METHOD AND APPARATUS FOR RADIOFREQUENCY ABLATION WITH INCREASED DEPTH AND/OR DECREASED VOLUME OF ABLATED TISSUE

• US 20100274238A1
• Filed: 04/22/2009
• Published: 10/28/2010
• Est. Priority Date: 04/22/2009
• Status: Active Grant

• Current Assignee: St. Jude Medical, Atrial Fibrillation Division, Inc. (Abbott Laboratories)
• Original Assignee: St. Jude Medical, Atrial Fibrillation Division, Inc. (Abbott Laboratories)
• Inventors: Klimovitch, Gleb V.
• Granted Patent: US 9,566,107 B2
• Time in Patent Office: Days
• US Class Current: 606/33
• CPC Class Codes: A61B 18/1442 Probes having pivoting end effectors, e.g. forceps
• CPC Class Codes: A61B 18/1447 wherein sliding surfaces cause opening/closing of the end effectors
• CPC Class Codes: A61B 2018/00577 Ablation
• CPC Class Codes: A61B 2018/00642 with feedback, i.e. closed loop control
• CPC Class Codes: A61B 2018/00666 using a threshold value
• CPC Class Codes: A61B 2018/00708 switching the power on or off
• CPC Class Codes: A61B 2018/00875 Resistance or impedance
• CPC Class Codes: A61B 2018/126 bipolar
• CPC Class Codes: A61B 2018/1467 using more than two electrodes on a single probe

Abstract

A method of ablating a tissue site includes at least two stages. A first stage involves conducting bipolar ablation between a first pair of electrodes situated in an opposing arrangement on opposing sides of the tissue site to form a pair of opposing first stage ablation regions extending from respective sides of the tissue towards the center. A second stage involves conducting bipolar ablation between a second pair of electrodes situated in a diametrical arrangement with respect to the first stage ablation regions, which forms a second stage ablation region intermediate the pair of first stage ablation regions. The second stage completes the ablation through the entire depth of the tissue site. Since the overall process can accommodate incomplete ablation during the first stage, lower power, reduced ablation times or both may be used during the first stage, avoiding overheating and with a decrease in ablated tissue volume.

Claims

1. A method of ablating a tissue site, comprising the steps of:

during a first stage, conducting bipolar ablation between a first pair of electrodes in an opposing arrangement on opposing sides of the tissue site so as to form a pair of opposing first stage ablation regions in the site; and

during a second stage, conducting bipolar ablation between a second pair of electrodes in a diametrical arrangement with respect to the first stage ablation regions to form a second stage ablation region intermediate said first stage ablation regions.

2. The method of claim 1 wherein the diametrical arrangement is a first diametrical arrangement, and wherein said method further comprises the step of conducting bipolar ablation, during the second stage, between a third pair of electrodes in a second diametrical arrangement with respect to the first stage ablation regions.

3. The method of claim 1 wherein the second pair of electrodes is different from the third pair of electrodes.

4. The method of claim 1 wherein the second stage comprises first and second intervals, and wherein said step of conducting bipolar ablation during the second stage comprises the sub-steps of:

conducting bipolar ablation during the first interval using the second pair of electrodes in the diametrical arrangement;

moving the second pair of electrodes to a second diametrical arrangement;

conducting bipolar ablation during the second interval using the second pair of electrodes in the second diametrical arrangement.

5. The method of claim 1 further including the steps of configuring, for the first stage, the first and second pairs of electrodes so as to be disposed in the opposing arrangement, and re-configuring, for the second stage, the first and second pairs of electrodes so as to be in a dual diametrical arrangement that includes the diametrical arrangement.

6. The method of claim 5 wherein said step of re-configuring includes the sub-step of:

moving the first and second pairs of electrodes from a first location corresponding to the opposing arrangement to a second location corresponding to the dual diametrical arrangement.

7. The method of claim 6 further including the step of:

mechanically clamping the tissue site proximate the first location.

8. The method of claim 1 wherein said step of conducting bipolar ablation during the second stage includes the sub-step of:

electrically isolating the first pair of electrodes from the tissue site.

9. The method of claim 8 wherein said electrically isolating step includes the sub-step of:

removing the first pair of electrodes from contact with the tissue site.

10. The method of claim 8 wherein said electrically isolating step includes the sub-step of:

interposing a high impedance between the first pair of electrodes and a source of ablation power.

11. The method of claim 10 wherein said interposing step includes the sub-step of selectively advancing and withdrawing an electrically insulative sheath over one or more of the electrodes.

12. The method of claim 1 wherein said steps of conducting bipolar ablation include the sub-step of:

powering in counter-phase the electrodes of at least one of the first and second pairs of electrodes.

13. The method of claim 12 wherein said powering step further includes the sub-steps of:

applying a first signal to one of the electrodes of one of the first and second electrode pairs;

applying a second signal to the other one of the electrodes of the one pair of electrodes wherein the first and second signals are offset in phase by 180 electrical degrees.

14. The method of claim 13 wherein the first and second signals are alternating current (AC) signals having a predetermined frequency.

15. The method of claim 14 wherein the predetermined frequency is in the radio frequency (RF) range between about 50 kHz and 500 kHz.

16. The method of claim 1 wherein said steps of conducting bipolar ablation include the sub-step of:

powering the first pair of electrodes at a substantially constant power.

17. The method of claim 1 further including the steps of:

monitoring an impedance of the tissue site;

discontinuing bipolar ablation during the first stage when the monitored impedance satisfies predetermined criteria.

18. The method of claim 17 wherein said predetermined criteria includes a saturation condition.

19. The method of claim 1 further including the step of:

selecting a first width for the electrodes of the first pair of electrodes for the first stage that is no greater than a second width associated with the second pair of electrodes for the second stage.

20. The method of claim 1 further including the step of:

selecting a length-to-width aspect ratio of the electrodes of the first pair of electrodes that is at least greater than one.

21. The method of claim 20 wherein the aspect ratio is greater than about three (3).

22. An apparatus, comprising:

means for conducting bipolar ablation between a first pair of electrodes in an opposing arrangement on opposing sides of the tissue site so as to form a pair of opposing first stage ablation regions in the site during a first stage; and

means for conducting bipolar ablation between a second pair of electrodes in a diametrical arrangement with respect to the first stage ablation regions to form a second stage ablation region intermediate said first stage ablation regions during a second stage.

23. An apparatus according to claim 22, wherein the diametrical arrangement comprises a first diametrical arrangement, and further comprising:

means for conducting bipolar ablation during the second stage between a third pair of electrodes in a second diametrical arrangement with respect to the first stage ablation regions.

24. An apparatus according to claim 22, wherein the second pair of electrodes comprises a different pair from the third pair of electrodes.

25. An apparatus according to claim 22, wherein the second stage comprises a first interval and a second interval and wherein said means for conducting bipolar ablation during the second stage further comprises:

means for conducting bipolar ablation during the first interval using the second pair of electrodes in the diametrical arrangement;

means for moving the second pair of electrodes to a second diametrical arrangement; and

means for conducting bipolar ablation during the second interval using the second pair of electrodes in the second diametrical arrangement.