Implantable system for monitoring the condition of the heart

• US 20050113705A1
• Filed: 09/28/2004
• Published: 05/26/2005
• Est. Priority Date: 11/26/2003
• Status: Active Grant

• Current Assignee: Angel Medical Systems, Inc.
• Original Assignee: Angel Medical Systems, Inc.
• Inventors: Fischell, David R., Fischell, Robert E., Johnson, Steven R., Harwood, Jonathan
• Granted Patent: US 7,512,438 B2
• Time in Patent Office: Days
• US Class Current: 600/515
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/355 Detecting T-waves
• CPC Class Codes: A61B 5/358 Detecting ST segments
• CPC Class Codes: A61B 5/366 Detecting abnormal QRS complex, e.g. widening
• CPC Class Codes: A61B 5/413 Monitoring transplanted tissue or organ, e.g. for possible rejection reactions after a transplant
• CPC Class Codes: A61N 1/025 Digital circuitry features of electrotherapy devices, e.g. memory, clocks, processors
• CPC Class Codes: A61N 1/37235 Aspects of the external programmer
• CPC Class Codes: A61N 1/37247 User interfaces, e.g. input or presentation means

Abstract

Disclosed is a “tracker system” that includes implanted electrical leads which are part of an implanted cardiotracker plus external equipment that includes external alarm means and a physician'"'"'s programmer. The tracker system is designed to monitor the degradation of a patient'"'"'s cardiovascular condition from one or more causes. These causes include the rejection of a transplanted heart and/or the progression of a stenosis in a coronary artery. As one or more stenoses in a coronary artery become progressively more narrow thereby causing reduced blood flow to the heart muscle coronary circulation, the tracker system can alert the patient by either or both internal and/or external alarm means to take the appropriate medical action. The physician'"'"'s programmer can be used to display histograms of key heart signal parameters that are indicative of the patient'"'"'s cardiovascular condition.

Claims

1. An implantable cardiotracker for tracking the cardiovascular condition of a human patient, the cardiotracker including:

at least two implanted electrodes that are positioned within the human patient to sense the electrical signal from the patient'"'"'s heart, the electrical signal being an electrogram which consists of a multiplicity of beats;

a processor to compute the value of at least one heart signal parameter for every beat of at least a portion of the multiplicity of beats of the electrogram; and

digital memory designed to store the computed values of the at least one heart signal parameter during a preset time period which is the data collection time period.

2. The implanted cardiotracker of claim 1 where the at least one heart signal parameter that is stored in memory is the value of the ST segment voltage.

3. The implanted cardiotracker of claim 1 where the at least one heart signal parameter that is stored in memory is the value of the ST segment voltage minus the PQ segment voltage which is the ST deviation.

4. The implanted cardiotracker of claim 1 where the at least one heart signal parameter that is stored in memory is the value of the ST shift which is defined as the ST deviation for a specific beat in a recent time period minus a baseline ST deviation recorded at some prior time.

5. The implanted cardiotracker of claim 1 where the at least one heart signal parameter that is stored in memory is the value of the QRS voltage.

6. The implanted cardiotracker of claim 5 where the QRS voltage is the maximum peak-to-peak QRS complex voltage for a specific beat.

7. The implanted cardiotracker of claim 1 where the at least one heart signal parameter that is stored in memory is the QRS shift which is the difference between the average QRS voltage in a recent data collection time period minus a baseline QRS voltage taken at some prior data collection time period, the baseline QRS voltage being the average QRS voltage during the prior data collection time period.

8. The implanted cardiotracker of claim 7 where the prior data collection time period when the baseline QRS voltage was measured is at a time when a heart transplant patient was not rejecting the heart that was surgically placed into his body.

9. The implanted cardiotracker of claim 1 where the at least one heart signal parameter that is stored in memory is the value of the R—

R interval.

10. The implanted cardiotracker of claim 1 where the at least one heart signal parameter that is stored in memory is the QRS complex width.

11. The implanted cardiotracker of claim 10 further including a counter which stores the number of times that the width of the QRS complex exceeded a preset value during the data collection time period.

12. The implanted cardiotracker of claim 11 where the preset value of the width of the QRS complex is at least 150 milliseconds.

13. The implanted cardiotracker of claim 1 where the number of the premature atrial contractions (PACs) that have occurred in the electrogram within the data collection time period is stored in memory.

14. The implanted cardiotracker of claim 1 where the number of the premature ventricular contractions (PVCs) that have occurred in the electrogram within the data collection time period is stored in memory.

15. The implanted cardiotracker of claim 1 where the at least one heart signal parameter that is stored in memory is the peak value of the T wave voltage.

16. The implanted cardiotracker of claim 1 where the number of T wave alternans occurring in the electrogram within the data collection time period is stored in memory.

17. The implanted cardiotracker of claim 1 where the data collection time period is approximately one day.

18. The implanted cardiotracker of claim 1 where the data collection time period is less than one day.

19. The implanted cardiotracker of claim 1 where the data collection time period is selected from the group consisting of one segment of the electrogram, approximately one minute, approximately one hour, approximately one day, approximately two days, approximately one week, approximately one month and approximately one year.

20. The implanted cardiotracker of claim 1 where the processor also computes and places into the digital memory the average of the stored values of the at least one heart signal parameter for the data collection time period.

21. The implanted cardiotracker of claim 20 where the average value is the mean value.

22. The implanted cardiotracker of claim 20 where the average value is the median value.

23. The implanted cardiotracker of claim 20 where the at least one heart signal parameter is stored in memory for at least two data collection time periods.

24. The implanted cardiotracker of claim 23 where one of the at least two data collection time periods is designated as a baseline time period and the average value of the heart signal parameter for the baseline time period is the average baseline value of that heart signal parameter during that baseline time period.

25. The implanted cardiotracker of claim 24 further including an alarm signal generator designed to generate an internal alarm signal when the average value of a heart signal parameter for a recent data collection time period exceeds the average baseline value of that heart signal parameter by an amount that is greater than a preset threshold value.

26. The implanted cardiotracker of claim 25 where the cardiotracker has the capability to generate at least two different types of internal alarm signals.

27. The implanted cardiotracker of claim 25 where the internal alarm signal that is generated by the cardiotracker is a SEE DOCTOR ALERT that indicates to the human patient that he or she should seek medical attention on a non-emergency basis.

28. The implanted cardiotracker of claim 25 where the internal alarm signal that is generated by the cardiotracker is an EMERGENCY ALARM that indicates to the human patient that he or she should seek immediate medical attention.

30. The implanted cardiotracker of claim 1 further including external equipment designed to provide two-way wireless communication with the implanted cardiotracker.

31. The implanted cardiotracker of claim 30 where the external equipment includes an external alarm system that is designed to provide an alarm signal that is an external alarm signal.

32. The implanted cardiotracker of claim 31 where the external alarm system includes means to manually turn off the external alarm signal.

33. The implanted cardiotracker of claim 31 where the external alarm system includes means to manually turn off the internal alarm signal generated by the cardiotracker.

34. The implanted cardiotracker of claim 31 where the external alarm system includes means to manually turn off both the internal alarm signal generated by the cardiotracker and the external alarm signal generated by the external alarm system.

35. The implanted cardiotracker of claim 1 further including external equipment having the capability to display data stored within the digital memory of the implanted cardiotracker.

36. The implanted cardiotracker of claim 35 where the external equipment includes a physician'"'"'s programmer designed to program specific operating parameters of the implanted cardiotracker.

37. The implanted cardiotracker of claim 35 where the data displayed includes the values of the at least one heart signal parameter stored during at least one data collection time period.

38. The implanted cardiotracker of claim 35 where the data displayed is extracted data including the average value of the at least one heart signal parameter computed for at least one data collection time period.

39. The implanted cardiotracker of claim 38 where the external equipment has the capability to display the average values of the at least one heart signal parameter over an extracted data retention time period.

40. The implanted cardiotracker of claim 39 where extracted data retention time period is at least one month.

41. The implanted cardiotracker of claim 39 where extracted data retention time period is at least six months.

42. The implanted cardiotracker of claim 38 where the extracted data is selected from the group consisting of the average ST segment voltage, the average ST deviation, the average ST shift, the average QRS voltage and the average QRS shift.

43. The implanted cardiotracker of claim 1 where the digital memory includes sufficient capacity to retain the values of the at least one heart signal for a multiplicity of data collection time periods, the multiplicity of data collection time periods being a collected data retention time period.

44. The implanted cardiotracker of claim 43 where the collected data retention time period is at least one week.

45. The implanted cardiotracker of claim 1 where the computed values of the at least one heart signal parameter are stored in the digital memory in a histogram format.

46. The implanted cardiotracker of claim 45 where the computed values of the at least one heart signal parameter are stored in at least one histogram, the at least one histogram having a multiplicity of bins, each bin corresponding to a different range of the at least one heart signal parameter.

47. The implanted cardiotracker of claim 46 where the processor computes the values of two heart signal parameters which are a first heart signal parameter and a second heart signal parameter.

48. The implanted cardiosaver of claim 47 further including a set of histograms where each histogram in the set corresponds to a different range of the first heart signal parameter and the bins in each histogram correspond to a range of the second heart signal parameter.

49. The implanted cardiotracker of claim 45 where the processor computes and places into the digital memory the average value of the at least one heart signal parameter stored in the histogram format for the entire data collection time period.

50. The implanted cardiotracker of claim 49 where the average value of the at least one heart signal parameter is extracted histogram data which is retained in the digital memory for the extracted data retention time period.

29. The implanted cardiotracker of 25 where the internal alarm signal is selected from the group consisting of a vibratory alarm signal, an electrical stimulation alarm signal or an audio alarm signal.

51. A method for early detection of rejection of a transplanted human heart in a human patient, the method comprising the steps of:

a. implanting into the human patient a cardiotracker designed to calculate and retain in memory the average value of at least one heart signal parameter of the patient'"'"'s electrogram for each of a multiplicity of data collection time periods;

b. transferring the average values of the at least one heart signal parameter in each data collection time period to a physician'"'"'s programmer and creating a display on the physician'"'"'s programmer that shows a time history of the average values of the at least one heart signal parameter for the multiplicity of data collection time periods; and

c. adjusting the administration of anti-rejection medications to reverse transplant rejection if the time history of the average values of the at least one heart signal parameter indicates the presence of transplant rejection.

52. A method for early detection of rejection of a transplanted human heart, the method comprising the steps of:

a. implanting a cardiotracker designed to calculate and retain in memory the average QRS voltage for each of a multiplicity of data collection time periods;

b. transferring the average QRS voltage for each data collection time period to a physician'"'"'s programmer and creating a display on the physician'"'"'s programmer that shows a time history of the average QRS voltage over the multiplicity of data collection time periods; and

c. adjusting the administration of anti-rejection medications to reverse transplant rejection if the time history of average QRS voltage indicates the presence of transplant rejection.

53. A method for monitoring the progression of atherosclerosis in a coronary artery or bypass graft of a human subject, the method comprising the steps of:

a. implanting a cardiotracker designed to calculate and retain in memory the average value of at least one ST segment related heart signal parameter for each of a multiplicity of data collection time periods, the ST segment related heart signal parameter being any one of the ST segment voltage, the ST deviation or the ST shift; and

b. transferring the average values of the at least one ST segment related heart signal parameter to a physician'"'"'s programmer designed to display a time history of the average values of the at least one ST segment related heart signal parameter over the multiplicity of data collection time intervals.

54. A method for detecting a significant change in the cardiovascular condition of a human subject, the method comprising the steps of:

a. implanting into the human subject a cardiotracker designed to calculate and retain in memory the average value of at least one heart signal parameter for each of a multiplicity of data collection time periods, the cardiotracker having an alarm means;

b. following each calculation of the average value of at least one heart signal parameter, having the cardiotracker decide if the average value just calculated is indicative of a significant change in the human subject'"'"'s cardiovascular condition; and

c. alerting the patient via the cardiotracker'"'"'s alarm means that a significant change in cardiovascular condition has been detected.

55. A system for tracking the cardiovascular condition of a human patient the system including:

at least two implanted electrodes that are positioned within the human patient to sense the electrical signal from the patient'"'"'s heart, the electrical signal being an electrogram which consists of a multiplicity of beats;

a histogram memory including memory capacity for at least one histogram, the histogram including at least two bins, each bin being a counter; and

a processor to compute the value of at least one heart signal parameter for at least a portion of the multiplicity of beats of the electrogram data, each beat of the portion of the multiplicity of beats that is processed being a processed beat, the processor also being designed to increment one of the at least two bins of the at least one histogram where the choice of bin to be incremented is dependent on the value of the at least one heart signal parameter whose value is computed by the processor.

56. The system of claim 55 where the histogram memory includes at least two sections, each section including at least one histogram.

57. The system of claim 56 where one of the at least two sections is the current section, the current section having at least one histogram that is incremented for a defined period of time which is a data collection time period.

58. The system of claim 56 where at least one of the at least two sections was the current section during a prior data collection time period.

59. The system of claim 56 where the histogram memory has at least seven sections.

60. The system of claim 55 where the histogram memory includes at least two histograms each histogram including at least two bins and the processor computes the values of at least two heart signal parameters which are a first heart signal parameter and a second heart signal parameter, the processor also being designed to select one of the at least two histograms based on the value of the first heart signal parameter, that histogram being the selected histogram the choice of bin to be incremented within the selected histogram being dependent on the value of the second heart signal parameter.

61. The system of claim 60 where the first heart signal parameter is R—

R interval and the second heart signal parameter is ST deviation.

62. The system of claim 60 where the first heart signal parameter is heart rate and the second heart signal parameter is ST deviation.

63. The system of claim 55 where the electrodes are implanted under the skin of the human patient.

64. The system of claim 63 where one of the electrodes is placed under the skin of the human patient in the vicinity of the upper chest.

65. The system of claim 55 where the electrodes are placed within the heart of the human patient.

66. The system of claim 65 where at least one of the electrodes is placed within the right ventricle of the patient'"'"'s heart.

67. The system of claim 55 where at least one of the heart signal parameter is the average amplitude of a sub-segment of each processed beat of the electrogram data.

68. The system of claim 67 where the sub-segment is the ST segment.

69. The system of claim 55 where at least one of the heart signal parameters is the ST deviation.

70. The system of claim 55 where at least one of the heart signal parameters is the QRS voltage.

71. The system of claim 70 where the QRS voltage is the peak-to-peak voltage of the QRS complex.

72. The system of claim 55 where at least one of the heart signal parameters is the width of at least one sub-segment of the processed beats of the electrogram data.

73. The system of claim 72 where the sub-segment is the QRS complex.

74. The system of claim 55 where at least one of the heart signal parameters is the R—

R interval of the processed beats of the electrogram data.

75. The system of claim 55 where at least one of the heart signal parameters is the R—

R interval variability of the processed beats of the electrogram data.

76. The system of claim 55 where the processed beats comprise less than half of all beats during any data collection time period.

77. The system of claim 55 where the processed beats comprise less than 10% of all beats during any data collection time period.

78. The system of claim 55 where each histogram is incremented by the processor for a preset data collection time period.

79. The system of claim 78 where the data collection time period is approximately one day.

80. The system of claim 78 where the data stored in each histogram is retained in memory for a data retention time period which follows the data collection time period during which data collection time period the bins of the histogram are incremented.

81. The system of claim 80 where the data retention time period is at least one week.

82. The system of claim 55 further including an extracted histogram data memory containing extracted histogram data resulting from computations periodically performed by the processor on the values stored in the at least one histogram.

83. The system of claim 82 where the extracted histogram data includes the median value of at least one of the heart signal parameters stored in the at least one histogram.

84. The system of claim 82 where the extracted histogram data includes the mean value of the values of the at least one heart signal parameter stored in the at least one histogram.

85. The system of claim 82 where the system further includes the means to compute a moving average of two or more values of extracted histogram data.

86. The system of claim 55 where the system further includes means to compare the extracted histogram data with a preset threshold.

87. The system of claim 86 where the system further includes alarm means to alert the patient when the preset threshold is exceeded.

88. The system of claim 82 where the extracted histogram data is retained in the extracted histogram data memory for a preset extracted data retention time period.

89. The system of claim 88 where the extracted data retention time period is greater than 30 days.

90. The system of claim 88 where the extracted data retention time period is at least six months.

91. A system for diagnosing the cardiovascular condition of a human patient the system including:

at least two implanted electrodes that are positioned within of the human patient to sense the electrical signal from the patient'"'"'s heart, the electrical signal being an electrogram which consists of a multiplicity of beats;

a processor designed to process the electrical signal sensed by the at least two electrodes, the processing being designed to periodically calculate the values of at least one heart signal parameter, the processor further being designed to identify a change in the at least one heart signal parameter that is indicative of a cardiac event; and

digital memory designed to store the values of the at least one heart signal parameter during a pre-specified time period which is a data collection time period.

92. The system of claim 91 where the cardiac event is an acute myocardial infarction.

93. The system of claim 91 where the cardiac event is coronary ischemia.

94. The system of claim 91 where the cardiac event is an arrhythmia.

95. The system of claim 94 where the arrhythmia is tachycardia.

96. The system of claim 94 where the arrhythmia is atrial fibrillation.

97. The system of claim 94 where the arrhythmia is premature ventricular contractions (PVCs).

98. The system of claim 91 where the cardiac event is rejection of a transplanted heart.

99. The system of claim 91 where the data collection time interval is approximately one day.

100. The system of claim 91 where the values of the at least one heart signal parameter are retained in the digital memory for a preset time period which is a data retention time period.

101. An implantable cardiac pacemaker for a human patient, the pacemaker including:

a pacemaker lead implanted into the heart of the human patient, the pacemaker lead being designed to sense the electrical signal from the patient'"'"'s heart, the electrical signal being an electrogram which consists of a multiplicity of beats;

pacemaker circuitry connected to the pacemaker lead, the pacemaker circuitry designed to pace the heart of a human patient,

a processor to compute the value of at least one heart signal parameter for each of the multiplicity of beats of the electrogram; and

digital memory designed to store the computed values of the at least one heart signal parameter during a pre-specified time period which is a data collection time period.

102. An implantable defibrillator for a human patient, the defibrillator including:

a lead implanted into the heart of the human patient, the lead being designed to sense the electrical signal from the patient'"'"'s heart, the electrical signal being an electrogram which consists of a multiplicity of beats;

defibrillator circuitry connected to the lead, the defibrillator circuitry designed to defibrillate the heart of a human patient after the occurrence of ventricular fibrillation;

a processor to compute the value of at least one heart signal parameter for each of the multiplicity of beats of the electrogram; and

digital memory designed to store the computed values of the at least one heart signal parameter during a pre-specified time period which is a data collection time period.

103. An implantable cardiotracker for providing early warning of rejection of a heart transplant in a human heart transplant patient, the cardiotracker including:

at least two implanted electrodes that are positioned within the human patient to sense the electrical signal from the patient'"'"'s heart, the electrical signal being an electrogram which consists of a multiplicity of beats;

a processor to compute and place into a digital memory the average QRS voltage for the multiplicity of beats of the electrogram for a first and a second data collection time period, the first data collection time period being a baseline data collection time period when the patient is not experiencing rejection of the transplanted heart and the second data collection time period being some later time period when the patient is starting to reject the transplanted heart.

104. The implantable cardiotracker of claim 103 further including an internal alarm system which is triggered when the average QRS voltage during the second data collection time period exceeds the baseline average QRS voltage by an amount that exceeds a preset threshold level that is set into the implanted cardiotracker.

105. The implantable cardiotracker of claim 103 further including an external alarm system which is triggered when the average QRS voltage during the second data collection time period exceeds the baseline average QRS voltage by an amount that exceeds a preset threshold level that is set into the implanted cardiotracker.

106. An implantable cardiotracker for tracking the level of coronary ischemia of a human patient, the cardiotracker including:

at least two implanted electrodes that are positioned within the human patient to sense the electrical signal from the patient'"'"'s heart, the electrical signal being an electrogram which consists of a multiplicity of beats;

a processor to compute and place into a digital memory the average value of the ST deviation for the multiplicity of beats of the electrogram for a first and a second data collection time period, the first data collection time period being a baseline data collection time period when the patient is not experiencing coronary ischemia and the second data collection time period being some later time period when the patient is experiencing coronary ischemia.

107. The implantable cardiotracker of claim 106 further including an internal alarm system which is triggered when the average value of the ST deviation during the second data collection time period exceeds the baseline average ST deviation by an amount that exceeds a preset threshold level that is set into the implanted cardiotracker.

108. The implantable cardiotracker of claim 106 further including an external alarm system which is triggered when the average value of the ST deviation during the second data collection time period exceeds the baseline average ST deviation by an amount that exceeds a preset threshold level that is set into the implanted cardiotracker.