System and method for measurement of an impedance using a catheter such as an ablation catheter

Patent metadata

Field	Value
Publication number	US-12527614-B2
Application number	US-202318399023-A
Country	US
Kind code	B2
Filing date	Dec 28, 2023
Priority date	Dec 28, 2007
Publication date	Jan 20, 2026
Grant date	Jan 20, 2026

Abstract

A catheter and patch electrode system is provided for use with an ablation generator, having a 4-wire interface for improved impedance measurement. The 4-wire interface includes a pair of source connectors across which an excitation signal is produced and a pair of sense connector wires across which the impedance is measured. The system further includes a cable that connects the generator to a catheter that includes a shaft with an ablation tip electrode disposed at a distal end. The impedance sensor circuit produces an excitation signal across the source connectors, which is then carried to the catheter by the cable, then to the tip electrode, travels through the complex load (tissue volume), and returns to the generator via a patch electrode. The impedance is measured by observing the voltage drop across the sense connectors caused by the excitation signal.

First claim

What is claimed is:

1 . An electrophysiology catheter system, comprising:
a catheter having an elongated shaft configured for intra-cardiac use and having a proximal end and a distal end, a first electrode, and a second electrode; a first sense lead electrically connected to the first electrode and extending through the elongated shaft; a second sense lead electrically connected to the second electrode and extending through the elongated shaft; an excitation signal source coupled to the catheter configured to produce an excitation signal comprising an electrical current; a sense circuit configured to measure a response signal induced by the excitation signal as observed across the first and second electrodes, wherein the sense circuit is coupled to the first electrode by the first sense lead, and wherein the sense circuit is coupled to the second electrode by the second sense lead; and a processing circuit configured to process the response signal to determine a complex impedance of a cardiac tissue volume proximate at least one of the first electrode and the second electrode.

2 . The electrophysiology catheter system of claim 1 , wherein the complex impedance comprises at least a magnitude and a phase angle.

3 . The electrophysiology catheter system of claim 1 , wherein the sense circuit comprises a bi-polar sense circuit.

4 . The electrophysiology catheter system of claim 3 , wherein the response signal comprises a bi-polar response signal.

5 . The electrophysiology catheter system of claim 1 , wherein the excitation signal comprises a constant current AC excitation signal configured to develop a corresponding AC response voltage signal.

6 . The electrophysiology catheter system of claim 1 , further comprising an excitation signal return coupled with the sense circuit.

7 . The electrophysiology catheter system of claim 6 , further comprising a patch configured for affixation to a patient and comprising the excitation signal return.

8 . The electrophysiology catheter system of claim 6 , wherein the catheter further comprises a third electrode configured to function as the excitation signal return.

9 . The electrophysiology catheter system of claim 1 , having an increased signal to noise ratio for detecting contacting of a tissue of a patient by the excitation signal source or disengagement of the excitation signal source from the tissue of the patient relative to a two-wire impedance measurement approach that employs a combined source electrode and a combined sense electrode.

10 . A method of determining an impedance of a cardiac tissue volume, comprising:
providing an electrophysiology catheter with an elongated shaft configured for intra-cardiac use and comprising a proximal end and a distal end, a first electrode, a second electrode, a first sense lead, and a second sense lead, wherein the first sense lead is electrically connected to the first electrode and extends through the elongated shaft, and wherein the second sense lead is electrically connected to the second electrode and extends through the elongated shaft; producing an excitation signal comprising an electrical current; measuring, with a sense circuit, a response signal induced by the excitation signal as observed across the first and second electrodes, wherein the sense circuit is coupled to the first electrode by the first sense lead, and wherein the sense circuit is coupled to the second electrode by the second sense lead; and processing the response signal, based on the excitation signal, to determine a complex impedance of the cardiac tissue volume.

11 . The method of claim 10 , wherein the complex impedance comprises at least a magnitude and a phase angle.

12 . The method of claim 10 , wherein the response signal comprises a bi-polar response signal.

13 . The method of claim 10 , wherein the excitation signal comprises a constant current AC excitation signal configured to develop a corresponding AC response voltage signal.

14 . The method of claim 10 , further comprising providing an excitation signal return coupled with the sense circuit.

15 . The method of claim 14 , further comprising providing a patch configured for affixation to a patient and comprising the excitation signal return.

16 . The method of claim 14 , wherein the electrophysiological catheter further comprises a third electrode configured to function as the excitation signal return.

17 . The method of claim 10 , further comprising detecting contacting of a tissue of a patient by an excitation signal source of the excitation signal or disengagement of the excitation signal source of the excitation signal from the tissue of the patient with a increased signal to noise ratio relative to a two-wire impedance measurement approach that employs a combined source electrode and a combined sense electrode.

Assignees

• St Jude Medical Atrial Fibrilation Div Inc
• St Jude Medical Atrial Fibrillation Div Inc

Inventors

• Miller Stephan P
• Kastner Glen H
• Deno Donald Curtis

Classifications

• A61B2018/165

  Multiple indifferent electrodes · CPC title

• A61B2018/00875

  Resistance or impedance · CPC title

• A61B18/1492

  having a flexible, catheter-like structure, e.g. for heart ablation (A61B18/1477 takes precedence) · CPC title

• A61B2018/00577

  Ablation · CPC title

• A61B18/1206 Primary

  Generators therefor · CPC title