Methods and electrode apparatus to achieve a closure of a layered tissue defect
Methods for treating anatomic tissue defects such as a patent foramen ovale generally involve positioning a distal end of a catheter device at the site of the defect, exposing a housing and energy transmission member from the distal end of the catheter, engaging the housing with tissues at the site of the defect, applying suction or other approximating tool to the tissue via the housing to bring the tissue together, and applying energy to the tissue with the energy transmission member or to deliver a clip or fixation device to substantially close the defect. Apparatus generally include a catheter body, a housing extending from a distal end of the catheter body for engaging tissue at the site of the defect, and further adapted to house a fusing or fixation device such as an energy transmission member adjacent a distal end of the housing, or a clip or fixation delivery element.
1. A method for fusing apposed layered tissue structures, the method comprising:
applying energy to the apposed layered tissue structure; and
controlling the applied energy to minimize creation of aberrant conductive paths and enhance fusing of adjacent tissue layers in the layered tissue structure,
wherein the controlling the applied energy includes:
applying power at an initial level of P 0 ,
increasing the power to a higher level of P 1 over a time period of t 1 , and
terminating the power after a time period t 2 if no impedance spike occurs.
2. The method as in claim 1 , further comprising:
reducing or terminating the power if an impedance spike occurs;
reapplying the power at a lower level P 2 over a time period t 3 ; and
terminating the reapplied power if an impedance spike occurs.
3. The method as in claim 1 , wherein the applied energy is controlled to create a weld lesion having a predetermined size in the range from 2 mm 2 to 400 mm 2 .
4. The method as in claim 1 , wherein the applied energy is controlled to create a weld lesion having a predetermined size in the range from 5 mm 2 to 90 mm 2 .
5. The method as in claim 1 , further comprising measuring a tissue response parameter and controlling the applied energy in response to the measured tissue response parameter.
6. The method as in claim 5 , wherein the measured tissue response parameter is selected from the group consisting of tissue temperature, tissue impedance, and tissue moisture.
7. The method as in claim 1 , wherein the controlling further includes varying over time at least one energy parameter selected from the group consisting of power, pulse rate, frequency, rate of increase, rate of decrease, and duration.
8. The method as in claim 7 , wherein the energy parameter is varied at least partly in response to an algorithm.
9. The method as in claim 8 wherein the algorithm is dependent upon a tissue response parameter.