Catheter positioning system

• US 6,050,267 A
• Filed: 02/04/1998
• Issued: 04/18/2000
• Est. Priority Date: 04/28/1997
• Status: Expired due to Term

• Current Assignee: American Cardiac Ablation Company Incorporated
• Original Assignee: American Cardiac Ablation Company Incorporated
• Inventors: Nardella, Paul C., Wrublewski, Thomas A.
• Primary Examiner(s): Lacyk, John P.
• Application Number:
  US09/018,435
• Time in Patent Office: 804 Days
• Field of Search: 128/899, 600/547, 600/373, 600/382
• US Class Current: 128/899
• CPC Class Codes: A61B 18/1492 having a flexible, catheter-like structure, e.g. for heart ablation A61B18/1477 takes precedence
• CPC Class Codes: A61B 2034/2053 Tracking an applied voltage gradient
• CPC Class Codes: A61B 5/0536 Impedance imaging, e.g. by tomography
• CPC Class Codes: A61B 5/063 using impedance measurements

Abstract

A system for detecting the position of a catheter in a patient includes three sets of excitation electrodes, with one set disposed in each of three intersecting axes. A signal processor measures a voltage indicative of impedance between a detection electrode disposed on the catheter and each of the three sets of excitation signals in order to determine the X coordinate, Y coordinate and Z coordinate of the catheter. The detected position of the catheter is recorded and the detection of subsequent catheter positions is performed relative to the recorded catheter position. The difference between subsequent catheter positions and the recorded position relative to the X, Y and Z axes is displayed in order to facilitate repositioning of the catheter at the recorded position. Excitation electrode embodiments utilizing as few as four excitation electrodes are disclosed. The excitation electrodes may be surface, subcutaneous or intracardiac electrodes.

Claims

1. An apparatus for detecting a position of a catheter in contact with a patient, wherein the catheter includes a detection electrode and said position is characterized by an X coordinate relative to an X axis, a Y coordinate relative to a Y axis, and a Z coordinate relative to a Z axis, said apparatus comprising:

an X axis excitation electrode;

a Y axis excitation electrode;

a Z axis excitation electrode;

a common excitation electrode;

a signal generator adapted for applying a first excitation signal between the X axis excitation electrode and the common electrode, a second excitation signal between the Y axis excitation electrode and the common electrode, and a third excitation signal between the Z axis excitation electrode and the common electrode; and

a signal processor for measuring the differential voltage indicative of impedance between the detection electrode and X axis excitation electrode and the common electrode in order to determine the X coordinate, the differential voltage indicative of impedance between the detection electrode and the Y axis excitation electrode and the common electrode in order to determine the Y coordinate, and the differential voltage indicative of impedance between the detection electrode and the Z axis excitation electrode and the common electrode in order to determine the Z coordinate.

2. The apparatus of claim 1 wherein the X axis excitation electrode, the Y axis excitation electrode, the Z axis excitation electrode, and the common electrode are surface electrodes adapted for external attachment to the patient.

3. The apparatus of claim 1 wherein the X axis excitation electrode, the Y axis excitation electrode, the Z axis excitation electrode, and the common electrode are subcutaneous electrodes adapted for insertion into the patient.

4. The apparatus of claim 1 wherein the X axis excitation electrode, the Y axis excitation electrode, the Z axis excitation electrode, and the common electrode are intracardiac electrodes adapted for insertion into the cardiac regions of the patient.

5. The apparatus of claim 1 wherein the first excitation signal has a first frequency, the second excitation signal has a second frequency, and the third excitation signal has a third frequency.

6. A method for detecting a position of a catheter in contact with a patient, said catheter including a detection electrode and said position being characterized by an X coordinate relative to an X axis, a Y coordinate relative to a Y axis, and a Z coordinate relative to a Z axis, said method comprising the steps of:

applying a first excitation signal to the patient generating a first electric field between an X axis excitation electrode and a common electrode disposed along the X axis;

applying a second excitation signal to the patient generating a second electric field between a Y axis excitation electrode and the common electrode disposed along the Y axis;

applying a third excitation signal to the patient generating a third electric field between a Z axis excitation electrode and the common electrode disposed along the Z axis;

locating the catheter so that the detection electrode is disposed in the patient within the first, second, and third electric fields; and

measuring the differential voltage between the detection electrode and the X axis excitation electrode and the common electrode to determine the X coordinate, measuring the differential voltage between the detection electrode and the Y axis excitation electrode and the common electrode to determine the Y coordinate, and measuring the differential voltage between the detection electrode and the Z axis excitation electrode and the common electrode to determine the Z coordinate thereby determining the X, Y and Z coordinates of the catheter.

7. The method of claim 6 further comprising the step of providing the X axis excitation electrode, the Y axis excitation electrode, the Z axis excitation electrode, and the common electrode as surface electrodes adapted for external attachment to the patient.

8. The method of claim 6 further comprising the step of providing the X axis excitation electrode, the Y axis excitation electrode, the Z axis excitation electrode, and the common electrode as subcutaneous electrodes adapted for insertion into the patient.

9. The method of claim 6 further comprising the step of providing the X axis excitation electrode, the Y axis excitation electrode, the Z axis excitation electrode, and the common electrode as intracardiac electrodes adapted for insertion into the cardiac regions of the patient.

10. The method of claim 6 wherein the first excitation signal applying step comprises providing the first excitation signal with a first frequency, the second excitation signal providing step comprises providing the second excitation signal with a second frequency, and the third excitation signal providing step comprises providing the third excitation signal with a third frequency.

11. An apparatus for detecting a position of a catheter in contact with a patient, said catheter including a detection electrode and said position being characterized by an X coordinate relative to an X axis, a Y coordinate relative to a Y axis, and a Z coordinate relative to a Z axis, said apparatus comprising:

a pair of X axis intracardiac excitation electrodes disposed along the X axis;

a pair of Y axis intracardiac excitation electrodes disposed along the Y axis;

a pair of Z axis intracardiac excitation electrodes disposed along the Z axis; and

a signal processor for measuring the differential voltage indicative of impedance between the detection electrode and each electrode of the pair of X axis intracardiac excitation electrodes in order to determine the X coordinate, the differential voltage indicative of impedance between the detection electrode and each electrode of the pair of Y axis intracardiac excitation electrodes in order to determine the Y coordinate, and the differential voltage indicative of impedance between the detection electrode and each electrode of the pair of Z axis intracardiac excitation electrodes in order to determine the Z coordinate.

12. The apparatus of claim 11 wherein each of the first, second and third pairs of intracardiac excitation electrodes shares a common electrode.

13. The apparatus of claim 11 further comprising:

a second pair of X axis intracardiac excitation electrodes disposed along a second X axis;

a second pair of Y axis intracardiac excitation electrodes disposed along a second Y axis; and

a second pair of Z axis intracardiac excitation electrodes disposed along a second Z axis.

14. The apparatus of claim 13 wherein the signal processor is adapted for being selectively coupled to either the first pair of X axis electrodes, the first pair of Y axis electrodes, and the first pair of Z axis electrodes or to the second pair of X axis electrodes, the second pair of Y axis electrodes, and the second pair of Z axis electrodes.

15. A method for detecting a position of a catheter in contact with a patient, said position characterized by an X coordinate relative to an X axis, a Y coordinate relative to a Y axis and a Z coordinate relative to a Z axis, comprising the steps of:

positioning a detection electrode on the catheter;

positioning a pair of X axis intracardiac excitation electrodes along the X axis;

applying a first excitation signal between the X axis intracardiac excitation electrodes;

positioning a pair of Y axis intracardiac excitation electrodes along the Y axis;

applying a second excitation signal between the Y axis intracardiac excitation electrodes;

positioning a pair of Z axis intracardiac excitation electrodes along the Z axis;

applying a third excitation signal between the Z axis intracardiac excitation electrodes;

measuring the differential voltage indicative of impedance between the detection electrode and each electrode of the X axis intracardiac excitation electrodes in order to determine the X coordinate;

measuring the differential voltage indicative of impedance between the detection electrode and each electrode of the Y axis intracardiac excitation electrodes in order to determine the Y coordinate; and

measuring the differential voltage indicative of impedance between the detection electrode and each electrode of the Z axis intracardiac excitation electrodes in order to determine the Z coordinate.

16. The method of claim 15 further comprising the step of providing one of each of the X axis intracardiac excitation electrodes, the Y axis intracardiac excitation electrodes, and the Z axis intracardiac excitation electrodes as a common electrode.

17. The method of claim 15 further comprising the steps of:

positioning a second pair of X axis intracardiac excitation electrodes along a second X axis;

positioning a second pair of Y axis intracardiac excitation electrodes along a second Y axis; and

positioning a second pair of Z axis intracardiac excitation electrodes along a second Z axis.

18. The method of claim 17 further comprising the steps of:

measuring the differential voltage indicative of impedance between the detection electrode and each electrode of the second pair of X axis intracardiac excitation electrodes in order to determine the X coordinate;

measuring the differential voltage indicative of impedance between the detection electrode and each electrode of the second pair of Y axis intracardiac excitation electrodes in order to determine the Y coordinate;

measuring the differential voltage indicative of impedance between the detection electrode and each electrode of the second pair of Z axis intracardiac excitation electrodes in order to determine the Z coordinate; and

selecting either the X, Y and Z coordinates determined from differential voltage measurements using the pairs or X-, Y- and Z- axis intracardiac excitation electrodes, or the X, Y and Z coordinates determined from differential voltage measurements using the second pairs of X-, Y- and Z- axis intracardiac excitation electrodes.

19. A method for detecting a position of a catheter in contact with a patient, said position characterized by an X coordinate relative to an X axis, a Y coordinate relative to a Y axis and a Z coordinate relative to a Z axis, comprising the steps of:

positioning a detection electrode on the catheter;

positioning a pair of X axis excitation electrodes along the X axis;

applying a first excitation signal between the X axis excitation electrodes;

positioning a pair of Y axis excitation electrodes along the Y axis;

applying a second excitation signal between the Y axis excitation electrodes;

positioning a pair of Z axis excitation electrodes along the Z axis;

applying a third excitation signal between the Z axis excitation electrodes;

determining the X coordinate by measuring the voltage between the detection electrode and a reference potential derived from the pair of X axis excitation electrodes;

determining the Y coordinate by measuring the voltage between the detection electrode and a reference potential derived from the pair of Y axis excitation electrodes; and

determining the Z coordinate by measuring the voltage between the detection electrode and a reference potential derived from the pair of Z axis excitation electrodes.

20. A method for detecting a position of a catheter in contact with a patient, said position characterized by an X coordinate relative to an X axis, a Y coordinate relative to a Y axis and a Z coordinate relative to a Z axis, comprising the steps of:

positioning a detection electrode on the catheter;

positioning a pair of X axis excitation electrodes along the X axis;

applying a first excitation signal between the X axis excitation electrodes;

positioning a pair of Y axis excitation electrodes along the Y axis;

applying a second excitation signal between the Y axis excitation electrodes;

positioning a pair of Z axis excitation electrodes along the Z axis;

applying a third excitation signal between the Z axis excitation electrodes;

determining the X coordinate by measuring a first voltage between the detection electrode and a first electrode of the pair of X axis excitation electrodes, measuring a second voltage between the detection electrode and a second electrode of the pair of X axis excitation electrodes and determining the difference between the first and second measured voltages;

determining the Y coordinate by measuring a third voltage between the detection electrode and a first electrode of the pair of Y axis excitation electrodes, measuring a fourth voltage between the detection electrode and a second electrode of the pair of Y axis excitation electrodes and determining the difference between the third and fourth measured voltages; and

determining the Z coordinate by measuring a fifth voltage between the detection electrode and a first electrode of the pair of Z axis excitation electrodes, measuring a sixth voltage between the detection electrode and a second electrode of the pair of Z axis excitation electrodes and determining the difference between the fifth and sixth measured voltages.

21. A method for detecting position of a treatment catheter in a patient'"'"'s heart, said treatment catheter including a detection electrode and said position being characterized by an X coordinate relative to an X axis, a Y coordinate relative to a Y axis and a Z coordinate relative to a Z axis, wherein the method comprises the steps of:

positioning a basket catheter in a chamber of the patient'"'"'s heart, said basket catheter having a plurality of flexible electrode-carrying arm members that bow outwardly to position electrodes in contact with a wall of the chamber and stabilize the basket catheter in the chamber, wherein electrodes of said arm members are operative for sensing cardiac signals,

selectively exciting plural ones of said electrodes as X axis excitation electrodes, Y axis excitation electrodes and Z axis excitation electrodes, respectively, to define electric fields in the heart, and

determining the X coordinate, the Y coordinate and the Z coordinate of the treatment catheter by measuring voltages between the detection electrode of the treatment catheter and the selectively excited ones of said electrodes of the basket catheter.