Non-invasive method and device to monitor cardiac parameters

• US 7,054,679 B2
• Filed: 10/31/2001
• Issued: 05/30/2006
• Est. Priority Date: 10/31/2001
• Status: Expired due to Term

• Current Assignee: Robert Hirsh
• Original Assignee: Robert Hirsh
• Inventors: Hirsh, Robert
• Primary Examiner(s): Schaetzle, Kennedy
• Application Number:
  US09/999,125
• Publication Number:
  US 20030083582A1
• Time in Patent Office: 1,672 Days
• Field of Search: 600/481, 600/483, 600/485, 600/486, 600/500, 600/504, 600/508, 600/513, 600/526, 600/523
• US Class Current: 600/523
• CPC Class Codes: A61B 5/02028 Determining haemodynamic parameters not otherwise provided for, e.g. cardiac contractility or left ventricular ejection fraction
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/029 Measuring or recording blood output from the heart, e.g. minute volume A61B8/065 takes precedence
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61B 8/06 Measuring blood flow measuring volume flow in general G01F, e.g. G01F1/66, G01F1/72; measuring speed of fluids in general G01P5/00

Abstract

A method of and a device for non-invasively measuring the hemodynamic state of a subject or a human patient involve steps and units of non-invasively measuring cardiac cycle period, electrical-mechanical interval, mean arterial pressure, and ejection interval and converting the measured electrical-mechanical interval, mean arterial pressure and ejection interval into the cardiac parameters such as Preload, Afterload and Contractility, which are the common cardiac parameters used by an anesthesiologist.

The converted hemodynamic state of a patient is displayed on a screen as a three-dimensional vector with each of its three coordinates respectively representing Preload, Afterload and Contractility. Therefore, a medical practitioner looks at the screen and quickly obtains the important and necessary information.

Claims

1. A method of monitoring cardiac parameters, comprising the steps of:

non-invasively measuring a plurality of predetermined non-invasive cardiac parameters from a subject;

converting the non-invasive cardiac parameters into a plurality of invasive cardiac analogues based upon a set of predetermined conversion equations; and

displaying a vector indicating a hemodynamic state.

2. The method of monitoring cardiac parameters according to claim 1 wherein the subject is a human.

3. The method of monitoring cardiac parameters according to claim 1 wherein the subject is an animal.

4. The method of monitoring cardiac parameters according to claim 1 wherein the predetermined non-invasive cardiac parameters include heart rate as denoted by HR, ejection interval as denoted by EI, mean arterial pressure as denoted by MAP and electrical-mechanical interval as denoted by E−

M, which is an interval between an electrical event E and a mechanical event M.

5. The method of monitoring cardiac parameters according to claim 4 wherein the predetermined invasive cardiac analogues include preload as denoted by P, afterload as denoted by A and contractility as denoted by C.

6. The method of monitoring cardiac parameters according to claim 5 wherein the predetermined conversion equations include

P=k1(EI*MAP*E−

M)+c1,

A=k2(MAP*E−

M)+c2, and

ln(C)k3(1/E−

M)+c3

where k1, k2, k3, c1, c2 and c3 are empirical proportionality constants.

7. The method of monitoring cardiac parameters according to claim 6 wherein the M in the E−

M is defined as a time when a second derivative with respect to time, M″

(t), reaches a maximum value.

8. The method of monitoring cardiac parameters according to claim 6 wherein the electrical event in determining the E−

M is selected from the group consisting of a Q-wave, a R-wave, an S-wave, and an artificial ventricular pacemaker spike.

9. The method of monitoring cardiac parameters according to claim 6 wherein the electrical event in determining the E−

M interval is determined by double differentiating an EKG voltage curve which corresponds to ventricular depolarization, V(t), with respect to time and defining the electrical event as a time when V″

(t) reaches a maximum positive value.

10. The method of monitoring cardiac parameters according to claim 6 wherein the second mechanical event in determining the E−

M is selected from the group consisting of arterial blood pressure and flow velocity upstroke.

11. The method of monitoring cardiac parameters according to claim 5 wherein the predetermined conversion equations include

P=k1′

((T−

EI)*MAP*E−

M)+c1′

,

A=k2′

(MAP*E−

M)+c2′

, and

ln(C)=k3′

(1/E−

M)+c3′

where k1′

, k2′

, k3′

, c1′

, c2′ and

c3′

are empirical proportionality constants for a particular one of the subjects and T is a time period of the cardiac cycle for the particular one of the subjects.

12. The method of monitoring cardiac parameters according to claim 11 wherein the M in the E−

M is defined as a time when a second derivative with respect to time, M″

(t), reaches a maximum value.

13. The method of monitoring cardiac parameters according to claim 11 wherein the electrical event in determining the E−

M is selected from the group consisting of a Q-wave, a R-wave, an S-wave, and an artificial ventricular pacemaker spike.

14. The method of monitoring cardiac parameters according to claim 13 wherein a mechanical event in determining the E−

M includes a time of an arterial blood pressure upstroke as denoted by TA and a time of a blood flow velocity upstroke as denoted by TF.

15. The method of monitoring cardiac parameters according to claim 11 wherein the electrical event in determining the E−

M interval is determined by double differentiating an EKG voltage curve which corresponds to ventricular depolarization, V(t), with respect to time and defining the electrical event as a time when V″

(t) reaches a maximum positive value.

16. The method of monitoring cardiac parameters according to claim 5 wherein the predetermined conversion equations include

P=k1′

((T−

EI)*MAP*E−

M)+c1′

,

A=k2′

*MAP/[K+exp(1/E−

M)]+c2′

, and

ln(C)=k3′

(1/E−

M)+c3′

where k1′

, k2′

, k3′

, c1′

, c2′ and

c3′

, and K are empirical proportionality constants for a particular one of the subjects and T is a time period of the cardiac cycle for the particular one of the subjects.

17. The method of monitoring cardiac parameters according to claim 5 further comprising the step of displaying the invasive cardiac analogues in three dimensional coordinate space that is defined by a first axis indicative of the P, a second axis indicative of the A and a third axis indicative of the C.

18. The method of monitoring cardiac parameters according to claim 17 further comprising an additional step of displaying a three dimensional object defining a safe zone indicative of a safe hemodynamic state.

19. The method of monitoring cardiac parameters according to claim 18 wherein the first axis, the second axis, the third axis and the three dimensional object are each displayed with a predetermined color.

20. The method of monitoring cardiac parameters according to claim 4 wherein the EI is measured by placing a Doppler ultrasound device over the suprasternal notch near the ascending aorta.

21. The method of monitoring cardiac parameters according to claim 4 wherein the electrical event E in the E−

M is determined by electrocardiograph as denoted by EKG.

22. The method of monitoring cardiac parameters according to claim 4 wherein the E−

M is determined by electrocardiograph as denoted by EKG and by placing a Doppler ultrasound device over a major artery.

23. The method of monitoring cardiac parameters according to claim 4 wherein the E−

M is determined by electrocardiograph as denoted by EKG and by placing a fiberoptic device over a major artery.

24. The method of monitoring cardiac parameters according to claim 1 further comprising an additional step of displaying a vector cross product between the vector and a predetermined vector indicating an amount of physiologic stress.

25. The method of monitoring cardiac parameters according to claim 1 further comprising an additional step of determining a fitness level of the subject based upon the invasive cardiac analogues.

26. The method of monitoring cardiac parameters according to claim 1 further comprising the step of determining management of an anesthetic-related procedure of the subject based upon the invasive cardiac analogues.

27. The method of monitoring cardiac parameters according to claim 1 further comprising the step of determining an abnormal cardiac condition of the subject based upon the invasive cardiac analogues.

28. The method of monitoring cardiac parameters according to claim 1 further comprising the step of transferring the non-invasive cardiac parameters from one location to another location before converting the non-invasive cardiac parameters into the invasive cardiac analogues.

29. The method of monitoring cardiac parameters according to claim 28 further comprising the step of evaluating a cardiac condition of the subject based upon the invasive cardiac analogues.

30. A system for monitoring cardiac parameters comprising:

a non-invasive cardiac parameter measuring unit for non-invasively measuring a plurality of predetermined non-invasive cardiac parameters from a subject;

a conversion unit connected to said non-invasive cardiac parameter measuring unit for converting the non-invasive cardiac parameters into a plurality of invasive cardiac analogues based upon a set of predetermined conversion equations and;

a display unit connected to said conversion unit for displaying a vector indicative of a hemodynamic state.

31. The system for monitoring cardiac parameters according to claim 30 wherein said non-invasive cardiac parameter measuring unit measures the predetermined non-invasive cardiac parameters from a human.

32. The system for monitoring cardiac parameters according to claim 30 wherein said non-invasive cardiac parameter measuring unit measures the predetermined non-invasive cardiac parameters from an animal.

33. The system for monitoring cardiac parameters according to claim 30 wherein said non-invasive cardiac parameter measuring unit further comprises a heart rate monitor for measuring heart rate as denoted by HR, a vibration sensing device for measuring an ejection interval as denoted by EI and a mechanical event M of an electrical-mechanical interval as denoted by E−

M, a blood pressure measuring device for measuring mean arterial pressure as denoted by MAP and an electrocardiogram measuring device for measuring an electrical event E of the electrical-mechanical interval.

34. The system for monitoring cardiac parameters according to claim 33 wherein said vibration sensing device comprises at least one of a Doppler ultrasound device, an optical plethysmographic device and a fiber optic device.

35. The system for monitoring cardiac parameters according to claim 30 wherein said conversion unit outputs the predetermined invasive cardiac analogues including preload as denoted by P, afterload as denoted by A and contractility as denoted by C.

36. The system for monitoring cardiac parameters according to claim 35 wherein said conversion unit determines the P, the A and the C based upon the predetermined conversion equations including

P=k1(EI*MAP*E−

M)+c1,

A=k2(MAP*E−

M)+c2, and

ln(C)k3(1/E−

M)+c3

where k1, k2, k3, c1, c2 and c3 are empirical proportionality constants.

37. The system for monitoring cardiac parameters according to claim 35 wherein said conversion unit determines the P, the A and the C based upon the predetermined conversion equations including

P=k1′

((T−

EI)*MAP*E−

M)+c1′

,

A=k2′

(MAP*E−

M)+c2′

, and

ln(C)=k3′

(1/E−

M)+c3′

,

where k1′

, k2′

, k3′

, c1′

, c2′ and

c3′

are empirical proportionality constants for a particular one of the subjects and T is a time period of the cardiac cycle for the particular one of the subjects.

38. The system for monitoring cardiac parameters according to claim 37 wherein said conversion unit obtains the mechanical event M in the E−

M by determining a time when a second derivative with respect to time, M″

(t) reaches a maximum value.

39. The system for monitoring cardiac parameters according to claim 38 wherein said non-invasive cardiac parameter measuring unit measures an electrical event in determining the E−

M, the electrical event being selected from the group consisting of a Q-wave as denoted by Q, a R-wave as denoted by R, a S-wave as denoted by S and an artificial ventricular pacemaker spike.

40. The system for monitoring cardiac parameters according to claim 39 wherein said non-invasive cardiac parameter measuring unit measures the mechanical event in determining the E−

M, the second mechanical event including a time of an arterial blood pressure upstroke as denoted by TA and a time of a flow velocity upstroke as denoted by TF.

41. The system for monitoring cardiac parameters according to claim 38 wherein said non-invasive cardiac parameter measuring unit measures an electrical event in determining the E−

M interval by double differentiating an EKG voltage curve which corresponds to ventricular depolarization, V(t), with respect to time and defining the electrical event as a time when V″

(t) reaches a maximum positive value.

42. The system for monitoring cardiac parameters according to claim 35 wherein said conversion unit determines the P, the A and the C based upon the predetermined conversion equations including

P=k1′

(DI*MAP*E−

M)+c1′

,

A=k2′

(MAP*E−

M)+c2′

, and

ln(C)=k3′

(1/E−

M)+c3′

where k1′

, k2′

, k3′

, c1′

, c2′ and

c3′

are empirical proportionality constants for a particular one of the subjects, DI is a diastolic filling interval, and T is a time period of the cardiac cycle for the particular one of the subjects.

43. The system for monitoring cardiac parameters according to claim 35 wherein said conversion unit determines the P, the A and the C based upon the predetermined conversion equations including

P=k1′

((T−

EI)*MAP*E−

M)+c1′

,

A=k2′

*MAP/[K+exp(1/E−

M)]+c2′

, and

ln(C)=k3′

(1/E−

M)+c3′

where k1′

, k2′

, k3′

, c1′

, c2′

, c3′

, and K are empirical proportionality constants for a particular one of the subjects and T is a time period of the cardiac cycle for the particular one of the subjects.

44. The system for monitoring cardiac parameters according to claim 35 wherein said display unit displays the invasive cardiac analogues in three dimensional coordinate space that is defined by a first axis indicative of the P, a second axis indicative of the A and a third axis indicative of the C.

45. The system for monitoring cardiac parameters according to claim 44 wherein said display unit additionally displays a three dimensional object defining a safe zone indicative of a safe hemodynamic state.

46. The system for monitoring cardiac parameters according to claim 45 wherein said display unit displays the first axis, the second axis, the third axis and the safe zone respectively in a predetermined color.

47. The system for monitoring cardiac parameters according to claim 45 wherein said display unit additionally displays a vector cross product between the vector and a predetermined vector indicative of an amount of physiologic stress.

48. The system for monitoring cardiac parameters according to claim 30 further comprising a determination unit connected to said conversion unit for determining a fitness level of the subject based upon the invasive cardiac analogues.

49. The system for monitoring cardiac parameters according to claim 30 further comprising a determination unit connected to said conversion unit for determining management of an anesthetic-related procedure of the subject based upon the invasive cardiac analogues.

50. The system for monitoring cardiac parameters according to claim 30 further comprising a determination unit connected to said conversion unit for determining an abnormal cardiac condition of the subject based upon the invasive cardiac analogues.

51. The system for monitoring cardiac parameters according to claim 30 further comprising a data communication unit connected to said non-invasive cardiac parameter measuring unit at one location for transferring the non-invasive cardiac parameters to said conversion unit at another location before converting the non-invasive cardiac parameters into the invasive cardiac analogues.

52. The system for monitoring cardiac parameters according to claim 51 wherein said data communication unit transfers the non-invasive cardiac parameters to said conversion unit via the Internet.

53. The system for monitoring cardiac parameters according to claim 51 wherein said data communication unit transfers the non-invasive cardiac parameters to said conversion unit via telecommunication.

54. The system for monitoring cardiac parameters according to claim 30 wherein said non-invasive cardiac parameter measuring unit is portable.

55. The system for monitoring cardiac parameters according to claim 30 wherein said conversion unit is retrofitted to an existing one of said non-invasive cardiac parameter measuring unit.

56. A method of defining a hemodynamic state, comprising the steps of:

defining a predetermined range of a vector space at least in three dimension for hemodynamic states;

measuring a predetermined set of non-invasive cardiac parameters; and

defining a vector in the vector space based upon the non-invasive cardiac parameters.

57. The method of defining a hemodynamic state according to claim 56 further comprising an additional step of displaying the vector in the vector space.

58. The method of defining a hemodynamic state according to claim 56 wherein the vector space is the predetermined range of invasive cardiac parameters and the vector is converted into an invasive cardiac analogue based upon the non-invasive cardiac parameters.

59. The method of defining a hemodynamic state according to claim 58 wherein the non-invasive cardiac parameters include {T, MAP, EI, DI, E−

M}, where the T is a period of a given cardiac cycle, the MAP is a mean arterial pressure value during the T, the EI is an ejection interval, the DI is a diastolic interval, the E−

M is an electrical-mechanical interval.

60. The method of defining a hemodynamic state according to claim 59 wherein the invasive cardiac analogue is a LVEDP and is proportional to (DI*MAP*E−

M), wherein the LVEDP is a left ventricular end diastolic pressure.

61. The method of defining a hemodynamic state according to claim 59 wherein the invasive cardiac analogue is SVR and is proportional to (MAP*E−

M), wherein the SVR is a systemic vascular resistance.

62. The method of defining a hemodynamic state according to claim 59 wherein the invasive cardiac analogue is a dp/dtmax and is proportional to exp(1/E−

M), wherein the dp/dtmax is the maximum rate of rise of left ventricular pressure.

63. The method of defining a hemodynamic state according to claim 59 wherein the invasive cardiac analogue is a SV and is proportional to EI*exp(1/E−

M), wherein the SV is a stroke volume.

64. The method of defining a hemodynamic state according to claim 59 wherein the invasive cardiac analogue is a Fbar and is proportional to exp(1/E−

M), wherein the Fbar is an average rate of blood outflow.

65. The method of defining a hemodynamic state according to claim 58 wherein the non-invasive cardiac parameters include {T, MAP, EI, E−

M}, where the T is a period of a given cardiac cycle, the MAP is a mean arterial pressure value during the T, the EI is an ejection interval, the E−

M is an electrical-mechanical interval.

66. The method of defining a hemodynamic state according to claim 58 wherein the non-invasive cardiac parameters include {EI, E−

M}, wherein the EI is an ejection interval, the E−

M is an electrical-mechanical interval.

67. The method of defining a hemodynamic state according to claim 56 wherein the vector space is the predetermined range of the non-invasive cardiac parameters and the vector is a non-invasive cardiac vector.

68. The method of defining a hemodynamic state according to claim 67 wherein the non-invasive vector space is defined by {T, MAP, EI, DI, E−

M}, where the T is a period of a given cardiac cycle, the MAP is a mean arterial pressure value during the T, the EI is an ejection interval, the DI is a diastolic interval, the E−

M is an electrical-mechanical interval.

69. The method of defining a hemodynamic state according to claim 67 wherein the non-invasive vector space is defined by {T, MAP, EI, E−

M}, where the T is a period of a given cardiac cycle, the MAP is a mean arterial pressure value during the T, the EI is an ejection interval, the E−

M is an electrical-mechanical interval.

70. The method of defining a hemodynamic state according to claim 56 wherein the vector is linearly scalable to at least one of the measured non-invasive cardiac parameters.

71. The method of defining a hemodynamic state according to claim 56 wherein the vector is monotonically increasing to at least one of the measured non-invasive cardiac parameters.

72. A method of monitoring a hemodynamic state, comprising the steps of:

taking first sets of non-invasive cardiac measurements to define a safety zone indicative of a vector sub-space containing safety sub-space vectors which define a state of well-being of a particular patient;

taking a second set of the non-invasive cardiac measurements from the particular patient to define a current hemodynamic state vector indicative of a current hemodynamic state; and

comparing the current hemodynamic state vector to a corresponding one of the safety sub-space vectors to generate a comparison result; and

determining an amount of deviation from the state of well-being in the particular patient based upon the comparison result.