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US-12616515-B2 - Estimation of electrode-tissue contact using stem and edge electrodes

US12616515B2US 12616515 B2US12616515 B2US 12616515B2US-12616515-B2

Abstract

A system includes an expandable frame and a processor. The expandable frame includes (i) one or more ablation electrodes disposed over an external surface of the frame and configured to be placed in contact with wall tissue of a cavity of a patient, and (ii) stem and edge electrodes coupled just proximally and just distally to the balloon, respectively. The processor is configured to: (a) measure one or more first impedances between one or more of the ablation electrodes and the stem electrode, (b) measure one or more second impedances between one or more of the ablation electrodes and the edge electrode, and (c) based on the first and second impedances, determine, for at least an ablation electrode from among the one or more ablation electrodes, whether the ablation electrode is in physical contact with the wall tissue.

Inventors

  • Assaf Govari

Assignees

  • BIOSENSE WEBSTER (ISRAEL) LTD.

Dates

Publication Date
20260505
Application Date
20190827

Claims (7)

  1. 1 . A system, comprising: an expandable frame coupled to a distal end of a shaft for insertion into a cavity of an organ of a patient, the expandable frame comprising one or more ablation electrodes disposed over an external surface of the frame, wherein the one or more ablation electrodes are configured to be placed in contact with wall tissue of the cavity; a stem electrode coupled to the distal end of the shaft proximally to the expandable frame, and an edge electrode coupled to the distal end of the shaft distally to the expandable frame; and a processor, which is configured to: measure one or more first impedances between one or more of the ablation electrodes and the stem electrode; measure one or more second impedances between one or more of the ablation electrodes and the edge electrode; and determine, for at least one ablation electrode from among the one or more ablation electrodes, based on the one or more first impedances and the one or more second impedances, whether said at least one ablation electrode is in physical contact with the wall tissue.
  2. 2 . The system according to claim 1 , wherein the processor is configured to determine that the ablation electrode is in physical contact with the tissue by determining that a measured first or second impedance is larger than a prespecified impedance by at least a prespecified minimal value.
  3. 3 . The system according to claim 2 , wherein the prespecified impedance is measured with the ablation electrode being in contact with blood.
  4. 4 . The system according to claim 2 , wherein the prespecified minimal value is stored in a look-up table.
  5. 5 . The system according to claim 1 , wherein the expandable frame comprises an expandable balloon and wherein the external surface of the frame comprises an external surface of a membrane of the balloon.
  6. 6 . The system according to claim 4 , wherein the prespecified impedance comprises approximately 100 to approximately 130 ohms as measured by the electrode.
  7. 7 . The system according to claim 1 , and comprising a relay that is configured to switch, under control of the processor, between two or more of: (i) a first configuration for measuring impedances between the ablation electrodes and the stem and edge electrodes, (ii) a second configuration for measuring impedances between the ablation electrodes and one or more body-surface electrodes, and (iii) a third configuration for performing ablation by driving an electrical signal between the ablation electrodes and a back patch electrode.

Description

FIELD OF THE INVENTION The present invention relates generally to medical probes, and particularly to multi-electrode cardiac ablation catheters. BACKGROUND OF THE INVENTION Various techniques for verifying contact of an electrode of a catheter with cardiac tissue have been proposed in the patent literature. For example, U.S. Patent Application Publication 2007/0255162 describes methods and systems for providing tissue contact assessment, by providing a catheter having a shaft having a plurality of electrodes, positioning the catheter at a tissue treatment site, applying an electrical current between at least two of the plurality of electrodes, measuring impedance voltage between the at least two of the plurality of electrodes and, processing the measured impedance voltage caused by the applied electrical current to provide contact assessment. As another example, U.S. Patent Application Publication 2012/0143179 describes a plurality of catheter-based ablation apparatus embodiments, including balloon catheters, that address several areas of atrial target tissue and which feature firm and consistent ablation element to tissue contact, to enable the creation of effective continuous lesions. In an embodiment, energy may be applied to a distal ring electrode of a balloon catheter, together with a reference electrode positioned on the balloon catheter shaft just proximal to the balloon, to measure the conductance across the balloon. If the balloon solidly occludes the PV, the impedance rises and the measurement can also be used to verify PV occlusion. SUMMARY OF THE INVENTION An embodiment of the present invention provides a system including an expandable frame and a processor. The expandable frame is coupled to a distal end of a shaft for insertion into a cavity of an organ of a patient and includes one or more ablation electrodes disposed over an external surface of the frame, wherein the one or more ablation electrodes are configured to be placed in contact with wall tissue of the cavity. The expandable balloon further includes a stem electrode coupled to the distal end of the shaft proximally to the balloon, and an edge electrode coupled to the distal end of the shaft distally to the balloon. The processor is configured to: (a) measure one or more first impedances between one or more of the ablation electrodes and the stem electrode, (b) measure one or more second impedances between one or more of the ablation electrodes and the edge electrode, and (c) based on the first and second impedances, determine, for at least an ablation electrode from among the one or more ablation electrodes, whether the ablation electrode is in physical contact with the wall tissue. In some embodiments, the processor is configured to determine that the ablation electrode is in physical contact with the tissue by determining that a measured first or second impedance is larger than a prespecified impedance by at least a prespecified minimal value. In some embodiments, the prespecified impedance is measured with the ablation electrode being in contact with blood. In an embodiment, the prespecified minimal value is stored in a look-up table. In another embodiment, the system further includes a relay that is configured to switch, under control of the processor, between two or more of: (i) a first configuration for measuring impedances between the ablation electrodes and the stem and edge electrodes, (ii) a second configuration for measuring impedances between the ablation electrodes and one or more body-surface electrodes, and (iii) a third configuration for performing ablation by driving an electrical signal between the ablation electrodes and a back patch electrode. In some embodiments, the expandable frame includes an expandable balloon and the external surface of the frame includes an external surface of a membrane of the balloon. There is additionally provided, in accordance with an embodiment of the present invention, a method including inserting into a cavity of an organ of a patient an expandable balloon coupled to a distal end of a shaft, the expandable balloon including one or more ablation electrodes disposed over an external surface of a membrane of the balloon, a stem electrode coupled to the distal end of the shaft proximally to the balloon, and an edge electrode coupled to the distal end of the shaft distally to the balloon. One or more of the ablation electrodes are placed in contact with wall tissue of the cavity. One or more first impedances between one or more of the ablation electrodes and the stem electrode are measured. One or more second impedances between one or more of the ablation electrodes and the edge electrode are measured. Based on the first and second impedances, it is determined, for at least an ablation electrode from among the one or more ablation electrodes, whether the ablation electrode is in physical contact with the wall tissue. The present invention will be more fully understood from the followin