Systems, devices, and methods for focal ablation

An apparatus, comprising:

• a single linear shaft including a linear distal portion positionable near a tissue wall, the linear shaft configured to be deflectable along one or more portions proximal to the linear distal portion to position the linear distal portion near the tissue wall, the linear shaft comprising a flexible shaft portion;
• a plurality of electrodes disposed on the linear distal portion, the plurality of electrodes configured to generate a pulsed electric field with the plurality of electrodes being capable of producing an ablation zone in the tissue wall having a depth that is independent of an orientation of the linear distal portion relative to the tissue wall, the plurality of electrodes including:
• a distal-most set of distal electrodes including a distal tip electrode, having a tip electrode length, disposed at a tip of the linear shaft and an adjacent distal electrode having a distal electrode length different from the tip electrode length and separated from the distal tip electrode by a distal spacing;
• and
• a proximal-most set of proximal electrodes disposed proximal to the distal-most set of distal electrodes, the proximal-most set of proximal electrodes including a proximal spacing separating an adjacent pair of proximal electrodes, the proximal spacing being greater than the distal spacing;
• the flexible shaft portion having a portion length defining an electrode set spacing separating the most distal proximal electrode from the adjacent distal electrode, the most distal proximal electrode of the proximal-most set of proximal electrodes adjacent to the most proximal distal electrode of the distal-most set of distal electrodes,
• wherein the distal spacing and the proximal spacing are less than the electrode set spacing;
• an electromagnetic sensor disposed along the portion length of the flexible shaft portion, such that the electromagnetic sensor is positioned between the set of distal electrodes and the set of proximal electrodes;
• and
• a plurality of leads coupled to the plurality of electrodes, each lead from the plurality of leads configured to deliver a voltage output having an amplitude of at least 700V to the plurality of electrodes (1) without dielectric breakdown of its corresponding insulation and (2) such that the set of distal electrodes are activated with a first polarity and the set of proximal electrodes are activated with a second polarity opposite the first polarity as an anode-cathode pair to collectively generate the pulsed electric field.

A method, comprising:

• positioning an ablation device including a single linear shaft in a cardiac chamber of a heart of a subject such that a linear distal portion of the linear shaft is near a first portion of a tissue wall with the linear shaft set at a first orientation to the first portion of the tissue wall, the linear shaft comprising a flexible shaft portion, the ablation device including a plurality of electrodes disposed on the linear distal portion and an electromagnetic sensor disposed at the flexible shaft portion, the plurality of electrodes including a distal-most set of distal electrodes, including a distal tip electrode having a distal tip length and an adjacent distal electrode having a distal electrode length different from the distal tip electrode length, and a proximal-most set of proximal electrodes, at least one adjacent pair of proximal electrodes of the set of proximal electrodes separated by a first spacing, the most distal proximal electrode of the set of proximal electrodes and the most proximal distal electrode of the set of distal electrodes separated by the flexible shaft portion having a portion length of a second spacing greater than the first spacing and devoid of electrodes of the plurality of electrodes, the most distal proximal electrode of the proximal-most set of proximal electrodes adjacent to the most proximal distal electrode of the distal-most set of distal electrodes, and the set of distal electrodes separated from each other by a distal spacing, the distal spacing less than each of the first spacing and the second spacing;
• and
• generating, using a signal generator, a first pulse waveform having a voltage amplitude of at least about 700 V;
• delivering, while the linear distal portion is set at the first orientation, the first pulse waveform to the plurality of electrodes such that the set of distal electrodes are activated with a first polarity and the set of proximal electrodes are activated with a second polarity opposite the first polarity to collectively generate a pulsed electric field that produces an ablation zone in the first portion of the tissue wall;
• positioning the ablation device in the cardiac chamber such that the linear distal portion is near a second portion of the tissue wall with the linear shaft set at a second orientation different from the first orientation;
• generating, using the signal generator, a second pulse waveform having a voltage amplitude of at least about 700 V;
• and
• delivering, while the linear distal portion is set at the second orientation, the second pulse waveform to the plurality of electrodes such that the set of distal electrodes are activated with the first polarity and the set of proximal electrodes are activated with the second polarity as an anode-cathode pair to collectively generate a pulsed electric field that produces an ablation zone via irreversible electroporation in the second portion of the tissue wall having a depth that is approximately equal to a depth of the ablation zone produced in the first portion of the tissue wall.