Pressure-modulated energy level for pacing pulses

• US 20030199933A1
• Filed: 04/22/2002
• Published: 10/23/2003
• Est. Priority Date: 04/22/2002
• Status: Active Grant

• Current Assignee: Chester L. Struble
• Original Assignee: Chester L. Struble
• Inventors: Struble, Chester L.
• Granted Patent: US 7,386,346 B2
• Time in Patent Office: Days
• US Class Current: 607/17
• CPC Class Codes: A61N 1/36564 controlled by blood pressure

Abstract

Techniques for pacing the heart of a patient as a function of a pressure value make use of a pressure monitor that receives a signal from a pressure sensor in the heart. The pressure monitor measures a pressure value. The pressure monitor may, for example, estimate the pulmonary artery diastolic pressure if the pressure sensor is located in the right ventricle, or calculate the mean central venous pressure if pressure sensor is located in the right atrium. The energy level of the pacing pulses delivered to the patient'"'"'s heart by a pacemaker is modulated as a function of the pressure value. Modulating the energy level of the pacing pulses modulates the cardiac output of the patient'"'"'s heart.

Claims

1. An implantable medical device comprising:

a pressure sensor that generates a pressure signal as a function of a pressure in a heart;

a pressure monitor that identifies a pressure value at a point of maximum slope in the pressure signal; and

a processor that causes a pacemaker to adjust the energy level of pacing pulses delivered to the heart as a function of the pressure value.

2. The device of claim 1, wherein the processor is further configured to generate a control signal as a function of the pressure value,

wherein the pacemaker is configured to receive the control signal and adjust the energy level of pacing pulses delivered to the heart as a function of the control signal.

3. The device of claim 1, wherein the amplitude of the pacing pulse delivered by the pacemaker is a function of the pressure value.

4. The device of claim 3, wherein the pulse amplitude is within a range from approximately 0.5 volts to approximately 5.0 volts.

5. The device of claim 1, wherein the pulse width of the pacing pulse delivered by the pacemaker is a function of the pressure value.

6. The device of claim 5, wherein the pulse width is within a range from approximately 0.05 ms to approximately 1.5 ms.

7. The device of claim 1, wherein the pressure sensor includes one of a capacitive absolute pressure sensor, a piezoelectric crystal transducer and a piezoresistive pressure transducer.

8. The device of claim 1, wherein the pressure monitor comprises a differentiating circuit, the differentiating circuit configured to generate a differential signal that is representative of the first derivative of the pressure signal,

wherein the pressure monitor identifies the pressure value corresponding to a maximum point on the differential signal.

9. The device of claim 1, wherein the pressure monitor comprises a differentiating circuit, the differentiating circuit configured to generate a differential signal that is representative of the second derivative of the pressure signal,

wherein the pressure monitor identifies the pressure value corresponding to a zero crossing point on the differential signal.

10. The device of claim 1, further comprising an input/output device coupled to the processor, the input/output device configured to exchange information between a person and the processor.

11. The device of claim 1, wherein the device is implanted in the upper chest of a patient.

12. An implantable medical device comprising:

a pressure sensor that generates a pressure signal as a function of a pressure in a heart;

a pressure monitor that estimates the pulmonary artery diastolic pressure as a function of the pressure signal; and

a processor that causes a pacemaker to adjust the energy level of pacing pulses delivered to the heart as a function of the estimated pulmonary artery diastolic pressure.

13. The device of claim 12, wherein the processor is further configured to generate a control signal as a function of the estimated pulmonary artery diastolic pressure,

wherein the pacemaker is configured to receive the control signal and adjust the energy level of pacing pulses delivered to the heart as a function of the control signal.

14. The device of claim 12, wherein the amplitude of the pacing pulse delivered by the pacemaker is a function of the estimated pulmonary artery diastolic pressure.

15. The device of claim 14, wherein the pulse amplitude is within a range from approximately 0.5 volts to approximately 5.0 volts.

16. The device of claim 12, wherein the pulse width of the pacing pulse delivered by the pacemaker is a function of the estimated pulmonary artery diastolic pressure.

17. The device of claim 16, wherein the pulse width is within a range from approximately 0.05 ms to approximately 1.5 ms.

18. The device of claim 12, wherein the pressure sensor is disposed in the right ventricle of the heart.

19. The device of claim 18, wherein the pressure monitor comprises a differentiating circuit, the differentiating circuit configured to generate a differential signal that is representative of the first derivative of the pressure signal,

wherein the pressure monitor estimates pulmonary artery diastolic pressure as a function of the differential signal.

20. The device of claim 18, wherein the pressure monitor comprises a differentiating circuit, the differentiating circuit configured to generate a differential signal that is representative of the second derivative of the pressure signal,

wherein the pressure monitor estimates pulmonary artery diastolic pressure as a function of the differential signal.

21. The device of claim 12, further comprising an input/output device coupled to the processor, the input/output device configured to exchange information between a person and the processor.

22. The device of claim 12, wherein the device is implanted in the upper chest of a patient.

23. An implantable medical device comprising:

a pressure sensor that generates a pressure signal as a function of a pressure in an atrium of a heart;

a pressure monitor to measure a pressure value as a function of the pressure signal; and

a processor that causes a pacemaker to adjust the energy level of pacing pulses delivered to the heart as a function of the pressure value.

24. The device of claim 23, wherein the processor is further configured to generate a control signal as a function of the pressure value,

wherein the pacemaker is configured to receive the control signal and adjust the energy level of pacing pulses delivered to the heart as a function of the control signal.

25. The device of claim 23, wherein the amplitude of the pacing pulse delivered by the pacemaker is a function of the pressure value.

26. The device of claim 25, wherein the pulse amplitude is within a range from approximately 0.5 volts to approximately 5.0 volts.

27. The device of claim 23, wherein the pulse width of the pacing pulse delivered by the pacemaker is a function of the pressure value.

28. The device of claim 27, wherein the pulse width is within a range from approximately 0.05 ms to approximately 1.5 ms.

29. The device of claim 23, wherein the pressure sensor includes one of a capacitive absolute pressure sensor a piezoelectric crystal transducer and a piezoresistive pressure transducer.

30. The device of claim 23, wherein the pressure value measured by the pressure monitor is the mean central venous pressure.

31. The device of claim 30, wherein the pressure sensor is disposed in the right atrium.

32. The device of claim 23, further comprising an input/output device coupled to the processor, the input/output device configured to exchange information between a person and the processor.

33. The device of claim 23, wherein the device is implanted in the upper chest of a patient.

34. A method comprising:

identifying a point of maximum slope in a pressure signal, the pressure signal being a function of a pressure in a heart;

identifying a value of the pressure signal at the maximum slope of the pressure signal; and

adjusting the energy level of pacing pulses delivered to the heart by a pacemaker as a function of the identified pressure value.

35. The method of claim 34, wherein adjusting the energy level of pacing pulses comprises adjusting the pulse amplitude of pacing pulses.

36. The method of claim 34, wherein adjusting the energy level of pacing pulses comprises adjusting the pulse width of pacing pulses.

37. The method of claim 34, wherein identifying the point of maximum slope in the pressure signal comprises:

generating the first derivative of the pressure signal during a cardiac cycle; and

sensing the point on the pressure signal at which the first derivative of the pressure signal is maximized.

38. The method of claim 34, wherein identifying a point of maximum slope in the pressure signal comprises:

sensing an R-wave of a cardiac cycle;

generating the second derivative of the pressure signal during the cardiac cycle; and

sensing the point on the pressure signal at which the second derivative of the pressure signal becomes negative after the R-wave.

39. The method of claim 34, wherein adjusting the energy level of pacing pulses delivered to the heart by a pacemaker as a function of the pressure value comprises:

storing a range of pressure values and one or more pacing pulse energy parameter values corresponding to each pressure value in the range;

selecting the pacing pulse energy parameter values that correspond to the identified pressure value; and

delivering pacing pulses to the heart, wherein the energy level of the delivered pacing pulses is a function of the selected pacing pulse energy parameter values.

40. The method of claim 39, further comprising:

receiving a range of pressure values; and

receiving one or more corresponding pacing pulse energy parameter values for each pressure value in the range.

41. The method of claim 40, further comprising storing the received range of pressure values and the corresponding pacing pulse energy parameter values in memory.

42. The method of claim 39, wherein the pressure values correspond to the pacing pulse energy parameter values according to an equation that defines a curve.

43. A method comprising:

estimating the pulmonary artery diastolic pressure as a function of a pressure within a heart; and

adjusting the energy level of pacing pulses delivered to the heart by a pacemaker as a function of the estimated pulmonary artery diastolic pressure.

44. The method of claim 43, wherein adjusting the energy level of pacing pulses comprises adjusting the pulse amplitude of pacing pulses.

45. The method of claim 43, wherein adjusting the energy level of pacing pulses comprises adjusting the pulse width of pacing pulses.

46. The method of claim 43, wherein estimating the pulmonary artery diastolic pressure as a function of the pressure in a heart comprises estimating the pulmonary artery diastolic pressure as a function of the pressure in the right ventricle.

47. The method of claim 43, wherein adjusting the energy level of pacing pulses delivered to the heart by a pacemaker as a function of the estimated pulmonary artery diastolic pressure comprises:

storing a range of pulmonary artery diastolic pressure values and one or more pacing pulse energy parameter values corresponding to each pulmonary artery diastolic pressure value in the range;

selecting the pacing pulse energy parameter values that correspond to the estimated pulmonary artery diastolic pressure value; and

delivering pacing pulses to the heart, wherein the energy level of the delivered pacing pulses is a function of the selected pacing pulse energy parameter values.

48. The method of claim 47, further comprising:

receiving a range of pulmonary artery diastolic pressure values; and

receiving one or more corresponding pacing pulse energy parameter values for each pulmonary artery diastolic pressure value in the range.

49. The method of claim 48, further comprising storing the received range of pulmonary artery diastolic pressure values and the corresponding pacing pulse energy parameter values in memory.

50. The method of claim 47, wherein the pulmonary artery diastolic pressure values correspond to the pacing pulse energy parameter values according to an equation that defines a curve.

51. A method comprising:

determining a mean value of a pressure signal over a period of time, the pressure signal being a function of a pressure within a heart; and

adjusting the energy level of pacing pulses delivered to the heart by a pacemaker as a function of the mean value.

52. The method of claim 51, wherein adjusting the energy level of pacing pulses comprises adjusting the pulse amplitude of pacing pulses.

53. The method of claim 51, wherein adjusting the energy level of pacing pulses comprises adjusting the pulse width of pacing pulses.

54. The method of claim 51, wherein determining a mean value of the pressure signal over a period of time comprises:

determining the length of a cardiac cycle;

sampling the pressure signal over the length of the cardiac cycle; and

calculating the mean of the pressure signal over the length of the cardiac cycle.

55. The method of claim 51, wherein determining a mean value of a pressure signal over a period of time, the pressure signal being a function of the pressure within a heart, comprises determining a mean value of a pressure signal over a period of time, the pressure signal being a function of the pressure within the right atrium of a heart,

wherein the determined mean value is the mean central venous pressure.

56. The method of claim 51, wherein adjusting the energy level of pacing pulses delivered to the heart by a pacemaker as a function of the mean pressure value comprises:

storing a range of mean pressure values and one or more pacing pulse energy parameter values corresponding to each mean pressure value in the range;

selecting the pacing pulse energy parameter values that correspond to the determined mean pressure value; and

delivering pacing pulses to the heart, wherein the energy level of the delivered pacing pulses is a function of the selected pacing pulse energy parameter values.

57. The method of claim 56, further comprising:

receiving a range of mean pressure values; and

receiving one or more corresponding pacing pulse energy parameter values for each mean pressure value in the range.

58. The method of claim 57, further comprising storing the received range of mean pressure values and the corresponding pacing pulse energy parameter values in memory.

59. The method of claim 56, wherein the mean pressure values correspond to the pacing pulse energy parameter values according to an equation that defines a curve.

60. A computer-readable medium comprising instructions that cause a processor to:

identify a point of maximum slope in a pressure signal, the pressure signal being a function of a pressure within a heart;

identify a value of the pressure signal at the maximum slope of the pressure signal; and

adjust the energy level of pacing pulses delivered to the heart by a pacemaker as a function of the identified pressure value.

61. The computer-readable medium of claim 60, wherein the instructions that cause a processor to identify a point of maximum slope in a pressure signal further comprise instructions that cause a processor to:

generate the first derivative of the pressure signal during a cardiac cycle; and

sense the point on the pressure signal at which the first derivative of the pressure signal is maximized.

62. The computer-readable medium of claim 60, wherein the instructions that cause a processor to identify a point of maximum slope in a pressure signal further comprise instructions that cause a processor to:

sense an R-wave of a cardiac cycle;

generate the second derivative of the pressure signal during the cardiac cycle; and

sense the point on the pressure signal at which the second derivative of the pressure signal becomes negative after the R-wave.

63. The computer-readable medium of claim 60, wherein the instructions that cause a processor to adjust the energy level of pacing pulses delivered to the heart by a pacemaker as a function of the identified pressure value further comprise instructions that cause a processor to:

store a range of pressure values and one or more pacing pulse energy parameter values corresponding to each pressure value in the range;

select the pacing pulse energy parameter values that correspond to the identified pressure value; and

direct the pacemaker to adjust the energy level of pacing pulses delivered to the heart, wherein the energy level of the pacing pulses is a function of the selected pacing pulse energy parameter values.

64. A computer-readable medium comprising instructions that cause a processor to:

receive an estimated pulmonary artery diastolic pressure value; and

adjust the energy level of pacing pulses delivered to the heart by a pacemaker as a function of the estimated pulmonary artery diastolic pressure value.

65. The computer-readable medium of claim 64, wherein the instructions that cause a processor to adjust the energy level of pacing pulses delivered to the heart by a pacemaker as a function of the estimated pulmonary artery diastolic pressure value further comprise instructions that cause a processor to:

store a range of pulmonary artery diastolic pressure values and one or more pacing pulse energy parameter values corresponding to each pulmonary artery diastolic pressure value in the range;

select the pacing pulse energy parameter values that correspond to the estimated pulmonary artery diastolic pressure value; and

direct the pacemaker to adjust the energy level of pacing pulses delivered to the heart, wherein the energy level of the pacing pulses is a function of the selected pacing pulse energy parameter values.

66. A computer-readable medium comprising instructions that cause a processor to:

determine a mean value of the pressure signal over a period of time, the pressure signal being a function of a pressure within a heart; and

adjust the energy level of pacing pulses delivered to the heart by a pacemaker as a function of the mean pressure value.

67. The computer-readable medium of claim 66, wherein the instructions that cause a processor to determine a mean value of the pressure signal over a period of time, further comprise instructions that cause a processor to:

determine the length of a cardiac cycle;

sample the pressure signal over the length of the cardiac cycle; and

calculate the mean of the pressure signal over the length of the cardiac cycle.

68. The computer-readable medium of claim 66, wherein the instructions that cause a processor to adjust the energy level of pacing pulses delivered to the heart by a pacemaker as a function of the mean pressure value, further comprise instructions that cause a processor to:

store a range of mean pressure values and one or more pacing pulse energy parameter values corresponding to each mean pressure value in the range;

select the pacing pulse energy parameter values that correspond to the determined mean pressure value; and

direct the pacemaker to adjust the energy level of pacing pulses delivered to the heart, wherein the energy level of the pacing pulses is a function of the selected pacing pulse energy parameter values.

69. An implantable medical device comprising:

means for identifying a point of maximum slope in a pressure signal, the pressure signal being a function of a pressure within a heart;

means for identifying a value of the pressure signal at the maximum slope of the pressure signal;

means for adjusting the energy level of pacing pulses delivered to the heart as a function of the identified pressure value.

70. An implantable medical device comprising:

means for estimating the pulmonary artery diastolic pressure as a function of a pressure within a heart; and

means for adjusting the energy level of pacing pulses delivered to the heart as a function of the estimated pulmonary artery diastolic pressure value.

71. An implantable medical device comprising:

means for determining a mean value of a pressure signal over a period of time, the pressure signal a function of a pressure within a heart; and

means for adjusting the energy level of pacing pulses delivered to the heart as a function of the determined mean pressure value.