Ablation system and method of use

• US 6,648,883 B2
• Filed: 04/24/2002
• Issued: 11/18/2003
• Est. Priority Date: 04/26/2001
• Status: Expired due to Term

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Mehra, Rahul, Francischelli, David E., Stewart, Mark T., Skarda, James R.
• Primary Examiner(s): Gibson, Roy D.
• Assistant Examiner(s): VRETTAKOS, PETER J
• Application Number:
  US10/132,379
• Publication Number:
  US 20030004507A1
• Time in Patent Office: 573 Days
• Field of Search: 606/41, 606/32-34, 606/48-52
• US Class Current: 606/41
• CPC Class Codes: A61B 18/1206 Generators therefor
• CPC Class Codes: A61B 18/1445 at the distal end of a shaft, e.g. forceps or scissors at the end of a rigid rod
• CPC Class Codes: A61B 2018/0016 Energy applicators arranged in a two- or three dimensional array
• CPC Class Codes: A61B 2018/00351 Heart
• CPC Class Codes: A61B 2018/00363 Epicardium
• CPC Class Codes: A61B 2018/00577 Ablation
• CPC Class Codes: A61B 2018/00702 Power or energy
• CPC Class Codes: A61B 2018/00761 Duration
• CPC Class Codes: A61B 2018/00791 Temperature
• CPC Class Codes: A61B 2018/00875 Resistance or impedance
• CPC Class Codes: A61B 2018/00886 Duration
• CPC Class Codes: A61B 2018/1467 using more than two electrodes on a single probe
• CPC Class Codes: A61B 2218/002 Irrigation

Abstract

A system and method for creating lesions and assessing their completeness or transmurality. Assessment of transmurality of a lesion is accomplished by monitoring the impedance of the tissue to be ablated. Rather than attempting to detect a desired drop or a desired increase impedance, completeness of a lesion is detected in response to the measured impedance remaining at a stable level for a desired period of time, referred to as an impedance plateau. The mechanism for determining transmurality of lesions adjacent individual electrodes or pairs may be used to deactivate individual electrodes or electrode pairs, when the lesions in tissue adjacent these individual electrodes or electrode pairs are complete, to create an essentially uniform lesion along the line of electrodes or electrode pairs, regardless of differences in tissue thickness adjacent the individual electrodes or electrode pairs.

Claims

1. A method of ablation, comprising;

applying ablation energy to a first tissue site;

monitoring impedance of the first tissue site; and

responsive to occurrence of an impedance plateau at the first tissue site, the impedance plateau determined by a plurality of |dZ/dt| values In a series of monitored |dZ/dt| values being below a preselected value, terminating application of ablating energy to the first tissue site.

2. A method as in claim 1 wherein the applying of ablation energy to the first tissue site comprises applying R-F energy using a first R-F electrode.

3. A method as In claim 2 wherein the monitoring of impedance of the first tissue site comprises monitoring impedance using the first R-F electrode.

4. A method as in claim 1 wherein the applying of R-F energy to the first tissue site comprises applying R-F energy using an irrigated first R-F electrode.

5. A method as in any of claims 1-4, wherein the terminating of application of ablating energy to the first tissue site comprises terminating application of ablation energy responsive to a series of monitored impedances that have an acceptable degree of change.

6. A method as in any of claims 1-4, wherein the terminating of application of ablating energy to the first tissue site comprises terminating application of ablation energy responsive to a series of monitored impedances that have an acceptable rate of change.

7. A method as in claim 1, further comprising:

applying ablation energy to a second tissue site;

monitoring impedance of the second tissue site; and

responsive to occurrence of an impedance plateau at the second tissue site, terminating application of ablating energy to the second tissue site.

8. A method as in claim 7, wherein the applying of ablation energy to the second tissue site comprises applying R-F energy using a second R-F electrode.

9. A method as in claim 8, wherein the monitoring of impedance of the second tissue site comprises monitoring impedance using the second R-F electrode.

10. A method as in claim 7, wherein the applying of R-F energy to the second tissue site comprises applying R-F energy using an irrigated second R-F electrode.

11. A method as in any of claim 7-10, wherein the terminating of application of ablating energy to the second tissue site comprises terminating application of ablation energy responsive to a series of monitored impedance that have an acceptable degree of change.

12. A method as in any of claims 7-10, wherein the terminating of application of ablating energy to the second tissue site comprises terminating application of ablation energy responsive to a series of monitored impedances that have an acceptable rate of change.

13. A method as in any of claims 7-10, wherein the applying of ablation energy to the first and second tissue sites is initiated simultaneously.

14. A method as in any of claims 7-10, wherein the applying of ablation energy to the second tissue site is initiated following termination of application of ablation energy to the first tissue site.