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

Patent metadata

Field	Value
Publication number	US-10660690-B2
Application number	US-96623207-A
Country	US
Kind code	B2
Filing date	Dec 28, 2007
Priority date	Dec 28, 2007
Publication date	May 26, 2020
Grant date	May 26, 2020

Abstract

A catheter and patch electrode system is provided for use with an apparatus, such as 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 RF ablation generator may also produce an ablation signal across a source wire and an indifferent return patch electrode. The system further includes a cable that connects the generator to a catheter. The catheter includes a shaft having a proximal end and a distal end, with an ablation tip electrode disposed at the distal end. A source lead is electrically coupled to the tip electrode and extends through the shaft to the proximal end where it is terminated. An optional sense lead is also electrically coupled to the tip electrode and extends through the shaft to the proximal end. The system further includes a source return (e.g., skin patch) and a sense return (e.g., skin patch), either or none of which may be combined with the indifferent return, and if used may be placed on opposite sides of the patient for improved performance. 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. A catheter, comprising:
an elongated shaft having a shaft proximal end and a shaft distal end;
an electrode disposed at said shaft distal end;
a source lead having a source lead proximal end and a source lead distal end and electrically connected to said electrode at said source lead distal end and extending through said shaft to said shaft proximal end; and
a sense lead having a sense lead proximal end and a sense lead distal end, said sense lead being different from said source lead, said sense lead distal end being directly electrically connected to said electrode and said sense lead extending through said shaft to said shaft proximal end;
a source return having a first end comprising electrically conductive material that is configured for contact with a patient; and
a sense return has a first end and a second end wherein said sense return first end comprises electrically conductive material that is configured for contact with the patient;
wherein said electrode is an ablation electrode, said source lead and said source return being configured for connection to respective connectors of an RF ablation generator to supply RF power to said ablation electrode and to supply an excitation signal for measuring complex impedance, said sense return first end being different from said ablation electrode, said sense lead proximal end and said sense return second end being configured for connection to respective connectors of a complex impedance sensor, and wherein said source return and said sense return are electrically isolated.

2. The catheter of claim 1 wherein said shaft includes a first lumen and a second lumen isolated from said first lumen, said source lead being disposed in said first lumen and said sense lead being disposed in said second lumen.

3. The catheter of claim 1 wherein said shaft includes a first lumen in which said source and sense leads are disposed.

4. The catheter of claim 1 wherein said source and sense leads are terminated separately at said shaft proximal end and configured for connection to at least one of a cable, an ablation generator and a complex impedance sensor configured to determine a complex impedance.

5. The catheter of claim 1 wherein said electrode is an ablation electrode, said source lead being configured for connection to an RF ablation generator to supply RF power to said electrode and for measuring complex impedance.

6. A catheter system for use with an apparatus having a four-wire interface including positive and negative source connectors across which is produced an excitation signal and positive and negative sense connectors, said system comprising:
a catheter comprising an elongated shaft having a shaft proximal end and a shaft distal end, a tip electrode disposed at said shaft distal end, a source lead having source lead proximal and distal ends wherein said source lead distal end is electrically connected to said tip electrode and said source lead extending through said shaft to said shaft proximal end and configured for connection to said positive source connector to receive said excitation signal, said electrode being further configured for electrical connection to said positive sense connector, said catheter further including a sense lead having a sense lead proximal end and a sense lead distal end, said sense lead being different from said source lead, said sense lead distal end being directly electrically connected to said electrode, said source and sense leads being terminated separately at said shaft proximal end;
a source return having a first end comprising electrically-conductive material configured for contact with a patient and a second end configured for electrical connection to said negative source connector;
a sense return having a first end comprising electrically-conductive material configured for direct contact with the patient and a second end configured for electrical connection to said negative sense connector;
wherein said apparatus is configured to determine an impedance between said sense connectors;
a patch configured for affixation to a patient and including said source and sense returns.

7. The system of claim 6 wherein said sense lead extends through said shaft to said shaft proximal end; and said system further including a cable having a first end configured for connection to said apparatus and a second end configured for connection to said catheter, said cable having a source conductor and a sense conductor, said source and sense conductors being terminated separately at said first end for connection to said positive source and sense connectors, respectively; said source and sense conductors being terminated separately at said second end for respective connection to said source and sense leads of said catheter.

8. The system of claim 6 further including a cable having a first end configured for connection to said apparatus and a second end configured for connection to said catheter, said cable having a source conductor and a sense conductor, said source and sense conductors being terminated separately at said first end for connection to said positive source and sense connectors, respectively; said source and sense conductors being electrically joined at said second end for connection to said source lead of said catheter.

9. The system of claim 6 wherein said catheter includes a ring electrode disposed proximate to but offset from said tip electrode, and wherein at least one of said source and sense returns comprises said ring electrode.

10. The system of claim 6 wherein said apparatus comprises an ablation generator, said tip electrode comprising an ablation electrode, said ablation generator including an RF power source configured to produce an RF ablation signal across said source connectors for delivery by said ablation electrode.

11. The system of claim 10 wherein said excitation signal has a first frequency, said RF ablation signal has a second frequency, said first and second frequencies being distinguishable.

12. The system of claim 11 wherein said ablation signal has a second frequency of about 450 kHz or higher.

13. The system of claim 6 wherein said excitation signal has a first frequency between about 2 kHz and 200 kHz.

14. The system of claim 13 where said first frequency is about 20 kHz.

15. A catheter system for use with an apparatus having a four-wire interface including positive and negative source connectors across which is produced an excitation signal and positive and negative sense connectors, said system comprising:
a catheter comprising an elongated shaft having a shaft proximal end and a shaft distal end, a tip electrode disposed at said shaft distal end, a source lead having source lead proximal and distal ends wherein said source lead distal end is electrically connected to said tip electrode and said source lead extending through said shaft to said shaft proximal end and configured for connection to said positive source connector to receive said excitation signal, said electrode being further configured for electrical connection to said positive sense connector;
a source return having a first end comprising electrically-conductive material configured for contact with a patient and a second end configured for electrical connection to said negative source connector;
a sense return having a first end comprising electrically-conductive material configured for direct contact with the patient and a second end configured for electrical connection to said negative sense connector;
a cable having a first end configured for connection to said apparatus and a second end configured for connectio

Assignees

• Miller Stephan P
• Kastner Glen H
• Deno D Curtis
• St Jude Medical Atrial Fibrillation Div Inc

Inventors

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

Classifications

• A61B18/1492

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

• A61B2018/00577

  Ablation · CPC title

• A61B2018/165

  Multiple indifferent electrodes · CPC title

• A61B2018/00875

  Resistance or impedance · CPC title

• A61B18/1206 Primary

  Generators therefor · CPC title