantaneous stiffness ratio waveform as a ratio of the first time derivative of the force signal to an instantaneous force metric; and

deriving an index of muscle function from the stiffness ratio waveform.

9. A method, comprising:

sensing a pressure signal during at least a portion of a muscular relaxation event;

computing an instantaneous stiffness ratio waveform as the ratio of the first time derivative of the pressure signal to the instantaneous pressure; and

deriving an index of muscle function as a feature of the instantaneous stiffness ratio waveform.

10. a method according to claim 9, wherein the pressure signal comprises a cardiac chamber pressure signal.

11. A method according to claim 9, wherein the index of muscle function comprises a peak of the stiffness ratio waveform.

12. A method according to claim 9, wherein the pressure signal comprises an intramuscular pressure signal.

13. A method according to claim 9, wherein the muscular contraction event comprises at least part of one of a myocardial depolarization sequence and a myocardial repolarization event.

14. A method according to claim 9, wherein the pressure signal relates to development of fluid pressure using one of an intracardiac force transducer and a intracardiac pressure transducer.

15. A method according to claim 14, wherein the intracardiac pressure transducer is adapted to be disposed within a portion of a right ventricular chamber.

16. An apparatus, comprising:

means for sensing a pressure signal during at least a portion of a muscular relaxation event;

means for computing an instantaneous stiffness ratio waveform as the ratio of the first time derivative of the pressure signal to the instantaneous pressure; and

means for deriving an index of muscle function as a feature of the instantaneous stiffness ratio waveform.

17. An apparatus according to claim 16, further comprising an implantable medical device configured to contain or couple to the recited structural elements.

18. An apparatus according to claim 16, wherein the means for sensing the pressure signal comprises at least one fluid pressure transducer, and wherein the at least one fluid pressure transducer is adapted for deployment into fluid communication to a portion of the venous system of a subject.

19. An apparatus according to claim 16, wherein said fluid pressure transducer comprises one of an absolute pressure transducer and a gauge pressure transducer and wherein said fluid pressure transducer is disposed within a substantially hermetic enclosure.

20. A computer readable medium for storing a set of instructions which when implemented in a system cause the system to perform a method, said medium comprising:

instructions for sensing a pressure signal during at least a portion of a muscular relaxation event;

instructions for computing an instantaneous stiffness ratio waveform as the ratio of the first time derivative of the pressure signal to the instantaneous pressure; and

instructions for deriving an index of muscle function as a feature of the instantaneous stiffness ratio waveform.