Method and Apparatus for Determining Cardiac Performance in a Patient

• US 20090210020A1
• Filed: 12/14/2006
• Published: 08/20/2009
• Est. Priority Date: 12/22/2005
• Status: Active Application

• Current Assignee: John A. Pearce, Jonathan W. Valvano, Marc D. Feldman
• Original Assignee: John A. Pearce, Jonathan W. Valvano, Marc D. Feldman
• Inventors: Feldman, Marc D., Valvano, Jonathan W., Pearce, John A.
• Application Number:
  US12/086,040
• Publication Number:
  US 20090210020A1
• Time in Patent Office: Days
• US Class Current: 607/4
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/413 Monitoring transplanted tissue or organ, e.g. for possible rejection reactions after a transplant
• CPC Class Codes: A61N 1/3627 for treating a mechanical deficiency of the heart, e.g. congestive heart failure or cardiomyopathy
• CPC Class Codes: A61N 1/36514 controlled by a physiological quantity other than heart potential, e.g. blood pressure controlled by two or more physical parameters A61N1/36585
• CPC Class Codes: A61N 1/36585 controlled by two or more physical parameters
• CPC Class Codes: A61N 1/368 comprising more than one electrode co-operating with different heart regions A61N1/3622, A61N1/3627 take precedence
• CPC Class Codes: A61N 1/36842 Multi-site stimulation in the same chamber
• CPC Class Codes: A61N 1/36843 Bi-ventricular stimulation
• CPC Class Codes: A61N 1/3702 Physiological parameters A61N1/365 takes precedence; evoked response A61N1/371
• CPC Class Codes: A61N 1/39622 Pacing therapy
• CPC Class Codes: A61N 1/3968 Constructional arrangements, e.g. casings A61N1/375 takes precedence

Abstract

An apparatus for determining heart transplant rejection of a heart in a patient includes at least two electrodes adapted to be sewn into the heart that span the left ventricle. The apparatus includes a voltage generator adapted to be inserted in the patient which generates a voltage to the two electrodes and senses the resulting voltage from the two electrodes. A method for determining heart transplant rejection of a heart in a patient. A pacemaker for a patient (including bi-ventricular pacing and AICDs). The pacemaker includes an RV lead having four electrodes adapted to be inserted into the RV apex. The pacemaker includes a voltage generator which generates a voltage signal to the electrodes and senses the instantaneous voltage along the length of the RV and determines the real and imaginary components to remove the myocardial components of the septum and RV free wall to determine absolute RV blood volume. The pacemaker includes a battery connected to the voltage generator. The pacemaker includes a defibrillator connected to the battery. The pacemaker can also be a bi-ventricular pacemaker to restore RV and LV synchrony during contraction. A method for assisting a heart of a patient.

Claims

1. An apparatus for determining heart transplant rejection of a heart in a patient comprising:

at least two electrodes adapted to be sewn into the heart that span the left ventricle; and

a voltage generator adapted to be inserted in the patient which generates a voltage to the two electrodes and senses the resulting voltage from the two electrodes.

2. An apparatus as described in claim 1 including a third electrode and a fourth electrode adapted to be implanted in the LV myocardium, and wherein the voltage generator determines both the magnitude and phase angle of the resulting voltage from the two electrodes and the third and fourth electrodes.

3. An apparatus as described in claim 2 wherein the voltage generator is adapted to be implanted in the chest of the patient and is in communication with the electrodes.

4. An apparatus as described in claim 3 wherein the voltage regulator includes a processor.

5. An apparatus as described in claim 4 including a pressure sensor for measuring instantaneous pressure of the heart chamber in communication with the processor.

6. An apparatus as described in claim 5 wherein the processor produces a single wave form at a desired frequency for the conductance (admittance) catheter.

7. An apparatus as described in claim 6 wherein the processor produces a plurality of desired wave forms at desired frequencies for the conductance (admittance) catheter.

8. An apparatus as described in claim 7 wherein the processor produces the plurality of desired wave forms at desired frequencies simultaneously, and the processor separates the plurality of desired wave forms at desired frequencies the processor receives from the conductance (admittance) catheter.

9. An apparatus as described in claim 8 wherein the conductance (admittance) catheter includes a plurality of electrodes to measure a least one segmental volume of a heart chamber.

10. An apparatus as described in claim 9 wherein the non-linear relationship depends on a number of the electrodes, dimensions and spacing of the electrodes, and an electrical conductivity of a medium in which the electrodes of the catheter are disposed.

11. An apparatus as described in claim 10 wherein the non-linear relationship is

β

(G)(σ

=0.928S/m)=1+1.774(10<sup>7.481×

10−

4(G−

2057)</sup>)

where;

G is the measured conductance (S), the calculations have been corrected to the conductivity of whole blood at body temperature (0.928 S/m), and 2057 is the asymptotic conductance in uS when the cuvette is filled with a large volume of whole blood.

12. An apparatus as described in claim 11 wherein

13. An apparatus as described in claim 12 wherein the pressure sensor is in contact with the conductance catheter to measure ventricular pressure in the chamber.

14. An apparatus as described in claim 13 wherein the plurality of electrodes includes intermediate electrodes to measure an instantaneous voltage signal from the heart, and outer electrodes to which a current is applied from the processor.

15. An apparatus as described in claim 14 wherein the pressure sensor is disposed between the intermediate electrodes and the outer electrodes.

16. An apparatus as described in claim 15 wherein the processor includes a computer with a signal synthesizer which produces the plurality of desired wave forms at desired single or multiple frequencies and a data acquisition mechanism for receiving and separating the plurality of desired wave forms at desired frequencies.

17. An apparatus as described in claim 16 wherein the computer converts conductance into a volume.

18. An apparatus as described in claim 17 wherein the computer produces a drive signal having a plurality of desired wave forms at desired frequencies to drive the conductance catheter.

19. An apparatus as described in claim 10 wherein

Vol(t)=ρ

L²g_b(t)exp[γ

*(g_b(t))²]

where Vol(t) is the instantaneous volume, ρ

is the blood resistivity, L is the distance between the sensing electrodes, g_b(t) is the instantaneous blood conductance, and γ

is an empirical calibration factor.

20. A pacemaker, including bi-ventricular pacemaker and AICDS, for a patient comprising:

an RV lead having four electrodes spanning the length of the RV adapted to be inserted into the RV apex with at least one of the four electrodes placed in either the right atrium or veins draining into the right heart of the patient;

a voltage generator which generates a voltage signal to the electrodes and senses the instantaneous voltage in the RV and determines the real and imaginary components to remove the myocardial component of the septum and RV free wall to determine absolute RV blood volume;

a battery connected to the voltage generator;

a defibrillator connected to the battery; and

a bi-ventricular pacemaker to resynchronize RV and LV ventricular contraction.

39. A pacemaker as described in claim 20 including a surface epicardial catheter having 4 electrodes.

21. A method for determining heart transplant rejection of a heart in a patient comprising the steps of:

sewing into the heart at least two electrodes that span the left ventricle; and

inserting in the patient a voltage generator which generates a voltage to the two electrodes and senses the resulting voltage from the two electrodes.

22. A method as described in claim 21 including the step of measuring instantaneous pressure of the heart chamber with a pressure sensor in communication with a processor of the voltage regulator.

23. A method as described in claim 22 including the step of producing a plurality of desired wave forms at desired frequencies for the conductance (admittance) catheter.

24. A method as described in claim 23 wherein the producing step includes the step of producing a single waveform at a single frequency.

25. A method as described in claim 23 wherein the producing step includes the step of producing the plurality of desired wave forms at desired frequencies simultaneously, and including the step of the processor separating the plurality of desired way forms at desired frequencies the processor received from the conductance (admittance) catheter.

26. A method as described in claim 25 wherein the producing step includes the step of producing with the processor the plurality of desired wave forms at desired frequencies simultaneously.

27. A method as described in claim 26 wherein the determining step includes the step of applying the non-linear relationship according to

β

(G)(σ

=0.928S/m)=1+1.774(10<sup>7.481×

10−

4(G−

2057)</sup>)

where;

G is the measured conductance (S), the calculations have been corrected to the conductivity of whole blood at body temperature (0.928 S/m), and 2057 is the asymptotic conductance in μ

S when the cuvette is filled with a large volume of whole blood.

28. A method as described in claim 27 wherein the determining step includes the step of determining instantaneous volume according to

29. A method as described in claim 28 wherein the step of measuring instantaneous pressure includes the step of measuring instantaneous pressure with the pressure sensor in contact with the conductance (admittance) catheter to measure the ventricular pressure in the chamber.

30. A method as described in claim 29 wherein the measuring step includes the step of measuring at least one segmental volume of a heart chamber with a plurality of electrodes on the conductance catheter.

31. A method as described in claim 30 wherein the measuring step includes the steps of applying a current to outer electrodes of the plurality of electrodes from the processor, and measuring an instantaneous voltage signal from the heart with intermediate electrodes of the plurality of electrodes.

32. A method as described in claim 31 wherein the step of measuring instantaneous pressure includes the step of measuring instantaneous pressure with the pressure sensor disposed between the intermediate electrodes and the outer electrodes.

33. A method as described in claim 32 wherein the producing with the processor step includes the step of producing with a signal synthesizer of a computer a single wave form at a single frequency.

34. A method as described in claim 33 wherein the producing with the processor step includes the step of producing with a signal synthesizer of a computer the plurality of desired wave forms at desired frequencies, and the processor separating step includes the step of receiving and separating the plurality of desired wave forms at desired frequencies with a data acquisition mechanism of the computer.

35. A method as described in claim 34 including the step of converting conductance (admittance) into a volume with the computer.

36. A method as described in claim 35 including the step of producing with the computer a drive signal having a wave form at a single frequency to drive the conductance (admittance) catheter.

37. A method as described in claim 36 including the step of producing with the computer a drive signal having the plurality of desired wave forms at desired frequencies to drive the conductance (admittance) catheter.

38. A method as described in claim 37 wherein the determining step includes the step of determining instantaneous volume according to

Vol(t)=ρ

_bL²g_b(t)exp[γ

·

(g_b(t))²] 

 

(15)

where Vol(t) is the instantaneous volume, σ

_b is the blood resistivity, L is the distance between the sensing electrodes, g_b(t) is the instantaneous blood conductance, and γ

is an empirical calibration factor.

40. A method for assisting a heart of a patient comprising the steps of:

inserting into the RV apex an RV lead of a pacemaker having four electrodes that span the length of the RV;

generating a voltage signal to the electrodes from a voltage generator; and

sensing the instantaneous voltage in the RV with the voltage generator to determine the real and imaginary components of the voltage to remove the myocardial component of the septum and RV free wall to determine absolute RV blood volume.