CARDIAC FORCE SENSOR AND METHODS OF USE

• US 20080114256A1
• Filed: 11/14/2006
• Published: 05/15/2008
• Est. Priority Date: 11/14/2006
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Zhang, Yongxing, Wei, Xuan, Zhang, Yunlong
• Granted Patent: US 7,848,822 B2
• Time in Patent Office: Days
• US Class Current: 600/488
• CPC Class Codes: A61B 5/11 Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb for measuring pulse A61B5/02 ;A61B5/1038 takes precedence; motion detection to correct for motion artifacts in physiological signals A61B5/721
• CPC Class Codes: A61B 5/224 Measuring muscular strength
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia
• CPC Class Codes: A61B 5/6846 specially adapted to be brought in contact with an internal body part, i.e. invasive
• CPC Class Codes: A61B 5/686 Permanently implanted devices, e.g. pacemakers, other stimulators, biochips A61B5/6861 takes precedence
• CPC Class Codes: A61B 5/6869 Heart
• CPC Class Codes: A61N 1/3627 for treating a mechanical deficiency of the heart, e.g. congestive heart failure or cardiomyopathy

Abstract

A method and apparatus permit sensing one or more forces exerted by one or more portions of a heart. A force transducer and displacement sensor are disclosed. A movement of one or more portions of a heart can be translated into one or more signals indicative of force. These signals can be used to provide information such as to diagnose or treat one or more conditions.

Claims

1. An apparatus, comprising:

an implantable intravascular cardiac lead, including a proximal portion and a distal portion, the proximal portion adapted to be coupled to an electronics unit of an implantable medical device, the distal portion adapted to be located within a chamber of a heart;

a displacement sensor, adapted to sense a displacement of a portion of the heart during a heart movement, the displacement sensor providing an output displacement signal; and

a force transducer, associated with the displacement sensor, the force transducer adapted to convert the sensed displacement signal into a sensed force signal indicative of a force with which the at least one portion of the heart moves during the heart movement.

2. The apparatus of claim 1, comprising a fixation structure, associated with the distal portion of the lead and adapted to be secured to a portion of the heart, and wherein the fixation structure is associated with the displacement sensor.

3. The apparatus of claim 1, in which the force transducer includes a contractile structure that contracts in response to an applied force.

4. The apparatus of claim 3, in which the contractile structure includes a spring.

5. The apparatus of claim 3, in which the contractile structure includes a bellows.

6. The apparatus of claim 3, in which the contractile structure includes a specified force-displacement relationship, and further comprising an electronics unit of the implantable medical device, the electronics unit adapted to determine, in accordance to the relationship, the force with which the at least one portion of the heart moves.

7. The apparatus of claim 1, comprising an electronics unit adapted to determine, at least one of an acceleration, a velocity, and a displacement of the at least one portion of the heart.

8. The apparatus of claim 6, in which the electronics unit is adapted to determine the pressure of the at least one portion of the heart using the force.

9. The apparatus of claim 1, in which the lead includes at least one electrode adapted to sense an intrinsic electric heart signal or to deliver electric energy to the heart.

10. The apparatus of claim 1, wherein the electronics unit of the implantable medical device includes a controller adapted to initiate or adjust an delivered electrical energy or a delivered substance in response to the sensed force signal.

11. The apparatus of claim 1, comprising:

an electronics unit, adapted to use one or more sensed forces to determine at least one of;

a ventricular uptake;

a ventricular relaxation behavior;

an interventricular mechanical delay;

an interventricular dyssynchrony;

a ventricular output;

an electromechanical delay;

an evoked response;

a pacing voltage;

a pacing location;

a paradoxical movement; and

a respiratory signal.

12. A method comprising:

sensing one or more forces exerted by at least one portion of a heart by detecting a compression or expansion of an cardiac element;

obtaining an electrical signal responsive to the one or more forces by measuring a displacement of the compression or expansion; and

communicating the electrical signal to an electronics unit of an implantable medical device.

13. The method of claim 12, comprising determining a value of the one or more forces exerted by a portion of the heart by using a force-displacement relationship of the cardiac element and the displacement of the compression or expansion.

14. The method of claim 13, comprising determining at least one of an acceleration, a velocity, and a displacement of at least one portion of the heart using the sensed one or more forces exerted by a portion of the heart.

15. The method of claim 13, comprising determining a pressure exerted on a lead by at least one portion of the heart using the sensed one or more forces exerted by the at least one portion of the heart.

16. The method of claim 12, comprising:

initiating or adjusting delivery of an energy or substance to the heart in response to sensed one or more forces exerted by the at least one portion of the heart.

17. The method of claim 12, comprising determining a ventricular uptake or ventricular relaxation behavior using the sensed one or more forces exerted by the at least one portion of the heart.

18. The method of claim 12, comprising determining at least one of an interventricular mechanical delay and an interventricular dyssynchrony using the sensed one or more forces exerted by the at least one portion of the heart.

19. The method of claim 12, comprising determining a left ventricular output using the sensed one or more forces exerted by the at least one portion of the heart, and wherein the sensing one or more forces exerted by the at least one portion of the heart includes sensing at a right ventricular septum and sensing at a left ventricular free lateral wall.

20. The method of claim 12, comprising sensing one or more electrogram signals and determining an electromechanical delay using the sensed one or more forces exerted by the at least one portion of the heart and using the sensed one or more electrogram signals.

21. The method of claim 12, comprising determining at least one of a pacing voltage and a pacing location using the sensed one or more forces exerted by the at least one portion of the heart.

22. The method of claim 21, comprising determining the at least one of the pacing voltage and the pacing location also using an evoked response.

23. The method of claim 12, comprising determining a paradoxical movement using the sensed one or more forces exerted by the at least one portion of the heart.

24. The method of claim 12, comprising determining at least one respiratory signal using the sensed one or more forces exerted by the at least one portion of the heart.

25. The method of claim 24, wherein the determining at least one respiratory signal includes lowpass filtering the electrical signal.

26. The method of claim 24, wherein the determining at least one respiratory signal includes using an amplitude of the sensed one or more forces.

27. The method of claim 12, comprising:

storing an indication of the electrical signal over more than one cardiac cycle; and

detecting a change in the indication of the electrical signal over a time period that spans more than one cardiac cycles.

28. The method of claim 12, comprising determining at least one of a minimum value, a maximum value, a minimum time rate of change, and a maximum time rate of change of the sensed one or more forces.

29. The method of claim 12, comprising determining a time rate of change in pressure using the sensed one or more forces.

30. The method of claim 12, comprising determining an indication of bradyarrhythmia at least in part by using the sensed one or more forces.

31. The method of claim 30, wherein the determining the indication of bradyarrhythmia comprises:

sensing an electrogram signal; and

deeming a bradyarrhythmia condition to exist when both the electrogram signal and the sensed one or more forces indicate an absence of a contraction over a specified time period.

32. The method of claim 12, comprising determining an undersensing condition, the determining the undersensing condition comprising:

sensing an electrogram signal to detect electrical cardiac conduction;

when the sensed one or more forces indicates at least one conduction that is absent from the sensed electrogram signal, then declaring the undersensing condition to exist.

33. The method of claim 12, comprising determining an indication of a tachyarrhythmia using the sensed one or more forces.

34. The method of claim 12, comprising determining an oversensing condition, the determining the oversensing condition comprising:

sensing an electrogram signal to detect electrical cardiac conduction;

when the sensed one or more forces indicate an absence of a mechanically-indicated contraction corresponding to at least one electrically-indicated contraction, then declaring the oversensing condition to exist.

35. The method of claim 12, comprising determining a hemodynamic status during arrhythmia using the sensed one or more forces.

36. The method of claim 35, comprising initiating or adjusting at least one of an electrical energy delivery and a substance delivery using the hemodynamic status.

37. The method of claim 12, comprising initiating or adjusting delivery of at least one of a shock and an antitachyarrhythmia pacing using the sensed one or more forces.