Ablation system and method of use
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.
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, increasing 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 RF energy using a first RF electrode.
3. A method as in claim 2 wherein the monitoring of impedance of the first tissue site comprises monitoring impedance using the first RF electrode.
4. A method as in claim 2 wherein monitoring of impedance of the first tissue site comprises monitoring voltage and current measurements to derive impedance.
5. A method as in claim 1 wherein monitoring of impedance of the first tissue site comprises monitoring impedance using dedicated monitoring electrodes.
6. A method as in claim 1 wherein the applying of RF energy to the first tissue site comprises applying RF energy using an irrigated first RF electrode.
7. A method as in any of claims 1 – 6 , wherein the increasing of application of ablating energy to the first tissue site comprises increasing application of ablation energy responsive to a series of monitored impedances that have an acceptable degree of change.
8. A method as in any of claims 1 – 6 , wherein the increasing of application of ablating energy to the first tissue site comprises increasing application of ablation energy responsive to a series of monitored impedances that have an acceptable rate of change.
9. 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, increasing application of ablating energy to the second tissue site.
10. A method as in claim 9 wherein the applying of ablation energy to the second tissue site comprises applying RF energy using a second RF electrode.
11. A method as in claim 10 wherein the monitoring of impedance of the second tissue site comprises monitoring impedance using the second RF electrode.
12. A method as in claim 10 wherein monitoring of impedance of the second tissue site comprises monitoring voltage and current measurements to derive impedance.
13. A method as in claim 9 wherein monitoring of impedance of the second tissue site comprises monitoring impedance using dedicated monitoring electrodes.
14. A method as in claim 9 wherein the applying of RF energy to the second tissue site comprises applying RF energy using an irrigated second RF electrode.
15. A method as in any of claims 9 – 14 , wherein the increasing of application of ablating energy to the second tissue site comprises increasing application of ablation energy responsive to a series of monitored impedances that have an acceptable degree of change.
16. A method as in any of claims 9 – 14 , wherein the increasing of application of ablating energy to the second tissue site comprises increasing application of ablation energy responsive to a series of monitored impedances that have an acceptable rate of change.
17. A method as in any of claims 9 – 14 , wherein the applying of ablation energy to the first and second ablating means is initiated simultaneously.
18. A method as in any of claims 9 – 14 , wherein the applying of ablation energy to the second ablating means is initiated following termination of application of ablation energy to the first ablating means.
19. A method of ablation, comprising:
applying ablation energy to a first tissue site;
monitoring impedance of the first tissue site;
responsive to occurrence of an impedance plateau at the first tissue site, increasing application of ablating energy to the first tissue site; and
responsive to occurrence of a rise in impedance at the first tissue site, modifying application of ablating energy to the first tissue site.
20. A method as in claim 19 wherein the applying of ablation energy to the first tissue site comprises applying RF energy using a first RF electrode.
21. A method as in claim 20 wherein the monitoring of impedance of the first tissue site comprises monitoring impedance using the first RF electrode.
22. A method as in claim 20 wherein monitoring of impedance of the first tissue site comprises monitoring voltage and current measurements to derive impedance.
23. A method as in claim 20 wherein monitoring of impedance of the first tissue site comprises monitoring impedance using dedicated monitoring electrodes.
24. A method as in claim 20 wherein the applying of RF energy to the first tissue site comprises applying RF energy using an irrigated first RF electrode.
25. A method as in claim 19 wherein the modifying of application of ablating energy comprises termination of ablating energy.
26. A method as in any of claims 19 – 25 , wherein the increasing of application of ablating energy to the first tissue site comprises increasing application of ablation energy responsive to a series of monitored impedances that have an acceptable degree of change.
27. A method as in any of claims 19 – 25 , wherein the modifying of application of ablating energy to the first tissue site comprises modifying application of ablation energy responsive to a series of monitored impedances that have an acceptable degree of change.
28. A method as in any of claims 19 – 25 , wherein the increasing of application of ablating energy to the first tissue site comprises increasing application of ablation energy responsive to a series of monitored impedances that have an acceptable rate of change.
29. A method as in any of claims 19 – 25 , wherein the modifying of application of ablating energy to the first tissue site comprises modifying application of ablation energy responsive to a series of monitored impedances that have an acceptable rate of change.
30. A method as in claim 19 , further comprising:
applying ablation energy to a second tissue site;
monitoring impedance of the second tissue site;
responsive to occurrence of an impedance plateau at the second tissue site, increasing application of ablating energy to the second tissue site; and
responsive to occurrence of an impedance rise at the second tissue site, modifying application of ablating energy to the second tissue site.
31. A method as in claim 30 wherein the applying of ablation energy to the second tissue site comprises applying RF energy using a second RF electrode.
32. A method as in claim 31 wherein the monitoring of impedance of the second tissue site comprises monitoring impedance using the second RF electrode.
33. A method as in claim 31 wherein monitoring of impedance of the second tissue site comprises monitoring voltage and current measurements to derive impedance.
34. A method as in claim 30 wherein monitoring of impedance of the second tissue site comprises monitoring impedance using dedicated monitoring electrodes.
35. A method as in claim 30 wherein the modifying of application of ablating energy comprises termination of ablating energy.
36. A method as in claim 31 wherein the applying of RF energy to the second tissue site comprises applying RF energy using an irrigated second RF electrode.
37. A method as in any of claims 30 – 36 , wherein the increasing of application of ablating energy to the second tissue site comprises increasing application of ablation energy responsive to a series of monitored impedances that have an acceptable degree of change.
38. A method as in any of claims 30 – 36 , wherein the modifying of application of ablating energy to the second tissue site comprises modifying application of ablation energy responsive to a series of monitored impedances that have an acceptable degree of change.
39. A method as in any of claims 30 – 36 , wherein the increasing of application of ablating energy to the second tissue site comprises increasing application of ablation energy responsive to a series of monitored impedances that have an acceptable rate of change.
40. A method as in any of claims 30 – 36 , wherein the modifying of application of ablating energy to the second tissue site comprises modifying application of ablation energy responsive to a series of monitored impedances that have an acceptable rate of change.
41. A method as in any of claims 30 – 36 , wherein the applying of ablation energy to the first and second ablating means is initiated simultaneously.
42. A method as in any of claims 30 – 36 , wherein the applying of ablation energy to the second ablating means is initiated following termination of application of ablation energy to the first ablating means.