Ablation system, clamp and method of use
A method and apparatus for ablating tissue are disclosed that comprise positioning two or more bi-directional ablation energy sources in spaced-apart relation in sufficient proximity to the tissue to be ablated so that, upon activation each energy source creates an energy field in the tissue to be ablated. The energy sources are spaced such that the energy fields created by at least one of the activated sources partially overlaps with the energy field created by one or more of the other energy sources. The energy sources are alternately activated and deactivated, so that a substantially constant energy field results where the energy fields created by at least two of the energy sources overlap. While the energy sources are preferably RF energy sources, other energy sources, such as microwave, may be used.
1 . A method of forming a tissue lesion, the method comprising:
positioning at least two electrodes in electrical field communication with a tissue;
energizing the at least two electrodes to create an overlapping electric field to originate a tissue ablation buried within the tissue, spaced from a tissue surface, that includes repetitively pulsing the at least two electrodes by delivering energy to a first of the at least two electrodes for a first duration and discontinuing energy delivery to the first of the at least two electrodes for a second duration, and delivering energy to the second of the at least two electrodes for a third duration, and discontinuing energy delivery to the second of the at least two electrodes for a fourth duration.
2 . The method of claim 1 , wherein the at least two electrodes further includes at least two complementary electrodes to create at least two pairs of electrodes.
3 . The method of claim 2 , wherein:
positioning the at least two electrodes includes positioning the at least two pairs of electrodes so that tissue is sandwiched between each of the at least two pairs of electrodes.
4 . The method of claim 3 , wherein:
the at least two pairs of electrodes are associated with opposing jaws of a clamp;
a first of the opposing jaws includes the at least two electrodes;
a second of the opposing jaws includes the at least two complementary electrodes.
5 . A method of forming tissue lesions, the method comprising:
positioning a first electrode and a second electrode in electric field communication with a tissue, where the first and second electrodes are spaced apart by a predetermined distance;
repetitively pulsing the first electrode to generate a first electric field within the tissue;
repetitively pulsing the second electrode to generate a second electric field within the tissue;
forming a first lesion in the tissue originating at a location buried between opposed surfaces of the tissue and growing outward toward the opposed surfaces.
6 . The method of claim 5 , wherein:
positioning the first electrode and the second electrode in electric field communication with the tissue includes positioning a third electrode and a fourth electrode in electric field communication with the tissue, where the tissue interposes the first and second electrodes and the third and fourth electrodes.
7 . The method of claim 6 , wherein:
the first, second, third, and fourth electrodes demarcate a boundary; and
the first lesion is transmural and located within the boundary.
8 . The method of claim 6 , wherein:
the first, second, third, and fourth electrodes are associated with opposing jaws of a clamp;
a first of the opposing jaws includes the first and second electrodes;
a second of the opposing jaws includes the third and fourth electrodes.
9 . The method claim 6 , wherein:
the first and third electrodes comprise a first pair of electrodes;
repetitively pulsing the first electrode includes pulsing the first pair of electrodes for a first period, and discontinuing pulsing the first pair of electrodes for a second period, and repeating the pulsing and the discontinuing pulsing of the first pair of electrodes;
the second and fourth electrodes comprise a second pair of electrodes;
repetitively pulsing the second electrode includes pulsing the second pair of electrodes for a third period, and discontinuing pulsing the second pair of electrodes for a fourth period, and repeating the pulsing and the discontinuing pulsing of the second pair of electrodes.
10 . A method of forming a tissue lesion, the method comprising:
generating at least a substantially constant energy field within a tissue to originate a lesion buried between opposing tissue surfaces, and that grows toward the opposing tissue surfaces, by alternately energizing a first electrode and a second electrode in contact with the tissue.
11 . The method of claim 10 , wherein alternately energizing the first electrode and the second electrode occurs at a frequency between about 2 and 575 Hertz.
12 . The method of claim 10 , wherein alternately energizing the first electrode and the second electrode occurs at a frequency between about 10 and 376 Hertz.
13 . The method of claim 10 , wherein alternately energizing the first electrode and the second electrode causes the first electrode to have a duty cycle of 50 percent on and 50 percent off.
14 . The method of claim 10 , wherein alternately energizing the first electrode and the second electrode causes the first electrode to have a duty cycle of greater than 50 percent on and less than 50 percent off.
15 . The method of claim 10 , wherein an impedance of the tissue in contact with the first and second electrodes is less than an impedance of the tissue at the lesion.
16 . The method of claim 10 , wherein an area of overlapping current flux coincides with where the lesion is originated.
17 . The method of claim 10 , wherein alternately energizing the first electrode and the second electrode continues until the lesion is transmural.
18 . The method of claim 10 , further comprising measuring a temperature of the tissue proximate the lesion to provide an indication of ablation progress.