Multifrequency conductance catheter-based system and method to determine LV function in a patient

• US 6,494,832 B1
• Filed: 08/28/2000
• Issued: 12/17/2002
• Est. Priority Date: 03/09/1999
• Status: Expired due to Term

• Current Assignee: Cardiovol, LLC
• Original Assignee: Conductance Technologies, Inc.
• Inventors: Feldman, Marc D., Valvano, Jonathan W., Pearce, John A.
• Primary Examiner(s): Getzow, Scott M.
• Application Number:
  US09/649,727
• Time in Patent Office: 841 Days
• Field of Search: 600/513, 600/547, 600/300, 600/301, 600/483, 600/485
• US Class Current: 600/301
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: A61B 5/0535 Impedance plethysmography for measuring blood flow A61B5/0295
• CPC Class Codes: A61B 5/0538 invasively, e.g. using a catheter
• CPC Class Codes: A61B 5/287 Holders for multiple electrodes, e.g. electrode catheters for electrophysiological study [EPS]

Abstract

An apparatus and method for determining cardiac performance in a patient. The apparatus includes a multifrequency conductance catheter for measuring instantaneous volume of a heart chamber with multifrequencies. The apparatus includes a mechanism for measuring instantaneous pressure of the heart chamber. The apparatus includes a mechanism for separating the multifrequencies. The apparatus includes a mechanism for signal processing the instantaneous volume and the pressure of the heart chamber to identify mechanical strength of the chamber and for automatically producing a plurality of desired waveforms at desired frequencies for the conductance catheter. The processing mechanism is connected to the pressure measuring mechanism, the separating mechanism and the volume measuring mechanism.

Claims

1. An apparatus for determining cardiac performance in a patient comprising:

a multifrequency conductance catheter for measuring instantaneous volume of a heart chamber with multifrequencies;

a mechanism for measuring instantaneous pressure of the heart chamber;

a mechanism for separating the multifrequencies; and

a mechanism for signal processing the instantaneous volume and the pressure of the heart chamber to identify mechanical strength of the chamber and for automatically producing a plurality of desired waveforms at desired frequencies for the conductance catheter, said processing mechanism connected to the pressure measuring mechanism, the separating mechanism and the volume measuring mechanism.

2. An apparatus as described in claim 1 wherein the conductance catheter includes a plurality of electrodes to measure at least one segmental volume of the heart chamber.

3. An apparatus as described in claim 2 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 processing mechanism.

4. An apparatus as described in claim 3 wherein the conductance catheter includes at least one pressure sensor to measure ventricular pressure in the chamber.

5. An apparatus as described in claim 3 wherein the pressure sensor is disposed between the intermediate electrodes and the outer electrodes.

6. An apparatus as described in claim 5 wherein the signal processing mechanism includes a computer with a signal synthesizer and a data acquisition mechanism connected to the catheter.

7. An apparatus as described in claim 6 wherein the signal processing mechanism includes a mechanism for converting conductance into a volume, said converting mechanism connected to the catheter and the computer.

8. An apparatus as described in claim 7 wherein the signal processing mechanism includes a mechanism for producing a drive signal to drive the conductance catheter, said producing mechanism connected to the catheter and the computer.

9. An apparatus as described in claim 8 wherein the converting mechanism includes signal processing circuitry for converting measured conductance to a volume, said signal processing circuitry connected to the catheter and the computer.

10. An apparatus as described in claim 9 wherein the converting mechanism includes a signal conditioning/filter mechanism for reducing noise level of measured conductance, said signal conditioning/filter mechanism connected to the signal processing circuitry and the computer.

11. An apparatus as described in claim 10 wherein the converting mechanism includes a pressure amplifier which amplifies the signal from the solid state pressure sensor, said pressure amplifier connected to the catheter and the signal conditioning/filter mechanism.

12. An apparatus as described in claim 11 wherein the drive mechanism includes an internal oscillator which generates a combined signal source of an amplitude excitation voltage at least at two different frequencies, said internal oscillator connected to the computer and the catheter.

13. An apparatus as described in claim 12 wherein the drive mechanism includes a voltage-to-current amplifier which converts excitation voltage to a current, said voltage-to-current amplifier connected to the internal oscillator and the catheter.

14. An apparatus as described in claim 13 wherein the drive mechanism includes an external input signal synthesizer mechanism for controlling the signal synthesizer of the computer to produce desired waveforms at desired frequencies, said external input signal synthesizer mechanism connected to the computer.

15. An apparatus as described in claim 14 wherein the separating mechanism includes a differential amplifier connected to the intermediate electrodes which extracts a combined signal potential from the intermediate electrodes.

16. An apparatus as described in claim 15 wherein the separating mechanism includes band-pass filters connected to the differential amplifier which separates the frequencies from the combined signal potential.

17. An apparatus as described in claim 16 wherein the signal processing means determines conductance according to

18. An apparatus as described in claim 17 wherein the signal processing means determines conductance according to

19. An apparatus as descibed in claim 18 wherein the signal processing means determines conductance according to

20. An apparatus according to claim 19 wherein the signal processing means determines conductance according to

21. An apparatus according to claim 20 wherein the signal processing means determines conductance according to

23. A method as described in claim 17 wherein the separating step includes the step of separating with active band-pass filters the frequencies from the combined signal potential.

24. A method as described in claim 18 wherein the extracting step includes the step of extracting from the intermediate electrodes with a common mode rejection differential amplifier the combined signal potential from the combined signal.

25. A method as described in claim 19 wherein the sending step includes the step of sending simultaneously the combined signal consisting of at least two frequencies from a combined signal source into a voltage to current amplifier.

26. A method as described in claim 20 wherein the applying step includes the step of applying a constant current from the voltage to current amplifier to the outer electrodes of the conductance catheter.

27. A method as described in claim 21 wherein the identifying step includes the steps of determining instantaneous pressure of the heart from a pressure sensor of the catheter, determining instantaneous volume of the heart from the conductances associated with each frequency and linking instantaneous pressure and instantaneous volume at the same time over time to generate pressure volume loops regarding the heart of the patient.

22. A method for determining cardiac performance in a patient comprising the steps of:

inserting a conductance catheter into an in viva heart;

sending simultaneously a combined signal consisting of at least two frequencies from a signal source into an amplifier;

applying a current to outer electrodes of the conductance catheter;

measuring an instantaneous voltage signal from the heart with intermediate electrodes of the conductance catheter;

extracting from the intermediate electrodes the combined signal potential from the combined signal;

separating the frequencies from the combined signal potential;

determining the separate conductance associated with each frequency; and

identifying pressure volume loops regarding the heart of the patient.