Systems for tissue stimulation and associated methods
Devices, systems, and methods for pacing tissue are disclosed herein. In some embodiments, the devices, systems, and methods position a tip section of a catheter adjacent tissue within an anatomical structure. The tip section is attached to a distal end portion of a catheter shaft, has a maximum radial dimension that is larger than a maximum radial dimension of the catheter shaft, and includes a plurality of electrodes spatially distributed about the tip section. The devices, systems, and methods further select one or more groupings of individual ones of the plurality of electrodes and deliver stimulating energy to or through the adjacent tissue via the selected groupings of electrodes. The stimulating energy is sufficient to activate nerve tissue proximate the tip section but is insufficient to ablate the adjacent tissue. In this manner, devices, systems, and methods disclosed herein can be used to locate nerve tissue proximate the tip section.
1 . A method for stimulating tissue, the method comprising:
positioning a catheter adjacent tissue within an anatomical structure, wherein the catheter includes two or more electrodes disposed at a distal end thereof;
receiving a request for electrical stimulation of the tissue with the catheter; and based, at least in part, upon the request for electrical stimulation-
delivering pulsed electrical energy to a first subset of the two or more electrodes during a first time period, and
delivering pulsed electrical energy to a second subset of the two or more electrodes during a second time period,
wherein—
the second subset is different from the first subset,
the second time period does not overlap with the first time period, and
a time difference between an end of the first time period and a beginning of the second time period is less than a refractory period of the tissue;
detecting capture indicative of activation of the tissue by measuring a displacement of the tissue above a threshold following the delivery of the pulsed electrical energy to the first subset and/or the second subset or by measuring cardiac signals synchronized to the pulsed electrical energy delivered to the first subset and/or the second subset with a consistent delay; and
determining that the tissue is nerve tissue if the capture is detected by measuring the displacement above the threshold or that the tissue is cardiac tissue if the capture is detected by measuring the synchronized cardiac signals with the consistent delay.
2 . The method of claim 1 wherein the time difference is less than 20 milliseconds.
3 . The method of claim 1 , further comprising applying pulsed electrical energy delivered to the first subset and/or the second subset through the tissue during the first time period and/or the second time period.
4 . The method of claim 1 , further comprising applying pulsed electrical energy delivered to the first subset and/or the second subset to or through the tissue during the first time period and/or the second time period, wherein a total duration during which the pulsed electrical energy is applied to or through the tissue over the first and second time periods is less than or equal to 100 milliseconds.
5 . The method of claim 1 , further comprising applying pulsed electrical energy delivered to the first subset and/or the second subset to or through the tissue during the first time period and/or the second time period, wherein a total duration during which the pulsed electrical energy is applied to or through the tissue over the first and second time periods is less than or equal to 50 milliseconds.
6 . The method of claim 1 , further comprising selecting individual ones of the two or more electrodes to include in the first subset and the second subset.
7 . The method of claim 1 wherein the first subset includes at least one electrode configured as a source electrode and at least one other electrode configured as a sink electrode.
8 . The method of claim 1 wherein the first subset and/or the second subset include only individual ones of the two or more electrodes determined to be currently in contact with the tissue based on impedance or electrogram measurements.
9 . The method of claim 1 wherein the first subset of the two or more electrodes and the second subset of the two or more electrodes span a majority of an effective outer surface area of a tip section of the catheter.
10 . The method of claim 1 wherein delivering the pulsed electrical energy to the first subset includes simultaneously delivering the pulsed electrical energy to each electrode of the first subset.
11 . The method of claim 10 wherein simultaneously delivering the pulsed electrical energy includes simultaneously delivering the pulsed electrical energy using two or more current sources.
12 . The method of claim 10 wherein simultaneously delivering the pulsed electrical energy includes simultaneously delivering the pulsed electrical energy to each electrode of the first subset using a respective series impedance, and wherein each series impedance is similar to or larger than an impedance of a respective electrode.
13 . The method of claim 1 wherein the catheter includes at least three electrodes, and wherein the first subset and the second subset each include a pair of electrodes, and wherein each pair of electrodes includes at least one electrode not shared by the other pair.
14 . The method of claim 13 wherein electrodes of at least one of the pairs of electrodes are configured to cooperate to deliver bipolar energy to the tissue.
15 . The method of claim 13 wherein electrodes of at least one pair are configured to cooperate to deliver near-unipolar energy to the tissue.
16 . The method of claim 1 wherein delivering pulsed electrical energy to the first subset and the second subset includes:
using a generator to deliver the pulsed electrical energy to electrodes of the first subset;
using switches, relays, or transistors to electrically couple electrodes in the second subset to the generator after delivering the pulsed electrical energy to the electrodes of the first subset; and
using the generator to deliver the pulsed electrical energy to the electrodes of the second subset.
17 . The method of claim 1 wherein pulsed electrical energy delivered to the first subset and/or the second subset is sufficient to stimulate the tissue but is insufficient to ablate the tissue.
18 . The method of claim 1 wherein pulsed electrical energy delivered to the first subset and/or the second subset is sufficient to stimulate nerve tissue proximate a tip section of the catheter but is insufficient to stimulate cardiac tissue proximate the tip section of the catheter.
19 . The method of claim 1 , further comprising detecting capture indicative of activation of the tissue by measuring a displacement of the tissue above a threshold following the deliveries of the pulsed electrical energy.
20 . The method of claim 19 wherein the tissue is nerve tissue.
21 . The method of claim 19 wherein the tissue is cardiac tissue.
22 . A method for determining tissue type within an anatomical structure, the method comprising:
positioning a catheter adjacent tissue within the anatomical structure, wherein the catheter includes two or more electrodes disposed at a deformable tip section thereof;
receiving a request for electrical stimulation of the tissue with the catheter;
based, at least in part, upon the request for electrical stimulation—
delivering pulsed electrical energy to a first subset of the two or more electrodes during a first time period, and
delivering pulsed electrical energy to a second subset of the two or more electrodes during a second time period;
detecting capture indicative of activation of the tissue by measuring a displacement of the tissue above a threshold following the delivery of the pulsed electrical energy to the first subset and/or the second subset or by measuring cardiac signals synchronized to the pulsed electrical energy delivered to the first subset and/or the second subset with a consistent delay; and
determining that the tissue is nerve tissue if the capture is detected by measuring the displacement above the threshold or that the tissue is cardiac tissue if the capture is detected by measuring the synchronized cardiac signals with the consistent delay,
wherein—
the second subset is different from the first subset,
the second time period does not overlap with the first time period, a time difference between an end of the first time period and a beginning of the second time period is less than a refractory period of the tissue,
a total duration of the first time period and the second time period is less than or equal to 50 milliseconds, and
the pulsed electrical energy is sufficient to stimulate nerve tissue proximate the deformable tip section but is insufficient to stimulate cardiac tissue proximate the deformable tip section.
23 . The method of claim 22 , further comprising:
displaying, on a graphical user interface, a representation of the catheter within the anatomical structure based on the electrical stimulation.