O.sub.2 level responsive system for and method of treating a malfunctioning heart

• US 4,967,748 A
• Filed: 05/04/1989
• Issued: 11/06/1990
• Est. Priority Date: 10/06/1987
• Status: Expired due to Term

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Leonard Bloom
• Inventors: Cohen, Todd J.
• Primary Examiner(s): Jaworski, Francis
• Assistant Examiner(s): MANUEL, GEORGE C
• Application Number:
  US07/347,814
• Time in Patent Office: 551 Days
• Field of Search: 128/419 P, 128/419 PG, 128/419 D
• US Class Current: 607/6
• CPC Class Codes: A61N 1/36564 controlled by blood pressure
• CPC Class Codes: A61N 1/3918 characterised by shock pathway, e.g. by electrode configuration
• CPC Class Codes: A61N 1/39622 Pacing therapy

Abstract

A system for and method of treating a malfunctioning heart is based on hemodynamics, the O₂ in blood at a site in a patient'"'"'s circulatory system being sensed. A signal is developed representative of short term O₂ level in the blood at the sites preferably at a site (right ventricle or a pulmonary artery) which carries mixed venous blood. A signal representative of a baseline O₂ level (fixed or varying) is provided and if the short term current O₂ level differs therefrom by a predetermined value, an indication of possible hemodynamic compromise, cardioversion/-defibrillation is effected. In a second embodiment, the determination of whether the difference between fixed or varying baseline O₂ level or current O₂ level is undertaken after a rate criteria (for example a heart rate above 155 b.p.m.) has been met. In a third embodiment, the rate and O₂ level criteria both must exist at the same time, before cardioverting/-defibrillation is initiated. In a fourth embodiment, a microprocessor is used. The system may be integrated with antitachycardia and/or antibradycardia pacemakers.

Claims

1. A cardioverting/defibrillating system for treating a malfunctioning heart of a patient, the system comprising, in combination, storage means for storing electrical energy, electrode means for electrically coupling the storage means to the heart, sensing means for sensing O₂ level in blood within a site in a circulatory system, means for providing a first signal representative of baseline O₂ level, means responsive to output from the sensing means for developing a second signal representing current O₂ level in blood at the site over a period of given duration, and means responsive to output from the means for providing the first signal and output from the means for developing the second signal for charging and enabling discharge of the electrical energy stored by the storage means across the electrode means to effect cardioversion/defibrillation upon change indicative of patient-compromise in the current O₂ level in blood at the site of at least a predetermined magnitude from the representative baseline O₂ level in blood.

2. The system according to claim 1, wherein the means providing a signal representative baseline O₂ level is constituted by means providing a signal representative of fixed baseline O₂ level in blood.

3. The system according to claim 2, wherein said sensing means is constituted by means for sensing O₂ level of mixed venous blood.

4. The system according to claim 2, wherein said sensing means is constituted by means for sensing O₂ level in mixed venous blood within a right ventricle of a heart.

5. The system according to claim 2, wherein said sensing means is constituted by means for sensing O₂ level in mixed venous blood within a pulmonary artery.

6. The system according to claim 1, wherein the means for providing a first signal representative of baseline O₂ level is constituted by means for developing a variable first signal representative of mean baseline O₂ level in blood at the site over a period of predetermined duration which is greater than the period of given duration.

7. The system according to claim 6, wherein said sensing means is constituted by means for sensing O₂ level of mixed venous blood.

8. The system according to claim 6, wherein said sensing means is constituted by means for sensing O₂ level in mixed venous blood within a right ventricle of a heart.

9. The system according to claim 6, wherein said sensing means is constituted by means for sensing O₂ level in mixed venous blood within a pulmonary artery.

10. The system according to claim 1, including means responsive to the first signal and to the second signal for providing a control signal indicative of the current O₂ level differing by at least a predetermined amount from the baseline O₂ level, and the means for charging and enabling discharge is responsive to the control signal.

11. The system according to claim 1, including a microprocessor for developing a control signal to control the means for charging and enabling discharge of the electrical energy stored by the storage means.

12. The system according to claim 1, including means for sensing heart rate to produce a distinctive control signal upon the heart rate exceeding a predetermined rate;

controllable antitachycardia pacemaking means for supplying pacing signals to the heart;

controllable cardioverting/defibrillating means, including the storage means for storing electrical energy;

control circuit means, responsive to the distinctive control signal and to an output from the means for charging and enabling discharge, for enabling the antitachycardia pacemaking means in response to presence of the distinctive control signal and contemporaneous absence of the output from the means for charging and enabling, and for enabling the cardioverting/defibrillating means in response to contemporaneous presence of both the distinctive control signal and the output from the means for charging and enabling.

13. The system according to claim 12, including means responsive to output from said means for sensing heart rate for developing a discharge-synchronizing signal synchronized to an R-wave, and the means for discharging electrical energy across the electrode means and into the heart includes means for synchronizing the discharge with the discharge-synchronizing signal to effect cardioversion.

14. The system according to claim 13, wherein the means for discharging electrical energy across the electrode means and into the heart effects discharge on a nonsynchronized basis, in the absence of the synchronization signal, to effect defibrillation.

15. The system according to claim 1, including means for discharging electrical energy across said electrode means and into the heart effects discharge on a nonsynchronized basis to effect defibrillation.

16. The system according to claim 1, further including antitachycardia pacemaking means for supplying tachycardia-correcting signals to the heart.

17. A cardioverting/defibrillating method of treating a malfunctioning heart comprising sensing O₂ level in blood at a site of a circulatory system, providing a representation of baseline O₂ level, determining current O₂ level in blood at the site from the sensed level at the site over a period of given duration, and delivering cardioverting/defibrillating electrical energy to the heart in response to change of at least a predetermined magnitude indicative of patient-compromise in the current O₂ level in blood at the site from the baseline O₂ level.

18. The method according to claim 17, wherein the step of providing a representation of baseline O₂ level in blood comprises providing a fixed representation of baseline O₂ level in blood at the site.

19. The method according to claim 18, wherein the step of sensing O₂ level in blood at the site is constituted by sensing O₂ level in mixed venous blood at the site.

20. The method according to claim 19, wherein the step of sensing O₂ level in mixed venous blood at the site is constituted by sensing O₂ level in mixed venous blood within a right ventricle of a heart.

21. The method according to claim 19, wherein the step of sensing O₂ level in mixed venous blood at the site is constituted by sensing O₂ level in mixed venous blood within a pulmonary artery.

22. The method according to claim 17, wherein the step of providing a representative of baseline O₂ level in blood at the site comprises providing a varying representation of mean baseline O₂ level in blood at the site over a period of predetermined duration which is greater than the period of given duration.

23. The method according to claim 22, wherein the step of sensing O₂ level in blood at the site is constituted by sensing O₂ level in mixed venous blood at the site.

24. The method according to claim 23, wherein the step of sensing O₂ level in mixed venous blood at the site is constituted by sensing O₂ level in mixed venous blood within a right ventricle of a heart.

25. The method according to claim 23, wherein the step of sensing O₂ level in mixed venous blood at the site is constituted by sensing O₂ level in mixed venous blood within a pulmonary artery.

26. The method according to claim 17, wherein the step of delivering cardioverting/defibrillating electrical energy is taken upon current O₂ level in blood at the site differing from baseline O₂ level in blood at the site by at least the predetermined magnitude.

27. The method according to claim 17, including sensing heart rate, the step of delivering cardioverting/defibrillating electrical energy being taken upon the heart rate exceeding a given rate and the current O₂ level in blood at the site differing from baseline O₂ level in blood at the site by at least a predetermined magnitude.

28. The method according to claim 17, further including supplying tachycardia-correcting signals to the heart in absence of patient-compromise and the presence of tachycardia.

29. A cardioverting/defibrillating system for treating a malfunctioning heart comprising, in combination, storage means for storing electrical energy, electrode means for electrically coupling the storage means to the heart, sensing means for sensing O₂ level in blood at a site in a circulatory system, means for providing a first signal representative of baseline O₂ level in blood at the site, means for developing a second signal representing current O₂ level in blood at the site, and means responsive to output from the means for providing the first signal and output from the means for developing the second signal for charging and enabling discharge of the electrical energy stored by the storage means across the electrode means to effect cardioversion/defibrillation upon change indicative of patient compromise in the current O₂ level at the site of at least a predetermined magnitude from the representative baseline O₂ level in blood at the site.

30. The system according to claim 29, further including means for supplying tachycardia-correcting signals to the heart in absence of patient-compromise and presence of tachycardia.

31. A cardioverting/defibrillating method of treating a malfunctioning heart comprising sensing O₂ level in blood within a site in a circulatory system, providing a representation of baseline O₂ level in blood at the site, determining current O₂ level in blood at the site from the sensed level, and discharging electrical energy into the heart to effect cardioversion/defibrillation in response to change of at least a predetermined magnitude in the current O₂ level in blood at the site from the baseline O₂ level in blood at the site indicative of patient-compromise.

32. The method according to claim 31, further including supplying tachycardia-correcting signals to the heart in absence of patient-compromise and presence of tachycardia.

33. A cardioverting/defibrillating system for treating a malfunctioning heart comprising sensing means for sensing O₂ level in blood within a site in a circulatory system, means for providing a first signal representative of baseline O₂ level in blood at the site, means responsive to output from the sensing means for developing a second signal representing current O₂ level in blood at the site, and means responsive to output from the means for providing the first signal and output from the means for developing the second signal for enabling electrical means to effect cardioversion/defibrillation of the malfunctioning hear upon change indicative of patient-compromise in the current O₂ level in blood at the site of at least a predetermined magnitude from the representative baseline O₂ level in blood at the site.

34. The system according to claim 33, wherein the means providing a signal representative baseline O₂ level in blood at the site is constituted by means providing a signal representative of fixed baseline O₂ level in blood at the site.

35. The system according to claim 34, wherein said sensing means is constituted by sensing means for sensing O₂ level in mixed venous blood.

36. The system according to claim 35, wherein said sensing means is constituted by sensing means for sensing O₂ level in mixed venous blood within a right ventricle of a heart.

37. The system according to claim 35, wherein said sensing means is constituted by means for sensing O₂ level in mixed venous blood within a pulmonary artery.

38. The system according to claim 33, wherein the means for providing a first signal representative of baseline O₂ level is constituted by means for developing a variable first signal representative of mean baseline O₂ level in blood at the site over a period of predetermined duration.

39. The system according to claim 38, wherein said sensing means is constituted by sensing means for sensing O₂ level in mixed venous blood.

40. The system according to claim 39, wherein said sensing means is constituted by sensing means for sensing O₂ level in mixed venous blood within a right ventricle of a heart.

41. The system according to claim 39, wherein said sensing means is constituted by means for sensing O₂ level in mixed venous blood within a pulmonary artery.

42. The system according to claim 33, further including means for supplying tachycardia-correcting signals to the heart in absence of patient-compromise and presence of tachycardia.

43. A cardioversion/defibrillation system for treating a malfunctioning heart comprising means for monitoring O₂ in blood at a site within a circulator system of a patient to provide an output representing O₂ level in blood at the site and means responsive to the output for supplying cardioverting/defibrillating energy to the heart upon the O₂ level in blood at the site falling to or below a patient-compromising level.

44. The system according to claim 43, including means for supplying tachycardia-correcting signals to the heart.

45. A cardioverting/defibrillating method of treating a malfunctioning heart comprising continuously monitoring O₂ level in blood at at a site in a patient'"'"'s circulatory system, and delivering cardioverting/defibrillating energy to the malfunctioning heart upon the O₂ level in blood at the site falling to or below a patient-compromising level.

46. The method according to claim 45, further including supplying Tachycardia-correcting signals to the heart in absence of patient-compromise and presence of tachycardia.

47. In a system for treating a malfunctioning heart of the type which includes storage means for storing electrical energy, electrode means for electrically coupling the storage means to the heart, sensing means for sensing O₂ level in mixed venous blood within a pulmonary artery in a circulatory system, means for providing a first signal representative of fixed baseline O₂ level, means responsive to output from the sensing means for developing a second signal representing current O₂ level in blood at the site over a period of given duration, and means responsive to output from the means for providing the first signal and output from the means for developing the second signal for charging and enabling discharge of the electrical energy stored by the storage means across the electrode means upon change in the current O₂ level in blood within said pulmonary artery of at least a predetermined amount from the representative baseline O₂ level in blood.

48. The system according to claim 47, including means responsive to the first signal and to the second signal for providing a control signal indicative of the current O₂ level differing by at least a predetermined amount from the baseline O₂ level, and the means for charging and enabling discharge is responsive to the control signal.

49. The system according to claim 47, including a microprocessor for developing a control signal to control the means for charging and enabling discharge of the electrical energy stored by the storage means.

50. The system according to claim 47, including means for sensing heart rate to produce a distinctive control signal upon the hear rate exceeding a predetermined rate;

controllable antitachycardia pacemaking means for supplying pacing signals to the heart;

controllable cardioverting/defibrillating means, including the storage means for storing electrical energy;

control circuit means, responsive to the distinctive control signal and to an output from the means for charging and enabling discharge, for enabling the antitachycardia pacemaking means in response to presence of the distinctive control signal and contemporaneous absence of the output from the means for charging and enabling, and for enabling the cardioverting/defibrillating means in response to contemporaneous presence of both the distinctive control signal and the output from the means for charging and enabling.

51. The system according to claim 50, including means responsive to output from said means for sensing heart rate for developing a discharge-synchronizing signal synchronized to an R-wave, and the means for discharging electrical energy across the electrode means and into the heart includes means for synchronizing the discharge with the discharge-synchronizing signal to effect cardioversion.

52. The system according to claim 51, wherein the means for discharging electrical energy across the electrode means and into the heart effects discharge on a nonsynchronized basis, in the absence of the synchronization signal, to effect defibrillation.

53. The system according to claim 47, including means for discharging electrical energy across said electrode means and into the heart effects discharge on a nonsynchronized basis to effect defibrillation.

54. In a system for treating a malfunctioning heart of the type which includes storage means for storing electrical energy, electrode means for electrically coupling the storage means to the heart, sensing means for sensing O₂ level in mixed venous blood within a pulmonary artery in a circulatory system, means for providing a variable first signal representative of a variable baseline O₂ level, means responsive to output from the sensing means for developing a second signal representing current O₂ level in blood at the site over a period of given duration, and means responsive to output from the means for providing the first signal and output from the means for developing the second signal for charging and enabling discharge of the electrical energy stored by the storage means across the electrode means upon change in the current O₂ level in blood within said pulmonary artery of at least a predetermined amount from the representative baseline O₂ level in blood.

55. The system according to claim 54, including means responsive to the first signal and to the second signal for providing a control signal indicative of the current O₂ level differing by at least a predetermined amount from the baseline O₂ level, and the means for charging and enabling discharge is responsive to the control signal.

56. The system according to claim 54, including a microprocessor for developing a control signal to control the means for charging and enabling discharge of the electrical energy stored by the storage means.

57. The system according to claim 54, including means for sensing heart rate to produce a distinctive control signal upon the heart rate exceeding a predetermined rate;

controllable antitachycardia pacemaking means for supplying pacing signals to the heart;

controllable cardioverting/defibrillating means, including the storage means for storing electrical energy;

control circuit means, responsive to the distinctive control signal and to an output from the means for charging and enabling discharge, for enabling the antitachycardia pacemaking means in response to presence of the distinctive control signal and contemporaneous absence of the output from the means for charging and enabling, and for enabling the cardioverting/defibrillating means in response to contemporaneous presence of both the distinctive control signal and the output from the means for charging and enabling.

58. The system according to claim 57, including means responsive to output from said means for sensing heart rate for developing a discharge-synchronizing signal synchronized to an R-wave, and the means for discharging electrical energy across the electrode means and into the heart includes means for synchronizing the discharge with the discharge-synchronizing signal to effect cardioversion.

59. The system according to claim 58, wherein the means for discharging electrical energy across the electrode means and into the heart effects discharge on a nonsynchronized basis, in the absence of the synchronization signal, to effect defibrillation.

60. The system according to claim 54, including means for discharging electrical energy across said electrode means and into the heart effects discharge on a nonsynchronized basis to effect defibrillation.

61. A method of treating a malfunctioning heart comprising sensing O₂ level in mixed venous blood at within a pulmonary artery of a circulatory system, providing a representation of baseline O₂ level, determining current O₂ level in blood within said pulmonary artery from the sensed level within said pulmonary artery over a period of given duration, and delivering cardioverting/defibrillating electrical energy to the heart in response to change of at least a predetermined magnitude in the current O₂ level in blood within said pulmonary artery from the baseline O₂ level.

62. The method according to claim 61, wherein the step of providing a representation of baseline O₂ level in blood comprises providing a fixed representation of baseline O₂ level in blood within said pulmonary artery.

63. The method according to claim 61, wherein the step of providing a representative of baseline O₂ level in blood within said pulmonary artery comprises providing a varying representation of mean baseline O₂ level in blood within said pulmonary artery over a period of predetermined duration which is greater than the period of given duration.

64. The method according to claim 61, including sensing heart rate, the step of delivering cardioverting/defibrillating electrical energy being taken upon the heart rate exceeding a given rate and the current O₂ level in blood at the site differing from baseline O₂ level in blood at the site by at least a predetermined magnitude.

65. A system for treating a malfunctioning heart comprising sensing means for sensing O₂ level in mixed venous blood within a pulmonary artery in a circulatory system, means for providing a first signal representative of baseline O₂ level in blood at said pulmonary artery, means responsive to output from the sensing means for developing a second signal representing current O₂ level in blood within said pulmonary artery, and means responsive to output from the means for providing the first signal and output from the means for developing the second signal for enabling electrical means for correcting the malfunction upon change in the current O₂ level in blood within said pulmonary artery of at least a predetermined amount from the representative baseline O₂ level in blood within said pulmonary artery.

66. The system according to claim 65, wherein the means providing a signal representative baseline O₂ level in blood within said pulmonary artery is constituted by means providing a signal representative of fixed baseline O₂ level in blood at the site.

67. The system according to claim 65, wherein the means for providing a first signal representative of baseline O₂ level is constituted by means for developing a variable first signal representative of mean baseline O₂ level in blood within said pulmonary artery over a period of predetermined duration.